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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.

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.

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.

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.

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.

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 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.

Dual fuel diesel engines using compressed natural gas (CNG) are an attractive low polluting application, because natural gas is a clean low CO2 emitting fuel with superior resource availability. In dual fuel diesel engines with CNG as the main fuel the natural gas is supplied from the intake-pipe and the pre-mixture formed in the cylinder is spontaneously ignited by an injected spray of ordinary diesel fuel. Dual fuel engines of this type have the advantages that only limited engine modifications are needed and that low calorie gas fuels such as biogas can be used. To reduce NOx emissions in the dual fuel operation, the present study conducted the diesel combustion with a setup similar to that used with EGR. To dilute the intake air, the experiments used N2 or CO2 gases which are the major components of EGR. The diluent gas addition ratio was defined as the mass ratio of the supplied diluent to the intake charge which is composed of air and diluent.

Dual fuel diesel engines using compressed natural gas (CNG) are an attractive low polluting application, because natural gas is a clean low CO₂-emitting fuel with superior resource availability. In dual fuel diesel engines with natural gas as the main fuel the natural gas is supplied from the intake pipe and the pre-mixture formed in the cylinder is spontaneously ignited by an injected spray of ordinary gas oil. Dual fuel engines of this type have the advantages that only limited engine modifications are needed and that low calorie gas fuels such as biogas can be used. To clarify the influence of the cetane number (C.N.) of the ignition fuel on the ignition performance, combustion characteristics, and emissions of the dual fuel operation, the present study used standard ignition fuels prepared by n-hexadecane and heptamethylnonane which define the ignitability of diesel combustion.

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.

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 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 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.

Since there is a trade-off relationship between NOx and particulates in exhaust gas emitted from a diesel engine, simultaneous reduction of the amounts of NOx and particulates in a combustion chamber is difficult. However, the amount of particulates produced in the combustion process could be reduced in a state of almost complete combustion, and the amount of NOx produced during the combustion process could be reduced by the use of a catalyst and reducing agent in the exhaust process. It has been demonstrated that the use of ethanol as a reducing agent on a silver-base catalyst in the presence of oxygen is an effective means for reducing NOx, although the mechanism of the reduction has not been elucidated. Therefore, in the present study, an NOx-reduction apparatus was conducted, and model experiments on NOx reduction were carried out in an atmosphere simulating exhaust gas emitted from a diesel engine and at the same catalyst temperature as that in a combustion chamber.

Small two stroke SI engines supplied with natural gas in the intake port are advantageous for low maintenance and low cost when used in co-generation systems for residential use. However in the engines with port injection systems, the unburned HC emissions are higher and thermal efficiency is lower than with 4 stroke engines. To overcome these disadvantages, an in-cylinder injection with a special low pressure injection nozzle system was attempted. The results showed that improvements in unburned HC emissions and thermal efficiency are possible due to the remarkable reduction in scavenging loss and the lean combustion.

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 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.

Lean-burn engines now being developed employ in-cylinder injection which requires high pressures and so necessitates expensive injection equipment. The injection system proposed here is an air assisted in-cylinder injection system which is injecting a mixture of air and fuel in the cylinder during the intake stroke and allowing atomization at lower injection pressures than those necessary in compressing fuel with a usual solid injection. This time, the experiments used a testing engine of a 4 stroke gasoline OHV type replacing the Side Valve type. Performance with a small depression in the main combustion chamber was investigated with a spark plug and reed valve installed in the depression. The engine was operated then following the same method as last year (SAE 982698). As a result, the lean burn method employed here was possible over a wide range of engine speeds and loads. Moreover, it was also shown that this operation was possible with a fully opened throttle valve.

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.