1 /**********************************************************************
3 FILENAME: uiuc_engine.cpp
5 ----------------------------------------------------------------------
7 DESCRIPTION: determine the engine forces and moments
9 ----------------------------------------------------------------------
13 ----------------------------------------------------------------------
15 REFERENCES: simple and c172 models based on portions of
16 c172_engine.c, called from ls_model;
17 cherokee model based on cherokee_engine.c
19 ----------------------------------------------------------------------
21 HISTORY: 01/30/2000 initial release
23 ----------------------------------------------------------------------
25 AUTHOR(S): Bipin Sehgal <bsehgal@uiuc.edu>
26 Jeff Scott <jscott@mail.com>
27 Michael Selig <m-selig@uiuc.edu>
29 ----------------------------------------------------------------------
33 ----------------------------------------------------------------------
37 ----------------------------------------------------------------------
43 ----------------------------------------------------------------------
45 CALLED BY: uiuc_wrapper.cpp
47 ----------------------------------------------------------------------
51 ----------------------------------------------------------------------
53 COPYRIGHT: (C) 2000 by Michael Selig
55 This program is free software; you can redistribute it and/or
56 modify it under the terms of the GNU General Public License
57 as published by the Free Software Foundation.
59 This program is distributed in the hope that it will be useful,
60 but WITHOUT ANY WARRANTY; without even the implied warranty of
61 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
62 GNU General Public License for more details.
64 You should have received a copy of the GNU General Public License
65 along with this program; if not, write to the Free Software
66 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
67 USA or view http://www.gnu.org/copyleft/gpl.html.
69 **********************************************************************/
70 #include <simgear/compiler.h>
72 #include "uiuc_engine.h"
82 Throttle[3] = Throttle_pct;
84 command_list = engineParts -> getCommands();
87 if (command_list.begin() == command_list.end())
89 cerr << "ERROR: Engine not specified. Aircraft cannot fly without the engine" << endl;
94 for (LIST command_line = command_list.begin(); command_line!=command_list.end(); ++command_line)
96 //cout << *command_line << endl;
98 linetoken1 = engineParts -> getToken(*command_line, 1);
99 linetoken2 = engineParts -> getToken(*command_line, 2);
101 switch(engine_map[linetoken2])
103 case simpleSingle_flag:
105 F_X_engine = Throttle[3] * simpleSingleMaxThrust;
110 //c172 engine lines ... looks like 0.83 is just a thrust increase
111 F_X_engine = Throttle[3] * 350 / 0.83;
112 F_Z_engine = Throttle[3] * 4.9 / 0.83;
113 M_m_engine = F_X_engine * 0.734 * cbar;
119 dP = (180.0-117.0)*745.7, // Watts
120 dn = (2700.0-2350.0)/60.0, // d_rpm (I mean d_rps, in seconds)
121 D = 6.17*0.3048, // prop diameter
122 dPh = (58.0-180.0)*745.7, // change of power as function of height
128 J, // advance ratio (ratio of horizontal speed to prop tip speed)
132 eta_engine; // engine efficiency
134 /* assumption -> 0.0 <= Throttle[3] <=1.0 */
135 P = fabs(Throttle[3]) * 180.0 * 745.7; /*180.0*745.7 ->max avail power [W]*/
136 n = dn/dP * (P-117.0*745.7) + 2350.0/60.0;
139 V = (V_rel_wind < 10.0 ? 10.0 : V_rel_wind*0.3048);
142 /* Propeller efficiency */
143 eta_engine = (J < 0.7 ? ((0.8-0.55)/(.7-.3)*(J-0.3) + 0.55) :
144 (J > 0.85 ? ((0.6-0.8)/(1.0-0.85)*(J-0.85) + 0.8) : 0.8));
146 /* power on Altitude */
147 H = Altitude * 0.3048; /* H == Altitude [m] */
148 P *= (dPh/dH * H + 180.0*745.7) / (180.0*745.7);
149 T = eta_engine * P/V; /* Thrust [N] */
151 /*assumption: Engine's line of thrust passes through cg */
152 F_X_engine = T * 0.2248; /* F_X_engine in lb */
162 // end uiuc_engine.cpp