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performance calculations for the Piaggio P.X RC aircraft engine
Piaggio P.X RC air-cooled 9 -cylinder radial engine 700 [hp](522.0 KW)
gear-driven supercharger, constant power to height : 1000 [m] blower ratio : 7.35 [:1]
introduction : 1936 country : Italy importance : ***
applications : Savoia-Marchetti S.M.73
normal rating : 700 [hp](522.0 KW) at 2300 [rpm] at 1000 [m] above sea level
take-off power : 670 [hp] (499.6 [KW]) at 2350 [rpm]
reduction : 0.62 , valvetrain : overhead valves, pushrod operated
weight engine(s) dry with reduction gear : 435.0 [kg] = 0.83 [kg/KW]
General information :
fuel system : fuel type : octane grade no. 87 oil system :
engine starter type :
bore : 146.0 [mm] stroke : 165.0 [mm]
valve inlet area : 32.5 [cm^2] one inlet and one exhaust valve in cylinder head
gas speed at inlet valve : 45.8 [m/s]
blower speed : 16905 [rpm] , mixture :13.0 :1
compression ratio: 6.00 :1
published stroke volume (Vs displacement): 24.900 [litre]
calculated stroke volume (Vs displacement) : 24.861 [litre]
compression volume (Vc): 4.972 [litre]
total volume (Vt): 29.833 [litre]
diam. engine : 128 [cm]
calculated engine length: 140 [cm]
specific power : 21.0 [kW/litre]
torque : 2167 [Nm]
engine weight/volume : 17.5 : [kg/litre]
average piston speed (Cm): 12.7 [m/s]
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intake manifold absolute pressure (MAP) at 1000 [m] altitude Pi : 1.00 [kg/cm2]
(28.96 [inHg])
mean engine pressure (M.E.P.) at 1000 [m] altitude Pm : 9.17 [kg/cm2]
compression pressure at 1000 [m] altitude Pc: 9.39 [kg/cm2]
estimated combustion pressure at 1000 [m] Pe : 37.51 [kg/cm2]
exhaust pressure at 1000 [m] Pu : 3.92 [kg/cm^2 ]
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compression-start temperature at 1000 [m] Tic: 343 [°K] (70 [°C])
compression-end temperature at 1000 [m] Tc: 527 [°K] (254 [°C])
average engine wall temperature at 1000 [m] : 476 [K] (202 [°C])
caloric combustion temperature at 1000 [m] Tec: 2257 [°K] (1984 [°C])
polytroph combustion temperature at 1000 [m] Tep : 2106 [°K] (1833 [°C])
estimated combustion temperature at 1000 [m] Te (T4): 2152 [°K] (1879 [°C])
polytrope expansion-end temperature at 1000 [m] Tup: 1151 [°K] (878 [°C])
exhaust stroke end temperature at 1000 [m] Tu: 1104 [°K] (831 [°C])
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calculations for take-off/emergency power at sea level
average piston speed : 12.9 [m/s]
gas speed at inlet valve : 46.8 [m/s]
caloric combustion temperature at sea level Tec: 2321 [°K] (2048 [°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 2350 [rpm] at sea level : 669 [hp]
Thermal efficiency Nth : 0.361 [ ]
Mechanical efficiency Nm : 0.744 [ ]
Thermo-dynamic efficiency Ntd : 0.269 [ ]
design hours : 1049 [hr] time between overhaul : 334 [hr]
dispersed engine heat by cooling air : 6942.82 [Kcal/minuut/m2]
required cooling surface : 14.70 [m2]
weight cooling ribs : 43.55 [kg]
fuel consumption optimum mixture at 2300.00 [rpm] at 1000 [m]: 150.10 [kg/hr]
specific fuel consumption thermo-dynamic : 224 [gr/epk] = 300 [gr/kwh]
specific fuel consumption (cruise power) at 1000 [m] : 300 [gr/kwh]
specific fuel consumption (volume*rpm) MAP = 1.0 kg/cm2 at 2300 [rpm] : 310 [gr/kwh]
estimated specific oil consumption (cruise power) : 8 [gr/kwh]
Literature :
Wikipedia
Jane’s all the world aircraft
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 28 November 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4
notes :