1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3 Module: FGPropeller.cpp
6 Purpose: Encapsulates the propeller object
8 ------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.org) -------------
10 This program is free software; you can redistribute it and/or modify it under
11 the terms of the GNU General Public License as published by the Free Software
12 Foundation; either version 2 of the License, or (at your option) any later
15 This program is distributed in the hope that it will be useful, but WITHOUT
16 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
20 You should have received a copy of the GNU General Public License along with
21 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
22 Place - Suite 330, Boston, MA 02111-1307, USA.
24 Further information about the GNU General Public License can also be found on
25 the world wide web at http://www.gnu.org.
27 FUNCTIONAL DESCRIPTION
28 --------------------------------------------------------------------------------
31 --------------------------------------------------------------------------------
34 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
38 #include "FGPropeller.h"
40 static const char *IdSrc = "$Id$";
41 static const char *IdHdr = ID_PROPELLER;
43 extern short debug_lvl;
45 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
47 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
50 FGPropeller::FGPropeller(FGFDMExec* exec, FGConfigFile* Prop_cfg) : FGThruster(exec)
55 Name = Prop_cfg->GetValue("NAME");
56 cout << "\n Propeller Name: " << Name << endl;
57 Prop_cfg->GetNextConfigLine();
58 while (Prop_cfg->GetValue() != "/FG_PROPELLER") {
62 cout << " IXX = " << Ixx << endl;
63 } else if (token == "DIAMETER") {
64 *Prop_cfg >> Diameter;
66 cout << " Diameter = " << Diameter << " ft." << endl;
67 } else if (token == "NUMBLADES") {
68 *Prop_cfg >> numBlades;
69 cout << " Number of Blades = " << numBlades << endl;
70 } else if (token == "EFFICIENCY") {
71 *Prop_cfg >> rows >> cols;
72 if (cols == 1) Efficiency = new FGTable(rows);
73 else Efficiency = new FGTable(rows, cols);
74 *Efficiency << *Prop_cfg;
75 cout << " Efficiency: " << endl;
77 } else if (token == "C_THRUST") {
78 *Prop_cfg >> rows >> cols;
79 if (cols == 1) cThrust = new FGTable(rows);
80 else cThrust = new FGTable(rows, cols);
81 *cThrust << *Prop_cfg;
82 cout << " Thrust Coefficient: " << endl;
84 } else if (token == "C_POWER") {
85 *Prop_cfg >> rows >> cols;
86 if (cols == 1) cPower = new FGTable(rows);
87 else cPower = new FGTable(rows, cols);
89 cout << " Power Coefficient: " << endl;
91 } else if (token == "EOF") {
92 cout << " End of file reached" << endl;
95 cout << "Unhandled token in Propeller config file: " << token << endl;
102 if (debug_lvl & 2) cout << "Instantiated: FGPropeller" << endl;
105 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
107 FGPropeller::~FGPropeller()
109 if (Efficiency) delete Efficiency;
110 if (cThrust) delete cThrust;
111 if (cPower) delete cPower;
112 if (debug_lvl & 2) cout << "Destroyed: FGPropeller" << endl;
115 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
117 // We must be getting the aerodynamic velocity here, NOT the inertial velocity.
118 // We need the velocity with respect to the wind.
120 // Note that PowerAvailable is the excess power available after the drag of the
121 // propeller has been subtracted. At equilibrium, PowerAvailable will be zero -
122 // indicating that the propeller will not accelerate or decelerate.
123 // Remembering that Torque * omega = Power, we can derive the torque on the
124 // propeller and its acceleration to give a new RPM. The current RPM will be
125 // used to calculate thrust.
127 // Because RPM could be zero, we need to be creative about what RPM is stated as.
129 float FGPropeller::Calculate(float PowerAvailable)
131 float J, C_Thrust, omega;
132 float Vel = (fdmex->GetTranslation()->GetUVW())(1);
133 float rho = fdmex->GetAtmosphere()->GetDensity();
134 float RPS = RPM/60.0;
137 J = Vel / (Diameter * RPM / 60.0);
142 if (MaxPitch == MinPitch) { // Fixed pitch prop
143 C_Thrust = cThrust->GetValue(J);
144 } else { // Variable pitch prop
145 C_Thrust = cThrust->GetValue(J, Pitch);
148 Thrust = C_Thrust*RPS*RPS*Diameter*Diameter*Diameter*Diameter*rho;
150 omega = RPS*2.0*M_PI;
152 if (omega <= 5) omega = 1.0;
154 Torque = PowerAvailable / omega;
155 RPM = (RPS + ((Torque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
156 return Thrust; // return thrust in pounds
159 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
161 float FGPropeller::GetPowerRequired(void)
163 if (RPM <= 0.10) return 0.0; // If the prop ain't turnin', the fuel ain't burnin'.
165 float cPReq, RPS = RPM / 60.0;
167 float J = (fdmex->GetTranslation()->GetUVW())(1) / (Diameter * RPS);
168 float rho = fdmex->GetAtmosphere()->GetDensity();
170 if (MaxPitch == MinPitch) { // Fixed pitch prop
171 cPReq = cPower->GetValue(J);
172 } else { // Variable pitch prop
173 cPReq = cPower->GetValue(J, Pitch);
176 PowerRequired = cPReq*RPS*RPS*RPS*Diameter*Diameter*Diameter*Diameter
178 return PowerRequired;
181 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
183 void FGPropeller::Debug(void)
185 //TODO: Add your source code here