A parametric study on natural gas fueled HCCI combustion engine using a multi-zone combustion model

Homogenous Charge Combustion Ignition (HCCI) is a good method for higher efficiency and to reduce NOx and particulate matter simultaneously in comparison to conventional internal combustion engines. In HCCI engines, there is no direct control method for auto ignition time. A common way to indirectly control the ignition timing in HCCI combustion engines is varying engine’s parameters which can affect the combustion. In this work, a parametric study on natural gas HCCI combustion is conducted in order to identify the effect of inlet temperature and pressure, compression ratio, equivalence ratio and engine speed on combustion and engine performance parameters. In this paper, two kinds of parameters will be discussed. First, in-cylinder pressure diagrams and variation of start of combustion which are combustion parameters will be presented and then the second category, indicated mean effective pressure and thermal efficiency which are performance parameters will be studied. A six zone model coupled with detailed chemical kinetics code is used to simulate HCCI combustion. Both heat and mass transfer was considered in the modeling procedure. Results revealed that among the considered parameters, the equivalence ratio and inlet pressure are the most valuable parameters which can improve the combustion and performance characteristics of the HCCI engine.     

Experimental and numerical study on the combustion characteristics of partially premixed charge compression ignition engine with dual fuel

The objective of this work is to investigate the effect of premixed fuel ratio on the combustion and emission characteristics in diesel engine by the experimental and numerical method. In order to investigate the effect of various factors such as the premixed ratio, EGR rate, and equivalence ratio on the exhaust gas from the premixed charge compression ignition diesel engine, the injection amount of premixed fuel is controlled by electronic port injection system. The range of premixed ratio between dual fuels used in this study is between 0 and 0.85, and the exhaust gas is recirclulated up to 30 percent of EGR rate.     

Performance, emission and combustion evaluation of soapnut oil-diesel blends in a compression ignition engine

Soapnut (Sapindus mukorossi) oil, a nonedible straight vegetable oil was blended with petroleum diesel in various proportions to evaluate the performance and emission characteristics of a single cylinder direct injection constant speed diesel engine. Diesel and soapnut oil (10%, 20%, 30% and 40%) fuel blends were used to conduct short-term engine performance and emission tests at varying loads in terms of 25% load increments from no load to full loads. Tests were carried out for engine operation and engine performance parameters such as fuel consumption, brake thermal efficiency, and exhaust emissions (smoke, CO, UBHC, NO_x, and O₂) were recorded. Among the blends SNO 10 has shown a better performance with respect to BTE and BSEC. All blends have shown higher HC emissions after about 75% load. SNO 10 and SNO 20 showed lower CO emissions at full load. NO_x emission for all blends was lower and SNO 40 blend achieved a 35% reduction in NO_x emission. SNO 10% has an overall better performance with regards to both engine performance and emission characteristics.     

An investigation into propane homogeneous charge compression ignition (HCCI) engine operation with residual gas trapping

Propane is available commercially for use in conventional internal combustion engines as an alternative fuel for gasoline. However, its application in the developing homogeneous charge compression ignition (HCCI) engines requires various approaches such as high compression ratios and/or inlet charge heating to achieve auto ignition. The approach documented here utilizes the trapping of internal residual gas (as used before in gasoline controlled auto ignition engines), to lower the thermal requirements for the auto ignition process. In the present work, with a moderate engine compression ratio the achievable engine load range was controlled by the degree of internal trapping of exhaust gas supplemented by inlet charge heating. Increasing the compression ratio decreased the inlet temperature requirements; however, it also resulted in higher pressure rise rates. Varying the inlet valve timing affects the combustion phasing which can help to decrease the maximum pressure rise rates. NOx emissions were characteristically low due to the nature of homogeneous combustion.     

Emission characteristics of high speed, dual fuel, compression ignition engine operating in a wide range of natural gas/diesel fuel proportions

In the effort to reduce pollutant emissions from diesel engines various solutions have been proposed, one of which is the use of natural gas as supplement to liquid diesel fuel, with these engines referred to as fumigated, dual fuel, compression ignition engines. One of the main purposes of using natural gas in dual fuel (liquid and gaseous one) combustion systems is to reduce particulate emissions and nitrogen oxides. Natural gas is a clean burning fuel; it possesses a relatively high auto-ignition temperature, which is a serious advantage over other gaseous fuels since then the compression ratio of most conventional direct injection (DI) diesel engines can be maintained high. In the present work, an experimental investigation has been conducted to examine the effects of the total air-fuel ratio on the efficiency and pollutant emissions of a high speed, compression ignition engine located at the authors’ laboratory, where liquid diesel fuel is partially substituted by natural gas in various proportions, with the natural gas fumigated into the intake air. The experimental results disclose the effect of these parameters on brake thermal efficiency, exhaust gas temperature, nitric oxide, carbon monoxide, unburned hydrocarbons and soot emissions, with the beneficial effect of the presence of natural gas being revealed. Given that the experimental measurements cover a wide range of liquid diesel supplementary ratios without any appearance of knocking phenomena, the belief is strengthened that the findings of the present work can be very valuable if opted to apply this technology on existing DI diesel engines.     

Numerical study on the realization of compression ignition in a type of porous medium engine fueled with Isooctane

The working process of a porous medium (PM) engine, characterized as periodic contact type and fueled with liquid fuel as Isooctane, is simulated by using an improved version of KIVA-3V. A modified volume-averaged method is proposed for describing the interaction between fuel droplets and the solid phase of the PM. The improved version of KIVA-3V was validated by simulating the experiment of Zhdanok for the superadiabatic combustion of CH₄-air mixtures under filtration in a packed bed. Good agreement between experimental data and computational results for the speed of combustion wave is achieved. The influences of initial PM temperature, PM structure and valve opening timing on the realization of compression ignition in the PM engine are also verified. Initial PM temperature is the crucial factor in guaranteeing the realization of the compression ignition of the PM engine. Considering influential factors, such as the properties of the PM, the compression ratio, the equivalence ratio, and the heat transfer between gas and solid phase of the PM should obtain optimized initial PM temperature. The variation in PM structure affects the convective heat transfer between the gas and solid phase and the dispersion effect of the PM. Compression ignition all can be realized in PM engines with four kinds of PM. Compression ignition is achieved at the considered four valve opening timings. Value opening timing has influence on the average temperature of the PM engine and the working of the PM engine does not allow earlier or later valve opening timing.     

Performance of diesel engine with biodiesel at varying compression ratio and ignition timing

The performance of Ricardo E6 engine using biodiesel obtained from mahua oil (B100) and its blend with high speed diesel (HSD) at varying compression ratio (CR), injection timing (IT) and engine loading (L) has been presented in this paper. The brake specific fuel consumption (BSFC) and exhaust gas temperature (EGT) increased, whereas brake thermal efficiency (BTE) decreased with increase in the proportion of biodiesel in the blends at all compression ratios (18:1-20:1) and injection timings (35-45° before TDC) tested. However, a reverse trend for these parameters was observed with increase in the CR and advancement of IT. The BSFC of B100 and its blends with high speed diesel reduced, whereas BTE and EGT increased with the increase in L for the range of CR and IT tested. The differences of BTEs between HSD and B100 were also not statistically significant at engine settings of ‘CR20IT40’ and ‘CR20IT45’. Thus, even B100 could be used on the Ricardo engine at these settings without affecting the performance obtained using HSD.     

Fuelling of a compression ignition engine on ethanol with DME as ignition promoter: Effect of injector configuration

The effect of injector configuration on the combustion and emissions of a compression ignition engine, fuelled on ethanol as the main fuel and dimethyl ether as ignition promoter, were investigated. Baseline constant speed tests were initially performed on diesel fuel using the recommended three-hole configuration. The tests were repeated with the recommended three-hole injector and then with a four-hole injector with ethanol as the main fuel. All other aspects of the engine remained unmodified. The four-hole injector resulted in the combustion of ethanol occurring closer to top dead centre, producing marginally more power and higher fuel conversion efficiency. In the case of the four-hole injector, emissions of both THC and NO_X were found to be lower than those produced by the three-hole injector. They were, however, in both cases lower than levels achieved with diesel fuelling.     

催化燃烧中表面反应-气相反应间相互作用及其对均质压燃发动机着火特性的影响

通过对微元管中甲烷在铂表面的催化燃烧过程的数值计算,分析了当混合气入口压力很高时气相反应对整个催化燃烧过程的影响;通过敏感度分析,找出了对异相着火及气相着火起主要作用的基元反应步.结果表明,在异相着火过程中起主要作用的基元反应步为甲烷与氧气在催化剂表面的吸附反应及氧气的解吸反应,在气相着火过程中起主要作用的基元反应步为OH·及水的吸附与解吸反应.对活塞顶涂有铂催化剂的均质压燃（HCCI）发动机的燃烧过程进行了数值模拟,分析了催化效应及关键表面反应基元步对HCCI发动机着火时刻以及燃烧过程中中间组分的影响,结果表明,催化反应能促进混合气的着火,缩短着火延迟时间,对HCCI发动机着火时刻起主要影响的表面反应为OH·及水的吸附与解吸反应.     

A study of natural gas/DME combustion in HCCI engines using CFD with detailed chemical kinetics

Combustion characteristics of natural gas and dimethyl ether (DME) mixture in a homogeneous charge compression ignition (HCCI) engine were studied numerically. Detailed chemical kinetics with 83 species and 360 reactions was used with an engine CFD code to simulate the combustion process. Operating conditions with different fuel compositions were simulated. Combustion, nitrogen oxides emissions and effects of fuel compositions on engine operating limits were well predicted by the present model. Chemical kinetics analysis indicated that ignition was achieved by DME oxidation which, in turn, induced combustion of natural gas. Low-temperature heat release is more pronounced as the amount of DME increases. Engine operations become unstable as the excess air ratio of natural gas is reduced near 2. The model also captures the HCCI features of low-combustion temperature and low-nitrogen oxides emissions for the alternative fuels used in this study.     

Effect of secondary mixing on fuel ignition and combustion in a diesel engine

The possibility of improving air-fuel mixture ignition by optimal contouring of the wall on which the jet is incident is confirmed. It is also shown that a decrease in the limiting temperature and in the ignition delay leads, in turn, to an increase in fuel-combustion efficiency, which ensures faster stabilization of engine operation after starting. Under diesel-engine nominal rating conditions, secondary mixing no longer has a profound effect on ignition and combustion processes. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 33–42, January–February, 1997     

Performance of compression ignition engine with mahua (Madhuca indica) biodiesel

The performance of biodiesel obtained from mahua oil and its blend with high speed diesel in a Ricardo E6 engine has been presented in this paper together with some of its fuel properties. These properties were found to be comparable to diesel and confirming to both the American and European standards. Engine performance (brake specific fuel consumption, brake thermal efficiency and exhaust gas temperature) and emissions (CO, smoke density and NO_x) were measured to evaluate and compute the behaviour of the diesel engine running on biodiesel. The reductions in exhaust emissions and brake specific fuel consumption together with increase brake power, brake thermal efficiency made the blend of biodiesel (B20) a suitable alternative fuel for diesel and thus could help in controlling air pollution.     

Optimization of a natural gas SI engine employing EGR strategy using a two-zone combustion model

Natural gas has been recently used as an alternative to conventional fuels in order to satisfy some environmental and economical concerns. In this study, a natural gas spark-ignition engine employing cooled exhaust gas recirculation (EGR) strategy in a high pressure inlet condition was optimized. Both engine compression ratio and start of combustion timing were optimized in order to obtain the lowest fuel consumption accompanied with high power and low emissions. That was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. In addition, a knocking model was incorporated with the two-zone combustion model in order to predict any auto-ignition that might occur. It was found that the value of the compression ratio at which the minimum fuel consumption occurs varies with the engine speed. A minimum fuel consumption of about 200 g/kW h was achieved at an engine speed of 1500 rpm, inlet conditions of 200 kPa and 333 K, and a compression ratio of about 12. Also, it was found that cooled EGR can significantly reduce NO emission at high compression ratio conditions. NO emission decreased by about 28% when EGR was increased from 20% at compression ratio of 10 to 27% at compression of 12 at the same engine speed of 3000 rpm.     

A computational simulation study for techno-economic comparison of conventional and stripping gas methods for natural gas dehydration

In the present work, the conventional natural gas dehydration method (CDM) and stripping gas method (SGM) are technically and economically analyzed, utilizing Aspen HYSYS and Aspen Process Economic Analyzer (APEA), respectively. To optimize the CDM and SGM, the sensitivities of the water content of dry gas, reboiler duty and raw material loss are analyzed against solvent rate and stripping gas rate. The optimized processes are set to achieve a targeted value of water content in dry gas and analyzed at optimized point. The analysis shows that SGM gives 46% lower TEG feed rate, 42% lower reboiler duty and 99.97% pure regenerated TEG. Moreover, economic analysis reveals that SGM has 38% lower annual operating cost compared to CDM. According to results, from both technical and economic point of view, SGM is more feasible for natural gas dehydration compared to CDM.     

A computational simulation study for techno-economic comparison of conventional and stripping gas methods for natural gas dehydration

In the present work, the conventional natural gas dehydration method (CDM) and stripping gas method (SGM) are technically and economically analyzed, utilizing Aspen HYSYS and Aspen Process Economic Analyzer (APEA), respectively. To optimize the CDM and SGM, the sensitivities of the water content of dry gas, reboiler duty and raw material loss are analyzed against solvent rate and stripping gas rate. The optimized processes are set to achieve a targeted value of water content in dry gas and analyzed at optimized point. The analysis shows that SGM gives 46% lower TEG feed rate, 42% lower reboiler duty and 99.97% pure regenerated TEG. Moreover, economic analysis reveals that SGM has 38% lower annual operating cost compared to CDM. According to results, from both technical and economic point of view, SGM is more feasible for natural gas dehydration compared to CDM.     

天然气中二氧化碳脱除技术

本文介绍了脱除天然气中二氧化碳的几种经济可行的工艺技术,即醇胺溶液化学吸收（MDEA）法、膜分离法、变压吸附法和低温甲醇吸收法。