Mixer Design for A High Performance Biogas Si Engine Converted from An Diesel Engine

Abstract

The performance and pollution emission of biogas engines strongly depend on the fuel-air equivalence ratio of the mixture. Thus an appropriate design of the mixer is the main issue in converting an existing diesel engine into a biogas spark ignition engine. This paper presents some results of simulation and experiment research on a venturi type mixer for a biogas SI engine converted from a ZH1115 diesel engine. The results show that the fuel-air equivalence ratio of the mixture is less dependent on the opening of the butterfly valve which controls the mixture but it sharply depends on CH4 concentration in the biogas and/or on section of the biogas supplying pipe. At full load, the fuel-air equivalence ratio is slightly changed in relation to the engine speed but at partial load, it strongly depends on the engine speed, particularly at low regime. The dimensionless diameter of the biogas supplying pipe can be expressed by a power relationship with CH4 concentration in biogas with an exponent of -0.515.