Jet Engine Mass Flow Rate calculation

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Discussion Overview

The discussion centers on calculating the air mass flow rate in jet engines, exploring methods and formulas related to thrust and specific impulse (Isp). Participants consider thermodynamic principles, momentum balances, and specific engine examples to address the problem.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant inquires about the formula for air mass flow rate in jet engines, referencing the thrust/Isp equation used in rocket calculations.
  • Another participant suggests starting with a thermodynamic heat balance and asks for details on inlet and outlet conditions, as well as the thrust/Isp equation.
  • A participant provides equations for total mass flow rate and fuel mass flow rate in rocket engines, mentioning the fuel-to-oxygen mixture ratio and referencing specific jet engine models.
  • Another participant emphasizes the need for inlet and outlet velocities, stating that Isp alone is insufficient and proposing a momentum balance for the control volume.

Areas of Agreement / Disagreement

Participants express differing views on the necessary parameters and methods for calculating air mass flow rate, indicating that multiple competing approaches remain without consensus.

Contextual Notes

Participants mention the importance of specific conditions such as velocities and thermodynamic states, which may not be fully defined in the discussion. The reliance on specific engine examples may limit the general applicability of the proposed methods.

vincentryan
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hi
how to find air mass flow rate in jet engine?
we are using thrust/Isp equation to find the mass flow rate for rocket equation. is that any formula available for finding the mass flow rate in jet engine
 
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You could start with a simple thermodynamic heat balance to get a ballpark figure.

Do you have any information on the inlet and outlet conditions or intermediate conditions like the compressor outlet to the turbine inlet?

What is the thrust/Isp equation? Can you post it?

Thanks
Matt
 
For Rocket,
Total Mass Flow rate W = F (Thrust) / Isp (Specific Impulse)
Fuel Mass Flow Rate Wf = W/(r+1)
Oxygen Mass Flow Rate Wo = W-Wf

r = fuel - oxygen mixture ratio

you have asked information about the inlet and outlet conditions or intermediate conditions like the compressor outlet to the turbine inlet.
Take on example of GE 90 - 110B and GE 90 - 110B1 engine.

the fuel flow rate for jet engine is calculated by the following equations
mfuel = Fuel flow rate=mair(f/a)/(B+1)
f/a=Cpg(To5-To4)/HV

help to fine the air mass flow rate
 

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