A comparative study of combustion performance and emissions of dual-fuel engines fueled with natural gas/methanol and natural gas/gasoline

A comparative study on combustion characteristics and performance of a dual-fuel engine fueled with natural gas/methanol and natural gas/gasoline was conducted experimentally. All experiments were performed at an engine speed of 1600 r.rnin(-1) with a brake mean effective pressure of 0.387 MPa. Energy substitution ratio (ESR) was defined as the energy released by methanol or gasoline to the total energy released. Four ESRs namely 0, 19, 33, and 44 % were conducted in this study. The results demonstrated that both methanol and gasoline addition accelerated the burning rate of natural gas, leading to an increased peak cylinder pressure (P-max) and maximum heat release rate (HRRmax). The corresponding crank angle of P-max and HRRmax advanced and approached to top dean center after methanol or gasoline enrichment for the specific spark timing (theta(ig)) and ESR. In addition, as the ESR grew from 0 % to 44 % with a theta(ig) of 25 degrees CA BTDC, the brake thermal efficiency (BTE) increased from 27.3 % to 28.1 % for the natural gas/methanol mixture. In contrast, BTE reduced from 27.3 % to 25.5 % for the natural gas/gasoline mixture. The total hydrocarbon and carbon monoxide emissions of natural gas engines can be lowered by adding methanol and raised by inputting gasoline. (C) 2021 Elsevier Ltd. All rights reserved.