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flightgear/src/FDM/IO360.cxx

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Initial revision.
2000-09-26 23:37:26 +00:00
// Module: 10520c.c
// Author: Phil Schubert
// Date started: 12/03/99
// Purpose: Models a Continental IO-520-M Engine
// Called by: FGSimExec
//
// Copyright (C) 1999 Philip L. Schubert (philings@ozemail.com.au)
//
// 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 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 details.
//
// You should have received a copy of the GNU 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 the world wide web at http://www.gnu.org.
//
// FUNCTIONAL DESCRIPTION
// ------------------------------------------------------------------------
// Models a Continental IO-520-M engine. This engine is used in Cessna
// 210, 310, Beechcraft Bonaza and Baron C55. The equations used below
// were determined by a first and second order curve fits using Excel.
// The data is from the Cessna Aircraft Corporations Engine and Flight
// Computer for C310. Part Number D3500-13
//
// ARGUMENTS
// ------------------------------------------------------------------------
//
//
// HISTORY
// ------------------------------------------------------------------------
// 12/03/99 PLS Created
// 07/03/99 PLS Added Calculation of Density, and Prop_Torque
// 07/03/99 PLS Restructered Variables to allow easier implementation
// of Classes
// 15/03/99 PLS Added Oil Pressure, Oil Temperature and CH Temp
// ------------------------------------------------------------------------
// INCLUDES
// ------------------------------------------------------------------------
//
//
/////////////////////////////////////////////////////////////////////
//
// Modified by Dave Luff (david.luff@nottingham.ac.uk) September 2000
//
// Altered manifold pressure range to add a minimum value at idle to simulate the throttle stop / idle bypass valve,
// and to reduce the maximum value whilst the engine is running to slightly below ambient to account for CdA losses across the throttle
//
// Altered it a bit to model an IO360 from C172 - 360 cubic inches, 180 HP max, fixed pitch prop
// Added a simple fixed pitch prop model by Nev Harbor - this is not intended as a final model but simply a hack to get it running for now
// I used Phil's ManXRPM correlation for power rather than do a new one for the C172 for now, but altered it a bit to reduce power at the low end
//
// Added EGT model based on combustion efficiency and an energy balance with the exhaust gases
//
// Added a mixture - power correlation based on a curve in the IO360 operating manual
//
// I've tried to match the prop and engine model to give roughly 600 RPM idle and 180 HP at 2700 RPM
// but it is by no means currently at a completed stage - DCL 15/9/00
//
//////////////////////////////////////////////////////////////////////
#include <iostream.h>
#include <fstream.h>
#include <math.h>
#include "IO360.hxx"
// ------------------------------------------------------------------------
// CODE
// ------------------------------------------------------------------------
// Calculate Engine RPM based on Propellor Lever Position
float FGEngine::Calc_Engine_RPM (float LeverPosition)
{
// Calculate RPM as set by Prop Lever Position. Assumes engine
// will run at 1000 RPM at full course
float RPM;
RPM = LeverPosition * Max_RPM / 100.0;
// * ((FGEng_Max_RPM + FGEng_Min_RPM) / 100);
if ( RPM >= Max_RPM ) {
RPM = Max_RPM;
}
return RPM;
}
float FGEngine::Lookup_Combustion_Efficiency(float thi_actual)
{
float thi[11]; //array of equivalence ratio values
float neta_comb[11]; //corresponding array of combustion efficiency values
float neta_comb_actual;
float factor;
//thi = (0.0,0.9,1.0,1.05,1.1,1.15,1.2,1.3,1.4,1.5,1.6);
thi[0] = 0.0;
thi[1] = 0.9;
thi[2] = 1.0;
thi[3] = 1.05; //There must be an easier way of doing this !!!!!!!!
thi[4] = 1.1;
thi[5] = 1.15;
thi[6] = 1.2;
thi[7] = 1.3;
thi[8] = 1.4;
thi[9] = 1.5;
thi[10] = 1.6;
//neta_comb = (0.98,0.98,0.97,0.95,0.9,0.85,0.79,0.7,0.63,0.57,0.525);
neta_comb[0] = 0.98;
neta_comb[1] = 0.98;
neta_comb[2] = 0.97;
neta_comb[3] = 0.95;
neta_comb[4] = 0.9;
neta_comb[5] = 0.85;
neta_comb[6] = 0.79;
neta_comb[7] = 0.7;
neta_comb[8] = 0.63;
neta_comb[9] = 0.57;
neta_comb[10] = 0.525;
//combustion efficiency values from Heywood [1]
int i;
int j;
j = 11; //This must be equal to the number of elements in the lookup table arrays
for(i=0;i<j;i++)
{
if(i == (j-1))
{
//this is just to avoid crashing the routine is we are bigger than the last element - for now just return the last element
//but at some point we will have to extrapolate further
neta_comb_actual = neta_comb[i];
return neta_comb_actual;
}
if(thi_actual == thi[i])
{
neta_comb_actual = neta_comb[i];
return neta_comb_actual;
}
if((thi_actual > thi[i]) && (thi_actual < thi[i + 1]))
{
//do linear interpolation between the two points
factor = (thi_actual - thi[i]) / (thi[i+1] - thi[i]);
neta_comb_actual = (factor * (neta_comb[i+1] - neta_comb[i])) + neta_comb[i];
return neta_comb_actual;
}
}
//if we get here something has gone badly wrong
cout << "ERROR: error in FGEngine::Lookup_Combustion_Efficiency\n";
//exit(-1);
return neta_comb_actual; //keeps the compiler happy
}
/*
float FGEngine::Calculate_Delta_T_Exhaust(void)
{
float dT_exhaust;
heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
dT_exhaust = enthalpy_exhaust / heat_capacity_exhaust;
return(dT_exhaust);
}
*/
// Calculate Manifold Pressure based on Throttle lever Position
static float Calc_Manifold_Pressure ( float LeverPosn, float MaxMan, float MinMan)
{
float Inches;
// if ( x < = 0 ) {
// x = 0.00001;
// }
//Note that setting the manifold pressure as a function of lever position only is not strictly accurate
//MAP is also a function of engine speed.
Inches = MinMan + (LeverPosn * (MaxMan - MinMan) / 100);
//allow for idle bypass valve or slightly open throttle stop
if(Inches < MinMan)
Inches = MinMan;
return Inches;
}
// set initial default values
void FGEngine::init() {
CONVERT_CUBIC_INCHES_TO_METERS_CUBED = 1.638706e-5;
// Control and environment inputs
IAS = 0;
Throttle_Lever_Pos = 75;
Propeller_Lever_Pos = 75;
Mixture_Lever_Pos = 100;
Cp_air = 1005; // J/KgK
Cp_fuel = 1700; // J/KgK
calorific_value_fuel = 47.3e6; // W/Kg Note that this is only an approximate value
R_air = 287.3;
// Engine Specific Variables used by this program that have limits.
// Will be set in a parameter file to be read in to create
// and instance for each engine.
Max_Manifold_Pressure = 28.50; //Inches Hg. An approximation - should be able to find it in the engine performance data
Min_Manifold_Pressure = 6.5; //Inches Hg. This is a guess corresponding to approx 0.24 bar MAP (7 in Hg) - need to find some proper data for this
Max_RPM = 2700;
Min_RPM = 600; //Recommended idle from Continental data sheet
Max_Fuel_Flow = 130;
Mag_Derate_Percent = 5;
// MaxHP = 285; //Continental IO520-M
MaxHP = 180; //Lycoming IO360
// displacement = 520; //Continental IO520-M
displacement = 360; //Lycoming IO360
displacement_SI = displacement * CONVERT_CUBIC_INCHES_TO_METERS_CUBED;
Gear_Ratio = 1;
started = true;
cranking = false;
CONVERT_HP_TO_WATTS = 745.6999;
// ofstream outfile;
// outfile.open(ios::out|ios::trunc);
// Initialise Engine Variables used by this instance
Percentage_Power = 0;
Manifold_Pressure = 29.00; // Inches
RPM = 600;
Fuel_Flow = 0; // lbs/hour
Torque = 0;
CHT = 370;
Mixture = 14;
Oil_Pressure = 0; // PSI
Oil_Temp = 85; // Deg C
HP = 0;
RPS = 0;
Torque_Imbalance = 0;
Desired_RPM = 2500; //Recommended cruise RPM from Continental datasheet
// Initialise Propellor Variables used by this instance
FGProp1_Angular_V = 0;
FGProp1_Coef_Drag = 0.6;
FGProp1_Torque = 0;
FGProp1_Thrust = 0;
FGProp1_RPS = 0;
FGProp1_Coef_Lift = 0.1;
Alpha1 = 13.5;
FGProp1_Blade_Angle = 13.5;
FGProp_Fine_Pitch_Stop = 13.5;
// Other internal values
Rho = 0.002378;
}
// Calculate Oil Pressure
static float Oil_Press (float Oil_Temp, float Engine_RPM)
{
float Oil_Pressure = 0; //PSI
float Oil_Press_Relief_Valve = 60; //PSI
float Oil_Press_RPM_Max = 1800;
float Design_Oil_Temp = 85; //Celsius
float Oil_Viscosity_Index = 0.25; // PSI/Deg C
float Temp_Deviation = 0; // Deg C
Oil_Pressure = (Oil_Press_Relief_Valve / Oil_Press_RPM_Max) * Engine_RPM;
// Pressure relief valve opens at Oil_Press_Relief_Valve PSI setting
if (Oil_Pressure >= Oil_Press_Relief_Valve)
{
Oil_Pressure = Oil_Press_Relief_Valve;
}
// Now adjust pressure according to Temp which affects the viscosity
Oil_Pressure += (Design_Oil_Temp - Oil_Temp) * Oil_Viscosity_Index;
return Oil_Pressure;
}
// Calculate Cylinder Head Temperature
static float Calc_CHT (float Fuel_Flow, float Mixture, float IAS)
{
float CHT = 350;
return CHT;
}
/*
//Calculate Exhaust Gas Temperature
//For now we will simply adjust this as a function of mixture
//It may be necessary to consider fuel flow rates and CHT in the calculation in the future
static float Calc_EGT (float Mixture)
{
float EGT = 1000; //off the top of my head !!!!
//Now adjust for mixture strength
return EGT;
}*/
// Calculate Density Ratio
static float Density_Ratio ( float x )
{
float y ;
y = ((3E-10 * x * x) - (3E-05 * x) + 0.9998);
return(y);
}
// Calculate Air Density - Rho
static float Density ( float x )
{
float y ;
y = ((9E-08 * x * x) - (7E-08 * x) + 0.0024);
return(y);
}
// Calculate Speed in FPS given Knots CAS
static float IAS_to_FPS (float x)
{
float y;
y = x * 1.68888888;
return y;
}
// update the engine model based on current control positions
void FGEngine::update() {
// Declare local variables
int num = 0;
// const int num2 = 500; // default is 100, number if iterations to run
const int num2 = 5; // default is 100, number if iterations to run
float ManXRPM = 0;
float Vo = 0;
float V1 = 0;
// Set up the new variables
float Blade_Station = 30;
float FGProp_Area = 1.405/3;
float PI = 3.1428571;
// Input Variables
// 0 = Closed, 100 = Fully Open
// float Throttle_Lever_Pos = 75;
// 0 = Full Course 100 = Full Fine
// float Propeller_Lever_Pos = 75;
// 0 = Idle Cut Off 100 = Full Rich
// float Mixture_Lever_Pos = 100;
// Environmental Variables
// Temp Variation from ISA (Deg F)
float FG_ISA_VAR = 0;
// Pressure Altitude 1000's of Feet
float FG_Pressure_Ht = 0;
// Parameters that alter the operation of the engine.
// Yes = 1. Is there Fuel Available. Calculated elsewhere
int Fuel_Available = 1;
// Off = 0. Reduces power by 3 % for same throttle setting
int Alternate_Air_Pos =0;
// 1 = On. Reduces power by 5 % for same power lever settings
int Magneto_Left = 1;
// 1 = On. Ditto, Both of the above though do not alter fuel flow
int Magneto_Right = 1;
// There needs to be a section in here to trap silly values, like
// 0, otherwise they will crash the calculations
// cout << " Number of Iterations ";
// cin >> num2;
// cout << endl;
// cout << " Throttle % ";
// cin >> Throttle_Lever_Pos;
// cout << endl;
// cout << " Prop % ";
// cin >> Propeller_Lever_Pos;
// cout << endl;
//==================================================================
// Engine & Environmental Inputs from elsewhere
// Calculate Air Density (Rho) - In FG this is calculated in
// FG_Atomoshere.cxx
Rho = Density(FG_Pressure_Ht); // In FG FG_Pressure_Ht is "h"
// cout << "Rho = " << Rho << endl;
// Calculate Manifold Pressure (Engine 1) as set by throttle opening
Manifold_Pressure =
Calc_Manifold_Pressure( Throttle_Lever_Pos, Max_Manifold_Pressure, Min_Manifold_Pressure );
// cout << "manifold pressure = " << Manifold_Pressure << endl;
//DCL - hack for testing - fly at sea level
T_amb = 298.0;
p_amb = 101325;
p_amb_sea_level = 101325;
//DCL - next calculate m_dot_air and m_dot_fuel into engine
//calculate actual ambient pressure and temperature from altitude
//Then find the actual manifold pressure (the calculated one is the sea level pressure)
True_Manifold_Pressure = Manifold_Pressure * p_amb / p_amb_sea_level;
// RPM = Calc_Engine_RPM(Propeller_Lever_Pos);
// RPM = 600;
// cout << "Initial engine RPM = " << RPM << endl;
// Desired_RPM = RPM;
//**************
//DCL - calculate mass air flow into engine based on speed and load - separate this out into a function eventually
//t_amb is actual temperature calculated from altitude
//calculate density from ideal gas equation
rho_air = p_amb / ( R_air * T_amb );
rho_air_manifold = rho_air * Manifold_Pressure / 29.6;
//calculate ideal engine volume inducted per second
swept_volume = (displacement_SI * (RPM / 60)) / 2; //This equation is only valid for a four stroke engine
//calculate volumetric efficiency - for now we will just use 0.8, but actually it is a function of engine speed and the exhaust to manifold pressure ratio
volumetric_efficiency = 0.8;
//Now use volumetric efficiency to calculate actual air volume inducted per second
v_dot_air = swept_volume * volumetric_efficiency;
//Now calculate mass flow rate of air into engine
m_dot_air = v_dot_air * rho_air_manifold;
// cout << "rho air manifold " << rho_air_manifold << '\n';
// cout << "Swept volume " << swept_volume << '\n';
//**************
//DCL - now calculate fuel flow into engine based on air flow and mixture lever position
//assume lever runs from no flow at fully out to thi = 1.6 at fully in at sea level
//also assume that the injector linkage is ideal - hence the set mixture is maintained at a given altitude throughout the speed and load range
thi_sea_level = 1.6 * ( Mixture_Lever_Pos / 100.0 );
equivalence_ratio = thi_sea_level * p_amb_sea_level / p_amb; //ie as we go higher the mixture gets richer for a given lever position
m_dot_fuel = m_dot_air / 14.7 * equivalence_ratio;
// cout << "fuel " << m_dot_fuel;
// cout << " air " << m_dot_air << '\n';
//**************
// cout << "Thi = " << equivalence_ratio << '\n';
combustion_efficiency = Lookup_Combustion_Efficiency(equivalence_ratio); //The combustion efficiency basically tells us what proportion of the fuels calorific value is released
// cout << "Combustion efficiency = " << combustion_efficiency << '\n';
//now calculate energy release to exhaust
//We will assume a three way split of fuel energy between useful work, the coolant system and the exhaust system
//This is a reasonable first suck of the thumb estimate for a water cooled automotive engine - whether it holds for an air cooled aero engine is probably open to question
//Regardless - it won't affect the variation of EGT with mixture, and we con always put a multiplier on EGT to get a reasonable peak value.
enthalpy_exhaust = m_dot_fuel * calorific_value_fuel * combustion_efficiency * 0.33;
heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
delta_T_exhaust = enthalpy_exhaust / heat_capacity_exhaust;
// delta_T_exhaust = Calculate_Delta_T_Exhaust();
// cout << "T_amb " << T_amb;
// cout << " dT exhaust = " << delta_T_exhaust;
EGT = T_amb + delta_T_exhaust;
// cout << " EGT = " << EGT << '\n';
// Calculate Manifold Pressure (Engine 2) as set by throttle opening
// FGEng2_Manifold_Pressure = Manifold_Pressure(FGEng2_Throttle_Lever_Pos, FGEng2_Manifold_Pressure);
// Show_Manifold_Pressure(FGEng2_Manifold_Pressure);
//==================================================================
// Engine Power & Torque Calculations
// Loop until stable - required for testing only
for (num = 0; num < num2; num++) {
// cout << Manifold_Pressure << " Inches" << "\t";
// cout << RPM << " RPM" << "\t";
// For a given Manifold Pressure and RPM calculate the % Power
// Multiply Manifold Pressure by RPM
ManXRPM = Manifold_Pressure * RPM;
// cout << ManXRPM;
// cout << endl;
// Phil's %power correlation
/* // Calculate % Power
Percentage_Power = (+ 7E-09 * ManXRPM * ManXRPM)
+ ( + 7E-04 * ManXRPM) - 0.1218;
// cout << Percentage_Power << "%" << "\t"; */
// DCL %power correlation - basically Phil's correlation modified to give slighty less power at the low end
// might need some adjustment as the prop model is adjusted
// My aim is to match the prop model and engine model at the low end to give the manufacturer's recommended idle speed with the throttle closed - 600rpm for the Continental IO520
// Calculate % Power
Percentage_Power = (+ 6E-09 * ManXRPM * ManXRPM)
+ ( + 8E-04 * ManXRPM) - 1.8524;
// cout << Percentage_Power << "%" << "\t";
// Adjust for Temperature - Temperature above Standard decrease
// power % by 7/120 per degree F increase, and incease power for
// temps below at the same ratio
Percentage_Power = Percentage_Power - (FG_ISA_VAR * 7 /120);
// cout << Percentage_Power << "%" << "\t";
// Adjust for Altitude. In this version a linear variation is
// used. Decrease 1% for each 1000' increase in Altitde
Percentage_Power = Percentage_Power + (FG_Pressure_Ht * 12/10000);
// cout << Percentage_Power << "%" << "\t";
//DCL - now adjust power to compensate for mixture
//uses a curve fit to the data in the IO360 / O360 operating manual
//due to the shape of the curve I had to use a 6th order fit - I am sure it must be possible to reduce this in future,
//possibly by using separate fits for rich and lean of best power mixture
//first adjust actual mixture to abstract mixture - this is a temporary hack
//y=10x-12 for now
abstract_mixture = 10.0 * equivalence_ratio - 12.0;
float m = abstract_mixture; //to simplify writing the next equation
Percentage_of_best_power_mixture_power = ((-0.0012*m*m*m*m*m*m) + (0.021*m*m*m*m*m) + (-0.1425*m*m*m*m) + (0.4395*m*m*m) + (-0.8909*m*m) + (-0.5155*m) + 100.03);
Percentage_Power = Percentage_Power * Percentage_of_best_power_mixture_power / 100.0;
// Now Calculate Fuel Flow based on % Power Best Power Mixture
Fuel_Flow = Percentage_Power * Max_Fuel_Flow / 100.0;
// cout << Fuel_Flow << " lbs/hr"<< endl;
// Now Derate engine for the effects of Bad/Switched off magnetos
if (Magneto_Left == 0 && Magneto_Right == 0) {
// cout << "Both OFF\n";
Percentage_Power = 0;
} else if (Magneto_Left && Magneto_Right) {
// cout << "Both On ";
} else if (Magneto_Left == 0 || Magneto_Right== 0) {
// cout << "1 Magneto Failed ";
Percentage_Power = Percentage_Power *
((100.0 - Mag_Derate_Percent)/100.0);
// cout << FGEng1_Percentage_Power << "%" << "\t";
}
// Calculate Engine Horsepower
HP = Percentage_Power * MaxHP / 100.0;
Power_SI = HP * CONVERT_HP_TO_WATTS;
// Calculate Engine Torque
Torque = HP * 5252 / RPM;
// cout << Torque << "Ft/lbs" << "\t";
Torque_SI = (Power_SI * 60.0) / (2.0 * PI * RPM); //Torque = power / angular velocity
// cout << Torque << " Nm\n";
// Calculate Cylinder Head Temperature
CHT = Calc_CHT( Fuel_Flow, Mixture, IAS);
// cout << "Cylinder Head Temp (F) = " << CHT << endl;
// EGT = Calc_EGT( Mixture );
// Calculate Oil Pressure
Oil_Pressure = Oil_Press( Oil_Temp, RPM );
// cout << "Oil Pressure (PSI) = " << Oil_Pressure << endl;
//==============================================================
// Now do the Propellor Calculations
#ifdef PHILS_PROP_MODEL
// Revs per second
FGProp1_RPS = RPM * Gear_Ratio / 60.0;
// cout << FGProp1_RPS << " RPS" << endl;
//Radial Flow Vector (V2) Ft/sec at Ref Blade Station (usually 30")
FGProp1_Angular_V = FGProp1_RPS * 2 * PI * (Blade_Station / 12);
// cout << FGProp1_Angular_V << "Angular Velocity " << endl;
// Axial Flow Vector (Vo) Ft/sec
// Some further work required here to allow for inflow at low speeds
// Vo = (IAS + 20) * 1.688888;
Vo = IAS_to_FPS(IAS + 20);
// cout << "Feet/sec = " << Vo << endl;
// cout << Vo << "Axial Velocity" << endl;
// Relative Velocity (V1)
V1 = sqrt((FGProp1_Angular_V * FGProp1_Angular_V) +
(Vo * Vo));
// cout << V1 << "Relative Velocity " << endl;
// cout << FGProp1_Blade_Angle << " Prop Blade Angle" << endl;
// Blade Angle of Attack (Alpha1)
/* cout << " Alpha1 = " << Alpha1
<< " Blade angle = " << FGProp1_Blade_Angle
<< " Vo = " << Vo
<< " FGProp1_Angular_V = " << FGProp1_Angular_V << endl;*/
Alpha1 = FGProp1_Blade_Angle -(atan(Vo / FGProp1_Angular_V) * (180/PI));
// cout << Alpha1 << " Alpha1" << endl;
// Calculate Coefficient of Drag at Alpha1
FGProp1_Coef_Drag = (0.0005 * (Alpha1 * Alpha1)) + (0.0003 * Alpha1)
+ 0.0094;
// cout << FGProp1_Coef_Drag << " Coef Drag" << endl;
// Calculate Coefficient of Lift at Alpha1
FGProp1_Coef_Lift = -(0.0026 * (Alpha1 * Alpha1)) + (0.1027 * Alpha1)
+ 0.2295;
// cout << FGProp1_Coef_Lift << " Coef Lift " << endl;
// Covert Alplha1 to Radians
// Alpha1 = Alpha1 * PI / 180;
// Calculate Prop Torque
FGProp1_Torque = (0.5 * Rho * (V1 * V1) * FGProp_Area
* ((FGProp1_Coef_Lift * sin(Alpha1 * PI / 180))
+ (FGProp1_Coef_Drag * cos(Alpha1 * PI / 180))))
* (Blade_Station/12);
// cout << FGProp1_Torque << " Prop Torque" << endl;
// Calculate Prop Thrust
// cout << " V1 = " << V1 << " Alpha1 = " << Alpha1 << endl;
FGProp1_Thrust = 0.5 * Rho * (V1 * V1) * FGProp_Area
* ((FGProp1_Coef_Lift * cos(Alpha1 * PI / 180))
- (FGProp1_Coef_Drag * sin(Alpha1 * PI / 180)));
// cout << FGProp1_Thrust << " Prop Thrust " << endl;
// End of Propeller Calculations
//==============================================================
#endif //PHILS_PROP_MODEL
#ifdef NEVS_PROP_MODEL
// Nev's prop model
num_elements = 6.0;
number_of_blades = 2.0;
blade_length = 0.95;
allowance_for_spinner = blade_length / 12.0;
prop_fudge_factor = 1.453401525;
forward_velocity = IAS;
theta[0] = 25.0;
theta[1] = 20.0;
theta[2] = 15.0;
theta[3] = 10.0;
theta[4] = 5.0;
theta[5] = 0.0;
angular_velocity_SI = 2.0 * PI * RPM / 60.0;
allowance_for_spinner = blade_length / 12.0;
//Calculate thrust and torque by summing the contributions from each of the blade elements
//Assumes equal length elements with numbered 1 inboard -> num_elements outboard
prop_torque = 0.0;
prop_thrust = 0.0;
int i;
// outfile << "Rho = " << Rho << '\n\n';
// outfile << "Drag = ";
for(i=1;i<=num_elements;i++)
{
element = float(i);
distance = (blade_length * (element / num_elements)) + allowance_for_spinner;
element_drag = 0.5 * rho_air * ((distance * angular_velocity_SI)*(distance * angular_velocity_SI)) * (0.000833 * ((theta[int(element-1)] - (atan(forward_velocity/(distance * angular_velocity_SI))))*(theta[int(element-1)] - (atan(forward_velocity/(distance * angular_velocity_SI))))))
* (0.1 * (blade_length / element)) * number_of_blades;
element_lift = 0.5 * rho_air * ((distance * angular_velocity_SI)*(distance * angular_velocity_SI)) * (0.036 * (theta[int(element-1)] - (atan(forward_velocity/(distance * angular_velocity_SI))))+0.4)
* (0.1 * (blade_length / element)) * number_of_blades;
element_torque = element_drag * distance;
prop_torque += element_torque;
prop_thrust += element_lift;
// outfile << "Drag = " << element_drag << " n = " << element << '\n';
}
// outfile << '\n';
// outfile << "Angular velocity = " << angular_velocity_SI << " rad/s\n";
// cout << "Thrust = " << prop_thrust << '\n';
prop_thrust *= prop_fudge_factor;
prop_torque *= prop_fudge_factor;
prop_power_consumed_SI = prop_torque * angular_velocity_SI;
prop_power_consumed_HP = prop_power_consumed_SI / 745.699;
#endif //NEVS_PROP_MODEL
//#if 0
#ifdef PHILS_PROP_MODEL //Do Torque calculations in Ft/lbs - yuk :-(((
Torque_Imbalance = FGProp1_Torque - Torque;
#endif
#ifdef NEVS_PROP_MODEL //use proper units - Nm
Torque_Imbalance = prop_torque - Torque_SI;
#endif
// cout << Torque_Imbalance << endl;
// Some really crude engine speed calculations for now - we really need some moments of inertia and a dt in here !!!!
if (Torque_Imbalance > 5) {
RPM -= 14.5;
// FGProp1_RPM -= 25;
// FGProp1_Blade_Angle -= 0.75;
}
if (Torque_Imbalance < -5) {
RPM += 14.5;
// FGProp1_RPM += 25;
// FGProp1_Blade_Angle += 0.75;
}
//DCL - This constant speed prop bit is all a bit of a hack for now
/*
if( RPM > (Desired_RPM + 2)) {
FGProp1_Blade_Angle += 0.75; //This value could be altered depending on how far from the desired RPM we are
}
if( RPM < (Desired_RPM - 2)) {
FGProp1_Blade_Angle -= 0.75;
}
if (FGProp1_Blade_Angle < FGProp_Fine_Pitch_Stop) {
FGProp1_Blade_Angle = FGProp_Fine_Pitch_Stop;
}
if (RPM >= 2700) {
RPM = 2700;
}
*/
//end constant speed prop
//#endif
//DCL - stall the engine if RPM drops below 550 - this is possible if mixture lever is pulled right out
if(RPM < 550)
RPM = 0;
// outfile << "RPM = " << RPM << " Blade angle = " << FGProp1_Blade_Angle << " Engine torque = " << Torque << " Prop torque = " << FGProp1_Torque << '\n';
outfile << "RPM = " << RPM << " Engine torque = " << Torque_SI << " Prop torque = " << prop_torque << '\n';
// cout << FGEng1_RPM << " Blade_Angle " << FGProp1_Blade_Angle << endl << endl;
}
// cout << "Final engine RPM = " << RPM << '\n';
}
// Functions
// Calculate Oil Temperature
static float Oil_Temp (float Fuel_Flow, float Mixture, float IAS)
{
float Oil_Temp = 85;
return (Oil_Temp);
}
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