Effect of hydrogen addition on performance, emission, and combustion characteristics of Deccan hemp oil and its methyl ester-fuelled CI engine

A vegetable oil-fueled diesel engine operation is characterized by low brake thermal efficiency and relatively high smoke emission. Conversion of vegetable oil to biodiesel results in slight improvement in efficiency and smoke emission, but the values are not comparable with diesel. In this work, a single-cylinder diesel engine's performance is evaluated by inducting hydrogen in small quantities in the intake manifold along with Deccan hemp oil (DHO) and its methyl ester (DHOME) as the pilot fuel. The tests were conducted at part-load and full-load conditions at an engine speed of 1500 rpm. Results indicate an increase in brake thermal efficiency from 29.7 to 32.6% and from 27.3 to 29.6% at full load with hydrogen-induced DHOME and DHO engine operation. Unburned-hydrocarbon emissions, carbon monoxide emission, and smoke emission reduced for both the fuels. However, NOx levels increased for the two fuels because hydrogen induction causes high combustion rates and high temperature in the combustion chamber. Hydrogen induction leads to high premixed combustion resulting in high peak pressures.