30 Questions
What is replaced by a constant-pressure heat-rejection process in a closed-loop Brayton cycle?
Exhaust process
Which process in a Brayton cycle involves Isentropic compression?
Compression in a compressor
What does the thermal efficiency of an ideal Brayton cycle depend on?
Pressure ratio and specific heat ratio
When neglecting kinetic and potential energy changes, the energy balance for a steady-flow process can be expressed how?
On a unit-mass basis
What type of process is the constant-pressure heat addition in a Brayton cycle?
Isobaric
Which part of the Brayton cycle involves a constant-pressure heat-rejection process?
4-1 Constant-pressure heat rejection
What is the net thrust developed by a turbojet engine when the pressures at the inlet and exit are identical?
Friday, February 10, 2023 NAA 122
What is the mass flow rate typically taken as in a turbojet engine?
The combustion rate of the fuel
Why do commercial airplanes save fuel by flying at higher altitudes during long trips?
To minimize the drag force from thinner air
What is the power developed from the thrust of a turbojet engine called?
Propulsive power WP
What does the net work developed by a turbojet engine equal to?
Zero
Why can't we define the efficiency of a turbojet engine in the same way as stationary gas turbine engines?
Because a turbojet engine's net work is zero
Which type of engine has greater cooling & lubrication requirements?
Four-stroke cycle engine
Why is the power produced by the same size engine more in a two-stroke cycle engine?
Because of lesser time for induction
Which engine type contains valves and valve mechanisms?
Two-stroke cycle engine
In which engine type is the part load efficiency better than a four-stroke cycle engine?
Two-stroke cycle engine
Which engine type is used where efficiency is important, such as in cars, buses, trucks, tractors, etc.?
Four-stroke cycle engine
Why does a two-stroke cycle engine have greater volumetric efficiency?
Due to greater time of induction
What is the major difference between the ideal jet propulsion cycle and the simple ideal Brayton cycle?
The gases are expanded to a pressure such that the turbine power just drives the compressor.
What is the significance of the pressure ratios for aircraft gas turbines?
Aircraft gas turbines operate at pressure ratios between 10 and 25.
What assumption is made about the turbine work in an ideal jet propulsion cycle?
The turbine work is equal to the compressor work.
What is the role of a diffuser in an aircraft gas turbine?
To increase the pressure of the incoming air.
What determines the thrust developed in a turbojet engine?
The difference in momentum between incoming air and exhaust gases.
Why does the net work output of a jet propulsion cycle equal zero?
Because the turbine work is sufficient to drive only the compressor and auxiliary equipment.
What is propulsive efficiency a measure of?
How efficiently thermal energy released during the combustion process is converted to propulsive energy
What is the desired output in a turbojet engine for propulsive efficiency calculation?
Power produced to propel the aircraft
What type of engine is the most widely used in aircraft propulsion?
Turbofan engine
What principle is a turbofan engine based on?
A large volume of slower moving air produces more thrust than a small volume of fast-moving air
Which cycles are considered totally reversible according to the text?
Carnot, Ericsson, and Stirling cycles
Which cycles may involve irreversibilities external to the system?
Otto, Diesel, and Brayton cycles
Learn about the characteristics of the ideal jet propulsion cycle where the net work output is zero and gases are expanded to a pressure just enough to drive the compressor and auxiliary equipment. Understand how this cycle differs from the simple ideal Brayton cycle.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
