A modern jet engine has a temperature after combustion of

Chapter 4, Problem 124HP

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QUESTION:

Problem 124HP

A modern jet engine has a temperature after combustion of about 1500 K at 3200 kPa as it enters the turbine section (see state 3, Fig. P4.124). The com pressor inlet is at 80 kPa, 260 K (state 1) and the outlet (state 2) is at 3300 kPa, 780 K; the turbine outlet (state 4) into the nozzle is at 400 kPa, 900 K and the nozzle exit (state 5) is at 80 kPa, 640 K. Neglect any heat transfer and neglect kinetic energy except out of the nozzle. Find the compressor and turbine specific work terms and the nozzle exit velocity.

FIGURE P4.124

Questions & Answers

QUESTION:

Problem 124HP

A modern jet engine has a temperature after combustion of about 1500 K at 3200 kPa as it enters the turbine section (see state 3, Fig. P4.124). The com pressor inlet is at 80 kPa, 260 K (state 1) and the outlet (state 2) is at 3300 kPa, 780 K; the turbine outlet (state 4) into the nozzle is at 400 kPa, 900 K and the nozzle exit (state 5) is at 80 kPa, 640 K. Neglect any heat transfer and neglect kinetic energy except out of the nozzle. Find the compressor and turbine specific work terms and the nozzle exit velocity.

FIGURE P4.124

ANSWER:

Solution 124 HP

Step 1 of 3

We have to find the compressor and turbine specific work terms and the nozzle exit velocity.

The Enthalpy of air at different states can be found from the Table A.7.1

State
         At 260 K and 80 kPa

State                                                    At 780 K and 3300 kPa

State 3                     At 1500 K and 3200 kPa

State                     At 900 K and 400 kPa

State                    At 640 K and 80 kPa

The compressor specific work term can be found using steady state single flow energy equation neglecting heat transfer and kinetic energy.

Where,

kJ/kg

kJ/kg

Thus,

                       

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