Browse Topic: Particulate matter (PM)

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Why It Takes More Energy to Decrease Rotor/Propeller Noise for eVTOL AircraftF-0080-2024-12365/7/2024
In the emerging market of Advanced Air Mobility (AAM), aerospace companies have been designing and prototyping electric and hybrid vehicles to revolutionize travel. These vehicles must have low noise and particulate emissions while also having enough propulsive efficiency to complete the mission. This paper presents the relationship between noise and propulsive efficiency as related to any aircraft equipped with an electric motor and a variable pitch rotor/propeller. The combination of the electric motor with the variable pitch propeller/rotor allows for a decoupled rotational speed and torque generation, meaning that the electric motor can generate the same amount of torque while operating at different rotational speeds. This feature allows the rotor/propeller to hold constant thrust at different combinations of rotational speeds and torque, by adjusting the collective pitch of the blades. Therefore, for a rotor at constant thrust, the minimum noise (from loading and thickness contributions) and minimum power operating points in terms of rotor RPM and collective blade pitch, are not the same thus leading to the fact that it takes increased energy to decrease noise. A MATLAB code is developed to investigate the power and noise relationship by employing several functions to integrate XFOIL and Blade Element Momentum Theory for the rotor performance calculations and WOPWOP for thickness and loading noise analysis.
Roiati, Riccardo, Santacruz, Xavier, Anderson, Richard
Eco-profiling of Bio-epoxies via Life cycle AssessmentSAE-PP-002312/3/2021
Epoxies, synthesized from bisphenol-A (BPA) and epichlorohydrin (ECH), are predominantly used as coatings, adhesives, and as matrix material in fiber-reinforced composites for body-in-white (BiW) applications in the automotive sector. However, given the production of conventional epoxies from non-renewable petroleum resource and toxicity of BPA, several initiatives have been undertaken by researchers to synthesize alternative epoxies from various bio-sources that are free of BPA and exhibit similar mechanical performance. As a result, such bio-sourced epoxies are almost immediately termed as “eco-friendly”, despite the lack of comprehensive evaluation of their ecological performance that takes into account enhanced natural resource usage and associated impacts accompanying such epoxies. Hence, this work aims at addressing this gap by evaluating the environmental impacts of such bio-sourced epoxies via cradle-to-gate life cycle assessment to determine the genuine credentials of their ecofriendliness. Epoxies synthesized from three different bio-sources – namely, bark extractives, lignin, and triglyceride – were chosen, to evaluate their ecological performance. ReCiPe midpoint and endpoint methods were used to evaluate these epoxies in accordance with ISO 14040 and 14044 standards. Among the three bio-epoxies, lignin-based epoxy exhibits poor eco-performance mainly due to the use of large amount of chemicals during extraction of lignin, involving delignification and valorization. On the contrary, bio-epoxy synthesized from triglycerides were found to be eco-friendly compared to other bio-epoxies. All bio-epoxies are observed to contribute significantly to toxicity-related categories, mainly due to higher electricity consumption during both epoxy synthesis and manufacturing processes. Overall, this work sheds light on various avenues for synthesizing truly sustainable epoxies that exhibit mechanical performance comparable to their conventional counterparts.
Anthony, Lindsay, Jackson, Alyssa
Oxygen System and Component CleaningARP1176B (Current)10/19/2020
This SAE Aerospace Recommended Practice (ARP) provides recommended practices for the cleaning of aircraft oxygen equipment, both metallic and non-metallic articles, such as oxygen lines (tubes, hoses, etc.), components (including regulator and valve parts), cylinders, and ground-based equipment that may be used to support aircraft oxygen systems. This document also specifies work area details, methods for selecting suitable cleaning agents, cleaning methods, and test methods for verifying levels of cleanliness. The cleanliness coding scheme specified in this document provides a method for documenting minimum cleanliness level requirements and for identifying compliance.
A-10 Aircraft Oxygen Equipment Committee
Low-Order Prediction of Mineral Dust Sticking Probability in Turboshaft EnginesF-0076-2020-1633810/5/2020
ABSTRACT Rotorcraft operations in arid environments can result in the ingestion of large quantities of dust particles into turboshaft engines, where they can melt and deposit on high pressure turbine nozzle guide vanes. This can result in reduced engine life-span and in worst case scenarios, in-flight engine failure. Predicting the extent and rate at which this damage occurs has proven difficult owing to the wide range of variables relating to the dust cloud, engine and most importantly, the properties of the particulate encountered. Whilst significant work has been carried out to model the particle deposition process for both volcanic ash and coal fly-ash, there is scarce similar work for the different types of mineral dusts rotorcraft encounter. In this contribution, we assess the suitability of two opposing numerical approaches for use in a generalised, reduced-order deposition model of individual mineral particles depositing on a vane. Both models are seen to be heavily reliant upon empirical inputs, be this the thermo-mechanical properties of the particles such as their yield strength, or currently unknown experimentally determined constants. An alternative approach is therefore proposed whereby the particle yield strength is correlated using existing relationships to the Vickers hardness of the grain, a property more amenable to empirical determination. The results obtained represent the current applicability limits of the two models based upon existing empirical data and thus highlight the need for further experimentation relating to both the thermo-mechanical properties and probabilities of adhesion for both individual mineral grains and mineral dust blends.
Ellis, Matthew, Bojdo, Nicholas, Filippone, Antonio, Jones, Merren, Pawley, Alison
Observer for Faulty Perception Correction in Autonomous Vehicles2020-01-06944/14/2020
Operation of an autonomous vehicle (AV) carries risk if it acts on inaccurate information about itself or the environment. The perception system is responsible for interpreting the world and providing the results to the path planning and other decision systems. The perception system performance is a result of the operating state of the sensors, e.g. is a sensor in fault or being adversely affected by the weather or environmental conditions, and approach to sensor measurement interpretation. We propose a trailing horizon switched system observer that minimizes the difference between reference tracking values developed from sensor fusion performed at an upper level and the values from a potentially faulty sensor based upon the convex combination of different sensor observation model outputs; the sensor observations models are associated with different sensor operating errors. The preferred observer target is a stationary landmark so as to remove additional uncertainty resulting from tracking of moving targets. Results for five scenarios show the observer identifies the appropriate sensor model in no more than a few sample intervals.
Omwansa, Mark, Meyer, Rick, Asher, Zachary, Goberville, Nick
Single vs Double Stage Partial Flow Dilution System: Automobile PM Emission Measurement2020-01-03664/14/2020
The US Code of Federal Regulations (CFR) Title 40 Part 1065 and 1066 require gravimetric determination of automobile Particulate Matter (PM) collected onto filter media from the diluted exhaust. PM is traditionally collected under simulated driving conditions in a laboratory from a full flow Constant Volume Sampler (CVS) system, where the total engine exhaust is diluted by HEPA filtered air. This conventional sampling and measurement practice is facing challenges in accurately quantifying PM at the upcoming 2025-2028 CARB LEVIII 1 mg/mi PM emissions standards. On the other hand, sampling a large amount of PM emitted from large size high power engines introduces additional challenges. Applying flow weighting, adjusting the Dilution Ratio (DR) and Filter Face Velocity (FFV) are proposed options to overcome these challenges. The Partial Flow Dilution System (PFDS) technique has been recognized as a viable alternative to the CVS method, to meet the wide range DR and FFV requirements for PM determination from both Light-Duty Vehicles (LDV) and Heavy-Duty Engines (HDE) [4, 5, 6, 7, 8]. In this study, performance of a PFDS for PM measurement with Single Dilution (SD) and Double Dilution (DD) configurations against conventional CVS sampling was investigated. Tests were run on a Cummins heavy-duty 8.9L engine with maximum rated power of 380 HP in an engine test cell. The engine aftertreatment system is comprised of a combined Diesel Oxidation Catalyst (DOC) and Selective Catalyst Reduction (SCR). The reference data, also referred to as historical data, was generated in a test cell using the CVS method. PM measurements were made over the US Non-road Transient Cycle (NRTC) and Ramped Modal Cycle (RMC). The brake-specific particulate matter (BSPM) was calculated using the raw chemical balance utilizing intake airflow measurements and the measurement of gases in the exhaust. The PFDS with single and double tunnel configuration showed good repeatability with a COV of <6% when compared against the historical data which has a COV of <8%. The PFDS with single and double dilution met all the global regulatory requirements with the correlation coefficient of 1.005 and the coefficient of determination (R2) greater than 0.98.
Rahman, Montajir, Rooney, Rick, Nevius, Tim, Otsuki, Yoshinori, Yoshida, Taisuke, Khan, Yusuf, Liew, Chet Mun, Basrur, Chirag
Impact of Post-Injection Parameters on Soot and Hydrocarbon Emissions in a Common-Rail Heavy-Duty Diesel Engine2020-01-03744/14/2020
In this paper, based on a direct injection (DI) diesel engine, soot and exhaust gaseous emissions were measured by a smoke meter and multi-component gas analyzer based on Fourier Transform Infrared (FTIR) spectroscopy under post-injection condition. The post-injection timing changed from 20 crank angle degree (CAD) after top dead center (ATDC) to 120 CAD ATDC, and the post-injection mass was set to either 5mg, 10mg or 15mg, to find a suitable post-injection strategy in a wide assessment range based on diesel oxidation catalyst (DOC) coupled diesel particle filter (DPF) after-treatment technology demands, considering emission reduction and after-treatment gas atmosphere investigation. The results showed that post-injection could achieve NOx emission reduction, up to 14%. Besides, post-injection led to worsening soot emissions, and more hydrocarbon (HC) emissions were detected compared to the condition without the post-injection. With the post-injection, a higher concentration of unsaturated HC emissions (such as C2H2, C2H4, and C3H6), formaldehyde (HCHO), and acetaldehyde (CH3CHO) appeared at late post-injection (after 70°CA). In the measured species, at 80°CA post-injection timing and with 10mg post-injection mass, species with low emissions (<30ppm), included CH4, C2H2, C3H6, and CH3CHO; species with medium emissions (>30ppm and <100ppm), included NO2, HCHO, C2H4, and NC8; species with large emissions (>100ppm), included NO, NOx and non-methane hydrocarbon (NMHC). Furthermore, the peak position of NMHC was the same as C3~C8 HCs and different from C2 HCs within the scope of the experiment, which indicated that, in terms of concentration, the proportion of C2 HCs was not dominant in total NMHC emissions.
Pan, Wang, Wu, Yan, Jing, Yi, Zizeng, Huang
Sub-23 nm Particle Emissions from Gasoline Direct Injection Vehicles and Engines: Sampling and Measure2020-01-03964/14/2020
Nowadays, the regulation regards only the particles larger than 23 nm. The attention is shifting towards the sub-23 nm particles because of their large presence at the exhaust of the modern engines and their negative impact on human health. The main challenge of the regulation of these particles is the definition of a proper procedure for their measure. The nature of the sub-23 nm particles is not well understood, and their measure is strongly affected by the sampling conditions leading to not reliable measure. The aim of this paper is to provide information on the emissions of sub-23 nm particles from GDI vehicles/engines. At the same time, the presence of volatiles, which mainly contribute to the formation of sub-23 nm particles, was evaluated and the effect of sampling conditions was investigated. The analysis was performed on a 1.8L GDI powered vehicle, widely used both in North America and Europe, and a 4-cylinder GDI engine, whose features are similar to those of the vehicle. For both the facilities, vehicle and engine, the Worldwide harmonized Light vehicles Test Cycle (WLTC) was performed. Particle emissions were characterized in terms of number and size by using both commercial systems and prototype systems developed within the European Project SUREAL23. For the vehicle analysis a MEXA 2000 SPCS, for particles larger than 23 nm, and the Induced Current Aerosol Detector (ICAD), developed with in the SUREAL23 European Project, for particles larger than 11 nm, were used. A commercial Engine Exhaust Particle Sizer (EEPS), working in the size range 5.6-560 nm, was used for the sizing and counting of the particles emitted from the GDI engine. For the characterization of the sampling conditions on the measurements were performed on the GDI engine. In this case the sampling was performed by a Particle Measurement Programme (PMP) compliant system, which permits to change the main sampling parameters, i.e. the temperature of the dilution air and of the evaporation chamber, to enhance the nucleation and / or condensation of volatiles. At the decrease of the sampling temperatures, a large concentration of sub-23 nm particles were measured suggesting the presence of large volatile material especially in the first phase of the Cold-start WLTC.
Di Iorio, Silvana, Catapano, Francesco, Sementa, Paolo, Vaglieco, Bianca Maria, Nicol, Giovanna, Sgroi, Mauro Francesco
Laser-Based System Detects Fires Even in Dusty, Harsh EnvironmentsTBMG-357561/1/2020
Researchers have developed a new laser-based system that offers an efficient and low-cost way to detect fires in challenging environments such as industrial facilities or large construction sites. With further development, the system could eventually detect fires that are more than a kilometer away. It could be used in a variety of industries such as waste management facilities, power supply plants, food processing factories, and textile factories.
A Fast, Simple Sampling Method for Characterizing Volatile Organic Compounds Emitted from Medical DevicesTBMG-3551211/1/2019
In 2018, an update on regulations for respiratory medical devices meant that volatile organic compounds (VOCs) emitted from the devices must be addressed. ISO 10993-1 highlights the need for medical device engineers and manufacturers to characterize these chemicals, particularly plastics, because these often emit chemicals such as phthalates and polychlorinated biphenyls, which are thought to be a health concern.1,2
Design of Experiments for Effects and Interactions during Brake Emissions Testing Using High-Fidelity Computational Fluid Dynamics2019-01-21399/15/2019
The investigation and measurement of particle emissions from foundation brakes require the use of a special adaptation of inertia dynamometer test systems. To have proper measurements for particle mass and particle number, the sampling system needs to minimize transport losses and reduce residence times inside the brake enclosure. Existing models and spreadsheets estimate key transport losses (diffusion, turbophoretic, contractions, gravitational, bends, and sampling isokinetics). A significant limitation of such models is that they cannot assess the turbulent flow and associated particle dynamics inside the brake enclosure; which are anticipated to be important. This paper presents a Design of Experiments (DOE) approach using Computational Fluid Dynamics (CFD) to predict the flow within a dynamometer enclosure under relevant operating conditions. The systematic approach allows the quantification of turbulence intensity, mean velocity profiles, and residence times. The factors of the DOE include: a) airflow level, b) brake size, c) rotor style, d) caliper position, e) brake rotation, f) brake rotational speed, and g) fixture style. Numerical simulations are performed using NGA, a high-order, multi-physics large-eddy simulation code. Particles are tracked individually in a Lagrangian manner. The CFD code is coupled with a conservative immersed boundary method to handle complex geometries. The second part of the study investigates the flow behaviour and the associated isokinetics near the sampling plane in the different nozzles that feed the air samples to the various instruments. In order to better understand the transport and fate of solid particles, the model uses a log-normal particle size distribution between 0.55 μm and 20 μm.
Agudelo, Carlos, Vedula, Ravi Teja, Capecelatro, Jesse, Wang, Qingquan
Real Driving Emissions Measurement of Brake Dust Particles2019-01-21389/15/2019
The measurement of brake dust particles is a complex challenge owing to its open system configuration; indeed, the emitted particles are directly spread into the environment. Measurements on the inertia brake dyno feature controllable and reproducible environmental and operational parameters. Although Real Driving Emission (RDE) measurements enable the detection of brake dust particles emitted in real driving conditions (i.e. traffic condition, driving style, air humidity, vehicle components’ wear and ageing, etc.), they are complex and not reproducible due to external, continuously changing parameters (e.g., flow conditions, changing traffic conditions, particulate matter from other sources). The motivation lies in developing a real driving emission sampling system for brake particle emissions, which meets the quality requirements of the measurements, as well as the prevention of particle losses and contamination, thereby supplementing and reviewing laboratory-based procedures. On the basis of knowledge from the computational fluid dynamics and experimental investigations, an advantageous concept of a sampling system for mobile application is presented. The chosen methodological approach shows that the transport efficiency and the uniformity of the number concentration depend on the design, the associated flow conditions and process parameters. In addition, the Particle injection and particle spreading behaviour, influence of disc ventilation and the variable particle properties over the cycle are to be implemented into the evaluation. As a result, an optimized design of a sampling system for mobile applications is derived. Furthermore, the results express the influence of different test environments, test cycles and test setups. The experimental study shows fundamental differences and similarities between laboratory and real-road test environments.
Hesse, David, Augsburg, Klaus
Impact of Ethanol and Aromatic Hydrocarbons on Particulate Emissions from a Gasoline Vehicle2019-24-01609/9/2019
The impact of transport on global and local pollution has resulted in stricter emission limits. More specifically, increasing attention is being paid to exhaust gas particulate emissions in spark ignition engines. The particulate formation is mainly affected by: 1-engine and fuel system characteristics, 2-fuel properties and 3-exhaust aftertreatment system. In order to estimate the influence of fuel characteristics on particulate emissions, several research works have proposed fuel indices that correlate some of the fuel physical and chemical properties with engine particulate emissions. This work investigates the impact of fuel composition on particulate emissions and evaluates the Honda Particulate Matter Index (PMI) proposed by Aikawa et al. and other fuel indices in terms of agreement with vehicle test bed results for a passenger car. Vehicle tests were performed on New European Driving Cycle (NEDC) and Worldwide Harmonized Light Vehicles Test Cycle (WLTC) by using an E10 Euro VI reference fuel and five different fuel blends with 10% to 20% of ethanol and 23% to 35% of aromatic hydrocarbons content by volume. The effect of aromatic hydrocarbons composition on particulate emissions is also investigated by considering the same amount of global aromatic hydrocarbons but different aromatic composition: heavy aromatic hydrocarbons (C11)- and light aromatic hydrocarbons (C7-C9). Results illustrate a good correlation between particulate emissions and aromatic hydrocarbons content but little or no sensitivity of particulate emissions to ethanol content in the fuels. The comparison of the fuel particulate indices and vehicle results revealed different sensitivities but good overall agreement. It was also found that particulate emissions present a high sensitivity to heavy aromatic hydrocarbons content. These results highlight the importance of fuel quality and more specifically the role of heavy aromatic hydrocarbons on particulate emissions.
Tahtouh, Toni, Ben Amara, Arij, Anselmi, Patricia, Starck, Laurie
Numerical Study of Pore Size and Distribution Effects on Gasoline Particulate Filter Performance03-12-05-00328/22/2019
Abstract The improved brake thermal efficiency of Gasoline Direct Injection (GDI) engines is accompanied by a significant increase in Particulate Matter (PM) mass and higher Particulate Number (PN) emissions as compared to (multi)Port Fuel Injected (PFI) engines. Gasoline particulate filters (GPFs) with high filtration efficiency and low backpressure will be required to meet the future, stringent PM/PN regulations. A two-dimensional (2D) CFD study was performed to determine the effects of pore size and distribution on the interdependent performance parameters of filtration efficiency and backpressure for clean GPFs. Simulation results show an on linear change infiltration efficiency as the pore size distribution tightens and determine a recommended distribution range, controlling the quantity of small-sized pores. Pore size distributions beyond this recommended range can cause a filtration performance loss or intolerable backpressure penalty for the GPF. In addition, a recent collaborative publication from our group has demonstrated our ability to create a hierarchical porous filter, with variable pore size in each layer. Knowing that filtration efficiency and pressure drop increase as the average pore size decreases offers inspiration for a novel wall design with small pores comprising the top 40% of the wall layers and larger pores on bottom 60%. The model predicts that such a wall would result in an 8% increase in filtration efficiency.
Yang, Pengze, Strzelec, Andrea
Radar Detection of High Concentrations of Ice Particles - Methodology and Preliminary Flight Test Results2019-01-20286/10/2019
High Ice Water Content (HIWC) has been identified as a primary causal factor in numerous engine events over the past two decades. Previous attempts to develop a remote detection process utilizing modern commercial radars have failed to produce reliable results. This paper discusses the reasons for previous failures and describes a new technique that has shown very encouraging accuracy and range performance without the need for any modifications to industry’s current radar design(s). The performance of this new process was evaluated during the joint NASA/FAA HIWC RADAR II Flight Campaign in August of 2018. Results from that evaluation are discussed, along with the potential for commercial application, and development of minimum operational performance standards for future radar products.
Harrah, Steven, Strickland, Justin, Hunt, Patricia, Proctor, Fred, Switzer, George, Ratvasky, Thomas, Strapp, J. Walter, Lilie, Lyle, Dumont, Christopher
Summary of the High Ice Water Content (HIWC) RADAR Flight Campaigns2019-01-20276/10/2019
NASA and the FAA conducted two flight campaigns to quantify onboard weather radar measurements with in-situ measurements of high concentrations of ice crystals found in deep convective storms. The ultimate goal of this research was to improve the understanding of high ice water content (HIWC) and develop onboard weather radar processing techniques to detect regions of HIWC ahead of an aircraft to enable tactical avoidance of the potentially hazardous conditions. Both HIWC RADAR campaigns utilized the NASA DC-8 Airborne Science Laboratory equipped with a Honeywell RDR-4000 weather radar and in-situ microphysical instruments to characterize the ice crystal clouds. The purpose of this paper is to summarize how these campaigns were conducted and highlight key results. The first campaign was conducted in August 2015 with a base of operations in Ft. Lauderdale, Florida. Ten research flights were made into deep convective systems that included Mesoscale Convective Systems (MCS) near the Gulf of Mexico and Atlantic Ocean, and Tropical Storms Danny and Erika near the Caribbean Sea. The radar and in-situ measurements from these ten flights were analyzed and correlations defined. Key results included 1) derived relationships between radar reflectivity factor (RRF), Ice Water Content (IWC), and ice particle size distributions, 2) characterization of HIWC conditions at the -50°C and other flight levels, and 3) verification of pilot observations, such as low radar reflectivity factor and pitot and total air temperature (TAT) anomalies. This data set also enabled new pilot radar HIWC detection algorithms to be developed and tested. A second campaign was conducted in August 2018 to test proposed HIWC radar detection algorithms within a new set of storm systems. Seven research flights were conducted from bases of operations in Ft. Lauderdale, Florida; Palmdale, California; and Kona, Hawaii. Flights were made into convective systems over the Gulf of Mexico and into an eastern-Pacific tropical system that developed into Hurricane Lane. Using a new, NASA-developed radar processing technique called “Swerling”, regions of HIWC were identified, and estimates of IWC were produced, at distances up to 60 Nm ahead of the NASA DC-8. Subsequently, the DC-8 flew through these regions to acquire the in-situ measurements to verify the radar-based IWC estimates.
Ratvasky, Thomas, Harrah, Steven, Strapp, J. Walter, Lilie, Lyle, Proctor, Fred, Strickland, Justin, Hunt, Patricia, Bedka, Kristopher, Diskin, Glenn, Nowak, John B., Bui, T. P., Bansemer, Aaron, Dumont, Christopher
Wind Tunnel Measurements of Simulated Glaciated Cloud Conditions to Evaluate Newly Developed 2D Imaging Probes2019-01-19816/10/2019
Instrumentation that has been used for characterization of mixed-phase and glaciated conditions in the past, like the OAP probes, are subject to errors caused by variations in diffraction on the images away from the object plane and by the discrete nature of their particle detection and sizing. Correction methods are necessary to consider their measurements adequate for high ice water content (IWC) environments judged to represent a significant safety hazard to propellers and turbofan engine operability and performance. For this reason, within the frame of EU FP7 HAIC project, instrumentation characterization and validation is considered a major element need for successful execution of flight tests campaigns. Clearly, instrumentation must be sufficiently reliable to assess the reproducibility of artificial clouds with high ice water content generated in icing tunnels. Instruments are required to measure these conditions with a sufficient level of accuracy for the purposes of the testing. Currently, there is an anticipated basic uncertainty of a factor of 2-5 when measuring clouds in-situ. This may be worse for thunderstorm core regions, because of the poorly measured ice particle sizes below 100 μm when using legacy instruments. Measurements below 100 μm are especially difficult for ice particles. In order to mitigate this measurement limitation, an innovative approach for imaging droplets and ice crystals was considered in this work. This method is based on Artium Technologies Inc. High Speed Imaging (HSI) instrument. The method utilizes a unique multi-beam illumination approach to control the depth of field, minimize out-of-focus image noise effects, and limit obscuration of particles in the sample volume produced by out-of-focus particles in the optical path. Rather than utilizing a linear array to acquire the images, a modern CMOS two-dimensional array imaging system is used. The lasers used for producing bright field shadow images are pulsed synchronously and have pulse duration of as little as 12.5 ns to “freeze” the particle motion. The response of the HSI will be reviewed on the basis of comparison with SPEC 2D-S by means of wind tunnel measurements for glaciated cloud conditions.
Esposito, Biagio M., Bachalo, William D., Leroy, Delphine, Schwarzenboeck, Alfons, Jurkat, Tina, Voigt, Christiane, Bansmer, Stephan
A Three-Layer Thermodynamic Model for Ice Crystal Accretion on Warm Surfaces: EMM-C2019-01-19636/10/2019
Ingestion of high altitude atmospheric ice particles can be hazardous to gas turbine engines in flight. Ice accretion may occur in the core compression system, leading to blockage of the core gas path, blade damage and/or flameout. Numerous engine powerloss events since 1990 have been attributed to this mechanism. An expansion in engine certification requirements to incorporate ice crystal conditions has spurred efforts to develop analytical models for phenomenon, as a method of demonstrating safe operation. A necessary component of a complete analytical icing model is a thermodynamic accretion model. Continuity and energy balances are performed using the local flow conditions and the mass fluxes of ice and water that are incident on a surface to predict the accretion growth rate. In this paper, a new thermodynamic model for ice crystal accretion is developed through adaptation of the Extended Messinger Model (EMM) from supercooled water conditions to mixed phase conditions (ice crystal and supercooled water). A novel three-layer accretion structure is proposed and the underlying equations described. The EMM improves upon the original model for airframe icing, the Messinger Model, by permitting a linear temperature gradient through the ice and water layers. This in turn allows prediction of the time over which water exists in isolation on an initially warm surface, before an ice layer forms. This is of particular interest to engine icing, as surfaces may initially be significantly above freezing temperature, before cooling on exposure to ice particles. The method is solved in a multi-step approach, where the overall exposure time is divided into discrete windows, and the calculation performed over each window. This allows the local flow conditions to be updated between windows, permitting the incorporation of a reducing flow enthalpy due to particle evaporation, as well as transient engine operation. Model results are then compared to experimental results. Comparisons are made to solutions generated using the standard Messinger Model.
Bucknell, Alexander, McGilvray, Matthew, Gillespie, David, Jones, Geoffrey, Collier, Benjamin
Event-Driven Simulation of Particle-Particle and Particle-Surface Collisions in Ice Crystal Icing2019-01-20146/10/2019
This paper describes an event-driven simulation tool for predicting particle-particle and particle-surface interactions in ice crystal icing (ICI). A new accretion model which is much less empirical than existing models for predicting ICI accretion is also described. Unlike previous models, the new “gouge/bounce model” (GBM) differentiates between (erosion) losses resulting from particle bounce and those resulting from particle gouging. A bounce threshold based on the tangential Stokes number is used to calculate most of the bounce loss. The GBM also predicts ejecta velocities and directions, at least approximately, which is important because most of the mixed-phase mass flux impacting a surface actually bounces off or erodes existing material in ICI, thereby increasing the mass flux downstream. The event-driven simulation tool, denoted COLLIDE, has been applied to two test cases in which accretion growth appeared to be affected by TWC in a manner beyond that which would be expected from the accumulation parameters. An existing correlation-based accretion model (CBM), modified to predict erosion dependence on particle diameter, is also implemented and applied to the test cases. COLLIDE predicted the observed accretion dependence on TWC in a least a qualitative fashion for the majority of model/test case permutations, supporting the hypothesis that collisions between backscattered and incident particles reduces erosion and thereby increases sticking efficiency as observed in experiments with larger particles. The predictions suggest scattering of incident particles by impacts with ejecta is the dominant mechanism responsible for the flux interference effect, not particle size reduction due to particle-particle collisions.
Currie, Thomas Charles
Motivation, Development and Verification of a Rapid 3D Lagrangian Impingement Code - Trajectory and Catch 3D+ (TAC3D+)2019-01-20116/10/2019
This paper details the motivation, development and validation of a rapid 3D Lagrangian impingement code, Trajectory and Catch 3D+ (TAC3D+). AeroTex’s motivation to develop a 3D Lagrangian method was primarily driven by the inherent mesh dependent dissipation effect found in their 3D Eulerian Water Catch code (EWC) [1]. Studies performed by AeroTex have shown that for geometries where there are aft impingement regions that are partly shadowed by a more forward impingement region, the level of water flux dissipation can be significant, particularly if the mesh is coarse and the impingement region is far aft. Examples of issues where this may be a particular issue would be impingement on a centerline aft mounted engine or the calculation of impingement on the wing root/belly fairing. The code has been developed around a modified version of the OpenFOAM Lagrangian solver. The analysis process consists of three main phases; a coarse droplet trajectory calculation to identify the region of interest, a refined trajectory calculation that is sufficiently fine to calculate local water collection and a surface water collection efficiency calculation including mass loss due to splash and bounce associated with large droplets where applicable. The code allows the user to utilize multiple cluster queues to spread the job across multiple compute nodes to deliver the solution rapidly. The TAC3D+ code has been verified against a selection of 2D and 3D cases including some incorporating splash and bounce effects. The code is undergoing further development to incorporate the physics associated with ice crystals and the re-impingement of splashed particles. In addition, AeroTex are exploring methods to make the code even more efficient by maximizing time steps, utilizing different integration schemes and potential for the use of GPUs.
Roberts, Ian
Predicted Ice Shape Formations on a Boundary Layer Ingesting Engine Inlet2019-01-20256/10/2019
Computational ice shapes were generated on the boundary layer ingesting engine nacelle of the D8 Double Bubble aircraft. The computations were generated using LEWICE3D, a well-known CFD icing post processor. A 50-bin global drop diameter discretization was used to capture the collection efficiency due to the direct impingement of water onto the engine nacelle. These discrete results were superposed in a weighted fashion to generate six drop size distributions that span the Appendix C and O regimes. Due to the presence of upstream geometries, i.e. the fuselage nose, the trajectories of the water drops are highly complex. Since the ice shapes are significantly correlated with the collection efficiency, the upstream fuselage nose has a significant impact on the ice accretion on the engine nacelle. These complex trajectories are caused by the ballistic nature of the particles and are thus exacerbated as particle size increases. Shadowzones are generated on the engine nacelle, and due to the curvature of the nose of the aircraft the shadowzone boundary moves from lower inboard to upper outboard as particle size increases. The largest particle impinging one the engine nacelle from the 50-bin discretization was the 47 μm drop diameter. As a result, the MVD greater than 40 μm Appendix O conditions were characterized by extremely low collection efficiency on the engine nacelle for these direct impingement simulations.
Porter, Christopher
Validation and Instrumentation of a Small Modular Multi-Stage Axial Compressor for Ice Crystal Icing Research2019-01-19406/10/2019
The National Research Council of Canada (NRC) has undergone the development of a Small Axial Compressor Rig for modelling altitude ice accretion in aircraft engines. The rig consists of two axial compressor stages measuring approximately 150mm in diameter, an extension duct to allow residence time for partial melting of ice crystals and a test piece. The axial compressor stages are intended to provide realistic engine conditioning such as fracture, pressure rise, temperature rise and centrifuging of glaciated ice crystals entering the rig. The rig was designed for use in altitude icing wind tunnels such as the NRC’s altitude icing wind tunnel (AIWT), research altitude test facility (RATFac.), and those of other organization such as NASA Glenn and Technical University of Braunshweig. Previous development work [1] provided partial validation of the aerodynamic performance of just the first compressor stage at 90% power. Recent development work has concluded the aerodynamic validation of both the first and the second stages and performance was found to be satisfactory for purpose. A prediction of the ice accretion behavior of the rig based on validated performance is provided. Details of the instrumentation scheme including measurement technique for the radial distribution of ice crystal downstream of the compressor stages, and measurement of particle sizes before and after each stage are also presented.
Neuteboom, Martin, Chalmers, Jennifer, Currie, Thomas
Icing Test and Measurement Capabilities of the NRC’s Gas Turbine Laboratory2019-01-19436/10/2019
The National Research Council’s Gas Turbine Laboratory provides industry leading icing facilities that allow manufacturers to develop, validate and certify new products for flight in adverse conditions. This paper shows how NRC measurement techniques are used across the facilities, and presents a literature-review of recently developed capabilities. The overview includes new details on some facilities, and future capabilities that are in development or planned for the near future. Methods developed at the NRC for characterizing inclement conditions are discussed and include the Isokinetic Probe, Particle Shadow Velocimetry, the Particle Detection Probe, and a size-binned real-time thermodynamic evaporation model. These are used to deliver accurate icing water content in facilities like the sea-level ice crystal generator, the Rotating Icing Rig, the Research Altitude Testing Facility, and liquid water test facilities in Ottawa and in Thompson, Manitoba at the Global Aerospace Centre for Icing and Environmental Research (GLACIER).
Chalmers, Jennifer, Davison, Craig, MacLeod, James, Neuteboom, Martin, Fuleki, Dan
An Experimental Investigation of a Wind-Driven Water Droplet over the Slippery Liquid Infused Porous Surface2019-01-19516/10/2019
The promising anti-icing performance of the slippery liquid infused porous surface (SLIPS) has been recently demonstrated for various engineering applications. The runback icing for aircraft and wind turbines could be effectively mitigated considering the timely removal of water droplet by the wind shearing force due to the low adhesion on the SLIPS. In this study, the flow field both inside and around the wind-driven droplet over the SLIPS was experimentally investigated by using Particle Image Velocimetry (PIV) technique. Previous studies majorly focus on the internal flow pattern before the droplet incipient motion. In this study, the flow field inside a moving droplet was firstly investigated. As a result of the low surface adhesion of the SLIPS, droplet oscillations were eliminated and the droplet internal flow field could be corrected from the optical distortion. Besides the discussion on the wind speed, the droplet viscosity was also studied by varying the water concentration of the glycerin-water solution. It was found that the internal circulation was highly related with the droplet viscosity. The inner circulations within the water droplet would be reduced, or eliminated, when the droplet viscosity was increased, which would change the droplet motion from sliding into rolling. It was suggested that the internal flow should be considered when theoretically modeling the wind-driven droplet movement over the SLIPS. This study could provide experimental evidence for a broader application of the SLIPS in the icing-related industrial world.
Ma, Liqun, Hu, Hui
Simulation of Ice Particle Breakup and Ingestion into the Honeywell Uncertified Research Engine (HURE)2019-01-19656/10/2019
Numerical solutions have been generated which simulate flow inside an aircraft engine flying at altitude through an ice crystal cloud. The geometry used for this study is the Honeywell Uncertified Research Engine (HURE) which was recently tested in the NASA Propulsion Systems Laboratory (PSL) in January 2018. The simulations were carried out at predicted operating points with a potential risk of ice accretion. The extent of the simulation is from upstream of the engine inlet to downstream past the strut in the core and bypass. The flow solution is produced using GlennHT, a NASA in-house code. A mixing plane approximation is used upstream and downstream of the fan. The use of the mixing plane allows for steady state solutions in the relative frame. The flow solution is then passed on to LEWICE3D for particle trajectory, impact and breakup prediction. The LEWICE3D code also uses a mixing plane approximation at the boundaries upstream and downstream of the fan. A distribution of particle sizes is introduced upstream, based on the distribution measured during the test. Predicted collection efficiency and melt ratio results are presented on various surfaces. The redistribution of particle sizes and mass are also investigated at various axial locations and compared to particle measurements in the bypass.
Rigby, David L., Wright, William, Flegel, Ashlie, King, Michael
ICICLE: A Model for Glaciated & Mixed Phase Icing for Application to Aircraft Engines2019-01-19696/10/2019
High altitude ice crystals can pose a threat to aircraft engine compression and combustion systems. Cases of engine damage, surge and rollback have been recorded in recent years, believed due to ice crystals partially melting and accreting on static surfaces (stators, endwalls and ducting). The increased awareness and understanding of this phenomenon has resulted in the extension of icing certification requirements to include glaciated and mixed phase conditions. Developing semi-empirical models is a cost effective way of enabling certification, and providing simple design rules for next generation engines. A comprehensive ice crystal icing model is presented in this paper, the Ice Crystal Icing ComputationaL Environment (ICICLE). It is modular in design, comprising a baseline code consisting of an axisymmetric or 2D planar flowfield solution, Lagrangian particle tracking, air-particle heat transfer and phase change, and surface interactions (bouncing, fragmentation, sticking). In addition, an efficient particle tracking method has been developed into the code, which employs the representative particle size distribution at each injection location and a deterministic particle sticking method by using an in-situ particle based scaling factor without aborting the particle trajectories. Various time integration algorithms, including implicit and explicit Euler and Runge-Kutta methods, are discussed and the effect on an acceptable timestep investigated. The model then improves on those available in the literature in three ways: firstly, an adaptation of the Extended Messinger Model (EMM) to mixed phase conditions is incorporated, improving the fidelity of the ice accretion prediction compared with the classical Messinger model. Secondly, an experimentally-derived model for sticking efficiency improves the accuracy of the continuity equation in the EMM; thirdly a simple model for integrating two-way coupling of mass and energy is proposed.
Bucknell, Alexander, McGilvray, Matthew, Gillespie, David, Yang, Xin, Jones, Geoffrey, Collier, Benjamin
Two-Way Flow Coupling in Ice Crystal Icing Simulation2019-01-19666/10/2019
Numerous turbofan power-loss events have occurred in high altitude locations in the presence of ice crystals. It is theorized that ice crystals enter the engine core, partially melt in the compressor and then accrete onto stator blade surfaces. This may lead to engine rollback, or shed induced blade damage, surge and/or flameout. The first generation of ice crystal icing predictive models use a single flow field where there is no accretion to calculate particle trajectories and accretion growth rates. Recent work completed at the University of Oxford has created an algorithm to automatically detect the edge of accretion from experimental video data. Using these accretion profiles, numerical simulations were carried out at discrete points in time using a manual meshing process. That work showed that flow field changes caused by a changing accretion profile had significant effects on the collection efficiency of impinging particles, ultimately affecting the mass of accreted ice and its shape. This paper discusses the development of the ICICLE numerical ice crystal icing code to include a fully automated two-way coupling between the accretion profile and flow field solution, to account for these effects. The numerical strategy; geometry redefinition, mesh update and flow field solution are discussed, followed by a comparison to experimental ice accretion of a simple 2D geometry and model predictions with and without flow field updating. The results showed that significant changes in leading edge accretion profiles were numerically predicted when the only the geometry was updated. Further changes then occurred when the flowfield was also updated.
Connolly, Jonathan Paul, McGilvray, Matthew, Gillespie, David, Bucknell, Alex, Parker, Liam, Jones, Geoffrey, Collier, Benjamin
NRC Particle Detection Probe: Results and Analysis from Ground and Flight Tests2019-01-19336/10/2019
High altitude ice crystals are causing in-service events in excess of one per month for commercial aircraft. The effects include air data probes malfunctioning (pitot pressure and total air temperature in particular), and uncommanded engine power loss or flameout events. The National Research Council Canada (NRC) has developed a particle detection probe (PDP) that mounts on the fuselage of aircraft to sense and quantify the ice crystals in the environment. The probe is low-power and non-intrusive. This paper presents the results of ground and flight testing of this probe. Results are presented for ground testing in a sea level ice crystal wind tunnel and an altitude icing tunnel capable of generating both ice crystal and super-cooled liquid. The PDP was operated on several flight campaigns and the results of two will be presented. The first was on board a NRC Convair 580 aircraft in French Guiana (FG) and the second was on an Airbus operated A340 research aircraft in Darwin and Reunion Island. The flight campaigns included fully glaciated, mixed phase and fully liquid conditions. Results will be presented and compared across operating conditions at typical altitudes for commercial aircraft. Aircraft installation effects on the PDP measurements will also be examined. NRC has developed preliminary algorithms that provide reliable detection of ice crystal environment along with the ability to estimate the concentration of ice particles being encountered by the aircraft. However, the algorithms themselves are considered proprietary and therefore will not be discussed.
Davison, Craig, Chalmers, Jennifer, Fuleki, Dan
Ice-Crystal Icing Accretion Studies at the NASA Propulsion Systems Laboratory2019-01-19216/10/2019
This paper describes an ice-crystal icing experiment conducted at the NASA Propulsion System Laboratory during June 2018. This test produced ice shape data on an airfoil for different test conditions similar to those inside the compressor region of a turbo-fan jet engine. Mixed-phase icing conditions were generated by partially freezing out a water spray using the relative humidity of flow as the primary parameter to control freeze-out. The paper presents the ice shape data and associated conditions which include pressure, velocity, temperature, humidity, total water content, melt ratio, and particle size distribution. The test featured a new instrument traversing system which allowed surveys of the flow and cloud. The purpose of this work was to provide experimental ice shape data and associated conditions to help develop and validate ice-crystal icing accretion models. The results support previous experimental observations of a minimum melt-ratio threshold for accretion to occur as well as the existence of a plateau region where the icing severity is high for a range of melt ratios. However, a maximum limit for melt ratio, which is suggested in the ice crystal icing literature, was not observed perhaps complicated by the potential for some supercooling of the water at these conditions.
Struk, Peter M., Agui, Juan, Ratvasky, Thomas, King, Michael, Bartkus, Tadas, Tsao, Jen-Ching
A Continuing Investigation of Diurnal and Location Trends in an Ice Crystal Icing Engine Event Database2019-01-19646/10/2019
Due to ongoing efforts by the aviation industry, much has been learned over the last several years regarding jet engine power loss and compressor damage events caused by the ingestion of high concentrations of ice crystal particles into the core flow path. Boeing has created and maintained a database of such ice crystal icing (ICI) events to aid in analysis and further study of this phenomenon. This article provides a general update on statistics derived from the Boeing event database, and provides more details on specific event clusters of interest. A series of three flight campaigns have, over the past five years, collected in-situ data in deep convective clouds that will be used for the assessment of the new FAA CFR Part 33 ice crystal environmental envelope Appendix D, and the equivalent EASA CS-25 Appendix P. The most recent Boeing engine event study in 2015 focused on oceanic cloud systems that caused events in Southeast Asia, a region expected to have similar cloud properties as the first flight campaign in Darwin, Australia. The current study will examine ICI engine events over South America and Africa, which are caused by large deep convective continental clouds of the type that were not the main focus of the three Appendix D/P flight campaigns. Continental event clouds are compared to the previously studied oceanic event clouds, in order to ascertain whether any systematic differences exist that should be considered when assessing the representativeness of the flight campaign datasets. The results may also be useful to those developing nowcasting algorithms identifying high ice concentration regions using satellite measurements.
Bravin, Melissa, Strapp, J. Walter
Uncertainty of the Ice Particles Median Mass Diameters Retrieved from the HAIC-HIWC Dataset: A Study of the Influence of the Mass Retrieval Method2019-01-19836/10/2019
In response to the ice crystal icing hazard identified twenty years ago, aviation industry, regulation authorities, and research centers joined forces into the HAIC-HIWC international collaboration launched in 2012. Two flight campaigns were conducted in the high ice water content areas of tropical mesoscale convective systems in order to characterize this environment conducive to ice crystal icing. Statistics on cloud microphysical properties, such as Ice Water Content (IWC) or Mass Median Diameter (MMD), derived from the dataset of in situ measurements are now being used to support icing certification rulemaking and anti-icing systems design (engine and air data probe) activities. This technical paper focuses on methodological aspects of the derivation of MMD. MMD are estimated from PSD and IWC using a multistep process in which the mass retrieval method is a critical step. Complementary to previous studies reporting on MMD values calculated from the HAIC-HIWC dataset, this paper deals with the uncertainty in MMD by comparing two different approaches for the retrieval of the mass-size (m-D) relationship. The analysis encompasses the data collected in the high IWC areas (IWC > 1g.m-3) sampled during the two HAIC-HIWC field campaigns. MMD series are computed using three different mass-size relationships and statistical values are compared. Overall, MMD values are in good agreement, at least for two methods although they imply quite different assumptions. On the variability in MMD values at a given temperature level, results show that MMD may vary significantly from one flight to the other, even though MMD series produced with the different mass retrieval methods follow a similar pattern. A strong temperature dependence is observed regardless the assumption on the m-D relationship, making MMD to increase by more than a factor of 2 as temperature increases from -50°C to -10°C. Finally, the influence on calculated MMD of two different definitions for particle size (Deq and Dmax) is demonstrated. Generally, MMD computed with Dmax are a few percent larger as compared to MMD calculated from Deq definition, supporting the conclusions from previous studies.
Coutris, Pierre, Schwarzenboeck, Alfons, Leroy, Delphine, Grandin, Alice, Dezitter, Fabien, Strapp, J. Walter
Development and Experimental Validation of a Control Oriented Model of a Catalytic DPF2019-01-09854/2/2019
1 The wall-flow Diesel Particulate Filter (DPF) is currently the most common after-treatment system used to meet the particulate emissions regulations for automotive engines. Today’s technology shows the best balance between filtration efficiency and back-pressure in the engine exhaust pipe. During the accumulation phase the pressure drop across the filter increases, thus requiring periodic regeneration of the DPF through after and post fuel injection strategies. This paper deals with the development of a control oriented model of a catalytic silicon carbide (SiC) wall flow DPFs with CuFe2O4 loading for automotive Diesel engines. The model is intended to be used for the real-time management of the regeneration process, depending on back-pressure and thermal state. In order to ensure suitable computational demand and to realize emissions control and fuel economy objectives, the 0-D model has been developed with the aim of investigating the essential behavior of the system, such as the chemical kinetic of filtered soot oxidation, the thermal and backpressure dynamics along accumulation and regeneration processes. Parameters identification and model validation have been performed vs. experimental data measured on the engine test bench at the exhaust of a EURO 5 light-duty Diesel engine, in different operating conditions. During the accumulation process, engine speed, load and rail pressure are controlled to ensure several levels of trapped soot; on the other hand, the injections pattern, which directly affects the DPF inlet temperature, is handled during regeneration tests. The results show that the model simulates the thermal dynamics and the pressure drop across the filter with good accuracy.
D'Aniello, Federica, Rossomando, Bruno, Arsie, Ivan, Pianese, Cesare
Numerical Modeling Study of Detailed Gas Diffusivity into Catalyst Washcoat for Lean NOx Catalyst2019-01-09934/2/2019
To evaluate the relationship between the exhaust gas purification performance and the catalyst pore properties related to gas diffusion, an elementary reaction model was combined with gas diffusion into catalyst pores, referred to as the pseudo-2D gas diffusion/reaction model. It was constructed for Pt/Al2O3 + CeO2 catalyst as lean NOx catalyst. The gas diffusion was described as macro pore diffusion between the catalyst particles and meso pore diffusion within the particle. The kinetic model was composed of 26 reactions of NO/CO/O2 chemistry including 17 Pt/Al2O3 catalyst reactions and 9 CeO2 reactions. Arrhenius parameters were optimized using activity measurement results from various catalysts with various pore properties, meso pore volume and diameter, macro pore volume and diameter, particle size, and washcoat thickness. Good agreement was achieved between the measured and calculated values. Moreover, as compared to the performance of other catalysts which was not used for reaction model calibration, the simulated results were in good agreement with this experimental data. Using the calibrated reaction model combined with detailed gas diffusion model, a sensitivity analysis for NOx concentration was performed to identify key diffusion parameters of the lean NOx catalyst. In summary, parameters with the highest sensitivity were catalyst particle size, washcoat thickness, CeO2 meso pore volume, and diameter. Also, catalyst macro pore volume and diameter showed no dependence. Consequently, to increase the NOx purification performance, the meso pore parameters and washcoat thickness should be increased, particle size should be decreased. With these changes, the gaseous NOx will easily move to the catalyst surface and into the active site of meso pore, resulting in better performance.
Yamamoto, Osami, Matsuo, Yuichi, Tosa, Shinichi, Okayama, Tatsuya, Zhang, Zhiwei, Tolsma, John
Experimental and Computational Study of DOC on CSF for Heavy Duty Diesel Applications2019-01-05864/2/2019
For diesel exhaust aftertreatment applications with space limitations, as well as to move the selective catalytic reduction system (SCR) to a warmer location closer to the engine, DOC on CSF technology can be used. This technology combines the diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF) functionalities in one component, thereby enabling volume reduction. DOC on CSF maintains the abatement of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM), and the oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) for passive soot oxidation and fast SCR reaction of NOx on a downstream SCR catalyst. In this study, the performance of DOC on CSF was compared to a DOC + bare diesel particulate filter (DPF) and a DOC + CSF system, to understand the performance benefits and challenges. All the components were optimized individually for their respective functions. The DOC on CSF was optimized for NO oxidation and passive soot oxidation performance. Experimental data and simulations were used to understand the underlying mechanisms in the DOC on CSF technology. Steady state HC oxidation under active regeneration conditions showed a benefit for DOC on CSF compared to the DOC + DPF system. The soot oxidation characteristics of the DOC on CSF were evaluated in comparison to a DPF or CSF downstream of a DOC under passive and active soot oxidation conditions. In addition, the contribution of NO2 generated within the filter on the soot oxidation was assessed. The passive soot oxidation characteristics of a DOC on CSF were found to be similar, or better, compared to DOC + DPF and DOC + CSF under certain conditions. The active regeneration efficiency was lower for the DOC on CSF due to the gradual increase in temperature along the length of the part during fuel injection. This work demonstrates the differences between the DOC on CSF and DOC + bare/coated DPF systems, thus enabling a better understanding of the performance of DOC on CSF to current applications.
Sethuraman, Sharan, Sitamraju, Siddarth, Lopez-De Jesus, Yaritza M, Markatou, Penelope
Ash Transport and Deposition, Cake Formation and Segregation-A Modeling Study on the Impact of Ash on Particulate Filter Performance2019-01-09884/2/2019
Non-combustible particles, commonly summarized as ash, influence the lifetime performance of wall flow filters. This study aims to investigate this influence by means of simulation. An existing transient 1D+1D wall flow filter model is extended by dedicated transport balances for soot and ash (1), by a discrete cake model describing changing soot and ash compositions over the cake height (2), by a phenomenological cake filtration model (3), by dedicated cake property models (4) and by a phenomenological model capturing the radial mobility of solids within the cake (5). Results of three different types of simulations are shown. First, the various sub-models are assessed in isolated simulation configurations. The combination of these shall serve as theoretical model validation. Second, isolated loading and passive regeneration simulations are performed. This aims to identify the impact of different filtration and cake migration constants on soot and ash segregation (i.e. ash accumulation) and on soot conversion performance. Third, the impact of ash during a combined loading and passive regeneration cycle is investigated. This aims to identify the impact of ash on the formation of a soot balance point.
Wurzenberger, Johann C., Kutschi, Susanne, Nikodem, Astrid
Sensitivity Study on Thermal and Soot Oxidation Dynamics of Gasoline Particulate Filters2019-01-09904/2/2019
Gasoline particulate filters (GPFs) are devices used to filter soot emitted by gasoline direct injection (GDI) engines. A numerical model for a ceria-coated GPF presented in a previous paper by H. Arunachalam et al. in 2017 was developed to predict internal temperature and soot amount combusted during regeneration events. Being that both the internal temperature and the accumulated soot cannot be directly measured during real-time operation and owing to their critical importance for GPF health monitoring as well as regeneration scheduling, the above model turns out to be a valuable tool for OBD applications. In this paper, we first conduct a stochastic analysis to understand the relation between the model parameters and the initial value of the ceria (IV) oxide volume fraction, as a deterministic value for such a state is not known. A particle swarm optimization (PSO) algorithm was employed to define what type of relationship the model parameters were with respect to the initial state of the ceria (IV) oxide volume fraction. A sensitivity study is then conducted over the model parameters to study parameter identifiability from system measurements. Effects of the initial temperature and initial amount of soot were studied as well. Results indicated that the model is most sensitive to the activation energy of GPF regeneration, agreeing with previous studies. Additionally, the model was shown to be able to predict the GPF temperature with less than 5% error when there was at most 20% uncertainty in the parameters. The results of the relationship between ceria (IV) oxide and the parameters, as well as the sensitivity analysis can be used simultaneously in the future for observer-based design.
Takahashi, Aki, Korneev, Slava, Onori, Simona
Smart DPF Regenerations - A Case Study of a Connected Powertrain Function2019-01-03164/2/2019
The availability of connectivity and autonomy enabled resources, within the automotive sector, has primarily been considered for driver assist technologies and for extending the levels of vehicle autonomy. It is not a stretch to imagine that the additional information, available from connectivity and autonomy, may also be useful in further improving powertrain functions. Critical powertrain subsystems that must operate with limited or uncertain knowledge of their environment stand to benefit from such new information sources. Unfortunately, the adoption of this new information resource has been slow within the powertrain community and has typically been limited to the obvious problem choices such as battery charge management for electric vehicles and efforts related to fuel economy benefits from adaptive/coordinated cruise control. In this paper we discuss the application of connectivity resources in the management of an aftertreatment sub-system, the Diesel Particulate Filter (DPF). Standard DPF regenerations are scheduled on an inferred soot load based on indirect indicators of system state, such as exhaust gas flow rate and pressure drop across the DPF and/or empirical models of engine out soot. Soot load estimation approaches such as these are necessary since a reliable method of a direct soot load measurement in a DPF is currently not available. In addition to model uncertainty it is also well known that regeneration control also suffers from uncertainty related to the drive routes, driver behavior, and traffic flow over the driven routes. These uncertainties force a conservative regeneration scheme, that does not fully exploit the soot trapping capacity of the DPF. This makes it difficult to guarantee any measure of uniform optimality over all vehicles. It is evident, however, that by leveraging information that allows a reduction in driver and traffic related uncertainties it may be possible to better schedule DPF regenerations and achieve some degree of performance benefit related to the overall efficiency of the regeneration process over the life of the vehicle. In this paper we present some initial results from such an effort that leverages cloud based real time traffic flow information from a traffic provider in making smart decisions related to the soot management over a DPF.
Hopka, Michael, Upadhyay, Devesh, Van Nieuwstadt, Michiel
Towards Quantitative Prediction of Urea Thermo-Hydrolysis and Deposits Formation in Exhaust Selective Catalytic Reduction (SCR) Systems2019-01-09924/2/2019
In order to assist in fast design cycle of Diesel engines selective catalytic reduction (SCR) exhaust systems, significant endeavor is currently being made to improve numerical simulation accuracy of urea thermo-hydrolysis. In this article, the achievements of a recently developed urea semi-detailed decomposition chemical scheme are assessed using three available databases from the literature. First, evaporation and thermo-hydrolysis of urea-water solution (UWS) single-droplets hanged on a thin thermocouple ring (127 μm) as well as on a thick quartz (275 μm), have been simulated at ambient temperature conditions ranging from 473K to 773K. It has been shown that the numerical results, in terms of evaporation rate and urea gasification, as well as droplet temperature history are very close to the experiments if the heat flux coming from the droplet support is properly accounted for. Indeed, an additional conduction flux has proved to be necessary in the evaporation model in order to account for the droplet heating coming from the support (i.e. thermocouple ring or quartz bead). This additional heat conduction flux has shown more critical for droplets suspended on a thick quartz. It is also argued that our detailed kinetic mechanism is able to ensure accurate thermal decompositions as long as the temperature inside the droplet is still nearly uniform. This assumption is shown to be true at low temperature and so, at low evaporation and thermo-hydrolysis rates. However, for high gas temperature, bubble nucleation near the support surface induces non-uniform temperature distribution.. This process makes accurate simulation of thermal decomposition extremely dependent on the local temperature inside such large suspended droplets. These results are also relevant and underline the modelling difficulties that we must tackle when it comes to studying the evaporation, boiling and thermolysis of liquid films and deposits on the exhaust walls. Next verification of the models has been carried out using UWS sprays injected in 6-m long pipe under typical Diesel engine exhaust manifold conditions. In this case, good agreement with experiments in terms of urea to ammonia (NH3) conversion efficiencies has been obtained under different temperatures and residence times. In addition, it proved that by-products (like solid biuret, Cyanuric acid and even ammelide) can be formed in the spray parcels upon water evaporation is completed during their travel to the exhaust catalyst inlet. These solid by-product particles may clog the catalyst inlet section.
Habchi, Chaouki, Quan, Shaoping, Drennan, Scott, Bohbot, Julien
Delamination and Porosity in Composites and Adhesives Using Solid and Particulate Powdered AerogelTBMG-339253/1/2019
NASA's Langley Research Center has developed a method that introduces solids and particulates — specifically aerogels — into composites or adhesives while they are being constructed. These additives survive as the structure is cured to serve as a testbed and standard. Once cured, the solid or particulate additive will behave as a delamination or porosity defect and will be indistinguishable from real delamination or porosity when inspected with popular nondestructive evaluation techniques such as ultrasound or thermography.
New Engine Optics to Fuel Future ResearchTBMG-338993/1/2019
An optical setup developed by researchers at Sandia's Combustion Research Facility and the Technical University of Denmark can now quantify the formation of soot — particulate matter consisting primarily of carbon — as a function of time and space for a variety of combustion processes. Initially, the researchers have focused on the combustion of liquid fuel sprays found in engines, where the extreme pressures and temperatures create an environment that is optically challenging.
Water Conditioning Agents for Aqueous Magnetic Particle InspectionAS4792B (Current)2/18/2019
This SAE Aerospace Standard (AS) covers water conditioning agents used to facilitate aqueous wet-method magnetic particle inspection.
AMS K Non Destructive Methods and Processes Committee
The Impact of Gasoline Direct Injection System Design on PM Emissions2019-01-00721/15/2019
Gasoline Direct Injection engines can have significantly higher particulate mass (PM) and particulate number (PN) emissions relative to equivalent displacement Port Fuel Injected engines. Both the EPA and California Air Resources Board have adopted new stringent standards to be phased in over the next 10 years. The California regulations continue to tighten to a 1 mg/mi PM limit that is phased-in beginning with model year 2025 with full compliance by model year 2028. This study examines the different fuel injection system technology improvements that will be used to attain the standards to as well as their relative costs, market penetration potential, emission reduction and fuel economy impacts. The identification of alternative approaches and the analysis of their impacts was performed in two tasks. The first task was a comprehensive literature review and the findings of the review are presented. In the second task, information on topics not fully informed by the literature review was obtained from interviews with experts at auto-manufacturers and fuel system suppliers. The information from the interviews was integrated with the findings from the literature review to develop a comprehensive understanding of vehicle PM emissions and the pathways that manufacturers could follow to comply with the 1 mg/mi standard.
Duleep, K. Gopal
Diffuse Back-Illuminated Extinction Imaging of Soot: Effects of Beam Steering and Flame Luminosity2019-01-00111/15/2019
This study presents diagnostic development of diffuse back-illuminated extinction imaging of soot. The method provides high temporal and spatial resolution of the line-of-sight optical density of soot (KL) in compression-ignited fuel sprays relevant to automotive applications. The method is subjected to two major sources of error, beam steering effects and broadband flame luminosity effects. These were investigated in detail in a direct injection combustion chamber with diesel fuel, under high and low sooting conditions. A new method for correcting flame luminosity effects is presented and involves measuring the flame luminosity using a separate high-speed camera via a beam splitter. The new method and existing methods are applied and the resulting flame luminosity correction errors are compared. The new method yields 50% lower errors than the most promising method (optical flow method). The impact on KL was investigated, showing that the KL uncertainty when using the optical flow method is unbounded for KL values above 2.7, while the new method has an uncertainty of 0.5 for the maximum KL value of 3.8. The new method yields overall lower uncertainties and is more suited to measuring KL in optical thick conditions. Large refractive index gradients in the path of the incident light cause false attenuation, resulting in ambiguity of the measured KL, referred to as beam steering. A detailed investigation of the beam steering effects caused by the non-uniformities in the diffused light source was performed. A beam steering model was made and qualitatively validated from experiments. The results from the beam steering model showed the importance of having a large collection angle, in order to average out small-scale non-uniformities in the light source. The model also showed that large-scale non-uniformities in the light source could affect the measurement even if the collection angle is large.
Bjørgen, Karl Oskar Pires, Emberson, David Robert, Lovas, Terese
The Effects of Injection Strategies on Particulate Emissions from a Dual-Injection Gasoline Engine2019-01-00551/15/2019
European standards have set stringent PN (particle number) regulation (6×1011 #/km) for gasoline direct injection (GDI) engine, posing a great challenge for the particulate emission control of GDI engines. Dual-injection, which combines direct-injection (DI) with port-fuel-injection (PFI), is an effective approach to reduce particle emissions of GDI engine while maintaining good efficiency and power output. In order to investigate the PN emission characteristics under different dual-injection strategies, a DMS500 fast particle spectrometer was employed to characterize the effects of injection strategies on particulates emissions from a dual-injection gasoline engine. In this study, the injection strategies include injection timing, injection ratio and injection pressure of direct-injection. The experimental results indicated that as the fuel percentage of direct-injection decreased, engine-out particle emissions also gradually declined, with the port-fuel-injection mode yielding the lowest PN emissions. There existed a turning point of direct-injection pulse width, by which the particulate emission characteristics of dual-injection were divided into two different parts. The best direct injection timing in the dual-injection mode to minimize PN emissions was closer to the exhaust top dead center than that in the direct-injection mode. Similar to gasoline-direct-injection, increasing direct-injection pressure in the dual-injection mode also yielded notable reductions in particle number, particle mass and geometry mean diameter (GMD). The experimental results in this paper provide important references for the development and calibration work of dual-injection gasoline engines.
Chen, Wenhao, Xia, Chun, Mao, Kerang, Tao, Jie, Fang, Junhua, Huang, Zhen
Contaminants Affecting the Formation of Soft Particles in Bio-Based Diesel Fuels during Degradation2019-01-00161/15/2019
Renewable fuels are essential in the field of heavy duty transportation if we are to reach a fossil-free society in the foreseeable future. However renewable diesel fuels based on fatty acid methyl ester (FAME) might face problems with degradation and with cold flow properties. From the perspective of an engine, this may cause problems in the fuel injection system, such as fuel filter clogging and injector deposits. These phenomena, especially fuel filter clogging, can be connected to gel-like soft particles, which could originate from degradation products as well as from byproducts created during biodiesel refining. In this study, soft particles from the degradation of bio-based diesel fuel were examined. The tested fuels included hydrogenated vegetable oils (HVO), rapeseed methyl ester (RME) and 10% blend of rapeseed methyl ester with standard diesel (B10). To test their potential to increase the formation of soft particles, contaminants such as water, metals and engine oil were included in the degradation methods. The formed insoluble products were analyzed with gravimetric means, scanning electron microscopy (SEM/EDX) and spectroscopy methods (FTIR). The results showed different behavior for each of the tested fuels. B10 was shown to be the most problematic, with the creation of gel-like soft particles. RME was less prone to create particles, probably due to its good solubility properties. HVO created the least sediments, possibly due to its high stability. According to the FTIR measurements, the captured insoluble sediments mainly consisted of polymerized oxidation products, acids and metal carboxylic ions. The type of metal influenced the chemical composition and the amount of insoluble sediment. Engine oil caused an increase in the amount of sediments. However the results also suggest that oil has a dampening effect for reactions between metals, water and fuels.
Csontos, Botond, Alim, Richard, Bernemyr, Hanna, Hittig, Henrik, Pach, Mayte
Heat of Vaporization and Species Evolution during Gasoline Evaporation Measured by DSC/TGA/MS for Blends of C1 to C4 Alcohols in Commercial Gasoline Blendstocks2019-01-00141/15/2019
Evaporative cooling of the fuel-air charge by fuel evaporation is an important feature of direct-injection spark-ignition engines that improves fuel knock resistance and reduces pumping losses at intermediate load, but in some cases, may increase fine particle emissions. We have reported on experimental approaches for measuring both total heat of vaporization and examination of the evaporative heat effect as a function of fraction evaporated for gasolines and ethanol blends. In this paper, we extend this work to include other low-molecular-weight alcohols and present results on species evolution during fuel evaporation by coupling a mass spectrometer to our differential scanning calorimetry/thermogravimetric analysis instrument. The alcohols examined were methanol, ethanol, 1-propanol, isopropanol, 2-butanol, and isobutanol at 10 volume percent, 20 volume percent, and 30 volume percent. The results show that total heat of vaporization of the alcohol gasoline blends is in line with the decreasing heat of vaporization in kilojoules per kilogram with increasing alcohol carbon number, as expected. Mass spectrometer results show that methanol fully evaporates at significantly lower fraction evaporated relative to other alcohols even though it is present at higher molar concentration at a fixed volumetric concentration. Certain alcohols, especially methanol and ethanol, can suppress the evaporation of aromatic compounds such as cumene during the evaporation process in some samples. While the use of mass spectrometry to analyze the composition of the evolving gas mixture provided useful results for a relatively simple research gasoline (FACE B), additional research is required to practically apply this methodology to more complex commercial gasolines.
Fioroni, Gina M., Christensen, Earl, Fouts, Lisa, McCormick, Robert
Modeling and Experimentation of GDI-Sized Particulate Filtration and Pressure-Drop Behavior in Uncoated Commercial DPF Substrates2019-01-00521/15/2019
Gasoline Direct Injection (GDI) is known to produce lower concentrations of smaller particulate matter (PM) compared to diesel combustion [1]. The lower concentration results in the absence of soot-cake formation on the filter channel wall and therefore filtration behavior deviates from the expected diesel particulate filter (DPF) performance. Therefore, studies of cake-less filtration regimes for smaller sized particulates is of interest for GDI PM mitigation. This work investigates the filtration efficiency of laboratory-generated particulates, representative of GDI-sized PM, in uncoated, commercial DPF cordierite substrates of varying porosities. Size-dependent particulate concentrations were measured using a Scanning Mobility Particle Sizer (SMPS), both upstream and downstream of the filters. By comparing these measured concentrations, the particle size-dependent filtration efficiency of filter samples was calculated. To predict filtration efficiency for these non-loaded particulate traps, the Opris and Johnson flow field model was updated to include sedimentation and thermophoretic terms and with soot-cake related filtration approximations removed. Experimental results showed excellent agreement with model predictions. Our study demonstrated that current DPFs are insufficient for deployment on GDI vehicles due to their low filtration efficiency for GDI-sized particles. GPFs (gasoline particulate filters) are essential and the newly developed filtration model can serve well to facilitate their design.
Sheppard, Jessica, Yang, Pengze, Strzelec, Andrea
Agglomeration and Nucleation of Non-Volatile Particles in a Particle Grouping Exhaust Pipe of a Euro VI Heavy-Duty Diesel Engine2019-01-00441/15/2019
The possibility of non-volatile particle agglomeration in engine exhaust was experimentally examined in a Euro VI heavy duty engine using a variable cross section agglomeration pipe, insulated and double walled for minimal thermophoresis. The agglomeration pipe was located between the turbocharger and the exhaust treatment devices. Sampling was made across the pipe and along the centre-line of the agglomeration pipe. The performance of the agglomeration pipe was compared with an equivalent insulated straight pipe. The non-volatile total particle number and size distribution were investigated. Particle number measurements were conducted according to the guidelines from the Particle Measurement Programme. The Engine was fuelled with commercially available low sulphur S10 diesel. Experiments conducted in heavy duty engine relevant operating points were done to sweep the effect of (i) Mass flow rate in the exhaust (ii) Temperature in the exhaust and (iii) Engine speed and thus exhaust pressure pulsation frequencies in the exhaust. The test matrix included eleven operating points at steady-state. The results show that, using the agglomeration pipe, neither significant non-volatile particle reduction nor noticeable change in particle size distribution could be proven. In the current study, nucleation of non-volatile particles could not be observed along the straight pipe. Furthermore, it was found that the variable cross-section agglomeration pipe and straight pipe showed similar results in the total particle number and particle size distribution with respect to non-volatile particles.
K, Arun Prasath, Stenlaas, Ola, Bernemyr, Hanna, Erlandsson, Anders
In-Cylinder GDI Soot via Visualization and Time-Resolved Total Cylinder Sampling2019-01-00371/15/2019
For better understanding, model development and its validation of in-cylinder soot formation processes of Gasoline Direct Injection (GDI) engines, crank-angle-resolved mass and size distribution of in-cylinder soot during a GDI combustion cycle were investigated via optical measurements and total cylinder sampling technique in an optically accessible Rapid Compression and Expansion Machine (RCEM). A direct-injection, spark-ignited and single-shot combustion event was achieved in the RCEM operated with engine speed 600 rpm, compression ratio 9.0, equivalence ratio 0.9 and natural aspiration. A three-component (iso-octane 65%, n-heptane 10%, toluene 25%) gasoline surrogate fuel and a multi-hole injector shared within the Japanese SIP Innovative Combustion Technology research program were used. As for the optical measurements, two-color method and laser/LED-based Diffused Back Illumination (DBI) high-speed imaging through sapphire windows on the cylinder head and the flat-top piston provided time-sequential in-cylinder soot mass. As for the total cylinder sampling, filter gravimetry and Portable Aerosol Mobility Spectrometer (PAMS) measurements of total-cylinder soot-laden gas provided crank-angle-resolved in-cylinder soot mass and size distribution. The total cylinder sampling was realized by replacing the cylinder head window with a stainless-steel diaphragm, rupturing the diaphragm at an arbitrary crank angle during combustion and rapidly expanding the total-cylinder soot-laden gas to effectively freeze secondary reactions and agglomeration of soot particles. The in-cylinder soot mass obtained by the above mentioned four different methods showed reasonable agreement each other both in increasing trend during combustion and quantitative soot mass. Measured variation of soot size distribution during combustion indicates that formation and agglomeration of soot are simultaneously occurring during combustion. Observation and morphology analysis of sampled soot via High-Resolution Transmission Electron Microscopy (HR-TEM) are also in progress.
Maruyama, Tomohisa, Sato, Yoshiumi, Endo, Kazuki, Tsukamoto, Takamichi, Aizawa, Tetsuya
Optical Diagnostics of Spray Characteristics and Soot Volume Fractions of n-Butanol, n-Octanol, Diesel, and Hydrotreated Vegetable Oil Blends in a Constant Volume Combustion Chamber2019-01-00191/15/2019
The effects of using n-butanol, n-octanol, fossil Diesel, hydrotreated vegetable oil (HVO), and blends of these fuels on spray penetration, flame and soot characteristics were investigated in a high-pressure high-temperature constant volume combustion chamber designed to mimic a heavy duty Diesel engine. Backlight illumination was used to capture liquid and vapor phase spray images with a high-speed camera. The flame lift-off length (LOL) and ignition delay were determined by analyzing OH* chemiluminescence images. Laser extinction diagnostics were used to measure the spatially and temporally resolved soot volume fraction. The spray experiments were performed by injecting fuels under non-combusting (623 K) and combusting (823 K) conditions at a fixed ambient air density of 26 kg/m3. A Scania 0.19 mm single straight hole injector and Scania XPI common rail fuel supply system were used to produce injection pressures of 120 MPa and 180 MPa. To evaluate the effect of cetane number (CN) variation on combustion processes and soot emissions, di-tertiary-butyl peroxide (DTBP) was added to one blend to modify its CN without greatly altering its composition. The different fuels exhibited similar vapor phase penetration, but their liquid phase penetration varied significantly with the fuels’ physical properties. HVO exhibited the longest steady state liquid penetration. A fuel has a longer ignition delay, resulting in a longer flame lift-off length and thus a lower soot optical thickness and soot volume fraction distribution. Compared to Diesel fuel, n-butanol blends and n-octanol produced much lower soot emissions because of their oxygen content, lower stoichiometric A/F ratio, and high latent heat of vaporization.
Zhang, Tankai, Andersson, Mats, Munch, Karin, Denbratt, Ingemar
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