Abstract: The gas dynamic function method proposed by Sokolov is a classical method for designing injectors. However, its assumptions based on ideal gases make it error-prone when it is applied to real gases under high pressures. The gas thermodynamic method was used in this study. The real gas adiabatic indices at isentropic temperatures and isentropic volumes were introduced from the definitions of enthalpy and constant-pressure specific heat. Combined with the energy equations, the theoretical formula of the real gas dynamic function was derived. The basic equations of gas injectors and pneumatic delivery injectors based on real gases were then derived according to the laws of momentum conservation and mass conservation. A comparison with Sokolov's design method showed that, under the low-pressure working condition, the computational results obtained using the revised method based on real gases were consistent with results obtained with Sokolov's design method, indicating that the revised design method covered Sokolov's design method. However, under the high-pressure working condition, the results for these two design methods were significantly different. The real gas correction compensated for the limitations of Sokolov's design method and can be applied to injector design for the entire pressure range.

Key words: ejector, design method, real gas, thermodynamics, gas dynamics function