Beneficial Use of Water Hammer in a Gasoline Direct Injection System

This paper reports on the study of an injection system for internal combustion engines that exploits a water hammer oscillating circuit as the high pressure pump. This concept has recently been developed by the authors and successfully used in a direct-injection two-stroke gasoline engine prototype. The fluid dynamic behavior is characterized by unsteady flow in high length/diameter ratio pipes and is dominated by water hammer and cavitation. A numerical code was developed to gain a better understanding of these complex phenomena and as an optimization tool. The flow in the piping was solved by means of a 1D model suitable to describe the cavitation and unsteady friction. An ad hoc experimental analysis was performed to demonstrate model consistency in simple test cases of cavitating and non-cavitating flows. The model was then used in a numerical code for the simulation of the whole water hammer injection plant.