here's what I have:
1. A turboprop engine with an idle rpm of 19,500 (=52% n1), full power (100% n1) is 37,500 rpm.
2. The reduction ratio is ca. 15:1 which means that, according to my understanding, the propeller rpm is 15 times lower than the engine rpm.
=> at idle power, the rpm should be 19,500/15 = 1300 RPM
Instead, when power is at idle, the propeller rpm is ca. 114 ("fdm/jsbsim/propulsion/engine/propeller-rpm") which is definitely lower than the said reduction ratio of 15:1.
Now I wonder which parameters I have to adjust that the idle propeller rpm is at the correct value.
Thanks in advance
Jonathan
Engine file:
- Code: Select all
<?xml version="1.0"?>
<!--
File: my_engine.xml
Author: AeromatiC++ v 3.2.5
See: http://wiki.flightgear.org/JSBSim_Engines#FGTurboprop
Inputs:
name: PT6A-27
type: Turboprop Engine
power: 620.0 hp
inlet temperature: 725.0 degrees C
overall pressure ratio: 15.0:1
Outputs:
psfc: 0.579 lbs/hr/hp
engine weight: 336.3 lbs
engine length: 4.9 ft
engine diameter: 1.9 ft
-->
<turboprop_engine name="PT6A-27">
<milthrust unit="LBS"> 1388.8 </milthrust>
<idlen1> 52.0 </idlen1>
<maxn1> 101.5 </maxn1>
<maxpower unit="HP"> 620.0 </maxpower>
<psfc unit="LBS/HR/HP"> 0.74 </psfc>
<n1idle_max_delay> 1.2 </n1idle_max_delay>
<maxstartingtime> 0.1 </maxstartingtime>
<startern1> 16.0 </startern1>
<ielumaxtorque unit="FT*LB"> 1536.0 </ielumaxtorque>
<itt_delay> 0.05 </itt_delay>
<betarangeend> 64.0 </betarangeend>
<reversemaxpower> 91.0 </reversemaxpower>
<function name="EnginePowerVC">
<table>
<description> Engine power, function of airspeed and pressure </description>
<independentVar lookup="row">atmosphere/P-sl-psf</independentVar>
<independentVar lookup="column">velocities/ve-kts</independentVar>
<tableData>
0 50 100 150 200 250
503 0.357 0.380 0.400 0.425 0.457 0.486
1048 0.586 0.589 0.600 0.621 0.650 0.686
1328 0.707 0.721 0.731 0.757 0.786 0.821
1496 0.779 0.786 0.808 0.821 0.857 0.900
1684 0.850 0.857 0.874 0.900 0.943 0.979
1896 0.914 0.929 0.946 0.971 1 1.057
2135 1 1.011 1.029 1.043 1.083 1.150
2213 1.029 1.043 1.057 1.079 1.114 1.171
</tableData>
</table>
</function>
<table name="EnginePowerRPM_N1" type="internal">
<description> Engine Power, function of RPM and N1 </description>
<tableData>
0 5 60 86 94 95 96 97 98 99 100 101
0.0 0.0 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4
803.5 0.0 0.4 29.2 166.9 292.1 317.1 350.5 383.8 417.2 442.2 484.0 517.4
1203.0 0.0 0.4 25.0 192.0 333.8 358.8 392.2 421.4 458.9 492.3 534.1 567.4
1604.8 0.0 0.4 4.2 200.3 367.2 396.4 425.6 458.9 496.5 525.7 567.4 600.8
2006.5 0.0 0.1 0.1 187.7 375.5 413.0 438.1 471.4 509.0 542.4 584.1 621.7
2207.4 0.0 0.1 0.1 171.1 367.2 400.5 429.7 467.3 504.9 538.2 579.9 620.0
</tableData>
</table>
<table name="ITT_N1" type="internal">
<description> Inter-Turbine Temperature ITT [deg C] depending on N1 and engine run (0=off / 1=running) </description>
<tableData>
0 1
0 0 0
15 105.1 105.1
60 188.5 546.7
96 283.5 714.8
100 294.4 790.2
</tableData>
</table>
<table name="CombustionEfficiency_N1" type="internal">
<description>Dependency of fuel efficiency coefficient on N1 (and RPM)</description>
<tableData>
90 0.1221
91.2 0.2834
92.2 0.5336
93.4 0.7188
94.1 0.7741
95.2 0.8471
96.5 0.9001
100 1
</tableData>
</table>
</turboprop_engine>
Propeller file:
- Code: Select all
<?xml version="1.0"?>
<!-- Generated by Aero-Matic v 3.3.1
See: http://wiki.flightgear.org/JSBSim_Thrusters#FGPropeller
Inputs:
Horsepower: 620
Max engine rpm: 38100
Prop diameter (ft): 8.5
Prop chord (ft): 0.76
Pitch: variable at 45 inch
Outputs:
Max prop rpm: 2110.0
Gear ratio: 15.0
Cp0: 0.0803575
Ct0: 0.187233
Static thrust (lbs): 2786.61
-->
<propeller version="1.01" name="HARTZELL-T10282H">
<ixx> 25.1034 </ixx>
<diameter unit="IN"> 102 </diameter>
<numblades> 3 </numblades>
<gearratio> 15.0 </gearratio>
<cp_factor> 3 </cp_factor>
<ct_factor> 3 </ct_factor> <!-- Set to match the number of blades -->
<minpitch> 0 </minpitch>
<maxpitch> 87 </maxpitch>
<minrpm> 1650 </minrpm>
<maxrpm> 2110 </maxrpm>
<constantspeed> 1 </constantspeed>
<reversepitch> -15 </reversepitch>
<!-- Thrust coefficient as a function of advance ratio and blade angle -->
<table name="C_THRUST" type="internal">
<tableData>
-15 0 15 30 45 60
0.00 0.0492 0.1132 0.1773 0.2413 0.3054 0.3694
0.05 0.0431 0.1068 0.1704 0.2337 0.2967 0.3596
0.10 0.0371 0.1006 0.1638 0.2264 0.2886 0.3503
0.15 0.0311 0.0946 0.1574 0.2195 0.2808 0.3415
0.20 0.0253 0.0887 0.1513 0.2129 0.2735 0.3332
0.25 0.0194 0.0830 0.1454 0.2066 0.2666 0.3254
0.30 0.0136 0.0774 0.1397 0.2005 0.2600 0.3180
0.35 0.0079 0.0718 0.1342 0.1948 0.2537 0.3110
0.40 0.0021 0.0664 0.1288 0.1893 0.2478 0.3044
0.45 -0.0037 0.0610 0.1236 0.1840 0.2421 0.2981
0.50 -0.0095 0.0557 0.1185 0.1789 0.2368 0.2922
0.55 -0.0154 0.0505 0.1136 0.1740 0.2316 0.2866
0.60 -0.0212 0.0453 0.1088 0.1693 0.2268 0.2813
0.65 -0.0272 0.0401 0.1041 0.1648 0.2221 0.2762
0.70 -0.0331 0.0349 0.0994 0.1604 0.2177 0.2715
0.75 -0.0392 0.0298 0.0949 0.1561 0.2135 0.2670
0.80 -0.0453 0.0247 0.0904 0.1520 0.2094 0.2627
0.85 -0.0515 0.0195 0.0860 0.1481 0.2056 0.2586
0.90 -0.0578 0.0144 0.0817 0.1442 0.2019 0.2548
0.95 -0.0642 0.0092 0.0774 0.1404 0.1983 0.2511
1.00 -0.0706 0.0040 0.0731 0.1368 0.1949 0.2476
1.05 -0.0772 -0.0012 0.0689 0.1332 0.1917 0.2443
1.10 -0.0839 -0.0065 0.0647 0.1297 0.1885 0.2412
1.15 -0.0907 -0.0118 0.0605 0.1263 0.1855 0.2382
1.20 -0.0976 -0.0171 0.0564 0.1230 0.1826 0.2353
1.25 -0.1047 -0.0225 0.0522 0.1197 0.1798 0.2326
1.30 -0.1118 -0.0280 0.0481 0.1165 0.1771 0.2300
1.35 -0.1191 -0.0335 0.0440 0.1133 0.1745 0.2276
1.40 -0.1265 -0.0391 0.0398 0.1102 0.1720 0.2252
1.50 -0.1418 -0.0504 0.0315 0.1040 0.1671 0.2208
1.60 -0.1576 -0.0620 0.0232 0.0981 0.1626 0.2168
1.70 -0.1739 -0.0739 0.0148 0.0922 0.1583 0.2131
1.80 -0.1909 -0.0862 0.0062 0.0864 0.1542 0.2097
1.90 -0.2084 -0.0987 -0.0024 0.0806 0.1502 0.2065
2.00 -0.2266 -0.1116 -0.0112 0.0749 0.1465 0.2036
2.10 -0.2454 -0.1249 -0.0201 0.0692 0.1429 0.2009
2.20 -0.2648 -0.1386 -0.0291 0.0635 0.1393 0.1984
2.30 -0.2848 -0.1526 -0.0384 0.0578 0.1359 0.1960
2.40 -0.3055 -0.1670 -0.0478 0.0521 0.1326 0.1938
</tableData>
</table>
<!-- Power coefficient as a function of advance ratio and blade angle -->
<table name="C_POWER" type="internal">
<tableData>
-15 0 15 30 45 60
0.00 0.0065 0.0313 0.0786 0.1483 0.2405 0.3553
0.05 0.0076 0.0339 0.0828 0.1541 0.2479 0.3643
0.10 0.0082 0.0361 0.0866 0.1596 0.2550 0.3730
0.15 0.0083 0.0379 0.0900 0.1647 0.2619 0.3816
0.20 0.0080 0.0392 0.0931 0.1695 0.2685 0.3900
0.25 0.0072 0.0402 0.0957 0.1740 0.2748 0.3983
0.30 0.0060 0.0407 0.0981 0.1782 0.2810 0.4066
0.35 0.0043 0.0408 0.1001 0.1821 0.2870 0.4147
0.40 0.0022 0.0405 0.1017 0.1858 0.2928 0.4227
0.45 -0.0004 0.0398 0.1031 0.1893 0.2985 0.4308
0.50 -0.0035 0.0387 0.1041 0.1925 0.3041 0.4388
0.55 -0.0070 0.0372 0.1047 0.1955 0.3095 0.4468
0.60 -0.0110 0.0353 0.1051 0.1982 0.3148 0.4547
0.65 -0.0156 0.0330 0.1051 0.2008 0.3200 0.4627
0.70 -0.0206 0.0303 0.1048 0.2031 0.3251 0.4708
0.75 -0.0261 0.0271 0.1042 0.2052 0.3301 0.4788
0.80 -0.0321 0.0236 0.1033 0.2071 0.3350 0.4869
0.85 -0.0386 0.0196 0.1021 0.2088 0.3398 0.4951
0.90 -0.0457 0.0152 0.1005 0.2103 0.3445 0.5033
0.95 -0.0533 0.0103 0.0986 0.2116 0.3492 0.5115
1.00 -0.0614 0.0050 0.0964 0.2126 0.3538 0.5198
1.05 -0.0701 -0.0007 0.0938 0.2135 0.3583 0.5282
1.10 -0.0794 -0.0069 0.0909 0.2141 0.3627 0.5367
1.15 -0.0892 -0.0136 0.0877 0.2146 0.3671 0.5452
1.20 -0.0996 -0.0207 0.0841 0.2148 0.3714 0.5538
1.25 -0.1106 -0.0282 0.0802 0.2148 0.3756 0.5625
1.30 -0.1221 -0.0363 0.0759 0.2146 0.3797 0.5712
1.35 -0.1343 -0.0449 0.0713 0.2142 0.3838 0.5800
1.40 -0.1471 -0.0539 0.0663 0.2135 0.3877 0.5889
1.50 -0.1746 -0.0735 0.0553 0.2116 0.3955 0.6070
1.60 -0.2046 -0.0950 0.0427 0.2087 0.4029 0.6253
1.70 -0.2372 -0.1187 0.0287 0.2049 0.4100 0.6439
1.80 -0.2726 -0.1445 0.0130 0.2001 0.4167 0.6628
1.90 -0.3106 -0.1725 -0.0042 0.1943 0.4230 0.6820
2.00 -0.3514 -0.2027 -0.0230 0.1875 0.4290 0.7014
2.10 -0.3950 -0.2351 -0.0435 0.1797 0.4346 0.7211
2.20 -0.4416 -0.2698 -0.0657 0.1708 0.4397 0.7410
2.30 -0.4910 -0.3069 -0.0896 0.1609 0.4444 0.7611
2.40 -0.5434 -0.3463 -0.1152 0.1498 0.4487 0.7815
</tableData>
</table>
<!-- Thrust effects of helical tip Mach -->
<table name="CT_MACH" type="internal">
<tableData>
0.85 1.0
1.05 0.8
</tableData>
</table>
<!-- Power-required effects of helical tip Mach -->
<table name="CP_MACH" type="internal">
<tableData>
0.85 1.0
1.05 1.8
2.00 1.4
</tableData>
</table>
</propeller>