Analysis of spray evolution from both piezo and solenoid injectors in single cylinder research engine

The continuous requests for the improvement of performance and the fulfilment of strict emission legislation have required the use of advanced technologies in modern diesel engines. A primary role has been played by the injection system development. Two main technologies have been used so far for the control of the needle lift: the solenoid driven injectors and the piezoelectric injectors. For the first, the movement is due to a magnetic field induced by a current circulating in a coil; for the latter, it is a piezoelectric material that elongates when a voltage signal is applied between its opposite surfaces. Investigations on the injection process by using solenoid and piezo injectors have been the objective of this paper. The experiments have been carried out in a single cylinder transparent engine operating in premixed mode. The head of a Euro 5 production engine has been mounted on an elongated cylinder and the production Common Rail injection system has been used. A sapphire window has been set in the piston head in order to observe the phenomena occurring in the combustion chamber. Engine has been fed with commercial diesel fuel. High speed camera has been used for the acquisition of spray evolution images. Information about the behaviour of the two injector types has been obtained. It has been observed that the two injector technologies show a different behaviour in terms of spray distribution in the combustion chamber. It has been found that piezoelectric injectors offer the advantage of a shorter injection delay than the traditional solenoid ones.