Chapter 2 Propulsion (Slides 21-49): Gas Cycles, Mach Number + Speed of Sound, Stagnation State + Flow

For the 2nd quiz as well. Refer to the first part for what else to study. (:

Area under P-V Diagram:

Work done for closed systems.
Area Enclosed = Net Cycle Work

Area under T-S Diagram:

Heat Transfer for the process
Net Heat Added = Area Enclosed

With an average temperature (increase/decrease), the thermal efficiency should?

Increase

Gas turbine operate on an open cycle where:

Air is taken from the atmosphere

Additional air that is bypassed around the combustor is used to:

keep the combustion chamber exit (turbine inlet) temperature low enough to allow the turbine to operate continuously.

Most of the turbine output is required to:

operate the compressor.

only the remainder is avliable to supply shaft work to generator, pump or other devices.

In a jet engine the turbine is designed to provide _________ output to drive compressor and auxiliary devices.

just enough

Bypass Ratio

ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core.

Quasi-Static Process

Thermodynamic process that happens slowly enough for the system to remain in internal equilibrium.

A reversible process quasi-static? (True/False)

True

Thrust is not a force (True/False)

False

Sound waves

infinitesimal (small) pressure waves propagating in a medium.

The propagation of acoustic/sound waves is reversible and adiabatic, therefore isentropic (True/False)

True

The speed of sound is _______ in liquids than gas (higher/lower)

higher

Assume a plane sound wave propagates in a:

medium at rest with speed ‘u’

Shock wave

type of propagating disturbance that moves faster than the local speed of sound. It also causes a abrupt change in temp, pressure, and density.

speed of sound equation:

a² = γRT

Flow in which the flow speed is faster than the local speed of sound

supersonic flow

In supersonic flow, the acoustic wave can be confined to a ______.
Hint: its a shape/geometric object

Cone

Stagnation State

reached in decelerating a flow to rest isentropically without any external work.

The stagnation state is referred to as the _____ state of the gas

total

There is an _________ relationship between the total pressure ratio and the entropy rise in an adiabatic flow

exponential

Calorically perfect gas

The specific heat capacity is a constant value.

Calorically imperfect gas

the specific heat capacity changes with temperature

In subsonic flow, a diffuser needs its exit area to ________ and for a nozzle the exit area to _______ (Input either: “Increase” OR “decrease”)

Increase; Decrease

In supersonic flow, a diffuser needs its exit area to ________ and for a nozzle the exit area to _______ (Input either: “Increase” OR “decrease”)

Decrease; Increase

One of the most fundamental and useful equations in Aerospace Engineering!
Hint: Aziz loves this equation!

Bernoulli’s Equation

Bernoulli Equation limitations

Only holds for inviscid (frictionless) and incompressible(constant density) flows.