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This paper describes the fuel properties, combustion characteristics and exhaust emissions of the methyl esters of saturated fatty acid with 6 to 10 carbons in the molecule chain. The fuels blend (50/50 mass%) of three saturated fatty acid methyl esters (methyl caproate, methyl caprylate, methyl caprate); with methyl laurate as a base fuel are tested using a DI diesel engine. From the experimental results, the blend of saturated fatty acid methyl ester with a lower carbon number has a lower kinematic viscosity, pour point and smoke emission, though having longer ignition delay, the same as long chain saturated fatty acid methyl ester.

This paper investigates the performance, exhaust emissions, and combustion characteristics of a dual fuel diesel engine fueled by CNG (compressed natural gas) as the main fuel. The experiments used a small single cylinder DI diesel engine and two kinds of fuels for the ignition: FAME (fatty acid methyl ester) fuels such as Methyl Oleate (OME) and OME-Methyl Palmitate (PME) blends, major components of biodiesel, and ordinary gas oil. The rate of the CNG supply was defined as the proportion of the heat energy of the supplied CNG to the total heat energy available in the cylinder. Compared with gas oil ignition, the FAME fuels had shorter ignition delays and significantly reduced smoke densities regardless of the PME contents. The PME contained in the FAME fuels gave rise to slight improvements in ignitability. The results also showed that the conditions where operation with CNG/FAME fuels is possible are very similar to those of the CNG/gas oil.

In order to improve the cold flow properties of coconut oil biodiesel and to reduce the lifecycle CO2 emission by using bio-alcohol at biodiesel manufacturing, varying the types of alcohol used at transesterification was examined. The pour point of coconut oil ester decreases as the carbon number of alcohol increases. Among 5 ester fuels, the pour point of coconut oil isobutyl ester (CiBE) made from isobutanol is lowest, −12.5 °C, compared to that of coconut oil methyl ester (CME), highest, −5 °C. The pour point of coconut oil 1-butyl ester (CBE) is −10 °C, second lowest. Furthermore, CBE, CiBE, CME and JIS No.2 diesel fuel (gas oil) were tested using a DI diesel engine. CBE and CiBE have shorter ignition delay compared to the gas oil although slightly longer than CME. CBE and CiBE have the same thermal efficiency and NOx emissions compared to the gas oil. HC, CO and Smoke emissions of coconut oil ester fuels slightly increase when the ester molecule carbon number increases.

In order to reduce the smoke emission of PME/1-butanol blend by increasing the 1-butanol content, PME/1-butanol blend is tested using a DI diesel engine with jerk-type fuel injection pump. With PME/1-butanol blend, there is no problem on the start-ability and stability of the engine operation up to 60 mass% of 1-butanol. On the other hand, with gas oil/1-butanol blend, there is no problem on those up to 40 mass% of 1-butanol. The PME/1-butanol blend has longer ignition delay compared with PME due to the low cetane number of 1-butanol. With increasing 1-butanol content, the smoke emissions of PME/1-butanol blend decrease although the HC and CO emissions increase due to the longer ignition delay.

To utilize bio-butanol as an alternative diesel fuel, the effect of butanol isomer, where 1-butanol, 2-butanol and isobutanol were studied except for tert-butanol, on the combustion characteristics and exhaust emissions of butanol/gas oil blend was investigated using a DI diesel engine without modification of engine parameters. First, to understand the effect of butanol content on the diesel combustion, engine test was carried out using blends of 1-butanol which contents were 10 to 50 mass%. With increasing 1-butanol content, the Smoke emission reduces although the ignition delay gets longer and the HC and CO emissions increase especially at low load. The engine operation is stable except for full load with 1-butanol 50 mass% blend. From the above experimental results, butanol isomer blending ratio is set to 40 mass%.

This paper describes how cooling loss reductions influence engine performance with emulsified fuel operation. The cooling loss ϕw during combustion was determined from the gas pressure in the cylinder at various conditions and the cooling water loss ϕc through the whole of the engine cycle was measured by changing the cooling water temperature. It was found that the indicated thermal efficiency varies with the change in cooling loss ϕw and cooling water loss ϕc versus the change of cooling water temperature. As a feature of emulsified fuel combustion it was determined that the reduced cooling loss improves the indicated thermal efficiency.

Micro-explosions and vaporizing behaviors of droplets of various emulsified fuels were investigated to determine the influence of emulsified fuel properties such as water content, water particle size, and viscosity of base fuel on combustion in a diesel engine. The investigation used gas oil, A heavy oil, and B heavy oil mixed with water and evaporated on a hot surface under atmospheric pressure. The influence on the engine performance was also investigated. It was confirmed that the viscosity of the base fuel, the water content, and the water particle size influenced the droplet evaporation on the hot surface and the occurrence and intensity of micro-explosions. There were remarkable differences in the BSFC for emulsified fuels in or outside the range where micro-explosions occurred on the hot surface.

The present study investigated the effect of boost pressure on the operation of a small single cylinder DI diesel engine equipped with a jerk type injection system fueled by different biodiesel fuels. The study employed a Roots blower type supercharger driven by a motor, and the boost pressures were varied from 100 kPa (naturally aspirated condition) to 140 kPa. The experiments used three kinds of biodiesel: rapeseed oil methyl ester (RME), soybean oil methyl ester (SME), and coconut oil methyl ester (CME). Further, a blended fuel with 60% (mass) CME and 40% 1-butanol (represented as CMEB) was also used. The influence of the boost pressure on the engine performance, combustion characteristics, and exhaust emissions with the abovementioned four biofuels were examined and compared with standard JIS No. 2 diesel fuel.

This paper describes the influence of different kinds of FAME (fatty acid methyl ester) on the smoke emissions of a small single cylinder DI diesel engine and the soot formation characteristics in suspended single droplet combustion. The study used eight kinds of commercial FAME and diesel fuel blends. The tested FAMEs are saturated fatty acids with 8 to 18 carbon molecule chains, and with three different double bonds with C18. The results show that with all the FAME mixtures here, the brake thermal efficiencies with the FAME-diesel fuel blends were similar to neat diesel fuel operation while the smoke emissions with all of the tested FAME-diesel fuel blends were lower. To examine the differences in the soot formation characteristics, measurements of the formed soot mass were also performed with a basic experimental technique with suspended single droplet combustion. The soot was trapped on a glass fiber filter, and the mass of the filter was measured with an electronic microbalance.

A number of studies in diesel dual fuel (DDF) operation which introduces natural gas from the intake pipe and ignites it by a diesel fuel injection in the combustion chamber have been conducted using conventional diesel engines. The present study investigated the influence of the ignition fuel on engine performance, combustion characteristics, and emissions with a combination of EGR and supercharging in DDF operation. The experiments employed iso-pentanol blended fuels for the ignition. Isopentanol is a next generation bio-alcohol fuel produced from cellulosic biomass, and actual use can be expected. The experiments were conducted at two CNG supply rates, 0% (ordinary diesel operation) and at a 40±4% (DDF operation) energy basis, and with EGR rates varied from 0 to 26%. The boost pressure was set at two conditions, 100 kPa (naturally aspirated, N/A) and 120 kPa (supercharged, S/C) with a supercharger.

This paper investigates the combined effect of EGR and emulsified fuels on engine performance. The influence of intake air temperature (25∼86°C) on engine performance was examined prior to uncooled EGR experiments. Compared with gas oil, emulsified fuel gave simultaneous improvements in NOx concentration, smoke density, and specific fuel consumption (BSFC) over the tested range. The effect of EGR on engine performance were investigated with various water to fuel ratios at two load conditions (BMEP=0.52MPa and 0.26MPa). It was confirmed that at 11% EGR with the emulsified fuel at the rated output resulted in a significant reduction in NOx concentration without worsening smoke density and BSFC.

This investigation reports how rapeseed oil blended with gas oil influences performance and emissions of a small single cylinder DI diesel engine. The paper also investigates evaporation and combustion characteristics of the blended fuels with basic experiments of single droplet evaporation on a hot plate and suspended droplet combustion. The results showed that the smoke density decreased when the rapeseed oil addition rates, y are equal to or higher than 50%. Compared with gas oil operation, equal proportions of gas oil and rapeseed oil (y=50%) or fuels with lower rapeseed oil ratios showed quite similar BSEC (specific energy consumption) and combustion characteristics. The droplet evaporation experiments on a hot plate showed that the maximum boiling rate point of the blend with equal proportions of gas oil and rapeseed oil is about 720K, intermediate between the two fuels. The results of the suspended droplet combustion showed different trends in ignitability.

This paper investigates the performance, combustion characteristics, and emissions of a small single cylinder DI diesel engine with biodiesel fuel (BDF) derived from unused rape, soybean, and palm oils. Compared with ordinary gas oil, the BDFs showed similar brake thermal efficiencies, better ignitability, and considerably reduced smoke densities, while the NOx emissions were somewhat higher. The injection characteristics and engine performance were also examined using neat Methyl Oleate (OME) and OME-Methyl Palmitate (PME) blends. Basic experiments of suspended single droplets were performed to evaluate the differences in ignition, combustion, and soot formation characteristics of these fuels. The results showed shorter ignition lags and combustion durations for the OME droplets blended with PME and the soot formation rate with OME is about 13% that of gas oil droplets.

This investigation reports how water emulsification influences spray characteristics, combustion characteristics, and engine performance and emissions using equal proportions of rapeseed oil and gas oil as the base fuel. The experiments used two types of DI diesel engines with different combustion chambers and injection systems. The results showed that the NOx emissions and smoke densities with the emulsified fuel decreased remarkably although the spray angle decreases and atomization becomes poorer due to increasing kinematic viscosity. To discuss the influence of water addition on evaporation, ignition, and combustion characteristics, basic experiments with single droplets suspended from a quartz bar were also performed. The experiments used an electric furnace maintained at high temperatures (1133K) at atmospheric pressure. The quartz bar used has a spherical suspending part (0.6 mm diameter), and droplets were placed manually, quickly, in the chamber.

This investigation reports engine performance, combustion characteristics, and exhaust emissions with alternative diesel fuels of blends of vegetable oil and various fuel additives (fuel improving agents). To improve the oil viscosity and distillation characteristics, the study used liquid oxygenated agents with lower boiling points and higher volatility than gas oil. The experiments used rapeseed oil and eight kinds of oxygenates: ethanol, 1-propanol, 1-butanol, 1-pentanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, and dibutyl ether. An ordinary small single cylinder DI diesel engine was used and the blending ratio was defined as the volume %; the proportion of oxygenate in the fuel was from 0% (neat rapeseed oil) to 29 or 33%. The results showed that all of the above oxygenates except ethanol and 2-methoxyethanol had good solubility in rapeseed oil (by manual mixing) at room temperature.

Transesterified fuels (biodiesel fuels; BDF) from vegetable oils are alternative fuels for diesel engines, they are renewable and offer potential reductions in carbon dioxide emissions. Many studies have reported that exhaust from BDF has equal or higher NOx concentrations while HC and PM emissions are significantly lower than with gas oil. The aim of the present investigation is to achieve drastic reductions in NOx emissions. Performance tests of a single cylinder DI diesel engine were conducted using water emulsified fuels from BDF and gas oil with varying water addition rates combined with cooled EGR. The result showed that at a rated output, the emulsified gas oil with water to base fuel volume ratio of 30% reduced NOx (from 1020ppm) to 190ppm with the 21% EGR condition maintaining the minimum BSEC value achieved with EGR free gas oil operation. However, the smoke density increased by 28%.

This investigation reports diesel engine performance of water-in-gas oil emulsified fuel and gas oil at compression ratios of 13.6, 15.6, and 17.0. It was confirmed that without worsening the specific fuel consumption, low compression ratios with emulsified fuel operation result in significant reductions in NOx concentration, reduced maximum combustion pressure, and decreased smoke density when compared with the 17.0 compression ratio for gas oil operation.

This paper investigates engine performance with a stable emulsified fuel including frying oil, composed of vegetable oils discarded from restaurants and households. To reduce the oil viscosity, equal proportions of used frying oil and gas oil were mixed and emulsions of this blended fuel and water were prepared. Performance tests of a single cylinder DI diesel engine showed that the Nox concentration and smoke density both reduced without worsening BSFC with water to fuel volume ratios of 15∼30% at a rated output. The engine was also operated with transesterified fuel from used frying oil, the so called “biodiesel”. The BSFC of neat biodiesel was lower than with gas oil at high loads and retarded injection timings, while the smoke density was reduced at all operating conditions.

To improve engine performance parameters such as smoke, NOx, and BSFC in a DI diesel engine, water-in-gas oil emulsified fuel was used without high pressure or high injection rate. It was confirmed that when compared with high pressure and high injection rate operation with gas oil, emulsified fuel gives significant reductions in NOx concentration, improved fuel economy, and reduced smoke density at ordinary injection pressure and retarded timings.