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performance calculations for the De Haviland Gipsy Twelve aircraft engine

De Haviland Gipsy Twelve air-cooled 12 -cylinder V-engine 415 [hp](309.5 KW)

gear-driven supercharger, constant power to height : 2400 [m] blower ratio : 7.14 [:1]

introduction : 1938 country : UK importance : **

applications : De Havilland D.H.91 Albatross

design : Frank Halford

normal rating : 415 [hp](309.5 KW) at 2450 [rpm] at 2400 [m] above sea level

take-off power : 510 [hp] (380.3 [KW]) at 2600 [rpm]

reduction : 0.667 , valvetrain : OHV

weight engine(s) dry with reduction gear : 480.0 [kg] = 1.55 [kg/KW]

General information : only 95 built

fuel system : fuel type : octane grade no. 87 oil system :

engine starter type :

bore : 118.0 [mm] stroke : 140.0 [mm]

valve inlet area : 21.3 [cm^2] one inlet and one exhaust valve in cylinder head

gasspeed at inlet valve : 41.4 [m/s]

blower speed : 17493 [rpm] , mixture :13.0 :1

compression ratio: 6.00 :1

stroke volume (Vs displacement): 18.372 [litre]

compression volume (Vc): 3.674 [litre]

total volume (Vt): 22.047 [litre]

calculated engine height : 93 [cm] engine width :90 [cm]

calculated engine length: 1.06 [m]

specific power : 16.8 [kW/litre]

torque : 1206 [Nm]

engine weight/volume : 26.1 : [kg/litre]

average piston speed (Cm): 11.4 [m/s]

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intake manifold absolute pressure (MAP) at 2400 [m] altitude Pi (ata.) : 1.24 [kg/cm2]

(36.03 [inHg])

mean engine pressure (M.E.P.) at 2400 [m] altitude Pm : 8.86 [kg/cm2]

compression pressure at 2400 [m] altitude Pc: 11.68 [kg/cm2]

estimated combustion pressure at 2400 [m] Pe : 46.66 [kg/cm2]

exhaust pressure at 2400 [m] Pu : 4.88 [kg/cm^2 ]

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compression-start temperature at 2400 [m] Tic: 353 [°K] (80 [°C])

compression-end temperature at 2400 [m] Tc: 544 [°K] (271 [°C])

average engine wall temperature at 2400 [m] : 476 [K] (202 [°C])

caloric combustion temperature at 2400 [m] Tec: 2468 [°K] (2195 [°C])

polytroph combustion temperature at 2400 [m] Tep : 2172 [°K] (1899 [°C])

estimated combustion temperature at 2400 [m] Te (T4): 2300 [°K] (2027 [°C])

polytrope expansion-end temperature at 2400 [m] Tup: 1233 [°K] (960 [°C])

exhaust stroke end temperature at 2400 [m] Tu: 1195 [°K] (921 [°C])

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calculations for take-off/emergency power at sea level

average piston speed : 12.1 [m/s]

gasspeed at inlet valve : 43.9 [m/s]

intake pressure at sea level for Take-off Pi : 1.06 [kg/cm2] (30.62 [inHg])

caloric combustion temperature at sea level Tec: 2316 [°K] (2042 [°C])

high burn temperature > risk of overheating max 2 min max power setting at sea

level

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

emergency/take off rating at 2600 [rpm] at sea level : 510 [hp]

Thermal efficiency Nth : 0.361 [ ]

Mechanical efficiency Nm : 0.722 [ ]

Thermo-dynamic efficiency Ntd : 0.261 [ ]

design hours : 1183 [hr] time between overhaul : 321 [hr]

dispersed engine heat by cooling air : 8053.13 [Kcal/minuut/m2]

required cooling surface : 9.24 [m2]

weight cooling ribs : 27.02 [kg]

fuel consumption optimum mixture at 2450.00 [rpm] at 2400 [m]: 146.99 [kg/hr]

specific fuel consumption thermo-dynamic : 231 [gr/epk] = 309 [gr/kwh]

estimated specific fuel consumption (cruise power) at 2400 [m] : 310 [gr/kwh]

specific fuel consumption (volume*rpm at 1 atm MAP) at 2450 [rpm] : 411 [gr/kwh]

estimated specific oil consumption (cruise power) : 17 [gr/kwh]

Literature :

Jane’s all the world aircraft 1938 page 21d,22d

Aero engines page 55

de Havilland Gipsy Twelve - 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

Gipsy Twelve on display at the Science Museum, London

(c) B van der Zalm 22 January 2022 contact : info.aircraftinvestigation@gmail.com python 3.7.4