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In typical jet-engine testings, a static thrust stand similar to the one shown below is used to mount engine. In engine testing, pressure is usually expressed in gauge pressure. At the engine inlet, air is stea introduced, and its cross-sectional area is 1.2 m². The inlet, condition is given by 250 m/s. 50 kPa (ga

In typical jet-engine testings, a static thrust stand similar to the one shown below is used to mount engine. In engine testing, pressure is usually expressed in gauge pressure. At the engine inlet, air is stea introduced, and its cross-sectional area is 1.2 m². The inlet, condition is given by 250 m/s. 50 kPa (ga

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
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In typical jet-engine testings, a static thrust stand similar to the one shown below is used to mount the engine. In engine testing, pressure is usually expressed in gauge pressure. At the engine inlet, air is steadily introduced, and its cross-sectional area is 1.2 m². The inlet condition is given by 250 m/s, 50 kPa (gauge) and -50°C. The nozzle-exhaust gas has a velocity of 550 m/s, and its absolute pressure is 101 kPa, the same as the atmospheric pressure. (a) Estimate the thrust force applied to the stand during the engine testing. Assume that the incoming air has the same mass flow rate as the exhaust gas. (b) Repeat (a) when fuel supplied to the engine is taken into account. The fuel mass flow rate into the engine is equal to 2% of the mass flow rate of incoming air. Which thrust force is likely to provide more accurate estimation? 250 m/s 50 kPa -50°C Jet engine Open atmosphere 550 m/s 0 kPa Static thrust stand Thrust
Transcribed Image Text:In typical jet-engine testings, a static thrust stand similar to the one shown below is used to mount the engine. In engine testing, pressure is usually expressed in gauge pressure. At the engine inlet, air is steadily introduced, and its cross-sectional area is 1.2 m². The inlet condition is given by 250 m/s, 50 kPa (gauge) and -50°C. The nozzle-exhaust gas has a velocity of 550 m/s, and its absolute pressure is 101 kPa, the same as the atmospheric pressure. (a) Estimate the thrust force applied to the stand during the engine testing. Assume that the incoming air has the same mass flow rate as the exhaust gas. (b) Repeat (a) when fuel supplied to the engine is taken into account. The fuel mass flow rate into the engine is equal to 2% of the mass flow rate of incoming air. Which thrust force is likely to provide more accurate estimation? 250 m/s 50 kPa -50°C Jet engine Open atmosphere 550 m/s 0 kPa Static thrust stand Thrust
Expert Solution
Step 1

Given:

Area at inlet is, A1=1.2 m2.

Velocity at inlet is, v1=250 m/s.

Pressure at inlet is, P=50 kPa.

Temperature at inlet is, T1=-50°C=223 K.

The velocity at outlet is, v2=550 m/s.

The pressure at outlet is, P2=0 kPa.

The absolute pressure is, Pabs=101 kPa.

Part-(a)

The volume flow rate at inlet can be calculated as,

V1=A1×v1

Substitute all the values in the above equation,

V1=1.2×250V1=300 m3/s

Mass flow rate can be calculated as,

m˙=P1V1RT1..................................(1)

Here,

P1=50+PabsP1=50+101P1=151 kPa

The value of R (gas constant) for air is, 0.287 kJ/kg.K.

Substitute all the values in the equation (1),

m˙=151×3000.287×223m˙=4530064.001m˙=707.80 Kg/s

We know that the rate of change of momentum is equal to the force.

The thrust force can be calculated as,

F˙=mexit×v2-min×v1F˙=m˙v2-v1            (mexit=min=m˙)

Substitute all the values in the above equation,

F˙=707.80×550-250F˙=212340 NF˙=212.340 KN

Thus, the thrust force applied is, 212.340 kN.

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