Experimental assessment on the performance, emission and combustion characteristics of a safflower oil fueled CI engine with hydrogen gas enrichment

Abstract

Inducting hydrogen with biodiesel in a compression ignition (CI) engine contributes to improvising the performance characteristics of the engine and minimize long-term issues. Combustion of hydrogen along with intake air impacts positively in air quality by preventing the formation of toxic emissions like hydrocarbons (HC) and carbon monoxide (CO). The benefits of hydrogen such as good diffusion rate, lesser ignition energy and fast flame propagation rate promotes a more homogenously mixed air fuel ratio. This experimental work focuses on enhancement of the performance and combustion characteristics of a direct injection compression ignition (DICI) engine by enriching the biodiesel with various levels of hydrogen gas supplement at the intake manifold. The brake thermal efficiency of the engine with safflower oil biodiesel is 31.15 % which is far inferior to that of diesel with 34 %. As an effort to improve the performance characteristics of the CI engine, hydrogen gas is inducted at 4 %, 8 % and 12 % energy share. HC, CO and smoke emission decreases by 15.09 %, 34.6 % and 18 % respectively compared to neat biodiesel at full load of 5.2 kW. An opposite trend is observed in NOx emissions which are raised from 1650 ppm to 1852 ppm. A 12.2 % increase in NOx emissions are realized due to homogenous flammable mixture that combusts closer to Top dead center (TDC). The hydrogen enrichment with safflower oil biodiesel influences the combustion characteristics in a positive vein except for the NOx emissions, which could be minimized through the use of retrofit devices like selective catalytic reducer, diesel oxidation catalyst etc.