Browse Topic: Engine mechanical components

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Acoustic Assessment in a Small Displacement Diesel Engine2014-32-01291/30/2026
In the last years, the increasing concern for the environmental issues of IC engines has promoted the development of new strategies capable of reducing both pollutant emissions in atmosphere and noise radiation. Engines can produce different types of noise: 1) aerodynamic noise due to intake and exhaust systems and 2) surface radiated noise. Identification and analysis of noise sources are essential to evaluate the individual contribution (injection, combustion, piston slap, turbocharger, oil pump, valves) to the overall noise with the aim of selecting appropriate control strategies. Previous paper focused on the combustion related noise emission. The research activity aimed at diagnosing and controlling the combustion process via acoustic measurements. The optimal placement of the microphone was selected, where the signal was strongly correlated to the in-cylinder pressure development during the combustion process. Analysis and processing of the sound emission allowed the acoustic contribution of the combustion event to be isolated. Some indices capable of relating the combustion noise radiation back to the combustion development were defined. This paper presents an experimental activity devoted to analyze the entire noise generation process of a small displacement diesel engine. The purpose was to identify the contribution of the different sources (mechanical, combustion, fluid dynamic) to the overall emission. The methodology here proposed analyze the specific signature in the frequency domain of each source. The final objective was to use the microphone signal acquired in a proper selected location, to obtain indications about the effective strategies to achieve noise reduction. The repetitiveness of the measurements was guaranteed by a network encircling the engine. Microphones were placed in different positions and tests were performed in the complete engine operative field. In the paper, the experimental set-up is described, the methodology is presented. Results are then shown and discussed.
Chiatti, Giancarlo, Recco, Erasmo, Chiavola, Ornella, Conforto, Silvia
Automation Title for Group Code D22PC-Auto-1752670240025 (Current)7/16/2025
Automation Abstract for Group Code D22
Airlines Electronic Engineering Committee
TightAIR12122024A (Current)12/12/2024
New Scoop
A-6 Aerospace Actuation, Control and Fluid Power Systems
Impact of Detailed SFC on Hybrid-Electric VTOL SizingF-0080-2024-13415/7/2024
Data from a 3.43 kW piston engine-generator is integrated with rotorcraft sizing analysis to assess its impact. First, the measured SFC map of the powerplant is modeled. Second, the sizing is validated with XV-15 flight test aircraft and NASA conceptual reference quadrotor. The power and platform models are then integrated to size a hypothetical quadrotor bi-plane unmanned air vehicle of 5 lb payload. Several cases for how the engine can be operated to meet the vehicle torque and speed are detailed. The key conculsion is that a detailed SFC model is as important as the aircraft model. Without it, errors in tip speed reduction, gross weight, and range would be quite dramatic from 50-100%. A tip speed reduction to 65% hover in cruise was found to strike the best balance between rotor performance and engine performance of the hypothetical aircraft, resulting in a gross weight of 50 lb and range of 120 nm at 60 kts cruise speed.
Arace, Matt, Datta, Anubhav
USUALLY UNOBSERVED REFINEMENTS OF AUTOMOBILE CONSTRUCTION0800031/1/2024
ELLSWORTH, JOHN MAGEE, FAY, THOMAS J.
Research on the Secondary Motion of Engine Piston Considering the Transport of Lubricating Oil03-17-03-002411/21/2023
Abstract At present, it is generally considered in the analysis of the secondary motion of engine piston that the piston skirt–cylinder liner friction pair is fully lubricated in an engine operating cycle. However, in practice, when the piston moves upward, the amount of lubricating oil at the inlet may not ensure that the friction pair is fully lubricated. In this article, the secondary motion of piston is studied when the transport of lubricating oil is considered to determine the lubrication condition of piston skirt–cylinder liner friction pair. The secondary motion of piston is solved based on the combined piston motion model, hydrodynamic lubrication model, asperity contact model, and lubricating oil flow model. The secondary motion equation of piston is solved by the Broyden method. The hydrodynamic lubrication equation is solved by the finite difference method. The asperity contact between piston skirt and cylinder liner is calculated by the Greenwood model. The flow of lubricating oil is analyzed based on the theory of fluid mechanics. The results indicate that, when the actual transport of lubricating oil is considered to determine the lubrication condition of piston skirt–cylinder liner friction pair, the secondary motion of piston is remarkably different from that in which the flooded lubrication is assumed in an engine operating cycle. Therefore, it is helpful to improve the accuracy and make the analysis closer to the actual engine operating situation that the transport of lubricating oil is considered in the analysis of the secondary motion of engine piston.
Liu, Jihai, Sun, Jun
Parameters Optimization of a Double Gyroscope Concept for a Two-Wheel Vehicle15-15-02-00094/20/2022
Abstract The concept of making a two-wheeled self-stabilizing vehicle can be a possibility soon. These vehicles use control moment gyroscopes (CMGs) to provide enough torque for the vehicle to prevent it from rolling and falling to the ground. CMGs can be used with different numbers and configurations. In this article, the aim is to offer a design procedure for a double gyroscope system, which can be used for any two-wheel vehicle to be self-stabilized. The procedure is based on using optimization algorithms in reaching the optimum double gyroscope configuration for a certain two-wheel vehicle to reach a zero-degree roll angle in the least time possible, which is the novel part of the procedure. A design procedure for a double gyroscope with the yaw axis as a spinning axis for a two-wheel vehicle is offered. This procedure has been tested for both a small two-wheel robot and a two-wheel enclosed vehicle. The research method started with a presentation of motion equations, followed by a discussion of the use of the PID cascade controller and its tuning process. Also setting up the simulation and finally using the gradient descent method of optimization with both the sequential quadratic programming (SQP) and the interior point algorithms to optimize the simulation results to achieve the optimum design. The simulations were carried out using an initial roll angle of 15°. Before optimization, the small two-wheel robot reached 0° roll angle in nearly 5 seconds at 2000 RPM flywheel spinning velocity and the two-wheel enclosed vehicle reached 0° roll angle in nearly 2.5 seconds at 4000 RPM flywheel spinning velocity. After optimization for the same spinning velocities the small two-wheel robot reached 0° in nearly 2 seconds but the enclosed two-wheel vehicle did not show a significant improvement with the results due to the good performance of the initial design of the vehicle.
Aboelsaoud, Mostafa, Taha, Ahmed Abdelsalam, Mabrouk, Mohamed Yasser, Aboelazm, Mohamed, Elgamal, Hassan
A Numerical Study on the Effect of a Pre-Chamber Initiated Turbulent Jet on Main Chamber Combustion2022-01-04693/29/2022
To elucidate the complex characteristics of pre-chamber combustion engines, the interaction of the hot gas jets initiated by an active narrow throated pre-chamber with lean premixed CH4/air in a heavy-duty engine was studied computationally. A twelve-hole KAUST proprietary pre-chamber geometry was investigated using CONVERGE software. The KAUST pre-chamber has an upper conical part with the spark plug, and fuel injector, followed by a straight narrow region called the throat and nozzles connecting the chambers. The simulations were run for an entire cycle, starting at the previous cycle's exhaust valve opening (EVO). The SAGE combustion model was used with the chemistry modeled using a reduced methane oxidation mechanism based on GRI Mech 3.0, which was validated against in-house OH chemiluminescence data from the optical engine experiments. Two different piston geometries, a flat piston geometry, and a more realistic bowl piston geometry were studied to understand the influence of jet on main chamber combustion. Varying the piston geometries results in different free jet times and hence main chamber combustion characteristics. Pre-chamber fuel ratio (PCFR) 6% of the total amount of fuel was investigated while keeping the global excess air ratios (λ) condition a constant value of 2.0. Both piston cases resulted in similar pre-chamber pressurization, with almost the same pre-chamber discharge and the equal pressure difference between pre-and main-chamber (ΔP) at the start of jet ejection. Different combustion behaviors were observed on analysis of the heat release rate in the main chamber. The importance of turbulence generated by the pre-chamber-initiated jets was further studied. It was observed that free jet time is a critical factor in developing turbulence in the main chamber. This increase in turbulence helps in increasing the burning velocity causing faster combustion. The influence of the jet-piston interaction is also analyzed as that determines the combustion behavior in the later CAD.
Sanal, Sangeeth, Echeverri Marquez, Manuel, Silva, Mickael, Cenker, Emre, Im, Hong G.
Gland Design, O-Ring and Other SealsAS4716D (Current)11/9/2021
This SAE Aerospace Standard (AS) provides standardized gland (groove) design criteria and dimensions for O-ring seal glands for static and dynamic applications, and other seals.
A-6C2 Seals Committee
Basic Aircraft Oxygen Systems DesignAIR825/14 (Current)8/11/2021
This slash document collects general reference material related to gaseous oxygen system flow requirements and sizing calculations. This document will assist oxygen system equipment designers and operators to establish systems and equipment requirements. The document consists of charts, tables, system schematics, system requirements, and sample calculations for system sizing.
A-10 Aircraft Oxygen Equipment Committee
Minimum Standard for Portable Gaseous, Oxygen EquipmentAS1046C (Historical)8/11/2021
This standard is intended to apply to portable compressed gaseous oxygen equipment. When properly configured, this equipment is used either for the administration of supplemental oxygen, first aid oxygen or smoke protection to one or more occupants of either private or commercial transport aircraft. This standard is applicable to the following types of portable oxygen equipment: a Continuous flow 1 Pre-set 2 Adjustable 3 Automatic b Demand flow 1 Straight-demand 2 Diluter-demand 3 Pressure-demand c Combination continuous flow and demand flow.
A-10 Aircraft Oxygen Equipment Committee
7.0.104 - Managing Distributed Systems Development through Model-Based E/E-Architecture DesignSAE-PP-002802/4/2021
This paper sketches a model based E/E-architecture analysis and design process for the development of distributed in-vehicle systems. Together with a model based system development, the sketched analysis and design process results in a cost-effective E/E-architecture which fulfills all the requirements for the developed in-vehicle system. As an example scenario, the integration of a new feature into a car, which requires integrating a new distributed function into the existing E/E-architecture of the car, is shown.
Lname, Fname
7.0.101 - A New Image De-hazing Method for Safety Critical ADAS ApplicationsSAE-PP-002772/4/2021
Driver safety and Advanced Driver Assistance Systems (ADAS) is gaining lot of importance these days. In some countries, there are strict regulations in place which mandate the use of certain ADAS features in automobiles. However, as the need for these safety critical systems increases, the challenges associated also increase. These challenges can arise due to technology, human factors or due to nature. In countries like India, where one can expect different weather conditions with changing geography, the associated challenges are mainly due to the natural factors like haze, fog, rain and smoke. This poses a challenging problem in terms of visibility for the drivers as well as in vision based ADAS; thereby, leading to many fatal road accidents. In this paper, a novel pre-processing technique, which addresses the interesting problem of enhancing the perceptual visibility of an image that is degraded by atmospheric haze, is proposed. The solution to this problem is presented by combining model (Beer Lambert model) based and non-model based technique of haze removal. The combined hybrid model picks the best haze free image from the series of non-hazy outputs, that are derived based on multiple scattering coefficients of the input hazy image. The idea here is to restore the true color of an image that is affected by the atmospheric haze. In comparison with the state of the art methods that are available in literature, the proposed method is shown to be capable of recovering better haze-free images both in terms of visual perception and quantitative evaluation. The proposed method promises better perceptual understandings and visibility restoration for vision based ADAS under hazy driving conditions.
Lname, Fname
6.0.116 - Development of 6 Years Old Child Virtual Model by Automatic ScalingSAE-PP-002712/4/2021
Traffic accidents cause one of the highest numbers of severe injuries in the whole population. The numbers of deaths or seriously injured citizens prove that traffic accidents and their consequences are still a serious problem to be solved. A lot of effort is devoted to both passive and active safety systems development. The transportation standards usually define safety requirements by regulations (e.g. ECE-R94, 96/79/EC and ECE-R95, 96/27/EC in Europe) with specific dummies for children to be used. The dummies include hardware sensors for monitoring accelerations, loads and other signals and each dummy is developed for a specific scenario, but there are limitations of these dummies, such as only a specific age or calibration just for a specific test. Taking into account that the consequence of a traffic accident is highly influenced by the stature of the body, virtual human body models, including those for children, start to play a significant role because they can be scaled or even personalized towards a particular population or even a particular person. The paper contributes to the field of vehicle safety technology concerning child restraint systems development, assessment and optimization with a virtual numerical approach. The goal of the paper is to exploit the previously developed scaling algorithm to create a virtual model of a six-year-old (6YO) child and to compare its response to the virtual dummy used for child safety in order to propose an automatic scaling process for a population-based vehicle safety assessment. The automatic scaling algorithm developing virtual human body models for a given age and gender is used to create the virtual 6YO child model. The algorithm scales body dimensions and particular segments' mass and the flexibility of the body is driven by flexindex and stiffness scaling. The performance of the automatically developed virtual 6YO child model was tested in frontal and lateral directions. The frontal response was tested with a standard sled test simulation using the standardized AAMA pulse in the frontal direction. The lateral response was tested with a side barrier impact test. The results of both tests were compared to the validated virtual Q6 Child Dummy FE model. The paper shows good performance of the automatic scaling process for developing 6YO virtual model for safety assessment. The automatically developed 6YO child model corresponds well from both the anthropological point of view and performance point of view to the existing validated dummy model.
Mutagaana, Festo
6.0.101 - Piston Sealing System Structure Design for Automobile's Lightweight Auto-TransmissionSAE-PP-002572/4/2021
Current automobile's auto-transmission has problems of defects and cost reduction because of welding process and very complicated assembly process due to individualized transmission piston and sealing components. Also, size and heavy weight of transmission piston components are the source of low mileage because they are made of aluminum, steel material. In this study, therefore, we perform structure design for piston sealing system which integrates piston and sealing material for automobile's lightweight auto-transmission. Also performed stress analysis through finite element analysis to secure required suitable strength when internal pressure is applied after assemble.
Mutagaana, Festo
2.0.101 - Experimental Study of cooling of Continuously Variable Transmission (CVT) in ScooterSAE-PP-002102/1/2021
The continuously variable transmission (CVT), which was conceptualized more than 500 years ago, is just now beginning to replace traditional transmissions in some automobiles. It is mostly used in scooter transmission. Engine power is transmitted to wheel through belt drive between two pulleys. The diameter of belt contact with pulley can change continuously and hence provide infinite gear ratios between driver and driven shafts. This technology leads to a smoother ride of vehicle. Heat is generated inside CVT due to friction between drive belt and clutch pulley. Amount of heat generated is even more due to clutch slippage during acceleration and deceleration. This will affect the service life of CVT components such as front movable drive (FMD), clutch pulley, clutch outer, and belt. In scooters generally, air cooling is preferred over liquid cooling. Cooling is achieved by incorporating centrifugal fan inside CVT housing. For better durability/service life, the degree of heat generated at CVT components should be minimal. The objective of this work is to identify the parameters causing change in temperature of CVT components and to evaluate its surface temperature in accordance with changed parameters. With reference to this, experiments were conducted with requisite design modification inside CVT housing, which enhances cooling effect. Amongst, variables determining air flow rate, are studied and their effect on temperature inside CVT housing is observed experimentally. Keeping the previous variables unaltered, further design modifications related to air flow pattern are done and cumulative effect of all variables is observed. Experiments were performed on an 110cc scooter engine by following customer driving pattern on chassis dynamometer. Results showed that design modifications intended for better cooling effect, has brought down temperature at CVT components. So, desired cooling effect is observed inside CVT housing imparting better service life of CVT components.
Mutagaana, Festo
REMOVAL TOOLS, CONNECTOR, ELECTRICAL CONTACT, (FORK TYPE, WRAP POST/CRIMP REMOVABLE) TYPE II, CLASS 1, COMPOSITION CAS81969/4A (Current)1/26/2021
AE-8C2 Terminating Devices and Tooling Committee
REMOVAL TOOLS, CONNECTOR, ELECTRICAL CONTACT, (FORK TYPE, WRAPPOST/CRIMP REMOVABLE) TYPE II, CLASS 1, COMPOSITION CAS81969/11A (Current)1/26/2021
AE-8C2 Terminating Devices and Tooling Committee
INSTALLING AND REMOVAL TOOLS, CONNECTOR, ELECTRICAL CONTACT, TYPE I AND II, CLASS 2, COMPOSITION BAS81969/10A (Current)1/26/2021
AE-8C2 Terminating Devices and Tooling Committee
Lubricating Oil, Aircraft Piston Engine (Ashless Dispersant)J1899_202010 (Current)10/28/2020
This SAE Standard establishes the requirements for lubricating oils containing ashless dispersant additives to be used in four-stroke cycle, reciprocating piston aircraft engines. This document covers the same lubricating oil requirements as the former military specification MIL-L-22851. Users should consult their airframe or engine manufacturers manuals for the latest listing of acceptable lubricants.
E-38 Aviation Piston Engine Fuels and Lubricants
Spark Arrester Test Procedure for Large Size EnginesJ342_202010 (Current)10/6/2020
This SAE Recommended Practice establishes equipment and procedures for the evaluation of the effectiveness and other performance characteristics of spark arresters or turbochargers used on the exhaust system of large engines normally used in a railroad locomotive, stationary power plant, and other similar applications. This document does not cover applications requiring flame arresting, exhaust gas cooling, or isolation from explosive gases. Two test methods are presented: a laboratory test using ambient air (cold test) and an engine test using exhaust gases (hot test). The hot test is preferred. Arresters tested by the provisions of this document can be expected to perform as tested when tilted no more than 45 degrees from their normal position. Test results from a spark arrester or turbocharger evaluated by the hot test can be applied to different engines of similar design, provided the data shows it to be effective in the applicable flow ranges. Certain design and performance characteristics, which represent current requirements by regulatory agencies for qualification and approval under this document, are listed in Appendix A.
SAE IC Powertrain Steering Committee
Infrared/Visible Optical Diagnostics of RCCI Combustion with Dieseline in a Compression Ignition Engine2020-01-05574/14/2020
Compression ignition engines are widely used for transport and energy generation due to their high efficiency and low fuel consumption. To minimize the environmental impact of this technology, the pollutant emissions levels at the exhaust are strictly regulated. To reduce the after-treatment needs, alternative strategies as the low temperature combustion (LTC) concepts are being investigated recently. The reactivity controlled compression ignition (RCCI) uses two fuels (direct- and port- injected) with different reactivity to control the in-cylinder mixture reactivity by adjusting the proportion of both fuels. In spite of the proportion of the port-injected fuel is typically higher than the direct-injected one, the characteristics of the latter play a main role on the combustion process. Use of gasoline for direct injection is attractive to retard the start of combustion and to improve the air-fuel mixing process. In this work, the influence of the direct-injected fuel properties on RCCI combustion mode is studied in an optical compression ignition engine. Gasoline fuel is injected in the intake manifold while a blend of gasoline and diesel (a.k.a. dieseline) is directly injected into the cylinder. Non-conventional optical diagnostics in the visible and infrared spectra are applied for the direct investigation of the in-cylinder phenomena during the injection and the combustion processes. A low-luminosity, mainly kinetically controlled combustion mode has been observed.
Sequino, Luigi, Mancaruso, Ezio, Monsalve-Serrano, Javier, Garcia, Antonio
A New Cavitation Algorithm to Support the Interpretation of LIF Measurements of Piston Rings2020-01-10914/14/2020
Laser induced fluorescence (LIF) is used to investigate oil transport mechanisms under real engine conditions. The engine oil is mixed with a dye that can be induced by a laser. The emitted light intensity from the dye correlates with the residual oil at the sensor position and the resulting oil film thicknesses can be precisely determined for each crank angle. However, the general expectation is not always achieved, e.g. an exact representation of piston ring barrel shapes. In order to investigate the responsible lubrication effects of this behavior, a new cavitation algorithm for the Reynolds equation has been developed. The solution retains the mass conservation and does not use any switch function in its mathematical approach. In contrast to common approaches, no vapor-liquid ratio is used, but one or several bigger bubbles are approximated, as have been observed in other experiments already. As a result, not only the known boundary conditions for the Reynolds equation become unnecessary, but the solution also gives a clearer idea as to the shape of the cavitation bubble. The combination of simulated oil film thicknesses, the resulting cavitation bubbles and the fixed field of view from the LIF sensor allows a reproduction of the measurement signal. The comparison of measurement and simulation exhibits a high correlation, and thus enables a deeper knowledge and understanding of the real conditions inside a combustion engine. On the other hand, it can be seen that effects such as a decrease in the LIF signal in the cavitation area is much lower than would be expected according to the literature.
Ruch, Fabian H., Wachtmeister, Georg
Further Experiments on the Effect of Bulk In-Cylinder Temperature in the Pressurized Motoring Setup Using Argon Mixtures2020-01-10634/14/2020
Mechanical friction and heat transfer in internal combustion engines have long been studied through both experimental and numerical simulation. This publication presents a continuation study on a Pressurized Motoring setup, which was presented in SAE paper 2018-01-0121 and found to offer robust measurements at relatively low investment and running cost. Apart from the limitation that the peak in-cylinder pressure occurs around 1 DegCA BTDC, the pressurized motoring method is often criticized on the fact that the gas temperatures in motoring are much lower than that in fired engines, hence might reflect in a different FMEP measurement. In the work presented in SAE paper 2019-01-0930, Argon was used as the pressurization gas due to its high ratio of specific heats. This allowed to achieve higher peak in-cylinder temperatures which close further the gap between fired and motored mechanical friction tests. In 2019-24-0141, Argon was mixed in different proportions with Air to synthesize gases with different ratios of specific heats in the aim of observing any abrupt transitions in the FMEP with different peak in-cylinder temperatures. In this publication, a higher loading test matrix to that published in 2019-24-0141 is presented, with an engine speed ranging from 1400 rpm to 3000 rpm and ratios of specific heats varying from that of Air (γ = 1.4) to that of Argon (γ = 1.67). The peak in-cylinder pressure was kept at a constant 103 bar. Results obtained in this work strengthen further the observations made in 2019-24-0141; where the measured FMEP is found to be insensitive to the different peak in-cylinder temperatures. In this study, a fast-response thermocouple of the eroding type was also fitted in the combustion chamber and gas-wall interface temperature histories were recorded. The transient heat flux was also computed through a spectral analysis and reported in this publication.
Caruana, Carl, Farrugia, Mario, Sammut, Gilbert, Pipitone, Emiliano
Optical Characterization of the Combustion Process inside a Large-Bore Dual-Fuel Two-Stroke Marine Engine by Using Multiple High-Speed Cameras2020-01-07884/14/2020
Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas, is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour, properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine, with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine, with fuel injection from positions at the rim of the cylinder, the flame morphology becomes asymmetric. The optical spatial mapping and tracking method is demonstrated to be well suited for the study of such an asymmetric combustion system. Spatial mapping and tracking of flame position is applied to both engine operating modes; normal diesel operation and dual-fuel operation with diesel pilot ignition of the gas. Similarities and differences between diesel and gas flame shape and development can thus be visualised directly. The effects of changing charge density, gas injection pressure and injection nozzle geometry on the flame geometry and development are also studied.
Hult, Johan, Matamis, Alexios, Baudoin, Eric, Mayer, Stefan, Richter, Mattias
Impact of Spark Plasma Length on Flame Kernel Development under Flow Condition2020-01-11144/14/2020
Advanced ignition systems with enhanced discharge current have been extensively investigated in research, since they are highly regarded as having the potential to overcome challenges that arise when spark-ignition engines are running under lean or EGR diluted conditions. Local flow field is also of particular importance to improve the ignitability of the air-fuel mixture in SI engines as the spark plasma channel can be stretched by the flow across the spark gap, leading to longer plasma length, thus more thermal spark energy distributed to the air-fuel mixture in the vicinity of the spark plug. Research results have shown that a constantly high discharge current is effective to maintain a stable spark plasma channel with less restrikes and longer plasma holding period. However, with the further increase in discharge current, plasma channel becomes thicker, and the stretched plasma length becomes shorter under a constant flow speed, which may suppress the advantages of the enhanced discharge current. In this work, the interaction between discharge current level and plasma length under flow conditions is investigated. Whether a thick but shorter plasma channel or a thin but stretched farther plasma channel is more effective for the flame kernel formation is discussed to provide an insight into the influence of the plasma length on flame initiation. An optical combustion chamber platform along with a cross-flow generation system was used to study the plasma channel behavior; an in-house developed spark energy management module was employed to boost the discharge current level up to 3 A; in order to decouple the effect of discharge duration on flame initiation, the total discharge process was controlled within 0.8 ms.
Zhu, Hua, Tan, Qingyuan, Yu, Xiao, Yang, Zhenyi, Liang, Li, Zheng, Ming, Reader, Graham, Qian, Jin
The Effects of Thick Thermal Barrier Coatings on Low-Temperature Combustion2020-01-02754/14/2020
An experimental study was conducted on a Ricardo Hydra single-cylinder light-duty diesel research engine. Start of Injection (SOI) timing sweeps from -350 deg aTDC to -210 deg aTDC were performed on a total number of five pistons including two baseline metal pistons and three coated pistons to investigate the effects of thick thermal barrier coatings (TBCs) on the efficiency and emissions of low-temperature combustion (LTC). A fuel with a high latent heat of vaporization, wet ethanol, was chosen to eliminate the undesired effects of thick TBCs on volumetric efficiency. Additionally, the higher surface temperatures of the TBCs can be used to help vaporize the high heat of vaporization fuel and avoid excessive wall wetting. A specialized injector with a 60° included angle was used to target the fuel spray at the surface of the coated piston. Throughout the experiments, the equivalence ratio, ϕ, was maintained constant at 0.4; the combustion phasing was consistently matched at 6.8 ± 0.4 deg aTDC. It can be concluded that the thick TBC cases achieved 1 to 2 percentage points improvement in combustion efficiency, and generally, a ~2 percentage points increase in indicated engine efficiency. It is also noticed that applying a dense top sealing layer to the TBC further improves the UHC emissions compared to the TBC coated piston with an unsealed surface. From the heat release analysis, it can be concluded that the TBCs have no significant impact on the heat release process and knock intensity while matching the combustion phasing; however, it reduces the intake temperature requirement by up to 20 K. The exhaust gas temperatures were expected to increase for the TBC cases, but the expected increase in exhaust temperature was not conclusive from the results observed in this study.
Yan, Ziming, Gainey, Brian, Gohn, James, Hariharan, Deivanayagam, Saputo, John, Schmidt, Carl, Caliari, Felipe, Sampath, Sanjay, Lawler, Benjamin
An Analytical Approach for Calculating Instantaneous Multilayer-Coated Wall Surface Temperature in an Engine2020-01-01604/14/2020
Thermal swing coatings that have low volumetric heat capacity and low thermal conductivity are attractive because they have the potential to significantly reduce heat transfer to the combustion chamber walls. This paper presents an analytical method for determining the exact solution of the time-resolved wall temperature during the engine cycle for any number of coating layers and properties using the Laplace transformed heat diffusion equation. The method relies only on material properties and the past heat flux history, and represents the exact solution of the heat diffusion equation. The analytical nature of the solution enables fast computation and, therefore, application to system-level optimization calculations. The model relies on an assumption of one-dimensional heat flow, and constant material properties. The major advantage of this approach compared to the standard finite difference approach, wherein the wall is finely discretized, is that there is no approximation and the accuracy is guaranteed, i.e., it does not depend on nodal density. Results are presented for both a quasi-steady operating condition and for an engine transient event. In the latter case a 200-fold reduction in computation time relative to a finite difference code was realized.
Koutsakis, G., Ghandhi, J.B.
A Study of Wear Mechanism on Upper Surface of Piston Top Ring Groove2020-01-13374/14/2020
During engine durability tests (peak power, constant engine speed) conducted in the development process, it has been the case that excessive wear has occurred to the upper surfaces of the piston top ring grooves, despite the fact that contact pressure due to combustion pressure has been low. This has resulted in considerable increases in development man-hours. The research discussed in this paper therefore set out to conduct a factor analysis of wear on the upper surfaces of piston top ring grooves in order to elucidate the wear mechanism in petrol engine for passenger car. This paper will discuss the test method employed in the factor analysis and the mechanism of wear demonstrated by the analysis. First, the form of the wear was analyzed, and rig test methods able to reproduce wear were developed. With regard to the form of wear, both sliding and impact modes were observed. Sensitivity analyses for each form of wear were conducted using rig tests. Quality engineering was employed in the tests, and sensitivity was analyzed based on the design of experimental method. Following this, an engine motoring test method was developed that was closer to the operating state of an actual engine, and that allowed tests to be simply conducted. This motoring test was able to reproduce a compound form of wear produced by sliding and impact, equivalent to that observed in an actual engine, and verified the accuracy of the factor sensitivity demonstrated in the rig tests. In addition, the motoring test was able to reproduce asymmetrical wear in the direction of the circumference of the grooves, which could not be reproduced in the rig test, and made it possible to elucidate the causes of this wear. Finally, an actual engine test was conducted combining the highest and lowest of the determined sensitivities, confirming the validity of the identified wear factors.
Sato, Kenji, Takahashi, Katsuyuki, Wakabayashi, Ryo, Yoshii, Kenta, Takahashi, Shinichi
Piston Bowl Design Optimization to Improve Low End Rated Torque in BS-VI Diesel Engine Based on Multi-Dimensional Combustion Simulation2020-01-02414/14/2020
In cylinder combustion and emission characteristics are dependent on piston bowl geometry design. In-cylinder fuel air mixing and flame front movement are influenced by piston bowl shape and design. These phenomena in turns affect the combustion behavior and the power developed by the diesel engine. In this study piston bowl geometry optimization of a LMD diesel engine is carried out to improve the torque and BSFC output at low end rated operating zones. The optimized bowl geometry is also incorporated in the engine and validated on the test bed. In this work, a commercially available CFD code AVL FIRE is used for combustion simulation and bowl geometry optimization. The validation of in-cylinder combustion simulation of a 2 liter Turbocharged LMD BS-VI diesel engine with base piston bowl geometry is carried out with the available test data. The validation of combustion simulation is performed for four engine operating speed points covering rated torque to rated power operating condition. Four key piston bowl geometry parameters were selected for the optimization study with the objective to improve the torque output at rated torque operation. Two bowl geometries from the optimization study were selected for further analysis at remaining engine operating points. Both the bowl geometries showed improvement in torque and BSFC at all the simulated operating zones. Based on the design feasibility one of the bowl geometry was selected for validation on physical engine. The results from test bed showed the optimized geometry gave torque improvement as predicted by the combustion simulation.
Appukuttan, Anish, Bisht, Jasvir, Kaundabalaraman, Kaarthic, Rathi, Hemantkumar
Experimental and Numerical Analysis of Passive Pre-Chamber Ignition with EGR and Air Dilution for Future Generation Passenger Car Engines2020-01-02384/14/2020
Nowadays the combination of strict regulations for pollutant and CO2 emissions, together with the irruption of electric vehicles in the automotive market, is arising many concerns for internal combustion engine community. For this purpose, many research efforts are being devoted to the development of a new generation of high-performance spark-ignition (SI) engines for passenger car applications. Particularly, the PC ignition concept, also known as Turbulent Jet Ignition (TJI), is the focus of several investigations for its benefits in terms of engine thermal efficiency. The passive or un-scavenged version of this ignition strategy does not require an auxiliary fuel supply inside the PC; therefore, it becomes a promising solution for passenger car applications as packaging and installation are simple and straightforward. Moreover, combining this concept with lean burn is an interesting alternative for both improving the engine efficiency and maintaining low pollutant emissions as it enables Low Temperature Combustion (LTC) which ultimately reduces NOX emissions. EGR dilution is also an attractive approach as it is compatible with the three-way catalyst for NOX control. However, previous researches focused on developing the technology rather than understanding the governing physical phenomena. Consequently, the knowledge about the characteristics and limitations of the combustion process for this ignition concept is still limited. For this purpose, an experimental campaign combined with a computational study was performed in this research work to analyze the TJI combustion features in a turbocharged passenger car-size single-cylinder SI engine, sweeping EGR and λ levels. Single-cycle RANS simulations were carried out following a suitable methodology and the results were validated against experimental data keeping the same engine configuration and operating conditions. The simulation results were used to study in detail the combustion process and jet characteristics. The analysis of the results provided a detailed insight about the key aspects limiting the passive PC ignition concept compatibility with air/EGR dilution.
Novella, Ricardo, Pastor, Jose, Gomez-Soriano, Josep, Barbery, Ibrahim, Libert, Cedric, Rampanarivo, Fano, Panagiotis, Chistou, Dabiri, Maziar
Temperature Measurement, Well Insert TypeARP175A (Current)4/14/2020
A-4 Aircraft Instruments Committee
Measurement of Fuel Distribution in a Small PFI Spark-Ignition Engine Using Tracer PLIF2020-01-07864/14/2020
The distribution of fuel-air mixture inside the engine cylinder strongly influences the combustion process. Planar laser-induced fluorescence (PLIF) is commonly used for fuel distribution measurement, however, it is mostly reported on moderate- to large-sized engines. In the present work, PLIF is applied to measure the fuel distribution inside the cylinder of a small, four-stroke, port-fuel-injection (PFI), spark-ignition engine with displacement volume of 110 cm3. Iso-octane was used as the base fuel, and 3-pentanone (15% by volume) was added as a fluorescent tracer in the base fuel. The effect of equivalence ratio, considering ϕ = 1.2, 1.0, and 0.8, on in-cylinder fuel distribution was studied with low throttle opening of 25% at 1200 rpm. PLIF images were recorded at different crank angle degrees during both intake and compression strokes over a swirl measurement plane located at the TDC position. It was found that the fuel stratification was present from intake to even late compression. Also, no significant change in fuel distribution patterns was noted at different crank angle degrees for a given operating condition. Instantaneous PLIF images of the fuel distribution at 330 CAD during compression also showed a considerable variation from one cycle to the next. As expected, the fluorescence signal intensity was increased with the increase in equivalence ratio. Results also showed that the fuel distribution was much more noticeable near the diametrically opposite location to the spark plug on the tested engine, and continued to exist till late compression (i.e. 330 CAD).
Garg, Shubham, Mittal, Mayank, Sahu, Srikrishna, Lakshminarasimhan, V
Transition from HCCI to PPC: Investigation of the Effect of Different Injection Timing on Ignition and Combustion Characteristics in an Optical PPC Engine2020-01-05594/14/2020
The partially premixed combustion (PPC) concept is regarded as an intermediate process between the thoroughly mixed Homogeneous charge compression ignition (HCCI) combustion and compression ignition (CI) combustion. It’s a combination of auto-ignition mode, a fuel-rich premixed combustion mode, and a diffusion combustion mode. The concept has both high efficiency and low soot emission due to low heat losses and less stratified fuel and air mixtures compared to conventional diesel CI. The mechanisms behind the combustion process are not yet very well known. This work focuses on the efficiency and the in-cylinder process in terms of fuel distribution and the initial phase of the combustion. More specifically, double injection strategies are compared with single injection strategies to achieve different levels of stratification, ranging from HCCI to PPC like combustion as well as poor (43%) to good (49%) of gross indicated efficiency. The experiments were performed in an optical heavy-duty CI engine. To analyze how the efficiency was affected in a transition from HCCI to PPC, the natural luminosity (N.L.) was captured with high-speed video (HSV). To complement the HSV data, fuel, temperature, and oxygen distribution were explored by Computational fluid dynamics (CFD) simulation. The results show that the jet-jet and jet-piston interactions can be modified and can reshape the transition trends of gross indicated efficiency and ignition location compared to a single injection. In the transition region, these interactions can improve the efficiency by shaping the fuel-rich region away from cold areas, like the vertical wall of the piston and the squish region, to avoid fuel wetting and incomplete combustion. However, with double injections in the piston bowl (PPC region), jet-jet interaction can unfortunately inhibit the mixing process of the second fuel jet and oxygen due to interaction with the fuel rich region from the first injection, ending up with a lower combustion efficiency.
Zhang, Miao, Derafshzan, Saeed, Xu, Leilei, Bai, Xue-Song, Richter, Mattias, Lundgren, Marcus
Effect of Homogenous-Stratified Mixture Combustion on Performance and Emission Characteristics of a Spray-Guided GDI Engine - A CFD Study2020-01-07854/14/2020
Today, gasoline direct injection (GDI) engine is one of the best strategies to meet the requirement of low pollutant emissions and fuel consumption. Generally, the GDI engine operates in stratified mixture mode at part-load conditions and homogeneous mixture mode at full-load conditions. But, at part-loads, soot emissions are found to be high because of improper air-fuel mixing. To overcome the above issue, a homogenous-stratified mixture (a combination of the overall homogeneous lean mixture with a combustible mixture at the location of the spark plug) is found to be better to reduce soot emissions compared to a stratified mixture mode. It will also help reduce fuel consumption. In this study, the analysis has been done to evaluate the effect of homogeneous-stratified mixture combustion on the performance and emission characteristics of a spray-guided GDI engine under various conditions using computational fluid dynamics (CFD). Here, for the analysis, overall equivalence ratios of 0.5 to 0.8 are considered. The constant engine speed of 2000 rev/min. and fuel injection pressure of 200 bar is used. Two direct fuel injections (the first in the suction stroke and the second in the compression stroke) are used to get the homogeneous-stratified mixture. The split ratios used among the two injections of 20:80, 30:70, 40:60, and 50:50 are tried. The comparisons of combustion, performance and emission characteristics at various split ratios are done with that of the single injection case using the stratified mixture. It is found that with split injection, homogenous-stratified mixture formation is very effective with a higher equivalence ratio and higher quantity of fuel in the first injection. In the above conditions, the in-cylinder pressures are comparable to that of the single injection case. Also, soot emissions are lower by about 95-99% compared to that of the single injection case. Also, with lower equivalence ratio and higher quantity of fuel in the first injection, NOx emissions are lower by about 15% compared to that of the single injection, whereas HC emissions are higher.
Kumar, Rahul, Mallikarjuna, J M
Functionality Analysis of Thermoplastic Composite Material to Design Engine Components2020-01-07744/14/2020
Developing of innovative technologies and materials to meet the requirements of environmental legislation on vehicle emissions has paramount importance for researchers and industries. Therefore, improvement of engine efficiency and fuel saving of modern internal combustion engines (ICEs) is one of the key factors, together with the weight reduction. Thermoplastic composite materials might be one of the alternative materials to be employed to produce engine components to achieve these goals as their properties can be engineered to meet application requirements. Unidirectional carbon fiber reinforced PolyEtherImide (CF/PEI) thermoplastic composite is used to design engine connecting rod and wrist pin, applying commercial engine data and geometries. The current study is focused on some elements of the crank mechanism as the weight reduction of these elements affects not only the curb weight of the engine but the overall structure. As a matter of fact, by reducing the reciprocating mass, alternate forces will be reduced and hence the size of the structural elements. Also, other elements of the engine can be designed for lightweighting, but the crank mechanism elements maximize the effects, by reducing both loads and weight. Finite element analysis (FEM) has been conducted for proper stress analysis and accordingly examine the design and parts functionalities. FEM analysis is performed using Altair HyperMesh for mesh optimization to conduct stress analysis of standard engine components made of steel and to redesign the parts using thermoplastic material to sustain the loads and stresses. Then the design modification has been considered to reduce loads and weight without parts performance interruption under service.
Razavykia, Abbas, Delprete, Cristiana, Rosso, Carlo, Baldissera, Paolo
Strategies to Gain the Loss in Power in a Military Diesel Engine Using JP-8 Instead of ULSD2020-01-08044/14/2020
The Department of Defense (DOD) has adopted the use of JP-8 under the “single battlefield fuel” policy. Fuel properties of JP-8 which are different from ULSD include cetane number, density, heating value and compressibility (Bulk modulus). While JP8 has advantages compared to ULSD, related to storage, combustion and lower soot emissions, its use cause a drop in the peak power in some military diesel engines. The engines that has loss in power use the Hydraulically actuated Electronic Unit Injection (HEUI) fuel system. The paper explains in details the operation of HEUI including fuel delivery into the injector and its compression to the high injection pressure before its delivery in the combustion chamber. The effect of fuel compressibility on the volume of the fuel that is injected into the combustion chamber is explained in details. A fuel such as JP-8 which has a lower Bulk modulus is compressed to a smaller volume than ULSD which has a higher Bulk modulus before its delivery in the combustion chamber, and this is the main reason for the drop in power explained earlier. Experiments conducted on a CAT C7 engine demonstrated the loss in peak power associated with JP-8 over the whole speed range. Different approaches in the injection process have been discussed to gain the loss in peak power.
Raut, Prasad D., Atre, Omkar A., Trivedi, Manan, Henein, Naeim
The Isochoric Engine2020-01-07964/14/2020
For the gasoline engine, the isochoric process is the ideal limit of the ideal processes. During the project, a combustion engine with real isochoric boundary conditions is built. A “resting time” of the piston for several degrees crank angle in the top dead center (TDC) can be realized with a special crank drive. This crank drive consists of two crankshafts with different strokes, which are combined. The two crankshafts rotate with a ratio of two to one in opposite directions. The total stroke corresponds to the amount of the first crankshaft, so it is possible to investigate different strokes of the second crankshaft in the same crankcase. Different “resting times” can be achieved by different strokes of the second crankshaft. A specific combination of both crankshafts make a stroke possible which corresponds to that of a conventional combustion engine. In addition to the standard cylinder pressure sensor, a quick surface temperature probe is also used as supplementary measurement technology. The influence of isochoric combustion is studied with constant air mass and constant lambda at three different strokes of the small crankshaft.
Burger, Benjamin, Bargende, Michael
Smart Spark Plug for Proper Combustion Timing in Gasoline Engines and Detection of Misfire and Knock2020-01-07904/14/2020
Internal combustion engines are required to achieve production goals of better fuel economy, improved fuel economy and reduced emissions in order to meet the current and future stringent standards. To achieve these goals, it is essential to control the combustion process using an in-cylinder combustion sensor and a system that produces a feedback signal to the ECU. This paper presents a system based on combustion ionization that includes a newly developed smart spark plug capable of sensing the whole combustion process. A unique feature of the smart spark plug system is its ability to sense the early stages of combustion and produce a complete ion current signal that accurately identifies and can be used for the control of the start of combustion. This is not the case for the conventional spark plug where the start of combustion cannot be determined from the ion current signal because its early part is distorted or completely overshadowed by the strong electromagnetic field produced by the spark ignition system. In addition to its ability to detect and control the start of combustion, the new system can detect other combustion related problems such as misfire and knock. The paper describes the construction of the smart spark plug and compares its ion current signal with that produced by the conventional spark plug. The new system, developed and patented by IC LLC, can be applied in current production spark ignition engines as well as for the development of future advanced concepts engines.
Assaad, Kamal, Henein, Naeim A.
Improving Heavy Duty Natural Gas Engine Efficiency: A Systematic Approach to Application of Dedicated EGR2020-01-08184/14/2020
The worldwide trend of tightening CO2 emissions standards and desire for near zero emissions is driving development of high efficiency natural gas engines for a low CO2 replacement of traditional diesel engines. A Cummins Westport ISX12 G was previously converted to a Dedicated EGR® (D-EGR®) configuration with two out of the six cylinders acting as the EGR producing cylinders. Using a systems approach, the combustion and turbocharging systems were optimized for improved efficiency while maintaining the potential for achieving 0.02 g/bhp-hr NOX standards. A prototype variable nozzle turbocharger was selected to maintain the stock torque curve. The EGR delivery method enabled a reduction in pre-turbine pressure as the turbine was not required to be undersized to drive EGR. A high energy Dual Coil Offset (DCO®) ignition system was utilized to maintain stable combustion with increased EGR rates. High compression ratio, reduced squish pistons were designed to maintain MBT combustion phasing and fast burn rates along the torque curve. The final engine configuration was tested on the Heavy-Duty Supplemental Emissions Test (SET), a 13-mode steady-state engine dynamometer test. The engine was able to achieve a weighted average efficiency improvement of 12% over the baseline configuration with a peak BTE of 41.7%.
Kocsis, Michael C., Mitchell, Robert, Moiz, Ahmed Abdul, Kalaskar, Vickey, Williams, D. Ryan, Sjovall, Scott
Combustion System Development in GAC Turbocharged Miller GDI Engine with 0.5L/Cylinder2020-01-08384/14/2020
GAC Group has set up two modular engine families, G and GS, for various vehicle classes equipping demands. G family engines, which have already gone through three generations, target for the higher torque and power, the lower fuel consumption and the future strict emission standards. For the latest generation, new technologies were added to achieve the development goals based on the previous modular engines. For example, miller combustion cycle with increased compression ratio is introduced in the newer engine combustion system. Additional key technologies such as 350 bar injection system and high tumble intake ports are also applied. The combustion system development, which established on the GAC Combustion Controlling System (GCCS), was facilitated by integrated use of advanced optical measurements and computational fluid dynamics for improving the in-cylinder flow, fuel sprays and the interaction between them. This paper presents the analytical work done to develop the combustion systems. A higher tumble intake port design enhances the motion in intake process, the well-organized in-cylinder flow may bend over the sprays and keep them from interacting with the cylinder. The redesigned spray structure and piston bowl could do good for a reasonable mixture formation, which decreases the soot and HC emissions, especially for the cold-start conditions. Results from engine test bench experiments show that all of the new generation of the 0.5L/cylinder turbocharged DI gasoline engines can meet the strict legislation for nearest or some considerable time to come.
Li, Yuhuai, Chen, Hong, Du, Jiakun, Wu, Jian, Zhan, Wenfeng, Wu, Guangquan, Lin, Sicong, Shao, Fake
Discharge Current Management for Diluted Combustion under Forced Flow Conditions2020-01-11184/14/2020
Lean burn or EGR diluted combustion with enhanced charge motion is effective in improving the efficiency of spark ignition engines. However, the ignition process under these conditions is getting more challenging due to higher ignition energy required by the lean or diluted mixture, as well as the interactions of the gas flow on the flame kernel. Enhanced spark discharge energy is essential to initiate the combustion under these conditions. Moreover, the discharge process should be more carefully controlled to improve the effectiveness of the spark. In this study, spark ignition systems with boosted discharge energy are used to ignite diluted air-fuel mixture under forced flow conditions. The impacts of the discharge current level, the discharge duration and the discharge current profile on the ignition are investigated in detail using optical diagnosis. It is evident from the results that extended discharge duration helps promote the flame propagation, though the effectiveness is limited when the duration exceeds the required minimum value for a self-sustained flame kernel. A higher discharge current level is favorable for generating a stronger flame kernel. With similar discharge energy delivered to the spark gap, a high-current spark with a shorter duration performs better than a longer duration low-current spark. Then the impacts of discharge current profiles are studied. Three spark discharge strategies, including a low-current continuous discharge, a high-current multi-pulse discharge, and a very high transient current discharge, are used in the comparison. The results reveal that sufficiently long discharge duration is critical for success ignition under the tested flow condition. Among the three ignition strategies, the low-current continuous spark discharge performs the best, even with the lowest discharge energy, due mainly to the continuous nature of the spark discharge.
Yang, Zhenyi, Wang, Linyan, Sandhu, Navjot S., Yu, Xiao, Zheng, Ming
Experimental Investigation of the Influence of Ignition System Parameters on Combustion in a Rapid Compression-Expansion Machine2020-01-11224/14/2020
Lean burn combustion concepts with high mean effective pressures are being pursued for large gas engines in order to meet future stringent emission limits while maintaining high engine efficiencies. Since severe boundary conditions for the ignition process are encountered with these combustion concepts, the processes of spark ignition and flame initiation are important topics of applied research, which aims to avoid misfiring and to keep cycle-to-cycle combustion variability within reasonable limits. This paper focuses on the fundamental investigation of early flame kernel development using different ignition system settings. The investigations are carried out on a rapid compression-expansion machine in which the spark ignition process can be observed under engine-like pressure and excess air ratio conditions while low flow velocities are maintained. The schlieren setup for high-speed optical investigations of the area of the spark plug electrodes is described and a suitable post-processing routine is introduced. The influence of different spark current durations on early flame kernel formation is investigated using a modulated capacitive discharge ignition (MCDI) system. The outcomes reveal that a short spark current duration results in a slower increase and higher standard deviation of the flame area during the early phase of combustion. Moreover, stable flame initiation appears to require a minimum spark current duration. The methodology introduced in this paper will be applied in detailed investigations of other spark plug geometries and ignition settings in order to shed more light on the ignition of lean mixtures.
Kiesling, Constantin, Pirker, Gerhard, Tilz, Anton, Oppl, Thomas, Nickl, Andreas, Wimmer, Andreas, Meyer, Georg
Optical Diagnostics of Isooctane and n-Heptane Isobaric Combustion2020-01-11264/14/2020
Isobaric combustion has demonstrated a great potential to reach high thermodynamic efficiency in the advanced Double Compression Expansion Engine (DCEE) concept. It appears as one of few viable choices for applications with high-pressure combustion. At these conditions, releasing heat at a constant pressure minimizes the peak in-cylinder pressure and, hence, mitigates excessive mechanical stress on the engine. This study focuses on the effect of fuels on the multiple-injection isobaric combustion. A single-cylinder heavy-duty engine was utilized to test and compare the isobaric combustion with pure isooctane and n-heptane fuels. The engine was equipped with an optical piston to allow a bottom-view of the combustion chamber. The interactions of multiple injections and the combustion behavior were studied using high-speed acquisition of chemiluminescence. The examined isobaric cases have a peak pressure of 70 bar. For cases with high soot luminosity, a short band-pass filter was used to avoid image saturation. Fuels with short ignition delay time such as n-heptane are usually used for isobaric applications as they offer good controllability of injections. However, the study herein demonstrates that isobaric combustion can be achieved even with high octane number fuels such as isooctane. The dwell time between injections is much larger for isooctane, which allows enhanced mixing of the fuel jets with air and thus a partially premixed combustion behavior. The high-speed imaging demonstrated evidence of flame extinguishing during the sequential injection of n-heptane. This contributes to the staging of the heat release rate.
Al Ramadan, Abdullah S., Nyrenstedt, Gustav, Ben Houidi, Moez, Johansson, Bengt
Impact of Multiple Injection Strategies on Efficiency and Combustion Characteristics in an Optical PPC Engine2020-01-11314/14/2020
Partially premixed combustion (PPC) is a promising way to achieve high thermal efficiency and low emissions, especially by using multiple injection strategies. The mechanisms behind PPC efficiency are still to be explained and explored. In this paper, multiple injections have been used to affect the gross indicated efficiency in an optical PPC engine modified from a Volvo MD13 heavy-duty diesel engine. The aim is both to improve and impair the gross indicated efficiency to understand the differences. The combustion natural luminosity is captured by a high-speed camera, and the distribution of fuel, oxygen, and temperature during the combustion process has been further explored by CFD simulation. The results show that with the right combination of the pilot, main, and post injection the gross indicated efficiency can be improved. Using a post injection in a triple-injection case show to have less effect on the combustion phasing than pilot injection in a double-injection case, while it can significantly affect combustion efficiency. The later of the double-injection cases tested (c30/16), has less heat transfer losses since the high-temperature region transported away from the cylinder head and piston bowl wall, which can be seen in the CFD-simulations. The highest gross indicated efficiency among the tested cases is given by the triple-injection case d38/24/6 as it reaches the best balance between the mixing and the local temperature through the jet-jet interactions and combustion-jet interactions.
Zhang, Miao, Xu, Leilei, Derafshzan, Saeed, Bai, Xue-Song, Richter, Mattias, Lundgren, Marcus
Effects of Direct Injection Timing and Air Dilution on the Combustion and Emissions Characteristics of Stratified Flame Ignited (SFI) Hybrid Combustion in a 4-Stroke PFI/DI Gasoline Engine2020-01-11394/14/2020
Controlled Auto-Ignition (CAI) combustion can effectively improve the thermal efficiency of conventional spark ignition (SI) gasoline engines, due to shortened combustion processes caused by multi-point auto-ignition. However, its commercial application is limited by the difficulties in controlling ignition timing and violent heat release process at high loads. Stratified flame ignited (SFI) hybrid combustion, a concept in which rich mixture around spark plug is consumed by flame propagation after spark ignition and the unburned lean mixture closing to cylinder wall auto-ignites in the increasing in-cylinder temperature during flame propagation, was proposed to overcome these challenges. The combustion and emissions characteristics in the SFI hybrid combustion were experimentally investigated in a single-cylinder 4-stroke gasoline engine operating at medium to high loads when direct injection timing was retarded from -100 °CA to -40 °CA after top dead center (ATDC) and excess air coefficient was increased from 1.0 to 1.2 at the direct injection ratio of 30%. The experimental results show that direct injection timing and excess air coefficient control the ignition timing and combustion duration. Ignition timing advances with increased excess air coefficient at the same direct injection timing. Long combustion duration occurs at earlier direct injection timing close to -100 °CA ATDC or very late direct injection timing near -40 °CA ATDC at different excess air coefficients. In the meantime, combustion duration reduces with increased excess air coefficient when auto-ignition occurs during the combustion processes, while it increases with excess air coefficient without auto-ignition. Nitrogen oxides emissions increase first and then decrease with retarded direct injection timing at different excess air coefficients, and their maximum values occur at the direct injection timing of -60°CA ATDC.
Fu, Xue-Qing, He, Bang-Quan, Li, Hongtao, Chen, Tao, Zhao, Hua, Yang, Jian-Jun, Liu, Shuang-Xi, Gao, Haiyang
Experimental Study on the Characteristics of Short Circuits and Restrikes of Spark Channels2020-01-11234/14/2020
Ignition performance is critical for the implementation of diluted combustion for spark-ignition engines. The short circuit and restrike phenomena can influence the initial ignition volume and discharge duration which are important for the stable ignition processes. In this study, the short circuits and restrikes of spark channels are studied with various flow velocities, spark plug gaps and discharge energies. The development of the spark channels is captured by using the direct imaging technique with a CMOS camera equipped with an image intensifier. A multi-coil ignition system is designed to enable flexible control of discharge energies. The results show that the spark plug gap size is a critical parameter to suppress the phenomena of short circuits and restrikes. With the enlargement of spark plug gap, the maximum and average lengths of the spark channel effectively increase. Meanwhile, increasing discharge power is another effective method to improve the short circuit and restrike phenomena. However, for the discharge strategy of single strike, further increasing the discharge power cannot improve the restrike phenomena. The spark channel growth rate has no correlation with the spark plug gap and the discharge energy, but linearly relating to the flow velocity around the spark plug gap. An enhanced flow velocity increases the events of short circuit and restrike. The restrike voltage increases with decrease of the discharge current or increase of the flow velocity, while, the restrike voltage is lower than the breakdown voltage of the spark onset from the same discharge process. Finally, a new spark plug prototype is given to suppress the short circuit and enhance the spark plasma channel under high-velocity flow conditions.
Huang, Shuai, Li, Tie, Wang, Ning, Wang, Xinran, Yang, Zhenyi, Yu, Xiao, Zheng, Ming
Investigation of the Impacts of Spark Plug Orientation on Combustion Stability under Lean SI Operation2020-01-11214/14/2020
The increasingly stringent restrictions on vehicle emissions and fuel consumption are driving the development of gasoline engines towards lean combustion. Increasing ignition energy has been considered an effective way to achieve lean operation conditions. To further improve the lean limit of engine combustion, the influence of the spark plug orientation on the combustion stability under lean operation should be explored. In this investigation, the original machine spark plug orientation, 90 degrees clockwise rotation, and 180 degrees clockwise rotation are studied to analyze the impact of spark plug orientation. The combustion experiment was carried out under the condition of low excess air ratio of the original machine and high excess air ratio with a 450 mA high energy ignition. It is found that changing the orientation of the spark plug had little effect on combustion at low excess air ratio; however, under high excess air ratio (ultra-lean operation), spark plug orientation had a great influence on combustion stability. The combustion stability can be significantly improved when the spark plug orientation is vertical to the intake direction. What’s more, we found that when the engine speed was low as 1000rpm, the effects of the spark plug orientation were not very clear. However, when the engine speed increased to 2000rpm, the lean operation limit can be improved from an excess air ratio of 1.78 to 1.96 by adjusting the orientation of the spark plug.
Gu, Qifan, Xu, Min, Ye, Chang, Hung, David, Li, Xuesong
Varying Intake Stroke Injection Timing of Wet Ethanol in LTC2020-01-02374/14/2020
Computational Fluid Dynamics (CFD) modeling was used to investigate the effects of the direct injection of wet ethanol at various injection timings during the intake stroke in a diesel engine with a shallow bowl piston. Thermally Stratified Compression Ignition (TSCI) has been proposed to expand the operating range of Low Temperature Combustion (LTC) by broadening the temperature distribution in the cylinder prior to ignition. TSCI is accomplished by injecting either water or a water-fuel mixture with a high latent heat of vaporization like wet ethanol. This current study focuses on isolating the effects that injecting such a high heat of vaporization mixture during the intake stroke has on the distribution of temperature and equivalence ratio in the cylinder before the onset of combustion. A CONVERGE 3-D CFD model of a single cylinder diesel research engine using Reynolds Averaged Naiver Stokes (RANS) turbulence modeling was developed and validated against experimental data. Then, five cases of injection timing with an injector included angle of 60° were simulated from -330 CAD to -210 CAD BTDC in increments of 30 CAD and five cases with an injector included angle of 150° were simulated from -330 CAD to -240 CAD BTDC also in increments of 30 CAD with an additional case at -340 CAD BTDC. For each spray case, the temperature and equivalence ratio stratification in the cylinder 10 CAD before TDC were analyzed using joint probability density functions (jPDFs). Results show that a later injection timing yields a more stratified mixture as well as a stronger inverse relationship between local temperature and equivalence ratio. An injection of wet ethanol at specific timings also causes the fuel to experience different mixing profiles due to the injector included angle and the piston position at each injection timing. Wall wetting on the piston was another area explored under varying spray conditions due to the high heat of vaporization of the fuel mixture.
O'Donnell, Patrick C., Rahimi Boldaji, Mozhgan, Gainey, Brian, Lawler, Benjamin
Influence of Port Water Injection on the Combustion Characteristics and Exhaust Emissions in a Spark-Ignition Direct-Injection Engine2020-01-02944/14/2020
It is well known that engine downsizing is still the main energy-saving technology for spark-ignition direct-injection (SIDI) engine. However, with the continuous increase of the boosting ratio, the gasoline engine is often accompanied by the occurrence of knocking, which has the drawback to run the engine at retarded combustion phasing. Besides, in order to protect the turbine blades from being sintered by high exhaust temperature, the strategies of fuel enrichment are often taken to reduce the combustion temperature, which ultimately leads to a high level of particulate number emission. Therefore, to address the issues discussed above, the port water injection (PWI) techniques on a 1.2-L turbocharged, three-cylinder, SIDI engine were investigated. Measurements indicate that the optimization of spark timing has a significant impact on its performance. The two factors of the water substance itself and spark advance caused by the knock mitigation are trade-offs, which eventually affect the combustion performance. Under knock limited spark advance (KLSA) condition, we find that the application of port water injection could effectively advance the combustion phasing and reduce exhaust gas temperature, which makes it possible to eliminate fuel enrichment and further enhances the fuel economy improvement at the maximum power point. As a result, about 5.2%-18.4% improvements in the fuel economy are obtained under different engine operating conditions. For the exhaust emissions, due to the increasing heat capacity of the mixture and the elimination of fuel enrichment, port water injection techniques cause an 85.3% reduction in particle number concentration. However, it shows that for a given λ, an increase in the water/fuel ratio would cause higher THC emissions, which is contributed to the occurrence of more quenching caused by higher peak combustion pressure. Finally, the potential of PWI on the engine combustion characteristics and emissions performance was revealed.
Fan, Yadong, Wu, Tianbao, Li, Xuesong, Xu, Min, Hung, David
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