甲醇预混合气F-T柴油引燃模式下发动机燃烧特性研究

为了提高甲醇在能量转化效率方面的优势,在一台CY25TQ型柴油机上,利用F-T柴油和煤基甲醇研究了甲醇占能比、F-T柴油喷油时刻对甲醇预混合气F-T柴油引燃燃烧方式下发动机燃烧特性的影响。试验结果表明:甲醇占能比增加,此燃烧方式滞燃期、持续期波动较大。在平均有效压力为0.45MPa下,缸内最大压力、瞬时放热率峰值、最大压力升率明显降低,最大降幅分别为26.40%、59.25%和58.00%。高负荷时,不同甲醇占能比下F-T柴油喷射时刻调整,能促进压升率进一步降低。与原柴油机扩散燃烧方式相比,虽然采用引燃喷射的双燃料发动机在中低负荷时的有效热效率有所降低,但是随着负荷增加,高负荷下的热效率比原柴油机高,最大提高了17.14%。     

甲醇预混合气F-T柴油引燃发动机压力振荡研究

为有效降低预混引燃双燃料发动机的压力振荡,对甲醇预混合气F-T柴油引燃发动机的爆震和粗暴燃烧及循环变动进行研究。试验结果表明:缸压信号的功率谱密度曲线并结合带通滤波方法可以很好地反映爆震和粗暴燃烧的结果;当甲醇占能比为0.62,较大压缩比下,发动机压力波动较小;随甲醇占能比增加或压缩比降低,爆发压力循环变动均会出现先升后降趋势,供油推迟有利于降低爆发压力循环变动。协调甲醇占能比、供油提前角、压缩比,对有效降低预混引燃发动机压力振荡具有重要意义。     

汽油均质混合气柴油引燃(HCII)燃烧特性的研究

为探索大幅度提高汽油机热效率的途径，采用了一种汽油均质混合气柴油引燃(HCⅡ)的燃烧方式，结合发动机性能试验与可视化试验对HCⅡ的燃烧特性进行了初步研究。研究结果表明：HCⅡ燃烧方式的热效率显著高于汽油机，可以达到甚至超过柴油机的水平；在汽柴油质量比大于0．5时可保证无烟燃烧；随汽柴油比的增加，滞燃期增长，着火点位置由中心向周边拓展。     

甲醇/生物柴油/F-T柴油混合燃料燃烧特性与排放特性研究

选取煤基燃料F-T柴油和甲醇,并辅以生物柴油,配制成甲醇/生物柴油/F-T柴油混合燃料,在未做调整的四缸增压中冷柴油机上进行试验研究。结果表明:混合燃料的燃烧放热率峰值、压力升高率峰值和缸内压力峰值均随混合燃料中生物柴油比例的增加而增加,且对应的相位延迟;外特性下燃用混合燃料时,碳烟、氮氧化物的排放量明显降低,在低转速下一氧化碳降低幅度较大,混合燃料对甲醛也有较大幅度的减排作用。     

引燃柴油量对甲醇/柴油双燃料发动机性能和排放的影响

在一台TY1100型直喷柴油机上,开展了引燃柴油量对柴油引燃甲醇双燃料发动机性能和排放影响的研究。试验结果表明:引燃柴油比例为28.9%~48.2%时,发动机可获得较好的动力性,甲醇质量掺比可达73.3%~83.2%。与原柴油机相比,双燃料发动机的碳烟排放大幅度下降,NOx排放降低,而HC和CO排放增加。高负荷时发动机有效热效率增加而CO排放基本相当。在同一引燃柴油量下,HC排放呈先增加后减少的趋势,增加引燃柴油量,可以提高发动机低负荷时的有效热效率和降低HC排放,但在全负荷时,会导致NOx排放增加。     

燃用F-T柴油/甲醇微乳化燃料对柴油机排放特性影响

在某增压柴油机上分别燃用0~#柴油、F-T柴油和三种不同配比的F-T柴油/甲醇微乳化燃料(简称FT微乳化燃料),分析了其燃烧排放特性,试验中柴油机结构和参数未进行调整。研究结果表明:相比于0~#柴油,燃用FT微乳化燃料缸内压力下降,放热率峰值降低。FT微乳化燃料有效降低了CO、NO_x和碳烟等常规排放,平均降幅范围分别为20%~40%、25%~27%和65%~97%。非常规排放中未燃甲醇排放随着燃料中甲醇比例的增加而增加,随着负荷增大而降低;甲醛排放均较0~#柴油有所增加,随负荷变化趋势与未燃甲醇相同,但并未与燃料中甲醇含量形成线性相关。     

柴油引燃天然气发动机不同喷射时刻和引燃油量下的燃烧和颗粒排放特性研究

在一台改装的柴油引燃天然气发动机上对不同的柴油喷射时刻和引燃油量(喷射油量)下的燃烧和颗粒排放进行了试验研究,并对相关的燃烧和颗粒排放特性进行分析。研究结果表明:随着喷射时刻和引燃油量的变化,柴油引燃天然气发动机的颗粒排放呈现单峰分布,其粒径分布无太大的变化,峰值粒径出现在29nm附近。随着喷射时刻的提前,纳米级颗粒数量浓度显著增加,颗粒的质量浓度呈现先减小后增加的趋势,滞燃期逐渐推迟,总燃烧持续期先减小后缓慢增加,相应的放热率曲线型心在逐渐靠近上止点后逐渐远离;随着引燃油量的增加,柴油引燃天然气发动机滞燃期和总燃烧持续期持续减小,放热率曲线型心逐渐靠近上止点,发动机排放颗粒的数量浓度明显减小,但其颗粒的质量浓度逐渐增加。     

PODE引燃甲醇双燃料压燃发动机排放特性研究

文章通过台架试验研究了双燃料压燃发动机的气态污染物的排放特性。研究结果表明:甲醇的加入会使得双燃料发动机的CO,THC,CH_4,1,3-丁二烯和N_2O的排放量均有所升高;随着甲醇占能比的增加,NO_x的排放量明显降低,当发动机负荷较小时,NO_x的排放量逐渐减少,而当发动机的负荷较大时,NO_x的排放量呈现出先增加后减少的变化趋势,而且NO_x中各成分所占比例也随着甲醇占能比的增加而发生改变;随着发动机负荷的增大,CO,THC,CH_4,1,3-丁二烯和N_2O的排放量均逐步下降,CO_2,NO和NO_x的排放量均逐步升高。     

柴油/甲醇组合燃烧增压共轨发动机的燃烧特性和排放特性

在增压共轨发动机上采用柴油,甲醇组合燃烧(DMCC)方式进行燃烧特性分析和排放特性分析.对DMCC模式下放热率、缸内压力变化和p-V图的分析表明,DMCC模式具有吸热汽化、推迟着火时间、提高定容燃烧度、降低排气温度等优点,从而大幅度提高了燃料的燃烧效率.对M100(纯甲醇)和M90(含水10%的甲醇)的排放量进行检测,表明M90比M100更能降低甲醛、NOJ、HC和CO排放.     

柴油引燃式天然气发动机最佳引燃柴油量及过量空气系数浓限、稀限的研究

以气口顺序喷射、全电控、柴油引燃天然气发动机为实验发动机,对柴油引燃天然气发动机的最佳引燃柴油量及过量空气系数的浓限、稀限进行了研究。研究发现：对于柴油引燃天燃气发动机的不同运行工况,存在相应的最佳引燃柴油量;最佳引燃柴油量并非越小（或天然气替代率越高）越好,在较小的引燃柴油量下,存在一个对碳烟排放不敏感的引燃柴油量;在这个不敏感的引燃柴油量范围内,适当增加引燃柴油量可以使天然气／空气混合气工作在较稀的过量空气系数下,降低NOx排放。通过实验得到了天然气／空气混合气过量空气系数的浓限、稀限,指出过量空气系数浓限是由NOx的排放标准所决定的,稀限则是由碳烟、HC、CO排放标准所决定的。     

甲醇质量比对防爆柴油机预混合引燃模式燃烧特性的影响

针对甲醇、聚甲氧基二甲醚和F-T柴油的各自优势,为提高能量转化效率,在改造后的CY25防爆柴油机上研究甲醇质量比对甲醇/聚甲氧基二甲醚、甲醇/F-T柴油预混合引燃模式燃烧特性的影响。研究结果表明:随着甲醇质量比的增加,甲醇/聚甲氧基二甲醚燃烧模式的比油耗增大,有效热效率降低;在甲醇质量比小于60%时,随着甲醇质量比的增加,甲醇/F-T柴油燃烧模式的比油耗减少,有效热效率升高;随着甲醇质量比的增加,两种预混合引燃模式的燃烧相位均后移,与单燃料原机燃烧模式相比,甲醇/聚甲氧基二甲醚燃烧模式下的缸内压力峰值和瞬时放热率峰值的最大升幅分别为9.5%和142%,甲醇/F-T柴油燃烧模式下的缸内压力峰值和瞬时放热率峰值的最大升幅分别4.24%和99.7%。     

Experimental investigations on a hydrogen diesel homogeneous charge compression ignition engine with exhaust gas recirculation

In this experimental study, hydrogen was inducted along with air and diesel was injected into the cylinder using a high pressure common rail system, in a single cylinder homogeneous charge compression ignition engine. An electronic controller was used to set the required injection timing of diesel for best thermal efficiency. The influences of hydrogen to diesel energy ratio, output of the engine and exhaust gas recirculation (EGR) on performance, emissions and combustion were studied in detail. An increase in the amount of hydrogen improved the thermal efficiency by retarding the combustion process. It also lowered the exhaust emissions. Large amounts of hydrogen and EGR were needed at high outputs for suppressing knock. The range of operation was brake mean effective pressures of 2–4 bar. The levels of HC and CO emitted were not significantly influenced by the amount of hydrogen that was used.     

Effects of compression ratio on the combustion characteristics of a homogeneous charge compression ignition engine

The effects of homogeneous charge compression ignition (HCCI) engine compression ratio on its combustion characteristics were studied experimentally on a modified TY1100 single cylinder engine fueled with dimethyl ether. The results show that dimethyl ether (DME) HCCI engine can work stably and can realize zero nitrogen oxides (NO_x) emission and smokeless combustion under the compression ratio of both 10.7 and 14. The combustion process has obvious two stage combustion characteristics at ɛ = 10.7 (ɛ refers to compression ratio), and the combustion beginning point is decided by the compression temperature, which varies very little with the engine load; the combustion beginning point is closely related to the engine load (concentration of mixture) with the increase in the compression temperature, and it moves forward versus crank angle with the increase in the engine load at ɛ = 14; the combustion durations are shortened with the increase in the engine load under both compression ratios. __________ Translated from Chinese Journal Combustion Engine Engineering, 2006, 27(4): 9–12 [译自: 内燃机工程]     

Role of hydrogen in improving performance and emission characteristics of homogeneous charge compression ignition engine fueled with graphite oxide nanoparticle-added microalgae biodiesel/diesel blends

The development of low-temperature combustion models combined with the use of biofuels has been considered as an efficient strategy to reduce pollutant emissions like CO, HC. NO_x, and smoke. Indeed, Homogeneous Charge Compression Ignition (HCCI) is the new approach to drastically minimize NO_x emissions and smoke owing to the lower cylinder temperature and a higher rate of homogeneous A/F mixture as compared to compression ignition (CI) engines. The present research deal with the behavior analysis of a CI engine powered by diesel, Euglena Sanguinea (ES), and their blends (ES20D80, ES40D60, ES60D40, ES80D20). The experimental results revealed the highest brake thermal efficiency for ES20D80 although it decreased by 4.1% compared to diesel at normal mode. The average drop in HC, CO, and smoke was 2.1, 2.3, and 5.7% for ES20D80 as opposed to diesel fuel. Therefore, in the next stage, ES20D80 with various concentrations of graphite oxide (GO) nanoparticle (20, 40, 60, and 80 ppm) was chosen to carry out experiments in the HCCI mode, in which hydrogen gas was induced along with air through the intake pipe at a fixed flow rate of 3 lpm for the enrichment of the air-fuel mixture. As a result, the combination of hydrogen-enriched gas and GO-added ES20D80 in the HCCI mode showed similar performance to the CI engine but registered a major reduction of NO_x and smoke emissions, corresponding to 75.24% and 53.07% respectively, as compared to diesel fuel at normal mode.     

Study on homogeneous charge compression ignition combustion in argon circulated closed cycle hydrogen engine

It is important to improve thermal efficiency and to reduce harmful exhaust gas emissions in internal combustion engines. A closed cycle engine system that uses a monatomic molecular gas as the working fluid can be expected to have high thermal efficiency due to the high specific heat ratio of the gas. Several studies have been reported on closed cycle engines with conventional spark ignition or compression ignition. This research newly proposes an argon circulated closed cycle homogeneous charge compression ignition (HCCI) engine system fueled with hydrogen. In this engine system, effects of in-cylinder gas initial temperature and residual water in recirculated gas on combustion characteristics were investigated. The results show that the system with argon circulation has the wider range of operable conditions and the higher thermal efficiency compared to the case with air as the working fluid.     

Experimental study of combustion and emission characteristics of ethanol fuelled port injected homogeneous charge compression ignition (HCCI) combustion engine

The homogeneous charge compression ignition (HCCI) is an alternative combustion concept for in reciprocating engines. The HCCI combustion engine offers significant benefits in terms of its high efficiency and ultra low emissions. In this investigation, port injection technique is used for preparing homogeneous charge. The combustion and emission characteristics of a HCCI engine fuelled with ethanol were investigated on a modified two-cylinder, four-stroke engine. The experiment is conducted with varying intake air temperature (120–150 °C) and at different air–fuel ratios, for which stable HCCI combustion is achieved. In-cylinder pressure, heat release analysis and exhaust emission measurements were employed for combustion diagnostics. In this study, effect of intake air temperature on combustion parameters, thermal efficiency, combustion efficiency and emissions in HCCI combustion engine is analyzed and discussed in detail. The experimental results indicate that the air–fuel ratio and intake air temperature have significant effect on the maximum in-cylinder pressure and its position, gas exchange efficiency, thermal efficiency, combustion efficiency, maximum rate of pressure rise and the heat release rate. Results show that for all stable operation points, NO_x emissions are lower than 10 ppm however HC and CO emissions are higher.     

Multi-dimensional modeling of the application of catalytic combustion to homogeneous charge compression ignition engine

The detailed surface reaction mechanism of methane on rhodium catalyst was analyzed.Comparisons betweennumerical simulation and experiments showed a basic agreement.The combustion process of homogeneouscharge compression ignition(HCCI)engine whose piston surface has been coated with catalyst(rhodium andplatinum)was numerically investigated.A multi-dimensional model with detailed chemical kinetics was built.The effects of catalytic combustion on the ignition timing,the temperature and CO concentration fields,and HC,CO and NO_x emissions of the HCCI engine were discussed.The results showed the ignition timing of the HCCIengine was advanced and the emissions of HC and CO were decreased by the catalysis.     

Thermodynamic analysis and utilisation of wet ethanol in homogeneous charge compression ignition engine

In this study, our objective is to computationally analyse the wet ethanol operated homogeneous charge compression ignition (HCCI) engine to evaluate its first and second law efficiency and observe these results by varying effectiveness of regenerator. The paper concludes that the first and second law efficiency decreases due to the increase in the effectiveness of regenerator. This increase in effectiveness leads to an increase in the temperature of air coming out of the regenerator. It further results in increase of the fuel air mixture intake temperature which finally reduces the work output and efficiency of the engine. Furthermore, the method of exergy analysis has been applied and evaluated. This study indicates that due to domination of chemical exergy destruction in combustion reaction in these systems, maximum exergy is destroyed in HCCI engine and to a lesser extent in catalytic converter. These findings will help in the design of such system for optimum result.     

Experimental study of the performances of a modified diesel engine operating in homogeneous charge compression ignition (HCCI) combustion mode versus the original diesel combustion mode

Homogeneous charge compression ignition (HCCI) combustion mode provides very low NO_x and soot emissions; however, it has some challenges associated with hydrocarbon (HC) emissions, fuel consumption, difficult control of start of ignition and bad behaviour to high loads. Cooled exhaust gas recirculation (EGR) is a common way to control in-cylinder NO_x production in diesel and HCCI combustion mode. However EGR has different effects on combustion and emissions, which are difficult to distinguish. This work is intended to characterize an engine that has been modified from the base diesel engine (FL1 906 DEUTZ-DITER) to work in HCCI combustion mode. It shows the experimental results for the modified diesel engine in HCCI combustion mode fueled with commercial diesel fuel compared to the diesel engine mode. An experimental installation, in conjunction with systematic tests to determine the optimum crank angle of fuel injection, has been used to measure the evolution of the cylinder pressure and to get an estimate of the heat release rate from a single-zone numerical model. From these the angle of start of combustion has been obtained. The performances and emissions of HC, CO and the huge reduction of NO_x and smoke emissions of the engine are presented. These results have allowed a deeper analysis of the effects of external EGR on the HCCI operation mode, on some engine design parameters and also on NO_x emission reduction.