What question did this study set out to answer?

This study aims to examine how varying the injection pressure of dissociated methanol gas affects engine performance and emissions during lean combustion.

June 6, 2026Open Access

Simulation Study on the Influence of Direct Injection Pressure on the Performance of Dissociated Methanol Gas on Lean Burn Methanol Engine

XMXianglong MengJilin University FXFangxi XieJilin University JDJiaquan DuanFirst Automotive Works (China)

Key Points

This study aims to examine how varying the injection pressure of dissociated methanol gas affects engine performance and emissions during lean combustion.
Simulation of different injection pressures of dissociated methanol gas in methanol engines under lean combustion conditions.
Analysis of jet penetration distance and emissions including NOx, CO, HC, CH3OH, and CH2O.
Investigation of changes in in-cylinder pressure and peak cylinder temperature with varying injection pressures.
Jet penetration distance decreases significantly with increasing injection pressures by 18.9 mm, 32.8 mm, and 37.4 mm at 0.3, 0.5, and 0.7 MPa respectively.
NOx emissions increase to a maximum and then decrease as injection pressure rises, while CO, HC, CH3OH, and CH2O emissions show an opposite trend.
At 1 MPa injection pressure, in-cylinder pressure and peak temperature reach their maximum values, while CO, HC, CH3OH, and CH2O emissions are minimized.

Abstract

Improving the thermal efficiency of engines and the application of alcohols are crucial for achieving carbon neutrality goals. This article investigates the effects of different dissociated methanol gas injection pressures on the performance of methanol engines under lean combustion conditions, aiming to improve combustion, performance, and emissions. It was found that the increase in environmental pressure would make the shape of the dissociated methanol gas jet more concentrated and shorten the jet penetration distance. When the time is 0.9 ms, the environmental pressure increases from 0.1 MPa to 0.3 MPs, 0.5 MPa, and 0.7 MPa, respectively. The jet penetration distance is shortened by 18.9 mm, 32.8 mm, and 37.4 mm, respectively. In addition, the increase in injection pressure will affect the development of mixture stratification and cause NOx emissions to first increase and then decrease. However, the CO, HC, CH3OH, and CH2O emissions showed the opposite trend. When the injection pressure exceeds 1 MPa, the direction of hydrogen stratification shifts from the x-axis to the y-axis. When the dissociated methanol gas injection pressure is 1 MPa, the in-cylinder pressure, peak cylinder temperature, and NOx emissions all reach their maximum values. The emissions of CO, HC, CH3OH, and CH2O are minimized.

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