Estimating the Effect of Compression Ratio on Power, Knock, and Emissions of a CNG Engine Converted from a Diesel Engine
Received: 4 February 2025 | Revised: 20 March 2025 and 24 March 2025 | Accepted: 28 March 2025 | Online: 4 June 2025
Corresponding author: Khuong Thi Ha
Abstract
This study examines the effect of compression ratio variation on the performance, fuel efficiency, and emissions of a single-cylinder diesel engine converted to operate on Compressed Natural Gas (CNG) using the AVL-Boost simulation software. The compression ratio was varied from 10 to 15 to evaluate key engine parameters. The results show that increasing the compression ratio improves thermal efficiency from 37.5% to 41%, enhances engine power from 13.2 kW to 14.3 kW, and increases torque from 58 Nm to 61.5 Nm. Additionally, specific fuel consumption decreases by approximately 6%, while CO and NOx emissions are reduced by 0.15% and 134 ppm respectively. However, higher compression ratios also increase the required octane number, potentially inducing knock beyond a ratio of 15. An optimal compression ratio of 15 is identified, balancing improved performance, fuel efficiency, and emission control without exceeding knock limits. These findings provide valuable insights for the design of high-efficiency, low-emission CNG engines.
Keywords:
compression ratio, CNG, diesel engine conversion, thermal efficiency, emissionsDownloads
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Copyright (c) 2025 Nguyen Thanh Vinh, Chu Duc Hung, Doan Cong Thanh, Nguyen Xuan Khoa, Khuong Thi Ha
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