Homogeneous Charge Combustion Research Articles

Numerical investigation for enhancing HCCI combustion characteristics in DI-CI engine fueled with butanol/diesel blends

The fast depletion of fossil fuels and the hazardous emissions associated with the use of fossil fuels in IC engines is driving the research in the area of renewable fuels. Homogeneous charge combustion ignition (HCCI) is a new mode of engine combustion technology, used for reducing the emissions without compromising the engine performance. The combination of HCCI and alcohol/diesel blends has the potential to simultaneously address the twin problems of depletion of fossil fuels and engine emissions. Butanol is an attractive biofuel, which is produced from agriculture wastes such as sugar cane bagasses and corn stalk etc. This paper presents numerical and modeling analysis on the emission and performance characteristics of a direct injection- compression ignition (DI-CI) engine operated with butanol/diesel blends. Numerical analysis was carried out using CONVERGE CFD software. Response surface methodology (RSM) was used in developing the response models for three output parameters, viz., nitrogen oxides (NOx), soot emissions and indicated specific fuel consumption (ISFC), in terms of the four input parameters, viz., compression ratio (CR), start of injection (SOI), fuel injection pressure (FIP) and exhaust gas recirculation (EGR). Numerical experiments were conducted by varying these four input parameters, i.e., CR from 14 to 19, FIP from 200 to 280 bar, EGR from 0% to 30% and SOI from 17° to 29° CA bTDC, and with four butanol/diesel blends (0, 20%, 30% and 40% of butanol-by volume, designated as Bu00, Bu20, Bu30 and Bu40). The optimum combination of the input parameters for the four test fuels were found with the objective of minimizing the three output parameters (i.e., ISFC, soot and NOx) using desirability approach. The homogeneity of the air-fuel mixture was estimated using equivalence ratio distribution index, i.e., Target fuel distribution index (TFDI). From the numerical analysis, it was found that the TFDI improved for the optimized case by 20.5%, 21.5%, 24.4% and 27.2% for Bu00, Bu20, Bu30 and Bu40 respectively as compared to their respective baseline configuration.

Experimental Investigation on Performance and Emission Characteristics of Diesel Lean Burn HCCI Engines

The purpose of this study is to analyse the effect of premixed diesel fumigation on the performance and emission characteristics of Homogeneous Charge Combustion Ignition (HCCI) engine and to optimize the diesel fumigation temperature. An experimental investigation was carried out on a single cylinder, four stroke, water cooled, port injected Kirloskar SVI engine. An electric air heater is fixed at the suction pipe. During the experimental study, the diesel fuel was premixed by port injector and get vaporized or fumigated by heated suction air. After the process of heating and premixing, the diesel has changed its phase and mixed with the air in the form of partially homogenous mixture. During the test, the engine was operated at different diesel fumigation temperature of 100 C, 110 C, 120 C, 130 C, 140 C and 150 C to assess the performance and emissions characteristics of the engine. It is observed that the diesel fumigation has made the huge impact on NOx and smoke formation. The emission of NOx and smoke were decreased simultaneously about 10% and 16% compared to the compression ignition engine. Moreover, this engine has produced high amount of CO and HC emissions at low fumigation temperature and also reduced the high fumigation temperature. The suction air temperatures of 120ï‚°C and 130ï‚°C operated under HCCI engine were found to produce lesser NOx and smoke emissions. Moreover, the engine fuel consumption was increased due to the low volumetric efficiency and also slightly affected the brake thermal efficiency.

Potential of direct-injection for the improvement of homogeneous-charge combustion in spark-ignition natural gas engines

The direct-injection has been considered as a way to improve the performance of conventional spark-ignition natural gas engines with the port-fuel-injection by increasing the engine volumetric efficiency. However, insufficient attention has been paid to the potential of direct-injection for the combustion and thermal efficiency improvement of homogeneous-charge combustion in natural gas engines that can be achieved by the spray-induced turbulence enhancement of the in-cylinder fuel–air mixture. The current study investigates the engine thermal efficiency, combustion speed, combustion stability and hydrocarbon emissions of a direct-injection natural gas engine under varied injection timings, and compares the combustion characteristics of the direct-injection with those of port-fuel-injection. Then, a particular engine operation scheme (port-fuel-injection of natural gas and direct-injection of nitrogen) is applied to evaluate the potential of spray-induced turbulence on the thermal efficiency improvement in the homogeneous-charge combustion mode. The results showed that the direct-injection could improve the engine combustion speed, combustion stability and thermal efficiency in low-load conditions as a result of enhanced in-cylinder turbulence at retarded injection timings. Meanwhile, the direct-injection decreased the engine thermal efficiency in high-load conditions and increased the hydrocarbon emissions regardless of the engine load condition due to the deteriorated mixture homogeneity. When the in-cylinder turbulence and mixture homogeneity were both achieved, a few percent of thermal efficiency improvement was obtained by the direct-injection, and the improvement rate increased as the engine load decreased.

Characteristics of Early Flame Development in a Direct-Injection Spark-Ignition CNG Engine Fitted with a Variable Swirl Control Valve

An experimental study was conducted to investigate the effect of the structure of the induction flow on the characteristics of early flames in a lean-stratified and lean-homogeneous charge combustion of compressed natural gas (CNG) fuel in a direct injection (DI) engine at different engine speeds. The engine speed was varied at 1500 rpm, 1800 rpm and 2100 rpm, and the ignition timing was set at a 38.5° crank angle (CA) after top dead center (TDC) for all conditions. The engine was operated in a partial-load mode and a homogeneous air/fuel charge was achieved by injecting the fuel early (before the intake valve closure), while late injection during the compression stroke was used to produce a stratified charge. Different induction flow structures were obtained by adjusting the swirl control valves (SCV). Using an endoscopic intensified CCD (ICCD) camera, flame images were captured and analyzed. Code was developed to analyze the level of distortion of the flame and its wrinkledness, displacement and position relative to the spark center, as well as the flame growth rate. The results showed a higher flame growth rate with the flame kernel in the homogeneous charge, compared to the stratified combustion case. In the stratified charge combustion scenario, the 10° SCV closure (medium-tumble) resulted in a higher early flame growth rate, whereas a homogeneous charge combustion (characterized by strong swirl) resulted in the highest rate of flame growth.

Thermal design of methane steam reformer with low-temperature non-reactive heat source for high efficiency engine-hybrid stationary fuel cell system

In hybrid fuel cell systems, the fuel-lean anode-off gas is very useful to improve the system efficiency via additional power generation or utilization of thermal energy for heating up of auxiliary devices. In this study, the thermal energy of the hybrid systems is firstly utilized in homogeneous charge combustion engine for additional power and is then supplied to heat up the external reformer. Different from other hybrid fuel cell systems, it is very difficult to utilize heat energy of exhausted gas from engine due to its low temperature characteristics. This study is concentrated on the computation analysis of external methane steam reformers with engine out exhausted gases. Computational model is validated with experiment and parametric study is conducted. Results show that the temperature uniformity of the longitudinal and radial directions is crucial for the methane conversion efficiency. Additionally, the methane conversion rate also depends on the performance of tube-side heat transfer. When the total methane flow is fixed, the methane conversion rate shows trade-off with increasing steam-to-carbon ratio (SCR). Finally, the sensitivity study shows that heat transfer area and reactor length are dominant parameters for steam reforming with engine out exhausted gases.

Development of High Efficiency and Low Emission Low Temperature Combustion Diesel Engine with Direct EGR Injection

Focus on energy and environmental sustainability policy has put automotive research & development directed to developing high efficiency and low pollutant power train. Diffused flame controlled diesel combustion has reach its limitation and has driven R&D to explore other modes of combustions. Known effective mode of combustion to reduce emission are Low temperature combustion (LTC) and homogeneous charge combustion ignition by suppressing Nitrogen Oxide(NOx) and Particulate Matter (PM) formation. The key control to meet this requirement are chemical composition and distribution of fuel and gas during a combustion process. Most research to accomplish this goal is done by manipulating injected mass flow rate and varying indirect EGR through intake manifold. This research paper shows viable alternative direct combustion control via co-axial direct EGR injection with fuel injection process. A simulation study with OpenFOAM is conducted by varying EGR injection velocity and direct EGR injector diameter performed with under two conditions with non-combustion and combustion. n-heptane (C7H16) is used as surrogate fuel together with 57 species 290 semi-detailed chemical kinetic model developed by Chalmers University is used for combustion simulation. Simulation result indicates viability of co-axial EGR injection as a method for low temperature combustion control.

Trend and future of diesel engine: Development of high efficiency and low emission low temperature combustion diesel engine

Stringent emission policy has put automotive research & development on developing high efficiency and low pollutant power train. Conventional direct injection diesel engine with diffused flame has reached its limitation and has driven R&D to explore other field of combustion. Low temperature combustion (LTC) and homogeneous charge combustion ignition has been proven to be effective methods in decreasing combustion pollutant emission. Nitrogen Oxide (NOx) and Particulate Matter (PM) formation from combustion can be greatly suppressed. A review on each of method is covered to identify the condition and processes that result in these reductions. The critical parameters that allow such combustion to take place will be highlighted and serves as emphasis to the direction of developing future diesel engine system. This paper is written to explore potential of present numerical and experimental methods in optimizing diesel engine design through adoption of the new combustion technology.

Vaporisation characteristics of methanol, ethanol and heptane droplets in opposed stagnation flow at low temperature and pressure

A computational model is developed and applied to study the vaporisation behaviour of three liquid fuels. This fundamental study is motivated by a need to understand how the performance of direct-injection-spark-ignition (DISI) engines may be affected by changes in fuel composition, especially alcohols. Currently, most DISI engines are designed for homogeneous-charge combustion, where the in-cylinder fuel injection, vaporisation and mixing is accomplished during the intake and early in the compression process. Thus the temperature and pressure are low, compared to post-compression conditions. The two-phase axisymmetric model is based upon an ideal opposed stagnation flow field. Liquid droplets are carried in one air stream that is met by an opposed air flow. Because of stagnation-flow similarity, the mathematical model can be represented as a one-dimensional boundary-value problem. Results show significant differences between methanol, ethanol and heptane fuels, which have potentially important impacts on the design and modification of fuel-injection systems for direct-injection engines with alternative fuels.

직접분사식 가솔린엔진의 분사 비율에 따른 연소특성에 관한 연구

Recently, the important issues of gasoline engine are to reduce the fuel consumption and emission. Thus, many researchers are studying the technology to solve these problems. One approach of these issues is to achieve homogeneous charge combustion and stratified change combustion with various injection strategy. In this study, the combustion characteristics of DISI engine accrding to injection strategy were examined. The effect of injection timing on lean limit A/F were investigated using dual DISI single cylinder. The results show that the engine operation region of dual DISI type engine is larger than that of PFI and DISI type engine cases. Especially, late injection is very effective to extend the operation region more than any other injection timings. In addition, the results show that when the DISI injection ratio is increase, leam limit A/F is improved. It means that the dual injection system car meet with emission regulations and reduce the fuel consumption. Also, combustion pressure of dual injection system is much higher than PFI and DISI injection.

Experimental Study on the Stratified and Homogeneous Charge of a Direct-Injection Spark Ignition Methanol Engine

Based on the gasoline direct-injection spark ignition (DISI) engine technologies and methanol fuel characteristics, a complex-guided multi-hole spray coupled with induction swirl and chamber-wall-guided stratified-charge combustion system for a DISI methanol engine was developed. It was retrofitted from a four-cylinder diesel engine with a compression ratio of 14. It was developed to run on methanol in stratified-charge and homogeneous-charge combustion modes; under part-load operating conditions, stratified-charge combustion is adopted to improve fuel economy while, under high- and full-load conditions, the homogeneous-charge combustion mode is adopted for the purpose of a higher power output. Under both combustion modes, the key parameters of the combustion system were matched and optimized respectively. The operating map for both combustion modes was obtained. Then, the engine power performance, emissions, and combustion characteristics were studied. The power output of the developed methanol engine is higher than that of the original diesel engine. By using the stratified combustion mode under low-load conditions, the engine fuel economy (the brake thermal efficiency) is improved; the stratified-charge combustion of methanol performed relatively well with acceptable values of the coefficient of the cyclic variation in the indicated mean effective pressure. The smoke and nitrogen oxide emissions from the DISI methanol engine are both reduced simultaneously and significantly.

Diffusion- and Homogeneous-Charge Combustion of Volatile Ethers in a Compression Ignition Engine

The combustion characteristics of several volatile ether molecules were studied under diffusion and homogeneous charge combustion modes in a compression ignition engine. Volatile ethers of low molecular mass are organic molecules that could be used as fuel for compression ignition engines. The physical and chemical characteristics of such ethers comprise high oxygen content, high volatility, and low viscosity, all of which are conducive to high thermal efficiencies and low pollutant emission during engine operation. It is thought that sootless combustion may be achieved in diffusion flames of high-speed direct injection diesel engines with some volatile ethers, due to their high oxygen content. The formation of oxides of nitrogen from the combustion of ethers may be almost eliminated by the use of lean, homogeneous charge compression ignition combustion, for which these fuel molecules are particularly suitable due to their high volatility. The first part of the experiments examines the combustion characte...

New Reduced Chemical Mechanism for Homogeneous Charge Combustion Ignition Combustion Investigation of Primary Reference Fuels

A reduced chemical mechanism for primary reference fuels (PRFs) and their mixtures has been developed to investigate the homogeneous charge combustion ignition (HCCI) combustion and emissions (uHC, CO, and NOx) processes. The reduced mechanism involves 42 species undergoing 62 reactions and has been validated against experiments under engine relevant conditions. First, the ignition delay time predicted by the reduced mechanism has been compared with shock tube experiments, and good agreement has been obtained for the PRF100, PRF90, PRF80, PRF60, and PRF0 fuels over the temperature range 667-1250 K at stoichiometric conditions. Second, the ignition delay time and burn rate has been validated against a rapid compression machine over the equivalence ratio range 0.2-0.5 and the initial temperature range 305-341 K for PRF90 fuel. Third, the ignition delay times and NOx emissions have been compared with HCCI engine experiments and good agreement has been obtained for the PRF90, PRF75, PRF50, and PRF25 fuels.

LPG-DME 성층혼합 압축착화 엔진

The combustion characteristics of a liquefied petroleum gas-di-methyl ether (LPG-DME) compression ignition engine was investigated under homogeneous charge and stratified charge conditions. LPG was used as the main fuel and injected into the combustion chamber directly. DME was used as an ignition promoter and injected into the intake port. Different LPG injection timings were tested to verify the combustion characteristics of the LPG-DME compression ignition engine. The combustion was divided into three region which are homogeneous charge, stratified charge, and diffusion flame region according to the injection timing of LPG. The hydrocarbon emission of stratified charge combustion was lower than that of homogeneous charge combustion. However, the carbon monoxide and nitrogen oxide emission of stratified charge combustion were slightly higher than those of the homogeneous charge region. The indicated mean effective pressure was reduced at stratified charge region, while it was almost same level as the homogeneous charge combustion region at diffusion combustion region. The start of combustion timing of the stratified charge combustion and diffusion combustion region were advanced compared to the homogeneous charge combustion. It attributed to the higher cetane number and mixture temperature distribution which locally stratified. However, the knock intensity was varied as the homogeneity of charge was increased.

An experimental study of the combustion characteristics in SCCI and CAI based on direct-injection gasoline engine

Emissions remain a critical issue affecting engine design and operation, while energy conservation is becoming increasingly important. One approach to favorably address these issues is to achieve homogeneous charge combustion and stratified charge combustion at lower peak temperatures with a variable compression ratio, a variable intake temperature and a trapped rate of the EGR using NVO (negative valve overlap). This experiment was attempted to investigate the origins of these lower temperature auto-ignition phenomena with SCCI and CAI using gasoline fuel. In case of SCCI, the combustion and emission characteristics of gasoline-fueled stratified-charge compression ignition (SCCI) engine according to intake temperature and compression ratio was examined. We investigated the effects of air–fuel ratio, residual EGR rate and injection timing on the CAI combustion area. In addition, the effect of injection timing on combustion factors such as the start of combustion, its duration and its heat release rate was also investigated.

Modeling of stratified combustion in a direct-ignition, spark-ignition engine accounting for complex chemistry

Intake, mixing and combustion processes are simulated in a direct-injection gasoline engine for three substantially different running conditions, including two full loads with homogeneous charge combustion and a part load with stratified charge combustion. The turbulent Flame Speed Closure (FSC) model is implemented into the FIRE code for the three-dimensional simulations of the combustion processes which is the focus in the present paper. To take local mixture properties into account, a complex chemistry mechanism consisting of 100 species and 475 reactions is used to calculate the laminar flame speeds and chemical timescales required by the model. A large range of equivalence ratios, pressures, and temperatures are investigated and the combustion limits are determined. The FSC model is extended to capture the postflame oxidation between excess fuel from the rich mixture and excess air from the lean mixture. The modeling of the flow field, mixture composition, and combustion is compared with optical and pressure measurements in a test-rig engine showing good agreement. The simulation of the stratified charge combustion indicates that the major part of the unburned fuel after the combustion originates from the lean mixture. The calculated amount of unburned fuel is in good agreement with the measured HC emissions.

314 二元燃料予混合圧縮着火ディーゼル機関における排気特性(エンジンシステムII)

314 二元燃料予混合圧縮着火ディーゼル機関における排気特性(エンジンシステムII)

Study on homogeneous charge combustion diesel engine (3rd report) expansion of low NOx combustion region and its behavior Hisakazu Suzuki, Noriyuki Koike, Hajime Ishii, Masuo Odaka (Traffic Safety and Nuisance Research Institute, Ministry of Transport)

Study on homogeneous charge combustion diesel engine (3rd report) expansion of low NOx combustion region and its behavior Hisakazu Suzuki, Noriyuki Koike, Hajime Ishii, Masuo Odaka (Traffic Safety and Nuisance Research Institute, Ministry of Transport)

Comparison of fuel injection systems and a new combustion method for a direct injection two-stroke-cycle automobile engine

A study of a direct fuel injection 2-stroke engine as a new generation power unit was performed and concluded as follows. 1. (1) A comparison of fuel injection system candidates was made and the one-fluid high-pressure type was chosen. 2. (2) Adopting the high-pressure fuel system to a single-cylinder engine, stratified charge combustion was realized using the late injection. 3. (3) It was found that homogeneous charge combustion using the early injection would enable high power output. 4. (4) The “2-zone combustion” was also achieved by injecting the fuel twice within one cycle.

Study on homogeneous charge combustion diesel engine (1st report) analysis of combustion and emission behaviors of an experimental DI diesel engine with pre-mixed fuel Hisakazu Suzuki, Noriyuki Koike, Hajime Ishii, Matsuo Odaka (Traffic Safety and Nuisance Research Institute, Ministry of Transport)

Study on homogeneous charge combustion diesel engine (1st report) analysis of combustion and emission behaviors of an experimental DI diesel engine with pre-mixed fuel Hisakazu Suzuki, Noriyuki Koike, Hajime Ishii, Matsuo Odaka (Traffic Safety and Nuisance Research Institute, Ministry of Transport)

A thermochemical phase space for combustion in engines

The phase space introduced in this paper is based on the recognition that the combustion system is nonlinear, and takes advantage, therefore, of the classical concept of nonlinear mechanics: a space whose coordinates are all the dependent variables of the problem. In the case at hand, they consist of all the thermochemical parameters of the system. The dimension of this space is thus equal to the number of degrees of freedom. The authors name it the Le Chatelier Space. Its major asset lies in providing a map for the global effects of the thermochemical processes occurring in the physical space of the combustion chamber, expressed in terms of trajectories or manifolds. Obtained thereby is an analytical insight into the effective mechanism of the combustion system. Application of the method is illustrated by the evaluation of advantages one can accrue on this basis for a premixed charge engine. It is shown, in particular, that if, instead of a throttled homogeneous charge combustion, the exothermic process is executed in a fireball mode of a direct injection stratified charge system, the engine can be rendered the ability for part-load operation at wide-open throttle, with significant gains in fuel economy and concomitant reduction inmore » pollutant emissions. Such a mode of combustion takes place within large-scale vortex structures generated and sustained by pulsed jets.« less