A Comparative Investigation of the Emission
Characteristics of Stoichiometric&nbsp;Combustion
and Lean-Combustion Methanol Engines

doi:10.3969/j.issn.1001-2222.2026.03.004

Vehicle Engine ›› 2026, Vol. 0 ›› Issue (3) : 23-28. DOI: 10.3969/j.issn.1001-2222.2026.03.004

A Comparative Investigation of the Emission Characteristics of Stoichiometric Combustion and Lean-Combustion Methanol Engines

SHI Laihua¹,KANG Jianjian¹,LI Lan¹,WU Di¹,LIU Bing¹,WANG Xin²

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Abstract

In a heavy-duty methanol engine developed to meet China-Ⅵ emission standards, stoichiometric-combustion and lean-combustion strategies were respectively applied to conduct cold-start and hot-start WHTC cycles. The raw exhaust emissions of regulated gaseous pollutants and particulate matter were measured. Results showed that, compared with stoichiometric-combustion, the lean-combustion strategy reduced methanol consumption by approximately 7%. Under both cold-start and hot-start conditions, lean-combustion operation benefits decreasing CO，CH₄，NO_x，NH₃, PM, and PN emissions from the heavy-duty methanol engine. However, lean-combustion operation led to higher unburned methanol and formaldehyde emissions during cold starts, and increased NMHC emissions during hot starts. With the lean-burn strategy, the raw PM and PN emissions of the heavy-duty methanol engine already met the China-Ⅵ limits, whereas NMHC and NO_x remained the primary compliance challenges. These issues can be addressed using an oxidation catalyst (OC) and a selective catalytic reduction (SCR) aftertreatment system, but particular attention should be paid to optimizing the control of unburned methanol and formaldehyde emissions at low exhaust temperatures.

Key words

internal combustion engine / methanol / stoichiometric-combustion / lean-combustion / emission

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SHI Laihua, KANG Jianjian, LI Lan, WU Di, LIU Bing, WANG Xin. A Comparative Investigation of the Emission Characteristics of Stoichiometric Combustion and Lean-Combustion Methanol Engines[J]. Vehicle Engine. 2026, 0(3): 23-28 https://doi.org/10.3969/j.issn.1001-2222.2026.03.004