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performance calculations for the Maybach HS Lu WWI aero engine

Gondola from stranded Zeppelin LZ85 L45 near Laragne, south of France with Maybach HS Lu engine and local people posing for the picture.

Gondola of the stranded Zeppelin LZ85 L45 with Maybach HS Lu engine inside at the banks of river Buech near Laragne in the south of France, October 1917.

Maybach HS Lu liquid-cooled 6 -cylinder inline engine 240 [hp](179.0 KW)

German engine rating : 243.3 [PS]

introduction : 1916 country : Germany importance : ***

applications : Zeppelin LZ80 LZ113

max. continuous(take-off) rating : 240 [hp](179.0 KW) at 1400 [rpm] at 1800 [m] above sea level

high compression engine : cannot run at full power at sea level,

constant power to height : 1800 [m]

no reduction, direct drive, valvetrain : OHV

fuel system : oil system :

weight engine(s) dry without reduction gear : 390.0 [kg] = 2.18 [kg/KW]

bore : 165.0 [mm] stroke : 180.0 [mm]

valve inlet area : 49.9 [cm^2] two inlet and two exhaust valves in cylinder head

gas speed at inlet valve : 25.3 [m/s]

throttle : 99 /100 open, mixture :13.0 :1

compression ratio: 6.08 :1

calculated compression ratio : 5.96 : 1

high compression engine cannot run with full power/throttle at sea-level (only for short period)

published volume (displacement): 23.100 [litre]

calculated stroke volume (Vs) : 23.093 [litre]

compression volume (Vc): 4.546 [litre]

total volume (Vt): 27.639 [litre]

engine height : 108 [cm]

power / stroke volume (litervermogen Nl): 7.7 [kW/litre]

torque : 1221 [Nm]

engine weight/volume : 16.9 : [kg/litre]

average piston speed (Cm): 8.4 [m/s]

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intake pressure at 1800 [m] altitude Pi : 0.84 [kg/cm2]

mean engine pressure (M.E.P.) at 1800 [m] altitude Pm : 6.14 [kg/cm2]

compression pressure at 1800 [m] altitude Pc: 8.00 [kg/cm2]

estimated combustion pressure at 1800 [m] Pe : 31.96 [kg/cm2]

exhaust pressure at 1800 [m] Pu : 3.29 [kg/cm^2 ]

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compression-start temperature at 1800 [m] Tic: 373 [°K] (100 [°C])

compression-end temperature at 1800 [m] Tc: 569 [°K] (296 [°C])

Maybach HS Lu engine on display at the Modern Transport Museum, Osaka

Maybach HS Lu engine on display at the Modern Transport Museum in Osaka

average engine wall temperature at 1800 [m] : 476 [K] (202 [°C])

caloric combustion temperature at 1800 [m] Tec: 2379 [°K] (2106 [°C])

polytroph combustion temperature at 1800 [m] Tep : 2272 [°K] (1999 [°C])

estimated combustion temperature at 1800 [m] Te (T4): 2290 [°K] (2017 [°C])

polytrope expansion-end temperature at 1800 [m] Tup: 1213 [°K] (940 [°C])

exhaust stroke end temperature at 1800 [m] Tu: 1132 [°K] (859 [°C])

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calculations for take-off/emergency power at sea level

emergency/TO max rpm : 1414 [rpm]

intake pressure at sea level Pi : 0.98 [kg/cm2]

rich mixture 11 : 1 applied for cooling > carburettor adjustable in flight by the pilot

compression pressure (TO power) at sea level Pc: 9.04 [kg/cm2]

estimated combustion pressure at sealevel Pe : 34.31 [kg/cm^2 ]

compression-start temperature at sealevel max rpm Tic:386 [°K] (113 [°C])

compression-end temperature at sealevel max rpm Tc:576 [°K] (303 [°C])

caloric combustion temperature at 1800 [m] Tec: 2590 [°K] (2317 [°C])

polytrope expansion-end temperature at 1800 [m] Tup: 1265 [°K] (992 [°C])

exhaust stroke end temperature at 1800 [m] Tu: 1007 [°K] (734 [°C])

fuel weight max rpm sea level : 1.73 [kg/minuut] mixture 11.0 :1

mean engine pressure at sealevel max rpm Pm : 6.94 [kg/cm2]

emergency/take off rating at 1414 [rpm] at sea level : 274 [hp]

bruto emergency/take off rating at 1414 [rpm] at sea level : 309 [hp]

Thermal efficiency Nth : 0.363 [ ]

Mechanical efficiency Nm : 0.742 [ ]

Thermo-dynamic efficiency Ntd : 0.269 [ ]

design hours : 787 time between overhaul : 24

required cooling surface : 11.12 [m2]

fuel consumption optimum mixture at 1400.00 [rpm] at 1800 [m]: 56.03 [kg/hr]

specific fuel consumption thermo-dynamic : 223 [gr/epk] = 299 [gr/kwh]

estimated specific fuel consumption (cruise power) at 1800 [m] optimum mixture : 302 [gr/kwh]

estimated sfc (cruise power) at 2000 [m] rich mixture : 302 [gr/kwh]

specific fuel consumption at 1800 [m] at 1400 [rpm] with mixture :13.0 :1 : 313 [gr/kwh]

estimated specific oil consumption (cruise power) : 12 [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

so we can improve our program. For copyright on drawings/photographs/

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