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ME 18b, HW 5
Due Thursday May 14, 2009 (accepted until 4 pm)
Note:
This homework is due on a Thursday not a Tuesday
TAs for HW #5:
Dan Alvarez, Sunday 810 pm, SFL 229;
Mary Dorman, Monday 79 pm, SFL 331
Number of classes attended: ______
Hours spent on homework: _______
1.
Brayton Cycle Jet Aircraft Engine
The General Electric GE90 is a family of high
bypass turbofan engines built by GEAviation for the Boeing 777, with thrust ranging from
74,000 to 115,000 lbf (329 to 512 kN). It was first introduced in November 1995.
The GE90
series are physically the largest engines in aviation history. The fan diameter of the latest
variant, the GE90115B, has a diameter of 325 cm (128 in). This means that the GE90 has a
diameter larger than most cabins in business aircraft.
For more info on this engine go to:
http://www.turbokart.com/about_ge90.htm
Using the state numbers shown in the figure below for your analysis; determine the following
operating conditions of the engine as power is applied prior to takeoff while the plane is still
stationary on the runway:
a.
Air mass flow rate for a thrust of 400 kN.
b.
Air volumetric flow rate in m
3
/min and cfm.
c.
The work of the fan, compressor and turbine.
The fan has a pressure ratio of 2.1 and the
compressor has a pressure ratio of 19.0.
Ignore the portion of fan work that provides
bypass air (which is not shown).
d.
The heat input for final combustion temperature of T
5
= 1400 K.
e.
The exhaust velocity
f.
The fuel consumption in kg/hr if the fuel has a heating energy value of 45 MJ/kg.
You will need to make your own assumptions about the inlet conditions.
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Solution:
Assume inlet conditions are 100 kPa and 295K and Vin = 0.
A reasonable pressure range would
be from about 75 kPa to 102 kPa for a ground level of 7500 ft to 200 ft above sea level.
A
reasonable temperature range would be from 40° to +40°C (cold Canadian winters to hot desert
summers).
State 1: T1 = 22°C, 295K, h1 = 296 kJ.kg, Pr1 = 1.053
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