Experimental investigation of the effects of water adding to the intake air on engine performance and exhaust emissions in diesel engines

In the present study, the effects of water injection (WI) into intake air on the engine performance and exhaust emissions have been investigated in a Renault K9K 700 type turbocharged automotive diesel engine which has common-rail injection system. Experiments have been performed at different loads, engine speeds and various water ratios (WRs). The water has been injected into intake air by a carburetor, which main nozzle section is adjustable, at approximately 2%, 4 %, 6 %, 8 %, 10 % ratios.It was determined from the experimental results that the WI at specified ratios into intake air improves somewhat the engine performance and decreases significantly NOx and smoke index K. K smoke index decreases by increasing of WRs at (2000, 2500 and 3000) rpm. Its maximum reduction has been obtained as 41.75 % for 11.71 % WR at 3000 rpm. At chosen loads and engine speeds, as WRs increases, NOx emissions decrease. More effective reduction NOx has been obtained after 6 % WR. At 2500 rpm, at full load (520 N) and at 1/1 fuel deliver rate (FDR), maximum decrement of NOx emission has been obtained as 12.489 % for 9.400 % WR. As WR increases, brake specific fuel consumption (BSFC) takes values close to the neat diesel fuel (NDF) or decreases. BSFC decreases approximately 0.5 % for (4-6) % WR at 2500 rpm. Effective power takes values close to NDF. At 3000 rpm, at full load (460 N) and at 1/1 FDR maximum increment ratio has been obtained as approximately at the level of 1.173 % for 6.543% WR.Key Words: NOx emissions, Smoke index K, Engine characteristics, Injected water into intake air, Common-rail injection system