Abstract:

An inlet injection system of methanol was built in a six cylinder diesel engine to investigate the
combustion and emission characteristics at different substitution rates under the condition of diesel/methanol
compound. The test results show that the combustion characteristics of the engine has changed with the
methanol compound combustion. With the methanol replacement rate increases, the premixed combustion ratio
increases and the diffusion combustion ratio decreases. With the methanol compound combustion, the overall
combustion duration shortened, heat is more focused and improve the combustion content. The methanol
compound combustion can also recover a part of heat from the cooling system, together with the joint effect of
the heat efficiency is greatly improved. However, the high methanol replacement rate will bring the deterioration
of the NOx and CO emissions with the methanol and formaldehyde emissions. The methanol compound
combustion will also delay the cylinder starts burning time, it is have to adjust the main injection timing to ensure
the stable operation of the engine.

Key words: diesel/methanol compound combustion, premixed combustion, emissions, combustion analysis, thermal efficiency