Abstract
Vegetable oils are receiving a lot of attraction as alternative engine fuels as they are renewable. Their direct use will enable decentralized power generation with local resources in rural areas. High viscosity of vegetable oils, results in poor vaporization, and hence decreases the performance and increases the emissions of a diesel engine. This problem can be tackled by injecting a gaseous fuel (LPG) in the intake manifold by using an electronically controlled gas injector in dual fuel mode. Rubber seed oil from rubber tree is considered to be suitable alternative fuel, which is used as primary fuel. LPG is considered as a viable fuel and it is used as secondary fuel. In this work the dual fuel method was investigated to ascertain its suitability to reduce the smoke emission from a neat rubber seed oil fuelled diesel engine. A single cylinder diesel engine with a rated output of 4.4 kW at 1500 rpm was converted to operate in the dual fuel mode. Tests were conducted with different amounts of LPG and rubber seed oil being supplied to the engine. LPG supply was varied from zero to the maximum value that the engine could tolerate. The engine output was also kept at different constant levels of 25, 50, 75 and 100% of full load. Experimental results indicated a small improvement in the thermal efficiency at 75% and 100% loads. At all loads the smoke level was drastically decreased. CO and HC levels are reduced at high outputs. Heat release rate indicates an increase in the combustion rate with LPG induction. On the whole it is concluded that LPG can be inducted along with air in order to reduce smoke levels and improve thermal efficiency of vegetable oil fuelled diesel engines.
KEYWORDS: Rubber seed oil; LPG; diesel engine; gas injection; performance; emission and combustion