Potential Issues and Optimization Solutions for High-Compression-Ratio Utilization in Hybrid-Dedicated Gasoline Engines

Qiuyu Liu, Baitan Ma, Zhiqiang Zhang, Chunyun Fu and Zhe Kang ()
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Qiuyu Liu: State Key Laboratory of Mechanical Transmission for Advanced Equipment, Chongqing University, Chongqing 400044, China
Baitan Ma: Dongfeng Liuzhou Motor Compoany Limited, Liuzhou 545005, China
Zhiqiang Zhang: Dongfeng Liuzhou Motor Compoany Limited, Liuzhou 545005, China
Chunyun Fu: State Key Laboratory of Mechanical Transmission for Advanced Equipment, Chongqing University, Chongqing 400044, China
Zhe Kang: State Key Laboratory of Mechanical Transmission for Advanced Equipment, Chongqing University, Chongqing 400044, China

Energies, 2025, vol. 18, issue 15, 1-22

Abstract: This systematic review critically examines the benefits and challenges of high-compression-ratio (CR) implementation in hybrid-dedicated engines, recognizing CR increase as a pivotal strategy for enhancing the indicated thermal efficiency to achieve carbon peak and carbon neutrality goals. However, excessively high CRs face critical constraints, including intensified knock propensity, increased heat transfer (HTR) losses, reduced combustion stability, augmented dissociation losses, and cold-start misfire risks. The feasibility and necessity of CR enhancement in hybrid systems were comprehensively evaluated based on these factors, with fundamental mechanisms of the detrimental effects elucidated. To address these challenges, optimized countermeasures were synthesized: knock suppression via high-octane fuels, EGR technology, lean combustion, and in-cylinder water injection; heat transfer reduction through thermal barrier coatings and independent CR/expansion-ratio control; misfire risk monitoring using ion current or cylinder pressure sensors. These approaches provide viable pathways to overcome high-CR limitations and optimize engine performance. Nevertheless, current research remains confined to isolated solutions, warranting future focus on integrated optimization mechanisms investigating synergistic interactions of multiple strategies under high-CR conditions.

Keywords: hybrid engine; high compression ratio; indicated thermal efficiency; knock control; heat transfer losses; optimization strategy (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: 2025
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