Hydrogen And Hydrogenous Mixture Fuelled Engine Combustion And Emission Characteristics Study

Hydrogen is clean and reproducible fuel with high thermal efficiency. Using hydrogen as fuel of internal combustion engine is very meaningful and critical for the alternative fuel development. In this paper, the simulation and experimental studies of hydrogen and H2/CH4 mixture fuelled engine have been carried out.For simulation study, a three-dimensional numerical simulation model is built for hydrogen and H2/CH4 mixture fuelled engine by CFD software STAR-CD, which includes complex chemical combustion module, turbulent flow module and heat transfer module etc. Based on the simulation model, cylinder pressure, cylinder temperature, fuel combustion rate, heat release rate, species concentration versus crank angle have been studied to get engine combustion and emission characteristics. The effects of the excess air ratio, ignition timing, initial intake temperature, initial intake pressure, fuel blend proportion as well as oxygen concentration have been researched to give guidance to the optimization of engine. Based on the simulation work, hydrogen engine experiment study has been carried out. The characteristics of hydrogen engine found in simulation study are validated by experimental results.The study results are summarized below:(1) With the increase of excess air ratio, the incremental rates of cylinder pressure and temperature decrease. Cylinder peak pressure and peak temperature decrease, and NO emission can be significantly reduced. Lean combustion of hydrogen can realize stable and clean combustion.(2) With the increase of ignition timing advance, the reaction progress of H2/O2 mixture will advance parallelly which causes higher mean temperature and higher NO emission in the cylinder.(3) With the same quantity of fuel injected into every cycle, lower initial intake temperature or higher initial intake pressure can make more fresh air enter the cylinder and H2/O2 mixture becomes lean. This slows down the combustion speed and makes the mean temperature lower which leads to lower NO emission.(4) H2/CH4 mixture fuelled engine study found that methane addition decreases the reaction speed of the mixture. With more methane in the mixture, the incremental rates of pressure and temperature inside the cylinder decrease. NO emission decreases due to the lower combustion temperature. Meanwhile, CO2 emissions increase. Blend proportion optimization is crucial to the optimization of H2/CH4 engine.(5) The decrease of oxygen concentration can slow down the combustion speed of H2/CH4 mixture and the incremental rates of temperature in the cylinder which can reduce the NO emission. But the carbon oxidant emission will increase due to the uncompleted combustion. The oxygen concentration should been carefully chosen for high combustion efficiency and lower emission of engine.