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performance calculations for the Pratt & Whitney R-2180-S1A1-G Twin Hornet aircraft engine
Twin Hornet on display at the Stuart Air show, Florida
Pratt & Whitney R-2180-S1A1-G Twin Hornet air-cooled 14 -cylinder radial engine 1150 [hp](857.6 KW)
gear-driven supercharger, constant power to height : 1830 [m] blower ratio : 10.00 [:1]
introduction : 1937 country : United States importance : *
applications : Douglas DC-4E
normal rating : 1150 [hp](857.6 KW) at 2350 [rpm] at 1830 [m] above sea level
take-off power : 1400 [hp] (1044.0 [KW]) at 2500 [rpm]
reduction : 0.5625 , valvetrain : overhead valves, pushrod operated
weight engine(s) dry with reduction gear : 747.0 [kg] = 0.87 [kg/KW]
General information : development terminated early in favour of the Twin Wasp
engine. Only 30 Twin Hornets were built.
fuel system : fuel type : octane grade no. 100 oil system :
engine starter type :
bore : 146.0 [mm] stroke : 152.0 [mm]
valve inlet area : 32.5 [cm^2] one inlet and one exhaust valve in cylinder head
gasspeed at inlet valve : 43.2 [m/s]
blower speed : 23500 [rpm] , mixture :13.0 :1
compression ratio: 6.66 :1
high octane fuel needed to prevent detonation
stroke volume (Vs displacement): 35.720 [litre]
compression volume (Vc): 6.294 [litre]
total volume (Vt): 41.920 [litre]
overall engine diameter: 137.0 [cm]
calculated engine length: 112.13 [m]
specific power : 24.0 [kW/litre]
torque : 3485 [Nm]
engine weight/volume : 20.9 : [kg/litre]
average piston speed (Cm): 11.9 [m/s]
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intake manifold absolute pressure (MAP) at 1830 [m] altitude Pi : 1.00 [kg/cm2] (28.96 [inHg])
mean engine pressure (M.E.P.) at 1830 [m] altitude Pm : 10.28 [kg/cm2]
compression pressure at 1830 [m] altitude Pc: 10.70 [kg/cm2]
estimated combustion pressure at 1830 [m] Pe : 42.74 [kg/cm2]
exhaust pressure at 1830 [m] Pu : 3.92 [kg/cm^2 ]
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compression-start temperature at 1830 [m] Tic: 338 [°K] (65 [°C])
compression-end temperature at 1830 [m] Tc: 534 [°K] (261 [°C])
average engine wall temperature at 1830 [m] : 476 [K] (202 [°C])
caloric combustion temperature at 1830 [m] Tec: 2296 [°K] (2023 [°C])
polytroph combustion temperature at 1830 [m] Tep : 2134 [°K] (1861 [°C])
estimated combustion temperature at 1830 [m] Te (T4): 2188 [°K] (1915 [°C])
polytrope expansion-end temperature at 1830 [m] Tup: 1139 [°K] (866 [°C])
exhaust stroke end temperature at 1830 [m] Tu: 1097 [°K] (824 [°C])
*********************************************************************************
calculations for take-off/emergency power at sea level
average piston speed : 12.7 [m/s]
gasspeed at inlet valve : 46.0 [m/s]
intake pressure at sea level for Take-off Pi : 1.22 [kg/cm2] (35.40 [inHg])
rich mixture 11.5 : 1 applied for cooling
caloric combustion temperature at sea level Tec: 2115 [°K] (1842 [°C])
insufficient cooling, can run max 2 minutes at this power before overheating
emergency/take off rating at 2500 [rpm] at sea level : 1400 [hp]
Thermal efficiency Nth : 0.378 [ ]
Mechanical efficiency Nm : 0.744 [ ]
Thermo-dynamic efficiency Ntd : 0.281 [ ]
design hours : 1086 [hr] time between overhaul : 376 [hr]
dispersed engine heat by cooling air : 13424.20 [Kcal/minuut/m2]
required cooling surface : 25.63 [m2]
weight cooling ribs : 79.53 [kg]
fuel consumption optimum mixture at 2350.00 [rpm] at 1830 [m]: 249.22 [kg/hr]
specific fuel consumption thermo-dynamic : 214 [gr/epk] = 287 [gr/kwh]
estimated specific fuel consumption (cruise power) at 1830 [m] : 325 [gr/kwh]
specific fuel consumption (volume*rpm at 1 atm MAP) at 2350 [rpm] : 276 [gr/kwh]
estimated specific oil consumption (cruise power) : 13 [gr/kwh]
Literature :
File:Pratt & Whitney R-2180 Twin Wasp Hornet radial engine, Stuart airshow.jpg - Wikimedia Commons
Pratt & Whitney R-2180-A Twin Hornet - Wikipedia
DISCLAIMER Above calculations are based on published data, they must be
regarded as indication not as facts.
Calculated performance and weight may not correspond with actual weights
and performances and are assumptions for which no responsibility can be taken.
Calculations are as accurate as possible, they can be fine-tuned when more data
is available, you are welcome to give suggestions and additional information
so we can improve our program. For copyright on drawings/photographs/
content please mail to below mail address
(c) B van der Zalm 22 January 2022 contact : info.aircraftinvestigation@gmail.com python 3.7.4
notes :
