Mechanical Engineering, Sahand University of Technology
It is a well known fact that, dual fuel engines at part loads, inevitably suffer lower thermal efficiency, higher carbon monoxide and unburned fuel emission. The work in this paper is to investigate combustion characteristics of a dual fuel (diesel-gas) engine at part loads, using a single zone combustion model with detailed chemical kinetics for combustion of natural gas fuel. The authors developed software in which the pilot fuel is considered as a subsidiary zone, and a heat source which is derived from two superposed Wiebe’s combustion functions is to account for its contribution to ignite gaseous fuel and the remainder of total released energy. Chemical kinetics mechanism consists of 112 reactions with 34 species. This quasi-two zone combustion model is able to establish the development of the combustion process with time, and the associated important operating parameters such as; pressure, temperature, heat release rate (H.R.R) and species concentration. Therefore this work is an attempt to investigate the combustion phenomenon at part loads, using techniques such as increasing the quantity of pilot fuel and exhaust gas recirculation (EGR) to solve the above mentioned problems. By employing these techniques, it is found that, both these methods have positive effect on the performance and emission parameters, except for NOx of dual fuel engines at part loads. Predicted values show good agreement with corresponding experimental values in a special engine with operating condition of (1/4 load, 1400 rpm). Implications will be discussed in details.