Investigation of combustion, performance and emission studies of HCCI engine operated with carbon free fuels

Abstract Increasing risk to the climate change on earth, it is essential to use carbon free and clean fuel routes to decrease greenhouse gas emissions and control the pollutant emissions from combustion process. Hydrogen (H 2 ) and ammonia (NH 3 ) are the substitute attractive fuels for carbon free combustion processes to meet the various energy applications. In present investigation the influence of NH 3 /H 2 fuel blends is analysed on combustion and emissions parameters of Homogeneous charge compression ignition (HCCI) engine for various equivalence ratios (ϕ = 0.3,0.5,0.8) and for various Ammonia hydrogen ratios (63%H 2 , 73%H 2 and 83%H 2 ) using thermodynamically by using CHEMKIN tool. It is also evident that auto-ignition temperature of ammonia is very high and low flame speed which resist the combustion in engine. Whereas hydrogen fuel has wide flammability limits and high flame speed appropriate blending of ammonia and hydrogen is required to promote and stabilize the HCCI combustion. For all the equivalence ratios and H 2 /Ammonia blends peak in-cylinder pressure and in-cylinder temperature increases as expected which plays a significant effect on overall combustion of engine. Blending a certain amount of hydrogen into the engine can significantly improve the requirements of the ammonia in engine’s inlet gas temperature and compression ratio. It has been observed that higher peak in-cylinder temperature and temperature for higher hydrogen ratio in blends which results in advance fuel mixture ignition and witnessed the improve performance and combustion characteristics of engine. The peak molar fraction of NO produced in the cylinder increases as the hydrogen doping ratio increases. Also, the effect of various intake fuel gas temperature for 73%H 2 with equivalence ratio of 0.8 is also studied. It is observed that 448 K fuel composition is favourable in present range of study. Further, with varying gas inlet pressure for temperature 448 K and 73%H 2 with 0.8 equivalence ratio combustion is delayed. Since no evident of CO 2 in air fuel mixture, so no carbon traces are observed. The obtain result validated with existing literature data.