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performance calculations for the Gnome 7 Omega WWI aero engine
Omega in the New England Air Museum, USA
Gnome 7 Omega air-cooled 7 -cylinder atmospheric inlet-valve rotary engine 50 [hp](36.8 KW)
introduction : September 1911 country : France importance : ***
applications : Bleriot XIbis, Bristol Box-kite
normal rating : 50 [hp](36.8 KW) at 1150 [rpm] at 0 [m] above sea level
no reduction, direct drive, valvetrain :
weight engine(s) dry : 75.0 [kg] = 2.04 [kg/KW]
bore : 110.0 [mm] stroke : 120.0 [mm]
Mechanical efficiency/mean pressure correction factor : 0.735 [ ]
invloed hoogte > cm : 0.63 [ ]
compression ratio: 0.00 :1
calculated compression ratio : 3.61 : 1
published volume (displacement): 8.000 [litre]
calculated stroke volume (Vs) : 7.983 [litre]
compression volume (Vc): 3.064 [litre]
total volume (Vt): 11.046 [litre]
power / stroke volume (litervermogen Nl): 4.6 [kW/litre]
torque : 305 [Nm]
engine weight/volume : 9.4 : [kg/litre]
average piston speed (Cm): 4.6 [m/s]
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intake pressure at 0 [m] altitude Pi : 0.95 [kg/cm2]
mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 4.75 [kg/cm2]
compression pressure at 0 [m] altitude Pc: 4.93 [kg/cm2]
estimated combustion pressure at 0 [m] Pe : 19.70 [kg/cm2]
estimated combustion pressure at 0 [m] Pe : 20.71 [kg/cm2]
exhaust pressure at 0 [m] Pu : 3.80 [kg/cm^2 ]
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compression-end temperature at 0 [m] Tc: 527 [°K] (253 [°C])
caloric combustion temperature at 0 [m] Tec: 2003 [°K] (1730 [°C])
polytroph combustion temperature at 0 [m] Te (T4): 2099 [°K] (1825 [°C])
exhaust temperature at 0 [m] Tu: 1245 [°K] (972 [°C])
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emergency/TO rating can be increased with higher [rpm}
(emergency/take off) rating at 1259 [rpm] at sea level : 55 [pk]
Thermal efficiency Nth : 0.274 [ ]
Mechanical efficiency Nm : 0.639 [ ]
Thermo-dynamic efficiency Ntd : 0.175 [ ]
design hours : 2248 time between overhaul : 330
fuel consumption optimum mixture at 1150.00 [rpm] at 0 [m]: 19.62 [kg/hr]
specific fuel consumption thermo-dynamic : 361 [gr/epk] = 490 [gr/kwh]
specific fuel consumption (cruise power) at 0 [m] optimum mixture : 515 [gr/kwh]
estimated sfc (cruise power) at 1500 [m] rich mixture : 527 [gr/kwh]
specific fuel consumption at 0 [m] at 1150 [rpm] optimum mixture : 533 [gr/kwh]
estimated specific oil consumption (cruise power) : 90 [gr/kwh]
Omega on display at the Royal air force museum, London
Literature :
Jane’s all the world aircraft 1913
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 29 February 2020 contact : info.aircraftinvestigation@gmail.com python 3.7.4