Here are updated IO360.cxx and IO360.hxx files with an alteration to
bring EGT down to a more reasonable range. EGT is now returned in deg Fahrenheit (yuk!!) by the accessor function since that is what the guage is calibrated in, and the absolute max value that can be output (max power mixture at max power) is about 750 deg F. Dave, I suggest that you set the guage to run from 450 - 750 deg F between the four big marker ticks. What do the offset and scale actually refer to in the .xml config file BTW? Fuel flow, better handling of manifold pressure wrt engine speed, and proper consideration of altitude effects next, hopefully.
This commit is contained in:
curt
parent
d79bfda33f
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2 changed files with 93 additions and 69 deletions
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@ -70,6 +70,11 @@
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// Requires a timestep to be passed to FGNewEngine::init and currently assumes this timestep does not change.
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// Could easily be altered to pass a variable timestep to FGNewEngine::update every step instead if required.
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//
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// DCL 27/10/00 - Added first stab at cylinder head temperature model
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// See the comment block in the code for details
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//
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// DCL 02/11/00 - Modified EGT code to reduce values to those more representative of a sensor downstream
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//
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//////////////////////////////////////////////////////////////////////
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#include <simgear/compiler.h>
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@ -454,7 +459,80 @@ void FGNewEngine::update() {
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// cout << "fuel " << m_dot_fuel;
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// cout << " air " << m_dot_air << '\n';
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//**************
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//***********************************************************************
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//Calculate percentage power
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// For a given Manifold Pressure and RPM calculate the % Power
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// Multiply Manifold Pressure by RPM
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ManXRPM = Manifold_Pressure * RPM;
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// cout << ManXRPM;
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// cout << endl;
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/*
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// Phil's %power correlation
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// Calculate % Power
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Percentage_Power = (+ 7E-09 * ManXRPM * ManXRPM) + ( + 7E-04 * ManXRPM) - 0.1218;
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// cout << Percentage_Power << "%" << "\t";
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*/
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// DCL %power correlation - basically Phil's correlation modified to give slighty less power at the low end
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// might need some adjustment as the prop model is adjusted
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// 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
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// Calculate % Power
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Percentage_Power = (+ 6E-09 * ManXRPM * ManXRPM) + ( + 8E-04 * ManXRPM) - 1.8524;
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// cout << Percentage_Power << "%" << "\t";
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// Adjust for Temperature - Temperature above Standard decrease
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// power % by 7/120 per degree F increase, and incease power for
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// temps below at the same ratio
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Percentage_Power = Percentage_Power - (FG_ISA_VAR * 7 /120);
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// cout << Percentage_Power << "%" << "\t";
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//******DCL - this bit will need altering or removing if I go to true altitude adjusted manifold pressure
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// Adjust for Altitude. In this version a linear variation is
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// used. Decrease 1% for each 1000' increase in Altitde
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Percentage_Power = Percentage_Power + (FG_Pressure_Ht * 12/10000);
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// cout << Percentage_Power << "%" << "\t";
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//DCL - now adjust power to compensate for mixture
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//uses a curve fit to the data in the IO360 / O360 operating manual
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//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,
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//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
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//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
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abstract_mixture = 10.0 * equivalence_ratio - 12.0;
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float m = abstract_mixture; //to simplify writing the next equation
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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);
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Percentage_Power = Percentage_Power * Percentage_of_best_power_mixture_power / 100.0;
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//cout << " %POWER = " << Percentage_Power << '\n';
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//***DCL - FIXME - this needs altering - for instance going richer than full power mixture decreases the %power but increases the fuel flow
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// Now Calculate Fuel Flow based on % Power Best Power Mixture
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Fuel_Flow = Percentage_Power * Max_Fuel_Flow / 100.0;
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// cout << Fuel_Flow << " lbs/hr"<< endl;
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// Now Derate engine for the effects of Bad/Switched off magnetos
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if (Magneto_Left == 0 && Magneto_Right == 0) {
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// cout << "Both OFF\n";
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Percentage_Power = 0;
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} else if (Magneto_Left && Magneto_Right) {
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// cout << "Both On ";
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} else if (Magneto_Left == 0 || Magneto_Right== 0) {
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// cout << "1 Magneto Failed ";
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Percentage_Power = Percentage_Power *
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((100.0 - Mag_Derate_Percent)/100.0);
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// cout << FGEng1_Percentage_Power << "%" << "\t";
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}
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//**********************************************************************
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//Calculate Exhaust gas temperature
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// cout << "Thi = " << equivalence_ratio << '\n';
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@ -476,7 +554,15 @@ void FGNewEngine::update() {
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EGT = T_amb + delta_T_exhaust;
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// cout << " EGT = " << EGT << '\n';
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//The above gives the exhaust temperature immediately prior to leaving the combustion chamber
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//Now derate to give a more realistic figure as measured downstream
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//For now we will aim for a peak of around 400 degC (750 degF)
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EGT *= 0.444 + ((0.544 - 0.444) * Percentage_Power / 100.0);
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EGT_degF = (EGT * 1.8) - 459.67;
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//cout << " EGT = " << EGT << " degK " << EGT_degF << " degF";// << '\n';
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//***************************************************************************************
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// Calculate Cylinder Head Temperature
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@ -561,7 +647,7 @@ the values from file to avoid the necessity for re-compilation every time I chan
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CHT_degF = (CHT * 1.8) - 459.67;
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// cout << "CHT = " << CHT_degF << " degF\n";
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//cout << " CHT = " << CHT_degF << " degF\n";
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// End calculate Cylinder Head Temperature
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@ -571,69 +657,7 @@ the values from file to avoid the necessity for re-compilation every time I chan
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// Engine Power & Torque Calculations
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// For a given Manifold Pressure and RPM calculate the % Power
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// Multiply Manifold Pressure by RPM
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ManXRPM = Manifold_Pressure * RPM;
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// cout << ManXRPM;
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// cout << endl;
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/*
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// Phil's %power correlation
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// Calculate % Power
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Percentage_Power = (+ 7E-09 * ManXRPM * ManXRPM) + ( + 7E-04 * ManXRPM) - 0.1218;
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// cout << Percentage_Power << "%" << "\t";
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*/
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// DCL %power correlation - basically Phil's correlation modified to give slighty less power at the low end
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// might need some adjustment as the prop model is adjusted
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// 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
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// Calculate % Power
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Percentage_Power = (+ 6E-09 * ManXRPM * ManXRPM) + ( + 8E-04 * ManXRPM) - 1.8524;
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// cout << Percentage_Power << "%" << "\t";
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// Adjust for Temperature - Temperature above Standard decrease
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// power % by 7/120 per degree F increase, and incease power for
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// temps below at the same ratio
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Percentage_Power = Percentage_Power - (FG_ISA_VAR * 7 /120);
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// cout << Percentage_Power << "%" << "\t";
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// Adjust for Altitude. In this version a linear variation is
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// used. Decrease 1% for each 1000' increase in Altitde
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Percentage_Power = Percentage_Power + (FG_Pressure_Ht * 12/10000);
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// cout << Percentage_Power << "%" << "\t";
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//DCL - now adjust power to compensate for mixture
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//uses a curve fit to the data in the IO360 / O360 operating manual
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//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,
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//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
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//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
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abstract_mixture = 10.0 * equivalence_ratio - 12.0;
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float m = abstract_mixture; //to simplify writing the next equation
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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);
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Percentage_Power = Percentage_Power * Percentage_of_best_power_mixture_power / 100.0;
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// Now Calculate Fuel Flow based on % Power Best Power Mixture
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Fuel_Flow = Percentage_Power * Max_Fuel_Flow / 100.0;
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// cout << Fuel_Flow << " lbs/hr"<< endl;
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// Now Derate engine for the effects of Bad/Switched off magnetos
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if (Magneto_Left == 0 && Magneto_Right == 0) {
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// cout << "Both OFF\n";
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Percentage_Power = 0;
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} else if (Magneto_Left && Magneto_Right) {
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// cout << "Both On ";
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} else if (Magneto_Left == 0 || Magneto_Right== 0) {
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// cout << "1 Magneto Failed ";
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Percentage_Power = Percentage_Power *
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((100.0 - Mag_Derate_Percent)/100.0);
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// cout << FGEng1_Percentage_Power << "%" << "\t";
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}
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// Calculate Engine Horsepower
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@ -102,7 +102,8 @@ private:
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float Torque;
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float CHT; // Cylinder head temperature deg K
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float CHT_degF; // Ditto in deg Fahrenheit
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float EGT; // Exhaust gas temperature
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float EGT; // Exhaust gas temperature deg K
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float EGT_degF; // Exhaust gas temperature deg Fahrenheit
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float Mixture;
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float Oil_Pressure; // PSI
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float Oil_Temp; // Deg C
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@ -230,9 +231,8 @@ public:
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inline float get_Rho() const { return Rho; }
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inline float get_MaxHP() const { return MaxHP; }
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inline float get_Percentage_Power() const { return Percentage_Power; }
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inline float get_EGT() const { return EGT; }
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// Note this returns CHT in Fahrenheit
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inline float get_CHT() const { return CHT_degF; }
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inline float get_EGT() const { return EGT_degF; } // Returns EGT in Fahrenheit
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inline float get_CHT() const { return CHT_degF; } // Note this returns CHT in Fahrenheit
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inline float get_prop_thrust_SI() const { return prop_thrust; }
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};
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