Advanced French Fighters vs 1942/1943 contemporaries (1 Viewer)

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Bretoal2 said:
For the 14R, this was of no interest since this engine's supercharger (in its second version with axial entry, from the 14R 04/05) had very high performances, with an efficiency close to 80%.
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For a frame of reference and out of curiosity; how does that 80% efficiency rating compare to other superchargers around the world during the same time period, on radials or otherwise?
From everything I've read, I'd imagine it would be a good bit better than the 801's supercharger and leaps and bounds better than the superchargers on Italian radials.
 

In the 1930s, it was quite difficult to compare the actual efficiency of superchargers from one country to another because the standards and test protocols were often quite different.

This difference in procedures is indicated by this American report (among many others) on the Planiol-Szydlowski S/C :


In the particular case of the Gnome & Rhône 14R 2-speeds S/C with axial entry, the same laboratory (Etablissement d'Essais des Moteurs, or EEMo, in Saint-Etienne in the "free zone") tested this S/C in the summer of 1942, as well, with same protocols and installations, as the Turboméca models (Planiol-Szydlowski) intended for the Hispano-Suiza 12Y and 12Z. The resulta are that the G&R S/C is almost as good as the Turboméca one.

The 80% value recorded by the EEMo is among the highest known in France at that time.

It is said that after the Bloch 157 was sent back to Villacoublay, its 14R engine was dismantled and sent to Germany, one may wonder if this S/C (more than any other parts of this engine...) with good efficiency was not of interest to DVL or BMW (BMW managed the Parisian factories of Gnome and Rhône). I have no proof, it is a simple hypothesis !
 
Have you already looked into the safran group database here: Media Library Patrimoine ?

I just realized today that they might have relevant info on the Hispano and G-R engines as well as Turboméca S-C, and indeed there are some Turboméca trials in 1942-44 and here some Gnome-Rhone trials.
 
FWIW, the S/C on the G&R 14R 05/05 was delivering 1180 mm Hg at 5000m (for 1580 HP at 2600 rpm), or ~46.50 in Hg, or about 1.61 ata; no ram effect in all cases.
The S/C of the BMW 801D was delivering ~1.55 ata at 5000m with tad of ram (for 1550 HP at 2700 rpm), at least when going with this chart. In the second gear at 5000-5500m, it looks like the difference of ~0.05 ata was 'worth' some 50 HP on the BMW 801D.
The 14R was not just turning lower RPM, but was also a much lighter engine than the 801 (that was probably over-built?), and also of the smaller displacement, while making better altitude power - kinda shows the importance of having a top-notch S/C. Granted, a sound military strategy >> a good S/C.
 
It might've been that French over-stated the efficiency of that S/C?
Eg. RR has never beaten the 75% efficiency on their superchargers, after many years of development (per this article, fig. 11). We know that Merlin XX was good for about +10.5 psi at 16000 ft (ie. about 1.77 ata at 5 km), with a S/C that was rated at 75% efficiency max at 2.5.1 pressure ratio (cue the S/C o the Merlin 50).
DB lines for were limited at 75% on their superchargers' maps for the DB 603A and 601E.

Granted, French methodology was possibly different than that of what the British or the Germans used. If that was the case, in a direct comparison and with the same methodology, either these other S/Cs are over 80% best-case, or the French S/C is under 75%.
 
B Bretoal2 Meanwhile I've been going into the rabbit hole of Hispano-Suiza 12Y-45 and onwards (including -51) in the Swiss and Safran archives. I'm sure I will be eventually able to gather enough info to make sense of all this, but do you have clear cut info on the power curves of -45, -49 and -51 (with H-S and Turboméca S-C).

I'm asking because -45 and -49 worked on both 87 and 93 octane fuel and -51 on -93 and -100 octane fuel, and depending on the documents I look at, the -51 is either a genuinely significant upgrade (+100hp) but in other data if seems that the -51 only adds a couple dozen horsepower. The values are all over the place.
 
tomo pauk How practical is it to apply very different supercharger designs to other engines than those they were originally intended for?

France ordered Allison V-1710 engines in 1939-40 to power American aircrafts (H-81/P-40 and P-38s without the turbocharger to use the same supercharger as the H-81s) as well as the Arsenal VG-32 fighter. However, the supercharging setup of early V-1710 was rather underwhelming, so how practical or fast would it have been to apply something like the Szydlowski superchargers, either directly adapted or just in principle? This would go a long way towards removing the only drawback of the V-1710 compared to French designs, as it was a generally better design than the Hispanos as far as the pure engine goes.
 
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A lot depended on the engine and S/C itself?
The RR engines went from 1-speed 1-stage S/C, paired with the 'bad' intake, to the 2-speed 1-stage unit with a good intake, and finally to the 2-speed 2-stage intercooled S/C. P&W engines 'acquired' the auxiliary stage of supercharging ia an elaborate piping and via a gearbox with 2 speeds an a neutral drive. Similar thing was done with the inter-war Bristol engines for altitude records.
Allison was succesfully tested with the 2-stage 2-speed S/C from the Merlin 60 series.
Jumo 213 went from 1-stage 2-speed S/C to the 2-stage 3-speed S/C with intercooler.

A long winded way to say that upgrades are/were certainly possible.

Several things need to happen before the S-P S/C can be installed as a compete unit, like the changed fuel delivery system (1 big carb vs. several smaller ones - might be tricky with two intakes, demanding two big carbs here?), and the beefier drive to the S/C (the original drive was too weak for the needs of a more capable S/C).

German engines, like their radials, might've been easier to mate with the S-P S/C (fuel injection, so no messing with the carbs). Or the Soviet engines?
 
This may depend on what you are trying to achieve and when.
The underwhelming Allison supercharger provided enough airflow for 1040hp at 4328meters (round off as you see fit.)
This compares to Szydlowsky superchargers on the 12Y engines that were providing enough airflow for either 920hp at 4200meters or 1000hp at 3260meters.

Both 'designs' could have been tweaked just a bit more, Allison adjusted in the inlet guides and a few other minor mods. What a 1941/42 Szydlowsky supercharger might have been capable off a 12Z maybe subject to debate.
But at what altitudes are quoted power ratings of the early 12Z being achieved at?

There was an Allison adapted to use a Merlin supercharger but it was a crude adaptation. They had to run the supercharger using an extension shaft and the supercharger was not part of the engine or bolted directly to it. They had to use some sort of cradle or frame and it might not have been a rigid as desired and/or didn't have the benefit of the cooling water in the back of the engine block being next to the supercharger?
Proper engineering might have been possible for production if the test rig had worked out.

The later Allison made the same 1040hp at 4328 meters (or close) but they were allowed to use high pressure at lower altitudes for the 1150hp rating at 3600meters (?)

Maybe they could have scaled up the Szydlowsky supercharger to handle more airflow fairly easy, Maybe the version intended for certain models of the 12Z was already larger.
 
Possibly the scale of the modifications required might be such that it would actually be closer to making a new supercharger with the same principles as the S-P (swirl throttle and impeller geometry if it's any better than the Allison S-C's geometry). Or possibly even a swirl throttle but with axial flow, much like the German and Russian swirl throttles (the former having been allegedly inspired by the S-P). The biggest benefit by far is the swirl throttle regardless since it allows a flatter power curve when climbing up to the rated altitude, which permits either greater low altitude power for the same rated altitude, or significantly better high altitude performance without sacrificing much low altitude power.

Unfortunately, IIRC NACA testing of the S-P was not done against American S-Cs.

Swirl throttles (axial types) seem to have otherwise only existed on Mikulin AM-42 and Jumo 213s, though an experimental DB-6 had one. I do not know when Polikovski worked on his swirl throttle (completely independently and possibly unaware of French developments). It is rather unfortunate that the French system didn't spread directly to the Soviet HS-12Y developments as this was probably the easiest possible integration option out of any non-French engines.
 
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It is quite possible (very likely) that the S-P supercharger was better but it seems to have been smaller (?) lower volume.
And then there is the time crunch.
The Allison has the intakes in the middle of the engine and there is no room for 4-6 carbs jammed in the middle of the engine without a really interesting intake manifold (can the pilot see over it?) With no cannon we may be able to accept some extra piping and bends to accept the standard S-P outlets. A lot of things can be done with time. But the French have got no time. Perhaps the Supercharger from the 12Z is bigger and will work. I have no idea of how big the 12Z supercharger was or if there was one 12Z supercharger or several between 1940 and the late 40s. This is not helped by the split between H-S Spain and H-S France and the Swiss off shoot. The Superchargers on the post WW II engines certainly seem to be flowing more air than the Allison.
For big power you need both pressure and volume.
 
Have you taken a look here?
The 1st Mikulin's engine with the Polikovskiy's device was a last member of the (A)M-34 family (note the peculiar curve of the -34FRN, that was also with a far better S/C than it's earlier siblings):



(click for hi-res)
 
For reference, the power curves for the Hispano 12Ys at the bench (without accounting for the ram air effect). Both the Hispano and S-P superchargers had an impeller diameter of 240mm and drive ratio of 10:1 except the 12Y-49's which had a 11.4:1 drive and the HS-12Y-51 (here with Hispano S-C) which reduced the impeller diameter to 225mm.

Manifold pressures were 880mm Hg nominal and 960mm Hg for takeoff for the 12Y-31, 45 and 49, 840 and 920mm respectively for the 12Y-29 (a 7:1 CR 12Y-31 which ran on 92/100 octane fuel instead of 85-87). The takeoff boost for -45 and -49 required 92 octane fuel, but 87 sufficed for normal operation. The 12Y-51 ran a 6.5:1 CR and 865mm Hg nominally (1025mm at takeoff) which allowed it to run on 92 octane fuel (early devs used 7:1 CR and 100 octane). Initially, a takeoff manifold pressure of 1140mm Hg was proposed for 1200 PS takeoff power.

The gist of it is that the higher CR of the 12Y-29 allowed a sizeable gain of 50+ PS at every altitude. The S-P supercharger improved low altitude so much that the 12Y-49 pretty much matched the low altitude performance of the 12Y-29 without the extra CR and higher octane requirement (the -45 was even slightly better), while dramatically improving performance up to 7500m, even exceeding the performance of the 12Y-51 with H-S supercharger. The 12Y-51 which ran on 92 octane fuel (100 octane for takeoff boost) like the 12Y-29, increased max rpm to 2500 instead of 2400 and featured some reinforcements managed to make yet another gain beyond the 12Y-29, increasing takeoff power by 200 PS, low altitude power by close to the same value, and high altitude performance by some 30 PS.

The ram air effect at high speeds increased the actual rated altitude by 1000m, with the maximum power actually being some 20-30 PS higher at the bench (and power at a given altitude above rated being much higher than without the ram air effect). The Swiss got to test the larger 1940 H-S supercharger with a drive ratio of 8.33:1 and a 4550m real rated altitude (the 12Y-31, 29 and -51 I talked about used the smaller version). With the S-P supercharger with drive ratio of 11.04 (likely 12Y-49 analogue), the rated altitude with ram effect for the 12Y-51 was 6400m (likely 5200-ish without ram effect). When comparing both S-Cs, the Swiss found out both were near identical up to 5000m with the Hispano having a marginal advantage of 5kph at most, but past that the S-P yielded a dramatic speed advantage of as much as 43kph at one altitude (difference between absolute top speeds was 20+ish kph) and 4 minutes to 10 000m (27 vs 31 minutes).

10-20 PS may be missing for some engines, depending on the sources. This is what I gathered from Swiss archives, the Safran database and claims in the Docavia book on Dewoitine 520.

12Y-45 vs 49 on the bench and 12Y-51 with H-S supercharger compared to the -45 and -49 of that curve:

The 12Y-45 had a 20-30hp advantage at lower altitudes, but the higher altitude performance of the 12Y-49 translated into a huge gain of up to 140 PS. One can also see that the H-S S/C -51 mostly held an advantage at lower rather than higher altitudes compared to the -49 and -45. However, the S-P S/C -51 would have probably leaped forward at all altitudes again, as I speculate with the curve in black (without accounting for the normally reduced throttling losses that the S-P would also provide).

The question that remains based on this info and that I will eventually try to answer one day when I go to the Hispano archives at Vincennes would be:

Did/could the 12Y-51 have been made to use an emergency rating at all altitudes instead of at takeoff by using 100 octane fuel as was possible with the later generation of engines (HS-12Z and GR-14S and R)? The HD-780 seafighter was to use a 12Y-51 with low alt S-C reaching 1050 PS at 1500m, which would indicate the engine was capable of handling extra power at low altitudes with the appropriate S-C. Possibly the Szydlowski S-C could have allowed or did allow such gains just as -45 vs -31. In which case there might/could have been a last intermediate power increase until the 12Z enters service.



As for the 12Z other than the values given on the Internet, unfortunately the 12Z-17 manual just gives 1150 PS nominally, 1300 PS at takeoff and 1500 PS on emergency power with a rated altitude of 6300, 6700 and 5900m respectively (very weird), using a Turboméca supercharger.

The only curve is the 1946 12Z on 100/130 octane fuel with 2-speed 296mm diameter Hispano-Suiza supercharger with 6.72 and 9.25 drive ratios (6200m rated altitude):

The only data mentioned in Docavia are 1110 PS at sea level, 1320 PS at 4750 m (or out to 7000m), 1210-1225 PS at 5850 or 6850m. The highest rated altitude figures are 7000-7500m as development of the S-P supercharger continued.

Turboméca continued work on the S-P supercharger, once testing a modified version with intermediary vanes and a 280mm impeller diameter in 1943. They once tested 2-speeds, as did the Spaniards in 1944. IMO a 2-speed gearbox would definitely have happened if France was not defeated, if only fielded by 1942-43.



Interestingly enough, I also found a document relative to an underground final assembly and testing plant of Hispano Suiza engines that was envisionned since 1939 and started work in March 1940. This was to be located in the quarries of Jonzac, 500km away from Paris on the Paris-Bordeaux line, thus far from German bomber bases and also better protected against enemy bombardment. This was to be scaled for a monthly production of 800 HS-12Y/Z a month. 15 000 square meters could be used, of which 5000 were cleaned up and prepared by late June 1940.
 
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I have these about the 12Y-45, 49 and 51 (date : 1942).


In the table, it is strange that datas "puissance au décollage avec surpression" and "pression d'admission autorisée au décollage" (takeoff power with overboost - allowed manifold pressure at T/O) are blank for 12Y-45 and 49. Same for the "puissance nominale au sol", "puissance nominale à l'altitude d'adaptation" and "altitude d'adaptation" (rated power at S/L - rated power at altitude - rated altitude) that are missing for the 12Y-49 - but on the other hand the curves for this engine are published, and not the other ones!

Let's see that datas "Quantité de chaleur à évacuer par l'huile" and "Quantité de chaleur à évacuer par le liquide de refroidissement" (Heat quantity to be evacuated by oil and heat quantity to be evacuated by the coolant) are higher for the 12Y-51, which shows that this engine must have been really more powerful than the other ones in this family.

I believe the table shows that Hispano-Suiza intended to build the 12Y-51 with its own supercharger : the rated altitude is only 3,250 m, well below what was allowed by the Szydlowski-Planiol (Turbomeca) S/C. And the engine length is same as the 12Y-31, 120mm less than the 12Y-45/49.
 

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For the 12Z, I have these curves too.

And a personal pic of the (big) 12Z Turbomeca supercharger, with well-known twin inlet, but single outlet :
 

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Some thoughts: the Dewoitine 520 took on average 6000-7000 man-hours to produce while the D551 was supposed to take 4000 hours with further optimization for production. The Bloch 15X series were estimated at 8000 hours in March 1938 but no data for actual production in 1940. The VG33 line didn't get time to show the man-hours during sustained production.

I have sometimes seen figures for 12-22 000 man-hours for Spitfires. Are there reliable figures for the man-hours it took to produce non-French Allied fighters as of mid 1940 and 1941?
Would it be valid to consider that the modern French fighter airframes at least had the saving grace of taking less effort to produce than other Allied fighters? Of course that would only serve to partially alleviate the smaller size of the French aero industry compared to British and US ones - even after the 1940-41 expansions are complete.
 
A lot of interesting informations here :

 
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Returning to this topic. As of 1940, the two main domestic engine development lines for French aircrafts were the HS-12Y-->Z and the GR-14N-->R, with the GR-14M-->S only really suitable for light support aircrafts as the war goes on.

But France's contemporaries had a lot more engine families developped or used during WW2. The British had Merlin, Griffon, Sabre, Vulture (for a bit), the Bristol radials. The Germans had countless designs, as did the Americans.

In comparison it seems that the French had fewer domestic developments, especially for fighters. This might be a blessing given the technical and production gap to fill if the French can concentrate limited means on only a few types of engines.
The GR-18R is at least a fairly straightforward path to a R-3350 analogue for bombers but might be too large for fighters.

The other "radials" all seem meant for very large aircrafts, maybe not even military, and incorporate more than 2 rows so are rather complex: the Mathis Vega, the Potez 28D, and Voisin 42M.

The only engine which seems small enough for fighters is the SNCM 130/137, kinda reminiscent of the Jumo 222 but perhaps too complicated to ever be ready and reliable for WW2?

SNCM 130 and 137 24-Cylinder Aircraft Engines

The SNCM 130 was a hexagonal 24-cylinder aircraft engine designed in France just before WWII. A slightly smaller prototype version, the SNCM 137, was built and tested before the German invasion.
oldmachinepress.com

So are the French stuck with using the 12Z and GR-14R as domestic powerplants for fighters?
 
Elan Vital said:
So are the French stuck with using the 12Z and GR-14R as domestic powerplants for fighters?
Click to expand...

No... as commercial agreements were signed with Bristol and Rolls-Royce in England, and Pratt & Whitney in the USA (the disastrous experience of the Hispano-Suiza 14AA and 14AB meant that no one wanted to hear about Wright in France) to build these firms' products under license.

But there was a sort of convergence of interests (I dare not calling this conspiracy...) from French officials and industrialists to ruin these projects. As well as to make people believe that the national engines were better. Which wasn't really true...

You may read these articles (in French) by P.-Y. Hénin on the SAM 40 website.

Hercules et Merlin : les projets inaboutis pour doter l’aviation française de moteurs anglais | SAM40

sam40.fr

L’Affaire Pratt & Whitney : histoire méconnue d’un contrat sabordé | SAM40

sam40.fr
 
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