Oberursel U.0 rating | aircraft investigation info

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performance calculations for the Oberursel U.O WWI aero engine

Oberursel U.O air-cooled 7 -cylinder atmospheric inlet-valve rotary engine 80 [hp](59.7 KW)

German engine rating : 81.1 [PS]

introduction : June 1915 country : Germany importance : ***

applications : Fokker E.I, Pfalz E.I

normal rating : 80 [hp](59.7 KW) at 1250 [rpm] at 0 [m] above sea level

no reduction, direct drive, valvetrain : SOHC

general information :

The Gnome Lambda seven-cylinder 80 hp rotary engine was also produced by the Oberursel firm as the Oberursel U.0 Umlaufmotor (the generic German term for a rotary engine) as their first-ever powerplant for German military aircraft, and was used on the initial versions of the famous Fokker Eindecker fighter, the Fokker E.I.

fuel system : oil system :

weight engine(s) dry : 118.1 [kg] = 1.98 [kg/KW]

bore : 124.0 [mm] stroke : 140.0 [mm]

valve inlet area : 29.5 [cm^2] one atmospheric inlet valve in piston head, one outlet valve in the cylinder head

gasspeed at inlet valve : 16.8 [m/s]

rich fuel mixture trough atmospheric inlet valve mixed with ambient air from exhaust valve give lean mixture and will be more rich at altitude

throttle : 93 /100 open, mixture :14.0 :1

calculated compression ratio : 3.75 : 1

stroke volume (Vs) : 11.835 [litre]

compression volume (Vc): 4.306 [litre]

total volume (Vt): 16.141 [litre]

diam. engine : 109 [cm]

power / stroke volume (litervermogen Nl): 5.0 [kW/litre]

torque : 456 [Nm]

engine weight/volume : 10.0 : [kg/litre]

average piston speed (Cm): 5.8 [m/s]

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intake pressure at 0 [m] altitude Pi : 0.98 [kg/cm2]

mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 4.46 [kg/cm2]

compression pressure at 0 [m] altitude Pc: 5.18 [kg/cm2]

estimated combustion pressure at 0 [m] Pe : 19.95 [kg/cm2]

estimated combustion pressure at 0 [m] Pe : 20.81 [kg/cm2]

exhaust pressure at 0 [m] Pu : 3.77 [kg/cm^2 ]

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compression-start temperature at 0 [m] Tic: 391 [°K] (117 [°C])

compression-end temperature at 0 [m] Tc: 523 [°K] (250 [°C])

average engine wall temperature at 0 [m] : 476 [K] (202 [°C])

caloric combustion temperature at 0 [m] Tec: 1968 [°K] (1695 [°C])

polytroph combustion temperature at 0 [m] Tep : 2015 [°K] (1742 [°C])

estimated combustion temperature at 0 [m] Te (T4): 1960 [°K] (1687 [°C])

polytrope expansion-end temperature at 0 [m] Tup: 1168 [°K] (895 [°C])

exhaust stroke end temperature at 0 [m] Tu: 1044 [°K] (771 [°C])

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emergency/take off rating at 1376 [rpm] at sea level : 88 [hp]

Thermal efficiency Nth : 0.289 [ ]

Mechanical efficiency Nm : 0.674 [ ]

Thermo-dynamic efficiency Ntd : 0.195 [ ]

design hours : 1667 time between overhaul : 73

fuel consumption optimum mixture at 1250.00 [rpm] at 0 [m]: 26.68 [kg/hr]

specific fuel consumption thermo-dynamic : 308 [gr/epk] = 413 [gr/kwh]

estimated specific fuel consumption (cruise power) at 0 [m] optimum mixture : 425 [gr/kwh]

estimated sfc (cruise power) at 1750 [m] rich mixture : 441 [gr/kwh]

specific fuel consumption at 0 [m] at 1250 [rpm] with mixture :14.0 :1 : 447 [gr/kwh]

estimated specific oil consumption (cruise power) : 110 [gr/kwh]

Literature :

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

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