Date started: 08/24/00
Purpose: Encapsulates the propeller object
- ------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.org) -------------
+ ------------- Copyright (C) 2000 Jon S. Berndt (jon@jsbsim.org) -------------
This program is free software; you can redistribute it and/or modify it under
- the terms of the GNU General Public License as published by the Free Software
+ the terms of the GNU Lesser General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
details.
- You should have received a copy of the GNU General Public License along with
+ You should have received a copy of the GNU Lesser General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA.
- Further information about the GNU General Public License can also be found on
+ Further information about the GNU Lesser General Public License can also be found on
the world wide web at http://www.gnu.org.
FUNCTIONAL DESCRIPTION
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+#include <iostream>
#include <sstream>
#include "FGPropeller.h"
-#include <models/FGPropagate.h>
-#include <models/FGAtmosphere.h>
-#include <models/FGAuxiliary.h>
+#include "input_output/FGXMLElement.h"
+
+using namespace std;
namespace JSBSim {
-static const char *IdSrc = "$Id$";
+static const char *IdSrc = "$Id: FGPropeller.cpp,v 1.44 2012/04/29 13:10:46 bcoconni Exp $";
static const char *IdHdr = ID_PROPELLER;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
: FGThruster(exec, prop_element, num)
{
string token;
- int rows, cols;
Element *table_element, *local_element;
string name="";
FGPropertyManager* PropertyManager = exec->GetPropertyManager();
Feathered = false;
Reverse_coef = 0.0;
GearRatio = 1.0;
+ CtFactor = CpFactor = 1.0;
+ ConstantSpeed = 0;
+ cThrust = cPower = CtMach = CpMach = 0;
+ Vinduced = 0.0;
if (prop_element->FindElement("ixx"))
Ixx = prop_element->FindElementValueAsNumberConvertTo("ixx", "SLUG*FT2");
MaxPitch = prop_element->FindElementValueAsNumber("maxpitch");
if (prop_element->FindElement("minrpm"))
MinRPM = prop_element->FindElementValueAsNumber("minrpm");
- if (prop_element->FindElement("maxrpm"))
+ if (prop_element->FindElement("maxrpm")) {
MaxRPM = prop_element->FindElementValueAsNumber("maxrpm");
+ ConstantSpeed = 1;
+ }
+ if (prop_element->FindElement("constspeed"))
+ ConstantSpeed = (int)prop_element->FindElementValueAsNumber("constspeed");
if (prop_element->FindElement("reversepitch"))
ReversePitch = prop_element->FindElementValueAsNumber("reversepitch");
- for (int i=0; i<2; i++) {
- table_element = prop_element->FindNextElement("table");
+ while((table_element = prop_element->FindNextElement("table")) != 0) {
name = table_element->GetAttributeValue("name");
- if (name == "C_THRUST") {
- cThrust = new FGTable(PropertyManager, table_element);
- } else if (name == "C_POWER") {
- cPower = new FGTable(PropertyManager, table_element);
- } else {
- cerr << "Unknown table type: " << name << " in propeller definition." << endl;
+ try {
+ if (name == "C_THRUST") {
+ cThrust = new FGTable(PropertyManager, table_element);
+ } else if (name == "C_POWER") {
+ cPower = new FGTable(PropertyManager, table_element);
+ } else if (name == "CT_MACH") {
+ CtMach = new FGTable(PropertyManager, table_element);
+ } else if (name == "CP_MACH") {
+ CpMach = new FGTable(PropertyManager, table_element);
+ } else {
+ cerr << "Unknown table type: " << name << " in propeller definition." << endl;
+ }
+ } catch (std::string str) {
+ throw("Error loading propeller table:" + name + ". " + str);
}
}
+ if( (cPower == 0) || (cThrust == 0)){
+ cerr << "Propeller configuration must contain C_THRUST and C_POWER tables!" << endl;
+ }
local_element = prop_element->GetParent()->FindElement("sense");
if (local_element) {
double Sense = local_element->GetDataAsNumber();
- SetSense(fabs(Sense)/Sense);
+ SetSense(Sense >= 0.0 ? 1.0 : -1.0);
}
local_element = prop_element->GetParent()->FindElement("p_factor");
if (local_element) {
P_Factor = local_element->GetDataAsNumber();
}
if (P_Factor < 0) {
- cerr << "P-Factor value in config file must be greater than zero" << endl;
+ cerr << "P-Factor value in propeller configuration file must be greater than zero" << endl;
}
+ if (prop_element->FindElement("ct_factor"))
+ SetCtFactor( prop_element->FindElementValueAsNumber("ct_factor") );
+ if (prop_element->FindElement("cp_factor"))
+ SetCpFactor( prop_element->FindElementValueAsNumber("cp_factor") );
Type = ttPropeller;
RPM = 0;
vTorque.InitMatrix();
D4 = Diameter*Diameter*Diameter*Diameter;
D5 = D4*Diameter;
-
- char property_name[80];
- snprintf(property_name, 80, "propulsion/engine[%d]/advance-ratio", EngineNum);
- PropertyManager->Tie( property_name, &J );
- snprintf(property_name, 80, "propulsion/engine[%d]/blade-angle", EngineNum);
- PropertyManager->Tie( property_name, &Pitch );
- snprintf(property_name, 80, "propulsion/engine[%d]/thrust-coefficient", EngineNum);
- PropertyManager->Tie( property_name, this, &FGPropeller::GetThrustCoefficient );
+ Pitch = MinPitch;
+
+ string property_name, base_property_name;
+ base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNum);
+ property_name = base_property_name + "/engine-rpm";
+ PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetEngineRPM );
+ property_name = base_property_name + "/advance-ratio";
+ PropertyManager->Tie( property_name.c_str(), &J );
+ property_name = base_property_name + "/blade-angle";
+ PropertyManager->Tie( property_name.c_str(), &Pitch );
+ property_name = base_property_name + "/thrust-coefficient";
+ PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetThrustCoefficient );
+ property_name = base_property_name + "/propeller-rpm";
+ PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetRPM );
+ property_name = base_property_name + "/helical-tip-Mach";
+ PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetHelicalTipMach );
+ property_name = base_property_name + "/constant-speed-mode";
+ PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetConstantSpeed,
+ &FGPropeller::SetConstantSpeed );
+ property_name = base_property_name + "/prop-induced-velocity_fps";
+ PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetInducedVelocity,
+ &FGPropeller::SetInducedVelocity );
Debug(0);
}
FGPropeller::~FGPropeller()
{
- if (cThrust) delete cThrust;
- if (cPower) delete cPower;
-
- char property_name[80];
- snprintf(property_name, 80, "propulsion/engine[%d]/advance-ratio", EngineNum);
- PropertyManager->Untie( property_name );
- snprintf(property_name, 80, "propulsion/engine[%d]/blade-angle", EngineNum);
- PropertyManager->Untie( property_name );
+ delete cThrust;
+ delete cPower;
+ delete CtMach;
+ delete CpMach;
Debug(1);
}
// We must be getting the aerodynamic velocity here, NOT the inertial velocity.
// We need the velocity with respect to the wind.
//
-// Note that PowerAvailable is the excess power available after the drag of the
-// propeller has been subtracted. At equilibrium, PowerAvailable will be zero -
-// indicating that the propeller will not accelerate or decelerate.
// Remembering that Torque * omega = Power, we can derive the torque on the
// propeller and its acceleration to give a new RPM. The current RPM will be
// used to calculate thrust.
//
// Because RPM could be zero, we need to be creative about what RPM is stated as.
-double FGPropeller::Calculate(double PowerAvailable)
+double FGPropeller::Calculate(double EnginePower)
{
- double omega, alpha, beta;
+ FGColumnVector3 localAeroVel = Transform().Transposed() * in.AeroUVW;
+ double omega, PowerAvailable;
- double Vel = fdmex->GetAuxiliary()->GetAeroUVW(eU);
- double rho = fdmex->GetAtmosphere()->GetDensity();
+ double Vel = localAeroVel(eU);
+ double rho = in.Density;
double RPS = RPM/60.0;
- if (RPS > 0.00) J = Vel / (Diameter * RPS); // Calculate J normally
- else J = 1000.0; // Set J to a high number
+ // Calculate helical tip Mach
+ double Area = 0.25*Diameter*Diameter*M_PI;
+ double Vtip = RPS * Diameter * M_PI;
+ HelicalTipMach = sqrt(Vtip*Vtip + Vel*Vel) / in.Soundspeed;
- if (MaxPitch == MinPitch) ThrustCoeff = cThrust->GetValue(J);
- else ThrustCoeff = cThrust->GetValue(J, Pitch);
+ PowerAvailable = EnginePower - GetPowerRequired();
- if (P_Factor > 0.0001) {
- alpha = fdmex->GetAuxiliary()->Getalpha();
- beta = fdmex->GetAuxiliary()->Getbeta();
- SetActingLocationY( GetLocationY() + P_Factor*alpha*Sense);
- SetActingLocationZ( GetLocationZ() + P_Factor*beta*Sense);
+ if (RPS > 0.0) J = Vel / (Diameter * RPS); // Calculate J normally
+ else J = Vel / Diameter;
+
+ if (MaxPitch == MinPitch) { // Fixed pitch prop
+ ThrustCoeff = cThrust->GetValue(J);
+ } else { // Variable pitch prop
+ ThrustCoeff = cThrust->GetValue(J, Pitch);
}
+ // Apply optional scaling factor to Ct (default value = 1)
+ ThrustCoeff *= CtFactor;
+
+ // Apply optional Mach effects from CT_MACH table
+ if (CtMach) ThrustCoeff *= CtMach->GetValue(HelicalTipMach);
+
Thrust = ThrustCoeff*RPS*RPS*D4*rho;
+
+ // Induced velocity in the propeller disk area. This formula is obtained
+ // from momentum theory - see B. W. McCormick, "Aerodynamics, Aeronautics,
+ // and Flight Mechanics" 1st edition, eqn. 6.15 (propeller analysis chapter).
+ // Since Thrust and Vel can both be negative we need to adjust this formula
+ // To handle sign (direction) separately from magnitude.
+ double Vel2sum = Vel*abs(Vel) + 2.0*Thrust/(rho*Area);
+
+ if( Vel2sum > 0.0)
+ Vinduced = 0.5 * (-Vel + sqrt(Vel2sum));
+ else
+ Vinduced = 0.5 * (-Vel - sqrt(-Vel2sum));
+
+ // We need to drop the case where the downstream velocity is opposite in
+ // direction to the aircraft velocity. For example, in such a case, the
+ // direction of the airflow on the tail would be opposite to the airflow on
+ // the wing tips. When such complicated airflows occur, the momentum theory
+ // breaks down and the formulas above are no longer applicable
+ // (see H. Glauert, "The Elements of Airfoil and Airscrew Theory",
+ // 2nd edition, ยง16.3, pp. 219-221)
+
+ if ((Vel+2.0*Vinduced)*Vel < 0.0)
+ Vinduced = 0.0; // We cannot calculate the induced velocity so let's assume it is zero.
+
+ // P-factor is simulated by a shift of the acting location of the thrust.
+ // The shift is a multiple of the angle between the propeller shaft axis
+ // and the relative wind that goes through the propeller disk.
+ if (P_Factor > 0.0001) {
+ double tangentialVel = localAeroVel.Magnitude(eV, eW);
+
+ if (tangentialVel > 0.0001) {
+ double angle = atan2(tangentialVel, localAeroVel(eU));
+ double factor = Sense * P_Factor * angle / tangentialVel;
+ SetActingLocationY( GetLocationY() + factor * localAeroVel(eW));
+ SetActingLocationZ( GetLocationZ() + factor * localAeroVel(eV));
+ }
+ }
+
omega = RPS*2.0*M_PI;
- vFn(1) = Thrust;
+ vFn(eX) = Thrust;
// The Ixx value and rotation speed given below are for rotation about the
// natural axis of the engine. The transform takes place in the base class
vH(eY) = 0.0;
vH(eZ) = 0.0;
- if (omega > 0.0) ExcessTorque = GearRatio * PowerAvailable / omega;
- else ExcessTorque = GearRatio * PowerAvailable / 1.0;
+ if (omega > 0.0) ExcessTorque = PowerAvailable / omega;
+ else ExcessTorque = PowerAvailable / 1.0;
RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
- if (RPM < 1.0) RPM = 0; // Engine friction stops rotation arbitrarily at 1 RPM.
+ if (RPM < 0.0) RPM = 0.0; // Engine won't turn backwards
- vMn = fdmex->GetPropagate()->GetPQR()*vH + vTorque*Sense;
+ // Transform Torque and momentum first, as PQR is used in this
+ // equation and cannot be transformed itself.
+ vMn = in.PQR*(Transform()*vH) + Transform()*vTorque;
return Thrust; // return thrust in pounds
}
double FGPropeller::GetPowerRequired(void)
{
double cPReq, J;
- double rho = fdmex->GetAtmosphere()->GetDensity();
+ double rho = in.Density;
+ double Vel = in.AeroUVW(eU);
double RPS = RPM / 60.0;
- if (RPS != 0) J = fdmex->GetAuxiliary()->GetAeroUVW(eU) / (Diameter * RPS);
- else J = 1000.0; // Set J to a high number
+ if (RPS != 0.0) J = Vel / (Diameter * RPS);
+ else J = Vel / Diameter;
- if (MaxPitch == MinPitch) { // Fixed pitch prop
- Pitch = MinPitch;
+ if (MaxPitch == MinPitch) { // Fixed pitch prop
cPReq = cPower->GetValue(J);
+
} else { // Variable pitch prop
- if (MaxRPM != MinRPM) { // fixed-speed prop
+ if (ConstantSpeed != 0) { // Constant Speed Mode
// do normal calculation when propeller is neither feathered nor reversed
+ // Note: This method of feathering and reversing was added to support the
+ // turboprop model. It's left here for backward compatablity, but
+ // now feathering and reversing should be done in Manual Pitch Mode.
if (!Feathered) {
if (!Reversed) {
double dRPM = rpmReq - RPM;
// The pitch of a variable propeller cannot be changed when the RPMs are
// too low - the oil pump does not work.
- if (RPM > 200) Pitch -= dRPM / 10;
-
+ if (RPM > 200) Pitch -= dRPM * deltaT;
if (Pitch < MinPitch) Pitch = MinPitch;
else if (Pitch > MaxPitch) Pitch = MaxPitch;
Pitch += (MaxPitch - Pitch) / 300; // just a guess (about 5 sec to fully feathered)
}
- } else { // Variable Speed Prop
- Pitch = MinPitch + (MaxPitch - MinPitch) * Advance;
+ } else { // Manual Pitch Mode, pitch is controlled externally
+
}
+
cPReq = cPower->GetValue(J, Pitch);
}
- if (RPS > 0) {
+ // Apply optional scaling factor to Cp (default value = 1)
+ cPReq *= CpFactor;
+
+ // Apply optional Mach effects from CP_MACH table
+ if (CpMach) cPReq *= CpMach->GetValue(HelicalTipMach);
+
+ if (RPS > 0.1) {
PowerRequired = cPReq*RPS*RPS*RPS*D5*rho;
vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
} else {
- PowerRequired = 0.0;
- vTorque(eX) = 0.0;
+ // For a stationary prop we have to estimate torque first.
+ double CL = (90.0 - Pitch) / 20.0;
+ if (CL > 1.5) CL = 1.5;
+ double BladeArea = Diameter * Diameter / 32.0 * numBlades;
+ vTorque(eX) = -Sense*BladeArea*Diameter*fabs(Vel)*Vel*rho*0.19*CL;
+ PowerRequired = Sense*(vTorque(eX))*0.2*M_PI;
}
return PowerRequired;
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-FGColumnVector3 FGPropeller::GetPFactor()
+FGColumnVector3 FGPropeller::GetPFactor() const
{
double px=0.0, py, pz;
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-string FGPropeller::GetThrusterLabels(int id, string delimeter)
+string FGPropeller::GetThrusterLabels(int id, const string& delimeter)
{
std::ostringstream buf;
- buf << Name << "_Torque[" << id << "]" << delimeter
- << Name << "_PFactor_Pitch[" << id << "]" << delimeter
- << Name << "_PFactor_Yaw[" << id << "]" << delimeter
- << Name << "_Thrust[" << id << "]" << delimeter;
+ buf << Name << " Torque (engine " << id << ")" << delimeter
+ << Name << " PFactor Pitch (engine " << id << ")" << delimeter
+ << Name << " PFactor Yaw (engine " << id << ")" << delimeter
+ << Name << " Thrust (engine " << id << " in lbs)" << delimeter;
if (IsVPitch())
- buf << Name << "_Pitch[" << id << "]" << delimeter;
- buf << Name << "_RPM[" << id << "]";
+ buf << Name << " Pitch (engine " << id << ")" << delimeter;
+ buf << Name << " RPM (engine " << id << ")";
return buf.str();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-string FGPropeller::GetThrusterValues(int id, string delimeter)
+string FGPropeller::GetThrusterValues(int id, const string& delimeter)
{
std::ostringstream buf;
cout << " Maximum Pitch = " << MaxPitch << endl;
cout << " Minimum RPM = " << MinRPM << endl;
cout << " Maximum RPM = " << MaxRPM << endl;
+// Tables are being printed elsewhere...
// cout << " Thrust Coefficient: " << endl;
// cThrust->Print();
// cout << " Power Coefficient: " << endl;
// cPower->Print();
+// cout << " Mach Thrust Coefficient: " << endl;
+// if(CtMach)
+// {
+// CtMach->Print();
+// } else {
+// cout << " NONE" << endl;
+// }
+// cout << " Mach Power Coefficient: " << endl;
+// if(CpMach)
+// {
+// CpMach->Print();
+// } else {
+// cout << " NONE" << endl;
+// }
}
}
if (debug_lvl & 2 ) { // Instantiation/Destruction notification
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