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QUESTION 2A compressor blade design tested in a cascade is found to choke with an inlet Mach number of0.9 when the inlet flow angle is 52 deg. If the ratio of the throat area to the frontal area, A*/H1s,for the cascade is).625, calculate the loss of stagnation pressure between the far upstream andthe throat and express this as a loss coefficient. Give your comments on what could cause thisloss.

Question
QUESTION 2
A compressor blade design tested in a cascade is found to choke with an inlet Mach number of
0.9 when the inlet flow angle is 52 deg. If the ratio of the throat area to the frontal area, A*/H1s,
for the cascade is).625, calculate the loss of stagnation pressure between the far upstream and
the throat and express this as a loss coefficient. Give your comments on what could cause this
loss.
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QUESTION 2 A compressor blade design tested in a cascade is found to choke with an inlet Mach number of 0.9 when the inlet flow angle is 52 deg. If the ratio of the throat area to the frontal area, A*/H1s, for the cascade is).625, calculate the loss of stagnation pressure between the far upstream and the throat and express this as a loss coefficient. Give your comments on what could cause this loss.

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check_circleAnswer
Step 1

Refer the compressible flow tables,

Q(M) 1.2698
2(1) 1.281
Po
Write the relation to calculate the stagnation pressure ratio from continuity equation
Po1
(M,)
Q(1)
cose
Po
Po1
1.2698
cos 520
(0.625)
1.281
=0.976446
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Q(M) 1.2698 2(1) 1.281 Po Write the relation to calculate the stagnation pressure ratio from continuity equation Po1 (M,) Q(1) cose Po Po1 1.2698 cos 520 (0.625) 1.281 =0.976446

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Step 2

Write the expression to calculate the ratio of inlet stagnation pressure at throat.

Po1
Р.
X
Po1
Po
Refer the compressible flow tables
0.5283 fory1.4 at Mach number 1.
Obtain the value of
as
Р.
ke
Po1
P
Substitute 0.5283 for
р
in Equation (I)
Р.
and 0.976446 for
1
1
Po1
X
0.5283 0.976446
=1.9385
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Po1 Р. X Po1 Po Refer the compressible flow tables 0.5283 fory1.4 at Mach number 1. Obtain the value of as Р. ke Po1 P Substitute 0.5283 for р in Equation (I) Р. and 0.976446 for 1 1 Po1 X 0.5283 0.976446 =1.9385

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Step 3

Write the expression to calculate t...

Po1 — Ро
Y
Po1 P
Po
1 -
Poi
(II)
1 -
Ро1
Substitute 0.976446 for 01 and 1.9385 for P01 in Equation (II).
Р.
р
1- (0.976446)
Y
1
1
1.9385
=0.0486
0.05
Generally compressor performance is affected by the following losses.
Viscous losses, shock losses, mixing losses and secondary losses like tip leakage flows. The
above mentioned losses affect the performance.
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Po1 — Ро Y Po1 P Po 1 - Poi (II) 1 - Ро1 Substitute 0.976446 for 01 and 1.9385 for P01 in Equation (II). Р. р 1- (0.976446) Y 1 1 1.9385 =0.0486 0.05 Generally compressor performance is affected by the following losses. Viscous losses, shock losses, mixing losses and secondary losses like tip leakage flows. The above mentioned losses affect the performance.

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