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performance calculations for the Oberursel UR.II WWI aero engine
Oberursel UR.II air-cooled 9 -cylinder two-valve rotary engine 110 [hp](82.0 KW)
German engine rating : 111.5 [PS]
introduction : July 1917 country : Germany importance : ***
applications : Fokker Dr.I, Fokker D.VIII, Fokker D.VI
general information : Straight copy of the France Le Rhone 9j 110 hp rotary engine.
normal rating : 110 [hp](82.0 KW) at 1100 [rpm] at 1000 [m] above sea level
no reduction, direct drive, valvetrain : mechanical operated in and exhaust valve.
One rod operating both inlet and exhaust valve
fuel system : oil system :
weight engine(s) dry : 151.7 [kg] = 1.85 [kg/KW]
bore : 112.0 [mm] stroke : 175.0 [mm]
Mechanical efficiency/mean pressure correction factor : 0.707 [ ]
valve inlet area : 19.1 [cm^2] one inlet and one exhaust valve in cylinder head
gasspeed at inlet valve : 23.2 [m/s]
throttle : 93 /100 open, mixture :13.0 :1
compression ratio: 5.00 :1
published volume (displacement): 15.517 [litre]
compression volume (Vc): 3.879 [litre]
total volume (Vt): 19.396 [litre]
diam. engine : 127 [cm]
power / stroke volume (litervermogen Nl): 5.3 [kW/litre]
torque : 712 [Nm]
engine weight/volume : 9.8 : [kg/litre]
average piston speed (Cm): 6.4 [m/s]
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intake pressure at 1000 [m] altitude Pi : 0.89 [kg/cm2]
mean engine pressure (M.E.P.) at 1000 [m] altitude Pm : 5.58 [kg/cm2]
compression pressure at 1000 [m] altitude Pc: 6.63 [kg/cm2]
estimated combustion pressure at 1000 [m] Pe : 26.54 [kg/cm2]
exhaust pressure at 1000 [m] Pu : 3.49 [kg/cm^2 ]
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compression-start temperature at 1000 [m] Tic: 401 [°K] (128 [°C])
compression-end temperature at 1000 [m] Tc: 568 [°K] (295 [°C])
caloric combustion temperature at 1000 [m] Tec: 2268 [°K] (1995 [°C])
polytroph combustion temperature at 1000 [m] Tep : 2271 [°K] (1998 [°C])
estimated combustion temperature at 1000 [m] Te (T4): 2239 [°K] (1966 [°C])
polytrope expansion-end temperature at 1000 [m] Tup: 1234 [°K] (960 [°C])
exhaust stroke end temperature at 1000 [m] Tu: 1048 [°K] (775 [°C])
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bruto emergency/take off rating at 1211 [rpm] at sea level : 119 [hp]
Thermal efficiency Nth : 0.331 [ ]
Mechanical efficiency Nm : 0.666 [ ]
Thermo-dynamic efficiency Ntd : 0.220 [ ]
design hours : 1111 time between overhaul : 44
fuel consumption optimum mixture at 1100.00 [rpm] at 1000 [m]: 30.99 [kg/hr]
specific fuel consumption thermo-dynamic : 273 [gr/epk] = 366 [gr/kwh]
estimated specific fuel consumption (cruise power) at 1000 [m] optimum mixture : 370 [gr/kwh]
estimated sfc (cruise power) at 3000 [m] rich mixture : 376 [gr/kwh]
specific fuel consumption at 1000 [m] at 1100 [rpm] with mixture :13.0 :1 : 378 [gr/kwh]
estimated specific oil consumption (cruise power) : 75 [gr/kwh]
Literature :
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 24 June 2020 contact : info.aircraftinvestigation@gmail.com python 3.7.4