Effect of Methanol Energy Substitution Ratio on Performance of Methanol/Diesel Dual-Direct Injection Engine

In order to achieve higher thermal efficiency and lower emissions of methanol/diesel dual-fuel engines, an independent dual-direct injection system was built on a single-cylinder diesel engine and the operating range of the methanol/diesel dual-direct injection engine was conducted experimentally. Results show that the indicated thermal efficiency decreases with the increase of the methanol energy substitution ratio under low engine loads. But the increase of the methanol energy substitution ratio benefits the improvement of indicated thermal efficiency under medium and high engine loads. The highest indicated thermal efficiency of 43. 4% could be achieved at an engine load rate of 79. 5% and a methanol energy substitution ratio of 52. 4%. Meanwhile, with the increase of the methanol energy substitution ratio, NO* and soot emissions decrease, but the opposite trends of HC and CO emissions arc observed. Besides, the maximum methanol energy substitution ratio and its influence on the thermal efficiency of the engine were investigated under the full engine load and it was found that the maximum methanol energy substitution ratio of the dual-direct injection engine could reach up to 96. 0% and the indicated thermal efficiency first increases and then decreases with the increase of the methanol energy substitution ratio and reaches a peak when the ratio increases to 50. 0%. The research can provide experimental and data support for further optimization of the performance and emission characteristics of methanol/diesel dual-direct injection engines. © 2023 Xi'an Jiaotong University. All rights reserved.