Fueled HCCI Engine Research Articles

Availability analysis of n-heptane and natural gas blends combustion in HCCI engines

One of the major problems associated with HCCI combustion engine application is lack of direct control for combustion timing. A proposed solution for combustion timing control is using a binary fuel blend in which two fuels with different auto-ignition characteristics are blended at various ratios on a cycle-by-cycle basis. The aim of this research is to investigate the exergy analysis of HCCI combustion when a blended fuel, which consists of n-heptane and natural gas, is used. In order to accomplish this task, a single-zone combustion model has been developed, which performs combustion computations using a complete chemical kinetics mechanism. The study was carried out with different percentages of natural gas in blended fuels and EGR (exhaust gas recirculation) ranging from about 45 to 85 percent and 0 to 40 percent, respectively. The results reveal that, when mass percentage of natural gas increases, exergy destruction is decreased increasing the second-law efficiency. Introducing EGR into the intake charge of dual fuel HCCI engine up to some stage (optimum value) enhances the second-law performance of the engine in spite of a reduction in work.

Experimental study of biogas combustion in an HCCI engine for power generation with high indicated efficiency and ultra-low NO x emissions

Combustion parameters and the main exhaust emissions from a biogas fueled HCCI engine are investigated in this study. The study was conducted on a 4-cylinder, 1.9L Volkswagen TDI Diesel engine, which was modified to run in HCCI mode with biogas by means of inlet charge temperature control, boosted intake pressure, and a sonic flow device upstream of the inlet manifold to control biogas composition and the equivalence ratio. For simulating typical power generation conditions, the engine was coupled to an AC motor generator operating at 1800 rpm. In the startup process, gasoline was used in HCCI mode for all cylinders. During the tests, biogas was used in cylinders 2 and 3, and gasoline was used in cylinders 1 and 4 to allow for more stable engine coolant and oil temperatures. The tests were performed through an experimental factorial design to evaluate the effect of inlet charge temperature, boost pressures, and the equivalence ratio of the biogas–air mixture on HCCI combustion parameters and emissions. For biogas at lower equivalence ratios, slight increases in inlet charge temperature and boost pressures enhanced combustion parameters and reduced CO and HC emissions. For biogas at higher equivalence ratios, the effects of inlet charge conditions on HCCI combustion and CO and HC emissions were attenuated; however, ringing intensities and NO x emissions were increased with higher inlet charge temperature and higher boosted pressures. The maximum gross indicated mean effective pressure was 7.4 bar, the maximum gross indicated efficiency was close to 45%, and NO x emissions were below the US-2010 limit of 0.27 g/kW h. These results show that a biogas fueled HCCI engine is a promising option in stationary power generation applications, meeting high efficiency and ultra-low NO x emissions.

Towards a Detailed Soot Model for Internal Combustion Engines

The formation of soot in an n-heptane fuelled HCCI engine, operated at a rich equivalence ratio of 1.93, has been studied by means of in-cylinder snatch sampling as well as by applying a new engine model, which features a highly detailed description of soot. The study has been conducted by scientists of the Department of Chemical Engineering and Biotechnology at Cambridge University (UK), the Institute of Clean and Secure Energy at the University of Utah (USA), Ibiden and Toyota. This new computationally efficient model can provide aggregate and primary particle size distribution functions and detailed information on aggregate morphology and chemical composition such as images similar to those produced with TEMs.

An Experimental Study on the Effect of Premixed and Equivalence Ratios on CO and HC Emissions of Dual Fuel HCCI Engine

In this study, effects of premixed and equivalence ratios on CO and HC emissions of a dual fuel HCCI engine are investigated. Tests were conducted on a single-cylinder engine with compression ratio of 17.5. Premixed gasoline is provided by a carburetor connected to intake manifold and equipped with a screw to adjust premixed air-fuel ratio, and diesel fuel is injected directly into the cylinder through an injector at pressure of 250 bars. A heater placed at inlet manifold is used to control the intake charge temperature. Optimal intake charge temperature results in better HCCI combustion due to formation of a homogeneous mixture, therefore, all tests were carried out over the optimum intake temperature of 110-115 oC. Timing of diesel fuel injection has a great effect on stratification of in-cylinder charge and plays an important role in HCCI combustion phasing. Experiments indicated 35 BTDC as the optimum injection timing. Varying the coolant temperature in a range of 40 to 70 oC, better HCCI combustion was achieved at 50 oC. Therefore, coolant temperature was maintained 50 oC during all tests. Simultaneous investigation of effective parameters on HCCI combustion was conducted to determine optimum parameters resulting in fast transition to HCCI combustion. One of the advantages of the method studied in this study is feasibility of easy and fast transition of typical diesel engine to a dual fuel HCCI engine. Results show that increasing premixed ratio, while keeping EGR rate constant, increases unburned hydrocarbon (UHC) emissions due to quenching phenomena and trapping of premixed fuel in crevices, but CO emission decreases due to increase in CO to CO2 reactions.

Effects of fuel additives on ignition timing of methane fuelled HCCI engine

AbstractThe control of ignition is one of the most critical issues in HCCI engines. It has been shown that using fuel additives play a significant role in reducing engine emission to satisfy the mandated EPA regulation. In this paper, the effect of additives such as hydrogen (H2), hydrogen peroxide (H2O2), formaldehyde (CH2O) and ethane (C2H6) on the control of ignition in natural gas HCCI engines has been investigated. The SENKIN code used to simulate the in-cylinder chemical reactions. The overall engine was modelled in the engine cycle simulation code, GT-Power. Then, the combustion results from SENKIN were transferred to the engine model to investigate the overall engine performance characteristics of the HCCI engine using a developed interface code that linked the SENKIN to GT-Power. The computational model was validated by available experimental data. The results showed that the calculated data were relatively in good agreement with the experimental data. It was found that an additive free mixture w...

Integration of Fuel Auto-ignition Characteristics and HCCI Engine Operation

Integration of Fuel Auto-ignition Characteristics and HCCI Engine Operation

3101 メタン混合に対するDME-HCCI燃焼の実験的研究(G07-1 燃焼制御(1),G07 エンジンシステム)

The HCCI is a promising combustion process for simultaneously obtaining low NOx and PM emissions and high thermal efficiency. With the engine technology currently available, however, the HCCI operating region is limited and compression ignition timing is difficult to control. One side, DME has attracted interest as a potential alternative fuel for compression ignition engines. This fuel has a negative temperature coefficient region in which the ignition delay is not shortened even if the compression-induced temperature rises. DME has characteristics which is producing multi-stage heat release through both low and high temperature combustion. Based on the experimental data, this paper discusses the effect of the methane mixture on combustion in a DME fueled HCCI Engine.

Effect of Internal Exhaust Gas Recirculation on Performance and Emissions from a Natural-Gas Fueled Homogeneous Charge Compression Ignition Engine

Besides the narrow operation range, natural gas fueled HCCI engine requires higher compression ratio and pre-heated air due to the low Cetan number. In this study, influences of the internal EGR ratio on the performance and the emissions of a single cylinder engine were investigated. Although the internal EGR lowers the permissible temperature of the intake air, it also decrease the indicated thermal efficiency. This is attributed to the increase of heat loss and pumping loss. The effect of internal EGR varies depending on the air temperature. At high air temperature, it increase the combustion duration. By contrast, at low temperature it increases the inner gas temperature at the start of compression phase, and thus, decreases the combustion duration. Under the turbo charged condition, the indicated thermal efficiency and the indicated mean effective pressure are increased. Those are attributed to the decreases of the heat loss.

2217 Effects of Rapid Expansion and EGR on NOx Formation of DME under Diesel Engine Condition

DME (Di-Methyl Ether) has been considered as one of the promising alternative fuels for diesel engines since it emits no smoke and low level of THC, Nox level, however, remains still a problem to be solved for DME fueled diesel engines. In this study, therefore, NOx reduction limitation has been investigated using a chemical kinetic simulation by changing EGR (Exhaust Gas Regulation) rate and engine speed for a DME fueled HCCI engine. From the obtained results, it is shown that Nox concentration decreases as the EGR rate increases when it is less than 30% at the speed of 1,500rpm. It is also shown that NOx concentration decreases monotonously as the engine speed increases.

96/03416 - RSYST: From nuclear reactor calculations towards a highly sophisticated scientific software integration environment

One of the major problems associated with HCCI combustion engine application is lack of direct control for combustion timing. A proposed solution for combustion timing control is using a binary fuel blend in which two fuels with different auto-ignition characteristics are blended at various ratios on a cycle-by-cycle basis.The aim of this research is to investigate the exergy analysis of HCCI combustion when a blended fuel, which consists of n-heptane and natural gas, is used. In order to accomplish this task, a single-zone combustion model has been developed, which performs combustion computations using a complete chemical kinetics mechanism.The study was carried out with different percentages of natural gas in blended fuels and EGR (exhaust gas recirculation) ranging from about 45 to 85 percent and 0 to 40 percent, respectively. The results reveal that, when mass percentage of natural gas increases, exergy destruction is decreased increasing the second-law efficiency. Introducing EGR into the intake charge of dual fuel HCCI engine up to some stage (optimum value) enhances the second-law performance of the engine in spite of a reduction in work.