甲醇-柴油混合燃料对发动机燃烧及排放特性的影响

在一台YTR3105直喷式柴油机上进行了小比例甲醇-柴油混合燃料发动机的燃烧及排放特性试验研究。结果表明:在相同的平均有效压力和转速下,随着甲醇含量的增加,燃料着火延迟相应增大,使得燃烧过程向上止点后移动。混合燃料的滞燃期比柴油长,预混燃烧放热率峰值增大,燃烧持续期缩短,缸内最大爆发压力和压力升高率增加。与纯柴油相比,甲醇-柴油混合燃料HC排放有所升高,但NOx和碳烟排放降低。大负荷时,CO排放显著下降。     

Performance,combustion and exhaust emissions characteristics investigation using Citrullus colocynthis L. biodiesel in DI diesel engine

The aims of this study is to investigate the performance, combustion and exhaust emissions of a single-cylinder, air cooled, direct injection (DI), compression ignition engine using biodiesel from non-edible feedstock. In this work, biodiesel (B100) used to lead this investigation is Citrullus colocynthis L. methyl ester (CCME) and its blends B30 with diesel fuel. The biodiesel is produced via alkaline-catalyzed transesterification process using methanol (6:1 M ratio), 1% of sodium hydroxide at the reaction temperature of 60 °C for 1 h. The important physical and chemical properties of CCME are close to those of diesel fuel. Fuels (diesel fuel, B100 and B30) were tested on a DI diesel engine at 1500 rpm for various power outputs. The results indicated that B100 and B30 exhibit the same combustion characteristics compared to diesel fuel. However, B100 and B30 display earlier start of combustion. At lower engine loads, the peaks of cylinder pressure and heat release rate (HRR) were higher for B30 than B100 and diesel fuel during premixed combustion period. At higher engine loads the peaks of cylinder pressure was higher for B100 than B30 and diesel fuel, but the HRR during diffusion combustion is more considerable than diesel fuel. The brake specific fuel consumption (BSFC) was higher for B100 than diesel fuel at all engine loads while B30 exhibited comparable trends. The thermal efficiency is slightly higher for B100 than B30 and diesel fuel at low loads and increase for B30 at full loads.B30 and B100 provided a higher reduction of hydrocarbons emissions up to 50% for B100. Nitrogen oxides and particulate matter emissions were also reduced.     

Effect of diethyl ether and ethanol additives on the combustion and emission characteristics of biodiesel-diesel blended fuel engine

An experimental investigation is conducted to evaluate the effects of using diethyl ether and ethanol as additives to biodiesel/diesel blends on the performance, emissions and combustion characteristics of a direct injection diesel engine. The test fuels are denoted as B30 (30% biodiesel and 70% diesel in vol.), BE-1 (5% diethyl ether, 25% biodiesel and 70% diesel in vol.) and BE-2 (5% ethanol, 25% biodiesel and 70% diesel in vol.) respectively. The results indicate that, compared with B30, there is slightly lower brake specific fuel consumption (BSFC) for BE-1. Drastic reduction in smoke is observed with BE-1 and BE-2 at higher engine loads. Nitrogen oxide (NOx) emissions are found slightly higher for BE-2. Hydrocarbon (HC) emissions are slightly higher for BE-1 and BE-2, but carbon monoxide (CO) are slightly lower. The peak pressure, peak pressure rise rate and peak heat release rate of BE-1 are almost similar to those of B30, and higher than those of BE-2 at lower engine loads. At higher engine loads the peak pressure, peak pressure rise rate and peak heat release rate of BE-1 are the highest and those of B30 are the lowest. BE-1 reflects better engine performance and combustion characteristics than BE-2 and B30.     

Performance,emission and combustion characteristics of a variable compression ratio engine using methyl esters of waste cooking oil and diesel blends

The performance, emission and combustion characteristics of a single cylinder four stroke variable compression ratio multi fuel engine when fueled with waste cooking oil methyl ester and its 20%, 40%, 60% and 80% blends with diesel (on a volume basis) are investigated and compared with standard diesel. The suitability of waste cooking oil methyl ester as a biofuel has been established in this study. Bio diesel produced from waste sun flower oil by transesterification process has been used in this study. Experiment has been conducted at a fixed engine speed of 1500 rpm, 50% load and at compression ratios of 18:1, 19:1, 20:1, 21:1 and 22:1. The impact of compression ratio on fuel consumption, combustion pressures and exhaust gas emissions has been investigated and presented. Optimum compression ratio which gives best performance has been identified. The results indicate longer ignition delay, maximum rate of pressure rise, lower heat release rate and higher mass fraction burnt at higher compression ratio for waste cooking oil methyl ester when compared to that of diesel. The brake thermal efficiency at 50% load for waste cooking oil methyl ester blends and diesel has been calculated and the blend B40 is found to give maximum thermal efficiency. The blends when used as fuel results in reduction of carbon monoxide, hydrocarbon and increase in nitrogen oxides emissions.     

Combustion characteristics of a direct-injection diesel engine fueled with Fischer-Tropsch diesel

Fischer-Tropsch (F-T) diesel fuel is characterized by a high cetane number, a near-zero sulphur content and a very low aromatic level. On the basis of the recorded incylinder pressures and injector needle lifts, the combustion characteristics of an unmodified single-cylinder direct-injection diesel engine operating on F-T diesel fuel are analyzed and compared with those of conventional diesel fuel operation. The results show that F-T diesel fuel exhibits a slightly longer injection delay and injection duration, an average of 18.7% shorter ignition delay, and a comparable total combustion duration when compared to those of conventional diesel fuel. Meanwhile, F-T diesel fuel displays an average of 26.8% lower peak value of premixed burning rate and a higher peak value of diffusive burning rate. In addition, the F-T diesel engine has a slightly lower peak combustion pressure, a far lower rate of pressure rise, and a lower mechanical load and combustion noise than the conventional diesel engine. The brake specific fuel consumption is lower and the effective thermal efficiency is higher for F-T diesel fuel operation. Translated from Journal of Xi’an Jiaotong University, 2006, 40(1): 5–9 [译自: 西安交通大学学报]     

柴油机燃用F-T柴油与0号柴油混合燃料时的性能与排放

开展了直喷式柴油机燃用F-T柴油与0号柴油混合燃料时性能与排放的研究,试验用燃料为0号柴油、含25%和50%F-T柴油的混合燃料以及100%F-T柴油。结果表明,在相同工况下,随着混合燃料中F-T柴油比例的增加,滞燃期缩短,预混燃烧放热峰值降低,扩散燃烧放热峰值增大,最高燃烧压力略微降低,发动机的燃油消耗率和有效热效率得到改善。在负荷特性上,发动机的CO_2、HC、CO、NO_x和碳烟排放随着F-T柴油的加入而降低,其中CO和碳烟在中高负荷时降低幅度最为显著。当F-T柴油掺混比例由0增至25%时,碳烟排放降低效果最为明显,此后随着F-T柴油的继续增加,碳烟排放降低幅度减少。     

柴油机燃用F-T柴油与0号柴油混合燃料的燃烧特性

根据实测的喷油器针阀升程和示功图,开展了直喷式柴油机燃用F-T柴油与0号柴油混合燃料时燃烧特性的研究．试验用燃料为0号柴油、含25%和50%F-T柴油的混合燃料以及100%F-T柴油．结果表明,在相同工况下,随着混合燃料中F-T柴油比例的增加,喷油延迟角增大,而喷油持续期变化不大．滞燃期随着F-T柴油比例的增加而缩短,其中当F-T柴油的比例由0增至25%时,滞燃期缩短最为明显,此后进一步增加F-T柴油的比例,滞燃期缩短幅度减小．随着混合燃料中F-T柴油比例的增加,预混燃烧放热峰值降低,扩散燃烧放热峰值增大,燃烧持续期略有延长,缸内最高燃烧压力和气体最高平均温度降低,最大压力升高率显著下降,发动机的燃烧噪音和机械损失减小,有效燃油消耗率和有效热效率得到改善．     

F-T柴油对直喷式柴油机燃烧和排放的影响

在两种不同供油提前角下研究了燃用F-T柴油对直喷式柴油机燃烧和排放特性的影响,结果表明:发动机不做任何调整时,与0号柴油相比,燃用F-T柴油的滞燃期较短,预混燃烧放热峰值较低,扩散燃烧放热峰值较高,最高燃烧压力和最大压力升高率较低,燃油消耗率和热效率都得到了改善,HC、CO、NOx和碳烟排放同时降低。当供油提前角推迟3℃A时,燃用F-T柴油燃烧持续期明显缩短,预混燃烧放热峰值、最高燃烧压力和最大压力升高率进一步降低,扩散燃烧放热峰值略有升高,燃油消耗率变化不大,NOx排放进一步降低, HC、CO和碳烟略有增加,其中HC排放与原柴油机相当,而CO和碳烟仍远低于原柴油机。     

Comparison between blended mode and fumigation mode on combustion,performance and emissions of a diesel engine fueled with ternary fuel (diesel-biodiesel-ethanol) based on engine speed

According to the literature, there is in lack of a comprehensive study to compare the combustion, performance and emissions of a diesel engine using diesel, biodiesel and ethanol fuels (DBE) in the blended mode and fumigation mode under various engine speeds. This study was conducted to fill this knowledge gap by comparing the effect of blended, fumigation and combined fumigation + blended (F + B) modes on the combustion, performance and emissions of a diesel engine under a constant engine load (50% of full torque) with five engine speeds ranging from 1400 rpm to 2200 rpm. A constant overall fuel composition of 80% diesel, 5% biodiesel and 15% ethanol, by volume % (D80B5E15), was utilized to provide the same fuel for comparing the three fueling modes.According to the average results of five engine speeds, the blended mode has higher peak heat release rate (HRR), ignition delay (ID), brake thermal efficiency (BTE), brake specific nitrogen monoxide (BSNO) and brake specific nitrogen oxides (BSNO_X), but lower duration of combustion (DOC), brake specific fuel consumption (BSFC), brake specific carbon dioxide (BSCO₂), brake specific carbon monoxide (BSCO), brake specific hydrocarbon (BSHC), brake specific nitrogen dioxide (BSNO₂), brake specific particulate matter (BSPM), total number concentration (TNC) and geometric mean diameter (GMD), and similar peak in-cylinder pressure compared to the fumigation mode. In addition, for almost all the parameters, results obtained in the F + B mode are in between those of the blended and fumigation modes. In regard to the effect of engine speed, the results reveal that the increase in engine speed causes reduction in peak in-cylinder pressure, BTE, BSHC, BSNO_X, BSNO and BSNO₂, but increase in peak HRR, ID, DOC, BSFC, BSCO₂, BSPM and TNC, and similar BSCO and GMD for almost all the tested fueling modes. It can be inferred that the blended mode is the suitable fueling mode, compared with the fumigation mode, under the operating conditions investigated in this study.     

Effects of Fischer-Tropsch diesel fuel on combustion and emissions of direct injection diesel engine

Effects of Fischer-Tropsch (F-T) diesel fuel on the combustion and emission characteristics of a single-cylinder direct injection diesel engine under different fuel delivery advance angles were investigated. The experimental results show that F-T diesel fuel exhibits shorter ignition delay, lower peak values of premixed burning rate, lower combustion pressure and pressure rise rate, and higher peak value of diffusion burning rate than conventional diesel fuel when the engine remains unmodified. In addition, the unmodified engine with F-T diesel fuel has lower brake specific fuel consumption and higher effective thermal efficiency, and presents lower HC, CO, NO_x and smoke emissions than conventional diesel fuel. When fuel delivery advance angle is retarded by 3 crank angle degrees, the combustion duration is obviously shortened; the peak values of premixed burning rate, the combustion pressure and pressure rise rate are further reduced; and the peak value of diffusion burning rate is further increased for F-T diesel fuel operation. Moreover, the retardation of fuel delivery advance angle results in a further significant reduction in NO_x emissions with no penalty on specific fuel consumption and with much less penalty on HC, CO and smoke emissions.     

直喷式柴油机燃用F-T柴油时的性能与排放

煤通过Fischer-Tropsch（F-T）合成可以获得十六烷值高、硫和芳香烃含量极低的F-T柴油.在一台未作改动的单缸直喷式柴油机上对燃用F-T柴油时发动机的性能和排放进行了研究.结果表明,在相同工况下与燃用常规柴油相比,燃用F-T柴油时的滞燃期较短,预混燃烧放热峰值较低,扩散燃烧放热峰值较高,最高燃烧压力略低,最大压力升高率显著下降,燃油消耗率和热效率都得到了改善.燃用F-T柴油可同时降低CO、HC、NOx和碳烟排放,其中NOx和碳烟排放分别平均降低了16.7%和40.3%.研究表明F-T柴油是柴油机优秀的清洁代用燃料.     

Biofuels and thermal barrier: A review on compression ignition engine performance,combustion and exhaust gas emission

The performance of an internal combustion engine is affected when renewable biofuels are used instead of fossil fuels in an unmodified engine. Various engine modifications were experimented by the researchers to optimise the biofuels operated engine performance. Thermal barrier coating is one of the techniques used to improve the biofuels operated engine performance and combustion characteristics by reducing the heat loss from the combustion chamber. In this study, engine tests results on performance, combustion and exhaust emission characteristics of the biofuels operated thermal barrier coated engines were collated and reviewed. The results found in the literature were reviewed in three scenarios: (i) uncoated versus coated engine for fossil diesel fuel application, (ii) uncoated versus coated engine for biofuels (and blends) application, and (iii) fossil diesel use on uncoated engine versus biofuel (and blends) use on coated engine. Effects of injection timing, injection pressure and fuel properties on thermal barrier coatings were also discussed. The material type, thickness and properties of the coating materials used by the research community were presented. The effectiveness and durability of the coating layer depends on two key properties: low thermal conductivity and high thermal expansion coefficient. The current study showed that thermal barrier coatings could potentially offset the performance drop due to use of biofuels in the compression ignition engines. Improvements of up to 4.6% in torque, 7.8% in power output, 13.4% in brake specific fuel consumption, 15.4% in brake specific energy consumption and 10.7% in brake thermal efficiency were reported when biofuels or biofuel blends were used in the thermal barrier coated engines as compared to the uncoated engines. In coated engines, peak cylinder pressure and exhaust gas temperature were increased by up to 16.3 bar and 14% respectively as compared to uncoated condition. However, changes in the heat release rates were reported to be between ?27% and +13.8% as compared to uncoated standard engine. Reductions of CO, CO₂, HC and smoke emissions were reported by up to 3.8%, 11.1%, 90.9% and 63% respectively as compared to uncoated engines. Significant decreases in the PM emissions were also reported due to use of thermal barrier coatings in the combustion chamber. In contrast, at high speed and at high load operation, increase in the CO and CO₂ emissions were also reported in coated engines. Coated engines gave higher NO_x emissions by about 4–62.9% as compared to uncoated engines. Combined effects of thermal barrier coatings and optimisation of fuel properties and injection parameters produced further performance and emissions advantages compared to only thermal barrier coated engines. Overall, current review study showed that application of thermal barrier coatings in compression ignition engines could be beneficial when biofuels or biofuel blends are used instead of standard fossil diesel. However, more research is needed combining coatings, types of biofuels and other engine modifications to establish a concrete conclusion on the effectiveness of the thermal barrier when biofuels are used in the compression ignition engine. Reduction of NO_x emissions is another important R & D area.     

A cycle simulation model for predicting the performance of a diesel engine fuelled by diesel and biodiesel blends

Among the alternative fuels, biodiesel and its blends are considered suitable and the most promising fuel for diesel engine. The properties of biodiesel are found similar to that of diesel. Many researchers have experimentally evaluated the performance characteristics of conventional diesel engines fuelled by biodiesel and its blends. However, experiments require enormous effort, money and time. Hence, a cycle simulation model incorporating a thermodynamic based single zone combustion model is developed to predict the performance of diesel engine. The effect of engine speed and compression ratio on brake power and brake thermal efficiency is analysed through the model. The fuel considered for the analysis are diesel, 20%, 40%, 60% blending of diesel and biodiesel derived from Karanja oil (Pongamia Glabra). The model predicts similar performance with diesel, 20% and 40% blending. However, with 60% blending, it reveals better performance in terms of brake power and brake thermal efficiency.     

The experimental study on the performance,combustion and emission characteristics of a diesel engine using diesel – biodiesel – diethyl ether blends

ABSTRACT

In the present research work, the experimental analysis has been executed to investigate the influence of diethyl ether as an oxygenated additive to the diesel-biodiesel blend on the performance, combustion and emission characteristics of a diesel engine. The biodiesel (Frying oil methyl ester) was prepared by the transesterification process, and the biodiesel was added (40% by volume) to the diesel fuel to prepare the diesel-biodiesel blend (D60FME40). The diethyl ether was added to the diesel-biodiesel blends D60FM35 (diesel 60% + biodiesel 35% by volume) and D60FM30 (diesel 60% + biodiesel 30% by volume) with suitable volume proportions of 5% and 10% respectively to form diesel-biodiesel-diethyl ether blends ((D60FM35DEE5) & (D60FM30DEE10)). Initially, the test was conducted with diesel fuel to obtain the baseline reference reading. Then, the reading was compared with results taken from the engine using a diesel-biodiesel blend (D60FME40) and diethyl ether blends (D60FM35DEE5) & (D60FM30DEE10). The results reveal that the maximum brake thermal efficiency was obtained with diesel fuel and it was higher than the diesel-biodiesel blend and diethyl ether blends. The peak in-cylinder gas pressure and heat release rate in the premixed stage was less for the diesel-biodiesel blend, but it was increased with the addition of diethyl ether to the blend. The diesel-biodiesel-diethyl ether blends show less carbon monoxide and hydrocarbon emissions except for NO_X emission as compared to the diesel and diesel-biodiesel blend, especially at the engine rated power.     

Performance of a DI diesel engine fuelled by blends of diesel and kiln-produced pyroligneous tar

This paper presents results of experiments undertaken to determine the performance of a direct injection (DI) diesel engine fuelled by blends of kiln-produced pyroligneous tar (PT) and diesel. The PT was sourced from Bulgaria where it was produced from a pine feedstock via a traditional kiln method that involves separation of the aqueous pyroligneous acid fraction. The tar is characterized by high carbon concentration, viscosity and high heating value. Although high, at fuel injection temperatures over 120 °C the tar's viscosity is likely to be lower than diesel. Analysis by GC revealed a number of compounds typically extracted from wood-based tar products. Blends containing 20% and 40% PT with diesel were tested in a 4-cylinder, 4-stoke DI diesel engine. The blends are stable and readily formed. Little difference in engine performance relative to diesel was found for 20% PT blends. PT blends (40%) exhibit significantly higher in-cylinder gas temperature and pressure. Ignition delay for both blends is longer than diesel, as is the fuel burn rate during the premixed stage of the combustion. During the diffusion stage of combustion, the fuel burn rate is lower relative to diesel. The performance of engines fuelled by blends containing 40% or more PT could be improved through optimization of engine systems.     

Effect of natural gas enrichment with hydrogen on combustion characteristics of a dual fuel diesel engine

Environmental benefits are one of the main motivations encouraging the use of natural gas as fuel for internal combustion engines. In addition to the better impact on pollution, natural gas is available in many areas. In this context, the present work investigates the effect of hydrogen addition to natural gas in dual fuel mode, on combustion characteristics improvement, in relation with engine performance. Various hydrogen fractions (10, 20 and 30 by v%) are examined. Results showed that natural gas enrichment with hydrogen leads in general to an improved gaseous fuel combustion, which corresponds to an enhanced heat release rate during gaseous fuel premixed phase, resulting in an increase in the in-cylinder peak pressure, especially at high engine load (4.1 bar at 70% load). The highest cumulative and rate of heat release correspond to 10% Hydrogen addition. The combustion duration of gaseous fuel combustion phase is reduced for all hydrogen blends. Moreover, this technique resulted in better combustion stability. For all hydrogen test blends, COV_IMEP does not exceed 10%. However, no major effect on combustion noise was noticed and the ignition delay was not affected significantly. Regarding performance, an important improvement in energy conversion was obtained with almost all hydrogen blends as a result of improved gaseous fuel combustion. A maximum thermal efficiency of 32.5%, almost similar to the one under diesel operation, and a minimum fuel consumption of 236 g/kWh, are achieved with 10% hydrogen enrichment at 70% engine load.     

Performance, emission and combustion characteristics of biodiesel fuelled variable compression ratio engine

Experiments has been carried out to estimate the performance, emission and combustion characteristics of a single cylinder; four stroke variable compression ratio multi fuel engine fuelled with waste cooking oil methyl ester and its blends with standard diesel. Tests has been conducted using the fuel blends of 20%, 40%, 60% and 80% biodiesel with standard diesel, with an engine speed of 1500 rpm, fixed compression ratio 21 and at different loading conditions. The performance parameters elucidated includes brake thermal efficiency, specific fuel consumption, brake power, indicated mean effective pressure, mechanical efficiency and exhaust gas temperature. The exhaust gas emission is found to contain carbon monoxide, hydrocarbon, nitrogen oxides and carbon dioxide. The results of the experiment has been compared and analyzed with standard diesel and it confirms considerable improvement in the performance parameters as well as exhaust emissions. The blends when used as fuel results in the reduction of carbon monoxide, hydrocarbon, carbon dioxide at the expense of nitrogen oxides emissions. It has found that the combustion characteristics of waste cooking oil methyl ester and its diesel blends closely followed those of standard diesel.     

直喷压燃式发动机燃用柴油/碳酸二甲酯的燃烧特性和放热过程研究

在一台直喷式发动机上开展了燃用柴油／碳酸二甲酯混合燃料的燃烧特性与放热过程研究。结果表明，随碳酸二甲酯含量的增加，预混燃烧推迟，扩散燃烧期缩短。在中高负荷区，相同平均有效压力下，缸内最高压力、最高压力升高率和最大放热率随碳酸二甲酯含量的增加而增加，而在低负荷区基本上不随碳酸二甲酯含量的增加而改变。着火滞燃期随碳酸二甲酯含量的增加而增加，而快速燃烧期和燃烧持续期不随碳酸二甲酯含量的变化而改变。随碳酸二甲酯含量的增加，燃油消耗率增加，等热值燃油消耗率降低。CO和烟度随碳酸二甲酯含量的增加而降低，NOx随碳酸二甲酯含量的变化，但变化不大。     

Impact of HHO gas enrichment and high purity biodiesel on the performance of a 315 cc diesel engine

Biodiesel and oxyhydrogen (HHO) gas have shown promising results in improving engine performance and emissions. In this work, the effects of HHO gas and 5% biodiesel blends (B5) and their combined use in a 315 cc diesel engine have been analyzed. Biodiesel is produced by base catalyzed transesterification and cleaned by emulsification. Its calculated cetane index (CCI) was 61.4. HHO gas is produced from electrolysis of concentrated potassium hydroxide solution. The use of 5% biodiesel blend resulted in a significant rise of 9.4% in the brake thermal efficiency (BTE) and a maximum reduction of 8.19% in the brake specific fuel consumption (BSFC). HHO enrichment of diesel and biodiesel at 2.81 L/min through the intake manifold improved the torque and power by an average of over 3%. HHO addition also improved the BTE of diesel by a maximum of 3.67%. The combination of high CCI biodiesel fuel and HHO creates a mixture that has shortened the ignition delay (ID) to the point that adverse effects were observed due to the premature combustion as shown by the average decrease in the BTE of 2.97% compared to B5. Thus, B5, on its own, is found to be the optimum fuel under these conditions.     

大豆生物柴油低温燃烧特性研究

对纯大豆生物柴油(B100)、普通柴油(B0)及其混合燃料(B20和B50)的低温燃烧特性在定容燃烧室中进行了试验研究。对各燃油在800 K环境温度下的燃烧压力、放热率、贯穿距离和碳烟量特性进行了测量。试验结果表明:随着燃油内生物柴油量的增加,缸内最高燃烧压力有所下降,着火延迟时间变短。燃油贯穿距离随着燃油内生物柴油量的增加而变长,但B50和B100的贯穿距离没有明显差别。低温燃烧时碳烟量明显降低,且燃油燃烧过程中的最大碳烟量随着燃油中生物柴油量的增加而降低。