Research on innovative one-dimensional mathematical model applied to the on-line measurement for transient discharge coefficient of diesel injector nozzle

This paper presents an innovative one-dimensional mathematical model applied to the on-line measurement for transient discharge coefficient of diesel injector nozzle. The state change in the fuel system is abstracted into the transfer and evolution process of the Riemann wave, and a direct mathematical relationship between the pressure and the transient discharge coefficient in a single Riemann wave environment is established. The on-line calibration method of fuel sound velocity is proposed, which avoids the complicated off-line calibration of fuel physical property. The time-domain characteristics recognition method of input signal is put forward and the model is segmented according to time characteristics to improve the applicability. The decoupling algorithm of reflected wave and the correction method of interference wave are proposed to improve the model robustness. The experimental results show that this mathematical model has good accuracy. It is found that the variation of the average discharge coefficient with injection pressure and pulse width is nonlinear due to the cavitation and needle valve average opening.