Abstract
In this study, the four kinetic reaction mechanisms were developed to simulate the formation of pollutant species in CNG fired IC engine. The reactions were generated using EXGAS and coupled with Leed’s NOx reactions to develop four kinetic mechanisms. These reaction mechanisms described the combustion of natural gas at low (below 800 K) to high (above 1000 K) temperature in combustion chamber. The simulation studies predicted that the maximum cylinder pressure was achieved up to 18.0 atm & 40.0 atm under fuel leaner conditions (φ ≈0.6) and fuel rich conditions (φ=1.13 to 1.3) respectively. The simulation based data was compared with the experimental data (when engine was operated at 3000 rpm, φ=1.0, Pinlet=0.67 atm). For fuel rich conditions, high concentrations of CO were observed while NOx levels were lowered while the fuel leaner mixture produced the lower CO emissions and moderate levels of NOx emissions. The NOx and CO profiles depicted that Mechanism-I, Mechanism-II and Mechanism III seemed to be inappropriate for predicting the emissions in due to CNG combustion IC engine. The molded data for Mechanism-IV exhibited closer agreement with experimental measurements. The rate of production analysis identified the important reactions in each mechanism which were contributing in the formation of emission concentrations of pollutant species. Although each proposed mechanism illustrated some discrepancies among the profiles, Mechanism-IV (consisting of 208 reactions and 78 species) showed good agreement with experimental data for pressure, temperature and pollutant species profiles.
Highlights
Combustion is a key process of converting chemical energy to heat which is converted to mechanical energy to derive in IC engine
This comparison provided the baseline information for the selection of an appropriate kinetic model of oxidation of natural gas in IC engine
The modeled data was compared with the experimental data
Summary
Combustion is a key process of converting chemical energy to heat which is converted to mechanical energy to derive in IC engine. Due this combustion, pressure and temperature suddenly rise within the engine chamber which provides the driving force to push the piston back to produce the motion in the automobile [1]. The authors concluded that the direct injection of CNG has shown better results in the thermal efficiencies comparable to those attained by high compression ratio. Lean burning of CNG in SI engines has the potential to improve thermal efficiency and reduce emissions compared with the burning of gasoline. An in-depth understanding of the physical and chemical processes is required to speed up the greener engine designs
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