Improvements in Efficiency and Mixture Formation for an Innovative Diesel HCCI Concept

2009 ◽  
Author(s):  
E. Musu ◽  
R. Rossi ◽  
R. Gentili
Keyword(s):  
Combustion Process ◽  
Pressure Rise ◽  
Pollutant Emissions ◽  
Spontaneous Ignition ◽  
Exhaust Gas ◽  
Mixture Formation ◽  
Hcci Combustion ◽  
Gas Recirculation ◽  
Transfer Flow ◽  
Homogeneous Charge

Homogeneous-charge, compression-ignition (HCCI) combustion is triggered by spontaneous ignition in dilute homogeneous mixtures. The combustion rate must be reduced by suitable solutions such as high rates of Exhaust Gas Recirculation (EGR) and/or lean mixtures. HCCI is considered to be a very effective way to reduce engine pollutant emissions, however only a few production engines have been built. HCCI combustion currently cannot be extended to the whole engine operating range, especially to high loads, since the use of EGR displaces air from the cylinder, limiting engine mean effective pressure, thus the engine must be able to operate also in conventional mode. This paper concerns a study of an innovative concept to control HCCI combustion in diesel-fueled engines. The concept consists in forming a pre-compressed homogeneous charge outside the cylinder and in gradually admitting it into the cylinder during the combustion process. In this way, combustion can be controlled by the transfer flow rate, and high pressure rise rates, typical of standard HCCI combustion, can be avoided. This new combustion concept has been called Homogenous Charge Progressive Combustion (HCPC). This paper concerns CFD analysis focused on improving efficiency and reducing pollutant emissions considering a new HCPC engine configuration. Results show an indicated efficiency around 45% and a consistent reduction of soot emission compared to conventional diesel engine.

A Preliminary Study Towards an Innovative Diesel HCCI Combustion

2007 ◽  
Author(s):  
D. Tamagna ◽  
E. Musu ◽  
R. Gentili
Keyword(s):  
Combustion Process ◽  
Pollutant Emissions ◽  
Spontaneous Ignition ◽  
Exhaust Gas ◽  
Compression Ignition ◽  
Pressure Gradients ◽  
Hcci Combustion ◽  
Preliminary Study ◽  
Gas Recirculation ◽  
Innovative Concept

Homogeneous-charge, compression-ignition (HCCI) combustion is triggered by spontaneous ignition in diluted homogeneous mixtures and has a gradual trend thanks to suitable solutions. It is considered a very effective way to reduce engine pollutant emissions, however only experimental prototypes have been based on this concept, except for a few small two-stroke engines. HCCI combustion is feasible with fuels both for S.I. and for C.I. engines, but currently it does not cover the whole engine operating field, thus the engine must be built to operate also as a conventional engine. In order to obtain a gradual combustion and not a simultaneous reaction (as it would be in spontaneously ignited homogeneous mixture), lean mixture is used and appropriate solutions, as Exhaust Gas Recirculation (EGR), are necessary. However, the admission of exhaust gas into the cylinder goes to detriment of engine maximum mean effective pressure. This paper concerns a preliminary study of an innovative concept to control HCCI combustion in Diesel-fuelled engines, apart from exhaust gas presence, the function of which is limited to NOx emission control. The main purpose of the research is the obtaining of Diesel HCCI combustion also with high mean effective pressures rendering the combustion behaviour more controllable as well. The concept consists in forming a pre-compressed homogenous charge outside the cylinder and in gradually admitting it into the cylinder during the combustion process. In this way, combustion can be controlled by the flow rate transfer and high pressure gradients, typical of common HCCI combustion, can be limited as well. A first analysis has been done, considering a cylinder filled with a perfectly stirred mixture of air and diesel fuel through a transfer duct, only to test the validity of the concept, regardless of which effective solution will be adopted. Both Two and Four Stroke operations have been considered to realize the concept. Results in terms of pressure, heat release rate, temperature and emission production have pointed out the validity of the concept. Especially the Two Stroke solution produces more soot than the conventional Diesel, pointing out that the air-fuel mixing is probably not optimized. Regarding NOx emissions, both the proposed solutions give better results than the conventional Diesel engine.

Effect of intake hydrogen addition on performance and emission characteristics of a diesel engine with exhaust gas recirculation

2011 ◽  
Vol 225 (8) ◽  
pp. 1919-1925 ◽  
Author(s):  
Y J Qian ◽  
C J Zuo ◽  
J Tan ◽  
H M Xu
Keyword(s):  
Diesel Engine ◽  
Pressure Rise ◽  
Engine Performance ◽  
Exhaust Gas Recirculation ◽  
Pollutant Emissions ◽  
Exhaust Gas ◽  
Performance And Emission ◽  
Hydrogen Addition ◽  
Hydrogen Enrichment ◽  
Gas Recirculation

This article presents the potential of improving engine performance and pollutant emissions of a ZS195 Diesel engine by exhaust gas recirculation (EGR) and intake hydrogen enrichment. The effect of EGR level and hydrogen addition on the engine performance and pollutant emissions has been investigated through detailed experiments at rated speed. The experimental results have shown that when EGR level is constant, the peak pressure and maximum rate of pressure rise increase with the increase of hydrogen addition. The intake hydrogen enrichment can reduce HC, CO, and soot level and increase NOX emission, but EGR technique can offset this effect. The combustion speed and thermal efficiency increase with the increase of hydrogen addition when EGR technique has been adopted.

scholarly journals Effects of EGR and Alternative Fuels on Homogeneous Charge Compression Ignition (HCCI) Combustion Mode

2021 ◽  
Vol 16 (2) ◽  
pp. 135-144
Author(s):  
Saliha Mohammed Belkebir ◽  
Benyoucef Khelidj ◽  
Miloud Tahar Abbes
Keyword(s):  
Alternative Fuels ◽  
Ignition Time ◽  
Combustion Process ◽  
Chemical Species ◽  
Pollutant Emissions ◽  
Combustion Mode ◽  
Hcci Combustion ◽  
Hcci Engines ◽  
Homogeneous Reactor ◽  
Gas Recirculation

We present in this article an analysis of the impacts of the exhaust gas recirculation (EGR) and alternative fuels on HCCI combustion mode. The objective is to reduce the pollutant emissions below the levels of established pollution standards. The ANSYS CHEMKIN-Pro software and the combined chemical kinetics mechanism were used to perform simulations for a closed homogeneous reactor under conditions relevant to HCCI engines. The calculation process is based on one single-zone in the combustion chamber. Numerical simulation has proven the ability of the models adopted, which use the essential mechanisms of the fuel combustion process, to reproduce, among other things, the evolution of the formation of chemical species. This study showed that adding hydrogen (H2) to methane (CH4) is an interesting alternative fuel because it reduces ignition time. It was concluded that an increase of EGR rate conducts to a slower combustion process, lower temperatures, and the reduction of nitrogen oxide (NOX) emissions.

The effect of axial charge stratification and exhaust gases on combustion ‘development’ in a homogeneous charge compression ignition engine

2008 ◽  
Vol 222 (11) ◽  
pp. 2171-2183 ◽  
Author(s):  
P G Aleiferis ◽  
A G Charalambides ◽  
Y Hardalupas ◽  
A M K P Taylor ◽  
Y Urata
Keyword(s):  
Exhaust Gas Recirculation ◽  
Injection Timing ◽  
Cylinder Wall ◽  
Exhaust Gas ◽  
Compression Ignition ◽  
Intake Valve ◽  
Stratified Charge ◽  
Hcci Combustion ◽  
Gas Recirculation ◽  
Homogeneous Charge

A high-swirl low-compression-ratio, optically accessed engine that was able to produce a stratified charge was used to investigate the differences in homogeneous charge compression ignition (HCCI) combustion and in the propagation of the autoignition front between a non-stratified and a stratified charge. Natural-light images were acquired using a fast camera to visualize HCCI combustion and to quantify the location of autoignition, the apparent ‘propagation speed’ of the autoignition front, and its variations between closed-valve injection timing (leading to a nearly homogeneous charge) and open-valve injection timing (leading to a strongly axially stratified charge), owing to temperature inhomogeneities that were introduced by utilizing a camshaft which allowed 40 per cent internal exhaust gas recirculation (iEGR). Experimental results show that, in the case without exhaust gas recirculation (EGR) and with closed-valve injection timing, autoignition started under the primary intake valve near the cylinder wall, while, in the case without EGR and with open-valve injection timing, autoignition started between the exhaust valve and the secondary intake valve, closer to the centre of the piston. With 40 per cent iEGR and closed-valve injection timing, autoignition started between the exhaust valve and the primary intake valve near the cylinder wall. These differences can be explained by the difference in the location of hot gases due to the injection timing or due to iEGR. Finally, without EGR, a ‘uniform’ autoignition front of HCCI combustion from the original sites of autoignition was observed compared with a more ‘random development’ of the autoignition front with 40 per cent iEGR. Strong local inhomogeneities (possibly a very rich mixture at a low temperature) could be present with 40 per cent iEGR.

A Numerical Study to Control the Combustion Performance of a Syngas-Fueled HCCI Engine at Medium and High Loads Using Different Piston Bowl Geometry and Exhaust Gas Recirculation

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Kabbir Ali ◽  
Changup Kim ◽  
Yonggyu Lee ◽  
Seungmook Oh ◽  
Kiseong Kim
Keyword(s):  
Numerical Study ◽  
Combustion Process ◽  
Pressure Rise ◽  
Fuel Mixture ◽  
Exhaust Gas Recirculation ◽  
Maximum Pressure ◽  
Exhaust Gas ◽  
Hcci Engine ◽  
Piston Bowl ◽  
Gas Recirculation

Abstract This study aims to analyze the effect of piston bowl geometry on the combustion and emission performance of the syngas-fueled homogenous charge compression ignition (HCCI) engine, which operates under lean air–fuel mixture conditions for power plant usage. Three different piston bowl geometries were used with a reduction of piston bowl depth and squish area ratio of the baseline piston bowl with the same compression ratio of 17.1. Additionally, exhaust gas recirculation (EGR) is used to control the maximum pressure rise rate (MPRR) of syngas-fueled HCCI engines. To simulate the combustion process at medium load (5 bar indicated mean effective pressure (IMEP)) and high loads of (8 and 10 bar IMEP), ansys forte cfd package was used, and the calculated results were compared with Aceves et al.’s Multi-zone HCCI model, using the same chemical kinetics set (Gri-Mech 3.0). All calculations were accomplished at maximum brake torque (MBT) conditions, by sweeping the air–fuel mixture temperature at the inlet valve close (TIVC). This study reveals that the TIVC of the air–fuel mixture and the heat loss rate through the wall are the main factors that influence combustion phasing by changing the piston bowl geometry. It also finds that although pistons B and C give high thermal efficiency, they cannot be used for the combustion process, due to the very high MPRR and NOx emissions. Even though the baseline piston shows high MPRR (23 bar/degree), it is reduced, and reveals an acceptable range of 10–12 bar/degree, using 30% EGR.

Combustion Characteristics of HCCI in Motorcycle Engine

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yuh-Yih Wu ◽  
Ching-Tzan Jang ◽  
Bo-Liang Chen
Keyword(s):  
Cylinder Head ◽  
Internal Combustion Engines ◽  
Peak Pressure ◽  
Pressure Rise ◽  
Combustion Characteristics ◽  
Hcci Combustion ◽  
Lower Maximum ◽  
Intake Air Heating ◽  
Gas Recirculation ◽  
Motorcycle Engine

Homogeneous charge compression ignition (HCCI) is recognized as an advanced combustion system for internal combustion engines that reduces fuel consumption and exhaust emissions. This work studied a 150 cc air-cooled, four-stroke motorcycle engine employing HCCI combustion. The compression ratio was increased from 10.5 to 12.4 by modifying the cylinder head. Kerosene fuel was used without intake air heating and operated at various excess air ratios (λ), engine speeds, and exhaust gas recirculation (EGR) rates. Combustion characteristics and emissions on the target engine were measured. It was found that keeping the cylinder head temperature at around 120–130°C is important for conducting a stable experiment. Two-stage ignition was observed from the heat release rate curve, which was calculated from cylinder pressure. Higher λ or EGR causes lower peak pressure, lower maximum rate of pressure rise (MRPR), and higher emission of CO. However, EGR is better than λ for decreasing the peak pressure and MRPR without deteriorating the engine output. Advancing the timing of peak pressure causes high peak pressure, and hence increases MRPR. The timing of peak pressure around 10–15 degree of crank angle after top dead center indicates a good appearance for low MRPR.

Measurement of Flame Frequency Response Functions Under Exhaust Gas Recirculation Conditions

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Joseph Ranalli ◽  
Don Ferguson
Keyword(s):  
Transfer Function ◽  
Carbon Capture ◽  
Transfer Functions ◽  
Combustion Process ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Flame Response ◽  
Gas Recirculation

Exhaust gas recirculation has been proposed as a potential strategy for reducing the cost and efficiency penalty associated with postcombustion carbon capture. However, this approach may cause as-yet unresolved effects on the combustion process, including additional potential for the occurrence of thermoacoustic instabilities. Flame dynamics, characterized by the flame transfer function, were measured in traditional swirl stabilized and low-swirl injector combustor configurations, subject to exhaust gas circulation simulated by N2 and CO2 dilution. The flame transfer functions exhibited behavior consistent with a low-pass filter and showed phase dominated by delay. Flame transfer function frequencies were nondimensionalized using Strouhal number to highlight the convective nature of this delay. Dilution was observed to influence the dynamics primarily through its role in changing the size of the flame, indicating that it plays a similar role in determining the dynamics as changes in the equivalence ratio. Notchlike features in the flame transfer function were shown to be related to interference behaviors associated with the convective nature of the flame response. Some similarities between the two stabilization configurations proved limiting and generalization of the physical behaviors will require additional investigation.

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