Merlin power with Modern Tech but Unleaded Petrol

[GregP]

The Merlin 130 / 130 may have produce 2060 BHP but, if you DID improve it by 50%, it certainly wouldn't be with the same parts. Merlin rods break at about 2600 - 2800 BHP. None of the really fast "Merlin"-powered racing P-51s are using Merlin rods. That was established pretty solidly by actual racing emergency engine failures. Also, when the power gets to 3800 BHP, the Merlin engine block starts to twist. There was a racer named Dago Red, and the engine block was twisted 7° - 8° when the engine came to Joe Yancey's shop about 2014 or so. He had to deck the block to make it straight again and then line bore the mains to get them back straight when the new owners wanted to return the engine back to stock configuration.

I'm pretty sure, actually pretty certain, that the Merlin was near its design peak when the war ended. That's not to say a redesigned 27L engine couldn't do what you are saying, just not a Merlin. Since the Merlin made 990 HP or so (Merlin C) when it was first flown in the Spitfire prototype, I think it made remarkable power gains during the war. But, I'm betting a modern complete redesign would be required to make both 2,500+ BHP and also be reliable at an acceptable level for civil operations.

 

[pbehn]

The Merlin 130 / 130 may have produce 2060 BHP but, if you DID improve it by 50%, it certainly wouldn't be with the same parts. Merlin rods break at about 2600 - 2800 BHP. None of the really fast "Merlin"-powered racing P-51s are using Merlin rods. That was established pretty solidly by actual racing emergency engine failures. Also, when the power gets to 3800 BHP, the Merlin engine block starts to twist. There was a racer named Dago Red, and the engine block was twisted 7° - 8° when the engine came to Joe Yancey's shop about 2014 or so. He had to deck the block to make it straight again and then line bore the mains to get them back straight when the new owners wanted to return the engine back to stock configuration.

I'm pretty sure, actually pretty certain, that the Merlin was near its design peak when the war ended. That's not to say a redesigned 27L engine couldn't do what you are saying, just not a Merlin. Since the Merlin made 990 HP or so (Merlin C) when it was first flown in the Spitfire prototype, I think it made remarkable power gains during the war. But, I'm betting a modern complete redesign would be required to make both 2,500+ BHP and also be reliable at an acceptable level for civil operations.

The engine parts on the first and last Merlins merely looked the same, lots has had already been changed as it was developed. I have no doubt if you asked the people at RR in 1945 what would happen to a Merlin producing 3,800HP they would tell you. Even in 1945 if you wanted a 3,500 HP engine they had the Eagle, which was very similar to the Sabre. If you insist on 27L and V12 they had the Crecy, both engines were overtaken by the jet age.

 

[GregP]

The RR boys could NOT tell what a Merlin making 3800 HP would do because a Merlin won't make that power. It will throw a scrap iron fit long before that power level is reached.

Since I worked on WWII V-12 engines for awhile, I know that "late" parts aren't the same as "early" parts, but there really aren't THAT many late or early parts. In the Allison, you have early and late wrist pins, valve actuators, crankshafts, intake manifolds, magnetos, nose cases, and a few other odds and ends but, with some 7,000 individual parts, the ones that changed between late and early were very small in number.

Same for a Merlin. They changed heads, and a few other items, but not many. I'm not nearly as familiar with a Merlin as I am an Allison.

Cheers.

 

[pbehn]

The RR boys could NOT tell what a Merlin making 3800 HP would do because a Merlin won't make that power. It will throw a scrap iron fit long before that power level is reached.

.

I think they would have a good idea from calculation.

 

[Shortround6]

Modern tech would mean modern materials and quality control for things like connecting rods. It would mean modern bearing design and modern lubricants.

Both RPM and cylinder pressures could be increased. Ignition timing could be made variable to help accommodate this.

A lot depends on how far from the original Merlin you are prepared to go. However using 12 large cylinders does present cooling problems.
Unfortunately for the "just pile a bunch of small engines together to make 27 liters school" that never seemed to work very well.

Vibration problems go up with both the RPM and the number of cylinders and the gear train needed to link large numbers of smaller engines together was also a source of problems.

 

[GregP]

Hi pbehn,

I'll grant you they likely knew it wouldn't be running at 3800 HP, no matter what else they knew. Either way, they designed a really good engine of 27L that was at the top of the game in WWII.

 

[pbehn]

Hi pbehn,

I'll grant you they likely knew it wouldn't be running at 3800 HP, no matter what else they knew. Either way, they designed a really good engine of 27L that was at the top of the game in WWII.

What I meant was that although they used a lot of trial and error with reliability, running things until they broke and then modifying the broken bit so it didnt. RR like all manufacturers knew their stuff, the dimensions size and weights of all these engines and their components dont come out very similar by chance, they knew their stuff on material strength and properties. I would not be surprised at all if there had been calculations to see what would have to be changed if HP went to 2,500, 3,000 and 3,500 because I am sure they did some before taking it to 2,000, if the engine needs a complete re design then the Hornet isnt possible or also needs a complete re design too.

 

[wuzak]

The numbers I provided are from first hand experience.

OK, so 4 bar boost/5 bar MAP?

It seems that in the car world boost and map are often used interchangeably.

 

[Deleted member 68059]

OK, so 4 bar boost/5 bar MAP?

It seems that in the car world boost and map are often used interchangeably.

I`m not really supposed to give any exact figures, but I think its ok for me to give out ballpark figures, as
they`re also possible to simply back calculate from other released data. So in terms of the
maximum possible manifold pressure, in Absolute terms (i.e. gauge+ atmospheric)
if you said between 4 and 5 Bar you will be in the right area. More people may in fact have
managed to push that firmly towards the 5 bar end of that bracket, as it was 3 years since I worked on it.

 

[Koopernic]

If we resurrected the Merlin I think a couple of things would be different:
1 No Rich Mixture for increased power will be allowed. It's 2021 and dumping unburned hydrocarbons is unacceptable. Even NOX is seen as a greenhouse gas (the culprit is actually excess nitrate fertiliser use not defeat devices in automobiles).
2 Because of noise limitations turbo chargers will be required to muffle the sound.
3 You might even need a catalytic converter. Regulations for emissions are going to get tough.
Airbus is seriously looking at cryogenic hydrogen., they may be forced to, there looks like a European hydrogen pipeline is being established. In this political climate emissions must be controlled tightly.

 

[Koopernic]

I`m not really supposed to give any exact figures, but I think its ok for me to give out ballpark figures, as
they`re also possible to simply back calculate from other released data. So in terms of the
maximum possible manifold pressure, in Absolute terms (i.e. gauge+ atmospheric)
if you said between 4 and 5 Bar you will be in the right area. More people may in fact have
managed to push that firmly towards the 5 bar end of that bracket, as it was 3 years since I worked on it.

Do F1 engines have emissions regulations to meet? For instance are they allowed to run 'rich'

 

[wuzak]

Do F1 engines have emissions regulations to meet? For instance are they allowed to run 'rich'

No.

But they have fuel efficiency requirements.

The maximum fuel flow rate is 100kg/h and the maximum fuel for a race is 110kg.

F1 engines actually run very lean. Actually leaner than stoichiometric, rather than slightly less rich for the lean condition in WW2 aero engines.

 

[wuzak]

Airbus is seriously looking at cryogenic hydrogen., they may be forced to, there looks like a European hydrogen pipeline is being established. In this political climate emissions must be controlled tightly.

They are looking at fuel cell electric powered aircraft, rather than hydrogen combustion engines.

 

[Deleted member 68059]

No.

But they have fuel efficiency requirements.

The maximum fuel flow rate is 100kg/h and the maximum fuel for a race is 110kg.

F1 engines actually run very lean. Actually leaner than stoichiometric, rather than slightly less rich for the lean condition in WW2 aero engines.

New generation F1 engines use a system not too dissimilar in basic principle to that developed by IG Farben with pilot ignition by Diglycol-diethly-ether (aka. "R300"), this
allows stable and predictable running even at Lambda 2.5

This is ultra-lean terratory. (normal spark ignition is left hand graph, pilot turbulent jet ignition is right hand side, vertical axis
is BMEP, so basically analogous to engine power when comparing results on the same engine).

 

[herman1rg]

On the subject of using car engines in aircraft these are adapted from those that power smart cars and/or smart roadsters FlyEco - Innovative drives for Ultralights

 

[Koopernic]

They are looking at fuel cell electric powered aircraft, rather than hydrogen combustion engines.

Indeed they are. Check out Bjorn Fehrm's articles on leeham news, probably the best in the world at this time. Transcontinental cryogenic hydrogen fuelled Jets in the A321/A330 class will be powered by gas turbines. Fuel cells, their transmission cables etc are still too heavy. Cryogenic hydrogen engines have much more compact combustion chambers and benefit from cryogenic pre and intercooling.

Fuel cells will be used for the APU as there is a clear benefit in this area.

Fuel cell flight will likely find its way to propulsion of light and general aviation, about the size of a Britain Norman Islander but using compressed hydrogen at 700 bar. There are massive savings in maintenance to be made.

Toyota's Mirai fuel cell car seems to be taking of. Degussa says that the fuel cells now use less platinum than a catalytic converter. Issue is weight for aircraft.

Boeing is betting more on SAF "Sustainable Aviation Fuels" of which one component are the Carbon Neutral PtL (Power to Liquids) fuels derived from CO2 capture but even Airbus admit that for transoceanic flight SAF is the only way. Of course this means the internal combustion engine is here to stay though it will use carbon neutral hydrocarbons and may be part of a hybrid drive train.

Interestingly the cryogenic hydrogen will simply be carried in the tail of the aircraft. It is so light the C of G shift is acceptable.

 

[ThomasP]

re hydrogen fuel cell not liquid hydrogen

Whew!. For a moment there I was imagining a 7,000 mile range 250 ton airliner that turns in to a 250-220 ton (upto 30 ton explosive content) FAE bomb, depending how soon after TO it crashes.

edit: did my math wrong. corrected now.

 

[pbehn]

Hi pbehn,

I'll grant you they likely knew it wouldn't be running at 3800 HP, no matter what else they knew. Either way, they designed a really good engine of 27L that was at the top of the game in WWII.

Looking for stuff on another discussion I came across this from here Daimler-Benz DB 605 - Wikipedia I have put in bold the significant part. Engineers of the time had more than a rough idea of the strength of structures, although high power aero engines were quite new, things like locomotives and ships had much more power for a long time before and the principles are basically the same.

The primary differences between the 605 and 601 were greater displacement, higher revolutions, higher compression ratio and a more powerful supercharger. Engineers determined that the cylinders could be bored out to a larger diameter without seriously affecting the strength of the existing block. The change was small, increasing the cylinder bore from the 601's 150 mm to the 605's 154 mm, but this increased the overall displacement from 33.9 litres to 35.7. Altered valve timing increased the inlet period and improved the scavenging to give greater volumetric efficiency at higher speeds, which improved the maximum allowable RPM from 2,600 in the 601 to 2,800 in the 605. The combination of these changes raised power output from 1,350 PS (1,332 hp) to 1,475 PS (1,455 hp). Engine weight increased from 700 to 756 kg.

 

[Koopernic]

It seems that modern formulae 1 engines use HCCI ignition with spark as a backup. This had lead to 45% thermal efficiency, a 1/3rd reduction in fuel burn compared to the V8 era all with increased power. Certainly a modern V12 Merlin would look quite different in many areas in order to compete and meet regulations

 

[GregP]

Hi pbehn,

Making a block strong enough for the bores has been with us since internal combustion engines. They knew the strength of the metal they were using, certainly.

When Chevrolet went from a 350 cubic inch V8 to a 400 cubic inch V8 on the same block, the metal was strong enough, but they then didn't have room for coolant spaces between the center two cylinders, so the 400 always ran hot there. Being strong enough and being able to cool it sufficiently are not the same subject.

I think the DB 605 overhaul times were fairly low, I seem to recall they started at something like 100 hours and got to something like 200 hours. I am NOT very sure why German engineers set the overhaul interval so low, but I have seen quality of metal put forth as one reason. Whether or not that is the real reason is another question. The engineering for the DB series engines was first class; ditto the Jumos. Perhaps it was just being conservative.

Maybe our German members know, or maybe Snowygrouch knows ... ?