An ideal simple gas turbine has a compression ratio of 5. What is its

In summary, we are given a simple gas turbine with a compression ratio of 5 and a ratio of specific heats of 1.4. We are asked to find the efficiency of the turbine, as well as the work ratio and heat rejected when the turbine produces 6 MW and the compressor requires 2 MW to drive it. With the given information, we can use the equations c=r(γ-1/γ) and η=1-(1/c) to find the efficiency and work ratio, but we need additional information to calculate the heat rejected.
  • #1
qablos
13
0

Homework Statement


An ideal simple gas turbine has a compression ratio of 5. What is its


Homework Equations


c=r(γ-1/γ)
η=1-(1/c)

The Attempt at a Solution


I'm stuck, I think I need to use the above equations and possibly more. I just don't know how to find a value for the ratio of specific heats,γ.
 
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  • #2


Do you have any other information about the compressor apart from its pressure ratio?
 
  • #3


rock.freak667 said:
Do you have any other information about the compressor apart from its pressure ratio?

Yeah:
"The turbine
produces 6 MW (gross) and the compressor requires 2 MW to drive it."
It's just put after the question, so I assumed I need to use the compression ratio which is 5.
 
  • #4


Given the pressure ratio alone, I don't think you can find the ratio of the specific heat capacities.

I am assuming that is what you were asked to find.
 
  • #5


Can you post the entire text of the problem? It looks like something is missing after
"What is its ..."
 
  • #6


SteamKing said:
Can you post the entire text of the problem? It looks like something is missing after
"What is its ..."

An ideal simple gas turbine has a compression ratio of 5. What is its efficiency? If the turbine
produces 6 MW (gross) and the compressor requires 2 MW to drive it, what is the work ratio and how much heat is
rejected?
 
  • #7


The ratio of specific heats is that for air, which is 1.4
 
  • #8


SteamKing said:
The ratio of specific heats is that for air, which is 1.4

I've done it now thanks!

But how do I calculate the heat rejected? :/
 
  • #9


I assume that the efficiency for the turbine was not 1.0. You know how much work output was obtained from the turbine. The efficiency of the turbine relates the output to the total heat input.
 

1. What is a compression ratio in a gas turbine?

A compression ratio in a gas turbine is the ratio of the volume of air entering the compressor to the volume of air leaving the compressor. It is an important factor in determining the efficiency of a gas turbine.

2. Why is a compression ratio of 5 considered ideal for a gas turbine?

A compression ratio of 5 is considered ideal for a gas turbine because it provides a good balance between efficiency and power output. Higher compression ratios can lead to increased efficiency but also require more energy, while lower ratios may result in lower efficiency and power output.

3. How does the compression ratio affect the performance of a gas turbine?

The compression ratio directly affects the performance of a gas turbine. A higher compression ratio can lead to increased efficiency and power output, while a lower ratio may result in decreased efficiency and power output.

4. What factors determine the ideal compression ratio for a gas turbine?

The ideal compression ratio for a gas turbine is determined by several factors, including the design of the compressor, the type of fuel used, and the desired power output. It is also influenced by the operating conditions and environmental factors.

5. Is a compression ratio of 5 the same for all gas turbines?

No, a compression ratio of 5 is not the same for all gas turbines. The ideal compression ratio can vary depending on the specific design and purpose of the gas turbine. Other factors, such as altitude and ambient temperature, can also affect the ideal compression ratio for a gas turbine.

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