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Revision sheets of the POWERPLANT module, in English, made with courses and AE data bank. Achieved more than 90% success
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ATPL (A)Review Worksheets
021 POWERPLANT
BY KDMN
2020
, TURBINE
I/ GAS TURBINE GENERAL PRINCIPLES
• The operation of the gas turbine uses action-reaction principle according to Newton’s third law.
• Thrust F = Q x (Vexit – Ventry).
01 CYCLE & COMPONENTS
• It relies on thermodynamic cycle, 4 strokes: Intake/supply, Compression, Combustion &
Expansion/ejection.
• Cycle transformation:
Divergente Convergente
Shape Shape
BRAYTON’s cycle
STATIC P
AXIAL SPEED
STATIC TEMP
Because of the diffuser
02 FORUMLAS
CONSUMPTION
Hourly cons (kg/h) Ch = 3600 Qc
Specific cons Csp = Ch / FN
POWER – SINGLE FLOW – TURBOJET
Calorific power Cp = Qc x Ncv (calorific value of kerosene = 44.106 J/kg
Theoretical thermal power Ttp = CP – Qa Cair (T6- T0), Cair = 1000J/kg/°C
Thermal power Pth = Pdyn = ½ Qa(V6²-V0²)
Dynamic power
Propulsion power Pp=Up=FN x V0
Useful power Fn= Qa(V6-V0) + QcV6 + S6(Ps6-P0)
EFFICIENCIES
theoretical thermal efficiency ⴄtt = Ttp/Cp
Internal efficiency ⴄI=Pth/Ttp = Pdyn/Ttp
External efficiency ⴄth= Pth/Cp = Pdyn/Cp
Propulsion efficiency ⴄp=Pp/Pth = Up/Pth = 2V0/(V6 +V0)
Overall efficiency ⴄG=Pp / Cp= Up/Cp= ⴄtt x ⴄI x ⴄp = 3600V0/CspNcv
, Cp
External ⴄtt
losses
Ttp ⴄt
ⴄG Internal ⴄI h
losses
Pth = Pdyn
Propulsive ⴄp
losses
P p = Up
POWER – DUAL FLOW- TURBOJET
Same
Theoretical thermal power Ttp=Cp – (Qa1Cair(T1s-T0)+Qa2Cair(T2s-T0)
Thermal power Pth= ½ Qa2(V2s²-V0²) + ½ Qa1(V1s²+V0²)~ ½ Qa(Veq²-V0²)
Same
POWER TURBOPROP
Calorific power Cp= QcNcv
Mechanical power Pm= Cx2pi+Nh/60, Nh t/min of the propeller
Total equivalent power Pteq= Pm + Pgaz= Pm + Fresidual.V0
Useful power/ propulsion power Pp=T.V0 =Pteq. ⴄh
Specific power Psp=Pteq/Qa
Propulsion efficiency ⴄh=Pu/Pteq
Overall efficiency ⴄg=Pu/Cp
03 TYPES OF GAS TURBINES
a) SINGLE FLOW TURBOJET, SINGLE COUPLING: after WW2, one turbines driving the compressor +
accessory box (hydraulic pump + oil pump + fuel pump + electric alternator). One air flow to create
thrust. Used for the APU
b) SINGLE FLOW TURBOJET, DOUBLE COUPLING: one HP turbine-compressor & one LP turbine-
compressor, 2 independent parts.
c) DUAL FLOW TURBOJET: less noise, less consumption, more efficient.
➔ One primary flow subjected to the compression, combustion & expansion cycle
➔ One secondary flow, which will not bunt with fuel. The static pressure increased by the large-
diameter compressor, called fan or blower, is sufficient to allow expansion and acceleration
by means of an ejection channel. It produces 80% of the thrust, decreasing to 50-60% in cruise.
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