162 lines
5.1 KiB
C++
162 lines
5.1 KiB
C++
/**********************************************************************
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FILENAME: uiuc_engine.cpp
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----------------------------------------------------------------------
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DESCRIPTION: determine the engine forces and moments
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----------------------------------------------------------------------
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STATUS: alpha version
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----------------------------------------------------------------------
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REFERENCES: simple and c172 models based on portions of
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c172_engine.c, called from ls_model;
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cherokee model based on cherokee_engine.c
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----------------------------------------------------------------------
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HISTORY: 01/30/2000 initial release
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----------------------------------------------------------------------
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AUTHOR(S): Bipin Sehgal <bsehgal@uiuc.edu>
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Jeff Scott <jscott@mail.com>
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Michael Selig <m-selig@uiuc.edu>
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----------------------------------------------------------------------
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VARIABLES:
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----------------------------------------------------------------------
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INPUTS: -engine model
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----------------------------------------------------------------------
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OUTPUTS: -F_X_engine
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-F_Z_engine
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-M_m_engine
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----------------------------------------------------------------------
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CALLED BY: uiuc_wrapper.cpp
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----------------------------------------------------------------------
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CALLS TO: none
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----------------------------------------------------------------------
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COPYRIGHT: (C) 2000 by Michael Selig
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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
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as published by the Free Software Foundation.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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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., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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USA or view http://www.gnu.org/copyleft/gpl.html.
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**********************************************************************/
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#include <simgear/compiler.h>
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#include "uiuc_engine.h"
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SG_USING_STD(cerr);
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void uiuc_engine()
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{
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stack command_list;
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string linetoken1;
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string linetoken2;
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Throttle[3] = Throttle_pct;
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command_list = engineParts -> getCommands();
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/*
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if (command_list.begin() == command_list.end())
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{
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cerr << "ERROR: Engine not specified. Aircraft cannot fly without the engine" << endl;
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exit(-1);
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}
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*/
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for (LIST command_line = command_list.begin(); command_line!=command_list.end(); ++command_line)
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{
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//cout << *command_line << endl;
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linetoken1 = engineParts -> getToken(*command_line, 1);
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linetoken2 = engineParts -> getToken(*command_line, 2);
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switch(engine_map[linetoken2])
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{
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case simpleSingle_flag:
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{
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F_X_engine = Throttle[3] * simpleSingleMaxThrust;
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break;
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}
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case c172_flag:
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{
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//c172 engine lines ... looks like 0.83 is just a thrust increase
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F_X_engine = Throttle[3] * 350 / 0.83;
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F_Z_engine = Throttle[3] * 4.9 / 0.83;
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M_m_engine = F_X_engine * 0.734 * cbar;
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break;
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}
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case cherokee_flag:
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{
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static float
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dP = (180.0-117.0)*745.7, // Watts
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dn = (2700.0-2350.0)/60.0, // d_rpm (I mean d_rps, in seconds)
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D = 6.17*0.3048, // prop diameter
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dPh = (58.0-180.0)*745.7, // change of power as function of height
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dH = 25000.0*0.3048;
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float
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n, // [rps]
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H, // altitude [m]
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J, // advance ratio (ratio of horizontal speed to prop tip speed)
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T, // thrust [N]
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V, // velocity [m/s]
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P, // power [W]
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eta_engine; // engine efficiency
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/* assumption -> 0.0 <= Throttle[3] <=1.0 */
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P = fabs(Throttle[3]) * 180.0 * 745.7; /*180.0*745.7 ->max avail power [W]*/
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n = dn/dP * (P-117.0*745.7) + 2350.0/60.0;
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/* V [m/s] */
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V = (V_rel_wind < 10.0 ? 10.0 : V_rel_wind*0.3048);
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J = V / n / D;
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/* Propeller efficiency */
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eta_engine = (J < 0.7 ? ((0.8-0.55)/(.7-.3)*(J-0.3) + 0.55) :
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(J > 0.85 ? ((0.6-0.8)/(1.0-0.85)*(J-0.85) + 0.8) : 0.8));
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/* power on Altitude */
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H = Altitude * 0.3048; /* H == Altitude [m] */
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P *= (dPh/dH * H + 180.0*745.7) / (180.0*745.7);
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T = eta_engine * P/V; /* Thrust [N] */
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/*assumption: Engine's line of thrust passes through cg */
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F_X_engine = T * 0.2248; /* F_X_engine in lb */
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F_Y_engine = 0.0;
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F_Z_engine = 0.0;
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break;
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}
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};
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}
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return;
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}
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// end uiuc_engine.cpp
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