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140 Referred Parameter Turboshaft Engine Model The engine technology parameters SP0C and sfc0C are assumed to vary linearly with mass flow ˙m0C up to a limit ˙mlim, and constant thereafter at SPlim and sfclim. The mass flow at the reference condition is ˙mref = Pref/SPref, with the reference values SPref and sfcref. The functions are defined by the limit values, and by the intercept values SPzero and sfczero at ˙m0C =0. If ˙mref ≥ ˙mlim, the limit values are set to the reference values. If ˙mref < ˙mlim, the intercept values are projected from the reference values: SPzero = SPref − ˙mrefx, x =(SPlim − SPref)/( ˙mlim − ˙mref); and similarly for sfczero. Then for ˙m0C < ˙mlim and for ˙m0C ≥ ˙mlim SP0C = SPzero + Ksp1 ˙m0C = Ksp0 + Ksp1 ˙m0C sfc0C = sfczero + Ksfc1 ˙m0C = Ksfc0 + Ksfc1 ˙m0C SP0C = SPlim sfc0C = sfclim From the limit and intercept values, the slopes are Ksp1 =(SPlim − SPzero)/ ˙mlim and Ksfc1 = (sfclim − sfczero)/ ˙mlim. Usually the effect of size gives Ksp2 ≥ 0 and Ksfc2 ≤ 0. The power at the limit is Plim = SPlim ˙mlim. Using ˙m0C = P0C/SP0C, the specific power equation can be solved for the mass flow given the power: ˙m0C = ⎧ ⎨ ⎩ P0C/SPlim ( K0 2K1 )2 + P0C K0 − K1 2K1 P0C ≥ Plim or Ksp1 =0 otherwise From this mass flow, SP0C and sfc0C are calculated, hence the fuel flow ˙w0C = sfc0CP0C. The specific thrust available at MCP is assumed to be constant, and the specification power turbine speed decreases with the mass flow: Fg0C = SF0C ˙m0C Nspec = Nopt0C = Nspec Nspec − KNs2/ ˙m0C Nopt0C Nspec ref ref + KNs2/ ˙m0C = KNs1 + KNs2/ ˙m0C Then the power and specific power at all ratings R are obtained from the ratios: P0R = rp0RP0C, SP0R = rs0RSP0C, PmechR = rm0RP0C. 18–9 Engine Speed The model as described in the previous sections may not adequately account for variation of engine performance with engine speed, so it is also possible to define the parameters corresponding to a set of engine-speed ratios r = N/Nspec. Then the engine-performance and power-available quantities are linearly interpolated to obtain the values at the required engine speed N. If this option is used, then the correction based on P (N)/P (Nspec) =ηt(N)/ηt(Nspec) is not applied. 18–10 Weight The engine weight can be a fixed input value, calculated as a function of power, or scaled with engine mass flow. As a function of power, the weight of one engine is: Wone eng = K0eng + K1engP + K2engP Xeng
Referred Parameter Turboshaft Engine Model 141 where P is the installed takeoff power (SLS static, specified rating) per engine. A constant weight per power W/P is given by using only K1eng. Alternatively, the specific weight SW = P/W can be scaled with the mass flow ˙m0C. The scaling is determined from the specific weight SWref at the reference mass flow ˙mref; and either the limit SWlim at ˙mlim (for ˙mref < ˙mlim) or the intercept SWzero at ˙m =0(for ˙mref ≥ ˙mlim). Then SW = and Wone eng = P/SW. SWzero + Ksw1 ˙m0C = Ksw0 + Ksw1 ˙m0C SWlim 18–11 Units ˙m0C < ˙mlim ˙m0C ≥ ˙mlim In this engine model, only the reference values and scaling constants are dimensional. Conventional English units and SI units are shown in table 18-2. Units of specific power and specific fuel consumption follow from these conventions. Table 18-2. Conventional units. power P mass flow ˙m fuel flow ˙w force F turbine speed N English: horsepower pound/sec pound/hour pound rpm SI: kiloWatt kilogram/sec kilogram/hour Newton rpm 18–12 Typical Parameters Typical values of the principal parameters describing the engine and its performance are given in table 18-3 for several generic engine sizes. These values represent good current technology. Advanced technology can be introduced by reducing the specific fuel consumption and weight, and increasing the specific power. Typical ratios of the power, specific power, and mass flow to the values at MCP are given in table 18-4 for several ratings. Figure 18-1 shows typical performance characteristics: fuel flow ˙w, mass flow ˙m, and net jet thrust Fg variation with power P and speed (referred quantities, normalized, at Nspec). Figure 18-2 shows typical variation of the power available with engine-turbine speed. Figures 18-3 to 18-8 show typical power-available characteristics: specific power SP, mass flow ˙m, and power P variation with temperature ratio θ, for static and 200 knots conditions and several engine ratings (referred quantities, normalized, at Nspec).
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NASA/TP-2009-215402 NDARC NASA Desi
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NASA/TP-2009-215402 NDARC NASA Desi
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TABLE OF CONTENTS CHAPTER 1 - INTRO
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TABLE OF CONTENTS (cont.) CHAPTER 1
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viii LIST OF FIGURES (cont.) Figure
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Chapter 1 Introduction The NASA Des
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Introduction 3 of rotorcraft config
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Introduction 5 previous case DESIGN
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Introduction 7 4) Scully, M.; and F
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Chapter 2 Nomenclature The nomencla
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Nomenclature 11 Fuel Tanks Power Na
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Nomenclature 13 Motion aF AC aircra
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Chapter 3 Tasks The NDARC code perf
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Tasks 17 engine group is found (inc
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Tasks 19 3-4 Maps 3-4.1 Engine Perf
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Chapter 4 Operation 4-1 Flight Cond
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Operation 23 e) Input payload weigh
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Operation 25 Table 4-1. Mission seg
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Operation 27 horizontal ground dist
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Operation 29 climb for zero power m
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Operation 31 a) Horizontal velocity
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Operation 33 From the pressure p =
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Chapter 5 Solution Procedures The N
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Solution Procedures 37 Sizing Task
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Solution Procedures 39 relaxation i
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Solution Procedures 41 Table 5-4. T
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Solution Procedures 43 successive s
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Solution Procedures 45 initialize e
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Chapter 6 Cost Costs are estimated
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Cost 49 Table 6-1. DoD and CPI infl
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Cost 51 predicted base price (1994$
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Chapter 7 Aircraft The aircraft con
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Aircraft 55 The tilt control variab
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Aircraft 57 forward axes for descri
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Aircraft 59 For steady-state flight
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Aircraft 61 where Δz F = z F − z
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Aircraft 63 disk area); or the drag
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Aircraft 65 7-10 Performance Indice
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Aircraft 67 WEIGHT EMPTY STRUCTURE
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Chapter 8 Systems The systems compo
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Chapter 9 Fuselage There is one fus
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Fuselage 73 αe = αfus − αzl, w
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Chapter 10 Landing Gear There is on
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Chapter 11 Rotor The aircraft can h
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Rotor 79 propulsion group. The driv
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Rotor 81 plane command. The collect
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Rotor 83 or just CSF = WCHF with no
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Rotor 85 If μ is zero, the equatio
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Rotor 87 The velocity ratio is fW =
Page 101 and 102: Rotor 89 T/T ∞ 1.3 1.2 1.1 1.0 Ha
Page 103 and 104: Rotor 91 TPP tilt / cyclic magnitud
Page 105 and 106: Rotor 93 with an average over the r
Page 107 and 108: Rotor 95 (all equal to 1 for μz =0
Page 109 and 110: Rotor 97 κ 1.30 1.25 1.20 1.15 1.1
Page 111 and 112: Rotor 99 (C T /σ) s c d mean 0.20
Page 113 and 114: Rotor 101 11-5.1.3 Twin Rotors For
Page 115 and 116: Rotor 103 The wake is a skewed cyli
Page 117 and 118: Rotor 105 weight per lifting rotor;
Page 119 and 120: Chapter 12 Force The force componen
Page 121 and 122: Chapter 13 Wing The aircraft can ha
Page 123 and 124: Wing 111 denotes outboard edge, sub
Page 125 and 126: Wing 113 13-3.1 Lift The wing lift
Page 127 and 128: Wing 115 The wing interference at t
Page 129 and 130: Chapter 14 Empennage The aircraft c
Page 131 and 132: Empennage 119 14-4 Weights The tail
Page 133 and 134: Chapter 15 Fuel Tank 15-1 Fuel Capa
Page 135 and 136: Fuel Tank 123 if Wfuel >Wfuel−max
Page 137 and 138: Chapter 16 Propulsion The propulsio
Page 139 and 140: Propulsion 127 If the sum of the fi
Page 141 and 142: Chapter 17 Engine Group The engine
Page 143 and 144: Engine Group 131 The engine group p
Page 145 and 146: Engine Group 133 specific fuel cons
Page 147 and 148: Chapter 18 Referred Parameter Turbo
Page 149 and 150: Referred Parameter Turboshaft Engin
Page 151: Referred Parameter Turboshaft Engin
Page 159 and 160: Chapter 19 AFDD Weight Models This
Page 161 and 162: AFDD Weight Models 149 The spar-cap
Page 163 and 164: AFDD Weight Models 151 19-1.2 Aircr
Page 165 and 166: AFDD Weight Models 153 where w = nz
Page 167 and 168: AFDD Weight Models 155 units as use
Page 169 and 170: AFDD Weight Models 157 Table 19-9.
Page 171 and 172: AFDD Weight Models 159 where fP = f
Page 173 and 174: AFDD Weight Models 161 The conversi
Page 175 and 176: AFDD Weight Models 163 19-12 Foldin
Page 177 and 178: AFDD Weight Models 165 error (%) er
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