Aircraft Engine Design Pdf Free 11 |TOP|

Aircraft Engine Design Pdf Free 11 |TOP|

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The applicant must prepare Instructions for Continued Airworthiness in accordance with appendix A to this part that are acceptable to the Administrator. The instructions may be incomplete at type certification if a program exists to ensure their completion prior to delivery of the first aircraft with the engine installed, or upon issuance of a standard certificate of airworthiness for the aircraft with the engine installed, whichever occurs later.

The engine must operate properly with the accessory drive and mounting attachments loaded. Each engine accessory drive and mounting attachment must include provisions for sealing to prevent contamination of, or unacceptable leakage from, the engine interior. A drive and mounting attachment requiring lubrication for external drive splines, or coupling by engine oil, must include provisions for sealing to prevent unacceptable loss of oil and to prevent contamination from sources outside the chamber enclosing the drive connection. The design of the engine must allow for the examination, adjustment, or removal of each accessory required for engine operation.

The engine must be designed and constructed to function throughout its normal operating range of crankshaft rotational speeds and engine powers without inducing excessive stress in any of the engine parts because of vibration and without imparting excessive vibration forces to the aircraft structure.

The operation test must include the testing found necessary by the Administrator to demonstrate backfire characteristics, starting, idling, acceleration, overspeeding, functioning of propeller and ignition, and any other operational characteristic of the engine. If the engine incorporates a multispeed supercharger drive, the design and construction must allow the supercharger to be shifted from operation at the lower speed ratio to the higher and the power appropriate to the manifold pressure and speed settings for rated maximum continuous power at the higher supercharger speed ratio must be obtainable within five seconds.

Each engine must be designed and constructed to function throughout its declared flight envelope and operating range of rotational speeds and power/thrust, without inducing excessive stress in any engine part because of vibration and without imparting excessive vibration forces to the aircraft structure.

Each hydraulic actuating system must function properly under all conditions in which the engine is expected to operate. Each filter or screen must be accessible for servicing and each tank must meet the design criteria of § 33.71.

Each applicant, except an applicant for an engine being type certificated through amendment of an existing type certificate or through supplemental type certification procedures, must complete one of the following tests on an engine that substantially conforms to the type design to establish when the initial maintenance inspection is required:

If the engine is designed to operate with a propeller, the following tests must be made with a representative propeller installed by either including the tests in the endurance run or otherwise performing them in a manner acceptable to the Administrator:

An applicant seeking type design approval for an engine to be installed on a two-engine airplane approved for ETOPS without the service experience specified in part 25, appendix K, K25.2.1 of this chapter, must comply with the following:

Most modern passenger and military aircraft are powered bygas turbine engines, which are also calledjet engines. There are several different typesof gas turbine engines, but all turbine engines have some partsin common. All turbine engines have an inlet to bringfree stream air into the engine. The inletsits upstream of the compressor and,while the inlet does no work on the flow,inlet performancehas a strong influence on engine netthrust.As shown in the figures above, inlets come in a variety ofshapes and sizes with the specifics usually dictated by the speed ofthe aircraft.

An inlet for asupersonicaircraft, on the other hand, has arelatively sharp lip. The inlet lip is sharpened to minimize theperformance losses fromshock wavesthat occur during supersonicflight. For a supersonic aircraft, the inlet must slow the flow downto subsonic speeds before the air reaches the compressor. Somesupersonic inlets, like the one at the upper right, use a centralcone to shock the flow down to subsonic speeds. Other inlets, likethe one shown at the lower left, use flat hinged plates to generatethe compression shocks, with the resulting inlet geometry having arectangular cross section. This variable geometry inlet isused on the F-14 andF-15 fighter aircraft. More exotic inlet shapes are usedon some aircraft for a variety of reasons.The inlets of theMach 3+SR-71 aircraft are specially designed to allowcruising flight at high speed.The inlets of the SR-71 actually produce thrust during flight.

Inlets forhypersonicaircraft present the ultimate design challenge. Forramjet-poweredaircraft, the inlet must bring the high speed external flowdown to subsonic conditions in theburner. High stagnation temperatures are presentin this speed regime and variable geometry may not be an option for theinlet designer because of possible flow leaks through the hinges.Forscramjet-poweredaircraft, the heat environment is even worse because the flightMach number is higher than that for a ramjet-powered aircraft.Scramjet inlets are highly integrated with the fuselage of theaircraft. On the X-43A, the inlet includes the entire lowersurface of the aircraft forward of the cowl lip. Thick, hotboundary layersare usually present on the compression surfaces of hypersonic inlets.The flow exiting a scramjet inlet must remain supersonic.

An inlet must operate efficiently over the entire flight envelopeof the aircraft. At very low aircraft speeds, or when just sitting onthe runway, free stream air is pulled into the engine by thecompressor. In England, inlets are called intakes, which is amore accurate description of their function at low aircraft speeds.At high speeds, a good inlet will allow the aircraft to maneuver tohighangles of attackand sideslip without disrupting flow to thecompressor. Because the inlet is so important to overall aircraftoperation, it is usually designed and tested by the airframe company,not the engine manufacturer. But because inlet operation is soimportant to engine performance, all engine manufacturers also employinlet aerodynamicists.The amount of disruption of the flow is characterized by a numericalinlet distortion index. Different airframers usedifferent indices, but all of the indices are based on ratios of thelocal variation of pressure to the average pressure at the compressor face.

The ratio of the average total pressure at the compressor face to thefree stream total pressure is called thetotal pressure recovery. Pressure recovery is another inlet performanceindex; the higher the value, the better the inlet. For hypersonic inletsthe value of pressure recovery is very low and nearly constant because of shock losses, so hypersonic inlets arenormally characterized by their kinetic energy efficiency.If the airflow demanded by the engine is much less than the airflowthat can be captured by the inlet, then the difference in airflow isspilled around the inlet. The airflow mis-match can produce spillagedrag on the aircraft.

The Cessna Citation X is an American business jet produced by Cessna that made its maiden flight in 1993. The Citation X was the first aircraft from Cessna to use a Rolls-Royce engine and fully integrated avionics.

In Chapter 3 we represented a gasturbine engine using a Brayton cycle and derived expressions forefficiency and work as functions of the temperature at variouspoints in the cycle. In this section we will perform further idealcycle analysis to express the thrust and fuel efficiency of enginesin terms of useful design variables, including design limits, flightconditions, and design choices.The expressions we develop will allow us to define a particularmission and then determine the optimum component characteristics(e.g. compressor, combustor, turbine) for an engine for a givenmission. Note that ideal cycle analysis addresses only thethermodynamics of the airflow within the engine. It does notdescribe the details of the components (the blading, the rotationalspeed, etc.), but only the results the various components produce(e.g. pressure ratios, temperature ratios). InChapter 12 we will look in greater detail athow some of the components (the turbine and the compressor) producethese effects.11.6.1 Notation and station numberingNotation:

New research shows that condensation trails from aircraft exhaust are playing a significant role in global warming. Experts are concerned that efforts to change aviation engine design to reduce CO2 emissions could actually create more contrails and raise daily temperatures even more.

Contrails are human-made clouds. They form in air above about 25,000 feet, when that air is moist and colder than -40 degrees Celsius. Like regular clouds, they arise when water vapor, in this case from the engine exhausts, forms into droplets by condensing onto particles in the air, in this case soot from the engines. Within a second, the water droplets freeze to make tiny ice crystals that show up visually as contrails.

There is potentially a third approach: changing engine design to generate more propulsive energy from a given fuel burn. This is already an overriding priority of aviation engineers seeking to cut costs, and it would also reduce CO2 emissions. But there is problem as regards contrails, say Bock and Burkhardt.

Up to this point consideration has been given only to the design point of the engine. This is clearly not adequate for a variety of reasons. Engines sometimes have to give less than their maximum thrust to make the aircraft controllable and to maintain an adequate life for the components. Furthermore all engines have to be started, and this requires the engine to accelerate from very low speeds achieved by the starter motor. The inlet temperature and pressure vary with altitude, climate, weather and forward speed and this needs to be allowed for. 2b1af7f3a8