This is an engine question.

alspug

I primarily like alternate history due to the possibilities it presents. I also like the ASB because you can alter the course of history with relatively small changes to technology.

My question is looking at the Rolls Royce Merlin with the difference in performance from the First to the last and then thinking about the potentials modern improvements could make. Now I am not looking at computer controlled anything. I am looking at the basic engine and what could be done to make it more reliable and powerful with little effort.

Merlin Engine is a 27 liter 12 cylinder engine with a 60 degree Vee and running a carburetor along with superchargers. Plural. as in a two speed supercharger.

I would like to point out that I am a huge fan of the Allison engines of the same era as they had more development potential from what I know.

The Basic Merlin engine could have done with the following from very early to improve performance and not be ASB.

1: Fuel Injection either into the supercharger or into the cylinders. Diesel injection was done at the time and fuel pumps and direct injection existed but was not used.
2: Better superchargers or a turbo supercharger setup.
3: Better Fuel ie higher octane rating regardless of how you get it.
4: Higher production numbers and higher quality machining to improve the end product.

I am fully aware that some other engines such as the Bristol Engines could be improved just as much if not more with similar levels of assistance.

On a seperate note if a Merlin Engine was built today using modern equipment just how much power do you think could be produced on good reliability. Obviously I am thinking this would be Billet Heads etc with higher compression and the like. If a Merlin can produce 2,000hp by 1945/6 what could be produced using a full computer CNC 5 axis machine etc.
 

Schlock

Including more of the oil galleries in the block casting like they did on the succeeding Griffin engine. Less pipes to leak led to improved reliability. The other obvious change is to go with mechanical fuel injection instead of a carburettor as well. Also, automatic boost control on the supercharger.
 
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tomo pauk

alspug said:
Merlin Engine is a 27 liter 12 cylinder engine with a 60 degree Vee and running a carburetor along with superchargers. Plural. as in a two speed supercharger.

I would like to point out that I am a huge fan of the Allison engines of the same era as they had more development potential from what I know.
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Between 1936 and 1955, Merlin was either a better engine than the V-1710, or a much better engine than the V-1710.
Development potential is/was food for academic discussion, what counted was what was available, and Merlin there delivered in spades.
Merlin was with one supercharger (singular) until the Merlin 60 series was developed, the 2-stage S/C being the main improvement. 2-stages of supercharging can be described as 2 superchargers working in series.
Number of S/C speeds is one thing; number of S/C stages is another, and independent to the number of speeds. The 1st Merlin with 2-speed S/C was Merlin X, used in bombers (version(s) of Whitley and Halifax); supervcharger in question was still 1-stage, ie. single supercharger for a Merlin.

alspug said:
The Basic Merlin engine could have done with the following from very early to improve performance and not be ASB.

1: Fuel Injection either into the supercharger or into the cylinders. Diesel injection was done at the time and fuel pumps and direct injection existed but was not used.
2: Better superchargers or a turbo supercharger setup.
3: Better Fuel ie higher octane rating regardless of how you get it.
4: Higher production numbers and higher quality machining to improve the end product.
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1 - Calum Douglas posted the charts showing a 10% increase of power when test engines (mostly radials) were retrofitted with direct fuel injection and with incresed valve overlap (that was the main source of extra power, fuel injection took care of now wasting the fuel during the overlap; the losses induced by carb were also removed for extra power). COnversely, a better carb was providing extra 10 mph and increase of ceiling on a Spitfire V where the modern carb was retrofitted. Either of the two was less susceptible for carb icing, while the fuel injection also gave better mileage.
tl;dr - fuel injection is a material benefit, do it, and do it early
2 - Merlin was king of superchargers in the OTL.
That, a host of smaller and not so small changes in the power section, and ever better fuels kept it competitive. The earlier introduction of the Merlin 60 series would've helped it from early 1942, though, most notably with Spitfire and heavy bombers. A 3-speed drive for the S/C would've been interesting, both for 1-stage and 2-stage types. A better throttle body, like what Mikulin engines had (and what Jumo copied for the 213, or DB for the 603L and 605L) would've helped at lower and medium altitudes a bit.
Adding the turbo comes with the cost in internal volume required - good for bombers, less attractive for fighters?
3 - It have had access to the best fuel available per OTL. In order to increase the boost further, water-alcohol injection should've been used by mid-war, instead to wait for 1945 and the V-1650-9, that didn't make a combat sortie in the ww2 being too late.
4 - Yes, Allies could've used more Merlins, so the more the merrier.

alspug said:
I am fully aware that some other engines such as the Bristol Engines could be improved just as much if not more with similar levels of assistance.
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Yes, Bristol engines could've used the improvements, especially with regards to the superchargers used. After all, Bristol was setting altitude records in the 1930s with aircraft that were powered by 2-stage supercharged engines.

alspug said:
On a seperate note if a Merlin Engine was built today using modern equipment just how much power do you think could be produced on good reliability. Obviously I am thinking this would be Billet Heads etc with higher compression and the like. If a Merlin can produce 2,000hp by 1945/6 what could be produced using a full computer CNC 5 axis machine etc.
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Use alcohol fuel and NOx, make the engine DOHC + lighter pistons + connecting rods for 3500 rpm?
Americans were getting ~2250 HP with the V-1650-9 already by 1945, service machines.
Make the engine turbocharged-only, where the turbo drives a 2-stage S/C adds another 20% power to the prop since there is no need for engine to also turn the S/C, like it was done with the Wasp Major last versions.
Turbo-compound the engine, like that was mooted for the V-1710, that was supposed to do ~3000 HP.

My suggestions are for service engines; racing or tractor-pulling will do much more.
 
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alspug

The entire problem with many of the aircraft the RAF had in 1939-1942 suffered from not having a reliable 2,000hp engine. For example the Fairey Battle was anemic and only had 1030 hp and even an extra 500 or so HP would have made it viable for longer.

The Fairey Barracuda was designed again around a 2,000hp engine and instead had a 1600 hp engine if my memory is not faulty.
The Fairey Fulmar would have had Fairey Firefly performance if given the extra 900hp.

The changes without altering aircraft procurement are incredible.

An RAF force with every aircraft having better climb and level speed thanks to %70 more engine power for minimal weight gain would be incredible.

Spitfire I performance would be closer to the mark IX or early Griffon aircraft.

The Mosquito would be invulnerable due to speed and climb. Probably close to Hornet performance.
 

tomo pauk

alspug said:
The entire problem with many of the aircraft the RAF had in 1939-1942 suffered from not having a reliable 2,000hp engine.
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Let's not put the burden just on the engine choice. Nobody have had a 2000 HP engine in use between 1939-41, and even in 1942 there was seldom an aircraft with a reliable 2000 HP engine in service. Aircraft designers are still supposed to do their job in making their aircraft as streamlined as it gets*, and air ministries should have the knowledge about what to expect with engines that are in pipeline and the resulting A/C that use the engines. Many aircraft performed excellent with 1200 or 1300 HP engines, let alone with 1500 HP engines.
A 1500 HP engine with an excellent S/C might be worth more than a 2000 HP engine with an obsolete S/C, eg. see Merlin 61 vs. the over-boosted BMW 801D or Homare.
A 2000 HP engine with an excellent S/C will mean much more than a 2000 HP engine with an obsolete S/C.

*See Hurricane vs. Spitfire - 40-50 mph difference on same horsepower; See Typhoon vs. Fw 190 - same performance despite 2000 HP vs. 1600-1700; see Wildcat vs. Zero - 30 mph difference on same HP.

alspug said:
For example the Fairey Battle was anemic and only had 1030 hp and even an extra 500 or so HP would have made it viable for longer.

The Fairey Barracuda was designed again around a 2,000hp engine and instead had a 1600 hp engine if my memory is not faulty.
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Fairey Battle should've never existed in the 1st place.
Everyone in the air ministry worth their salt knew well that a 5 ton 1-engined bomber with a 422 sq ft wing (and thick wing) will be easily intercepted by a 2.5 ton fighter with a 260 sq ft wing, let alone by a 2.5 ton fighter with a 160-220 sq ft thin wing, provided that all of the 3 aircraft in question are powered with engines of similar power.

alspug said:
The Fairey Fulmar would have had Fairey Firefly performance if given the extra 900hp.

The changes without altering aircraft procurement are incredible.

An RAF force with every aircraft having better climb and level speed thanks to %70 more engine power for minimal weight gain would be incredible.

Spitfire I performance would be closer to the mark IX or early Griffon aircraft.
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Doubling the power of British engines by 1940 is firmly in ASB land, I'm afraid.
 

jlckansas

You have to worry about your power output with prop RPM because you start getting close or exceeding Mach 1 on the Prop ends and further down the prop itself. A good use would be with a extremely high altitude aircraft, whether a bomber, transport, or elint bird, that would be used in place of jets or turbo props.
 

fastmongrel

I think the proper answer is give Whittle some (lots of) money and give an order for a prototype to Boulton-Paul who will build the Defiant jet.
 

tomo pauk

jlckansas said:
RPM and prop diameter are the factors in blade speed. You need a specially designed prop to exceed the speed of sound on the tip and moving inward to keep the efficiency of the engine prop combination up where you need it.
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I don't want that prop tips came close to Mach 1, and the engineers that were making both props and engines were of the same opinion.
 
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