The Effect Of Different Compression Ratios In HCNG Operating SI-Engines And Comparison To Simulated Results

The thermal efficiency is one of the most important values for combustion processevaluation. Due to the fact that many car manufacturers tend to focus in modern engineson high fuel economy the importance of this value increases. Three main factors can beidentified to improve thermal efficiency: Compression ratio, air fuel ratio andcombustion duration.This research work investigates the influence of variable compression ratioregarding the combustion behavior and emissions for a HCNG fueled engine for varyinghydrogen concentrations (20%,55%,75%). For the experimental tests animplementation of cylinder heads with different height has been conducted for therespective compression ratios (10,11,12). Based on the recorded pressure developmentthe thermal efficiency and the mass fraction burned can be obtained. Depending on theignition timing cycles, which achieve the highest thermal efficiency, will be analyzed indetail. In the final step a quasi-dimensional model will be used to simulate these cycles.Therefore the experimental pressure data will be set as reference and compared tosimulated results. The main target for the simulation is to determine calibration factorsfor the quasi dimensional model. In order to produce comparable, consistent andaccurate results the limiting value for the relative error for the maximum pressurebetween simulations and experiments was set to1%.