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performance calculations for the Wright 12 hp aero engine
The fuel ignition didn't happen in the cylinders, as in most internal combustion engines, but in combustion chambers attached to the cylinders. The spring-operated "automatic" intake valves are at the tops of the chambers, while the cam-operated exhaust valves are at the bottom.
Wright 12 hp liquid-cooled 4 -cylinder inline engine 12 [hp](8.9 KW)
introduction : December 1903 country : United States importance : *****
applications : Wright Flyer I
max. continuous(take-off) rating : 12 [hp](8.9 KW) at 1025 [rpm] at 0 [m] above sea
level
When started it’s output was 16 hp dropping to 12 hp when the engine heated up.
It had an aluminium crankcase.
The engine was cooled by water from a narrow vertical water reservoir mounted on a forward strut. The system was not a radiator in the typical sense, for the water did not circulate. The reservoir simply replenished the water jacket as the water evaporated from it.
reduction : 0.341 , valvetrain :
It had a 13.6 kg flying wheel, later aircraft used the propeller as flying wheel.
weight reduction gear : 3.6 [kg] > two chains driving the two propellers
fuel system : oil system :
weight engine(s) dry without reduction gear : 82.0 [kg] = 9.16 [kg/KW]
bore : 102.0 [mm] stroke : 102.0 [mm]
valve inlet area : 13.3 [cm^2] one inlet and one exhaust valve in cylinder head
gasspeed at inlet valve : 14.9 [m/s]
throttle : 99 /100 open, mixture :13.0 :1
compression ratio : 3.00 : 1
published volume (displacement): 3.300 [litre]
calculated stroke volume (Vs) : 3.334 [litre]
compression volume (Vc): 1.671 [litre]
total volume (Vt): 5.005 [litre]
hoogte motor : 71 [cm]
power / stroke volume (litervermogen Nl): 2.7 [kW/litre]
torque : 83 [Nm]
engine weight/volume : 24.8 : [kg/litre]
average piston speed (Cm): 3.5 [m/s]
intake pressure at 0 [m] altitude Pi : 1.00 [kg/cm2]
mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 3.57 [kg/cm2]
compression pressure at 0 [m] altitude Pc: 3.95 [kg/cm2]
estimated combustion pressure at 0 [m] Pe : 15.76 [kg/cm2]
estimated combustion pressure at 0 [m] Pe : 17.83 [kg/cm2]
exhaust pressure at 0 [m] Pu : 3.95 [kg/cm^2 ]
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compression-start temperature at 0 [m] Tic: 409 [°K] (136 [°C])
compression-end temperature at 0 [m] Tc: 520 [°K] (247 [°C])
average engine wall temperature at 0 [m] : 476 [K] (202 [°C])
caloric combustion temperature at 0 [m] Tec: 1973 [°K] (1700 [°C])
polytroph combustion temperature at 0 [m] Tep : 2076 [°K] (1803 [°C])
estimated combustion temperature at 0 [m] Te (T4): 2008 [°K] (1735 [°C])
expansion-end temperature to high > valves will get burned
polytrope expansion-end temperature at 0 [m] Tup: 1278 [°K] (1005 [°C])
exhaust stroke end temperature at 0 [m] Tu: 1186 [°K] (913 [°C])
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emergency/take off rating is equal to max.continuous rating : 12 [hp](8.9 KW)
Thermal efficiency Nth : 0.240 [ ]
Mechanical efficiency Nm : 0.610 [ ]
Thermo-dynamic efficiency Ntd : 0.146 [ ]
design hours : 8819 time between overhaul : 621 [hr]
fuel consumption optimum mixture at 1025.00 [rpm] at 0 [m]: 7.61 [kg/hr]
specific fuel consumption thermo-dynamic : 410 [gr/epk] = 550 [gr/kwh]
estimated specific fuel consumption (cruise power) at 0 [m] optimum mixture : 600 [gr/kwh]
estimated sfc (cruise power) at 100 [m] rich mixture : 612 [gr/kwh]
specific fuel consumption at 0 [m] at 1025 [rpm] with mixture :13.0 :1 : 851 [gr/kwh]
estimated specific oil consumption (cruise power) : 25 [gr/kwh]
The 1903 Wight engine had no carburettor to vaporize the fuel. Instead, gasoline dripped onto the hot engine block through an opening (in above drawing you can see the opening >air+arrow). As the gasoline evaporated, it was sucked into the combustion chambers.
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/
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(c) B van der Zalm 15 May 2019 contact : info.aircraftinvestigation@gmail.com python 3.7.4