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And if the had a liquid intercooler they'd be good to go right there.P-39 Expert said:P-63 was irrelevant in my opinion. Bell and the AAF could have installed the two stage Allison in a P-39 easily enough and had them from May '43 (when the engine was in production) instead of waiting until basically the end of '43 for the P-63 to get into production.
I'm confused, some people are telling me that it had ADI in lieu of intercooling, others a liquid intercooler...MIflyer said:And I did not say that they lacked the space for the intercooler. In fact, Allison designed and tested a liquid cooled intercooler (not aftercooler) for ther two stage engines, so there was no need to affect Merlin production, not there was any reason it would have.
And if the had a liquid intercooler they'd be good to go right there.
I'm confused, some people are telling me that it had ADI in lieu of intercooling, others a liquid intercooler...
When did they start research on liquid intercoolers?
Why did they do that?wuzak said:At some stage, Allison decided to change the 2 stage engine so that the carburettor was on the engine stage supercharger, like their regular single stage engines. The Auxiliary supercharger would bolt onto that and feed the carburettor with compressed air - sort of like a turbocharger would.
This arrangement precluded the use of a liquid:air intercooler, as there was no space.
OkayNo production two-stage V-1710 had any type aftercooler or intercooler but it was always intended to have one.
Why did they do that?
Agree, why they didn't start with the carb in the normal place on the back of the engine like the P-38 (and other turbocharged engines) is a mystery to me. The 3000' increase in critical altitude was significant. And with the carb on the engine the intake duct for the auxiliary stage didn't need to feed a downdraft carbueretor but could have been at any angle (updraft, downdraft, sidedraft or any other angle), greatly easing design problems. Probably caused by the AAF like a lot of other problems that Allison had (backfire screens, fuel injection, etc.). Hindsight is 20/20.The carburetor on the auxiliary caused a 2" hg drop in pressure at the inlet. In addition the Allison controlled the auxiliary stage speed by measuring the absolute pressure at the carburetor, this apparently caused the auxiliary stage to run slower than it should for a given altitude. Moving the carb between stages gained ~3,000ft in critical altitude.
This fit the profile for the V-1710's earlier on. Unless you were willing to add a pair of scoops to either side like the XP-39, you'd be shit out of luck.So the core engine would be the standard single stage V-1710 and the auxiliary stage would be a bolt on component.
What would the scoops be for?This fit the profile for the V-1710's earlier on. Unless you were willing to add a pair of scoops to either side like the XP-39, you'd be shit out of luck.
Agree, why they didn't start with the carb in the normal place on the back of the engine like the P-38 (and other turbocharged engines) is a mystery to me. The 3000' increase in critical altitude was significant. And with the carb on the engine the intake duct for the auxiliary stage didn't need to feed a downdraft carbueretor but could have been at any angle (updraft, downdraft, sidedraft or any other angle), greatly easing design problems. Probably caused by the AAF like a lot of other problems that Allison had (backfire screens, fuel injection, etc.). Hindsight is 20/20.
The three bends being in the duct from the auxiliary stage to the carb on the back of the engine?They probably put the carb body on the auxiliary stage to avoid the three extra bends needed.
Though I know I replied to this earlier, when they originally designed the liquid intercooler, they were designing the first and second stage with a liquid intercooler between them right? Why not a bolt-on intercooler and supercharger (this might sound stupid, but that's how you learn).So the core engine would be the standard single stage V-1710 and the auxiliary stage would be a bolt on component.
An air-to-air intercooler.What would the scoops be for?
Exactly. All contemporary Allisons were the same, improvements were normally applied to all the engine models. Only differences were the internal supercharger gear ratios which were interchangeable and the location of the reduction gear (conventionally on the "F" or remotely on the "E"). But the power sections of all the the Allisons were the same and the auxiliary stage supercharger was a bolt-on addition which worked on both the E and F models. So this was really not a new engine, just the auxiliary stage was new. No intercooler, WEP used water injection on the P-63 which was the only user of a production mechanical two stage Allison.So the core engine would be the standard single stage V-1710 and the auxiliary stage would be a bolt on component.
Though I know I replied to this earlier, when they originally designed the liquid intercooler, they were designing the first and second stage with a liquid intercooler between them right? Why not a bolt-on intercooler and supercharger (this might sound stupid, but that's how you learn).
An air-to-air intercooler.
...
No intercooler, WEP used water injection on the P-63 which was the only user of a production mechanical two stage Allison.
You are almost there.I know it's weird how sometimes you miss something totally, and then a day or more later it all connects
Okay, from what I gather
And if I understand the exchanges correctly (and I could be wrong)...
- Early V-1710: Had an integral supercharger with provision for a bolt-on supercharger and intercooler. When so configured: Airflow went from the carburetor intake to the auxiliary-stage supercharger, then to the air-to-air intercooler, and from that point to the inlet manifold. From this point it would go through the main-stage supercharger, and then to the cylinders.
- Proposed V-1710 Two-Stage Configuration: Airflow went from the carburetor intake to the first-stage, then second-stage superchargers, and from that point to the liquid-cooled after-cooler, which was integrated into the inlet manifold. From there it went to the cylinders.
- Technical problems popped up with the two-stage configuration with liquid-cooled intercooler/after-cooler including the fact that the configuration
- Caused a reduction in manifold pressure, whereas the earlier configuration (supercharger, carburetor, supercharger, cylinders) produced 3000 feet extra to the aircraft's critical altitude
- Auxiliary-stage speed was measured by absolute pressure in the carburetor, which resulted in the stage running slower than it should: Where did they normally control the auxiliary speed from? Why did they change it?
- They reverted to the earlier arrangement which had the bolt-on supercharger/turbocharger (take your pick), with the same configuration (supercharger, carburetor, supercharger, cylinders).
Far as I know all the ones used on fixed-wing, heavier-than-air aircraft employed them, those that were proposed for airships seemed the exception to the rule. I just used the term "auxiliary" stage for the second stage.You are almost there.
All Allisons (all WWII aircraft engines) had an internal supercharger.
It's not about the P-39/P-63, it's about the V-1710 design.Forget about the intercooler/aftercooler for the mechanical (not turbo) second stage. Never worked properly and there was no room in the P-39/63 structure. This was decided fairly early on in development.
Okay, I understand the layout.So, with no intercooler the order would be: Air ducted from outside into the carbueretor on the second stage, compressed by the second stage, ducted to the first stage and into the intake manifold and to the cylinders.