// IO360.hxx - a piston engine model currently for the IO360 engine fitted to the C172 // but with the potential to model other naturally aspirated piston engines // given appropriate config input. // // Written by David Luff, started 2000. // Based on code by Phil Schubert, started 1999. // // 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. #ifndef _IO360_HXX_ #define _IO360_HXX_ #include #include class FGNewEngine { private: // These constants should probably be moved eventually float CONVERT_CUBIC_INCHES_TO_METERS_CUBED; float CONVERT_HP_TO_WATTS; // Properties of working fluids float Cp_air; // J/KgK float Cp_fuel; // J/KgK float calorific_value_fuel; // W/Kg float rho_fuel; // kg/m^3 float rho_air; // kg/m^3 // environment inputs float p_amb_sea_level; // Sea level ambient pressure in Pascals float p_amb; // Ambient pressure at current altitude in Pascals float T_amb; // ditto deg Kelvin // Control inputs float Throttle_Lever_Pos; // 0 = Closed, 100 = Fully Open float Propeller_Lever_Pos; // 0 = Full Course 100 = Full Fine float Mixture_Lever_Pos; // 0 = Idle Cut Off 100 = Full Rich int mag_pos; // 0=off, 1=left, 2=right, 3=both. bool starter; //misc float IAS; double time_step; // Engine Specific Variables that should be read in from a config file float MaxHP; // Horsepower float displacement; // Cubic inches float displacement_SI; //m^3 (derived from above rather than read in) float engine_inertia; //kg.m^2 float prop_inertia; //kg.m^2 float Max_Fuel_Flow; // Units??? Do we need this variable any more?? // Engine specific variables that maybe should be read in from config but are pretty generic and won't vary much for a naturally aspirated piston engine. float Max_Manifold_Pressure; // inches Hg - typical manifold pressure at full throttle and typical max rpm float Min_Manifold_Pressure; // inches Hg - typical manifold pressure at idle (closed throttle) float Max_RPM; // rpm - this is really a bit of a hack and could be make redundant if the prop model works properly and takes tips at speed of sound into account. float Min_RPM; // rpm - possibly redundant ??? float Mag_Derate_Percent; // Percentage reduction in power when mags are switched from 'both' to either 'L' or 'R' float Gear_Ratio; // Gearing between engine and propellor float n_R; // Number of cycles per power stroke - 2 for a 4 stroke engine. // Engine Variables not read in from config file float RPM; // rpm float Percentage_Power; // Power output as percentage of maximum power output float Manifold_Pressure; // Inches Hg float Fuel_Flow_gals_hr; // USgals/hour float Torque_lbft; // lb-ft float Torque_SI; // Nm float CHT; // Cylinder head temperature deg K float CHT_degF; // Ditto in deg Fahrenheit float Mixture; float Oil_Pressure; // PSI float Oil_Temp; // Deg C float current_oil_temp; // deg K /**** one of these is superfluous !!!!***/ float HP; // Current power output in HP float Power_SI; // Current power output in Watts float RPS; float angular_velocity_SI; // rad/s float Torque_FMEP; // The component of Engine torque due to FMEP (Nm) float Torque_Imbalance; // difference between engine and prop torque float EGT; // Exhaust gas temperature deg K float EGT_degF; // Exhaust gas temperature deg Fahrenheit float volumetric_efficiency; float combustion_efficiency; float equivalence_ratio; // ratio of stoichiometric AFR over actual AFR float thi_sea_level; // the equivalence ratio we would be running at assuming sea level air denisity in the manifold float v_dot_air; // volume flow rate of air into engine - m^3/s float m_dot_air; // mass flow rate of air into engine - kg/s float m_dot_fuel; // mass flow rate of fuel into engine - kg/s float swept_volume; // total engine swept volume - m^3 /********* swept volume or the geometry used to calculate it should be in the config read section surely ??? ******/ float True_Manifold_Pressure; //in Hg - actual manifold gauge pressure float rho_air_manifold; // denisty of air in the manifold - kg/m^3 float R_air; // Gas constant of air (287) UNITS??? float delta_T_exhaust; // Temperature change of exhaust this time step - degK float heat_capacity_exhaust; // exhaust gas specific heat capacity - J/kgK float enthalpy_exhaust; // Enthalpy at current exhaust gas conditions - UNITS??? float Percentage_of_best_power_mixture_power; // Current power as a percentage of what power we would have at the same conditions but at best power mixture float abstract_mixture; //temporary hack float angular_acceleration; //rad/s^2 float FMEP; //Friction Mean Effective Pressure (Pa) // Various bits of housekeeping describing the engines state. bool running; // flag to indicate the engine is running self sustaining bool cranking; // flag to indicate the engine is being cranked int crank_counter; // Number of iterations that the engine has been cranked non-stop bool spark; // flag to indicate a spark is available bool fuel; // flag to indicate fuel is available // Propellor Variables float FGProp1_RPS; // rps float prop_torque; // Nm float prop_thrust; // Newtons double prop_diameter; // meters double blade_angle; // degrees // MEMBER FUNCTIONS // Calculate Engine RPM based on Propellor Lever Position float Calc_Engine_RPM(float Position); // Calculate Manifold Pressure based on throttle lever position // Note that this is simplistic and needs altering to include engine speed effects float Calc_Manifold_Pressure( float LeverPosn, float MaxMan, float MinMan); // Calculate combustion efficiency based on equivalence ratio float Lookup_Combustion_Efficiency(float thi_actual); // Calculate percentage of best power mixture power based on equivalence ratio float Power_Mixture_Correlation(float thi_actual); // Calculate exhaust gas temperature change float Calculate_Delta_T_Exhaust(void); // Calculate cylinder head temperature void Calc_CHT(void); // Calculate exhaust gas temperature void Calc_EGT(void); // Calculate fuel flow in gals/hr void Calc_Fuel_Flow_Gals_Hr(void); // Calculate current percentage power void Calc_Percentage_Power(bool mag_left, bool mag_right); // Calculate Oil Temperature float Calc_Oil_Temp (float oil_temp); // Calculate Oil Pressure float Calc_Oil_Press (float Oil_Temp, float Engine_RPM); // Propeller calculations. void Do_Prop_Calcs(void); public: // ofstream outfile; //constructor FGNewEngine() { // outfile.open("FGNewEngine.dat", ios::out|ios::trunc); } //destructor ~FGNewEngine() { // outfile.close(); } // set initial default values void init(double dt); // update the engine model based on current control positions void update(); inline void set_IAS( float value ) { IAS = value; } inline void set_Throttle_Lever_Pos( float value ) { Throttle_Lever_Pos = value; } inline void set_Propeller_Lever_Pos( float value ) { Propeller_Lever_Pos = value; } inline void set_Mixture_Lever_Pos( float value ) { Mixture_Lever_Pos = value; } // set the magneto switch position inline void set_Magneto_Switch_Pos( int value ) { mag_pos = value; } inline void setStarterFlag( bool flag ) { starter = flag; } // set ambient pressure - takes pounds per square foot inline void set_p_amb( float value ) { p_amb = value * 47.88026; // Convert to Pascals } // set ambient temperature - takes degrees Rankine inline void set_T_amb( float value ) { T_amb = value * 0.555555555556; // Convert to degrees Kelvin } // accessors inline float get_RPM() const { return RPM; } inline float get_Manifold_Pressure() const { return True_Manifold_Pressure; } // inline float get_Rho() const { return Rho; } inline float get_MaxHP() const { return MaxHP; } inline float get_Percentage_Power() const { return Percentage_Power; } inline float get_EGT() const { return EGT_degF; } // Returns EGT in Fahrenheit inline float get_CHT() const { return CHT_degF; } // Note this returns CHT in Fahrenheit inline float get_prop_thrust_SI() const { return prop_thrust; } inline float get_prop_thrust_lbs() const { return (prop_thrust * 0.2248); } inline float get_fuel_flow_gals_hr() const { return (Fuel_Flow_gals_hr); } inline float get_oil_temp() const { return ((current_oil_temp * 1.8) - 459.67); } inline bool getRunningFlag() const { return running; } inline bool getCrankingFlag() const { return cranking; } inline bool getStarterFlag() const { return starter; } }; #endif // _IO360_HXX_