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// 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
//
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// DCL 28/9/00 - Added estimate of engine and prop inertia and changed engine speed calculation to be calculated from Angular acceleration = Torque / Inertia.
// Requires a timestep to be passed to FGEngine::init and currently assumes this timestep does not change.
// Could easily be altered to pass a variable timestep to FGEngine::update every step instead if required.
//
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//////////////////////////////////////////////////////////////////////
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# include <simgear/compiler.h>
# include <iostream>
# include <fstream>
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# include <math.h>
# include "IO360.hxx"
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FG_USING_STD ( cout ) ;
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// ------------------------------------------------------------------------
// 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 ;
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//combustion efficiency values from Heywood: ISBN 0-07-100499-8
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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
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void FGEngine : : init ( double dt ) {
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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 ;
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time_step = dt ;
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// 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
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engine_inertia = 0.2 ; //kgm^2 - value taken from a popular family saloon car engine - need to find an aeroengine value !!!!!
prop_inertia = 0.03 ; //kgm^2 - this value is a total guess - dcl
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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
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// for (num = 0; num < num2; num++) {
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// 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
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//first adjust actual mixture to abstract mixture - this is a temporary hack in order to account for the fact that the data I have
//dosn't specify actual mixtures and I want to be able to change what I think they are without redoing the curve fit each time.
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//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 ;
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;
}
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# endif
# ifdef NEVS_PROP_MODEL //use proper units - Nm
Torque_Imbalance = Torque_SI - prop_torque ; //This gives a +ve value when the engine torque exeeds the prop torque
angular_acceleration = Torque_Imbalance / ( engine_inertia + prop_inertia ) ;
angular_velocity_SI + = ( angular_acceleration * time_step ) ;
RPM = ( angular_velocity_SI * 60 ) / ( 2.0 * PI ) ;
# endif
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/*
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';
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// outfile << "RPM = " << RPM << " Engine torque = " << Torque_SI << " Prop torque = " << prop_torque << '\n';
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// cout << FGEng1_RPM << " Blade_Angle " << FGProp1_Blade_Angle << endl << endl;
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// 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 ) ;
}
