// 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 #include #include #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 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 = 200; // 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); }