Explore US alternatives to British sleeve valve engines (and the ramifications)

[KiwiBiggles]

...A 14 cylinder Perseus 100 derivative would have been interesting too...

Wouldn't a 14 cylinder Perseus development be otherwise known as the Hercules? They had the same bore and stroke, so I would be interested in what you would see as distinctive about a Perseus development.

 

[merlin]

I think the Taurus existed because it was a sleeve-valve version of the earlier Aquila - giving decent amount of power for a small engine.

 

[Shortround6]

The Aquila used nine 127 mm x 137 mm cylinders (950 cu in/15.6 liters) and ran at 3000rpm. 46 in dia.

The Perseus used nine 146 mm x 165 mm cylinders (1520 cu in/24.9 liters) and ran at 2750rpm. 52in dia. 1120lbs

The Taurus used fourteen 127 mm x 143 mm cylinders (1550 cu in/25.4 liters) and ran at 3000-3300rpm. 46.2in dia. 1300lbs

Hercules used fourteen 146 mm x 165 mm cylinders (2360 cu in/38.7 liters) and ran at 2700rpm. 52in dia. 1680lbs (early version/s?)

Centaurus used eighteen 146 mm x 177/8 mm cylinders (3270 cu in/53.6 liters) and ran at 2700rpm. 55.3in dia. 2700lbs (early version/s?)

Perseus 100 used nine 146 mm x 177/8 mm cylinders (1635 cu in/26.8 lites) and ran at 2700rpm, 55.2 dia and 1325lbs. Not sure if it ever flew, and was pretty much a post war engine. Use Centaurus parts to make a post war Pegasus type (application) engine.

Mercury used nine 146 mm x 165 mm cylinders (1520 cu in/24.9 liters) and ran at 2750rpm. 51.5in dia. 1010-1065lbs for later versions.

Pegasus used nine 146 mm x 190 mm cylinders (1750 cu in/28.7 liters) and ran at 2600rpm. 53.3/55.3?in dia. 1135-1180lbs for later versions.

The Taurus tried to use RPM to make up for small displacement and tried to use small diameter to make up for greater weight. Unfortunately the "market" had moved by the time is was ready (or close to ready) and most airframe makers and operators were looking for 1300-2000hp engines, not 1100-1200hp engines for new airframes. And if sleeve valve engines were significantly higher priced that limited the "market" for smaller or medium sized aircraft.

Bristol, pre-war was spending too much time and money competing with itself. The Perseus , despite coming to market first (1932) never really caught on in a big way.

 

[Koopernic]

Were power losses higher for sleeve valve engines than for a poppet valve engine?

Losses for a sleave valve engine were probably significantly less than a poppet valve engine.

What is called a 'rotating sleeve' engines have been built for automotive use (and are still under development) to reduce friction, increase engine life, increase fuel efficiency. It is essentially a 'sleeve valve' engine with the rotating sleeve but using traditional poppet valves for the actual induction and exhaust.

The sleeve valve does not seem to have developed any superiority since conventional technologies developed just as far if not further. The sodium cooled exhaust valves is one example but a multitude of other developments eroded the hypothetical advantage of the sleeve valve: counter balanced and counterweighted shafts, better springs, precision heads, vacuum cast heads etc, fuel injection.

No one post war seems to have persisted with them in automotive technology (maybe Rover a little?). The invention of a German engineer, Felix Wankel, during WWII then initially as a compressor seems to have shown more promise after the war though it sent a number of companies broke or near broke until being perfected by Mazda. (It was hoped large scale aviation Wankel engine might save curtiss wright)

For instance the Bristol Hercules at 2400cubic inch with sleeve valves had more diameter and generally less power than the 2600 cubic inch BMW801 and engine which had use of significantly inferior fuel (C3 was inferior to 100/130). The Hawker Typhoon with the Sabre never had superior speed or performance over the Fw 190 (except may be range and that is more a result of size) and it was not until laminar flow technology came in on the Tempest in mid/late 1944 that any gap opened up (clearly an airframe advance).

Radial engines generally use rocker operated poppet valves since overhead camshafts greatly increase diameter. Whatever inferiority in breathing of poppet valves seems to be easily made up by just turning up the boost pressure of the supercharger a little.

Possibly the sleeve valve might have won an all out 10 year billion dollar development race but the poppet valve was always at a more advanced stage of its development.

There were two interesting alternative piston attempts: the Napier Nomad 2 stroke diesel which used sleeve valves to ensure excellent scavenging of exhaust gases, it was trubo compounded and very efficient (no more efficient than the Jumo diesels but much lighter). The Germans (mainly BMW) played with something they called a 'ring cycle engine' that would now be called a HCCI (Homogenous Charge Combustion Ignition) engine whereby the charge is ignited not by a spark but a special ignitable fluid inject in a small quantity. It gets rid of troublesome spark plugs and the hots spots they have which may cause pre ignition. The special ignition fluid might be something like otherwsie troublesome heptane. HCCI engines are seriously efficient, around 50% and exceed even diesels.

 

[tomo pauk]

...

For instance the Bristol Hercules at 2400cubic inch with sleeve valves had more diameter and generally less power than the 2600 cubic inch BMW801 and engine which had use of significantly inferior fuel (C3 was inferior to 100/130).

The Hercules initially used the lower grade fuel than it was the 130 grade. C3 fuel got better as the war progressed, both countries of origin tried to up the boost power.
Hercules was at least as good as BMW 801, the Mk.VI making 1670 HP at 7500ft and 1500 HP at 17000 ft, per Beaufighter VI data sheet, dated August 1942*. Granted, BMW upped the boost in 1943 (via C3 as ADI) and in 1944, and introduced the 801S. Bristol produced the Hercules 100, that was good for 1800 HP at 10000 ft, and 1630 at 20000 ft. That mark (and later ones) rectified the major issue of the earlier Hercules vs. 801, namely the exhaust system.
The Hercules was regarded as trouble-free engine for most if not all of its service, unlike the BMW 801, where it took until late 1942 to sort out reliability issues that stopped reaching the anticipated power.

*maybe that was for operation at 2900 rpm?

The Hawker Typhoon with the Sabre never had superior speed or performance over the Fw 190 (except may be range and that is more a result of size) and it was not until laminar flow technology came in on the Tempest in mid/late 1944 that any gap opened up (clearly an airframe advance).

Let's not blame the engine. Typhoon was a far draggier aircraft, due to it's bigger thicker wings. The laminar flow technology was not needed, just forget the 19% thick wing and go for, say, 15% thick one, and the plane performs great.
We can also observe that performance of Fw-190 took a hit once 4 belt fed cannons were installed, speed was down to 651 km/h even on fully rated BMW 801Ds.

 

[bobbysocks]

there is supposed to be another rotary type engine out. saw it in a homebuilt ac forum. it doesnt use the wankel design....i'll see if i can dig it up...it LOOKED interesting...how well it works..???

think this is what i saw. right now its small for like lawnmowers and small equip. but a few steps up and the ultralight ac builders will be drooling....

Small engine packs a punch | MIT News

 

[wuzak]

There were two interesting alternative piston attempts: the Napier Nomad 2 stroke diesel which used sleeve valves to ensure excellent scavenging of exhaust gases, it was trubo compounded and very efficient (no more efficient than the Jumo diesels but much lighter).

The Napier Nomad didn't have sleeve valves, and I'm sure it was significantly more efficient than the Jumo Diesels, with which it shared some heritage (Napier building some Jumo Diesels under licence).

The Germans (mainly BMW) played with something they called a 'ring cycle engine' that would now be called a HCCI (Homogenous Charge Combustion Ignition) engine whereby the charge is ignited not by a spark but a special ignitable fluid inject in a small quantity. It gets rid of troublesome spark plugs and the hots spots they have which may cause pre ignition. The special ignition fluid might be something like otherwsie troublesome heptane. HCCI engines are seriously efficient, around 50% and exceed even diesels.

I think the HCCI concept is different to what you describe. HCCi basically works as a compression ignition engine, but using petrol rather than Diesel fuel.

I am not sure about "ring cycle". There weere some toroidalshaped engines made by the Germans, known as swing piston designs, to mainly be used as gas generators for turbines.

 

[pbehn]

Care to shed some light on that?

I know nothing about sleeve valve operation but they have the ports in the side of the bore like a two stroke. On a two stroke there is the theoretical compression ratio which is just a comparison of volumes. The actual compression ratio is different and depends on the scavenging and swirling and even harmonics in the exhaust and inlet which is where the tuners make their money. On many tuned 4 stroke engines the inlet and exhaust valves are open at the same time so the compression ratio is obviously a theoretical guide. I believe sleeve valves had some advantages (maybe just in theory) regarding port timing but that was in stuff I read as a teenager. Superchargers and Turbos no doubt queer the pitch even more.

 

[kool kitty89]

The Taurus tried to use RPM to make up for small displacement and tried to use small diameter to make up for greater weight. Unfortunately the "market" had moved by the time is was ready (or close to ready) and most airframe makers and operators were looking for 1300-2000hp engines, not 1100-1200hp engines for new airframes. And if sleeve valve engines were significantly higher priced that limited the "market" for smaller or medium sized aircraft.

Bristol, pre-war was spending too much time and money competing with itself. The Perseus , despite coming to market first (1932) never really caught on in a big way.

This latter bit really seems to be the issue. The US had P&W and Wright competing against eachother in areas where Bristol seemed to be more competing with themselves and on top of that the US end of things didn't have sleeve valves OR 4-valve-per-cylinder designs complicating matters.
If the R-1830 was having the level of problems the Taurus had, the R-1820 was nearly always a viable alternative in spite of the larger diameter.


Germany sort of had that issue too given Bramo and BMW merged, but that seemed to work out mostly for the best. (and the older 132 and 323 radials worked well enough for requirements in the 800~1200 HP range)

Then again, the US only had one viable liquid cooled inline design at all vs both the British and Germans having multiple ones from multiple firms. (or course, Japan was even more extreme with their array of radial designs)

Also ironic that the British and (especially) Germans both put tight-cowled, fan-cooled radials in service when the US and Japan had much heavier demand for those engine types and would have benefited even more. (and both Curtis and Republic experimented with such configurations successfully, but never put them into mass production -the final/optimum configruation on the XP-42 and XP-47J were both rather Fw-190/Tempest-II like)

 

[wuzak]

An article about the Hercules in which Feddon's claims for teh advantages of sleeve valves are shwon.

1941 | 2830 | Flight Archive

Courtesy of J.A.W.

 

[Shortround6]

The thing with P&W and Wright was that they were trying to top each other to gain a bigger market share. They also didn't really come up with alternate engines in each size class. That is to say P&W didn't come up with two different 30 liter engines and market them at the same time and neither did Wright.

P&W built the (their 3rd generation engines) R-1830 first and then the R-1535 to slot in below it. They first ran the R-2180 fourteen in 1936 and started work on a R-2600 eighteen cylinder engine. When they heard about Wright's R-2600 fourteen they slowed down on the R-2180 and brought the eighteen cylinder engine up to 2800 cu to top it. Meanwhile they kept improving the R-1830. Wright was improving the R-1820 and after building a few R-3350s dropped back to sorting out the R-2600 putting the R-3350 on hold. P W pretty much stopped development of the R-1535 and it saw very little commercial use. Military being interested for view over the nose. in the late 30s P &W dropped it. The 9 cylinder R-1690 lasting maybe a year longer in production than the 14 cylinder R-1535.

The US companies pursued two avenues to greater power, Larger displacement and higher boost and/or RPM as materials permitted.
The Sleeve valve was an attempt to go around some of the limitations of the poppet valve. It was hoped that the improvements in breathing and higher compression due to the theoretical absence of hot spots would allow the sleeve valve engines to make more power from equal displacement. Unfortunately for the sleeve valve the poppet valve development advanced just as fast.

Hemispherical (or near to it) combustion chambers allowed large valves and good breathing. The massive amount of fining on the head and around the valves and valve gear helped reduce the hot spot/valve problem (and this is not even a late war engine). These improvements allowed the poppet valve engines to increase their power out put compared to their displacement (new fuels helped too.)

 

[gjs238]

An article about the Hercules in which Feddon's claims for teh advantages of sleeve valves are shwon.

1941 | 2830 | Flight Archive

Courtesy of J.A.W.

One of the benefits mentioned in that article is cooler exhaust. Wonder if that would have been good (for the US) with turbochargers.

 

[Shortround6]

Some of the benifits are a bit over stated or apply to situations that may have been true at one time but were no longer true in 1940. One in particular needs looking at.

"j. Complete enclosure of all working parts, absence of external oil leads and impossibility of oil leakage.

Later model Mercury engine.

The statement could very well be true about comparing the sleeve valve to other Bristol engines but was much less true when comparing to some other radials. P W and Wright had long since given up on exposed valve gear and/or rocker arms/shafts lubricated with grease guns.

And as anybody who owned a British motorcycle or car of even the 1960s or 70s can tell you, the British may have had a different definition of "oil leakage" than the rest of the world

There are stories of Hercules powered glider tugs sitting on the ground with columns of smoke rising from the engine cowls after missions. Not as oil tight as hoped for?

 

[fastmongrel]

And as anybody who owned a British motorcycle or car of even the 1960s or 70s can tell you, the British may have had a different definition of "oil leakage" than the rest of the world

To be fair to the engine designers of those motorcycle or car engines the mobile oil slick was a quality control problem more than an engine fault. Take the Jag XK6 engine. Early engines were as tight as a Ducks exhaust pipe apart from the rocker cover which could twist if it wasnt torqued up precisely but later on as the factory was taken over and money got tighter and tighter the engine tooling wore out and more and more power was squeezed out of the ageing design then they could become leakier than a sieve.

In the shop we regulary see a XK150 as far as I can tell the engine is the original and on its 7th owner since 1960 yet it doesnt leak apart from a slight wet patch on the overdrive which is probably from the crank seal.

 

[Koopernic]

The Napier Nomad didn't have sleeve valves, and I'm sure it was significantly more efficient than the Jumo Diesels, with which it shared some heritage (Napier building some Jumo Diesels under licence).

I think the HCCI concept is different to what you describe. HCCi basically works as a compression ignition engine, but using petrol rather than Diesel fuel.

I am not sure about "ring cycle". There weere some toroidalshaped engines made by the Germans, known as swing piston designs, to mainly be used as gas generators for turbines.

The compression ignition CI or diesel cycle works by injection 100% of the fuel near top dead centre at the commencement of the down stroke, a high compassion ratio of around 20:1 ensures ignition. The Spark Ignition SI works by having the fuel air mixture a "Homogenous Mixture" already prepared on thee preceding down stroke. Ignition is controlled at top dead centre with a electrical spark.

The HCCI Homogenous Charge Compression Ignition HCCI engine works by having a fuel air mixture inducted on the down stroke. However ignition is not initiated by a spark but by a special fluid injected near top dead centre.

This eliminates the hot spot created by the spark plug that can cause preignition, allows much higher compression ratios (and therefore efficiency) while the method of ignition allows very lean mixtures to be run, which is also efficient.


http://www.fischer-tropsch.org/primary_documents/gvt_reports/BIOS/bios_1612.htm
Later, however, investigations centred on the use of the "Ring"
process. This process had the additional advantage that it made
feasible the use of high boiling point safety fuels. The work on the
"Ring" process had been summarised by O'Farrel in BIOS Report No.1609,
which also contains an extensive bibliography on the subject.

In the "Ring" process, ignition was produced by spraying a liquid into
the combustion chamber, at the appropriate moment in the compression
stroke. This liquid spontaneously ignited at the cylinder temperature,
thus igniting the main fuel charge. Diglycol diethyl ether and
butandiol diethyl ether were found particularly suitable as ignition
fuels. The former, which had a cetane number of 188, was manufactured
in quantity and was also used as a diesel starting fuel. The mechanism
of the self ignition of this fuel was thought to be a rapid
disintegration of the molecule under the action of heat. This
reaction, being exothermic, produced a rapid temperature rise causing
the products of the decomposition to ignite.

This of curse is a HCCI engine. There is another approach to HCCI engine ignition which involves recirculating exhaust gases, the proportion of which controls the ignition point.

Imagine an Me 109G14AS with the water methanol tank replaced with the special ignition fuel, the compression ratio raised from about 7.4:1 to 12:1 with about 50% more power for no increase in fuel consumption, no increase in thermal load on the engine and no need to lower critical altitude by using the supercharger to over boost.