Numerical Simulation Of Ammonia Fuel Combustion Process

The rapid development of the automotive industry has brought convenience to people,but also brought about huge environmental pollution,resulting in the rapid consumption of fossil energy.Ammonia is considered to be one of the ideal green fuels that can be used in engines because of its high calorific value,high octane number,cheap availability,and complete combustion that produces only water and nitrogen without contamination.In this paper,the single-zone homogeneous compression ignition module in CHEMKIN,a large-scale gas-phase kinetics software,is coupled with the combustion reaction mechanism of ammonia to study the combustion and emission of ammonia fuel with different intake air temperature,inlet pressure,mixture concentration,rotation speed and compression ratio.According to the combustion performance,the improvement measures of adding pilot fuels are proposed.The effects of different hydrogenation ratios on the ignition timing and emission characteristics of the ammonia/hydrogen mixture fuel are analyzed.The minimum compression ratio required and intake air temperature for fuel combustion under different hydrogenation ratios is sought.The results show that:(1)The intake air temperature and the compression ratio have a great influence on the ignition time and cylinder pressure of the ammonia fuel,but have little influence on the cylinder temperature;the inlet pressure has little effect on the ignition time of the fuel and the peak temperature in the cylinder,but it has a significant effect on the peak pressure in the cylinder.The range of ammonia fuel compression ignition is relatively wide.When the equivalence ratio is 0.4,the combustion can be carried out,which means that the ammonia fuel can achieve compression ignition under lean conditions;the rotational speed has little effect on the temperature and pressure of the internal combustion engine’s cylinder.(2)The percentage of hydrogen added to the blended fuel increases from 5% to 30%,the minimum intake air temperature required to achieve compression ignition of the blended fuel decreases from 550 K to 340 K,and the minimum compression ratio required to achieve compression ignition decreases from 28 to 11.It can be seen that incorporating hydrogen as a pilot fuel in ammonia fuel can significantly reduce the intake air temperature and the compression ratio of the internal combustion engine.(3)Under normal pressure conditions,the compression ratio is set to 18,the intake air temperature is 350 K,the ammonia fuel is ignited,and the hydrogen content of the mixed fuel is around 25%.