Numerical and Experimental Study on Knock Sources in Spark Ignition Engine with Electromagnetic Valve Train
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ght © 2020 KSAE/ 11804 pISSN 12299138/ eISSN 19763832
NUMERICAL AND EXPERIMENTAL STUDY ON KNOCK SOURCES IN SPARK IGNITION ENGINE WITH ELECTROMAGNETIC VALVE TRAIN Jiangtao Xu1), Yong Feng1)*, Siqin Chang2) and Tongjun Guo2) School of Mechanical Engineering, Nanjing Institute of Industry Technology, Nanjing 211167, China School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China 1)
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(Received 25 October 2019; Revised 18 December 2019; Accepted 4 January 2020) ABSTRACTAs one of the most common engine types in nowadays, the thermal efficiency of spark-Ignition (SI) engine is limited due to the lower compression ratio. Various technical solutions have been proposed to suppress knock and improve compression ratio of SI engines. In this paper, an new technical solution based on electromagnetic valve train (EMVT) was proposed to suppress knock of spark ignition engines, so that high compression ratio (HCR) engine (13:5) was obtained. Moreover, experimental and numerical analyses were carried out to optimize the proposed EMVT strategy. The result showed that the proposed EMVT strategies could well suppress the engine knock by reducing end-gas temperature and pressure and improving the spark-flame rate, resulting in significantly enhanced power, economic, and emission characteristics of SI engines. This study provides theoretical basis and technical approach for the development of internal combustion engines with high efficiency and high compression ratio. KEY WORDS : High compression ratio, Knock, Exhaust gas recirculation, Electromagnetic valve train, Miller cycle
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significance to develop more high-effciency gasoline engines with reduced greenhouse emissions and energysaving feature (Kalghatgi, 2018). Literature review shows that each unit increase in compression ratio will lead to 1 ~ 3 % increase in the thermal efficiency of gasoline engine (Goswami et al., 2015). Engine knocking is an abnormal combustion phenomenon resulted from auto-ignition of the end-gas before the spark-flame front arrives, engine knocking will intensify with the effective compression ratio (ECR). The occurrence of engine knocking mainly depends on the endgas temperature and pressure as well as the spark-flame development rate (Mane et al., 2019). Therefore, restraining engine knock is of great importance for further improvement of engine’s thermal efficiency. Engine knock is usually avoided by optimizing ignition advance angle, air-fuel ratio, fuel composition (Fu et al., 2017), and the shape of combustion chamber (Ravi and Porpatham, 2017). However, these measures are carried out at the sacrifice of engine output performance (Marseglia et al., 2017). Therefore, it is necessary to develop more efficient technical means to suppress HCR engine knock (Ravi et al., 2017). At present, various technical solutions have been proposed to improve the engine performance under partial load operation and full load operation (Li et al., 2017). The fully flexible valve technique appears a very robust
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