Question

I ONLY NEED ANSWERS TO F.) AND G.)

I SOLVED THE REST. THANK YOU!

The Boeing 747 has a cruising altitude of 45,000 feet and cruising speed of 275 m/s. At this elevation, the temperature and pressure according to the US Standard Atmosphere (air properties as a function of altitude) are 220K and 1.8x104 Pa, respectively. The engines are steady state devices that can be modeled using the 1st Law of Thermodynamics with air (ideal gas) as the working fluid undergoing several processes. a. The inlet area of the engines is 0.5 m2. What is the mass flow rate (per engine)? I got 39.19 kg/s b. The first stage (inlet) of the jet engine is a diffuser. If the exit of the diffuser is 0.6 m2, T2 = 250K and P2 = 25200 Pa, what is the air velocity after the diffuser process? (State 2 is the exit of the first stage and the entrance to the compressor) I got 186 m/s c. The engine compressor is rated at 30 MW and the air entering the compressor is at 250K. What is the temperature at the exit of the compressor if the process is assumed to be adiabatic? For more accuracy, use the “ideal-gas properties of air” table (Table A17 in the provided Thermo property tables) for properties you may need. I got 1320 K d. The working fluid enters the combustor after the compression process. At the cruising speed, each engine consumes 1 L/s of jet fuel. What is the rate of heat release per engine if the volumetric energy density of jet fuel is 35 MJ/L? I got 35 Mj/s e. Model the combustor as a heat exchanger in which the heat from combustion gets transferred to the working fluid as an outside heat source (not like the real combustor pictured above). What is the specific (intensive) enthalpy change using this model assuming there is no heat loss in the combustor? I got 893 kJ/kg

f. Using the Table again, what is the specific enthalpy and temperature after combustion?

g. The turbine in the jet engine only needs to supply enough power to compress the air in the compressor. What is the temperature of the air at the exit of the turbine assuming this turbine process is adiabatic with negligible kinetic energy change?

Answer #1

As a propulsion engineer, you are tasked with testing
the turbojet engine of an aircraft to determine its performance
characteristics. The turbojet engine is analyzed on an
air-standard basis based on the Brayton cycle. Air, with a velocity
of 265 m/s and volumetric flow rate of 230 m3/s, enters
the diffuser at 18 kPa, -57oC, and exits at 30
kPa. The compressor pressure ratio is 15 to 1. The
maximum temperature exiting the combustor is 1087oC. The
pressure exiting the nozzle is...

1) A nozzle is a device for increasing the velocity of a
steadily flowing stream of fluid. At the inlet to a certain nozzle
the enthalpy of the fluid is 3025 kJ/kg and the velocity is 60 m/s.
At the exit from the nozzle the enthalpy is 2790 kJ/kg. The nozzle
is horizontal and there is negligible heat loss from
it.
(i) Find the velocity at the nozzle exit.
(ii) If the inlet area is 0.1 m2 and specific volume...

1) 20 kg/min water at 20º C is mixed adiabatically with 40
kg/min water at 80 ºC. What is the outlet water temperature?
Select one:
a. 80 °C
b. 60 °C
c. 50 °C
d. 70 °C
2)
Steam at 0.8 MPa and 500 ºC is throttled over a well insulated
valve to 0.6 MPa, what is the outlet temperature
Select one:
a. 450 ºC
b. 500 ºC
c. DOF>0
d. 400 ºC
3)
Humid air at 70 C and...

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