| HCNG fuel is short for hydrogen enriched compressed natural gas, which isconsidered a promising alternative fuel for vehicles. Previous research indicates that thebest hydrogen fraction in the mixture that balances the power output and the emission isaround20%. This paper focus on the performance and emission characteristics of20%HCNG engine, experimental test and simulation are utilized during the research.Numerical simulation includes two parts: calibration of quasi-dimensionalsimulation and combustion analysis based on KIVA-3V program. A two zoneentrainment combustion model for pure hydrogen engine was built based on the originalHCNG model, and then three coefficients of quasi dimensional model were calibratedcarefully with a wide range of operating conditions and various fractions of hydrogenadded to natural gas. The model was calibrated by the experiment and predicted thecombustion pressure of20%HCNG under different compression ratios. In the KIVAprogram work, computational grid of the combustion chamber was built at first,turbulence model and combustion model were selected, and the initial conditions andboundary conditions were defined. The multi-dimensional model was validated by theexperimental result and the average pressureã€velocity vectorã€temperatureã€COemission and NOx emission during the combustion chamber were discussedpreliminarily.Experimental tests were carried out under different compression ratios:10,11and12. The influence of compression ratio on the20%HCNG engine was investigatedunder different ignition timings and excess air ratios. The results show that highercompression ratio can improve the thermal efficiency, increase the power output andreduce the fuel consumption. Higher compression ratio also does good to the cycle bycycle variation and heat release, however, it is harmful for the NOx exhaust emission.Appropriate lean burn can improve the efficiency further and reduce the NOx emissioneffectively. |
PDF Full Text Request