Browse Topic: Stratified charge engines

Items (500)

Knock: A Century of Research

7/28/2021

Knock is one of the main limitations on increasing spark-ignition (SI) engine efficiency. This has been known for at least 100 years, and it is still the case today. Knock occurs when conditions ahead of the flame front in an SI engine result in one or more autoignition events in the end gas. The autoignition reaction rate is typically much higher than that of the flame-front propagation. This may lead to the creation of pressure waves in the combustion chamber and, hence, an undesirable noise that gives knock its name. The resulting increased mechanical and thermal loading on engine components may eventually lead to engine failure. Reducing the compression ratio lowers end-gas temperatures and pressures, reducing end-gas reactivity and, hence, mitigating knock. However, this has a detrimental effect on engine efficiency. Automotive companies must significantly reduce their fleet carbon dioxide (CO2) values in the coming years to meet targets resulting from the 2015 Paris Agreement. One path towards meeting these is through partial or full electrification of the powertrain. However, the vast majority of automobiles in the near future will still feature a gasoline-fueled SI engine; hence, improvements in combustion engine efficiency remain fundamental. As knock has been a key limitation for so long, there is a huge amount of literature on the subject. A number of reviews on knock have already been published, including in recent years. These generally concentrate on current understanding and status. The present work, in contrast, aims to track the progress of research on knock from the 1920s right through to the present day. It is hoped that this can be a useful reference for new and existing researchers of the subject and give further weight to occasionally neglected historical activity, which can still provide important insights today.

Corrigan, Daire James, Fontanesi, Stefano

Effect of a Split-Injection Strategy on the Atomisation Rate Using a High Pressure Gasoline DI Injector

2020-01-03224/14/2020

The Gasoline direct-injection (GDI) engine can emit high levels of particulate matter and unburned Hydrocarbons when operating under stratified charge combustion mode. Injecting late in the compression stroke means the fuel has insufficient time to atomise and evaporate. This could cause fuel film accumulation on the piston surface and combustion liner. Locally fuel rich diffusion combustion could also result in the formation of soot particles. Employing a split-injection strategy can help tackle these issues. The first injection is initiated early in the intake stroke and could ensure a global homogeneous charge. The second injection during the compression stroke could help form a fuel-rich charge in the vicinity of the spark plug. Many studies have established the crucial role that a split-injection strategy plays in the stratified charge operation of GDI engines. The current study examines how a split-injection strategy affects the flow field and spray characteristics at high injection pressure. This is done by analysing the global spray structures and the atomisation rates. In particular, the effects of changing dwell times between injections on the spray characteristics of the second injections are evaluated. The experiments were conducted in a constant volume spray chamber. A multi-hole solenoid DI injector, with maximum injection pressure capability of 35MPa, was used to carry out the investigations. The spray characteristics were determined using high-speed imaging. The atomisation rates, breakup processes and droplet sizes were studied using Phase Doppler Particle Anemometry. Short and large pulse widths, in the range of 0.3ms to 0.8ms, were investigated.

Dhanji, Meghnaa Paresh, Zhao, Hua

Investigations on Pre-chamber Ignition Device Using Experimental and Numerical Approaches

2019-01-216312/19/2019

Nowadays Spark Ignition (SI) engine efficiency is mainly limited by abnormal combustion (knock) and stability issues at high dilution rate (both EGR and air). Increasing the combustion velocity is a relevant way to overcome these limitations. Main strategy to increase the combustion velocity is to enhance the flow motion in the cylinder (tumble motion) in order to increase the turbulence during the combustion. Such approach is mainly performed by working on intake port design which lead to engine volumetric efficiency penalties. Another approach to increase the combustion velocities is to have multiple ignition kernels in the chamber. This can be obtained thanks to Turbulent Jet Ignition (TJI) which uses a pre-chamber to spread the initial flame kernel throughout the combustion chamber. To achieve pre-chamber optimization a deep understanding of the complex phenomena involved in TJI as well as validated numerical tools is required. The present paper aims at providing such understanding using both numerical simulations and experimental investigations. First, dedicated experimental methodology is deployed on an optical engine providing a characterization of the flame jets depending on the pre-chamber geometry. Then, the numerical 3D CFD tool is setup to model these experimental configurations and then used to bring additional information on the breathing mechanisms of the pre-chamber. Finally, experiments are conducted on a single cylinder SI engine, replacing the conventional spark plug by a pre-chamber. The contribution of this ignition device to the improvements of engine efficiency is evaluated.

Laget, O., Chevillard, S., Pilla, G., Gautrot, X., Colliou, T.

0D/1D Turbulent Combustion Model Assessment from an Ultra-Lean Spark Ignition Engine

2019-01-14093/25/2019

This paper focuses on an assessment of predictive combustion model using a 0D/1D simulation tool under high load, different excess air ratio λ , and different combustion stabilities (based on coefficient of variation of indicated mean effective pressure COVimep). To consider that, crank angle resolved data of experimental pressure of 500 cycles are recorded under engine speed 1000 RPM and 2000 RPM, wide-open throttle, and λ=1.0, 1.42, 1.7, and 2.0. Firstly, model calibration is conducted using 18 cases at 2000 RPM using 500 cycle-averaged in-cylinder pressure to find optimized model constants. Then, the model constants are unchanged for other cases. Next, different cycle-averaged pressure data are used as inputs in the simulation based on the COVimep for studying sensitivity of the turbulent model constants. The simulation is conducted using 1D simulation software GT-Power. Firstly, a three-pressure analysis (TPA) model (intake, in-cylinder, exhaust) for experimental prediction and optimization of burn rate shape are studied. Boundary conditions such as the three pressure histories, intake/exhaust valves timings, boundary temperatures, and exhaust gas emissions are used as model inputs. Errors of indicated thermal efficiency, indicated mean effective pressure, and CA50 are within 3%. Predicted parameters from the TPA model such as air volumetric efficiency, trapped air/fuel vapor mass, trapped residual gas fraction, tumble, and surface temperature of the piston, head, and valves are used as initializations in the predictive combustion model. A built-in flame propagation model, termed as SITurb, is investigated whether it can replicate the in-cylinder pressure and burn rate shapes. A revised laminar flame speed correlation of five-component gasoline surrogate is incorporated in the combustion model via an encrypted dynamic link library file. The results show that thermodynamic histories of the combustion are reproducible under high load and stoichiometric-to-ultra-lean conditions. Under all cases, only turbulent flame speed multiplier needs to be calibrated.

Sok, Ratnak, Yamaguchi, Kyohei, Kusaka, Jin

Computational Fluid Dynamic Simulation of In-Cylinder Pressures to Validate High-Range VCR

02-11-04-002010/22/2018

This article serves as a proof-of-concept and feasibility analysis regarding a variable compression ratio (VCR) engine design utilizing an exhaust valve opening during the compression stroke to vary the compression ratio instead of the traditional method of changing the cylinder or piston geometry patented by Ford, Mercedes-Benz, Nissan, Peugeot, Gomecsys, et al. [1]. In this concept, an additional exhaust valve opening was used to reduce the virtual compression ratio of the engine, without geometric changes. A computational fluid dynamics model in ANSYS Forte was used to simulate a single-cylinder, cold flow, four-stroke, direct injection engine cycle. In this model, the engine was simulated at a compression ratio of 10:1. Then, the model was modified to a compression ratio of 17:1. Then, an additional valve opening at the end of the compression stroke was added to the 17:1 high compression model. The valve opening at the end of the compression stroke was used to bleed off a small amount of pressure. This allows an engine to be built for a geometric 17:1 compression ratio (longer cylinder) while also having the ability to “act” as a 10:1 compression ratio engine due to the valve pressure release. By manipulating the timing of the valve opening, the engine would operate with a compression ratio anywhere between 10:1 and 17:1 depending on the load/speed knock limit. The additional valve opening profile was developed from the initial valve opening during the exhaust stroke. The timing of the additional valve opening was manipulated over multiple simulation iterations to finally achieve approximately the same maximum cylinder pressure as the first simulation trial (Test 11 CR17b). Opening a valve twice in one cycle ideally uses direct injection and camless valve operation. Available valve actuator technology was compared to the required valve actuation speed for this design and was determined to be feasible. In addition, fuel injection timing was investigated regarding near-top dead center (TDC) injection. Fuel must be directly injected after the exhaust valve closes during the compression stroke to avoid fuel loss through the exhaust manifold. This late fuel injection was determined to be feasible based on previous injection-timing studies [12].

Davis, Shelbie L., Washko, Frank

Combustion analysis in a SI engine with homogeneous and stratified pre-chamber system

2018-36-01129/3/2018

Extensive studies of pre-chamber ignition systems in internal combustion engines have proven its effectiveness in reduction of fuel consumption and improvement in several combustion parameters. Considering the different types of pre-chamber configurations, this paper aims to compare the combustion in a SI engine with both homogeneous and stratified pre-chamber ignition systems. To achieve this objective a system with the ability to control the hydrogen injection in the pre-chamber was built. This system was installed in a multi-cylinder Ford Sigma 1.6L engine and tested in a dynamometric room. Tests consisted in imposing a constant rotation and IMEP to test three conditions: standard spark ignition, pre-chamber ignition system without fuel injection (homogenous) and with hydrogen injection (stratified). It was possible to identify that with the use of pre-chamber ignition system there is a reduction in specific fuel consumption and in the combustion duration. This phenomenon can be attributed to the increase of turbulence, created by the gases that leave the pre-chamber. With the stratified system, the presence of active chemical species resulting from the combustion of hydrogen intensifies this phenomenon.

Alvarez, Carlos Eduardo Castilla, Roso, Vinicius Rückert, Santos, Nathalia Duarte Souza Alvareng, Fernandes, Alysson Teixeira, Valle, Ramon Molina

Combustion Analysis of a Current Vehicular Engine Operating in Lean Air-Fuel Conditions

2017-36-020711/7/2017

Environmental issues and energy security are critical concerns of the most countries. According researchers, excessive growth of land vehicles is one of the biggest contributors to global air pollution and oil reserves reduction. In this context, the use of lean burn technologies emerges as a promising strategy, allowing lower fuel consumption and pollutants emissions. Present work aims to analyze the behavior of a current commercial engine, gasoline fueled, varying the air-fuel ratio without the use of lean burn ignitions technologies. Analysis was performed through bench dynamometer tests, evaluating cylinder pressure, exhaust gas temperature, fuel conversion efficiency, cycle thermal efficiency, coefficient of variation in indicated mean effective pressure, apparent heat release rate, flame development angle and burn duration. As expected, mixture impoverishment caused a progressive increase of burn duration, flame development angle and coefficient of variation in indicated mean effective pressure and a decrease in exhaust gases temperature. Difficult operation of the catalyst due to the exhaust temperature reduction and the significant increase of combustion variability, pointed out by the experimental results, reinforce the importance of the use of techniques for adequate lean mixtures burning.

Alvarez, Carlos Eduardo Castilla, Roso, Vinícius Rückert, Couto, Giselle Elias, Valle, Ramon Molina

Effect of Hydrogen Volume Ratio on the Combustion Characteristics of CNG-Diesel Dual-Fuel Engine

2017-01-227010/8/2017

CNG-diesel dual fuel combustion mode has been regarded as a practical operation strategy because it not only can remain high thermal efficiency but also make full use of an alternative fuel, natural gas. However, it is suffering from misfire and high HC emissions under cold start and low load conditions. As known, hydrogen has high flammability. Thus, a certain proportion of hydrogen can be added in the natural gas (named HCNG) to improve combustion performance. In this work, the effect of hydrogen volume ratio on combustion characteristics was investigated on an optically accessible single-cylinder CNG-diesel engine using a Phantom v7.3 color camera. HCNG was compressed into the tank under different hydrogen volume ratios varied from 0% to 30%, while the energy substitution rate of` HCNG remained at 70%. The results show that with the increase of hydrogen volume ratios, the peak of in-cylinder pressure and heat release increase significantly, and the crank angles corresponding to the maximum pressure, maximum heat release rate, and cumulative heat release rates of 5%, 20% and 50% advance. With the increase of hydrogen volume ratios, the ignition delay, from main injection timing to initial flame timing, decreases while the number of yellow ignition spots and the yellow ignition area increase. The HCNG has two ways to combustion, which are flame propagation and compression ignition. Based on the flame images, the combustion process can be divided into five phases: (1) ignition delay phase, (2) diesel premixed combustion phase, (3) diesel mixing controlled combustion phase, (4) HCNG premixed combustion phase, (5) remaining diesel mixing controlled combustion phase. Hydrogen has more notable effect on the early combustion than the late phase.

Liu, Fushui, Kang, Yue, Wu, Han, Lee, Chia-Fon, Li, Yikai

Injector Fouling and Its Impact on Engine Emissions and Spray Characteristics in Gasoline Direct Injection Engines

2017-01-08083/28/2017

In Gasoline Direct Injection engines, direct exposure of the injector to the flame can cause combustion products to accumulate on the nozzle, which can result in increased particulate emissions. This research observes the impact of injector fouling on particulate emissions and the associated injector spray pattern and shows how both can be reversed by utilising fuel detergency. For this purpose multi-hole injectors were deliberately fouled in a four-cylinder test engine with two different base fuels. During a four hour injector fouling cycle particulate numbers (PN) increased by up to two orders of magnitude. The drift could be reversed by switching to a fuel blend that contained a detergent additive. In addition, it was possible to completely avoid any PN increase, when the detergent containing fuel was used from the beginning of the test. Microscopy showed that increased injector fouling coincided with increased particulate emissions. Based on these results a selection of the injectors was installed in a laboratory injection chamber and the spray patterns were investigated with a high speed camera. Injectors corresponding to the largest PN drift produced the thinnest spray jets with the deepest penetration. These factors amplify the risk of wall wetting and provide an explanation for the increase of PN. The positive effect of the detergent was also reflected in the spray pattern analysis, which illustrates the potential benefits of such fuel additives.

Henkel, Sebastian, Hardalupas, Yannis, Taylor, Alexander, Conifer, Christopher, Cracknell, Roger, Goh, Tor Kit, Reinicke, Paul-Benjamin, Sens, Marc, Rieß, Michael

Influence of Ethanol Content, Compression Ratio and Cylinder Head Material on Idling Speed, Warm-Up Time and Emissions of a Non-Road Small Single Cylinder Gasoline Engine

2016-32-005511/8/2016

A Design of experiments methodology was carried out to investigate the effects of compression ratio, cylinder head material, and fuel composition on the engine speed, fuel consumption, warm-up time, and emissions of a carbureted single cylinder air-cooled spark ignited engine. The work presented here is aimed at finding out the sensitivity of engine responses, as well as the optimal combination among the aforementioned parameters. To accomplish this task two cylinder heads, one made of aluminum and the second one of cast iron, were manufactured; an antechamber-type adapter for the spark plug to modify the combustion chamber volume was used. Ethanol/gasoline blends containing 10 and 20 volume percent ethanol were prepared. Engine performance was evaluated based on the changes in engine speed at idle conditions. The concentrations of CO2, CO, and HC in the exhaust were recorded. The test results show that the higher engine speed, lower HC, and lower CO2 take place for the aluminum cylinder head, higher level compression ratio, and 10 percent ethanol blend combination. The lower fuel consumption corresponds with the aluminum cylinder head, higher level compression ratio, and 20 percent ethanol blend case. The shortest warm-up time is achieved with the cast iron cylinder head, the higher compression ratio, using 10 percent ethanol blend. In general, it is also concluded that CO and HC emissions decrease with the increase of the ethanol content in the fuel blend. The results indicate that cylinder head material affects engine behavior, but less than expected. Among the three factors varied within this work, and limited by their level values, the compression ratio is the most influencing parameter affecting the engine performance at idle conditions.

Romero, Carlos Alberto, Mejia, Luz Adriana, Carranza, Yamid

Comparative Study of Unregulated Emissions on a Heavy Duty CNG Engine using CNG & Hydrogen Blended CNG as Fuels

2016-01-80909/27/2016

One of the most promising solutions to address the twin problems of transport related pollution and energy security is to use alternative fuels. Compressed Natural gas (CNG) has been widely used in India to address the menace of pollution from commercial vehicles in cities like Delhi. Hydrogen blended compressed natural gas (HCNG) as a fuel has potential for further reducing harmful emissions and greenhouse gases. Enriching hydrogen in CNG improves combustion characteristic of CNG and reduces carbonyl emissions. Due to growing concerns over un-regulated emissions and their effect on human health, it is imperative to estimate un-regulated emissions from such alternatives for assessing overall impact of such fuels. Presently world over, emission legislations mainly addresses pollutants like CO, HC, NOx, CH4, NH3, PM etc. Relatively higher quantity in exhaust qualifies these pollutants to be monitored and controlled. But as the consumption of alternative fuels becomes comparable to that of the liquid fuels, other unregulated emissions like Methanol (CH3OH), Ethanol (C2H5OH), Formaldehyde (HCHO), Acetaldehyde (CH3CHO), Formic Acid (HCOOH), Acetic Acid (CH3COOH), Propene (C3H8), Ethylene (C2H4), Ethyne (C2H2) Benzene (C6H6), 1,3-Butadiene (1,3-C4H6), Toluene (C7H8), Butene (C4H8) etc. become significant. This paper presents the study of unregulated emissions on a heavy duty six cylinder engine used in the transport buses with CNG and HCNG as fuels. A transient engine dynamometer set up was used along with Fourier Transform Infrared Spectroscopy Gas Analyzer (FTIR) for measuring unregulated emissions. It was observed from the test results that regulated emissions like CO, NO, HC and PM are considerably reduced with HCNG fuel. Also, unregulated emissions like Formic Acid (HCOOH), Propane (C3H8), Ethylene (C2H4), Ethyne (C2H2), Benzene (C6H6), 1,3-Butadiene (1,3-C4H6), Toluene (C7H8) and Butene (C4H8) are significantly reduced with HCNG fuel. Whereas, there is slight increase in Methanol (CH3OH), Ethanol (C2H5OH), Formaldehyde (HCHO) and Acetaldehyde (CH3CHO) with HCNG. It can be inferred from the study that HCNG has reduced significant amount of unregulated emissions and it is the most promising fuel for transport sector in future. Beside this it is also observed that with HCNG Fuel, there is increase in NH3 and NO2 which create favorable condition for effective working of exhaust after treatment device like selective catalytic reduction (SCR) for Euro VI compliant vehicles.

Singh, Sauhard, Mishra, Sumit, Mathai, Reji, Sehgal, A K, Suresh, R

Automotive Direct-Injection Stratified-Charge Engine Development in the 1970-1980’s

2016-01-01754/5/2016

Spark-ignition direct-injection technology existed since about 1930 for the primary purpose to give multifuel capability over what the compression-ignited diesel engine could provide. In subsequent decades development of multifuel engines continued both as higher-compression-ratio “spark-ignited diesel” and moderate-compressionratio stratified-charge engines. Global events in the 1960-1970’s, namely the oil embargo, oil-supply crises, and the passage of the U.S. Clean Air Act intensified interest in such engines. The military and large commercial fleet operators were particularly focused on efficiency and multifuel capability over concerns for fuel supplies. Automobile manufacturers were focused on gasoline-fueled efficiency and the potential to reduce engine-out legislated NOx emissions with the stratified-charged combustion systems. In this paper the major direct-injection spark-ignited stratified-charge concepts pursued during the 1970-1980’s are reviewed at a high level, and relevant references are cited. Examination of this development history should be of interest to those working on modern gasoline direct-injected engines, as a variety of concepts were pursued, with the physics of those combustion processes being pertinent to today’s systems in production and under development. In many cases advances in fuel-injection hardware, enabled by modern manufacturing methods, and control technologies, enabled by modern computers and sensors, have allowed design objectives of the past to be implemented successfully today.

Groff, Edward G.

E100 Stratified Lean Combustion Analysis in a Wall-Air Guided Type GDI Optical Engine

2015-36-02699/22/2015

Gasoline direct injection (GDI) engines have very attractive potential for improving fuel economy and exhaust emissions, especially disadvantages of increased fuel consumption at part load. In this research, a study has been made on the investigations of stratified lean combustion in a wall-air guided type spark-ignition single cylinder optical research engine. Experiments were conducted at constant load (NIMEP 3 bar) using ethanol as fuel, for a wide range of injection, ignition and mixture formation parameters. Engine efficiency and combustion stability were evaluated at each excess air ratio. Optical visualization illustrated the spray behavior and flame propagation. Specific fuel consumption improvement was achieved with lean burn mixtures. Thus, combustion analysis data based on in-cylinder pressure measurement provide useful data for ethanol GDI engine development.

da Costa, Roberto Berlini Rodrigues, Gomes, Carlos Alberto, Franco, Rafael Lara, Guzzo, Marcio Expedito, Pujatti, Fabrício José Pacheco

Development of a Quasi-Dimensional Spray Evaporation and Mixture Formation Model for Direct-Injection Spark-Ignition Engines

2015-24-24719/6/2015

This paper presents a phenomenological quasi-dimensional model of the processes that lead to charge preparation in a Direct-Injection Spark-Ignition (DI-SI) engine, focusing on the physics of atomization and drop evaporation, spray development and the mutual interaction between these phenomena. Atomization and drop evaporation are addressed by means of constant-diameter drop parcels, which provide a discrete drop-size distribution. A discrete Probability Density Function (PDF) approach to fuel/air mixing is proposed, based on constant-mixture-fraction classes that interact with each other and with the drop parcels. The model has been developed in the LMS Imagine.Lab Amesim™ system simulation platform for multi-physical modeling and integrated in a generic SI combustion chamber submodel, CFM1D [15], of the IFP-Engine library. The validation of the approach is performed on an experimental test case consisting of a high pressure isooctane injection in a constant volume vessel for which mie-scattering and high-speed schlieren visualizations for different thermodynamic conditions were performed at IFPEN within the framework of the French government MAGIE R&D project. Liquid and vapor penetration as well as spray angle data from experiments are then used to tune the RANS CFD simulations performed with the IFP-C3D code. CFD provides further data which is not directly available from the experiments such as drop size and charge distributions as well as spray properties outside the optical measurement field, which are then used to tune and validate the 0D model. Good accordance is found between validation data and the results obtained with the proposed model showing the advantages of a detailed - though phenomenological - description of the main phenomena involved.

Pellegrino, Federico, Dulbecco, Alessio, Veynante, Denis

An Optical Analysis of a DISI Engine Cold Start-Up Strategy

2015-01-18779/1/2015

Particulate number (PN) standards in the current ‘Euro 6’ European emissions standards pose a challenge for engine designers and calibrators during the warm-up phases of cold direct injection spark ignition (DISI) engines. To achieve catalyst light-off in the shortest time, engine strategies are often employed which inherently use more fuel to attain higher exhaust temperatures. This can lead to the generation of locally fuel-rich regions within the combustion chamber and the emission of particulates. This investigation analyses the combustion structures during the transient start-up phase of an optical DISI engine. High-speed, colour 9 kHz imaging was used to investigate five important operating points of an engine start-up strategy whilst simultaneously recording in-cylinder pressure. Results show a striking range of flame structures occurring at different times in the start-up cycle with significant differences in flame propagation rates, flame front structures and local air-fuel ratios (AFRs). High-luminosity regions, occurring due to observed soot incandescence, identify distinct regions of potential soot generation. The processed pressure data shows a clear link between engine performance and flame growth speed and structures.

Efthymiou, Petros, Garner, Colin P., Hargrave, Graham K., Richardson, David

Evaluation of Long Drain Gas Engine Oil on Heavy Duty Engine Using Hydrogen Blended CNG

2015-01-09664/14/2015

The ever increasing demand of fuels for vehicles can only be met by use of alternate fuels like Compressed Natural Gas (CNG) and Hydrogen (H2). The 18 percent hydrogen enriched CNG fuel referred to as HCNG has the potential to lower emissions and is considered to be the first step towards promotion of a Hydrogen economy. While, automotive industry matures up with the usage of new engines, lubricant manufacturers are also moving on to the next stage by formulating oils to be used in gas engines such as CNG, HCNG etc. This paper presents the evaluation of gas engine oil on 6-cylinder heavy duty CNG engine using HCNG. The six cylinder engine was chosen due to its importance for urban bus transportation. The engine was optimized for using HCNG fuel. Initial performance of the engine using HCNG was compared vis-à-vis CNG and, thereafter, the engine was subjected to endurance test of 500 hours as per 8 mode engine simulated driving cycle. It has been observed that HCNG shows reduction of CO, THC and CH4 emissions and NOx emissions increased as compared to CNG. However, these values meet the Euro IV emission norms. Oil sampling and analysis were undertaken after completion of every 100 hrs. Also, performance and emission characteristics of the engine were analyzed after completion of every 100 hours as per European Transient Cycle (ETC). The performance parameters of the engine lubricant such as kinematic viscosity @ 40°C, kinematic viscosity @ 100°C, viscosity index and TBN over the complete endurance test of 500 hrs were within the permissible limits. Wear elements like Fe, Al, Sn, Cr, Si, Pb, Ag etc. were within limits over the period of endurance test of 500 hrs. Specific fuel consumption (SFC) measurements were consistent at all the 8 modes of engine simulated driving cycle. Test results indicates that over the period of endurance test of 500 hrs with HCNG, all the major exhaust emissions species such as CO, THC, CH4 and NOx emissions were lower than the Euro IV emission norms for the heavy duty engines and there were no significant changes in the CO2 values. The study shows that the engine oil can be used for long drain application.

Singh, Sauhard, Bhardwaj, Anil, Mathai, Reji, Sehgal, A K, Suresh, R, Das, B P, Tyagi, Nishant, Mohite, Jaywant, Chougule, N B

A Study of Potential Fuel Economy Technologies to Achieve CAFE 2025 Regulations using Fleet Simulation Modeling Software

2015-01-16834/14/2015

The 2025 Corporate Average Fleet Economy (CAFE) fuel economy regulations are a significant challenge to the automotive industry. These regulations require dramatic increases in vehicle fleet fuel economy. This paper will identify and analyze a portfolio of technologies that have the potential to achieve the 2025 CAFE fuel economy targets, focusing on powertrain enhancements. The study uses a MAHLE Powertrain developed fleet modeling tool and a range of vehicle technologies and powertrain data taken from MAHLE's global research and development activities. Powertrain technologies considered include extreme engine downsizing, dilute combustion, friction reduction, hybridization, diesel and alternative fuels. The vehicle technologies analyzed include vehicle light weighting, reduced rolling resistance, advanced transmissions and improved aerodynamics. The results of this study suggest that in order to meet CAFE 2025 fleet fuel economy regulations, a combination of advanced powertrain, drivetrain and vehicle technology changes will be required.

Porter, Bernie, Blaxill, Hugh, Jariri, Noor

Study on Effect of Engine Operating Parameters on Flame Characteristics

2015-01-07494/14/2015

In gasoline direct injection (GDI) engines, air-fuel mixture homogeneity plays a major role on engine performance, especially in combustion and emission characteristics. The performance of the engine largely depends on various engine operating parameters viz., start of injection, duration of injection and spark timing. In order to achieve faster results CFD is becoming a handy tool to optimize and understand the effect of these parameters. Therefore, this study aims on evaluating the two injection parameters viz., single and split injection to evaluate different flame characteristics. Novelty in this study is to define five different parameters which are called α, β, γ, δ and η the details of which are explained in the paper. In order to understand the flame characteristics, these five parameters are found to be very useful. In the present study, a single-cylinder, two-valve, four- stroke engine which is used in two-wheelers in India is considered for carrying out the CFD analysis. An air-assisted direct in-cylinder fuel injection is considered for the analysis and experiments. Commercial software is used for carrying out the combustion analysis. For specifying the boundary conditions, pressure measurements were made in an actual engine. In order to study the effect of engine performance three different start of injection, duration of injection, spark timings, fuel split ratios are considered. In order to validate the CFD results, measurements of output power is made on the actual engine and is compared with the CFD predictions. From the results obtained, it is concluded that for better mixing and good combustion, for single injection case, SOI of 198 CAD and 3 ms injection duration, with 20° spark advance found to be the best. Similarly for split injection case, fuel split ratios of 2:1 with SOI of 45 and 250 CADs for first and second injections respectively are found to be the best.

Sureshkumar, J., Venkitachalam, Ganesan, Mallikarjuna, J M, Elayaraja, R

Injection Strategies, Optimization and Simulation Techniques on DI CNG Technology

2015-26-00461/14/2015

CNG has long since been established as a front runner amongst other available alternative fuels. In India, its infrastructure and penetration far exceeds others. While other, more efficient alternatives are been researched, CNG has established itself in the market as the alternative fuel of choice for majority of Indians. CNG technology has evolved itself from the basic venturi system to the more efficient sequential injection system nowadays. While the efficiency of an engine using sequential injection CNG has increased, the inherent problem with respect to lower volumetric efficiency and hence less power still persists. Direct injection CNG technology is seen as the solution to this age old problem. In the older days, the lack of technological expertise in SI direct fuel injection provided a stumbling block for development of direct gas injection. But with the surge in technological advancement lately, especially in the gasoline direct injection area has opened new avenues for development of gas direct injection technology. DI CNG technology has the benefits of increased power, improved BSFC and lower emissions. Further the challenges in this technology are lower injector life and expensive modifications in the MPFI technology. In this paper we look at the various injection strategies, experiments and simulation analysis carried out worldwide on DI CNG technology and the potential this area has in unleashing the true benefits of CNG fuel. Further this research will help us in developing our own DI CNG engine in the future.

Thipse, Sukrut S, Sonawane, Shailesh B, D' Souza, Ashwin F, Rairikar, S D, Kavathekar, Kishor Kumar, Marathe, Neelkanth V

Aerodynamic In-Cylinder Flow Simulation in an Internal Combustion Engine with Torch Ignition System

2014-36-02989/30/2014

Stringent automotive emissions and fuel economy regulations have been bringing challenges for the development of new engine technologies to achieve greater levels of efficiency and pollutants reduction. In this scenario the homogeneous charge pre-chamber jet ignition system (HCJI) enables lean operation due the jet combustion gases emerging from the small pre-chamber combustor as the ignition source for main chamber combustion in an internal combustion engine. The present computational work was carrying out to investigate the interaction between the pre-chamber and main chamber fluid dynamics events. This CFD research was performed and validated with a experimental data for a single cylinder of a 4-stroke indirect fuel injection engine under the motoring condition running at 4500 rpm with 50% wide open throttle condition. The analyses are focused to identify the influences in the fluid flow field in the terms of tumble ratio and the turbulence kinetic energy along the degree of crank angle during intake and compression stroke. The computational results can explain better the homogeneity with this new combustion system configuration.

BORGHI, F. T., MOREIRA, T. A. A., WHANCO, R., BARROS, J. E. M, VALLE, R. M.

Automotive Fuels Reference Book, Third Edition

The first two editions of this title, published by SAE International in 1990 and 1995, have been best-selling definitive references for those needing technical information about automotive fuels. This long-awaited new edition has been thoroughly revised and updated, yet retains the original fundamental fuels information that readers find so useful. This book is written for those with an interest in or a need to understand automotive fuels. Because automotive fuels can no longer be developed in isolation from the engines that will convert the fuel into the power necessary to drive our automobiles, knowledge of automotive fuels will also be essential to those working with automotive engines. Small quantities of fuel additives increasingly play an important role in bridging the gap that often exists between fuel that can easily be produced and fuel that is needed by the ever-more sophisticated automotive engine. This book pulls together in a single, extensively referenced volume, the three different but related topics of automotive fuels, fuel additives, and engines, and shows how all three areas work together. It includes a brief history of automotive fuels development, followed by chapters on automotive fuels manufacture from crude oil and other fossil sources. One chapter is dedicated to the manufacture of automotive fuels and fuel blending components from renewable sources. The safe handling, transport, and storage of fuels, from all sources, are covered. New combustion systems to achieve reduced emissions and increased efficiency are discussed, and the way in which the fuels’ physical and chemical characteristics affect these combustion processes and the emissions produced are included. There is also discussion on engine fuel system development and how these different systems affect the corresponding fuel requirements. Because the book is for a global market, fuel system technologies that only exist in the legacy fleet in some markets are included. The way in which fuel requirements are developed and specified is discussed. This covers test methods from simple laboratory bench tests, through engine testing, and long-term test procedures.

CNG Fueling Strategies for Commercial Vehicles Engines-A Literature Review

2013-01-281211/27/2013

The paper presents a survey of the opportunities to convert compression ignition heavy duty truck engines to work on single or dual fuel modes with CNG. In one popular option, the compression ignition engine is converted to spark ignition with throttle load control and port injection of the CNG. In another option of increasing popularity, the LNG is directly injected and ignited by direct injection of pilot Diesel. This latter option with direct injection of natural gas and diesel through separate injectors that are fully independent in their operation is determined to be the most promising, as it is expected to deliver better power density and similar part load fuel economy to Diesel.

Boretti, Alberto, Lappas, Petros, Zhang, Bingjie, Mazlan, Siti Khalijah

Advanced Glow Plug for Heavy Fuels Applications

2013-01-17164/8/2013

With current DoD goals of switching to a common battlefield logistics fuel, there is a significant push to develop technologies that allow small, high-powered engines such as used in unmanned aerial, marine, and ground vehicles, typically fueled by volatile fuels such as gasoline, to operate on heavy fuels such as JP-8. In this paper, the feasibility of catalytic glow plugs as an enabling component for the use of heavy fuels both as a retrofit to existing engines as well as new engine designs is demonstrated. Compared to standard spark igniters and non-catalytic glow plugs, the use of catalytic glow plugs will provide benefits including lower required compression ratio, improved igniter life, reduced energy requirements, and overall reduction in system weight and size. The catalytic glow plugs were shown to have a significant increase in surface temperature (180+°C) with impingement of a fuel spray and this increase was maintained over many cycles of impingement. Engine testing demonstrated the use of catalyst-allowed stable engine operation at reduced power requirements with durability exceeding 150 hrs. This technology would allow the use of logistic heavy fuels in small engines, while potentially reducing power supply weight and engine complexity and weight, both of which would allow greater range and/or payload capacity.

Baird, Benjamin, Etemad, Shahrokh

Laser Diagnostics and Optical Measurement Techniques in Internal Combustion Engines

The increasing concern about CO2 emissions and energy prices has led to new CO2 emission and fuel economy legislation being introduced in world regions served by the automotive industry. In response, automotive manufacturers and Tier-1 suppliers are developing a new generation of internal combustion (IC) engines with ultra-low emissions and high fuel efficiency. To further this development, a better understanding is needed of the combustion and pollutant formation processes in IC engines. As efficiency and emission abatement processes have reached points of diminishing returns, there is more of a need to make measurements inside the combustion chamber, where the combustion and pollutant formation processes take place. However, there is currently no good overview of how to make these measurements. Based on the author’s previous SAE book, Engine Combustion Instrumentation and Diagnostics, this book focuses on laser-based optical techniques for combustion flows and in-cylinder measurements. Included are new chapters on optical engines and optical equipment, case studies, and an updated description of each technique. The purpose of this book is to provide, in one publication, an introduction to experimental techniques that are best suited for in-cylinder engine combustion measurements. It provides sufficient details for readers to set up and apply these techniques to IC engines and combustion flows.

Enabling High Efficiency Direct Injection Engine with Naphtha Fuel through Partially Premixed Charge Compression Ignition Combustion

2012-01-06774/16/2012

More stringent emissions standards along with higher fuel economy demands have obliged auto makers to develop technical solutions that exploit synergistic features from gasoline and diesel engines. To minimize NOx and soot trade-off, diesel powertrain has been developed to adopt increasingly complex and expensive technology such as extremely high pressure fuel injection systems, low pressure EGR, and variable valve timing. These attempts are associated with promoting Partially Premixed Charge Compression Ignition (PPC-CI) combustion via increasing mixing time and ignition delay. Alternatively, PPC-CI combustion can be achieved easier by using fuels with higher resistance to auto-ignition than conventional diesel fuel. Previous work has demonstrated the possibility of reducing the cost of future diesel after-treatment systems by using gasoline-like fuels. In this study, we start with a 0.5-liter single-cylinder direct injection spark ignition (DISI) engine and demonstrate that fuel economy can be improved significantly by running it in PPC-CI mode. Naphtha, less processed refinery stream in the gasoline boiling and carbon number range, but with lower Octane Number, has been run in a 12:1 compression ratio single-cylinder engine with DISI fuel system and shallow oval-type bowl piston. Both light and heavy Naphtha were successfully run in PPC-CI mode with regular valve events and intake charge boosting at six engine running conditions representative of a typical urban driving cycle including idle. Very low NOx level was achieved through high EGR and advanced injection timings to segregate the fuel injection from heat release. When compared to a Stoichiometric SI operation with optimal valve timings, 19% weighted cycle average fuel consumption reduction was achieved. This result demonstrates that an engine equipped with a low cost DI system could offer noticeably better efficiency through PPC-CI combustion, especially when run with Naphtha, which can provide lower CO₂ emission in a refinery process. Although further work is needed to develop a practical engine, high efficiency, reduced system cost and overall CO₂ footprint benefits can be achieved by matching the fuel and the combustion system.

Chang, Junseok, Kalghatgi, Gautam, Amer, Amer, Viollet, Yoann

Experimental Investigation in Combustion Characteristics of Ethanol-gasoline Blends for Stratified Charge Engine

2011-32-055111/8/2011

The increasing of global energy demand and stringent pollution regulations have promoted research on alternative fuels. In Thailand, ethanol, can be produced from many sources of national agriculture products as renewable fuel, which was strongly promoted by government due to its many merits for use in transportation field. In this study, combustion characteristics of ethanol-gasoline blend (20%, 85%, and 100%) as well as pure gasoline (E0) were investigated by using a swirl-generated constant volume combustion chamber. Flame propagations of different fuel blends were observed by high speed Schlieren photography technique while pressure history data were recorded for detailed combustion analysis. Combustion behavior, combustion duration and rate of pressure rise of all tested fuels were investigated in various swirl intensities and equivalence ratios. In addition, effect of swirl intensities and ethanol concentration on lean misfire limit were also discussed. The results showed that the high concentration of ethanol blend with the high swirl intensity can significantly extended lean misfire limit while lowering combustion variations. Furthermore, combustion duration can be accelerated by increasing the percentage of ethanol in fuel blend. Through this study, a better understanding of stratified charge combustion fuelled with ethanol/gasoline blends can be achieved.

Charoenphonphanich, Chinda, Ornman, Piyaboot, Karin, Preechar, Kosaka, Hidenori, Chollacoop, Nuwong

The Twin Swirl “MR-Process” Combustion Mechanism and Conversion of Diesel Engines to Operate with Gaseous Fuels

2011-24-00669/11/2011

Converting diesel engines to cheaper and cleaner fuels like LPG and CNG, with conventional methods needs a different combustion chamber, which has a lower compression ratio than a diesel engine (≻16:1) due to risk of detonation. This alteration makes the conversion process more expensive and difficult. On the other hand, decreasing a compression ratio leads to lower performance and efficiency compared to those of the original engine. To overcome this disadvantage it is proposed a novel mechanism for mixture formation and combustion, named as "MR-Process." This mechanism is realized in a combustion chamber MR-2 with twin-swirl turbulent flow. This chamber is suitable for operation with diesel fuels as well as with LPG and NG. In this paper are presented theoretical and experimental investigations of engines operating with "MR-Process" combustion mechanism.

Mehdiyev, Rafig, Ogun, Kurtulus, Ozcan, Enishan, Arslan, Hikmet, Babaoglu, Osman, TEKER, Hüseyin

Effect of Hydrogen in CNG on Small Engine Performance and Emissions

2011-24-02029/11/2011

Three-wheelers have a long history in Europe and Asia as extremely durable and reliable passenger and delivery vehicles. There are a number of reasons that have resulted into the proliferation of the 3-wheelers in developing countries especially in South Asian countries. 3-wheelers are quite economical in terms of manufacturing and maintenance. They have also earned huge popularity due to their easy maneuvering capabilities. The inherent engine design of 3-wheeler with conventional fuels have recognized for lower fuel economy and higher emissions. Concerns about energy security, air quality and need for sustainable economic growth are making it imperative that all nations, especially developing countries, begin making an accelerated transition from fossil fuels to clean energy alternatives. South Asian countries have already done a remarkable job of converting a large number of three-wheelers and buses to compressed natural gas (CNG), and in India there is an on-going effort to extend this transition to hydrogen blended CNG (HCNG). Hydrogen is being added in CNG as an additive for further improving its combustion efficiency. Optimized hydrogen enriched natural gas (HCNG) engine has potential in reducing of harmful emission and greenhouse gases. This paper highlights engine performance, regulated and non-regulated emissions using CNG and 18% HCNG blend (v/v) with different measures in a CNG three-wheeler was tested on chassis dynamometer for performance and emissions. Ignition timing of the engine was optimized for better performance. Results indicated that significant reduction in CO and HC with penalty in increase NOx emission with use of HCNG fuel. To control NOx emissions, simple mechanism of EGR system was introduced. Although hydrogen enriched fuel reduces harmful emissions significantly, non-regulated emissions were observed with HCNG fuel. Growing concern over non-regulated emissions, it is imperative to estimate non-regulated emission for assessing overall emission advantages of HCNG fuel. Non-regulated emission also measured and reported for overall emission benefits with use of HCNG fuel.

SUBRAMANIAN, MUTHAN

A Comparison of Spray-Guided Stratified-Charge Combustion Performance with Outwardly-Opening Piezo and Multi-Hole Solenoid Injectors

2011-01-12174/12/2011

This investigation was aimed at measuring the relative performance of two spray-guided, single-cylinder, spark-ignited direct-injected (SIDI) engine combustion system designs. The first utilizes an outwardly-opening poppet, piezo-actuated injector, and the second a conventional, solenoid operated, inwardly-opening multi-hole injector. The single-cylinder engine tests were limited to steady state, warmed-up conditions. The comparison showed that these two spray-guided combustion systems with two very different sprays had surprisingly close results and only differed in some details. Combustion stability and smoke emissions of the systems are comparable to each other over most of the load range. Over a simulated Federal Test Procedure (FTP) cycle, the multi-hole system had 15% lower hydrocarbon and 18% lower carbon monoxide emissions. Most significantly, the spray guided system with the multi-hole spray ended up having 3.0% lower fuel consumption than the piezo system over the simulated FTP cycle.

Smith, James, Szekely Jr, Gerald, Solomon, Arun, Parrish, Scott

A Continuous Discharge Ignition System for EGR Limit Extension in SI Engines

2011-01-06614/12/2011

A novel continuous inductive discharge ignition system has been developed that allows for variable duration ignition events in SI engines. The system uses a dual-coil design, where two coils are connected by a diode, combined with the multi-striking coil concept, to generate a continuous current flow through the spark plug. The current level and duration can be regulated by controlling the number of re-strikes that each coil performs or the energy density the primary coils are charged to. Compared to other extended duration systems, this system allows for fairly high current levels during the entire discharge event while avoiding the extremely high discharge levels associated with other, shorter duration, high energy ignition systems (e.g. the plasma jet [ 1 , 2 ], railplug [ 3 ] or laser ignition systems [ 4 , 5 , 6 , 7 , 8 ]. Tests on a single cylinder of a 4-cylinder engine indicated that the addition of the continuous discharge mode resulted in a larger improvement in burn rate and stability than was achieved by either one coil in multi-strike mode or both coils in multi-strike mode with simultaneous discharge. The improvement in burn rate and stability translated into improved fuel consumption, particularly at low specific power levels and at high engine speeds. Finally, the improvement in EGR tolerance at low load conditions is seen as an important enabler for high dilution engines, as the requirement for engine stability during throttle tip-out is an important limiting factor in the ultimate EGR levels targeted by engine designers.

Alger, Terrence, Gingrich, Jess, Mangold, Barrett, Roberts, Charles

A Review of Pre-Chamber Initiated Jet Ignition Combustion Systems

2010-01-226310/25/2010

This paper reviews progress on turbulent jet ignition systems for otherwise standard spark ignition engines, with focus on small prechamber systems (≺3% of clearance volume) with auxiliary pre-chamber fueling. The review covers a range of systems including early designs such as those by Gussak and Oppenheim and more recent designs proposed by General Motors Corporation, FEV, Bosch and MAHLE Powertrain. A major advantage of jet ignition systems is that they enable very fast burn rates due to the ignition system producing multiple, distributed ignition sites, which consume the main charge rapidly and with minimal combustion variability. The locally distributed ignition sites allow for increased levels of dilution (lean burn/EGR) when compared to conventional spark ignition combustion. Dilution levels are comparable to those reported in recent homogeneous charge compression ignition (HCCI) systems. In addition, jet ignition systems have the potential for combustion phasing control and hence speed/load range benefits when compared to HCCI, without the need for SI-HCCI combustion mode switching. The faster burn rates also allow for a base compression ratio increase (1-2 points) when compared to spark ignition and when combined with diluted mixture combustion, provide increased engine efficiency.

Toulson, Elisa, Schock, Harold J., Attard, William P.

CFD Modeling of In-Cylinder Fuel-Air Mixing in a CNG-Fuelled SI Engine with Port Gas Injection

2010-32-00039/28/2010

The concept of fuel-air mixture stratification is evaluated for a single cylinder, 200-cc CNG-fuelled SI engine with port gas injection (PGI). A detailed study based on three-dimensional computational fluid dynamics (CFD) modeling has been reported. Fuel-air stratification was observed in case of PGI compared to premixed fuel-air mixture formed by a conventional gas carburetor system. Overall stratification of more than 15% was observed for PGI between the rich and lean zones in the combustion chamber compared to less than 1% in case of premixed gas carburetor. It was observed that the gas injection location, direction, timing, duration and injection pressure have a significant effect on stratification pattern.

Garg, Manish, Ravikrishna, R

High Speed Endoscope Imaging to Supplement CFD Analysis and Combustion Testing for SIDI Engine Startup Development

2010-01-03474/12/2010

Optimization of engine startup from crank to catalyst light-off is essential for achieving low emissions. For Spark Ignition Direct Injected (SIDI) engines, this requires optimization of the piston crown features, spray characteristics and control strategy. In this case study, high speed endoscope imaging was used to provide a qualitative confirmation of CFD spray predictions and to provide insight into engine starting in a “real” engine environment. The effect of piston feature was initially evaluated in a single cylinder engine running the dual-injection catalyst heating mode. The piston features were also assessed at part load and wide open throttle. The videos of the spray development were compared to CFD predictions. In the example case reported here, endoscope imaging showed that the baseline piston bowl was not effective in deflecting the spray toward the spark plug. Moving the piston bowl toward the injector gave a visible improvement in the spray deflection. Engine tests confirmed improved combustion stability. A unique rigid camera-mounting system allowed similar endoscope access on a multi-cylinder engine to provide continuous imaging of the actual crank, crank-to-run, and light-off processes. The impact of injection pressure during startup on the initial spray and combustion events could be readily visualized to assist calibration. These results confirmed that high speed endoscopy can be applied to practical engine development programs for qualitative CFD validation and to assist in engine startup and catalyst heating mode development.

Sczomak, David P., Zhao, Allan, Simon, Michael, Zeng, Yangbing

Development of a Quasi-Dimensional Combustion Model for Stratified SI-Engines

2009-01-265911/2/2009

The simulation of the combustion process is an essential part of the internal combustion engine development. For simulating whole engine maps quasi-dimensional models in combination with 1-D-flow simulations are widely used. This procedure is beneficial due to short computation times and accurate forecast capability of quasi-dimensional combustion models. For the simulation of homogeneous SI-engines the two-zone entrainment model is usually used, which is based on hemispherical flame propagation. In this work a new approach for the quasi-dimensional calculation of the stratified SI-engine combustion process is proposed, which is based on the two-zone entrainment model. This proven approach was extended with regard to the inhomogeneous air/fuel composition of stratified SI-engines that make a two-zone treatment not sufficient. Therefore, four unburnt zones are defined: a rich zone, a stoichiometrical zone, a lean zone and a remaining air zone. Furthermore in analogy to existing approaches a burnt zone is defined. These zones are connected to each other by mass flow rates which are calculated by a mixture model. This mixture model considers the current geometry of the zones. In order to model the combustion progress a complete new approach for the flame propagation was developed that meets the concerns of the stratified combustion process. The newly developed approach was validated on measurement data of a modern, stratified SI-engine with multiple injection. 158 operating points were validated, that are covering the whole stratified range of the engine. The selected operating points also include a detailed variation of the multiple injection capabilities. A high accuracy of forecast capability could be proven by the new combustion model.

Schmid, Andreas, Grill, Michael, Berner, Hans-Jürgen, Bargende, Michael, Rossa, Sascha, Böttcher, Michael

High Injection Pressures at the Upper Load Limit of Stratified Operation in a DISI Engine

2009-01-265711/2/2009

This paper presents the results of investigations that were carried out on a single-cylinder spray-guided direct injection engine. The effects of injection pressures of up to 1000 bar on combustion and emissions at the stability limit of stratified load are presented. It is known that at low engine speeds, problems in mixture preparation occur due to insufficient in-cylinder motion at higher loads in stratified charge operation. Additionally, adverse effects appear at high engine speeds due to limited time for vaporization and mixture formation. Therefore, investigations at various engine speeds ranging from 2000 to 4000 rpm were performed. As a baseline, a production multihole injector is compared with an injector that has been specially adapted for higher injection pressures.

Buri, S., Busch, S., Kubach, H., Spicher, U.

Structure of a Partially Premixed Iso-Octane/Air Turbulent V-Flame

2009-01-265511/2/2009

The effect of the equivalence ratio gradient on a partially premixed, iso-octane/air, rod-stabilized turbulent V-flame was studied. Using a uniquely designed rectangular exit burner, the equivalence ratio was varied linearly along the exit of the burner while the global equivalence ratio was fixed at stoichiometric. A two-dimensional spectrometer provided line measurements along a wide spectral range (UV to near IR) and was used to identify radiating species to characterize each branch of the partially premixed flame (PPF). Chemiluminescence imaging of OH* and CH* was used to evaluate the general structure of the PPF and assess its potential use as an estimate of time averaged heat release rates. Planar Laser Induced Fluorescence of OH (OH-PLIF) images were collected to investigate the varying topography of the PPF. Variations of wrinkling scales, flame brush, and tribrachial flame structure were observed and discussed for different gradients in equivalence ratio.

Vena, P. C., Deschamps, B. M., Smallwood, G. J., Johnson, M. R.

Investigating Unburned Hydrocarbon (UHC) Emissions in a GDI Engine (Homogeneous and Stratified Modes) Using Formaldehyde LIF and Fast-FID Measurements in the Exhaust Port

2007-01-402910/29/2007

An experimental method was set up in a single cylinder optical engine in GDI configuration to study UHC origins in both homogeneous and stratified operation. On the one hand, UHC were observed in the combustion chamber by formaldehyde LIF (excitation at 355 nm and collection from 400 to 470 nm). Formaldehyde is a natural UHC tracer since it results from partly decomposed fuel that has not been fully oxidized during combustion. A quartz cylinder liner was used in order to benefit from a large optical access. On the other hand, UHC emissions measurement were simultaneously performed with a fast FID analyzer whose sampling probe was located 2 cm downstream the exhaust valve, in one of the two exhaust ports. An instantaneous exhaust mass flow model was also developed using 0-D simulation. The computed mass flow rate was coupled to fast FID measurements to estimate instantaneous and cycle to cycle UHC emissions. Temporal form of the fast FID signals was correlated to the UHC visualizations and was found to provide valuable information to investigate UHC sources. In case of stratified combustion, UHC were located in the whole volume of in-cylinder gases, with significant local heterogeneities, UHC were mostly attributed to flame quenching in over mixed (too lean) regions and partial oxidation in under mixed (too rich) zones. In homogeneous mode, UHC were rather observed close to the walls, with very low UHC concentration in the in-cylinder bulk gases. UHC appeared to be mostly due to flame quenching along the walls and in crevices.

de Francqueville, L., Thirouard, B., Cherel, J.

The Prospects of Using Alcohol-Based Fuels in Stratified-Charge Spark-Ignition Engines

2007-01-403410/29/2007

Near-term energy policy for ground transportation is likely to have a strong focus on both gains in efficiency as well as the use of alternate fuels; as both can reduce crude oil dependence and carbon loading on the environment. Stratified-charge spark-ignition direct-injection (SIDI) engines are capable of achieving significant gains in efficiency. In addition, these engines are likely to be run on alternative fuels. Specifically, lower alcohols such as ethanol and iso-butanol, which can be produced from renewable sources. SIDI engines, particularly the spray-guided variant, tend to be very sensitive to mixture preparation since fuel injection and ignition occur within a short time of each other. This close spacing is necessary to form a flammable mixture near the spark plug while maintaining an overall lean state in the combustion chamber. As a result, the physical properties of the fuel have a large effect on this process. Since alcohols tend to have higher heats of vaporization & lower energy densities compared to gasoline (which requires a greater fuel mass to be injected), the local conditions at the time of ignition can be very different from more conventional fuels. In this study, an optically accessible engine is used along with high-speed image and pressure data, to study the operating characteristics when fuelled with ethanol & iso-butanol. These results are compared to those of iso-octane, a pure chemical commonly substituted for gasoline. First, a mapping study is completed to demonstrate that comparable performance can be achieved between the three fuels. Next, ignition and burning characteristics are analyzed and any differences between the fuels are highlighted. Finally, high-speed laser-induced fluorescence is used to study the evaporation and mixing process of the three fuels around the time of ignition. Through this study, a better understanding of SIDI engines run on alternative fuels can be achieved.

Smith, James D., Sick, Volker

Modern Engine Technology from A to Z

Part dictionary, part encyclopedia, Modern Engine Technology from A to Z will serve as your comprehensive reference guide for many years to come. Keywords throughout the text are in alphabetical order and highlighted in blue to make them easier to find, followed, where relevant, by subentries extending to as many as four sublevels. Full-color illustrations provide additional visual explanation to the reader. This book features: approximately 4,500 keywords, with detailed cross-references more than 1,700 illustrations, some in full color in-depth contributions from nearly 100 experts from industry and science engine development, both theory and practice

Van Basshuysen, Richard, Schaefer, Fred

Analysis for suitability of Loop and Cross Scavenged System for Stratified Charged Engine

2007-24-00649/16/2007

The results obtained with Loop & Cross scavenged systems reveal that during early charging period the scavenged through losses are more in loop scavenged system in comparison to cross scavenged and in later part both shows considerable improvement still the probability of trapping of charge in cross scavenged are higher. Therefore stratification of charge helps in reducing the loss of fuel in both the system. But in case of cross scavenged system due to better trapping characteristics throughout the scavenging process leads to improved combustion too. Cross scavenged system employed with dual intake system shows reduction in fuel of the order of 26% & 29.7% for 40% & 50% flow through AASL, whereas, loop scavenged system shows 12.85% & 14.4% for the same flow through AASL.

Berwal, A. K., Gupta, V. K., Saxena, Mukesh

Experimental and Theoretical Investigation of Non-Quasi-Homogeneity of Flame Propagation in Stratified Media

2007-01-01304/16/2007

A combined experimental and theoretical study is presented of the conditions under which flame propagation in stratified media can differ from “quasi-homogeneity”, i.e. propagation with the flame speed corresponding to the local equivalence ratio in the unburnt mixture. To this extent, OH chemiluminescence intensity measurements were performed in flames propagating through step-changes in equivalence ratio (from Φ=1 to 0.9, 0.6 and 0.5). The results showed a heat “back-support” into the flames, a phenomenon that was stronger with increasing equivalence ratio steps. In order to theoretically model flame propagation in fuel concentration gradients, heat flux from burnt gases and fuel mass fraction gradient across the reaction sheet were incorporated into the conventional asymptotic solution for flame propagation in perfectly premixed mixtures. Theoretical results provided an explanation for the experimental finding that departure from quasi-homogeneity is more pronounced in leaner mixtures and greater equivalence ratio gradients.

Kang, Taekyu, Kyritsis, Dimitrios C.

Experiments on Compression Ignition by Air Injection (CIBAI) in a Modified Single-Cylinder, Four-Stroke, Spark Ignition, Cooperative Fuel Research (CFR) Engine: A Novel Approach

2006-01-335710/16/2006

Compression ignition by air injection (CIBAI) has been successfully achieved in a modified single cylinder, four-stroke, spark ignition cooperative fuel research (CFR) engine. This new combustion concept has the potential to replace traditional spark ignition and high-pressure fuel injection controlled ignition. Its high ignition energy provides the capability to rapidly ignite ultra-lean air-fuel mixtures, to maximize combustion compression with associated thermal efficiency, while reducing NOX formation. This paper presents the results of the first group of experiments conducted at West Virginia University on compression ignition by air injection (CIBAI). The objective of these experiments was to demonstrate experimentally the viability of achieving ignition by air injection (CIBAI) for controlled auto-ignition (CAI) in a CFR engine.

Echavarria, Fernando, Loth, John, Morris, Gary

Model for Control of Combustion in a Piston Engine

2006-01-04014/3/2006

Significant improvement of engine performance can be achieved by ushering in a micro-electronic system to control the execution of combustion - an exothermic process whose sole purpose is to generate pressure. Hence, the primary feedback for the controller is provided by a pressure transducer. The activators are piezo-electrically activated pintle valves of MEMS type. The task of the micro-electronic processor is to provide an accurate feed-forward signal for the actuators on the basis of the information obtained from the feedback signal, within a time interval between consecutive cycles. Furnished here for this purpose is an algorithm for an interface module between the pressure sensor and the governor. Concomitantly, the gains thus attainable in the reduction of fuel consumption and curtailment of pollutant formation are thereby assessed. The implementation of this method of approach is illustrated by application to a HCCI engine.

Bitar, Eilyan Y., Oppenheim, Antoni K., Schock, Harold J.

Direct-Injected Hydrogen-Methane Mixtures in a Heavy-Duty Compression Ignition Engine

2006-01-06534/3/2006

A diesel pilot-ignited, high-pressure direct-injection of natural gas heavy-duty single-cylinder engine was fuelled with both natural gas and blends of 10% and 23% by volume hydrogen in methane. A single operating condition (6 bar GIMEP, 0.5 ϕ, 800 RPM, 40%EGR) was selected, and the combustion phasing was varied from advanced (mid-point of combustion at top-dead-center) to late (mid-point of combustion at 15°ATDC). Replacing the natural gas with hydrogen/methane blend fuels was found to have a significant influence on engine emissions and on combustion stability. The use of 10%hydrogen was found to slightly reduce PM, CO, and tHC emissions, while improving combustion stability. 23%hydrogen was found to substantially reduce CO and tHC emissions, while slightly increasing NOx. The greatest reductions in CO and tHC, along with a significant reduction in PM, were observed at the latest combustion timings, where combustion stability was lowest. The high hydrogen-content fuel was found to reduce the ignition delay of the gaseous jet by approximately 20%, without influencing the ignition delay of the diesel pilot. The results were generally consistent at all combustion timings tested, and were found to be insensitive to injection pressure.

McTaggart-Cowan, G.P., Jones, H.L., Rogak, S.N., Bushe, W.K., Hill, P.G., Munshi, S.R.

Fast Response Measurement of Combustion Air to Fuel Ratio for Stratified Two-Stroke Engines

2005-32-010910/12/2005

Due to emission regulations for hand-held power tools more and more stratified-charge two-stroke engines enter into the market [Sawada et al. 1998, Zahn et al. 2000]. These engines require investigations and treatment for tuning the transient behaviour that are beyond the methods of the tuning for conventional engines. Especially the in-cylinder air-to-fuel-ratio cannot be determined from simple exhaust gas analysis any more. This paper presents an exhaust gas sampling system to enable the use of a standard lambda meter for a fast response measurement of air to fuel ratio out of the combustion chamber. The gas is sampled by means of a small restriction directly out of the combustion chamber. In case of miss-fire the hydrocarbon concentration in the sample is too high for the lambda sensor. With a dilution or a pre-converter system the hydrocarbon concentration can be adjusted to the range of the lambda sensor. Verification has been done with several tests. The air to fuel ratio in combustion is a key issue to tune the transient behaviour and to meet all customer requirements of the engine performance.

GEYER, Klaus, HALLÉ, Christine, ROßKAMP, Heiko

Effect of Compression Ratio on Stratified-Charge Direct- Injection Gasoline Combustion

2005-01-01004/11/2005

Charge cooling due to fuel evaporation in a direct-injection spark-ignition (DISI) engine typically allows for an increased compression ratio relative to port fuel injection (PFI) engines. It is clear that this results in a thermal efficiency improvement at part load for homogenous-charge DISI engines. However, very little is known regarding the effect of compression ratio on stratified charge operation. In this investigation, DISI combustion data have been collected on a single cylinder engine equipped with a variable compression ratio feature. The results of experiments performed in stratified-charge direct injection (SCDI) mode show that despite its over-advanced phasing, thermal conversion efficiency improves with higher compression ratios. This benefit is quantified and dissected through an efficiency analysis. Furthermore, since the engine was equipped with both wall-guided DI and PFI systems, direct comparisons are made at part load for fuel consumption and emissions. Interestingly, combustion efficiency deteriorates in SCDI mode as compression ratio increases, albeit not due to crevice loading as is the case in PFI operation. Mechanisms for the observed hydrocarbon emissions behavior are suggested for change in load and compression ratio. The conclusions reached in this investigation provide an experimental basis for adequately selecting a compression ratio in SCDI engines.

Muñoz, Rubén H., Han, Zhiyu, VanDerWege, Brad A., Yi, Jianwen

Evaluation of Combustion Velocities in Bi-fuel Engines by Means of an Enhanced Diagnostic Tool Based on a Quasi-Dimensional Multizone Model

2005-01-02454/11/2005

The burned-gas propagation process has been characterized in two bi-fuel engines by means of a combustion diagnostic tool resulting from the integration of an original multizone heat-release model with a CAD procedure for the burned-gas front geometry simulation. Burned-gas mean expansion speed ub, mean gas speed ug and burning velocity Sb were computed as functions of crank angle and burned-gas radius for a wide range of engine speeds (n = 2000-5500 rpm), loads (bmep = 200-790 kPa), relative air-fuel ratios (RAFR = 0.80-1.60) and spark advances (SA ranging from 8 deg retard to 8 deg advance from MBT), under both gasoline and CNG operations. Finally, the influence of intake runner and combustion chamber geometries on flame propagation process was investigated. Main results show that Sb is generally comparable for the engine running on both gasoline and CNG, at the same engine speed and load, under stoichiometric and MBT operations. In fact, higher temperatures and pressures of the unburned-gas ahead of the flame front under CNG fuelling compensate for natural gas lower laminar-burning speed SL at reference conditions. The tested intake runner sets showed to exert a minor effect on burned-gas propagation. On the contrary, combustion chamber shape and spark plug positioning strongly influenced combustion process. Finally, the ratio of Sb to SL was analyzed as a function of engine operating variables during the rapid-burning interval.

d'Ambrosio, S., Misul, D., Spessa, E., Vassallo, A.

Combustion Characteristics of a Spray-Guided Direct-Injection Stratified-Charge Engine with a High-Squish Piston

2005-01-19374/11/2005

This work describes an experimental investigation on the stratified combustion and engine-out emissions characteristics of a single-cylinder, spark-ignition, direct-injection, spray-guided engine employing an outward-opening injector, an optimized high-squish, bowled piston, and a variable swirl valve control. Experiments were performed using two different outward-opening injectors with 80° and 90° spray angles, each having a variable injector pintle-lift control allowing different rates of injection. The fuel consumption of the engine was found to improve with decreasing air-swirl motion, increasing spark-plug length, increasing spark energy, and decreasing effective rate of injection, but to be relatively insensitive to fuel-rail pressure in the range of 10-20 MPa. At optimal injection and ignition timings, no misfires were observed in 30,000 consecutive cycles. Multiple pulsing of the injector did not improve upon the single injection-pulse results either by changing the timing of the injection process or by changing the dwell time between injection events.

Szekely, Gerald A., Alkidas, Alex C.

PIV In-Cylinder Flow Measurements of Swirl and the Effect of Combustion Chamber Design

2004-01-19526/8/2004

Particle Image Velocimetry (PIV) experiments were performed on single-cylinder versions of a 0.375 L/cylinder and a 0.5 L/cylinder engines from the same engine class to determine the differences in swirl flow between the two engines. Two engine speeds (750 and 1500 rpm), manifold pressures (75 kPa and 90 kPa) and valve timings (maximum overlap and with the intake valve 20° retarded from the max overlap position) were examined. The swirl ratio (SR) and mean velocity (|V|) were calculated at BDC for every case in the mid-stroke plane and the fluctuation velocity (U') calculated for the 1500 rpm / 90 kPa / maximum overlap case. The in-cylinder velocities do not differ by the expected ratio of mean piston speed caused by differences in the engine stroke. The smaller engine was expected to have lower in-cylinder velocities and SRs due to a shorter stroke and lower piston speeds but instead has SR and |V| levels that are the same or higher than the larger engine. In addition, the fluctuation velocities between the two engines are essentially identical. The values of U´ exhibit the proper scaling with engine speed but show only minor differences between the two engines. Examination of the flow fields show that the intake jet from the smaller engine is stronger. The smaller intake valves of the 0.375 L engine cause higher velocities in the intake flow. Also, the position of the intake valves and the relative spacing of the valve edges lead the smaller engine to have an advantage in swirl formation.

Alger, Terry, McGee, Jeff, Gallant, Erica, Wooldridge, Steve

Future General Aviation Piston Engines and Fuels - An Integrated Approach

2004-01-18104/20/2004

The continued availability of leaded specialty aviation gasolines remains as an item of crucial importance in the near-term future of general aviation; however, the development of new piston engines capable of operation with other transportation fuels available in large pools is considered an indispensable element in the long-range survival of the industry. This paper offers a road map that while allowing the continued utilization of the current fleet of piston aircraft, sets the stage for a transition to new piston powerplants and associated aircraft, compatible with widely available transportation fuels such as motor gasoline based aviation fuels for the lower and some medium performance aircraft, and aviation turbine fuels for the balance of medium and high performance airplanes. The proposed fuels and associated aircraft engines transition road map represents an integrated approach that covers the entire family of future general aviation products, in contrast with current fragmented efforts that ignore the small volume and wide world dispersal of this market. Transportation fuels likely to remain available around the world well into the future, determine the characteristics and combustion technologies of future engines. A discussion of said engine technologies, including emerging new combustion concepts, power management and advanced essential engine accessory systems is included in this document. This paper reflects generalized results of extensive studies and related supportive research activities on current typical general aviation fuels and engines, and on fuels and experimental engines envisioned to support the industry during the next 50 years.

Gonzalez, Cesar, Jesik, Richard L.

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