Investigation of the effects of water adding to the intake air on the engine performance and exhaust emissions

In the presented study, the effects of water addition to intake air (WAIA) in gasoline engines on engine performance and exhaust emissions were investigated both experimentally and numerically. In the experimental study, WAIA was performed to a modern automobile engine (Renault Clio) at four different engine speeds and four different water ratios (3%, 6%, 9%, and 12%). For each engine speed, six different loading conditions were selected. In the numerical study, WAIA was investigated in a modern automobile engine (Renault Megane) at three different water ratios (5%, 10%, and 15%) and six different engine speeds. In the numerical study, a dimensionless, thermodynamics-based two-zone cycle model was adapted and used for water usage. At the end of the experimental study, it was determined that the brake specific fuel consumption (BSFC) decreased under all selected operating conditions except at 6000 rpm with WAIA. The maximum reduction rates in SFC at engine speeds of 3000, 4000, and 5000 rpm were 28.27% at 5.60% water ratio, 4.16% at 2.67% water ratio, and 7.19% at 9.0% water ratio, respectively. It was determined that NOx and HC emissions were generally decreased under all selected operating conditions with WAI. With EHSE; although CO decreased at 3000 rpm, CO increased at 4000 rpm, there was no significant change in CO at 5000 rpm and it generally increased at 6000 rpm. As a result of the experimental study, it was determined that approximately 9% water ratio was the optimal level in terms of both engine characteristics and exhaust emissions. At the end of the numerical study, it was found that the BSFC and YNO the values of mole fraction ratio increased, and the combustion temperatures, cylinder pressures, and, CO emission values decreased at the selected water ratios.