Design & Spec a 14-cyl Bristol Mercury with Fuel Injection

[Bretoal2]

So basically it's a cooling issue that requires a clean sheet engine. I know less about the sleeve valve lineage -- where did the Perseus stumble?

The Perseus didn't stumble, but was quickly overtaken by a significantly more powerful engine—the Hercules, whose cylinders were exactly the same size, but with 14 ones instead of the Perseus's 9, and thus gave 1,375 hp as soon as 1938, running on 87 octane fuel.

Producing less than 1,000 hp, the Perseus was thus doomed, and a final attempt to boost performance —the Perseus 100, whose stroke had been increased from 165 to 178 mm (from 6.5 to 7.00 inches)—yet produced a 1,200 hp engine, but still far inferior to the Hercules, despite its slightly larger diameter.

So, the Perseus gave a power that was no longer competitive from the start of the conflict, and its development was halted in 1942 before its teething troubles were fully resolved. Only 2,800 were built, while the Hercules was produced over 50,000.

But one consolation: the Perseus-100 was the "father" of the Centaurus, whose cylinders had exactly the same dimensions. The power outputs "per cylinder" of these two engines were actually similar.

 

[Shortround6]

But one consolation: the Perseus-100 was the "father" of the Centaurus, whose cylinders had exactly the same dimensions. The power outputs "per cylinder" of these two engines were actually similar.

It may have been the other way around. The Perseus 100 may have been the junior Centaurus ( one row of 9 instead of two rows of 9). There don't seem to any photographs of the actual Perseus 100, or at least Wilkinson's says no photo was available in Feb 1946. It is not mentioned in Lumsden. It may have been an attempt to get orders for a British 1200hp engine post war for the commercial market. Unfortunately the commercial market was flooded with surplus R-1820s, R-2000 and R-1820s. P&W could not sell enough new R-2180s (1/2 of an R-3360)to pay for the R&D and tooling for example.

Perseus was doomed in the late 30s due to it's size. A 25.9 liter engine was simply not big enough to compete even with the wonders of the sleeve valve.
Trying to compete with the American 30liter engines was depending way too much on the Sleeve valve. The Americans (and others) had solved just about all of the real poppet valve problems by the late 30s. P&W canned their own 25.2liter 14 cylinder engine in 1939/40 as far as development goes. They filled out existing contracts for but the R&D was going to bigger engines Like the R-1830 and R-2000. P&W even cut the early R-2180 as it being too small a step up from the R-1830 and went for the R-2800.
The German BMW 132 was a developed P&W R-1690 (27.7 liters) But P&W had abandoned that engine to work on the R-1830.

Running a Perseus with a better supercharger and later Hercules cylinders is going to get you a a 1030hp engine when the Hercules is giving 1600hp (rounded up/off) which shows the problem with trying to push the Perseus very far. 1800hp Hercules cylinders is going to give you 1160hp? But 1800hp Hercules is into the 100 series of engines of 1944?
Hercules XVIII made that much power but used a cropped impeller in the supercharger so while making good power at really low levels, they weren't really very good in the mid/high teens.
I am assuming that the lower end (crankshaft and crankcase) and supercharger have been modified to mirror the Hercules just to show that even better cylinders (cooling and ability to use high octane fuel) was not going to turn the small engine into a first class engine.

 

[Bretoal2]

It may have been the other way around. The Perseus 100 may have been the junior Centaurus ( one row of 9 instead of two rows of 9). There don't seem to any photographs of the actual Perseus 100, or at least Wilkinson's says no photo was available in Feb 1946. It is not mentioned in Lumsden. It may have been an attempt to get orders for a British 1200hp engine post war for the commercial market. Unfortunately the commercial market was flooded with surplus R-1820s, R-2000 and R-1820s. P&W could not sell enough new R-2180s (1/2 of an R-3360)to pay for the R&D and tooling for example.

Perseus was doomed in the late 30s due to it's size. A 25.9 liter engine was simply not big enough to compete even with the wonders of the sleeve valve.
Trying to compete with the American 30liter engines was depending way too much on the Sleeve valve. The Americans (and others) had solved just about all of the real poppet valve problems by the late 30s. P&W canned their own 25.2liter 14 cylinder engine in 1939/40 as far as development goes. They filled out existing contracts for but the R&D was going to bigger engines Like the R-1830 and R-2000. P&W even cut the early R-2180 as it being too small a step up from the R-1830 and went for the R-2800.
The German BMW 132 was a developed P&W R-1690 (27.7 liters) But P&W had abandoned that engine to work on the R-1830.

Running a Perseus with a better supercharger and later Hercules cylinders is going to get you a a 1030hp engine when the Hercules is giving 1600hp (rounded up/off) which shows the problem with trying to push the Perseus very far. 1800hp Hercules cylinders is going to give you 1160hp? But 1800hp Hercules is into the 100 series of engines of 1944?
Hercules XVIII made that much power but used a cropped impeller in the supercharger so while making good power at really low levels, they weren't really very good in the mid/high teens.
I am assuming that the lower end (crankshaft and crankcase) and supercharger have been modified to mirror the Hercules just to show that even better cylinders (cooling and ability to use high octane fuel) was not going to turn the small engine into a first class engine.

The main problem, as I mentioned above without delving too deeply into the idea, is that the realities of the conflict very quickly showed that nothing could be done with a low-powered engine. So, development in England focused on the Merlin, boosted to its limits, the Vulture (aborted), the Sabre, and the Centaurus. In the midst of all this, an 800 hp engine was of no use, as would have been a junior Hercules. The French made the same mistake with the Gnome-Rhône 14M and Hispano-Suiza 14AB, of the 650 hp class (!!!). Same mistake, but even worse, than the Peregrine. See that the first version of the Sud-Est 100 (LéO 50), "heavy" fighter intended to accommodate 6 to 8 HS 404 guns, had been designed around two G&R 14Ms!

One should also consider the english Air Ministry's policy towards engine development, which was not exactly "straightforward" during the first months of the war.

 

[loftonhenderson]

Ok I did some reading, tried to incorporate your feedback, and gave it a go:

1. Bristol "Aries" (Poppet Perseus-type engine)

Type: 9-cylinder, air-cooled, poppet-valve, 26.76L radial engine (two large valves per cylinder)
Specs: ~54" diameter, ~56" length, 5.85" × 6.75" bore & stroke, ~1,250–1,350 lbs (dry)
Dates: 1933 first run; 1934 first flight; 1937 production start / operational use

Notes:​

• Context: "The Perseus used nine 5.75" x 6.5" cylinders (24.9L) and ran at 2750 rpm. 52" dia. 1,120lbs"
• Context: "Perseus 100 used nine 5.75" x 7" cylinders (26.8L) and ran at 2700 rpm. 55.2" dia. 1,325lbs. Used Centaurus parts to make a postwar Pegasus-type (application) engine"
• Cylinders: shorter, fatter barrel increases fin area and stiffens the assembly compared to Pegasus
• Heads: aluminum alloy monobloc with machined steel fins and improved finning; hemi-ish 2V chamber, included angle ~46° (radial-friendly, good quench area, keeps diameter tight); sodium‑cooled exhaust valves; stellite seats
• Valvetrain: single cam‑ring, two tracks; enclosed, pressure‑fed rockers
• Cranktrain: forged steel main crank; split‑type aluminum alloy crankcase with steel center web for the middle main and reduction gear thrust
• Fuel/air: pressure carburetor (Bendix‑type) + port-assist injection (small, constant-pressure jets at each intake stub; on/off or staged for high boost), automatic boost control; anti‑detonant injection (ADI)
• Supercharger: single‑stage, two‑speed centrifugal; 11.8" impeller with inducer vanes, modern vaneless diffuser + scroll; clean plenum

Max HP (WEP unless noted + ADI if applicable):​

(supercharger type, max rpm, boost, fuel; special systems; dry weight)​

• 1937 / Aries IV: 2-speed S/C, 2,600 rpm, —, 87 oct; pressure carb + port injection; ~1,300 lbs
  • ~1,000 hp @ SL
  • ~920 hp @ ~6kft (low gear)
  • ~890 hp @ ~15kft (high gear)
• 1939 / Aries VIII: 2-speed S/C, 2,700 rpm, —, 100 oct; pressure carb + port injection; ~1,300 lbs
  • ~1,180 hp @ SL
  • ~1,125 hp @ 6.5kft (low gear)
  • ~1,090 hp @ 16kft (high gear)
• 1940 / Aries X (ADI): 2-speed S/C, 2,700 rpm, —, 100 oct; pressure carb + port injection, ADI; ~1,325 lbs
  • ~1,320 hp @ SL
  • ~1,230 hp @ ~5.5kft (low gear)
  • ~1,170 hp @ ~14.5kft (high gear)

Thoughts? I'm assuming a slightly smaller dia than the Perseus 100 because the cylinders are a bit shorter and fatter. Also assuming a number of Hercules-style cylinder/crank/bottom end modifications.

 

[loftonhenderson]

S Shortround6 B Bretoal2 D don4331 tomo pauk Z z42 any thoughts?