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performance calculations for the Pratt & Whitney R-2800-CA15 Double Wasp aircraft engine

Pratt & Whitney R-2800-CA15 Double Wasp air-cooled 18 -cylinder double row radial engine 2100 [hp](1566.0 KW)

gear-driven supercharger, constant power to height : 4000 [m] blower ratio : 8.00 [:1]

introduction : 1945 country : USA importance : ****

applications : Douglas DC-6

normal rating : 2100 [hp](1566.0 KW) at 2700 [rpm] at 4000 [m] above sea level

take-off power : 2400 [hp] (1789.7 [KW]) at 2800 [rpm]

reduction : 0.4 , valvetrain : overhead valves, pushrod operated

weight engine(s) dry with reduction gear : 1073.0 [kg] = 0.69 [kg/KW]

General information : with water injection

fuel system : fuel type : octane grade no. 91 oil system :

engine starter type :

bore : 146.1 [mm] stroke : 152.4 [mm]

valve inlet area : 32.6 [cm^2] one inlet and one exhaust valve in cylinder head

gasspeed at inlet valve : 49.6 [m/s]

blower speed : 21600 [rpm] , mixture :13.0 :1

compression ratio: 6.70 :1

high octane fuel needed tp prevent detonation

stroke volume (Vs displacement): 45.960 [litre]

compression volume (Vc): 8.063 [litre]

total volume (Vt): 54.019 [litre]

overall engine diameter: 134.0 [cm]

calculated engine length: 112.17 [m]

specific power : 34.1 [kW/litre]

torque : 5538 [Nm]

engine weight/volume : 23.3 : [kg/litre]

average piston speed (Cm): 13.7 [m/s]

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intake manifold absolute pressure (MAP) at 4000 [m] altitude Pi (ata.) : 1.01 [kg/cm2]

(29.19 [inHg])

mean engine pressure (M.E.P.) at 4000 [m] altitude Pm : 12.90 [kg/cm2]

compression pressure at 4000 [m] altitude Pc: 10.87 [kg/cm2]

estimated combustion pressure at 4000 [m] Pe : 43.40 [kg/cm2]

exhaust pressure at 4000 [m] Pu : 3.95 [kg/cm^2 ]

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compression-start temperature at 4000 [m] Tic: 339 [°K] (66 [°C])

compression-end temperature at 4000 [m] Tc: 538 [°K] (265 [°C])

average engine wall temperature at 4000 [m] : 476 [K] (202 [°C])

caloric combustion temperature at 4000 [m] Tec: 2302 [°K] (2029 [°C])

polytroph combustion temperature at 4000 [m] Tep : 2150 [°K] (1877 [°C])

estimated combustion temperature at 4000 [m] Te (T4): 2199 [°K] (1926 [°C])

polytrope expansion-end temperature at 4000 [m] Tup: 1145 [°K] (872 [°C])

exhaust stroke end temperature at 4000 [m] Tu: 1109 [°K] (836 [°C])

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calculations for take-off/emergency power at sea level

average piston speed : 14.2 [m/s]

gasspeed at inlet valve : 51.5 [m/s]

intake pressure at sea level for Take-off Pi : 1.14 [kg/cm2] (33.04 [inHg])

rich mixture 11.5 : 1 applied for cooling > carburettor adjustable in flight by the pilot

caloric combustion temperature at sea level Tec: 2118 [°K] (1845 [°C])

insufficient cooling, can run max 2 minutes at this power before overheating

emergency/take off rating at 2800 [rpm] at sea level : 2403 [hp]

Thermal efficiency Nth : 0.378 [ ]

Mechanical efficiency Nm : 0.738 [ ]

Thermo-dynamic efficiency Ntd : 0.279 [ ]

design hours : 929 [hr] time between overhaul : 403 [hr]

dispersed engine heat by cooling air : 19977.30 [Kcal/minuut/m2]

required cooling surface : 32.42 [m2]

weight cooling ribs : 101.52 [kg]

fuel consumption optimum mixture at 2700.00 [rpm] at 4000 [m]: 372.32 [kg/hr]

specific fuel consumption thermo-dynamic : 215 [gr/epk] = 289 [gr/kwh]

estimated specific fuel consumption (cruise power) at 4000 [m] : 285 [gr/kwh]

specific fuel consumption (volume*rpm at 1 atm MAP) at 2700 [rpm] : 224 [gr/kwh]

estimated specific oil consumption (cruise power) : 9 [gr/kwh]

Literature :

Jane’s fighting aircraft WWII page 311

Aero engines – Bill Gunston page 131

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