Optimization of Gasoline to CNG Engine Conversion using Computer aided Engine Simulation
Among all the alternative fuels available in the market, CNG has so far proved to be the most promising. However, most of its use is limited to retrofitted engines, which has lead to improper utilization of CNG as a spark ignition fuel. This study focuses on efficient utilization of the high calorific value and other desirable properties of CNG by making slight design and operational changes. Performance of engine is studied using a computer aided engine simulation model that evaluates the performance of engine in a virtual working environment. Effect of various parameters on the engine operation is also studied and the valuable data collected in the process is used to alter the operational and design parameters of the engine. In this way engine is tuned for optimum utilization of CNG and its performance is enhanced as compared to the conventional CNG conversion kits.
Study of CNG Combustion Under Internal Combustion Engines Conditions Part I : Using Quasi-Dimensional Modelling
An in-house quasi-dimensional code has been developed which simulate the overlap, intake, compression, combustion, as well as expansion and exhaust processes of a homogeneous charged internal combustion engine (ICE). A detailed chemical kinetic mechanism, constituting of 39 species and 148 elementary reactions, has been used in conjunction with above code to study the combustion of CNG under IC engine conditions. Two different criteria, based on pressure rise and mass of fuel burned, are used to detect the onset of ignition. Parametric studies are conducted to show the effect of compression ratio, initial pressure, intake temperature and equivalence ratio, on the time of ignition and fuel burning rate. The results obtained from the modelling show a good agreement with the experimental data.
Unsteady Heat Transfer During the Rapid Compression and Expansion of Air
The instantaneous unsteady heat transfer during rapid compression and expansion of air within a pneumatically driven piston in a cylinder arrangement which offers simple, well-controlled and known boundary conditions was examined. Values of the instantaneous apparent overall heat flux from the cylinder gas to the wall surfaces were calculated using a thermodynamic analysis of the experimentally measured pressure and volume temporal development. Corresponding heat flux values were also calculated through the application of a zero-dimensional model that incorporates the use of the k–e turbulence model. Comparison of the results of the model with corresponding experimental data showed fair to good agreement for the wide range of compression ratio values used (8.4∼24.3). Also, correlation of the derived data using an effective velocity which is based on the distribution of mean kinetic energy, turbulence energy and piston motion and a characteristic length that is a function of the instantaneous height between the piston top and the cylinder head and bore diameter as the parameters to use when calculating the Reynolds, Prandtl and Nusselt numbers resulted in the following workable relationship: Nu = 0.01Re0.205 Pr0.033 .Copyright © 2002 by ASME