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bd40bc7c7a Suppose that our steady flow control volume is a set of streamlines describing the flow up to the nose of a blunt object. Considering the state of the gas within the inlet, prior to passage into the compressor, as state (1), and working in the reference frame of the motionless airplane:. Equal, by the same argument as a). Frequently, however, we are interested only in the work that crosses the system boundary, not the volumetric or flow work. Also, for now we will assume that the gas behaves as an ideal gas, though in general this is a poor approximation. Heat is added, a compressor is doing work on the system, the flow entering the system does work on the system (work = -p1V1), and work is done by the system through pushing out the flow (work = +p2V2). The steady flow energy equation tells us that if there is no heat or shaft work (the case for our adiabatic inlet) the stagnation enthalpy (and thus stagnation temperature for constant Cp) remains unchanged.
Thus TT1= TTatm = Tatm. For the case shown below, a jet engine is sitting motionless on the ground prior to take-off. Homework 9 (PDF) . What if the body or reference frame is moving? We know from looking at re-entry vehicles, that the skin temperature is much hotter than the atmospheric temperature. (The Mach number, M, is the ratio of the flow speed, c, to the speed of sound, a. If there is also no heat transferred to the flow (adiabatic), then the steady flow energy equation becomes. If the atmosphere is assumed still, and we stagnate a fluid particle on the nose of a high speed vehicle (carrying it along with the vehicle and thus essentially giving it kinetic energy) its stagnation temperature is given by where c is the vehicle speed. This energy is composed of two parts: the internal energy of the fluid (u) and the flow work (pv) associated with pushing the mass of fluid across the system boundary. Q6.11 (PDF) Q6.12 (PDF) Example: . Flow through a rocket nozzle A liquid bi-propellant rocket consists of a thrust chamber and nozzle and some means for forcing the liquid propellants into the chamber were they react, converting chemical energy to thermal energy.