Handbook of Turbomachinery Second Edition Revised - Ventech!

pressures at critical points. These data may be obtained during
certification tests as well.
Engine vibration survey.
Bird ingestion or foreign object damage (FOD) tests.
Bird ingestion tests are performed to determine the robustness of the
engine components to withstand the effects of ingestion of foreign objects
such as a bird (1 to 4 lbm), piece of tire tread, sand, gravel or water, ice and
hail. According to FAA regulations, the engine is required to demonstrate
that the ingestion of a bird 4 lbm in weight, fired at the engine at a maximum
climb speed of 250 knots (273 miles/hr), should cause no fire, fan or rotor
burst, or loss in shutdown capability. The regulations stipulate further that a
1 lbm bird fired several times at the engine at an initial climb speed of 150
knots (173 miles/hr) should cause less than 25% thrust loss with no
shutdown. (A certain minimum number of test firings proportional to the
area based on the engine inlet flange diameter is required.) This test is more
severe in its effects than the 4-lbm bird ingestion test. The ingestion of water,
ice, or hail should cause no thrust loss or shutdown of the engine.
FAA Certification Tests and Military Quality Tests. Figure 18 shows the
engine cycle for FAA accelerated mission test, which specifies variations in
power level plotted against time. Each cycle shown lasts 26.4 min. The total
duration of the test is 150 hr. The engine is expected to operate satisfactorily
over the whole period with no deterioration in performance. At the end of
the test, inspection should indicate no signs of distress at any of the
components.
Future of Mechanical and Thermal Design
As seen in the foregoing, improved materials, better analytical techniques
including unsteady flow prediction capability, and better experimental
methods to understand the local effects of stress and heat transfer are
necessary to improve the capabilities for design. These improvements may
be expected to permit the design of more durable machines with improved
performance. The following paragraphs provide a very limited sample of
some of the areas that are showing signs of promise for future developments.
Improved Materials
Ceramics for Airfoils and Turbine Disks. Ceramics have certain
characteristics that make them admirably suited for use in hightemperature
applications. These are
Copyright © 2003 Marcel Dekker, Inc.