Determination of the Constants of the Equation of State for Calculating the Elastic Properties of Various Engine Fuels and Technical Fluids

The creation of modern mathematical models of unsteady high-pressure fuel injection in engines requires the replacement of universal empirical equations for one of the elastic properties of fuel by a mathematically more correct equation of state. The necessity of the existence and use of convenient and simple forms of the equation of state, allowing the values of density, compressibility factor and sound velocity of traditional and alternative fuels for diesel engines to be determined quickly and with sufficient accuracy, has been substantiated. Modern approaches to the description of the state of droplet and two-phase liquids are analyzed. The absence of phase transitions in the process of fuel delivery under high pressures has allowed to substantiate the possibility of using the equation of state for the forward and backward account. An equation of state adequate to processes with high and ultrahigh pressures (up to 400 MPa) and moderately high temperatures (up to 460 K) has been proposed. The equipment used and the method of obtaining empirical information through determination of the current sound velocity are described. A method for calculating the values of constants of the chosen form of the equation of state in the form of expressions determining their dependence on temperature and an algorithm for calculating the constants of the equation of state in processing experimental data are presented. Based on literature data, as well as the results of studies conducted, sets of empirical equation of state constants for 49 diesel fuels, various test and technical fluids, and alternative motor fuels are obtained