57.
In addition to the 'sea-level' tests, sample engines are tested to a flight evaluation test
Overhaul
schedule. These tests cover such characteristics as anti-icing, combustion and reheat efficiencies, performance, mechanical reliability, and oil and fuel consumptions at the variety of conditions to which the engine may be subjected during its operational life. Flight evaluation testing can be effected by installing the engine in an aircraft or in an altitude test cell (fig. 25-13) to test the variations of air humidity, pressure and temperature on the engine, its accessories and the oil and fuel systems. When in an aircraft, the engine is operated at the actual atmospheric conditions specified in the schedule, but in an altitude test cell, the engine is installed in an enclosed cell and tested to the schedule in conditions that are mechanically simulated.
58.
Mechanical simulation comprises supplying the engine inlet with an accurately controlled mass airflow at the required temperature and humidity, and adjusting the atmospheric pressure within the exhaust cell to coincide with pressure at varying altitudes.
59.
The data which is accumulated from either 'sea-level' or altitude testing is retained for future development, engine life assessment, material capa-bilities or any aspect of engine history.
60.
During the testing of turbo-jet engines there is a need to reduce the exhaust noise to within acceptable limits. This may be achieved by several different means, each involving costly equipment. However, a typical silencer would do this by expansion in the first section, damping by acoustic tubes and final diffusion by a large exit through which
Overhaul
the hot gas would be directed upwards at a low velocity.
Preparing for storage/despatch
61. The preparation of the engine/module for storage and/or despatch is of major importance, since storage and transportation calls for special treatment to preserve the engine. To resist corrosion during storage, the fuel system is inhibited by special oil and all apertures are sealed off. The external and internal surfaces of the engine are also protected by special inhibiting powders or by paper impregnated with inhibiting powder and the engine is enclosed in a re-usable bag (fig. 25-15) or plastic sheeting into which a specific amount of desiccant is inserted. If transportation by rail or sea is involved, the inhibited and bagged engine may be packed in a wooden crate or metal case.
Appendix 1
Conversion factors
UNIT ABBREVIATIONS
in = inch s = second km = kilometre (mx1000) ft = foot min = minute g = gram yd = yard h = hour kg = kilogram oz = ounce f = force N = newton lb = pound W = watt Pa = pascal cwt = hundredweight kW = kilowatt (Wx1000) kPa = kilopascal Btu = British thermal unit mm = millimetre (mx0.001) J = Joule hp = horsepower m = metre kJ = kilojoule (Jx1000) Hg = mercury MJ = megajoule (Jx1 000 000)
CONVERSION FACTORS - Exact values are printed in bold type.
LENGTH 1 in = 25.4 mm 1 ft = 0.3048 m 1 mile = 1 .60934 km 1 International nautical mile = 1.852 km
AREA 1 in2 = 645.16 mm2 1 ft2 = 92903.04 mm2
VOLUME 1 UK fluid ounce = 28413.1 mm3 1 US fluid ounce = 29573.5 mm3 1 Imperial pint = 568261.0 mm3 1 US liquid pint = 473176.0 mm3 1 UK gallon = 4546090.0 mm3 1 US gallon = 3785410.0 mm3 1 in3 = 16387.1 mm3 1 ft3 = 0.0283168 m3
MASS 1 oz (avoir.) = 28. 3495 g 1 lb = 0.45359237 kg 1 UK ton = 1.01605 tonne 1 short ton (2000 lb) = 0.907 tonne
DENSITY 1 lb/in3 = 27679.9 kg/m3
1 lb/ft3 = 16.0185 kg/m3
VELOCITY 1 in/min = 0.42333 mm/s
1 ft/min = 0.00508 m/s
1 ft/s = 0.3048 m/s
1 mile/h = 1.60934 km/h
1 International knot = 1.852 km/h
ACCELERATION 1 ft/s2 = 0.3048 m/s2
MASS FLOW RATE 1 lb/h = 1.25998x10-4 kg/s
FORCE 1 Ibf = 4.44822 N
1 kgf = 9.80665 N
1 tonf = 9964.02 N
PRESSURE 1 in Hg (0.0338639 bar) = 3386.39 Pa
1 Ibf/in2 (0.0689476 bar) = 6894.76 Pa
1 bar = 100.0 kPa
1 standard atmosphere = 101.325 kPa
MOMENT (torque) 1 Ibf in = 0.112985 Nm
1 Ibf ft = 1.35582 Nm
ENERGY/ HEAT/ WORK 1 hph = 2.68452 MJ
1 therm = 105.506 MJ
1 Btu = 1.05506 kJ
1 kWh = 3.6 MJ
HEAT FLOW RATE 1 Btu/h = 0.293071 W
POWER 1 hp (550 ft Ibf/s) = 0.745700 kW
KINEMATIC VISCOSITY 1 ft2/s = 929.03 stokes = 0.092903 m2/s
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