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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 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 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.

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.

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%.