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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.

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.