Combustion stability, RGF and pressure referencing effect on HRR for a high compression ratio SI engine with natural gas lean mixtures

• Published in: Case studies in thermal engineering 2024-01, Vol.53, p.103891, Article 103891
• Main Authors: Mesa, Edisson S. Castaño, Quintana, Sebastian H., Bedoya, Iván D.
• Format: Article
• Language: English
• Subjects: Heat release rate; High compression ratio; Knocking; Natural gas; Residual gas; Spark ignition
• ISSN: 2214-157X; 2214-157X
• DOI: 10.1016/j.csite.2023.103891

The knocking and heat release based on cylinder pressure trace is a widespread practice in combustion diagnostic for conventional SI engines. The accuracy depends on quality of measured in-cylinder pressure, thermodynamic models and parameters feeding such models. In non-conventional engine, common models to assess engine operation, do not satisfy properly expected standard, thus application of new methods and models is required. This study presents the determination of knocking intensity by in-cylinder pressure and cycle-to-cycle variability for operation analysis, the effect of referencing pressure and residual gas fraction on heat release for non-conventional SI engines with high compression ratio with natural gas at partial loads and lean mixture. Higher spark timings was achieved at 21 degrees, limited by low occurrence audible knock for KI20 over 0.04 bar. Compression ratio 15.5, engine speed at 1800 rpm, air-cooled system, and equivalence ratio of 0.73 make limited the operation. KI20 of 0.072 was reached at IMEP 3.96 bar and spark timing of 21 degrees. Maximum CoV of KI20 was 27.1. Pressure referencing shows low differences in polytropic coefficients of 1.34. Slight difference for RGF generates differences in the mass burned up to 12%, and around 0.4 degrees in combustion duration.