Analysis of Diesel Knock for High-Altitude Heavy-Duty Engines Using Optical Rapid Compression Machines

Xiangting Wang, Haiqiao Wei, Jiaying Pan, Zhen Hu, Zeyuan Zheng and Mingzhang Pan
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Xiangting Wang: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Haiqiao Wei: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Jiaying Pan: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Zhen Hu: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Zeyuan Zheng: School of Mechanical Engineering, Guangxi University, Nanning 530004, China
Mingzhang Pan: School of Mechanical Engineering, Guangxi University, Nanning 530004, China

Energies, 2020, vol. 13, issue 12, 1-14

Abstract: In high altitude regions, affected by the low-pressure and low-temperature atmosphere, diesel knock is likely to be encountered in heavy-duty engines operating at low-speed and high-load conditions. Pressure oscillations during diesel knock are commonly captured by pressure transducers, while there is a lack of direct evidence and visualization images, such that its fundamental formation mechanism is still unclear. In this study, optical experiments on diesel knock with destructive pressure oscillations were investigated in an optical rapid compression machine. High-speed direct photography and simultaneous pressure acquisition were synchronically performed, and different injection pressures and ambient pressures were considered. The results show that for the given ambient temperature and pressure, diesel knock becomes prevalent at higher injection pressures where fuel spray impingement becomes enhanced. Higher ambient pressure can reduce the tendency to diesel knock under critical conditions. For the given injection pressure satisfying knocking combustion, knock intensity is decreased as ambient pressure is increased. Further analysis of visualization images shows diesel knock is closely associated with the prolonged ignition delay time due to diesel spray impingement. High-frequency pressure oscillation is caused by the propagation of supersonic reaction-front originating from the second-stage autoignition of mixture. In addition, the oscillation frequencies are obtained through the fast Fourier transform (FFT) analysis.

Keywords: diesel knock; rapid compression machine; spray impingement; auto-ignition; reaction front propagation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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