A de Laval nozzle of exit-to-throat area ratio and throat area is fed with air ( , )…

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Waves, acoustics and compressible flow · Waves, acoustics and compressible flow

Signal Speeds in Fluids, Ch Flow through nozzles: area change, choking and thrust

Problem

A de Laval nozzle of exit-to-throat area ratio

2.00

and throat area

10.0\,\mathrm{cm^2}

is fed with air (

\gamma=1.4

R=287.05\,\mathrm{J\,kg^{-1}\,K^{-1}}

) from a reservoir at

p_0=500\,\mathrm{kPa}

and

T_0=300\,\mathrm K

. The back pressure

p_{\mathrm b}

can be set to

480

200

50

20\,\mathrm{kPa}

. ((a)) Find the two exit pressures that divide the back-pressure axis for this nozzle, and classify the operating regime at each of the four back pressures. ((b)) At

p_{\mathrm b}=480\,\mathrm{kPa}

, find the exit Mach number, the mass flow and the Mach number at the throat. ((c)) Find the mass flow at the other three back pressures, and say for which of them this chapter tells us the flow inside the nozzle. ((d)) At

p_{\mathrm b}=20\,\mathrm{kPa}

, find the exit Mach number, exit pressure and exit speed, and say what the jet does after it leaves.

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