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The isentropic efficiency is . The variation of fluid density for compressible flows requires attention to density and other fluid property relationships. The fluid equation of state, often unimportant for incompressible flows, is vital in the analysis of compressible flows. Also, temperature variations for compressible flows are usually ...
In the classical regime, expansions are smooth isentropic processes, while compressions occur through shock waves, which are discontinuities in the flow. If gas-dynamics is inverted, the opposite occurs, namely rarefaction shock waves are physically admissible and compressions occur through smooth isentropic processes. [24]
Most steady-flow devices operate under adiabatic conditions, and the ideal process for these devices is the isentropic process. The parameter that describes how efficiently a device approximates a corresponding isentropic device is called isentropic or adiabatic efficiency. [12] Isentropic efficiency of turbines:
Figure 1: A de Laval nozzle, showing approximate flow velocity increasing from green to red in the direction of flow Density flow in a nozzle. A rocket engine nozzle is a propelling nozzle (usually of the de Laval type) used in a rocket engine to expand and accelerate combustion products to high supersonic velocities.
Furthermore, stage efficiency is the product of blade efficiency and nozzle efficiency, or =. Nozzle efficiency is given by η N = V 2 2 2 ( h 1 − h 2 ) {\displaystyle \eta _{N}={\frac {{V_{2}}^{2}}{2\left(h_{1}-h_{2}\right)}}} , where the enthalpy (in J/Kg) of steam at the entrance of the nozzle is h 1 {\displaystyle h_{1}} and the enthalpy ...
During an isentropic expansion process the working fluid always ends in the two-phase (also called wet) zone, if it is a wet-type fluid. If the fluid is of dry-type, the isentropic expansion necessarily ends in the superheated (also called dry) steam zone. If the working fluid is of isentropic-type, after an isentropic expansion process the ...
In practice, the flow of steam through a nozzle is not isentropic, but accompanied with losses which decrease the kinetic energy of steam coming out of the nozzle. The decrease in kinetic energy is due to: viscous forces between steam particles, heat loss from steam before entering the nozzle, deflection of flow in the nozzle,
The stagnation state of the gas at the nozzle entry is represented by point 01. The gas expands adiabatically in the nozzles from a pressure p 1 to p 2 with an increase in its velocity from c 1 to c 2. Since this is an energy transformation process, the stagnation enthalpy remains constant but the stagnation pressure decreases (p 01 > p 02) due ...