![]() However, pressures and temperatures decrease rapidly and at different rates along the nozzle, and consequently, real gas effects and variations of properties can become significant. In general, at elevated temperatures, the effects of molecular attraction are negligible and compressibility factors of fluids are close to unity. Nevertheless, propellants and combustion products in advanced or conventional propulsion systems, such as electrothermal, microwave, laser, nuclear, and chemical rockets, can attain relatively high temperatures and pressures. The NASA CEA (Chemical Equilibrium and Applications) code is largely used for the preliminary design of rockets and calculates nozzle properties and propulsion parameters considering frozen or equilibrium one-dimensional flows of thermally perfect ideal gases. ![]() The classical equations for the calculation of rocket propulsion parameters are based on one-dimensional flows of ideal gases with constant properties. The effects of covolumes and intermolecular attraction forces on flow and propulsion parameters are analyzed. Errors of ideal gas solutions for calorically perfect and thermally perfect gases are determined with respect to van der Waals gases, for chamber temperatures varying from 1000 to 4000 K and chamber pressures from 5 to 35 MPa. Steady isentropic one-dimensional flows through a nozzle are assumed for the determination of specific impulse, characteristic velocity, thrust coefficient, critical flow constant, and exit and throat flow properties of He, H 2, N 2, H 2O, and CO 2 gases. ![]() This work derives new analytical solutions for propulsion parameters, considering gases obeying the van der Waals equation of state with specific heats varying with pressure and temperature. Variations in flow properties and the effects of real gases along a nozzle can become significant and influence the calculation of propulsion and thermodynamic parameters used in performance analysis and design of rockets. Propellants or combustion products can reach high pressures and temperatures in advanced or conventional propulsion systems.
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