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In this study, premixed charge compression ignition (PCCI) combustion was implemented using an injector that had a narrow injection angle of 70° and a moderately early injection timing of -40° crank angle after top dead center (CA ATDC). In-cylinder pressure measurements and high-speed direct imaging of the flame were performed in an optically accessible single-cylinder diesel engine. Frequency analysis of the acquired in-cylinder pressure data was carried out to obtain the frequency range of diesel knock. Meanwhile, image segmentation and a tracking algorithm based on YCbCr color space were implemented to determine the frequency range of diesel knock from the obtained high-speed image. The results show that the frequency of diesel knock was dominated by the range from 13 kHz to 15 kHz. Still, frequency with low power existed down until 7 kHz. The frequencies of the area movement were shown to be 13 kHz and, in some cases, 8.67 kHz.

Low Temperature Combustion (LTC) is known to be feasible only in lower load ranges so in real world application of LTC, engine operation mode should frequently change back and forth between LTC mode in lower loads and conventional mode in higher loads. In this research, effect of injection strategy on smoothness and emissions during mode transition in a single cylinder heavy duty diesel engine is studied. The Exhaust Gas Recirculation (EGR) line was controlled by a servo-valve capable of opening or closing the EGR loop within only one engine cycle. Ten cycles after the EGR valve closure were taken as the transition period during which injection timing and quantity were shifted in various ways (i.e. injection strategies) and the effect on Indicated Mean Effective Pressure (IMEP) stability and emissions was studied.