Abstract: The bulk elastic modulus of the air and liquid mixing fluid is the inherent physical property, and it has direct effects on the accuracy, rapidity and stability of fluid driving. An accurate model to calculate the bulk elastic modulus is the basis for the design and optimization of the fluid machinery, and it is of great value to the theory and engineering. By analysing the evolution process of the cavitation in the fluid and Henry's law, a quintic polynomial is proposed to fit the theoretical relationship air content and pressure, and then a theoretical model (Model1) to calculate the bulk elastic modulus of the air and liquid mixing fluid is obtained. Compared with the experimental date, the results of different models are analysed and the effects of the pressure and air content on the fluid bulk elastic modulus are revealed. The investigation shows that Wylie and Nykanen models have a little difference under isothermal conditions, and the bulk elastic modulus of both are approximate within the full pressure range; the values of Ruan model are larger within high pressure range and close to the values of Wylie model within low pressure range; the values of Model1 is the closest model to the experimental data, and it provides a more accurate method to predict the bulk elastic modulus of the fluid within law pressure range, in which the liquid phase will turn into gas phase. The investigation will provide the reference to a better prediction of the bulk elastic modulus of the air and liquid mixing fluid.

Key words: air and liquid mixing fluid, bulk elastic modulus, cavitation, saturated vapor pressure, theoretical model