| The accurate calculation of the heat loss from bulk gas to engine coolant is critical for the optimization of the engine cooling system, calculation of the heat release rate, and improvement of the engine efficiency. The heat transfer coefficient of the traditional diesel and gasoline engines has been well documented. However, the research specific for the heat loss of spark ignition (SI) engine operating on gaseous fuels is limited.;This research developed a revised Woschni equation scaling factor for a Weichai turbocharged SI WP-10 engine operated on gaseous fuels. The engine was a 6 cylinder, 9.7 Liter stoichiometric engine developed to operate on gaseous fuels. The specific heat ratio was derived by calculating the specific heat of bulk gas which was a function of bulk gas mixture composition, and temperature. The scaling factors of the heat transfer coefficient was developed based on the hypothesis that the heat release rate was zero prior to the beginning and after the completion of combustion. When operated at full load, the scaling factors of the heat transfer coefficient for this engine was 0.34, 0.33, and 0.32 when operated on natural gas, natural gas & carbon dioxide, and natural gas & propane, respectively. Utilizing the revised Woschni equation, the heat release rate was calculated for each fuel. The effect of fuel composition and spark timing on cylinder pressure, heat release rate, mass fraction burned, combustion duration, and heat loss was analyzed. As expected, the blending of carbon dioxide to natural gas elongated the ignition delay, retarded the combustion phasing, and elongated the combustion duration. In comparison, the blending of propane accelerated the combustion process as indicated by the shorter combustion duration and ignition delay, and also the increased peak cylinder pressure. The effect of the fuel composition on the exhaust emissions before and after the three-way catalyst was also examined and presented. |
