The effects of water injection inside an internal combustion engine regarding NO_x emissions

Abstract In this paper we present the influence of water injection on NOx emissions and the performance of a gasoline engine subjected under light to medium loads. The test bench used for measurements has a 4-cylinder, 1.6-liter engine and operates with a wasted spark configuration. Water is injected upstream of the throttle valve through a single injector mounted in the intake runner. The injection timing and amount of water injected inside the engine have been controlled by NI CompactRIO hardware device by the aid of an in-house algorithm implemented in LabView. Water is injected twice at each rotation of the crankshaft in order to have water in all cylinders. The injection of water is done at a fix angle, one time at 0°CA and the other at 360°CA, only the amount is varied from 10% to 45% of the total fuel fraction injected. The results showed that at an amount of water of about 25% of the total fraction of fuel injected, it produced a considerable decrease in NOx emissions, while keeping engine performance unchanged.