1 // IO360.hxx - a piston engine model currently for the IO360 engine fitted to the C172
2 // but with the potential to model other naturally aspirated piston engines
3 // given appropriate config input.
5 // Written by David Luff, started 2000.
6 // Based on code by Phil Schubert, started 1999.
8 // This program is free software; you can redistribute it and/or
9 // modify it under the terms of the GNU General Public License as
10 // published by the Free Software Foundation; either version 2 of the
11 // License, or (at your option) any later version.
13 // This program is distributed in the hope that it will be useful, but
14 // WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 // General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
26 #include <simgear/compiler.h>
34 // These constants should probably be moved eventually
35 float CONVERT_CUBIC_INCHES_TO_METERS_CUBED;
36 float CONVERT_HP_TO_WATTS;
38 // Properties of working fluids
39 float Cp_air; // J/KgK
40 float Cp_fuel; // J/KgK
41 float calorific_value_fuel; // W/Kg
42 float rho_fuel; // kg/m^3
43 float rho_air; // kg/m^3
46 float p_amb_sea_level; // Sea level ambient pressure in Pascals
47 float p_amb; // Ambient pressure at current altitude in Pascals
48 float T_amb; // ditto deg Kelvin
51 float Throttle_Lever_Pos; // 0 = Closed, 100 = Fully Open
52 float Propeller_Lever_Pos; // 0 = Full Course 100 = Full Fine
53 float Mixture_Lever_Pos; // 0 = Idle Cut Off 100 = Full Rich
54 int mag_pos; // 0=off, 1=left, 2=right, 3=both.
61 // Engine Specific Variables that should be read in from a config file
62 float MaxHP; // Horsepower
63 float displacement; // Cubic inches
64 float displacement_SI; //m^3 (derived from above rather than read in)
65 float engine_inertia; //kg.m^2
66 float prop_inertia; //kg.m^2
67 float Max_Fuel_Flow; // Units??? Do we need this variable any more??
69 // 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.
70 float Max_Manifold_Pressure; // inches Hg - typical manifold pressure at full throttle and typical max rpm
71 float Min_Manifold_Pressure; // inches Hg - typical manifold pressure at idle (closed throttle)
72 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.
73 float Min_RPM; // rpm - possibly redundant ???
74 float Mag_Derate_Percent; // Percentage reduction in power when mags are switched from 'both' to either 'L' or 'R'
75 float Gear_Ratio; // Gearing between engine and propellor
76 float n_R; // Number of cycles per power stroke - 2 for a 4 stroke engine.
78 // Engine Variables not read in from config file
80 float Percentage_Power; // Power output as percentage of maximum power output
81 float Manifold_Pressure; // Inches Hg
82 float Fuel_Flow_gals_hr; // USgals/hour
83 float Torque_lbft; // lb-ft
84 float Torque_SI; // Nm
85 float CHT; // Cylinder head temperature deg K
86 float CHT_degF; // Ditto in deg Fahrenheit
88 float Oil_Pressure; // PSI
89 float Oil_Temp; // Deg C
90 float current_oil_temp; // deg K
91 /**** one of these is superfluous !!!!***/
92 float HP; // Current power output in HP
93 float Power_SI; // Current power output in Watts
95 float angular_velocity_SI; // rad/s
96 float Torque_FMEP; // The component of Engine torque due to FMEP (Nm)
97 float Torque_Imbalance; // difference between engine and prop torque
98 float EGT; // Exhaust gas temperature deg K
99 float EGT_degF; // Exhaust gas temperature deg Fahrenheit
100 float volumetric_efficiency;
101 float combustion_efficiency;
102 float equivalence_ratio; // ratio of stoichiometric AFR over actual AFR
103 float thi_sea_level; // the equivalence ratio we would be running at assuming sea level air denisity in the manifold
104 float v_dot_air; // volume flow rate of air into engine - m^3/s
105 float m_dot_air; // mass flow rate of air into engine - kg/s
106 float m_dot_fuel; // mass flow rate of fuel into engine - kg/s
107 float swept_volume; // total engine swept volume - m^3
108 /********* swept volume or the geometry used to calculate it should be in the config read section surely ??? ******/
109 float True_Manifold_Pressure; //in Hg - actual manifold gauge pressure
110 float rho_air_manifold; // denisty of air in the manifold - kg/m^3
111 float R_air; // Gas constant of air (287) UNITS???
112 float delta_T_exhaust; // Temperature change of exhaust this time step - degK
113 float heat_capacity_exhaust; // exhaust gas specific heat capacity - J/kgK
114 float enthalpy_exhaust; // Enthalpy at current exhaust gas conditions - UNITS???
115 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
116 float abstract_mixture; //temporary hack
117 float angular_acceleration; //rad/s^2
118 float FMEP; //Friction Mean Effective Pressure (Pa)
120 // Various bits of housekeeping describing the engines state.
121 bool running; // flag to indicate the engine is running self sustaining
122 bool cranking; // flag to indicate the engine is being cranked
123 int crank_counter; // Number of iterations that the engine has been cranked non-stop
124 bool spark; // flag to indicate a spark is available
125 bool fuel; // flag to indicate fuel is available
127 // Propellor Variables
128 float FGProp1_RPS; // rps
129 float prop_torque; // Nm
130 float prop_thrust; // Newtons
131 double prop_diameter; // meters
132 double blade_angle; // degrees
137 // Calculate Engine RPM based on Propellor Lever Position
138 float Calc_Engine_RPM(float Position);
140 // Calculate Manifold Pressure based on throttle lever position
141 // Note that this is simplistic and needs altering to include engine speed effects
142 float Calc_Manifold_Pressure( float LeverPosn, float MaxMan, float MinMan);
144 // Calculate combustion efficiency based on equivalence ratio
145 float Lookup_Combustion_Efficiency(float thi_actual);
147 // Calculate percentage of best power mixture power based on equivalence ratio
148 float Power_Mixture_Correlation(float thi_actual);
150 // Calculate exhaust gas temperature change
151 float Calculate_Delta_T_Exhaust(void);
153 // Calculate cylinder head temperature
156 // Calculate exhaust gas temperature
159 // Calculate fuel flow in gals/hr
160 void Calc_Fuel_Flow_Gals_Hr(void);
162 // Calculate current percentage power
163 void Calc_Percentage_Power(bool mag_left, bool mag_right);
165 // Calculate Oil Temperature
166 float Calc_Oil_Temp (float oil_temp);
168 // Calculate Oil Pressure
169 float Calc_Oil_Press (float Oil_Temp, float Engine_RPM);
171 // Propeller calculations.
172 void Do_Prop_Calcs(void);
180 // outfile.open("FGNewEngine.dat", ios::out|ios::trunc);
188 // set initial default values
189 void init(double dt);
191 // update the engine model based on current control positions
194 inline void set_IAS( float value ) { IAS = value; }
195 inline void set_Throttle_Lever_Pos( float value ) {
196 Throttle_Lever_Pos = value;
198 inline void set_Propeller_Lever_Pos( float value ) {
199 Propeller_Lever_Pos = value;
201 inline void set_Mixture_Lever_Pos( float value ) {
202 Mixture_Lever_Pos = value;
204 // set the magneto switch position
205 inline void set_Magneto_Switch_Pos( int value ) {
208 inline void setStarterFlag( bool flag ) {
211 // set ambient pressure - takes pounds per square foot
212 inline void set_p_amb( float value ) {
213 p_amb = value * 47.88026;
214 // Convert to Pascals
216 // set ambient temperature - takes degrees Rankine
217 inline void set_T_amb( float value ) {
218 T_amb = value * 0.555555555556;
219 // Convert to degrees Kelvin
223 inline float get_RPM() const { return RPM; }
224 inline float get_Manifold_Pressure() const { return True_Manifold_Pressure; }
225 // inline float get_Rho() const { return Rho; }
226 inline float get_MaxHP() const { return MaxHP; }
227 inline float get_Percentage_Power() const { return Percentage_Power; }
228 inline float get_EGT() const { return EGT_degF; } // Returns EGT in Fahrenheit
229 inline float get_CHT() const { return CHT_degF; } // Note this returns CHT in Fahrenheit
230 inline float get_prop_thrust_SI() const { return prop_thrust; }
231 inline float get_prop_thrust_lbs() const { return (prop_thrust * 0.2248); }
232 inline float get_fuel_flow_gals_hr() const { return (Fuel_Flow_gals_hr); }
233 inline float get_oil_temp() const { return ((current_oil_temp * 1.8) - 459.67); }
234 inline bool getRunningFlag() const { return running; }
235 inline bool getCrankingFlag() const { return cranking; }
236 inline bool getStarterFlag() const { return starter; }
240 #endif // _IO360_HXX_