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Tuesday, May 8th 2007, 8:39pm

Aircraft Engines



4-stroke Petrol engines operate on the Otto Cycle as shown on the Pressure-Volume graph above.
Stage 1->2 Compression
Stage 2->3 Heat addition
Stage 3->4 Expansion
Stage 4->1 Heat rejection

The volume enclosed can be found. This gives the Mean Effective Pressure (MEP) which is used as a yardstick for comparison between different engines.

MEP = (4 x Pi x Torque) / (Displacement x 10^-3)

Where displacement is in litres, MEP in Pa and torque in Nm. A suitable modifier can be incorporating into the equations for the heathens who still use cubic inches.

It is not usually common to find torque values so this is replaced by power/engine speed. Engine speed is usually given in rpm and so needs to be multipied by 60/(2 x Pi). This gives;

MEP = (8 x Pi^2 x Power) / (0.06 x Displacement x Engine Speed)

MEP = (960 x Power) / (Displacement x Engine Speed)

Note Power in hp not kW for kW use 1290 and answer in bar

From this it is possible to work out historical MEP values and then use these to get a value for any engine you want to invent.

The Merlin for example goes from MEP of 12.2 to an eventual 31.2bar

There are further limitations on engines related to volumetric effeciency and strength issues.

The bore of the cylinder has a maximum size of about 160mm. Much greater than this and there are problems in spreading out the charge to burn evenly. You'd need different valves (e.g. sleeves) to operate more efficiently.

The speed of the piston is limited by the stress placed on the piston rings to about 15m/s. To find the engine speed for a given stroke(in m);

(15 x 60) / (2 x stroke) = engine speed

It'll typically be between 2500 and 4000rom

To find the displacement of an engine decide on the bore, stroke and no. of cylinders

Displacement = (Pi x bore^2 x stroke x No. of cylinders) / 4

Kaiser Kirk

Lightbringer and former European Imperialist

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2

Wednesday, May 9th 2007, 12:28am

RE: Aircraft Engines

Quoted

Originally posted by Red Admiral
the heathens who still use cubic inches.


...people use some other measurement ?

Actually cu. in. rarely matters here, we deal in cu. yards :) For a truely archaic measure, we use chains, as in 80 chains to the mile. :)

Back to the subject, interesting post. Graphing the MEP in relation to date would seem to establish a basis for hypothetical engine's performance.

This post has been edited 1 times, last edit by "Kaiser Kirk" (May 9th 2007, 12:31am)


3

Wednesday, May 9th 2007, 10:52am

For cu in of displacement instead of 960 multiplier use 58600 instead.

I'll work out some MEP values and plot them against date.

4

Wednesday, June 20th 2007, 7:37pm

Source code

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Engine Type	Power	Displacement 	RPM	BMEP	Year
Hispano Suiza 12Y	760	36	2400	8.444444444	1932
MikulinAM-34	825	45.82	1850	9.343258579	1932
Merlin I	1030	27	3000	12.20740741	1936
DB600	900	33.9	2400	10.61946903	1936
V-1710	1000	28	3000	11.42857143	1936
Bristol Pegasus	885	28.7	2600	11.38568748	1936
Bristol Perseus	810	24.9	2400	13.01204819	1936
Bristol Mercury	840	24.9	2750	11.77656079	1936
Hispano Suiza 12Y	867	36	2400	9.633333333	1936
R-2600	1600	42.7	2600	13.83534498	1936
R-3350	2200	54.56	2600	14.88833747	1937
DB601A	1175	33.9	2500	13.30973451	1938
Sabre I	2050	36.7	3800	14.11157321	1938
Jumo 211	1200	35	2400	13.71428571	1938
Mikulin AM34	1200	45.82	1850	13.5901943	1938
Merlin XX	1480	27	3000	17.54074074	1939
V-3420	2600	56	3000	14.85714286	1939
Bristol Hercules	1290	38.7	2900	11.03448276	1939
Hispano Suiza 12Z	1500	36	2700	14.81481481	1939
Sabre I	2200	36.7	3800	15.14412735	1940
Sabre I	2400	36.7	3800	16.5208662	1940
Hispano Suiza 12Y	1084	36	2400	12.04444444	1940
Jumo 211	1475	35	2600	15.56043956	1940
Jumo 213	1750	35	3250	14.76923077	1940
Mikulin Am38	1700	46.66	2350	14.88358519	1940
Shevstov M-82	1700	41.2	2600	15.23525019	1940
Merlin 45M	1585	27	3000	18.78518519	1941
DB601E	1450	33.9	2700	15.20812848	1941
V-1710	1325	28	3000	15.14285714	1941
BMW801	1560	41.8	2700	13.26953748	1941
Bristol Pegasus 100oct	1065	28.7	2600	13.70142053	1941
R-2800	2000	46	2600	16.05351171	1941
R-2600	1850	42.7	2600	15.99711764	1941
Merlin 24	1640	27	3000	19.43703704	1942
Merlin 63	1710	27	3000	20.26666667	1942
DB603A	1750	44.5	2700	13.98252185	1942
DB605A	1475	35.7	2800	14.16566627	1942
Bristol Hercules	1650	38.7	2900	14.1138733	1942
Bristol Centaurus	2520	53.6	2700	16.71641791	1942
Mikulin Am42	2000	46.66	2500	16.45949421	1942
BMW801D	1730	41.8	2700	14.71557682	1943
Jumo 213B	2000	35	3250	16.87912088	1943
R-3350	3700	54.56	2600	25.03947665	1943
Merlin 130	2030	27	3000	24.05925926	1944
Merlin Experimental	2640	27	3000	31.28888889	1944
DB603L	2000	44.5	2700	15.98002497	1944
DB605DBM	1800	35.7	2800	17.28691477	1944
DB605DCM	2000	35.7	2800	19.20768307	1944
Sabre V	3040	36.7	3040	26.15803815	1944
R-2800	2800	46	2600	22.47491639	1944
R-4360	4300	71.4	2600	22.23658694	1944
Sabre VII	3500	36.7	3800	24.09292987	1945
V-1710	2200	28	3000	25.14285714	1945
BMW801E	2000	41.8	2700	17.01222754	1945
BMW801F	2400	41.8	2700	20.41467305	1945
Sabre VIII	4000	36.7	3800	27.534777	1946


Some acquired BMEP values.

A plot of BMEP against date shows an increasing trend but there is a lot of variation. Generally a lower BMEP will result in a more reliable engine.

For comparison with the above, my bike engine (lowest of all the low powered things) has a BMEP of 11.5bar

Kaiser Kirk

Lightbringer and former European Imperialist

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5

Wednesday, June 20th 2007, 10:01pm

Very nice RA, thank you. Now all I have to do is digest it :)

I thought I'd include this list as well. It's obviously not complete, but while learning to use planebuilder I found the question of engine dimensions to be valid, and wound up trying to piece together information from that notoriously reliable source... the internet.

HP (TO vs. Max vs. at what altitude) and year (i.e. reliable production vs. prior) were often hard, and often only one weight, usually of the main or later model was available.

Historical Engines
1929: 625hp Gnome-Rhone Mistral Major 14k radial

1930: 650hp /1,387 lb V-1710-115 Allison prototype. 2.45' h x 3.05'wide.
1930:

1931: Jumo 210 19.7L development started.

1932: 775hp / 1,162lb R-18303 Twin Wasp, 31.63L, 4.2'dia.
1932: 760hp / 1,036lb, Hispano-Suiza 36L 12Y, 3.1 ft high x 2.5 ft. wide x 5.7 ft long.
1932: DB600 development started.

1933: 750hp / ?lb Pegasus III
1933: 1,025hp / ?lb Gnome-Rhone Mistral Major 14kfrs
1933: 770hp Gnome-Rhone Mistral 7k

1934: 670hp / 981lb Jumo 210A 19.7L est. 3.4 ft high x 2.3 ft. wide x 4.9 ft. long.

1935: Historical date Standard Oil developed 100 octane fuel.
1935: 750hp / 1,036lb, M-100 variant of Hispano-Suiza 12Y
1935: PV-12, Merlin prototype
1935: 867hp / 1,687lb Jumo 211 prototype 35L 3.5 ft high x 2.7 ft. wide x 7.2 ft. long.
1935: 867hp / 1,036lb, Hispano-Suiza 12Y-21 100 octane 36L, , 3.1 ft high x 2.5 ft. wide x 5.7 ft long.
1935: RR Kestrel VI

1936: 810hp / 1001lb Wright Cyclone GR-1820-G2, 29.88L, 4.5' dia.
1936: 890hp / 1001lb Wright Cyclone GR-1820-F52, 29.88L, 4.5' dia.
1936: 719hp / 981lb Jumo 210G 21L 3.4 ft high x 2.3 ft. wide x 4.9 ft. long.
1936: 850hp / 1,036lb, Hispano-Suiza 36L 12Y-31, 3.1 ft high x 2.5 ft. wide x 5.7 ft long.
1936: 950hp / 1,300lb Gnome-Rhone Mistral Major 14N, 38.7L, 4.3' dia.

1937: 1,050hp/ 1,310(?)lb P&W R-1830-66 Twin Wasp, 31.63L, 4.2' dia.
1937: 600hp / 883lb SIHI-G Wasp, 21.9L, 4.3' dia.
1937: 800hp / 1,015lb SIE-G Hornet, 27.7L, 4.6' dia.
1937: 700hp / 1,070lb S2A4-G Twin Wasp Junior, 3.7' dia.
1937: 1,000hp / 1,265lb SB-G Twin Wasp, 31.63L , 4' dia.
1937: 1,065hp / 1,180lb Pegasus XVIII, 28.7L, 4.6' dia.
1937: 955hp Dagger VII , unreliable.
1937: 1,000hp /1,387 lb V-1710-115 Allison prototype. 2.45' h x 3.05' wide.
1937: 1,085hp / 1,687lb Jumo 211A 35L 3.5 ft high x 2.7 ft. wide x 7.2 ft. long.
1937: 970hp / 1,300lb Gnome-Rhone Mistral Major 14N, 38.7L, 4.3' dia.

1938 : 1,350hp / 2502lb = 36.8hp/L Napier prototype, H block.
1938 : 2,050hp / 2502lb = 55.9hp/L Napier prototype, H block.
1938: 1,030hp/ 1,320lb Merlin II, 27L, unreliable.
1938: 1,183hp / 1,455lb Jumo 211B 35L 3.5 ft high x 2.7 ft. wide x 7.2 ft. long.
1938: 900hp / 1,036lb, Hispano-Suiza 36L 12Y-45

1938 : BF109V14 : DB601A 1100

1939: 1000hp Dagger VIII, air-cooled H, unreliable.
1939: 1,130hp/ 1,320lb Merlin X, 27L, reliable.
1939: 995hp/1,065lb Bristol Mercury XV, 24.9L, 4' 3.5"dia.
1939: 1,290hp/ 1,930lb Bristol Hercules I, 38.7L, 4'4" dia.
1939: 1,375hp/ 1,930lb Bristol Hercules II, 38.7L, 4'4" dia.
1939: FW 190 v1, 1550hp BMW 139
1939: FW 190 v1, 1550hp BMW 801
1939: Gnome-Rhone 14R, 1291hp
1939: 1030hp /1,300lb Gnome-Rhone Mistral Major 14N, 38.7L, 4.3' dia.
1939: Gnome-Rhone 14R, start 1578hp MAX


1940: 1,030hp/ 1,320lb Merlin II, 27L, reliable.
1940: USN 2-stage supercharger.
1940: 2,200hp / 2,502lb = 59.9hp/L Napier 3.84' h x 3.33'wide.
1940: 1,500hp/ 1520hp Hispano-Suiza 12Z-17, 36L,
1940: 1,084hp/1,036 lb. Hispano-Suiza 12Y-51, 36L, 3.1 ft high x 2.5 ft. wide x 5.7 ft long.
1940 : 1,200hp/1,467 P&W R-1830-76 Twin Wasp, 31.63L, 4.2'dia.
1940 : 1,000hp Wright R-1820-G205A Cyclone
1940 1,100hp / 1,365lb, M-105, 35L,
1940: 1,500hp/ 1,930lb Bristol Hercules XI, 38.7L, 4'4" dia.
1940: Gnome-Rhone 14N, 1100hp
1940: DB601E start

1941: 1,730hp / 2,707lb BMW 801-C, 41.8L, 4.2'dia.
1941: Japanese 2-stage supercharger.
1941 : Nakajima Sakae 21, 1,130hp
1941: 1,250hp /1,595 lb V-1710-115 Allison prototype. 28L, 2.45' h x 3.05'wide.
1941: 1,322hp / 1,587lb Jumo 211F 35L 3.5 ft high x 2.7 ft. wide x 7.2 ft. long.

1941: Bf109E-4/N DB601N 1,200hp
1941: FW 190A-1, 1560 BMW 801C-1
1941: FW 190A-2, 1600 BMW 801C-2

1942: 1,180hp / 1,365lb, VK-105PF , 35L
1942: 1,650hp / 1,685lb, VK-107A, 35L
1942: 2,520hp/ 2,695lb Bristol Centaurus VII, 53.6L, 4'7.3" dia.

edit: squares

This post has been edited 1 times, last edit by "Kaiser Kirk" (Jun 21st 2007, 12:30am)