Effect of CNG flow rate on the performance and emissions of a Mullite-coated diesel engine under dual-fuel mode

Abstract

On the diesel engines that are used to generate power in transportation and industries, many researchers have to deal with major problems of smoke emissions while extracting higher efficiency. There are many studies which reported the exhaust emission reduction strategies from diesel engines by applying new combustion methods that are capable of mitigating the formation of harmful emissions. One of the methods to reduce the exhaust emissions in diesel engines is to use the dual-fuel combustion mode. In this study, an attempt has been made to evaluate the effect of thermal barrier coating (TBC) on the dual-fuel engine and for this, experiments are carried out on a single-cylinder direct-injection diesel engine under dual-fuel and low heat rejection mode with compressed natural gas (CNG) as gaseous fuel. Engine components that are exposed to the combustion are coated with Mullite (3Al2O3-2SiO2) TBC. Diesel at 200 bar injector opening pressure was used as pilot fuel and CNG at different flow rates (5, 10 and 15 litres per minute) was inducted into the combustion chamber through inlet manifold as main fuel. Experimental results show that the coating of TBC on the engine components has a positive effect on the performance emissions of the dual-fuel test engine. Brake specific fuel consumption (BSFC) was found improved significantly at all flow rates of CNG with coated engine. Emissions on the other hand were also noticed to be on the lower side with the coated engine except NOx. Smoke emissions were significantly reduced with coated CNG operation of the test engine at all flow rates.