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1、航空工程學(xué)院 航空發(fā)動(dòng)機(jī)綜合課程設(shè)計(jì)航空發(fā)動(dòng)機(jī)綜合課程設(shè)計(jì) no light up during start 題 目 cfm56-5ccfm56-5c 發(fā)動(dòng)機(jī)啟動(dòng)不點(diǎn)火發(fā)動(dòng)機(jī)啟動(dòng)不點(diǎn)火 作者姓名賈嵩松 專業(yè)名稱熱能與動(dòng)力工程 指導(dǎo)教師尚永鋒 提交日期 答辯日期 contents chapter 1 general.1 1.1 overview of the cfm56-5c turbofan engine.1 1.2 the technology behind the cfm56-5c turbofan engine .2 1.3 the subject of this article.2 c

2、hapter 2 fadec control system.4 2.1 fadec system introduction.4 2.1.1 fadec purpose.4 2.1.2 fadec component .4 2.2 electronic control unit.4 2.2.1 ecu distribution.4 2.2.2 ecu power supply.4 2.3 hydro-mechanical unit (hmu).5 2.3.1 hmu introduction.5 2.3.2 hmu function.5 2.3.3 schematic diagram of hm

3、u .6 2.4 process of fadec control.7 2.4.1 working process.7 2.4.2 function diagram of the fadec.8 2.4.3 abnormal work.8 chapter 3 ignition system.10 3.1 general description.10 3.2 ignition system distribution .10 3.2.1 electrical power.10 3.2.2 ignition exciter.11 3.2.3 ignition leads.12 3.2.4 spark

4、 igniter.12 3.3 ignition system control.13 3.3.1 the process of ignition.13 3.3.2 the control switch.14 3.4 principle diagram of the ignition.15 3.4.1 working process.15 3.4.2 function diagram of the ignition system.15 3.4.3 abnormal work.16 3.4 fuel nozzle.16 chapter 4 fault analysis.18 4.1 fault a

5、nalysis.18 4.1.1 fault description.18 4.1.2 analysis of failure causes.18 4.1.3 fault tree .18 4.2 process of trouble shooting.19 reference.21 appendix.22 abbreviations egt: exhaust gas temperature ecu: electronic control unit hmu: hydro-mechanical unit fadec: full authority digital engine control p

6、mc: power management control acc: active clearance control adiru: air data/inertial reference unit eivmu: engine interface and vibration monitoring unit vsv: variable stator vane vbv: variable bleed valve hpt: high pressure turbine lpt: low pressure turbine lptcc: low pressure turbine case cooling h

7、ptcc: high pressure turbine case cooling racsb: rotor active clearance start bleed chapter 1 general 1.1 overview of the cfm56-5c turbofan engine the cfm56-5c, the most powerful engine in the cfm56 family, is the sole cost-effective propulsion system perfectly tailored for the long-range airbus a340

8、-200 and a340-300 aircraft (fig.1-1). fig.1-1 cfm56-5c in its class, the airbus a340/cfm56-5c offers the lowest noise signature in commercial service. supported at its entry into service in 1993 by the cfm56 familys more than 40 million engine flight hours of experience, the cfm56-5c has an excellen

9、t reliability ratea hallmark of the cfm56 family. other versions of the cfm56 are also in service on the a320, providing airlines that operate a320/a340 mixed fleets a valuable commonality benefit due to reduced inventories and spare parts levels. to maximize overall performance and profitability fo

10、r airlines, cfm offers the cfm56-5c as a total propulsion system: engine, nacelle, and exhaust systems. continuing the cfm56 engines excellent worldwide reputation, the cfm56-5c features innovative technologies, low fuel consumption, and the ability to meet all existing environmental requirements wi

11、th significant margins. 1.2 the technology behind the cfm56-5c turbofan engine tab.1-1 related parameter of the cfm56-5c engine model: cfm56 -5c2-5c3-5c4 max. thrust312003250034000 bypass ratio6.56.56.4 so we can obtain some related general data of the cfm-5c: max. thrust (lb): 31,200 - 34,000 max c

12、limb thrust (lb):73707580 max. cruise thrust (lb):69107100 bypass ratio: 6.5 overall pressure ratio at max climb: 37.438.3 length (in):103 fan diameter (in):72.3 basic dry weight (lb):8796 1.3 the subject of this article in the process of using the engine, generally, many troubles may be happened. i

13、n this article, we focus on discussing the one of the deviant starting: no light up of starting. this failure often occurs, when the starting of the engine. namely, after the starter start, within the specified time (10 seconds after the supplying of the fuel), if the egt or the indication of n2 not

14、 increase, it show that the engine is no light up. now we should close the switch of starting. by analyzing the information, we can obtain the main related component about this trouble: ecu, hmu, igniter-spark a and b. in this article, we will first introduce these components of this trouble, includ

15、ing their operating principle, some subsystem and their parts that may cause misfiring. then through these, we can obtain the fault tree of this trouble, and process or method of trouble shooting. chapter 2 fadec control system 2.1 fadec system introduction 2.1.1 fadec purpose the full authority dig

16、ital engine control (fadec) provides full range engine control to achieve steady state and transient engine performances when operated in combination with aircraft subsystems. fadec can take complete control of engine systems in response to command inputs from the aircraft. it also provides informat

17、ion to the aircraft for flight deck indications, engine condition monitoring, maintenance reporting and trouble-shooting. the purposes of fadec follow: (a) power management control (pmc) (b) starting/shutdown ignition control (c) fuel control (d) active clearance control (acc) (e) variable geometry

18、control (f) thrust reverser 2.1.2 fadec component the fadec system consists of: -an electronic control unit (ecu) containing two identical computers, designated channel a and channel b. the ecu electrically performs engine control calculation and monitors the engines condition. -a hydro-mechanical u

19、nit (hmu), which converts electrical signals from the ecu into hydraulic pressures to drive the engines valves and actuators. -peripheral components such as valves, actuators and sensors used for control and monitoring. refer to fig.2-1.fadec component fig.2-1.fadec component 2.2 electronic control

20、unit 2.2.1 ecu distribution the electronic control unit (ecu) is a dual channel digital electronic control with each channel utilizing a microprocessor for main control functions, a microcontroller for pressure transducer interface functions and a microcontroller for arinc communication function. th

21、e ecu is a vibration-isolated single unit mounted on the fan case. refer to fig.2-2. electronic control unit the functions of ecu follow: (a) each ecu channel receives data buses from two air data and inertial reference units (adiru) and operational commands from the engine interface vibration monit

22、oring unit (eivmu) in the aircraft on arinc 429 data busses. (b) it also receives operating condition data from the various dedicated engine sensors such as t12, ps12, p0, n1, n2, ps3, t/p25, t3 and tc, and computes the necessary fuel flow, vsv, vbv, hpt clearance control, lpt clearance control, rot

23、or active clearance control valve (only applicable for cfm56-5c) and transient bleed valve (only applicable for cfm56-5c/p) positions. fig.2-2 electronic control unit (c) the ecu provides the necessary current to the torque motors in the hydro-mechanical unit to control the various modulating valves

24、 and actuators. (d) the ecu performs an on/off control of the ignition relays, starter air valve solenoid, the aircraft thrust reverser directional valve and the thrust reverser pressurizing valve. 2.2.2 ecu power supply the ecu provides digital data output in arinc 429 format to the aircraft for en

25、gine parameter display, aircraft flight management system and the aircraft maintenance data system. so the ecu is powered by a three-phase engine alternator. two independent coils from the alternator provide the power to the two separate ecu channels. a logic circuit within the ecu, automatically se

26、lects the correct power source: -a/c power supply. the power sources are the 115v-400hz ac transfer busses 1and 2 - control alternator. the control alternator provides two separate power sources from two independent windings. one is hardwired to channel a, the other to channel b. the alternator is c

27、apable of supplying the necessary power above an engine speed of approximately 15% n2. refer to fig.2-3 ecu power supply ecu a/c 115v ac 400hz control alternator chan a and bchan a and b fig.2-3 ecu power supply 2.3 hydro-mechanical unit (hmu) 2.3.1 hmu introduction the hydro-mechanical unit (hmu) i

28、s attached to the aft section of the fuel pump unit housing. the two units make a bigger unit, or package. this package is installed on the aft side of the agb, at the left side of the horizontal drive shaft housing. refer to fig.2-4.hydro-mechanical unit. fig.2-4.hydro-mechanical unit 2.3.2 hmu fun

29、ction the hmu has different functions: it provides internal calibration of fuel pressures. it meters the fuel flow for combustion. it provides the fuel shut-off and fuel manifold minimum pressurization levels. it bypasses unused fuel. it provides mechanical n2 over-speed protection. it delivers the

30、correct hydraulic power source to various engine fuel equipments. refer to fig.2-5.hmu purposes. hmu fuel pressures calibration metered fuel flow for combustion -fuel shut-off -fuel manifold pressurization excess fuel flow bypass mechanical n2 over-speed protection fuel equipment power source supply

31、 chan a and b fig.2-5.hmu purposes 2.3.3 schematic diagram of hmu a general schematic of the hmu is shown in the referenced illustration. fig.2-6. schematic diagram of hmu 1. fuel metering the fuel metering valve is hydraulically driven through a torque motor/servo valve by the ecu. the torque motor

32、 contains two electrically isolated, independent coils, one dedicated to channel a, the other to channel b of the ecu. a differential pressure regulating valve maintains a constant pressure drop across the metering valve. as a result, fuel flow varies proportionally with metering valve position. two

33、 fuel metering valve position resolvers, one dedicated to each channel in the ecu, produce an electrical feedback signal in proportion to fuel metering valve position. the ecu uses this signal to compute the current required at the fuel metering valve torque motor for achieving closed loop electrica

34、l control. fig.2-6. schematic diagram of hmu 2. motive flow modulation the hmu contains 5 additional torque motors/pilot valves that modulate hydraulic signals to the following: -low pressure turbine clearance control valve (lptcc) -high pressure turbine clearance control valve (hptcc) -rotor active

35、 clearance control system (racsb) -transient bleed system -variable stator vane actuators (vsv) -variable bleed valve actuators (vbv) each torque motor contains two electrically isolated, independent coils. one is dedicated to channel a, the other to channel b, of the ecu. they provide flow and pres

36、sure at an hmu pressure port in response to electrical commands from the ecu. 3. fuel shut-off valve the fuel shut-off valve shuts off fuel flow to the engine in response to an aircraft supplied electrical signal (28vdc) commanded by the eng/master switch. it has to be noted that the shut-off signal

37、 of the hp fuel shut-off valve also closes the lp fuel valve. 2.4 process of fadec control 2.4.1 working process according to normal start programs, when the pilot press start switch, ecu through torque motor/servo valve drive hydraulically the fuel metering valve, including chan a and chan b. at th

38、e same time, a differential pressure regulating valve maintains a constant pressure drop across the metering valve, so that fuel flow varies proportionally with metering valve position. there are two resolvers that produce an electrical feedback signal in proportion to fuel metering valve position.

39、then the ecu uses this signal to compute the current required at the fuel metering valve torque motor for achieving closed loop electrical control. refer to fig.2- 7.working process. torque motor/servo valve resolvers ecu chan a and b hmu fmv fuel pump fuel manifolds p regulating valve and bypass va

40、lve adjustment proportional to the piston position fig.2-7. working process 2.4.2 function diagram of the fadec according to the subsystem and working process of the fadec, we can obtain the function diagram of the fadec. refer to fig.2-8. from it we can understand the function of fadec. fadec ecu h

41、mu peripheral components fmv p regulating valve pressurizing and shut-off valve valveactuatorsensor electrical connector ecu cooling system ignition system tm r shut-off solenoid control fig.2-8. function diagram of the fadec 2.4.3 abnormal work when light up during start, if egt and n2 display does

42、 not increase, and the same time the flow indication also not increase, the engine will be ignition failure. this failure is called no light up during start. the process of ignition is controlled by ecu and hmu in fadec. so we can find possible causes in them. the ecu controls mainly the power suppl

43、y in ignition. if no light up occurs, we can guess that the ignition voltage may be below 24kv. or the fuel nozzle emerges poor fuel or rich fuel conditions. no light up during start ecu ignition voltage below hmu fuel supply abnormal ecu failure lead plug loose fmv failure torque motor/servo valve

44、failure resolver failure pressurizing valve and shut-off solenoid fig.2-9.possible failure parts in fig.2-9 possible failure parts, we show the some components that may cause the ecus and hmus abnormal working based on the reasons of the possible. from it the maintenance personnel can find the relat

45、ed components to shoot the trouble. chapter 3 ignition system 3.1 general description the ignition system consists of two independent systems a and b. each system is equipped with: -one ignition exciter, the exercitation of which is controlled by the ecu, either channel a or b of the ecu. -one spark

46、 igniter -one coaxial shielded ignition lead. a. ignition exciters the 2 ignition exciters are installed on shock dampened brackets on the outer surface of the fan case. each exciter has an input connector and an output connector. b. spark igniters the 2 spark igniters are installed into bosses at t

47、he 4 and 8 oclock positions on the outer surface of the combustion case. the inner tip extends, through ferrules, into the outer liner of the combustion chamber. c. ignition leads the ignition leads are constructed of insulated wire in a sealed flexible conduit having a copper inner braid and a nick

48、el outer braid. the leads connect the spark igniters to the ignition exciters. the aft ends of the leads, from the tube bundle junction box to the spark igniters, are cooled by fan discharge air passing through the lead conduit. fig.3-1.ignition system location the ignition system requires 115v, 400

49、hz from the electrical system via the ecu. the ecu controls the operation of ignition exciters a and b. the ignition for each engine is performed by one or both exciter(s) which transform(s) the 115v-400hz power supply into high voltage pulsating current. the high voltage flows through the ignition

50、lead (shielded and ventilated) and delivers to the spark igniter the power required to ignite the fuel/air mixture by a series of sparks. the purpose of the system is: -to produce an electrical spark to ignite the fuel/air mixture in the engine combustion chamber during the starting cycle on ground

51、and in flight -to provide continuous ignition in the following cases: (a) when manually selected. (b) auto-matically when engine flame out is detected. 3.2 ignition system distribution the ignition system enables three functions: -the electrical power supply -the distribution -the switching 3.2.1 el

52、ectrical power the ignition system requires 115v, 400hz from the electrical system via the ecu. the ecu controls the operation of ignition exciters a and b. the ignition exciters transform the 115v, 400hz into 20kv high voltage pulsating current. fig.3-2. electrical power aircraft upper ignition exc

53、iter lower ignition exciter 115v-400hz ac 115v-400hz ac fig.3-2. electrical power 3.2.2 ignition exciter the two ignition exciters are installed on the inlet fan case with resilient shock mounts at the 3 oclock position. a tin plated aluminum housing encloses each exciter. the components are secured

54、 to the housing mechanically or with silicone cement to protect them from vibration damage. the housing is sealed to ensure proper operation under varying environmental conditions. each ignition exciter has: -one ignition lead connector -one electrical input connector. fig.3-2. ignition exciter fig.

55、3-2. ignition exciter 3.2.3 ignition leads an ignition lead transmits electrical energy from an ignition exciter to a spark igniter. each lead consists of a 0.28 in. (7 mm) diameter silicone insulated cable containing a no. 14 awg nickel plated copper stranded conductor. the 0.28 in. (7 mm) cable is

56、 housed within a flexible conduit which features a nickel plated copper inner braid, a nickel-iron convoluted conduit, and a nickel outer braid. fan discharge air is introduced into an enlarged diameter portion of each ignition lead conduit for cooling of the silicone insulated cable and igniter con

57、nection. refer to fig.3-3. ignition lead fig.3-3. ignition lead 3.2.4 spark igniter there are 2 spark igniters in bosses at the 4 and 8 oclock positions, looking forward, on the combustion case assembly. the tip of the spark igniters extends, through ferrules, into the outer liner into the combustio

58、n chamber. each spark igniter is connected by a lead to an ignition exciter. the ignition exciter sends electrical energy to the spark igniter. the spark igniter supplies the spark necessary for ignition of the fuel/air mixture in the combustor. fig.3-4. ignition leads and left/right spark - ignitio

59、n fig.3-4. ignition leads and left/right spark ignition 3.3 ignition system control 3.3.1 the process of ignition the engine is fitted with a dual ignition system. each system has an ignition exciter unit connected to its own spark igniter. depending on the operating mode, one or both circuit(s) is

60、(are) selected by the ecu. the ignition exciter is of the capacitor discharge type. it requires an 115vac, 400hz input current from the ecu. the output voltage is about 20kv at the end of the ignition lead. the ignition exciter consists of: -one input circuit (input filter and power transformer) -on

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