Effect of Injection Strategies in Diesel/NG Direct-Injection Engines on the Combustion Process and Emissions under Low-Load Operating Conditions

Jinze Li, Longfei Deng, Jianjun Guo, Min Zhang, Zhenyuan Zi, Jie Zhang and Binyang Wu
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Jinze Li: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Longfei Deng: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Jianjun Guo: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Min Zhang: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Zhenyuan Zi: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Jie Zhang: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Binyang Wu: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China

Energies, 2020, vol. 13, issue 4, 1-18

Abstract: The direct injection of natural gas (NG), which is an important research direction in the development of NG engines, has the potential to improve thermal efficiency and emissions. When NG engines operate in low-load conditions, combustion efficiency decreases and hydrocarbon (HC) emissions increase due to lean fuel mixtures and slow flame propagation speeds. The effect of two combustion modes (partially premixed compression ignition (PPCI) and high pressure direct injection (HPDI)) on combustion processes was investigated by CFD (Computational Fluid Dynamics), with a focus on different injection strategies. In the PPCI combustion mode, NG was injected early in the compression stroke and premixed with air, and then the pilot diesel was injected to cause ignition near the top dead center. This combustion mode produced a faster heat release rate, but the HC emissions were higher, and the combustion efficiency was lower. In the HPDI combustion mode, the diesel was injected first and ignited, and then the NG was injected into the flame. This combustion mode resulted in higher emissions of NO x and soot, with a diffusion combustion in the cylinder. HC emissions significantly decreased. Compared with PPCI combustion, HPDI had a higher thermal efficiency.

Keywords: direct injection of natural gas; injection strategy; partially premixed compression ignition (PPCI); high pressure direct injection (HPDI); combustion (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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