Study on combustion characteristics and particulate emissions of a common-rail diesel engine fueled with n-butanol and waste cooking oil blends

Biodiesel is a promising alternative fuel because of its renewability and extensive source of raw materials. Butanol can be blended in biodiesel to reduce the kinematic viscosity and promote the fuel atomization. In this respect, biodiesel was blended with 10% and 20% n-butanol, and the combustion characteristics and particulate emissions of the fuel blends were tested in a turbocharged, 6-cylinder, common rail diesel engine at a constant speed of 1400 rpm under seven engine loads. The experimental results show that under various engine loads, all of the butanol and biodiesel fuel blends provide faster combustion than diesel due to the higher oxygen content of n-butanol and the lower cetane number of butanol which results in stronger premixed combustion. The addition of butanol is beneficial to concentrating the heat release and thus shorten the combustion duration. With an increased proportion of butanol, soot emissions of butanol and biodiesel fuel blends decrease, the number concentration and volume concentration of ultrafine particles (UFPs) reduce noticeably. Meanwhile, the geometric mean diameters of UFPs decrease with an increase in butanol. With an increase of the engine loads, the number concentration peaks of UFPs gradually transfer from the size range of nucleation mode particles (NMPs) to the size range of accumulation mode particles (AMPs) due to the elevated combustion temperatures and high equivalence ratios. Moreover, biodiesel and fuel blends exhibit a higher percentage of NMPs as compared to diesel because of the fuel-bound oxygen, zero aromatics, and low sulfides.     

Progress in biodiesel processing

Biodiesel is a notable alternative to the widely used petroleum-derived diesel fuel since it can be generated by domestic natural sources such as soybeans, rapeseeds, coconuts, and even recycled cooking oil, and thus reduces dependence on diminishing petroleum fuel from foreign sources. The injection and atomization characteristics of the vegetable oils are significantly different than those of petroleum-derived diesel fuels, mainly as the result of their high viscosities. Modern diesel engines have fuel-injection system that is sensitive to viscosity change. One way to avoid these problems is to reduce fuel viscosity of vegetable oil in order to improve its performance. The conversion of vegetable oils into biodiesel is an effective way to overcome all the problems associated with the vegetable oils. Dilution, micro-emulsification, pyrolysis, and transesterification are the four techniques applied to solve the problems encountered with the high fuel viscosity. Transesterification is the most common method and leads to monoalkyl esters of vegetable oils and fats, now called biodiesel when used for fuel purposes. The methyl ester produced by transesterification of vegetable oil has a high cetane number, low viscosity and improved heating value compared to those of pure vegetable oil which results in shorter ignition delay and longer combustion duration and hence low particulate emissions.     

Combustion performance and emission reduction characteristics of automotive DME engine system

This article is a condensed overview of a dimethyl ether (DME) fuel application for a compression ignition diesel engine. In this review article, the spray, atomization, combustion and exhaust emissions characteristics from a DME-fueled engine are described, as well as the fundamental fuel properties including the vapor pressure, kinematic viscosity, cetane number, and the bulk modulus. DME fuel exists as gas phase at atmospheric state and it must be pressurized to supply the liquid DME to fuel injection system. In addition, DME-fueled engine needs the modification of fuel supply and injection system because the low viscosity of DME caused the leakage. Different fuel properties such as low density, viscosity and higher vapor pressure compared to diesel fuel induced the shorter spray tip penetration, wider cone angle, and smaller droplet size than diesel fuel. The ignition of DME fuel in combustion chamber starts in advance compared to diesel or biodiesel fueled compression ignition engine due to higher cetane number than diesel and biodiesel fuels. In addition, DME combustion is soot-free since it has no carbon–carbon bonds, and has lower HC and CO emissions than that of diesel combustion. The NO_x emission from DME-fueled combustion can be reduced by the application of EGR (exhaust gas recirculation). This article also describes various technologies to reduce NO_x emission from DME-fueled engines, such as the multiple injection strategy and premixed combustion. Finally, the development trends of DME-fueled vehicle are described with various experimental results and discussion for fuel properties, spray atomization characteristics, combustion performance, and exhaust emissions characteristics of DME fuel.     

Assessing idling effects on a compression ignition engine fueled with Jatropha and Palm biodiesel blends

In this study, performance of a diesel engine operated with Jatropha and Palm biodiesel blends at high idling conditions has been evaluated. The result obtained from experiment elucidate that, at all idling modes HC and CO emissions of both blends decreases, however, NO_x emissions increases compared to pure diesel fuel. Jatropha biodiesel has higher viscosity compared to Palm biodiesel, which might have degraded the spray characteristics and caused slightly improper mixing which might have led to slightly incomplete combustion, thus at both idling conditions, Jatropha blends emitted higher CO and HC compared to Palm biodiesels. Compared to diesel fuel, CO emissions were 5.9–9.7%, 17.6–22.6%, 23.5–29%, 2.9–6.4%, 5.9–14.5% and 11.8–17.74% less, HC emissions were 10.3–11.5%, 24.13–30.76%, 34.5–39%, 6.9–7.7%, 26–27% and 31–35% less and NO_x emissions were 8.3–9.5%, 14–15%, 22–25%, 5–7.14%, 10–11.3% and 17–18% more respectively for 5, 10 and 20% blends of Palm and Jatropha biodiesel. Compared to diesel fuel, at high idling conditions brake specific fuel consumption all Palm and Jatropha biodiesel–diesel blends increased. Compared to diesel fuel, BSFC were 1.14–1.35%, 2.28–2.96%, 7.1–8.35%, 2.28–2.69%, 3.98–5.39% and 8.83–9.29% more respectively for 5, 10 and 20% blends of Palm and Jatropha biodiesel.     

Performance and emission characteristics of a Kirloskar HA394 diesel engine operated on fish oil methyl esters

The high viscosity of fish oil leads to problem in pumping and spray characteristics. The inefficient mixing of fish oil with air leads to incomplete combustion. The best way to use fish oil as fuel in compression ignition (CI) engines is to convert it into biodiesel. It can be used in CI engines with very little or no engine modifications. This is because it has properties similar to mineral diesel. Combustion tests for methyl ester of fish oil and its blends with diesel fuel were performed in a kirloskar H394 DI diesel engine, to evaluate fish biodiesel as an alternative fuel for diesel engine, at constant speed of 1500 rpm under variable load conditions. The tests showed no major deviations in diesel engine's combustion as well as no significant changes in the engine performance and reduction of main noxious emissions with the exception on NO_x. Overall fish biodiesel showed good combustion properties and environmental benefits.     

Droplet Combustion Characteristics of Biodiesel–Diesel Blends using High Speed Backlit and Schlieren Imaging

This work investigates the effect of blending biodiesel with diesel on the combustion of an isolated fuel droplet. Biodiesel blends substituting diesel oil in different concentrations on volumetric basis, in addition to neat diesel and biodiesel, were studied. High-speed Schlieren and backlighting imaging techniques have been used to track droplet combustion. The results showed that partial substitution of diesel oil by biodiesel at the test conditions led to increasing secondary atomization from the droplet, compared to neat diesel or biodiesel fuel droplets. This in turn enhances evaporation, mixing, and then combustion. Additionally, the results showed that biodiesel has a higher burning rate compared to diesel, and that increasing biodiesel in the blend increases the burning rate of the blend. Nucleation has also been traced to take place inside the droplets of the blends. Moreover, flame size (height and width) has been reduced by increasing biodiesel concentration in the blend.     

A review on biodiesel production,combustion, emissions and performance

This article is a literature review on biodiesel production, combustion, performance and emissions. This study is based on the reports of about 130 scientists who published their results between 1980 and 2008. As the fossil fuels are depleting day by day, there is a need to find out an alternative fuel to fulfill the energy demand of the world. Biodiesel is one of the best available sources to fulfill the energy demand of the world. More than 350 oil-bearing crops identified, among which some only considered as potential alternative fuels for diesel engines. The scientists and researchers conducted tests by using different oils and their blends with diesel.A vast majority of the scientists reported that short-term engine tests using vegetable oils as fuels were very promising but the long-term test results showed higher carbon built up and lubricating oil contamination resulting in engine failure. They concluded that vegetable oils, either chemically altered or blended with diesel to prevent the engine failure. It was reported that the combustion characteristics of biodiesel are similar as diesel and blends were found shorter ignition delay, higher ignition temperature, higher ignition pressure and peak heat release. The engine power output was found to be equivalent to that of diesel fuel. In addition, it observed that the base catalysts are more effective than acid catalysts and enzymes.     

Nozzle flow and atomization characteristics of ethanol blended biodiesel fuel

This study was conducted to investigate the injection and atomization characteristics of biodiesel–ethanol blended fuel. The injection performance of biodiesel–ethanol blended fuel was analyzed from the injection rate characteristics using the injection rate measuring system, and the effective injection velocity and effective spray diameter using the nozzle flow model. Moreover, the atomization characteristics, such as local and overall SMD distributions, overall axial velocity and droplet arrival time were analyzed and compared with these from diesel and biodiesel fuels to obtain the atomization characteristics of biodiesel–ethanol blended fuel.It was revealed that ethanol fuel affects the decrease of the peak injection rate and the shortening of the injection delay due to the decrease of fuel properties, such as fuel density and dynamic viscosity. In addition, the ethanol addition improved the atomization performance of biodiesel fuel, because the ethanol blended fuel has a low kinematic viscosity and surface tension, then that has more active interaction with the ambient gas, compared to BD100.     

Exhaust emission study on neat biodiesel and alcohol blends fueled diesel engine

In this study, neat biodiesel with octanol additive was employed in a diesel engine and its effects on engine emission were studied. The five fuels evaluated were neat palm kernal oil biodiesel, octanol blended with biodiesel by 10%, 20%, and 30% volume, and diesel. All the emissions are reduced by the addition of octanol in biodiesel in all loads owing to the higher oxygen concentration of air/fuel mixtures and improved atomization. Hence, it is concluded that the neat biodiesel and octanol blends can be employed as an alternative fuel for existing unmodified diesel engines owing to its lesser emission characteristics.     

Combustion,emission and engine performance characteristics of used cooking oil biodiesel—A review

As the environment degrades at an alarming rate, there have been steady calls by most governments following international energy policies for the use of biofuels. One of the biofuels whose use is rapidly expanding is biodiesel. One of the economical sources for biodiesel production which doubles in the reduction of liquid waste and the subsequent burden of sewage treatment is used cooking oil (UCO). However, the products formed during frying, such as free fatty acid and some polymerized triglycerides, can affect the transesterification reaction and the biodiesel properties. This paper attempts to collect and analyze published works mainly in scientific journals about the engine performance, combustion and emissions characteristics of UCO biodiesel on diesel engine. Overall, the engine performance of the UCO biodiesel and its blends was only marginally poorer compared to diesel. From the standpoint of emissions, NOx emissions were slightly higher while un-burnt hydrocarbon (UBHC) emissions were lower for UCO biodiesel when compares to diesel fuel. There were no noticeable differences between UCO biodiesel and fresh oil biodiesel as their engine performances, combustion and emissions characteristics bear a close resemblance. This is probably more closely related to the oxygenated nature of biodiesel which is almost constant for every biodiesel (biodiesel has some level of oxygen bound to its chemical structure) and also to its higher viscosity and lower calorific value, which have a major bearing on spray formation and initial combustion.     

Experimental investigations on the effect of fuel injection parameters on diesel engine fuelled with biodiesel blend in diesel with hydrogen enrichment

Fuel injection pressure and injection timing are two extensive injection parameters that affect engine performance, combustion, and emissions. This study aims to improve the performance, combustion, and emissions characteristics of a diesel engine by using karanja biodiesel with a flow rate of 10 L per minute (lpm) of enriched hydrogen. In addition, the research mainly focused on the use of biodiesel with hydrogen as an alternative to diesel fuel, which is in rapidly declining demand. The experiments were carried out at a constant speed of 1500 rpm on a single-cylinder, four-stroke, direct injection diesel engine. The experiments are carried out with variable fuel injection pressure of 220, 240, and 260 bar, and injection timings of 21, 23, and 25 °CA before top dead center (bTDC). Results show that karanja biodiesel with enriched hydrogen (KB20H10) increases BTE by 4% than diesel fuel at 240 bar injection pressure and 23° CA bTDC injection timing. For blend KB20H10, the emissions of UHC, CO, and smoke opacity are 33%, 16%, and 28.7% lower than for diesel. On the other hand NOx emissions, rises by 10.3%. The optimal injection parameters for blend KB20H10 were found to be 240 bar injection pressure and 23 °CA bTDC injection timing based on the significant improvement in performance, combustion, and reduction in exhaust emissions.     

非直喷式增压柴油机燃用生物柴油的性能与排放特性

研究了非直喷式增压柴油机燃用柴油一生物柴油混合燃料的性能和排放特性。未对原机作任何调整和改动，研究了不同生物柴油掺混比例的混合燃料对功率、油耗、烟度和NOx排放的影响。结果表明：非直喷式柴油机燃用生物柴油后柴油机功率略有下降，油耗有所上升，烟度大幅下降，NOx排放增加明显。油耗、烟度和NOx的变化均与生物柴油掺混比例呈线性关系，合适的生物柴油掺混比例即可以保持柴油机的性能，又可有效地降低碳烟排放，且不引起NOx排放的显著变化。对于该增压柴油机，掺混生物柴油对外特性下的排放影响最大，影响最小的为标定转速下的负荷特性。不论是全负荷还是部分负荷，燃用生物柴油时低速下的烟度降低和NOx上升幅度均比高速时大，而同转速下高负荷时烟度降低和NOx上升更为明显。     

柴油机燃用大豆油甲酯的生命周期环境评价

近年来,生物柴油作为一种无毒的、可生物降解的、可再生的柴油机代用燃料倍受关注.但在选用其作为汽车代用燃料时,必须对其做出科学、客观的评估.为了能够正确评价生物柴油的能耗与排放,利用GREET1.7软件对柴油、大豆油甲酯和大豆油甲酯-柴油混合液的能耗和排放进行生命周期评价.研究结果表明,与柴油相比,随着掺混比的增大,能耗总量增大,化石燃料消耗减小,C02和GHGs排放降低,VOC、CO、NOxC02颗粒(PM 10和PM2.5)和SOx排放均升高.     

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.     

Using of cotton oil soapstock biodiesel–diesel fuel blends as an alternative diesel fuel

In this study, usability of cotton oil soapstock biodiesel–diesel fuel blends as an alternative fuel for diesel engines were studied. Biodiesel was produced by reacting cotton oil soapstock with methyl alcohol at determined optimum condition. The cotton oil biodiesel–diesel fuel blends were tested in a single cylinder direct injection diesel engine. Engine performances and smoke value were measured at full load condition. Torque and power output of the engine with cotton oil soapstock biodiesel–diesel fuel blends decreased by 5.8% and 6.2%, respectively. Specific fuel consumption of engine with cotton oil soapstock–diesel fuel blends increased up to 10.5%. At maximum torque speeds, smoke level of engine with blend fuels decreased up to 46.6%, depending on the amount of biodiesel. These results were compared with diesel fuel values.     

Comprehensive study of biodiesel fuel for HSDI engines in conventional and low temperature combustion conditions

In this research, an experimental investigation has been performed to give insight into the potential of biodiesel as an alternative fuel for High Speed Direct Injection (HSDI) diesel engines. The scope of this work has been broadened by comparing the combustion characteristics of diesel and biodiesel fuels in a wide range of engine loads and EGR conditions, including the high EGR rates expected for future diesel engines operating in the low temperature combustion (LTC) regime.The experimental work has been carried out in a single-cylinder engine running alternatively with diesel and biodiesel fuels. Conventional diesel fuel and neat biodiesel have been compared in terms of their combustion performance through a new methodology designed for isolating the actual effects of each fuel on diesel combustion, aside from their intrinsic differences in chemical composition.The analysis of the results has been sequentially divided into two progressive and complementary steps. Initially, the overall combustion performance of each fuel has been critically evaluated based on a set of parameters used as tracers of the combustion quality, such as the combustion duration or the indicated efficiency. With the knowledge obtained from this previous overview, the analysis focuses on the detailed influence of biodiesel on the different diesel combustion stages known ignition delay, premixed combustion and mixing controlled combustion, considering also the impact on CO and UHC pollutant emissions.The results of this research explain why the biodiesel fuel accelerates the diesel combustion process in all engine loads and EGR rates, even in those corresponding with LTC conditions, increasing its possibilities as alternative fuel for future DI diesel engines.     

Effect of straight vegetable oil blends and biodiesel blends on wear of mechanical fuel injection equipment of a constant speed diesel engine

Vegetable oils and biodiesel have emerged as strong alternative fuels worldwide. However use of new fuels in existing engines leads to issues such as wear of vital moving components, and fuel injection equipment (FIE). It is important to ensure that new alternative fuel does not affect the FIE adversely. In this experimental study, a non-firing engine FIE simulator test rig prototype was developed and 250 h endurance test of FIE was performed with an objective to ensure the long-term compatibility and durability of biofuel blends. The components of FIE such as plunger, nozzle needle, valve, and valve holder were investigated for wear. Test fuels used in this study were Karanja blends (K20, K5), Jatropha blends (J20, J5), Biodiesel blends (B20, B5) and baseline mineral diesel in a non-firing engine FIE simulator. The compatibility of FIE with test fuels in terms of dimensional loss, weight loss and surface texture variations using optical microscopy before and after the endurance test was compared. Biodiesel blends showed relatively lower wear compared to mineral diesel however SVO blends showed no definite trend of the wear results compared to baseline mineral diesel.     

The effect of biodiesel oxidation on engine performance and emissions

Biodiesel is an alternative fuel consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Previous research has shown that biodiesel-fueled engines produce less carbon monoxide, unburned hydrocarbons, and particulate emissions compared to diesel fuel. One drawback of biodiesel is that it is more prone to oxidation than petroleum-based diesel fuel. In its advanced stages, this oxidation can cause the fuel to become acidic and to form insoluble gums and sediments that can plug fuel filters. The objective of this study was to evaluate the impact of oxidized biodiesel on engine performance and emissions. A John Deere 4276T turbocharged DI diesel engine was fueled with oxidized and unoxidized biodiesel and the performance and emissions were compared with No. 2 diesel fuel. The neat biodiesels, 20% blends, and the base fuel (No. 2 diesel) were tested at two different loads (100 and 20%) and three injection timings (3° advanced, standard; 3° retarded). The tests were performed at steady-state conditions at a single engine speed of 1400 rpm. The engine performance of the neat biodiesels and their blends was similar to that of No. 2 diesel fuel with the same thermal efficiency, but higher fuel consumption. Compared with unoxidized biodiesel, oxidized neat biodiesel produced 15 and 16% lower exhaust carbon monoxide and hydrocarbons, respectively. No statistically significant difference was found between the oxides of nitrogen and smoke emissions from oxidized and unoxidized biodiesel.     

A study on the performance and emission of a diesel engine fueled with Jatropha biodiesel oil and its blends

Biodiesel either in neat form or as a mixture with diesel fuel is widely investigated to solve the twin problem of depletion of fossil fuels and environmental degradation. The main objective of the present study is to compare performance, emission and combustion characteristics of biodiesel derived from non edible Jatropha oil in a dual fuel diesel engine with base line results of diesel fuel. The performance parameters evaluated were: brake thermal efficiency, brake specific fuel consumption, power output. As a part of combustion study, in-cylinder pressure, rate of pressure rise and heat release rates were evaluated. The emission parameters such as carbon monoxide, carbon dioxide, un-burnt hydrocarbon, oxides of nitrogen and smoke opacity with the different fuels were also measured and compared with base line results. The different properties of Jatropha oil after transestrification were within acceptable limits of standards as set by many countries. The brake thermal efficiency of Jatropha methyl ester and its blends with diesel were lower than diesel and brake specific energy consumption was found to be higher. However, HC, CO and CO₂ and smoke were found to be lower with Jatropha biodiesel fuel. NO_x emissions on Jatropha biodiesel and its blend were higher than Diesel. The results from the experiments suggest that biodiesel derived from non edible oil like Jatropha could be a good substitute to diesel fuel in diesel engine in the near future as far as decentralized energy production is concerned. In view of comparable engine performance and reduction in most of the engine emissions, it can be concluded and biodiesel derived from Jatropha and its blends could be used in a conventional diesel engine without any modification.     

Properties and use of jatropha curcas oil and diesel fuel blends in compression ignition engine

In the present investigation the high viscosity of the jatropha curcas oil which has been considered as a potential alternative fuel for the compression ignition (C.I.) engine was decreased by blending with diesel. The blends of varying proportions of jatropha curcas oil and diesel were prepared, analyzed and compared with diesel fuel. The effect of temperature on the viscosity of biodiesel and jatropha oil was also studied. The performance of the engine using blends and jatropha oil was evaluated in a single cylinder C.I. engine and compared with the performance obtained with diesel. Significant improvement in engine performance was observed compared to vegetable oil alone. The specific fuel consumption and the exhaust gas temperature were reduced due to decrease in viscosity of the vegetable oil. Acceptable thermal efficiencies of the engine were obtained with blends containing up to 50% volume of jatropha oil. From the properties and engine test results it has been established that 40–50% of jatropha oil can be substituted for diesel without any engine modification and preheating of the blends.