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 Lesser General Public License as published by the Free Software
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+#include <iostream>
#include <sstream>
#include "FGPropeller.h"
-#include <models/FGPropagate.h>
-#include <models/FGAtmosphere.h>
-#include <models/FGAuxiliary.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 1.32 2010/10/21 03:27:40 jberndt Exp $";
static const char *IdHdr = ID_PROPELLER;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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");
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);
}
}
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 );
- snprintf(property_name, 80, "propulsion/engine[%d]/propeller-rpm", EngineNum);
- PropertyManager->Tie( property_name, this, &FGPropeller::GetRPM );
+ Pitch = MinPitch;
+
+ string property_name, base_property_name;
+ base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNum);
+ 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);
}
{
delete cThrust;
delete cPower;
+ delete CtMach;
+ delete CpMach;
Debug(1);
}
double rho = fdmex->GetAtmosphere()->GetDensity();
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) /
+ fdmex->GetAtmosphere()->GetSoundSpeed();
- if (MaxPitch == MinPitch) ThrustCoeff = cThrust->GetValue(J);
- else ThrustCoeff = cThrust->GetValue(J, Pitch);
+ 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);
+
if (P_Factor > 0.0001) {
alpha = fdmex->GetAuxiliary()->Getalpha();
beta = fdmex->GetAuxiliary()->Getbeta();
}
Thrust = ThrustCoeff*RPS*RPS*D4*rho;
+
+ // From B. W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics"
+ // first edition, eqn. 6.15 (propeller analysis chapter).
+ Vinduced = 0.5 * (-Vel + sqrt(Vel*Vel + 2.0*Thrust/(rho*Area)));
+
omega = RPS*2.0*M_PI;
vFn(1) = Thrust;
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;
+ // Transform Torque and momentum first, as PQR is used in this
+ // equation and cannot be transformed itself.
+ vMn = fdmex->GetPropagate()->GetPQR()*(Transform()*vH) + Transform()*vTorque;
return Thrust; // return thrust in pounds
}
{
double cPReq, J;
double rho = fdmex->GetAtmosphere()->GetDensity();
+ double Vel = fdmex->GetAuxiliary()->GetAeroUVW(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);
}
+
+ // Apply optional scaling factor to Cp (default value = 1)
cPReq *= CpFactor;
- if (RPS > 0) {
+ // 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*Vel*Vel*rho*0.19*CL;
+ PowerRequired = fabs(vTorque(eX))*0.2*M_PI;
}
return PowerRequired;
projects / flightgear.git / blobdiff