USE EXCEL TO SOLVE THE HOMEWORK
THE HOMEWORK FILE IS ATTACHED FOR BETTER READ. H
USE EXCEL TO SOLVE THE HOMEWORK
THE HOMEWORK FILE IS ATTACHED FOR BETTER READ. HOWEVER, IT IS BELOW TO GIVE YOU AN IDEA OF WHAT IT IS
.Question 1:The purpose of this question isto examine the governing parameters that
dictate the overall performance of a turbojet engine.
Part 1: Generate a plot of (1) Specific Thrust, (2) Overall Efficiency, (3) Thermal
Efficiency, and (4) Propulsive Efficiency vs. Flight Mach Number (0 < Mo < 3) for an
idea turbojet with a turbine inlet temperature of 1600 K and compressor pressure ratio of
25. Comment on the implications of these results.
Part 2: Examine the impact of flight Mach number and turbine inlet temperature for a
turbojet engine flying at an altitude of 12 km. Generate the following plots and comment
on the implications of your results:
2.1: Plot of (1) Specific Thrust, (2) Overall Efficiency, (3) Thermal Efficiency,
and (4) Propulsive Efficiency for Flight Mach number of M=0.85 and M=1.2 vs.
Compressor pressure ratio, c, using a turbine inlet temperature, Tt4=1400 K.
2.2: Plot of (1) Specific Thrust, (2) Overall Efficiency, (3) Thermal Efficiency,
and (4) Propulsive Efficiency for Flight Mach number of M=0.85 vs. Compressor
pressure ratio, c, using turbine inlet temperatures, Tt4=1400 K and Tt4=1800 K.
2
Question 2: In all of the developments that we have carried out thus far, we have
assumed that the compression and expansion processes in the aircraft engines were
reversible and adiabatic. This, of course, is not the case because entropy increases in all
real compressors, turbines, inlets and nozzles. To take this into account, we can define an
adiabatic efficiency for any such compression or expansion process. For a compression
process is it is defined as:
Adiabatic Efficiency = Ideal Work of Compression / Actual Work of Compression
The pressure ratio is the same in both the idea and actual process. Translating this into a
mathematical expression gives:1
1
1
−
−
=
−
c
c
c
2.1
We could describe the case for a turbine as:
Adiabatic Efficiency = Actual Work of Expansion / Ideal Work of Expansion
The mathematical expression of this statement for the turbine is:
1
1
1
−
−
−
=
t
t
t
2.2
The purpose of this question is to allow you to explore the effect of compressor
inefficiency on the performance of a turbojet engine.
Part 1: Derive an expression for the thrust per unit mass flow, including (only) the effect
of compressor inefficiency less than unity. Use the compressor temperature ratio, c, and
the efficiency, c, (defined above) to characterize the compressor.
Part 2: Derive a corresponding expression for the specific impulse.
Part 3: Calculate the thrust per unit of airflow and the specific impulse for t=7, Mo=1,
c=2, for a range of c from 1.0 to 0.7. Plot and comment on these results.
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