TSFC vs Mach Number, Why does it increase?

In summary, the increase in TSFC and decrease in net thrust with Mach number can be attributed to the increasing pressure and temperature ratios, as well as the higher drag caused by faster moving air.
  • #1
firestarter7
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I have the Thrust Specific Fuel consumption plot for a turbofan engine versus the Mach Number. Until Mach = 1, the TSFC increases steadily for different flight altitude conditions (0 km...10 km, with the 0 km line on top and then 2km, 4 km etc). Can anyone tell me why TSFC increases with the Mach Number? I have also noticed that the fuel flow decreases with Mach Number. Why is that? And Why does Net thrust decrease with Mach number 0 km...10 km, with the 0 km line on top and then 2km, 4 km etc)? I am thankful for any help on this.
 
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  • #2
The increase in TSFC with Mach number is due to the increasing pressure ratio and temperature ratio across the compressor and turbine. As the Mach number increases, the pressure ratio and temperature ratio increase, resulting in the need for more fuel to be burned in order to produce the same amount of thrust. This increase in fuel flow results in a higher TSFC. The decrease in net thrust with Mach number is due to the higher drag caused by the faster moving air. As the Mach number increases, the air moving through the engine has to accelerate more quickly, causing an increase in drag and a decrease in thrust.
 

What is TSFC vs Mach Number and why is it important?

TSFC (Thrust Specific Fuel Consumption) vs Mach Number is a comparison of the amount of fuel consumed by an aircraft engine in relation to its thrust output at different speeds, or Mach numbers. It is important because it helps determine the efficiency of an engine and its performance at different flight speeds.

How does TSFC change with increasing Mach Number?

As Mach Number increases, so does TSFC. This is because at higher speeds, the engine needs to work harder to maintain thrust, which requires more fuel consumption. Therefore, the TSFC value increases as Mach Number increases.

Why does TSFC increase at higher Mach Numbers?

The increase in TSFC at higher Mach Numbers is due to the compressibility of air. As an aircraft moves faster, the air entering the engine compresses, causing the engine to work harder to maintain the same level of thrust. This results in increased fuel consumption and a higher TSFC value.

What is the relationship between TSFC and Mach Number?

The relationship between TSFC and Mach Number is directly proportional. This means that as Mach Number increases, TSFC also increases. This is because the engine needs more fuel to maintain thrust at higher speeds.

How does the design of an engine affect the relationship between TSFC and Mach Number?

The design of an engine can significantly impact the relationship between TSFC and Mach Number. A well-designed engine can have a lower TSFC value at high Mach Numbers, indicating more efficient fuel consumption. On the other hand, a poorly designed engine may have a higher TSFC value at high Mach Numbers, resulting in lower efficiency and increased fuel consumption.

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