Home » Mechanical Engineering » Compressors, Gas Dynamics and Gas Turbines

Propulsive efficiency condition for a rocket A rocket achieves maximum overall propulsive efficiency when the aircraft (vehicle) flight speed is how related to the jet exhaust velocity? Choose the correct option.

Difficulty: Easy

Equal to the jet velocity
Half of the jet velocity
Double the jet velocity
Much less than the jet velocity

Correct Answer: Equal to the jet velocity

Explanation:

Concept/Approach
Propulsive efficiency depends on the velocity match between the vehicle and the exhaust. For momentum devices (including rockets), efficiency is maximized when flight speed ≈ jet speed, minimizing kinetic energy wasted in the exhaust slipstream.

Final Answer
Equal to the jet velocity

← Previous Question Next Question→

More Questions from Compressors, Gas Dynamics and Gas Turbines

Degree of reaction in an axial-flow compressor: precise definition How is the degree of reaction (R) defined for an axial-flow compressor stage? Choose the correct option.
Typical overall compression ratio in simple gas-turbine cycles Select a representative simple-cycle gas turbine compressor pressure ratio used in basic textbook problems and older industrial sets. Choose the correct option.
Compressor performance terminology: delivered air volume The term used for the volume of air delivered by a compressor (referred to standard free-air conditions) is: Choose the correct option.
Applications of compressed air: identify the correct set Which of the following are common uses of compressed air in mechanical/thermal systems? Choose the correct option.
Compressor terminology: identify the parameter that equals work per cycle divided by stroke volume. Definition focus: In reciprocating compressors, the ratio (workdone per cycle)/(stroke volume) is called what? Choose the correct term.
Compressor fundamentals: select the correct statement among the following. Evaluate each statement about definitions and work in air compression, and choose the only correct one.
Clearance volume and volumetric efficiency in compressors: validate the statement for design practice. Statement to evaluate: Clearance volume is kept as small as possible because it adversely affects volumetric efficiency. Choose whether the statement is correct.
Perfect (complete) intercooling criterion in two-stage air compression: identify the temperature condition. Condition to classify perfect intercooling: Temperature of air leaving the intercooler is ________ the original atmospheric (inlet) air temperature. Choose the correct relation.
Pressure rise mechanism in a sliding vane blower: evaluate the two-stage explanation. Statement to evaluate: In a vane blower, the pressure increases first due to internal compression (decreasing cell volume) and then due to some backflow from the discharge until line pressure is reached. Choose whether the statement is correct.
Purpose of intercooling in multi-stage air compressors: choose the primary objective. Select the main reason intercoolers are used between compression stages.

Discussion & Comments

No comments yet. Be the first to comment!

Join Discussion