Effect of mixer type on cylinder-to-cylinder variation and performance in hydrogen-natural gas blend fuel engine

Compressed natural gas (CNG) buses were adopted in urban areas as a promising alternative to diesel buses, which emitted plenty of harmful emissions. Although CNG can meet the current emission standards, satisfying the requirements of the next EURO-VI emission regulation without an additional peripheral device may be impossible. The use of a hydrogen-compressed natural gas (HCNG) blend can help achieve a reduction in automotive exhaust emissions as well as prepare for an upcoming hydrogen economy through the construction of hydrogen infrastructure. Moreover, an HCNG engine has higher thermal efficiency than a CNG engine, producing lesser harmful emissions.Cylinder-to-cylinder variation affects multicylinder engine operation and can considerably influence an HCNG engine because fuel composition and excess air ratio differences can contribute to cylinder-to-cylinder variations. In the present study, the effect of the mixer type on cylinder-to-cylinder variation and performance characteristics were investigated using an 11-L heavy-duty CNG engine fuelled with HCNG (CNG 70 vol%, hydrogen 30 vol%). A change in the mixer type does not affect the characteristics of cylinder-to-cylinder variation and the combustion stability of the HCNG engine. The efficiency of cylinders 1 and 6 is lower than that of the other cylinders because of the configuration of the cylinder in the in-line-type engine. The significant increase in the pressure drop under a wide open-throttle operating condition makes it difficult to satisfy the engine's specifications.

► Change in gas mixer type does not affect cylinder-to-cylinder change of HCNG engine.
► This change also does not affect combustion stability of HCNG engine.
► THC and CO emissions of outermost cylinders higher than those of other cylinders.
► THC and CO emissions get oxidized with the remaining oxygen.
► Simplified mixer does not meet engine specification due to increase in pressure drop.