Experimental analysis of super-knock occurrence based on a spark ignition engine with high compression ratio. (15th December 2018)

• Record Type: Journal Article
• Authors: Zhou, Lei; Kang, Rui; Wei, Haiqiao; Feng, Dengquan; Hua, Jianxiong; Pan, Jiaying; Chen, Rui
• Is Part Of: Energy. Volume 165(2018)Part B
• Page Start: 68
• Page End: 75
• Publication Date: 2018-12-15
• Subjects: Super-knock -- Pre-ignition -- High compression ratio -- Pressure oscillation -- Combustion modes; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2018.09.166
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: 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. Highlights: The cause of super-knock occurrence is comprehensively studied. Pre-ignition is not a unique condition leading to super-knock. There is no direct relationship between super-knock intensity and super-knock onset. The fundamental theories were employed to explaining the mechanism.