247 lines
9.7 KiB
C++
247 lines
9.7 KiB
C++
// IO360.hxx - a piston engine model currently for the IO360 engine fitted to the C172
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// but with the potential to model other naturally aspirated piston engines
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// given appropriate config input.
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//
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// Written by David Luff, started 2000.
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// Based on code by Phil Schubert, started 1999.
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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#ifndef _IO360_HXX_
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#define _IO360_HXX_
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#include <simgear/compiler.h>
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#include <math.h>
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#include STL_IOSTREAM
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#include STL_FSTREAM
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#if !defined(SG_HAVE_NATIVE_SGI_COMPILERS)
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SG_USING_STD(ofstream);
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#endif
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class FGNewEngine {
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private:
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// These constants should probably be moved eventually
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float CONVERT_CUBIC_INCHES_TO_METERS_CUBED;
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float CONVERT_HP_TO_WATTS;
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// Properties of working fluids
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float Cp_air; // J/KgK
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float Cp_fuel; // J/KgK
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float calorific_value_fuel; // W/Kg
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float rho_fuel; // kg/m^3
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float rho_air; // kg/m^3
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// environment inputs
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float p_amb_sea_level; // Sea level ambient pressure in Pascals
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float p_amb; // Ambient pressure at current altitude in Pascals
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float T_amb; // ditto deg Kelvin
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// Control inputs
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float Throttle_Lever_Pos; // 0 = Closed, 100 = Fully Open
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float Propeller_Lever_Pos; // 0 = Full Course 100 = Full Fine
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float Mixture_Lever_Pos; // 0 = Idle Cut Off 100 = Full Rich
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int mag_pos; // 0=off, 1=left, 2=right, 3=both.
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bool starter;
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//misc
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float IAS;
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double time_step;
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// Engine Specific Variables that should be read in from a config file
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float MaxHP; // Horsepower
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float displacement; // Cubic inches
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float displacement_SI; //m^3 (derived from above rather than read in)
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float engine_inertia; //kg.m^2
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float prop_inertia; //kg.m^2
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float Max_Fuel_Flow; // Units??? Do we need this variable any more??
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// 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.
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float Max_Manifold_Pressure; // inches Hg - typical manifold pressure at full throttle and typical max rpm
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float Min_Manifold_Pressure; // inches Hg - typical manifold pressure at idle (closed throttle)
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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.
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float Min_RPM; // rpm - possibly redundant ???
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float Mag_Derate_Percent; // Percentage reduction in power when mags are switched from 'both' to either 'L' or 'R'
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float Gear_Ratio; // Gearing between engine and propellor
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float n_R; // Number of cycles per power stroke - 2 for a 4 stroke engine.
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// Engine Variables not read in from config file
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float RPM; // rpm
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float Percentage_Power; // Power output as percentage of maximum power output
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float Manifold_Pressure; // Inches Hg
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float Fuel_Flow_gals_hr; // USgals/hour
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float Torque_lbft; // lb-ft
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float Torque_SI; // Nm
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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 Mixture;
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float Oil_Pressure; // PSI
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float Oil_Temp; // Deg C
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float current_oil_temp; // deg K
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/**** one of these is superfluous !!!!***/
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float HP; // Current power output in HP
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float Power_SI; // Current power output in Watts
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float RPS;
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float angular_velocity_SI; // rad/s
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float Torque_FMEP; // The component of Engine torque due to FMEP (Nm)
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float Torque_Imbalance; // difference between engine and prop torque
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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 volumetric_efficiency;
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float combustion_efficiency;
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float equivalence_ratio; // ratio of stoichiometric AFR over actual AFR
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float thi_sea_level; // the equivalence ratio we would be running at assuming sea level air denisity in the manifold
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float v_dot_air; // volume flow rate of air into engine - m^3/s
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float m_dot_air; // mass flow rate of air into engine - kg/s
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float m_dot_fuel; // mass flow rate of fuel into engine - kg/s
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float swept_volume; // total engine swept volume - m^3
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/********* swept volume or the geometry used to calculate it should be in the config read section surely ??? ******/
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float True_Manifold_Pressure; //in Hg - actual manifold gauge pressure
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float rho_air_manifold; // denisty of air in the manifold - kg/m^3
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float R_air; // Gas constant of air (287) UNITS???
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float delta_T_exhaust; // Temperature change of exhaust this time step - degK
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float heat_capacity_exhaust; // exhaust gas specific heat capacity - J/kgK
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float enthalpy_exhaust; // Enthalpy at current exhaust gas conditions - UNITS???
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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
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float abstract_mixture; //temporary hack
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float angular_acceleration; //rad/s^2
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float FMEP; //Friction Mean Effective Pressure (Pa)
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// Various bits of housekeeping describing the engines state.
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bool running; // flag to indicate the engine is running self sustaining
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bool cranking; // flag to indicate the engine is being cranked
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int crank_counter; // Number of iterations that the engine has been cranked non-stop
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bool spark; // flag to indicate a spark is available
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bool fuel; // flag to indicate fuel is available
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// Propellor Variables
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float FGProp1_RPS; // rps
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float prop_torque; // Nm
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float prop_thrust; // Newtons
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double prop_diameter; // meters
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double blade_angle; // degrees
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// MEMBER FUNCTIONS
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// Calculate Engine RPM based on Propellor Lever Position
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float Calc_Engine_RPM(float Position);
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// Calculate Manifold Pressure based on throttle lever position
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// Note that this is simplistic and needs altering to include engine speed effects
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float Calc_Manifold_Pressure( float LeverPosn, float MaxMan, float MinMan);
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// Calculate combustion efficiency based on equivalence ratio
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float Lookup_Combustion_Efficiency(float thi_actual);
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// Calculate percentage of best power mixture power based on equivalence ratio
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float Power_Mixture_Correlation(float thi_actual);
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// Calculate exhaust gas temperature change
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float Calculate_Delta_T_Exhaust(void);
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// Calculate cylinder head temperature
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void Calc_CHT(void);
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// Calculate exhaust gas temperature
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void Calc_EGT(void);
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// Calculate fuel flow in gals/hr
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void Calc_Fuel_Flow_Gals_Hr(void);
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// Calculate current percentage power
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void Calc_Percentage_Power(bool mag_left, bool mag_right);
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// Calculate Oil Temperature
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float Calc_Oil_Temp (float oil_temp);
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// Calculate Oil Pressure
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float Calc_Oil_Press (float Oil_Temp, float Engine_RPM);
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// Propeller calculations.
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void Do_Prop_Calcs(void);
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public:
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// ofstream outfile;
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//constructor
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FGNewEngine() {
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// outfile.open("FGNewEngine.dat", ios::out|ios::trunc);
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}
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//destructor
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~FGNewEngine() {
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// outfile.close();
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}
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// set initial default values
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void init(double dt);
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// update the engine model based on current control positions
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void update();
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inline void set_IAS( float value ) { IAS = value; }
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inline void set_Throttle_Lever_Pos( float value ) {
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Throttle_Lever_Pos = value;
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}
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inline void set_Propeller_Lever_Pos( float value ) {
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Propeller_Lever_Pos = value;
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}
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inline void set_Mixture_Lever_Pos( float value ) {
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Mixture_Lever_Pos = value;
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}
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// set the magneto switch position
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inline void set_Magneto_Switch_Pos( int value ) {
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mag_pos = value;
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}
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inline void setStarterFlag( bool flag ) {
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starter = flag;
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}
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// set ambient pressure - takes pounds per square foot
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inline void set_p_amb( float value ) {
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p_amb = value * 47.88026;
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// Convert to Pascals
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}
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// set ambient temperature - takes degrees Rankine
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inline void set_T_amb( float value ) {
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T_amb = value * 0.555555555556;
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// Convert to degrees Kelvin
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}
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// accessors
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inline float get_RPM() const { return RPM; }
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inline float get_Manifold_Pressure() const { return True_Manifold_Pressure; }
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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_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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inline float get_prop_thrust_lbs() const { return (prop_thrust * 0.2248); }
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inline float get_fuel_flow_gals_hr() const { return (Fuel_Flow_gals_hr); }
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inline float get_oil_temp() const { return ((current_oil_temp * 1.8) - 459.67); }
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inline bool getRunningFlag() const { return running; }
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inline bool getCrankingFlag() const { return cranking; }
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inline bool getStarterFlag() const { return starter; }
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};
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#endif // _IO360_HXX_
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