Experimental analysis of super-knock occurrence based on a spark ignition engine with high compression ratio
journal contributionposted on 08.10.2018 by Lei Zhou, Rui Kang, Haiqiao Wei, Dengquan Feng, Jianxiong Hua, Jiaying Pan, Rui Chen
Any type of content formally published in an academic journal, usually following a peer-review process.
The super-knock phenomenon is a major obstacle for further improving the power density in SI engines. The objective of this paper is to experimentally investigating the mechanism involved in the occurrence of super-knock. In this work, a high compression ratio (CR = 13) coupled with advanced spark timings were employed to achieving intense or critical thermal-dynamic conditions to easily inducing the super-knock. The results show that super-knock can originate from spark ignition, which is different from previous results regarding pre-ignition. Changing the spark timing super-knock can be induced with very high pressure oscillation at the present high compression ratio. The high compression ratio could generate sufficiently high thermal-dynamic conditions to inducing the abnormal combustion. In this research, four combustion phenomena were observed. The present work indicates that there is a nonlinear relationship between knock intensity and knocking onset in terms of pressure profiles at different cycles. The super-knock or knock phenomena were dominantly induced by spark ignition, which were controlled by the pre-ignition after several cycles. Finally, the analysis of the mechanism of super-knock with severe pressure oscillation was employed based on the thermal explosion theory and cavity resonances. There are two possible auto-ignition combustion modes that can induce the intense pressure oscillation.
This study is supported by the National Natural Science Foundation of China (Grant No. 91641203, 91741119, 51476114).
- Aeronautical, Automotive, Chemical and Materials Engineering
- Aeronautical and Automotive Engineering