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.
Effects of gas composition on the performance and emissions of compressed natural gas engines
Natural gas is considered to be a promising alternative fuel for passenger cars, truck transportation and stationary engines providing positive effects both on the environment and energy security. However, since the composition of natural gas fuel varies with location, climate and other factors, it is anticipated that such changes in fuel properties will affect emission characteristics and performance of CNG (Compressed Natural Gas) engines. The purpose of the present study is to investigate the effects of the difference in gas composition on the engine performance and emission characteristics, The results show that THC (Total Hydrocarbon) decreases with increasing WI (Wobbe Index) and MCP (Maximum Combustion Potential). On the other hand, it is observed that NOx slightly increases as WI and MCP increase. The TLHV (Total Lower Heating Value of Intake) is proposed in this study as a potential index for compatibility of gas fuels in a CNG engine. There is a variation in power up to 20% depending on the composition of gas when the A/F ratio and spark timing are fixed for a specific gas fuel.
Computational fluid dynamics as a development tool for rotary blood pumps.
Computational fluid dynamics (CFD) is beginning to significantly impact the development of biomedical devices, in particular rotary cardiac assist devices. The University of Pittsburgh's McGowan Center for Artificial Organ Development has extensively used CFD as the primary tool to analyze and design a novel axial flow blood pump having a magnetically suspended rotor. The blood-contacting surfaces of the pump were developed using a design strategy based on CFD that involved closely coupling a Navier-Stokes solver to a parameterized geometry modeler and advanced mesh movement techniques. CFD-based blood damage models for shear-induced hemolysis as well as surrogate functions describing thrombosis potential were employed to help guide design improvements. This CFD-based design approach resulted in the timely development of a pump subjected to multiple geometric refinements without building expensive physical prototypes for each design iteration. A physical prototype of the final improved pump was fabricated and experimentally analyzed using particle imaging flow visualization. The CFD predicted results correlated well with the experimental data including pressure-flow (H-Q) performance and specific flow field features. It is estimated that the present CFD-based design approach shortened the overall design time frame from an order of years to months.