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A rapid compression/expansion machine (RCEM) based on a single-cylinder engine was developed to understand the fundamental phenomenon of knock during spark-ignition (SI) combustion. In order to cause auto-ignition in the end-gas mixture during the flame-propagation process, and also to visualize the processes, the original head of the engine was replaced with a specially designed combustion chamber. The effects of spark timing, compression ratio and equivalence ratio on knock intensity were systematically investigated using the RCEM with n-butane fuel. In addition, the possibility of knock control by the injection of hydrogen into the end-gas region is also discussed. The experimental results indicate that a higher compression ratio, spark-ignition timing at -10 °ATDC and a stoichiometric equivalence ratio cause heavy knock. However, the knock intensity is drastically decreased with hydrogen injection.

The effects of biodiesel oxidation stability on diesel fuel injection equipment (FIE) behavior were investigated using newly developed test rig and methodology. On the test rig, biodiesel blend fuels were circulated through a fuel tank and a common rail injection system. Fuel injected from typical diesel injectors was returned into the fuel tank to enhance the speed of fuel degradation. The results showed that injector deposits could be reproduced on a test rig. It was observed that injector body temperature increase accelerates the degradation of fuel and therefore gives earlier FIE failure. Fuel renewal could partially restore the injection quantity after complete failure at low injection pressure, thus showing a potential cleaning effect on injector deposits when refueling a car.

Utilizing the desirable feature of hydrogen, this study demonstrates the improvement of engine performance and exhaust emissions due to the mixing of hydrogen into natural-gas fuel in a spark-ignition engine at the wide-open throttle (WOT) condition. Both hydrogen and natural-gas fuels were injected into the intake port only in the suction flow, which could make the operation under a wide range of conditions without backfire even at a hydrogen fuel. Based on the measured processes of combustion, the knock characteristics were discussed with special attention to the extremely high burning velocity of hydrogen. At a higher compression ratio, the thermal efficiency in the stoichiometric condition was improved, nevertheless a precise control of ignition timing was required to suppress a hard knock. From the experimental results of engine performance in a variety of parameters, optimal use of hydrogen was exhibited for different engine loads.

The Premixed Charge Compression Ignition (PCCI) natural-gas engine has been investigated extensively as a power source for stationary applications due to its potential for high thermal efficiency and very low NOx emissions. However, methane, which is a major component of natural gas, has a high auto-ignition temperature. Stable ignition of natural gas in PCCI engines can be achieved by high compression ratio, intake air heating, internal EGR and various other techniques. Although each of the above-mentioned methods shows positive effects, to some extent, on engine performance and emissions, the literature indicates that stable operation of the PCCI natural gas engine would require a combination of various techniques, which reveals the need for further investigation. The goal of the present study is to control the PCCI natural gas ignition and combustion by ozone addition into the intake air.

Utilization of ethanol-diesel blend fuels in partial Premixed Charge Compression Ignition (PCCI) combustion was attempted to achieve clean diesel engine. The experiment was carried out using a naturally aspirated single cylinder DI diesel engine equipped with common rail injection and cooled EGR systems. PCCI combustion was realized by two stage injection in which part of fuel was injected during the compression stroke and the rest near TDC. The results indicate that under middle to high engine loads, both weak sooting tendency and low cetane number of ethanol blend fuels offer a great improvement in PM and NOx emissions when compared to the diesel combustion with ordinary pilot injection. However, this results in penalties in thermal efficiency, THC and CO emissions.

Ethanol is a bio-based renewable and oxygenated fuel, thereby providing potential to reduce the PM emission in diesel engines and to provide reduction in life cycle CO2. There are several studies which report improvement in the engine performance using ethanol blend fuels. However, most of these studies are carried out using diesel engines with basic combustion control technologies. Therefore, it is doubtful whether a diesel engine fuelled with ethanol blend fuels can compete with the recently developed clean diesel engines. From another point of view, it is important to know whether it is possible to overcome the disadvantages of ethanol blend fuels using modern diesel engines. The aim of this study is to find strategies for fully utilizing the advantages of diesel-ethanol blends in the recent diesel engines. For this purpose, experiments were performed using a single-cylinder DI diesel engine equipped with common rail injection and cold EGR systems.