Calculating Velocity of Exit Stream in Aircraft - George

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SUMMARY

The discussion focuses on calculating the velocity of the exit stream in aircraft, specifically in the context of jet engines. Key factors include thrust, intake velocity, inlet diameter, and air density (ρ). George highlights that while thrust is defined as momentum per time, the necessary information to accurately determine exit velocity is insufficient due to the varying temperatures and densities between the intake and exit streams. Additionally, the pressure difference in supersonic conditions plays a crucial role in thrust generation.

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  • Understanding of jet engine propulsion mechanisms
  • Knowledge of fluid dynamics principles
  • Familiarity with thermodynamics, particularly temperature and density variations
  • Basic grasp of thrust calculations in aerospace engineering
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Aerospace engineers, students studying propulsion systems, and professionals involved in aircraft design and performance optimization will benefit from this discussion.

skydvr8029
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I would like to get some help if possible. I am trying to determine the correct formula to calculate the velocity of the exit stream in an aircraft. I know the thrust, the velocity of the intake, inlet diameter, and air density (ρ). Thanks for any help.

George
 
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Thrust is momentum per time - with the known mass flow (mass per time: you have density, velocity and area), you can calculate the velocity difference between intake and exit.
 
It depends on the propulsion mechanism. Is this a jet engine? Because if you are considering a jet engine I don't think you have enough information. The temperature of the exit stream is significantly higher than the inlet temperature which means the density is different between intake and exit. So you can determine the mass flux but you do not have sufficient information to determine the velocity. In addition, if the exit stream is supersonic and is not perfectly expanded then the pressure difference between intake and exit will also be contributing to the thrust.
 

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