Performance analysis and control of NOx emissions in diesel engine using on-board acetylene gas from calcium carbide

The rise in fuel prices and strict regulations on exhaust emissions on one side and depletion of fossil fuels on the other side has demanded the usage of fuel-efficient and clean combustion engines by using alternative fuel. The selection of the most suitable and reliable alternative fuel to suit the existing engine without modifications is an energizing task. The features like the wide operating range in compression ratios and air-fuel mixture ratio encourages diesel engines more compatible as compared to petrol engines. In the present work, Acetylene gas was selected due to excellent combustion properties, high flame velocity, and has higher chemical energy in it. In addition to that, the Acetylene is produced from CaC2 (calcium carbide) and is acquired from CaCO3 (limestone) which is vastly available in nature. Several researchers have done extensive research with acetylene gas as an alternative fuel on both petrol engines and diesel engines with many modifications in the existing engines. In most of the cases, the highpressure acetylene gas was used to improve power output, efficiency, and also to reduce exhaust emissions. The usage of C2H2 gas at higher pressure is not safe and backfiring is the most common phenomenon which influences the safety of operation. In the present investigation, the calcium carbide and water are mixed to produce the acetylene gas, and the same gas is mixed with air and this mixture will be as intake to the engine, and diesel is injected as usual. The acetylene gas at low pressure is used at various flow rates to explore the behavior of engine exhaust and efficiency and compare it with a pure diesel engine. The main focus is on brake thermal efficiency NOx emissions and the optimum flow rate of acetylene gas without a knock. With an optimum flow rate of acetylene, the brake thermal efficiency up to medium load is slightly reduced and at maximum load, it is very nearer to diesel fuel efficiency and even increased by 6.2%. The oxides of nitrogen emissions are escalated over the entire load range. The optimum EGR rate is investigated by considering the smoke, SFC, and temperature of the exhaust gases of the dual engines, and the same optimum EGR is applied to control NOx. The effects of hydrocarbons and carbon monoxide are not considerable. Hence, it is not covered in this study. (C) 2019 Elsevier Ltd. All rights reserved.