Browse Topic: Nozzles

Items (295)

Method for Evaluating the Flow Properties of Pumpable Sealers

J2025_202101 (Current)

1/7/2021

This SAE Recommended Practice sets forth a method for evaluating the flow properties of automotive sealers that have been dispensed via a high pressure automatic system.

Materials, Processes and Parts Council

Low-Order Prediction of Mineral Dust Sticking Probability in Turboshaft Engines

F-0076-2020-16338

10/5/2020

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

Multimaterial Fiber “Ink” for 3D-Printed Devices

TBMG-359752/1/2020

A new method uses standard 3D printers to produce functioning devices with the electronics already embedded inside. The devices are made of fibers containing multiple interconnected materials that can light up, sense their surroundings, store energy, or perform other actions.

Self-Assembled Micro-Organogels Enable 3D Printing of Silicone Structures

TBMG-347527/1/2019

For the millions of people every year who have or need medical devices implanted, an advancement in 3D printing technology could enable significantly quicker implantation of devices that are stronger, less expensive, more flexible, and more comfortable than anything currently available. Such devices are molded, which could take days or weeks to create customized parts designed to fit an individual patient. The 3D printing method cuts that time to hours; additionally, small and complex devices such as pressure-sensitive valves, simply cannot be molded in one step.

High Strength Elevated Temperature Bolting Practice

ARP700C (Current)5/3/2019

This SAE Aerospace Recommended Practice (ARP) provides general information on the design and installation of threaded fasteners in high strength and high temperature applications in propulsion systems. Some of the more common definitions of fastener terminology are also provided.

E-25 General Standards for Aerospace and Propulsion Systems

Dispenser Nozzle Spouts for Liquid Fuels Intended for Use with Spark Ignition and Compression Ignition Engines

J285_201904 (Current)4/29/2019

Fuel Systems Standards Committee

Printing Technology Uses Sound Waves to Control Size of Liquid Droplets

TBMG-337022/1/2019

Liquid droplets are used in many applications, from printing ink on paper to creating microcapsules for drug delivery. Inkjet printing is the most common technique used to pattern liquid droplets, but it's only suitable for liquids that are roughly ten times more viscous than water. Many fluids of interest to researchers are far more viscous; for example, biopolymer and cell-laden solutions that are vital for biopharmaceuticals and bioprinting are at least 100 times more viscous than water. Some sugar-based biopolymers could be as viscous as honey, which is 25,000 times more viscous than water. The viscosity of these fluids also changes dramatically with temperature and composition, making it more difficult to optimize printing parameters to control droplet sizes.

Visual Analyses of End of Injection Liquid Structures and the Behaviour of Nozzle Surface-Bound Fuel in a Direct Injection Diesel Engine

2019-01-00591/15/2019

For efficiency, the majority of modern diesel engines implement multiple injection strategies, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potential contributor towards pollutant emissions. To investigate the underlying processes, highspeed optical measurements at the microscopic scale were performed inside a motored diesel engine under low load/idling conditions. Visualisation of the injector nozzle surface and near nozzle region permitted an indepth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface when the engine is not fired. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading. As the needle re-seated, the abrupt pressure drop inhibited atomisation. Large, slow moving, liquid structures were released into the cylinder with the capability of impinging on nearby surfaces, creating localised fuel rich regions, or escaping through the exhaust and contributing towards un-burnt hydrocarbon emissions. Large ligaments remained attached to the nozzle, with some fluid subsequently breaking away while the remaining fuel adhering the nozzle retracted back causing surface wetting. The EOI event was succeeded by further surface wetting due to the expansion of orifice-trapped gas dislodging nozzle-residing fuel that then overspilled onto the external surface. The drop in in-cylinder pressure elicited bubbling within the surface-bound fuel, further increasing the films spreading rate. The resulting bubble agglomerations collapsed in large chain reactions, projecting more fuel into the cylinder. Finally, as the intake valves closed, high velocity intake air was diverted towards the nozzle removing the remaining surface-bound fuel. As a result, a large volume of fuel was released into the combustion chamber after the EOI causing deposits on nearby surfaces or getting released through the exhaust where it would contribute towards un-burnt hydrocarbon emissions. It is likely that the anticipated increase in in-cylinder pressure and temperature if the engine was fired would either reduce the time-scale of these event or completely inhibit them. However, understanding the behaviour of the surface-bound fuel within this environment will aid designs that control surface wetting, thus inhibiting nozzle coking with the capacity to control internal deposits.

Sykes, Dan, de Sercey, Guillaume, Gold, Martin, Pearson, Richard, Crua, Cyril

Evaluation of Diesel Spray with Non-Circular Nozzle - Part I: Inert Spray

2019-01-00651/15/2019

Numerous studies have characterized the impact of high injection pressure and small nozzle holes on spray quality and the subsequent impact on combustion. Higher injection pressure or smaller nozzle diameter usually reduce soot emissions owing to better atomization quality and fuel-air mixing enhancement. The influence of nozzle geometry on spray and combustion of diesel continues to be a topic of great research interest. An alternate approach impacting spray quality is investigated in this paper, specifically the impact of non-circular nozzles. The concept was explored experimentally in an optically accessible constant-volume combustion chamber (CVCC). Non-reacting spray evaluations were conducted at various ambient densities (14.8, 22.8, 30 kg/m3) under inert gas of Nitrogen (N2) while injection pressure was kept at 100 MPa. Shadowgraph imaging was used to obtain macroscopic spray characteristics such as spray structure, spray penetration, and the spray cone angle. Analysis from image processing showed expected result of lower penetration rate and higher spray cone angle as ambient density increased. Two slot nozzles with different aspect ratios but similar flow area as compared with one of the circular nozzles were tested. Given a certain minor-to-major axis ratio of the non-circular nozzle, spray penetration of non-circular nozzle can be longer or shorter than that of the circular nozzle. At a similar condition, the spray cone angle was smaller for the non-circular nozzle compared to that of the circular nozzle. A mathematical model based on the work of Hiroyasu & Arai [1] was applied to predict spray tip penetration for all the tested nozzles. The model was then modified to predict spray penetration of non-circular nozzles. Non-circular nozzles were shown to have an impact on spray break-up and spray penetration, that can potentially promote the level of mixing. Validated 3D CFD simulation was used to provide insight into the spray and combustion of a non-circular nozzle. Subsequently, longer ignition delay was observed for non-circular nozzle as compared to a circular nozzle through simulation results.

Cung, Khanh, Moiz, Ahmed Abdul, Shah, Bansal, Kalaskar, Vickey, Miwa, Jason, Abidin, Zainal

Valve Flow Coefficients under Engine Operation Conditions: Pressure Ratios, Pressure and Temperature Levels

2019-01-00411/15/2019

Engine valve flow coefficients are not only used to characterize the performance of valve/port designs, but also for modelling gas exchange in 0D/1D engine simulation. Flow coefficients are usually estimated with small pressure ratios and at ambient air conditions. In contrast, the ranges for pressure ratio, pressure and temperature level during engine operation are much more extensive. In this work the influences of these three parameters on SI engine poppet valve flow coefficients are investigated using 3D CFD and measurements for validation. While former investigations already showed some pressure ratio dependencies by measurement, here the use of 3D CFD allows a more comprehensive analysis and a deeper understanding of the relevant effects. At first, typical ranges for the three mentioned parameters during engine operation are presented. A preliminary study for a simple nozzle geometry shows the suitability of the utilized 3D CFD code for partially overcritical flow, and demonstrates the limits of the fundamental nozzle flow equation. Steady flow simulations of two different four-stroke SI engine cylinder head geometries reveal that valve flow coefficients show noticeable dependencies on all three named parameters especially for small valve lifts, and flow direction from port into cylinder. Pressure recovery within and downstream valve gap influenced by valve gap boundary layer height is identified to be responsible for this behavior. In the reverse flow direction the existence of pressure recovery can also be confirmed, but its effects are found to be superimposed by flow necking and separation effects which especially depend on valve design. For validation, the 3D CFD results are compared with valve flow coefficients measured at flow test bench with extended pressure ratios and pressure levels. The measurements confirm the valve flow coefficient dependencies found by simulations.

Fasse, Sven, Grill, Michael, Bargende, Michael

Spray Characterization of Gasoline Direct Injection Sprays Under Fuel Injection Pressures up to 150 MPa with Different Nozzle Geometries

2019-01-00631/15/2019

Maximum fuel injection pressures for GDI engines is expected to increase due to positive effects on emissions and engine-efficiency. Current GDI injectors have maximum operating pressures of 35 MPa, but higher injection pressures have yielded promising reductions in particle number (PN) and improved combustion stability. However, the mechanisms responsible for these effects are poorly understood, and there have been few studies on fuel sprays formed at high injection pressures. This paper summarizes experimental studies on the properties of sprays formed at high injection pressures. The results of these experiments can be used as inputs for CFD simulations and studies on combustion behavior, emissions formation, and combustion system design. The experiments were conducted using an injection rate meter and optical methods in a constant volume spray chamber. Injection rate measurements were performed to determine the injectors’ flow characteristics. Spray imaging was performed using a high-speed video camera. Several spray properties such as the liquid spray penetration, spray plume angle, and the spray breakup point were determined as functions of the fuel injection pressure and injected fuel mass by image post-processing. The impact of fuel pressure on spray droplet size was also investigated using two-component Phase Doppler Interferometry. Piezoelectric injectors for diesel engines were used with modified nozzles that produce sprays resembling those generated in gasoline engines. Experiments were performed with fuel injection pressures ranging from 20 to 150 MPa, and chamber pressures of 0.1 and 0.6 MPa. In addition, four different nozzles with three different nozzle configurations and either 6 or 10 holes were used to determine how hole geometry affects spray formation. The study’s key findings are that increasing the fuel injection pressure advances spray breakup and creates smaller droplets, improving mixture formation and accelerating evaporation. The nozzle type and the ambient pressure both significantly affect aspects of spray behavior such as spray tip development.

Yamaguchi, Akichika, Koopmans, Lucien, Helmantel, Arjan, Karrholm, Fabian Peng, Dahlander, Petter

Outwardly Opening Hollow-Cone Diesel Spray Characterization under Different Ambient Conditions

2018-01-16949/10/2018

The combustion quality in modern diesel engines depends strictly on the quality of the air-fuel mixing and, in turn, from the quality of spray atomization process. So air-fuel mixing is strongly influenced by the injection pressure, geometry of the nozzle duct and the hydraulic characteristics of the injector. In this context, spray concepts alternative to the conventional multi-hole nozzles could be considered as solutions to the extremely high injection pressure increase to assure a higher and faster fuel-air mixing in the piston bowl, with the final target of increasing the fuel efficiency and reducing the engine emissions. The study concerns an experimental depiction of a spray generated through a prototype high-pressure hollow-cone nozzle, under evaporative and non-evaporative conditions, injecting the fuel in a constant-volume combustion vessel controlled in pressure and temperature up to engine-like gas densities in order to measure the spatial and temporal fuel patterns. The spray evolution was characterized by means of two optical techniques, schlieren and Mie scattering. Schlieren images take into account of both liquid and vapor fraction, while the Mie-scattering for the liquid fraction. The images were processed through a customized procedure developed in MATLAB to better outline the contours of the liquid phase and the vapor/atomized zones. Results showed this nozzle configuration appears intrinsically capable of generating a finely atomized spray homogeneously and circumferentially distributed contributing to a better fuel-air mixing level.

Montanaro, Alessandro, Allocca, Luigi, Beatrice, Carlo, Ianniello, Roberto

Assessment of the New Features of a Prototype High-Pressure “Hollow Cone Spray” Diesel Injector by Means of Engine Performance Characterization and Spray Visualization

2018-01-16979/10/2018

The application of more efficient compression ignition combustion concepts requires advancement in terms of fuel injection technologies. The injector nozzle is the most critical component of the whole injection system for its impact on the combustion process. It is characterized by the number of holes, diameter, internal shape, and opening angle. The reduction of the nozzle hole diameter seems the simplest way to promote the atomization process but the number of holes must be increased to keep constant the injected fuel mass. This logic has been applied to the development of a new generation of injectors. First, the tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate. The vertical movement of the needle generates an annulus area for the fuel delivery on 360 degrees, so controlling the atomization as a function of the vertical plate position. Second, on the base of the obtained results, the authors have introduced a new nozzle configuration. This is characterized by a hybrid fuel injection concept, composed of five preferential fuel jets, generated via a specific design of the internal nozzle geometry, and an additional circle-shaped fuel injection, with the aim of using the air between the jets. The experimental investigation has been performed on a single-cylinder metal engine to assess the new concept injector performance by varying the main control parameters (electrical command, nozzle tip protrusion, test point, etc.). Then a deeper investigation of the injector characteristics in different conditions has been performed in an optical single-cylinder diesel engine via digital imaging to catch information on its functioning. A better control of the fuel delivery has been observed compared to the previous injector configuration. Images of the injection process showed that the fuel assumed a good symmetric shape at the nozzle exit for both the jets and the circular plume. A better utilization of the available volume is granted by the new concept injector. The improved mixing quality has shown advantages in terms of combustion efficiency and engine-out emissions.

Sequino, Luigi, Belgiorno, Giacomo, Di Blasio, Gabriele, Mancaruso, Ezio, Beatrice, Carlo, Vaglieco, Bianca Maria

Characterizing Spray Propagation of GDI Injectors under Crossflow Conditions

2018-01-16969/10/2018

In DISI engines spray distribution and atomization directly influence mixture formation, the quality of combustion and the resulting emissions. Constant Volume Chambers (CVC) are commonly used to characterize sprays of gasoline injectors. The CVCs provide good optical access but the flow condition of the engine cannot be reproduced. Optically accessible engines in contrast deliver realistic flow conditions but have restricted optical access. In former investigations we compared the spray propagation of different injectors in constant volume chambers and in optical accessible engines. These results showed a clear difference of the spray propagation in the CVC and the engine, especially at high charge motion conditions in the engine. To find an appropriate way to investigate the impact of different charge motion a flow channel was built with adjustable crossflow velocities from 5-50 m/s. The spray propagation during the injection process was measured with high-speed shadowgraphy. Two main parameters are introduced to describe the crossflow stability. The location of the intensity center represents the global spray deflection. The second parameter is the ratio between the areas of high and low optical spray density to express the spray “blow-out” under crossflow conditions. Five different injectors were investigated at injection pressures between 100 bar and 170 bar to determine their stability and behavior under crossflow conditions. The results show a clear dependence of the spray propagation on crossflow velocities. With increasing injection pressure the stability against crossflow is increasing. Furthermore, the injectors show different behavior at the same conditions due to their different nozzle designs.

Welss, Richard, Bornschlegel, Sebastian, Wensing, Michael

An Experimental Investigation on Spray Mixing and Combustion Characteristics for Spray C/D Nozzles in a Constant Pressure Vessel

2018-01-17839/10/2018

The Engine Combustion Network (ECN) is a coordinate effort from research partners from all over the world which aims at creating a large experimental database to validate CFD calculations. Two injectors from ECN, namely Spray C and D, have been compared in a constant pressure flow vessel, which enables a field of view of more than 100 mm. Both nozzles have been designed with similar flow metrics, with Spray D having a convergent hole shape and Spray C a cylindrical one, the latter being therefore more prone to cavitation. Although the focus of the study is on reacting conditions, some inert cases have also been measured. High speed schlieren imaging, OH* chemiluminescence visualization and head-on broadband luminosity have been used as combustion diagnostics to evaluate ignition delay, lift off length and reacting tip penetration. Parametric variations include ambient temperature, oxygen content and injection pressure variations. Results extend the range of variation of previously reported experiments in the literature for such nozzles, showing good agreement with such previous results and enlarging the available database for CFD validation. A systematic shorter lift-off length is observed for Spray C, while ignition delay from broadband luminosity and schlieren visualization show no clear difference between both nozzles. Comparison against literature results from Spray A has also been performed, from which behavior of the larger nozzles is seen to be highly affected by the slower mixing process.

Pastor, Jose V., Garcia-Oliver, Jose M, Garcia, Antonio, Morales López, Andrés

The Nozzle Flows and Atomization Characteristics of the Two-Component Surrogate Fuel of Diesel from Indirect Coal Liquefaction at Engine Conditions

2018-01-16919/10/2018

Recently, all world countries facing the stringent emission regulations have been encouraged to explore the clean fuel. The diesel from indirect coal liquefaction (DICL) has been verified that can reduce the soot and NOx emissions of compression-ignition engine. However, the atomization characteristics of DICL are rarely studied. The aim of this work is to numerically analyze the inner nozzle flow and the atomization characteristics of the DICL and compare the global and local flow characteristics of the DICL with the NO.2 diesel (D2) at engine conditions. A surrogate fuel of the DICL (a mixture of 72.4% n-dodecane and 27.6% methylcyclohexane by mass) was built according to its components to simulate the atomization characteristics of the DICL under the high-temperature and high-pressure environment (non-reacting) by the Large Eddy Simulation (LES). The simulation results show that the DICL is more likely to form cavitation compared with D2, and the turbulence level at the orifice exit is larger for DICL. The liquid penetration of DICL is shorter than that of D2, while the vapor penetrations between DICL and D2 have no obvious difference. The spray cone angle of DICL is larger than that of D2. In addition, the gas-phase axial velocity of the DICL along the spray center line is slightly larger than that of D2 in the upstream of the spray. Moreover, the SMD of the DICL is larger than that of D2. Generally, this study is helpful to understand the differences in the inner nozzle flow features and the atomization characteristics between DICL and D2.

Huang, Zhong, Zhang, Wenzheng, Xia, Jin, Ju, Dehao, Han, Dong, Lu, Xing-Cai

Spray Parameters of Fuel Blends of Recycled Lubricating Oil and Diesel

2018-01-16939/10/2018

The use of alternative fuels consisting of mineral and synthetic waste substances such as recycled lubricating oil blended with diesel is a measure to mitigate the environmental impact of the fossil fuels. However, to inject these fuel blends into contemporary engines without changes to their components, it must maintain or improve the fuel injection characteristics compared to neat diesel, in order to maintain or improve the engine performance. In the present research, the spray parameters of injected fuel, such as length, angle and atomization particle diameter in terms of the Sauter mean diameter (SMD), are modeled depending on the characterization of different concentration of the recycled lubricating oil blended with diesel. It was found that the same nozzle geometry of the injectors can provide an equivalent fuel spray performance for different concentrations of these alternative fuel blends, and that the increase of the recycled lubricating oil in the fuel blend reduced the wear of the needle and nozzle of the injector. The densities and viscosities between each fuel type are very similar and any correction of injection duration or pressure is not required. Due to simple distillation and blending process, alternative and environmentally friendly fuel blends can be obtained to reduce the combustion of fossil diesel and reuse waste pollutant substances as a sustainable and immediately applicable solution for modern engines and fuel injection systems.

Gutierrez, Marcos, Castillo, Andres, Iniguez, Juan, Reyes, Gorky

High Strength Elevated Temperature Bolting Practice

ARP700B (Historical)8/23/2018

E-25 General Standards for Aerospace and Propulsion Systems

Effect of Micro-Hole Nozzle on Diesel Spray and Combustion

2018-01-03014/3/2018

The influence of nozzle geometry on spray and combustion of diesel continues to be a topic of great research interest. One area of promise, injector nozzles with micro-holes (i.e. down to 30 μm), still need further investigation. Reduction of nozzle orifice diameter and increased fuel injection pressure typically promotes air entrainment near-nozzle during start of injection. This leads to better premixing and consequently leaner combustion, hence lowering the formation of soot. Advances in numerical simulation have made it possible to study the effect of different nozzle diameters on the spray and combustion in great detail. In this study, a baseline model was developed for investigating the spray and combustion of diesel fuel at the Spray A condition (nozzle diameter of 90 μm) from the Engine Combustion Network (ECN) community. Upon validation of parameters such as spray penetration, lift-off length, and ignition delay the baseline simulation was extended to study different nozzle orifice diameters. All simulations were performed using a constant-volume combustion chamber (CVCC) geometry with similar ambient conditions of pressure (60 bar) and temperature (900 K). It was shown that liquid length was shortened to a “minimum” level after nozzle diameter was reduced to 50 μm or lower. Moreover, the decrease in nozzle diameter enhanced spray atomization and gas entrainment to the fuel jet. This caused the location of the lifted flame to move closer to the nozzle tip. While local equivalence ratio along the spray centerline was significantly reduced with smaller nozzle diameters, the fuel/air ratio remained relatively unchanged (lean) at the jet boundary where the lifted flame stabilized. Higher injection pressures in the simulation also enhanced fuel-air mixing, resulting in shorter lift-off lengths and lower soot formation. The results from this study agree with literature findings of the trend in soot reduction with very small nozzle diameter. Potential improvements to the current models include different kinetic mechanisms for prediction of soot precursors such as benzene (C6H6), and better matching in terms of ignition and flame structure. A full engine combustion chamber simulation confirmed the soot reduction phenomenon associated with the smaller nozzle diameter.

Cung, Khanh, Bitsis, Daniel Christopher, Briggs, Thomas, Kalaskar, Vickey, Abidin, Zainal, Shah, Bansal, Miwa, Jason

Contrary Effects of Nozzle Length on Spray Primary Breakup under Subcooled and Superheated Conditions

2018-01-03024/3/2018

Nozzle length has been proven influencing fuel spray characteristics, and subsequently fuel-air mixing and combustion processes. However, almost all existing related studies are conducted when fuel is subcooled, of which fuel evaporation is extremely weak, especially at the near nozzle region. In addition, injector tip can be heated to very high temperature in SIDI engines, which would trigger flash boiling fuel spray. Therefore, in this study, effect of nozzle length on spray characteristics is investigated under superheated conditions. Three single-hole injectors with different nozzle length were studied. High speed backlit imaging technique was applied to acquire magnified near nozzle spray images based on an optical accessible constant volume chamber. Fuel pressure was maintained at 15 MPa, and n-hexane was chosen as test fuel. Fuel temperature ranged from 25 °C to 85 °C, and ambient pressure ranged from 20 kPa to 200 kPa, which provided a wide range of subcooled and superheated conditions. Results show that nozzle length has contrary effect on spray primary breakup process under subcooled and superheated conditions. Longer nozzle led to narrower near nozzle spray under subcooled conditions due to stronger restriction effect of nozzle wall. However, longer nozzle could result in stronger in-nozzle fuel evaporation and more in-nozzle bubbles near the nozzle exit under superheated conditions, which led to faster and stronger fuel atomization and evaporation processes, and thus wider fuel spray.

Wu, Shengqi, Xu, Min, Yang, Shangze, Yin, Peng

Modeling the Dynamic Coupling of Internal Nozzle Flow and Spray Formation for Gasoline Direct Injection Applications

2018-01-03144/3/2018

A numerical study has been carried out to assess the effects of needle movement and internal nozzle flow on spray formation for a multi-hole Gasoline Direct Injection system. The coupling of nozzle flow and spray formation is dynamic in nature and simulations with pragmatic choice of spatial and temporal resolutions are needed to analyze the sprays in a GDI system. The dynamic coupling of nozzle flow and spray formation will be performed using an Eulerian-Lagrangian Spray Atomization (ELSA) approach. In this approach, the liquid fuel will remain in the Eulerian framework while exiting the nozzle, while, depending on local instantaneous liquid concentration in a given cell and amount of liquid in the neighboring cells, part of the liquid mass will be transferred to the Lagrangian framework in the form of Lagrangian parcels. Such approach requires solving an additional transport equation apart from the conservation equations of mass, momentum, species, energy, and turbulence in Eulerian framework. This additional equation is termed as the Σ equation. Σ represents the liquid-gas interfacial area per unit volume in a given computational cell. Once the liquid mass is transferred to the Lagrangian framework, parcels undergo breakup, collision, coalescence and evaporation, similar to any typical Lagrangian spray approach. This hybrid approach will have the potential of capturing the transient flow characteristics due to needle movement transcending downstream and affecting time-fluctuating spray phenomenon. The Spray G condition from the Engine Combustion Network (ECN) has been chosen for this study. Parametric studies on the effect of turbulence models, Eulerian to Lagrangian mass transfer criterion, breakup models have been performed. While these simulations are very expensive, they are expected to be more predictive than the standing approach of initializing a Lagrangian simulation with a ‘blob’ injection model. Simulation predictions with ELSA are shown to be in good agreement with measured data on spray penetration, and gas velocities, available in the literature.

Saha, Kaushik, Srivastava, Priyesh, Quan, Shaoping, Senecal, P. K., Pomraning, Eric, Som, Sibendu

Optimal Injection Strategies to Compensate for Injector Aging in Common Rail Fuel Systems

2018-01-11604/3/2018

Aging effects such as coking or erosive damage that occur in fuel injection nozzles are known to deteriorate the engine performance. This article proposes an optimization method to compensate for injector aging and to control the combustion behavior over engine lifetime by adapting the injection strategy. First, a control-oriented combustion model is presented, which takes the condition of the injection nozzle into account. In combination with a simulation model of the entire fuel injection system from a previous study, the model is capable of predicting the heat release rate (HRR) at different working conditions. Measurements with a single-cylinder diesel engine were performed, using injectors with modified and aged nozzles, to validate the proposed combustion model and particularly to analyze the influence of injector aging. Using the simulation model, optimal injection strategies were obtained by applying a line search optimization scheme to recover a reference HRR trajectory. Simulation results of the proposed method demonstrate the great potential for improving long-term engine efficiency and controlling exhaust emissions.

Hofmann, Oliver, Schuckert, Sebastian, Wachtmeister, Georg, Rixen, Daniel

Oil Circulation Rate in Ejector Cooling Cycles

2018-01-00774/3/2018

In this study, the influence of compressor speed, ejector motive nozzle needle position and evaporator inlet metering valve opening on the oil circulation rates (OCRs) of an automotive R744 transcritical standard ejector cycle was experimentally investigated. Significantly higher OCR (~10%) was observed at the evaporator inlet of the ejector cycle than at the high pressure side. It has been observed that evaporator OCR was increased with increasing compressor speed. When the motive nozzle needle moved towards the nozzle throat, both compressor discharge flow rate and evaporator OCR were observed to be significantly lowered. As the evaporator inlet metering valve opening was adjusted, the compressor mass flow rate did not vary significantly while the evaporator mass flow rate decreased with decreasing metering valve opening. The evaporator OCR decreased from 6.5% to 2.2% as the metering valve opening varied from 86% to 27%.

Zhu, Jingwei, Botticella, Francesco, Elbel, Stefan

Methodology and Tools to Predict GDI Injector Tip Wetting as Predecessor of Tip Sooting

2018-01-02864/3/2018

With upcoming emission regulations particle emissions for GDI engines are challenging engine and injector developers. Despite the introduction of GPFs, engine-out emission should be optimized to avoid extra cost and exhaust backpressure. Engine tests with a state of the art Miller GDI engine showed up to 200% increased particle emissions over the test duration due to injector deposit related diffusion flames. No spray altering deposits have been found inside the injector nozzle. To optimize this tip sooting behavior a tool chain is presented which involves injector multiphase simulations, a spray simulation coupled with a wallfilm model and testing. First the flow inside the injector is analyzed based on a 3D-XRay model. The next step is a Lagrangian spray simulation coupled with a wallfilm module which is used to simulate the fuel impingement on the injector tip and counter-bores. Lower injection pressures and a rounded edge at the nozzle inlet due to hydro-erosive grinding are increasing the wallfilm on the injector. The simulations are verified with measurements including high speed microscopic video analyzes of the injector tip during injection. The simulated wallfilm on the injector tip matches well with the measurement results. As a last step, the tested engine is simulated in one operating point including the injector nozzle geometry for a full 720° CrA cycle. Variations of charge motion, injector and fuel temperatures are investigated to reduce the tip wetting and improve fuel evaporation. An increased fuel temperature and high tip temperatures show a promising reduction of the injector tip wallfilm. Further simulations performed with multi-component fuels allow a prediction of tip wetting for region based different gasoline distillation curves.

Fischer, Armin, Thelliez, Marina

Application of Vortex Control to an Automotive Transcritical R744 Ejector Cycle

2018-01-00604/3/2018

Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycles is that the ejector cycle performance is sensitive to working condition changes which are common in automotive applications. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. The ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect ejector cycle COP. This paper presents the experimental results of the application of a new two-phase nozzle restrictiveness control mechanism to an automotive transcritical R744 ejector cycle. This new control mechanism, vortex control, utilizes an adjustable vortex at the nozzle inlet to control the nozzle restrictiveness on the two-phase flow without changing the physical dimensions of the nozzle geometry. The test results show that nozzle restrictiveness can be adjusted with this new mechanism. Under common working conditions, with vortex control the ejector motive inlet pressure can be varied from 8609 kPa to 9637 kPa for constant motive inlet temperature and total motive mass flow rate.

Zhu, Jingwei, Elbel, Stefan

LES Investigation of ECN Spray G2 with an Eulerian Stochastic Field Cavitation Model

2018-01-02914/3/2018

Due to an ongoing trend of high injection pressures in the realm of internal combustion engines, the role of cavitation that typically happens inside the injector nozzle has become increasingly important. In this work, a large Eddy Simulation (LES) with cavitation modeled on the basis of an Eulerian Stochastic Field (ESF) method and a homogeneous mixture model is performed to investigate the role of cavitation on the Engine Combustion Network (ECN) spray G2. The Eulerian stochastic field cavitation model is coupled to a pressure based solver for the flow, which lowers the computational cost, thereby making the methodology highly applicable to realistic injector geometries. Moreover, the nature of the Eulerian stochastic field method makes it more convenient to achieve a high scalability when applied to parallel cases, which gives the method the edge over cavitation models that are based on Lagrangian tracking. The result of the Eulerian stochastic field simulation is compared against that from a typical single volume fraction solver for validation. Vortex structures and its correspondence to cavitation are shown, and the behavior of the size Probability Density Function (PDF) at different probe locations at different times are acquired to demonstrate the capability of the Eulerian stochastic field model to capture cavitation and potentially providing more statistical information in each cell as compared to the typical single volume fraction solver. Major cavitation zones that are observed in the result indicates the important role of cavitation in ECN spray G2, therefore inferring a need to take cavitation into consideration in future spray studies.

Chen, Boxiong, Oevermann, Michael

Experimental Analysis of Fuel and Injector Body Temperature Effect on the Hydraulic Behavior of Latest Generation Common Rail Injection Systems

2018-01-02824/3/2018

The present paper describes the effect of thermal conditions on the hydraulic behavior of Diesel common rail injectors, with a particular focus on low temperatures for fuel and injector body. The actual injection system thermal state can significantly influence both the injected quantity and the injection shape, requiring proper amendments to the base engine calibration in order to preserve the combustion efficiency and pollutant emissions levels. In particular, the introduction of the RDE (Real Driving Emission) test cycle widens the effective ambient temperature range for the homologation cycle, this way stressing the importance of the thermal effects analysis. An experimental test bench was developed in order to characterize the injector in an engine-like configuration, i.e. fuel pump, piping, common rail, pressure control system and injectors. One of the injectors is used for the measurement of injection rate time profile by means of a Zeuch method-based injection analyzer, mean injected volume per shot and dynamic pressure time-history at pump outlet and injector inlet. The fuel temperature, measured at the fuel pump inlet, and the injector body temperature are independently conditioned in a range between −10 °C and 90 °C. Latest generation common rail injectors - featuring the first a pressure-balanced pilot stage, the other a three-way valve pilot stage respectively - were tested over a wide range of thermal conditions as combination of fuel and injector body temperatures, injection pressure level (up to 2000 bar), and injection strategies (solo-main, pilot-main and main-post injection patterns). The experimental results showed a strong effect of thermal conditions on the injector hydraulics. The injected volume can be varied up to 30% compared to the reference operating condition (Tfuel = 40 °C, Tbody = 90 °C). The injection rate analysis evidenced that the injector closure timing can be seriously affected by the system thermal state, while the nozzle steady flow is typically less influenced by the fuel and injector body temperature in the examined range. It was also evidenced a different temperature effect for different pilot stage architectures. In one case the temperature reduction led to an injection volume decrease and in the other case, comparable differences where observed but with a completely opposite trend.

Cavicchi, Andrea, Postrioti, Lucio, Pesce, Francesco Concetto, Ferrara, Umberto

Experimental and Computational Investigation of Subcritical Near-Nozzle Spray Structure and Primary Atomization in the Engine Combustion Network Spray D

2018-01-02774/3/2018

In order to improve understanding of the primary atomization process for diesel-like sprays, a collaborative experimental and computational study was focused on the near-nozzle spray structure for the Engine Combustion Network (ECN) Spray D single-hole injector. These results were presented at the 5th Workshop of the ECN in Detroit, Michigan. Application of x-ray diagnostics to the Spray D standard cold condition enabled quantification of distributions of mass, phase interfacial area, and droplet size in the near-nozzle region from 0.1 to 14 mm from the nozzle exit. Using these data, several modeling frameworks, from Lagrangian-Eulerian to Eulerian-Eulerian and from Reynolds-Averaged Navier-Stokes (RANS) to Direct Numerical Simulation (DNS), were assessed in their ability to capture and explain experimentally observed spray details. Due to its computational efficiency, the Lagrangian-Eulerian approach was able to provide spray predictions across a broad range of conditions. In general, this “engineering-level” simulation was able to reproduce the details of the droplet size distribution throughout the spray after calibration of the spray breakup model constants against the experimental data. Complementary to this approach, higher-fidelity modeling techniques were able to provide detailed insight into the experimental trends. For example, interface-capturing multiphase simulations were able to capture the experimentally observed bimodal behavior in the transverse interfacial area distributions in the near-nozzle region. Further analysis of the spray predictions suggests that peaks in the interfacial area distribution may coincide with regions of finely atomized droplets, whereas local minima may coincide with regions of continuous liquid structures. The results from this study highlight the potential of x-ray diagnostics to reveal salient details of the near-nozzle spray structure and to guide improvements to existing primary atomization modeling approaches.

Battistoni, Michele, Magnotti, Gina M., Genzale, Caroline L., Arienti, Marco, Matusik, Katarzyna E., Duke, Daniel J., Giraldo, Jhoan, Ilavsky, Jan, Kastengren, Alan L., Powell, Christopher F., Marti-Aldaravi, Pedro

Evaluation of Shot-to-Shot In-Nozzle Flow Variations in a Heavy-Duty Diesel Injector Using Real Nozzle Geometry

2018-01-03034/3/2018

Cyclic variability in internal combustion engines (ICEs) arises from multiple concurrent sources, many of which remain to be fully understood and controlled. This variability can, in turn, affect the behavior of the engine resulting in undesirable deviations from the expected operating conditions and performance. Shot-to-shot variation during the fuel injection process is strongly suspected of being a source of cyclic variability. This study focuses on the shot-to-shot variability of injector needle motion and its influence on the internal nozzle flow behavior using diesel fuel. High-speed x-ray imaging techniques have been used to extract high-resolution injector geometry images of the sac, orifices, and needle tip that allowed the true dynamics of the needle motion to emerge. These measurements showed high repeatability in the needle lift profile across multiple injection events, while the needle radial displacement was characterized by a much higher degree of randomness. A robust and previously validated computational setup from the authors’ research group using a commercial computational fluid dynamics (CFD) code has been adapted for the eight-hole heavy-duty common-rail diesel injector used for the measurements. The simulation results obtained using the x-ray-scanned geometry have been validated against available experimental data of mass flow rate at the nozzle exit. The fuel mass flow rate has then been analyzed at three different injection pressures that cover the conditions at which the injector typically operates during normal engine operation. Finally, the average off-axis motion of the needle has been perturbed (based on the variability found in the experimental measurements) to generate three new cases that present different amplitude and phasing of the radial displacement with respect to the baseline average motion. This revealed the effects of off-axis motion on shot-to-shot and orifice-to-orifice variations.

Torelli, Roberto, Matusik, Katarzyna E., Nelli, Kyle C., Kastengren, Alan L., Fezzaa, Kamel, Powell, Christopher F., Som, Sibendu, Pei, Yuanjiang, Tzanetakis, Tom, Zhang, Yu, Traver, Michael, Cleary, David J.

Single-Hole Asymmetric GDI Injector: Influence of the Drill Angle and the Counter-Bore under Flash-Boiling and Non-Flash-Boiling Conditions

2018-01-02884/3/2018

Sac-type nozzles, which are often used in gasoline direct injection (DI), induce asymmetry to the spray. The drill angle, that is, the angle between the axis of the nozzle and the axis of the injector, is one of the key causes of the asymmetric flow. Despite its significance, the influence of the drill angle on spray is poorly understood. In the current work, a parametric study has been carried out using single-hole sac-type nozzles by varying the drill angle. The drill angle was varied from a value of 0° to 45° in steps of 15°. Apart from the geometric variation, the ambient pressure and the fuel temperature were varied to achieve flash-boiling and non-flash-boiling spray conditions. Simulations were carried out using an in-house computational fluid dynamics (CFD) solver that accounts for thermodynamic non-equilibrium coupled with a liquid-gas interface-area-density transport model to account for primary atomization of the fuel. The spray angle was calculated on the basis of a threshold analysis applied to the liquid-gas interface-area-density. The results indicate that the drill angle has a significant influence on the near-nozzle spray, where larger drill angles cause wider sprays. An analogy between a stepped-hole nozzle and a convergent-divergent nozzle was speculated in recent experimental and computational studies. Therefore, to further the understanding of this proposed analogy, the current study also explored the influence of the counter-bore on the ensuing spray. An analysis of the pressure field and the static pressure drop along the axis of the nozzle shows that the counter-bore acts like an expansion chamber, thereby causing flash-boiling sprays to behave like underexpanded supersonic jets and non-flash-boiling sprays to behave like overexpanded jets. However, a further investigation of this hypothesis is necessary before its potential use as a design tool.

Rachakonda, Sampath K., Paydarfar, Arman, Schmidt, David

Effects of the Residual/Sucked Air Bubbles on Diesel Near - Nozzle Spray Structure

2017-01-231410/8/2017

Study of the spray formation in vicinity of the nozzle is essential to better understand and predict the physical processes involved in the diesel atomization. The initial spray patterns were found to be different from one injection to another during our visualization experiments, which was carried out based on a long distance microscope with a high speed camera in this work. It was found that the initial spray might contain a clear single mushroom, tail region and intact liquid column, or have a tail in front of the mushroom without changing its direction. Occasionally, it presented as a double-mushroom shape, or did not include a clear mushroom. Our visualization results showed that the various spray structures were observed at different injection pressures and different injection cycles under the same injection pressure. The difference of spray patterns may be due to the residual fuel/air bubbles surviving from the last injection or sucking into the nozzle during the needle opening, turbulent nature of the flow and the unsteady movement of the injector needle, while the reasons are not identified. In order to explain the various spray patterns, effects of the distribution of the simplified air bubbles inside the nozzle on the spray patterns at the start stages of the injection were further investigated with a combination of the LES method and VOF model coupling the cavitating flow inside the orifice. A higher injection pressure was set due to the faster the spray under the larger the injection pressure, and the operating condition was closer to the realistic diesel condition. The study confirmed that the initial mushroom and the tail were generated by the residual/sucked bubbles, and the main mushroom occurred because of the boundary layer theory. The location, size and amount of the residual/sucked air bubbles were responsible for the variation of initial spray structures between different injections. Moreover, the cavitation model was shown to play a role in the development of spray.

Guo, Genmiao, He, Zhixia, Wang, Qian, Sun, Shenxin, Chen, Zhou

Fluid Structure Interaction Analysis of Acrylic Optically Transmissive Nozzles

2017-01-230910/8/2017

In this paper, a contrast experiment has been carried out for discussing the phenomenon of fuel dripping at the end of injection by using the different nozzles with varied materials. The experiment results show that the nozzle deformation has an important effect on the fuel dripping at the end of injection. The duration of the fuel shut-off process with the steel nozzle which producing smaller deformation is shorter than the polymethyl methacrylate nozzle. The mass of fuel dripping with the steel nozzle is less. For implementing a deep analysis on the experimental phenomenon about the fuel dripping with the polymethyl methacrylate nozzle, a three dimensional numerical simulation research was carried out for analyzing the influence of fuel flow inside nozzle on the solid deformation and stress distribution of the nozzle by using Fluid-Structure-Interaction method. The simulation results show that the deformation and the stress are mainly occurred in the sac and the inlet of the orifice. And the maximum stress has been observed at the entrance of the sac. The maximum stress is over the adhesive force and cause the failure of the optically transmissive nozzle. Then the fluid volume change with the injection pressure and the fluid flow characteristic considering the solid deformation were also researched. The results of this research show that the solid deformation of polymethyl methacrylate nozzle lead to a delay of the injector fuel shut-off time which comparing to the real injector made by steel, and the total fuel mass discharging from the nozzle is slightly increase. The solid deformation also lead to a fact that the fuel is continually discharged from the optically transmissive nozzle over a long time after the closing of injection, similar to that seen in the experimental results.

Wen, Hua, Liang, Shuaishuai, Chen, Peng, Jiang, Guangjun

Comparison of Shadowgraph Imaging, Laser-Doppler Anemometry and X-Ray Imaging for the Analysis of Near Nozzle Velocities of GDI Fuel Injectors

2017-01-2302

10/8/2017

The fuel spray behavior in the near nozzle region of a gasoline injector is challenging to predict due to existing pressure gradients and turbulences of the internal flow and in-nozzle cavitation. Therefore, statistical parameters for spray characterization through experiments must be considered. The characterization of spray velocity fields in the near-nozzle region is of particular importance as the velocity information is crucial in understanding the hydrodynamic processes which take place further downstream during fuel atomization and mixture formation. This knowledge is needed in order to optimize injector nozzles for future requirements. In this study, the results of three experimental approaches for determination of spray velocity in the near-nozzle region are presented. Two different injector nozzle types were measured through high-speed shadowgraph imaging, Laser Doppler Anemometry (LDA) and X-ray imaging. Correlation among these three methods is used to classify the benefits and limitations of each measurement technique. The combination of these conceptually different measurement approaches provides a better insight into the complex phenomena of spray penetration and mixture preparation along with near-nozzle effects such as tip wetting in order to optimize future HDEV injector generations.

Knorsch, Tobias, Mamaikin, Dmitrii, Leick, Philippe, Rogler, Philipp, Wang, Jin, Li, Zhilong, Wensing, Michael

Effects of Hole Diameter and Injection Pressure on Fuel Spray and Its Evaporation Characteristics of Multi-Hole Nozzle for Diesel Engine

2017-01-230510/8/2017

The performance of a diesel engine largely depends on the spray behavior and mixture formation. Nozzle configurations and operating conditions are important factors that influence spray development. Using numerical and experimental methods, this study focused on the spray development of multi-hole nozzles under non-evaporating and evaporating conditions to compare the influence of nozzle hole diameter and injection pressure on spray characteristics. High-speed video observation was employed to study the properties of spray development under the non-evaporating condition, while the Laser Absorption Scattering technique was used in the observation and quantitative analysis of evaporating spray characteristics in the evaporating condition. In addition, computational fluid dynamics study results published previously [1] were correlated with the current experimental results to provide more detailed explanations about the mechanism of the characteristics of spray behavior. As for the effects of hole diameter, the evaporation ratio increased when the nozzle with smaller hole diameter was used at the initial injection phase. However, especially after injection, the evaporation ratio increased with increasing nozzle hole diameter because of the shorter injection duration. With regard to the effect of injection pressure, high injection pressure accelerated the internal flow that promotes the high cavitation level inside the nozzle. High injection pressure also provides high momentum, which prolongs the spray tip penetration. As a result, the evaporation ratio increases with the increase in injection pressure. The combined effects of nozzle hole diameter and injection pressure under similar fuel injection rates were investigated in the last section. The results show the distinct features for each condition although they have similar injection rate curves.

Yamauchi, Jun, Dong, PengBo, Nishida, Keiya, Ogata, Youichi

Effects of Nozzle Hole Diameter on Diesel Sprays in Constant Injection Mass Condition

2017-01-230010/8/2017

As known, the constant injection mass is a criterion for measuring the thermal efficiency of diesel engines. In this study, the effects of nozzle hole diameter on diesel free-spray characteristics were investigated in constant injection mass condition. The experiment was performed in a constant volume combustion chamber equipped with a high pressure common-rail injector that can change nozzles. Three single-hole axis nozzles with different hole diameters were used. High speed camera and Schlieren visualization set-up were used to capture the spray behaviors of liquid phase and vapor phase respectively. For liquid phase spray, the higher nozzle hole diameter, the higher were the liquid phase spray penetration rate and the saturated liquid phase spray penetration length. The saturated liquid phase spray penetration length wound not grow but oscillate around different mean values at the steady stage. In addition, the increase of nozzle hole diameter increased the saturated liquid phase spray cone angle. For vapor phase spray, the variation laws of vapor phase spray penetration lengths could be divided into nonlinear increase period and linear increase period. The effects of nozzle hole diameter on vapor phase spray penetration rate were negligible in the nonlinear increase period, but the higher nozzle hole diameter, the higher was the vapor phase spray penetration rate in the linear increase period. The higher nozzle hole diameter, the higher were the increase-rate of vapor phase spray cone angles and the saturated vapor phase spray cone angles. The reduction of nozzle hole diameter increased the pure vapor phase spray penetration tip length.

Du, Wei, Lou, Juejue, Liu, Fushui

Feed Mechanism and Method for Feeding Minute Components

TBMG-2769510/1/2017

Electrical circuits such as printed wiring boards or hybrid microcircuits designed to utilize surface mount electrical components are commonly assembled by computer-controlled automated equipment. These machines typically use a vacuum nozzle to pick up and handle the components during assembly. Three methods are commonly used to feed surface mount components to automatic assembly equipment: tape reel feeders, linear or bowl-type vibratory feeders, or waffle-style packages.

Analysis of a Prototype High-Pressure “Hollow Cone Spray” Diesel Injector Performance in Optical and Metal Research Engines

2017-24-00739/4/2017

Technologies for direct injection of fuel in compression ignition engines are in continuous development. One of the most investigated components of this system is the injector; in particular, main attention is given to the nozzle characteristics as hole diameter, number, internal shape, and opening angle. The reduction of nozzle hole diameter seems the simplest way to increase the average fuel velocity and to promote the atomization process. On the other hand, the number of holes must increase to keep the desired mass flow rate. On this basis, a new logic has been applied for the development of the next generation of injectors. The tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate that moves vertically. The plate motion allows to obtain an annulus area for the delivery of the fuel on 360 degrees; while the plate lift permits to vary the atomization level of the spray. The experimental activities have been performed on a single-cylinder metal engine in order to evaluate the new injector concept functionality in typical engine working conditions. Then a deeper investigation of injector the characteristics has been performed in an optical single-cylinder diesel engine via high speed digital imaging in order to catch information on its operation. The results have shown a good response of the injector fuel delivery control but penalties in terms of emissions and efficiency compared to multihole nozzles. Images of the injection process showed that the fuel assumed an asymmetric shape at the exit of the injector affecting the mixing quality and, then, the combustion efficiency.

Beatrice, Carlo, Belgiorno, Giacomo, Di Blasio, Gabriele, Mancaruso, Ezio, Sequino, Luigi, Vaglieco, Bianca Maria

Ejector Energy-Saving Technology for Mobile Air Conditioning Systems

2017-01-01203/28/2017

This study reports on a new generation ECS (Ejector Cycle System) which includes a highly efficient ejector and a novel system configuration. The ejector is working as a fluid jet pump that recovers expansion energy which is wasted in the conventional refrigeration cycle decompression process, and converts the recovered expansion energy into pressure energy and raises the compressor suction pressure. Consequently, the ejector system can reduce power consumption of the compressor by using the above mentioned pressure-rising effect and improve energy efficiency of the refrigeration cycle. The ejector consists of a nozzle, a suction section, a mixing section and a diffuser. The objective of this study is to improve actual fuel economy of all vehicles by ejector technology. The previous generation ECS was reported in 2012 SAE World Congress1. Now, a new generation ECS has been successfully developed and released in the market for Mobile Air Conditioning systems as of 2013. It achieves higher energy efficiency through the development of ARC (Active flow Ratio Control. It means to control the refrigerant flow ratio of the suction flow to the total flow by separating gas-liquid two phase flow), improved design of each ejector part, and improved internal flow distribution inside the evaporator. The ejector is integrated into the tank of evaporator like the previous generation, so there is no impact to vehicle packaging space. Test results demonstrated that the new generation ECS reduced annual power consumption of compressor by 10% compared to previous generation and by 20% compared to conventional expansion valve systems. The new generation ejector technology can significantly improve actual fuel consumption of Mobile Air Conditioning systems and contribute to global greenhouse gas reduction.

Shan, Zhiwei, Kawamoto, Yoichiro, Ogata, Gota

Numerical Investigation of the Impact of Nozzle Endwall Clearance Distribution on Variable Nozzle Turbine Performance

2017-01-10343/28/2017

As the variable nozzle turbine(VNT) becomes an important element in engine fuel economy and engine performance, improvement of turbine efficiency over wide operation range is the main focus of research efforts for both academia and industry in the past decades. It is well known that in a VNT, the nozzle endwall clearance has a big impact on the turbine efficiency, especially at small nozzle open positions. However, the clearance at hub and shroud wall sides may contribute differently to the turbine efficiency penalty. When the total height of nozzle clearance is fixed, varying distribution of nozzle endwall clearance at the hub and shroud sides may possibly generate different patterns of clearance leakage flow at nozzle exit that has different interaction with and impact on the main flow when it enters the inducer. It is possible that variation of the nozzle endwall clearances between hub side and shroud side, e.g. tiny transverse movement of nozzle vanes along their pivotal shafts, results in significant deviations in turbine aerodynamic performances at some operation conditions. In this paper, the deviations of turbine efficiency at three typical nozzle vane openings and different rotational speeds, with different distribution of nozzle endwall clearances were numerically analyzed. It was found that when the total height of nozzle clearances is fixed, changing the nozzle endwall clearance distribution between the hub and shroud sides can impact the turbine performance, and shifting clearance towards hub side can effectively improve the VNT turbine efficiency, especially at high speed ratio and small vane open positions.

Zhao, Ben, Hu, Liangjun, Engeda, Abraham, Sun, Harold

Study on the Interaction of Clearance Flow and Shock Wave in a Turbine Nozzle

2017-01-10393/28/2017

Radial flow Variable Nozzle Turbine (VNT) enables better matching between the turbocharger and engine. At partial loading or low-end engine operating points, the nozzle vane opening of the VNT is decreased to achieve higher turbine efficiency and transient response, which is a benefit for engine fuel consumption and emission. However, under certain small nozzle opening conditions (such as nozzle brake and low-end operating points), strong shock waves and strong nozzle clearance flow are generated. Consequently, strong rotor-stator interaction between turbine nozzle and impeller is the key factor of the impeller high cycle fatigue and failure. In present paper, flow visualization experiment is carried out on a linear turbine nozzle. The turbine nozzle is designed to have single-sided clearance, and the Schlieren visualization method is used to describe the formation and development process of clearance flow and shock wave under different clearance and expansion ratio configurations. Numerical simulations are also performed to investigate the flow structure and the interaction behavior between shock wave and clearance flow in details. Results indicate that for the investigated turbine nozzle, the shock wave is squeezed and bent in the opposite direction of the main flow in the interaction region. In the location close to the end-wall, the shock wave is truncated by the clearance flow and mixed downstream-wise with a distorted shock wave structure. Furthermore, increasing the clearance size causes the distortion of the shock wave structure near the end-wall, while the shock wave intensity near mid-span is increased. Meanwhile, the clearance leakage flow and shock wave can cause the static pressure of the nozzle vane exit to fluctuate violently.

Lei, Xinguo, Qi, Mingxu, Sun, Harold, Shi, Xin, Hu, Liangjun

A Study of Diesel Fuel Injector Deposit Effects on Power and Fuel Economy Performance

2017-01-0803

3/28/2017

Injector cleanliness is well characterised in the literature [1,2,3,4] as a key factor for maintained engine performance in modern diesel cars. Injector deposits have been shown to reduce injector flow capacity resulting in power loss under full load; however, deposit effects on fuel economy are less well characterised. A study was conducted with the aim of developing an understanding of the impact of diesel injector nozzle deposits on fuel economy. A series of tests were run using a previously published chassis dynamometer test method. The test method was designed to evaluate injector deposit effects on performance under driving conditions more representative of real world driving than the high intensity test cycle of the industry standard, CEC DW10B engine test, [1]. The efficacy of different additive levels in maintaining injector cleanliness and therefore power and fuel economy was compared in a light duty Euro 5 certified vehicle. Full load power loss in low or non-additised fuels was observed (~3%), whereas a keep-clean dose of a deposit control additive (DCA) fully maintained performance. Furthermore, a statistically robust link between injector fouling and an increase in specific fuel consumption (~0.7%) at steady state was established. In addition, mechanisms were proposed for the link between injector fouling and changes in fuel consumption derived from in-cylinder measurements throughout the test duration, as well as exploration of how fuel consumption effects change across the operating range outside of the test cycle.

Behrendt, Christiane, Smith, Alastair