Spit Mk9 Post 3.006 Update

[-TBC-AeroAce]

Ok so, 

 

I believe that the MK9 is now bugged. 

 

The issue is due to the automatic radiators (I do not mean assists as the MK9 rads are controlled automatically).

 

Very simply the rads do not seem to open what so ever when the engine starts to overheat. 

 

I think that after the new update for the lower boil temp of coolant due to the lower pressure at altitude, the figures used for the radiator system to actuate the rads have not been updated. This has the result of the rads not opening when the engine is overheating. 

 

When I fly it now and get into an overheat situation the rads will not open what so ever, which has got to be a bug or oversight.

 

The only way I can now fly the MK9 is by opening the rads in manual mode which will only open 100% or nothing, which clearly gives a big disadvantage.

 

Devs please look into this  and PS I am not saying that the boiling of coolant at altitude is a problem, it is that the rads do not seem to be responding to any increase in temp because the boiling point is a lot lower than what it used to be, and my assumption is that the code that controls the rads is using the old figures, hence why they dont open. 

 

Thanks 

 

Aero

 

@Jason_Williams

 

@Han

 

 

 

Edited September 29, 2018 by AeroAce

[unreasonable]

I would like clarification on this too.  A Spitfire IX should be able to climb to maximum altitude at 2850rpm and 12lbs boost without overheating, except perhaps in the most extreme tropical conditions.  We know this because it was tested to do so.

 

Taking off on Kuban Autumn map and then climbing at 180-200 mpg at these settings (slightly under given the difficulty of getting exact settings on my throttle) the temperatures rose quickly towards the top of the temperature range and my radiators were open - checking outside view.  So far so good - up to about the gear change the temperatures stabilized at the top end of the rated range - 115 C for coolant. 90 C for oil.  No problem since the maximum for coolant is 135 C. (Presumably the SL value).

 

Over about 20,000 ft the temperatures are beginning to drop to well inside the rated range, so I checked outside view again - and my radiators are 1) closed  and 2) streaming coolant.

 

I do not know if this is incorrect or not: but given that I still had a long way to go to reach maximum operating altitude I was to put it mildly surprised by that combination.

 

 

 

 

Edited September 29, 2018 by unreasonable

[BlitzPig_EL]

I'm struggling to understand how a pressurized cooling system would be at all effected by changes in altitude, and one filled with an ethylene glycol mix to boot.

Certainly an open pan of water, or a kettle filled with pure water would have it's boiling point changed as altitude increased.  But a capped off, pressurized cooling system filled with a glycol mix?  The mechanical pressure cap on the system would maintain whatever pressure in the system that the cap was calibrated for, regardless of altitude.

[-TBC-AeroAce]

1 hour ago, BlitzPig_EL said:

I'm struggling to understand how a pressurized cooling system would be at all effected by changes in altitude, and one filled with an ethylene glycol mix to boot.

Certainly an open pan of water, or a kettle filled with pure water would have it's boiling point changed as altitude increased.  But a capped off, pressurized cooling system filled with a glycol mix?  The mechanical pressure cap on the system would maintain whatever pressure in the system that the cap was calibrated for, regardless of altitude.

 

I dont understand how a closed system can leak also but I was told that there is a pressure bypass value that allows coolant to escape if it boils. But I still don't get that because it is boiling because it is at a lower pressure?

 

 

Could someone that knows what they are talking about please explain. 

 

Also bear in mind that the problem with the spit atm is nothing to do with boiling/leaking. It is that the rads just plainly do not seem to be opening at all in response to temperature change, so don't turn it's into a thread about the boiling/leaking and if that is correct or not.

Edited September 29, 2018 by AeroAce

[unreasonable]

19 minutes ago, AeroAce said:

 

I dont understand how a closed system can leak also but I was told that there is a pressure bypass value that allows coolant to escape if it boils. But I still don't get that because it is boiling because it is at a lower pressure?

 

 

Could someone that knows what they are talking about please explain. 

 

Also bear in mind that the problem with the spit atm is nothing to do with boiling/leaking. It is that the rads just plainly do not seem to be opening at all in response to temperature change, so don't turn it's into a thread about the boiling/leaking and if that is correct or not.

 

I disagree - when I climbed the Spitfire IX with the radiators on automatic, they were clearly opening as the temperatures rose. I checked frequently in external view and they were quite obviously open at low altitude and high temperature.  The problem was that at high altitude the temperatures are dropping - presumably enough to tell the radiators to close, which they eventually do - yet the glycol starts boiling off.  If you like I will run again and do some screenshots to demonstrate, but it is easier to see for your self: just go to outside view every two or three thousand feet and look at them.

 

As I understand it most cooling systems had a pressure release valve, so that if the difference in pressure between inside and out gets above a set limit the valve opens and some pressure is relieved.  Since the external pressure drops with altitude, and the maximum difference in pressure in and out is set constant by the valve, the pressure inside the system will also drop as the valve releases the over-pressure.    

[Ehret]

At higher altitudes not only temperatures are going down but the air pressure, too. So, radiators could be getting lower mass of air through them, even if it's colder. I'm not sure how much but this should affect the cooling efficiency.

 

Another thing is that the cooling liquid containers and pipes aren't ideally stiff. Lower external pressure will expand them even if by a little.

[Barnacles]

I saw a article about this in ww2 planes. Basically the factors are: lower air mass flow (basically lower IAS) offset by lower air temperature and lower power produced by the engine above full throttle height. The conclusion was that broadly the cooling systems generally are around as effective at all altitudes. I can't remember the paper mentioning anything to do with lower boiling points.

 

[-TBC-AeroAce]

1 hour ago, unreasonable said:

 

I disagree - when I climbed the Spitfire IX with the radiators on automatic, they were clearly opening as the temperatures rose. I checked frequently in external view and they were quite obviously open at low altitude and high temperature.  The problem was that at high altitude the temperatures are dropping - presumably enough to tell the radiators to close, which they eventually do - yet the glycol starts boiling off.  If you like I will run again and do some screenshots to demonstrate, but it is easier to see for your self: just go to outside view every two or three thousand feet and look at them.

 

 

I was not really taking about lowers alts as the problem from the boiling is clearly not there, I did actually just confirm that they do open at low alt but that is not where the problem is. 

 

If you go above 10k ft they will not open because as you say the temperature is lower. But as the boil temp is also lower the rads do no open even if it is boiling. 

 

So I guess the question is: IRL did the system know to lower the temperature of which to open the rads based of an increase of height/decrease in pressure to compensate for the lower boiling point?

 

They defo do not open up high which makes the plane really bad at the moment, I had a G2 owning me at 25k ft where as before I would be all over it.

1 hour ago, unreasonable said:

As I understand it most cooling systems had a pressure release valve, so that if the difference in pressure between inside and out gets above a set limit the valve opens and some pressure is relieved.  Since the external pressure drops with altitude, and the maximum difference in pressure in and out is set constant by the valve, the pressure inside the system will also drop as the valve releases the over-pressure.    

 

Ahh there we go, that makes sense.

 

Lol and just a random side note as we are talking about the MK9. Does anyone think the trim wheel moves too fast?

 

Edited September 29, 2018 by AeroAce

[RedKestrel]

I found some pilots notes online here: http://www.avialogs.com/viewer/avialogs-documentviewer.php?id=2521
 

The notes say that the radiators are fully automatic and are designed to open when coolant reaches 115 degrees Celsius. I skimmed them and didn't find anything about changes at high altitude. Its possible the radiator temp gauge in-game is reading too low, and the 115 is calibrated to sea level...so the game starts boiling off coolant before you can see that it would be a problem. 

I don't know enough about the systems to speculate further.

[=EXPEND=13SchwarzeHand]

50 minutes ago, 71st_AH_Barnacles said:

I saw a article about this in ww2 planes. Basically the factors are: lower air mass flow (basically lower IAS) offset by lower air temperature and lower power produced by the engine above full throttle height. The conclusion was that broadly the cooling systems generally are around as effective at all altitudes. I can't remember the paper mentioning anything to do with lower boiling points.

 

 

As unreasonable mentioned, the boiling point is irrelevant and maybe just a misinterpretation of what An P. was saying.

He mentioned the “boiling point” of the yak

to be at 110*C. To my knowledge this can only be reached at sea level, if the water glycol mixture is about 50%.

AFAIK mixtures were not that high, so what I think he really means is that the release valve of the pressurized cooling system is set to release the coolant once the difference between outside pressure and pressure inside the cooling system ( which also depends on temperature) reaches 110*C inside of the system - and standard temp and pressure at sea level.

As you gain altitude the outside pressure drops. The valve will thus start releasing coolant at lower temps (inside pressures) than before.

So the phrase “boiling point” is somewhat of simplification or wrongly used to describe the SEA LEVEL Temperatur for which the release valves are set and has nothing to do with the actual physical boiling.

Edited September 29, 2018 by =EXPEND=SchwarzeDreizehn

[-TBC-AeroAce]

And just to turn this into a complete mess of a thread.

 

So if the coolant system vent valve is actuated by the difference in pressure  (internal vs air pressure), isnt the pressure of system until it needs to vent maintained at ground level pressure as the system has not opened yet? And if so why would the boiling point of the coolant reduce with altitude as the system is closed until it opens and equalises the pressure? Conversely as the coolant can boil at a lower temperature than that of sea level because of reduced pressure, that would mean that would mean the system is open even before the vent valve is opened and the  coolant pressure would be at the same pressure as the air, so how would there be a difference in pressure in the first place to actuate the venting?

 

My head hurts

 

Im not speaking like the above are facts, Im just trying to understand the system.

Edited September 29, 2018 by AeroAce

[Barnacles]

8 minutes ago, =EXPEND=SchwarzeDreizehn said:

 

As unreasonable mentioned, the boiling point is irrelevant and maybe just a misinterpretation of what An P. was saying.

He mentioned the “boiling point” of the yak

to be at 110*C. To my knowledge this can only be reached at sea level, if the water glycol mixture is about 50%.

AFAIK mixtures were not that high, so what I think he really means is that the release valve of the pressurized cooling system is set to release the coolant once the difference between outside pressure and pressure inside the cooling system ( which also depends on temperature) reaches 110*C inside of the system - and standard temp and pressure at sea level.

As you gain altitude the outside pressure drops. The valve will thus start releasing coolant at lower temps (inside pressures) than before.

So the phrase “boiling point” is somewhat of simplification or wrongly used to describe the SEA LEVEL Temperatur for which the release valves are set and has nothing to do with the actual physical boiling.

Yes I think you're absolutely spot on. I reckon the boiling expression is a misnomer the 'boiling' happens in the vapour once it's vented to atmosphere. Of course boiling can happen in a pressurised system but that is not necessarily the same as the pressure relief lifting.

[-TBC-AeroAce]

6 minutes ago, 71st_AH_Barnacles said:

Yes I think you're absolutely spot on. I reckon the boiling expression is a misnomer the 'boiling' happens in the vapour once it's vented to atmosphere. Of course boiling can happen in a pressurised system but that is not necessarily the same as the pressure relief lifting.

 

ahh 

Edited September 29, 2018 by AeroAce

[Barnacles]

Anyway in this manual https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://zenoswarbirdvideos.com/Images/spit/SPIT9MANUAL.pdf&ved=2ahUKEwiO5M-o7-DdAhUmz4UKHTCtBIkQFjASegQIAhAB&usg=AOvVaw1lmsslkgfhPIEkgwhR2U63 applicable to the Merlin 70 and 66, it says the radiator flap open button is purely for testing the operation of the flaps. There's no mention of the need to override auto radiator in any flight regime. Like Jason says there's been some big changes so they'll need to sweep up some emergent issues, but it looks like this is one of them

[-TBC-AeroAce]

33 minutes ago, 71st_AH_Barnacles said:

Anyway in this manual https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://zenoswarbirdvideos.com/Images/spit/SPIT9MANUAL.pdf&ved=2ahUKEwiO5M-o7-DdAhUmz4UKHTCtBIkQFjASegQIAhAB&usg=AOvVaw1lmsslkgfhPIEkgwhR2U63 applicable to the Merlin 70 and 66, it says the radiator flap open button is purely for testing the operation of the flaps. There's no mention of the need to override auto radiator in any flight regime. Like Jason says there's been some big changes so they'll need to sweep up some emergent issues, but it looks like this is one of them

 

Cool,

 

Im not trying to aggressively shout about a bug. I was more interested in learning about the system and finding out what MAY be wrong. 

 

Im sure we will hear about it from the devs.

[Barnacles]

https://ww2aircraft.net/forum/threads/me-109-f-vs-spitfire-coolant-radiator-installations.31940/

 

There are some interesting posts on this link. Also someone had access to a test that said the spit IX would not exceed 100 c coolant temperature in level flight with radiator flaps in minimum drag position ( closed ) at 25lbs MP at full throttle height in summer conditions.

 

Hope they have a fiddle with this plane along with the 190a8 which seems to suffer from an unusual amount of overheating.

 

 

[novicebutdeadly]

7 hours ago, AeroAce said:

 

I dont understand how a closed system can leak also but I was told that there is a pressure bypass value that allows coolant to escape if it boils. But I still don't get that because it is boiling because it is at a lower pressure?

 

 

Could someone that knows what they are talking about please explain. 

 

Also bear in mind that the problem with the spit atm is nothing to do with boiling/leaking. It is that the rads just plainly do not seem to be opening at all in response to temperature change, so don't turn it's into a thread about the boiling/leaking and if that is correct or not.

Could it act the same way that a car's radiator cap does??

When the engines coolant exceeds a certain pressure due to heat expansion it pushes up a release valve (spring) in the cap that allows coolant to escape.

If there is no overflow bottle (traditional type) it will vent on to the ground (or air for an aircraft), and only has a one way spring valve (if it has a overflow bottle it has a two way valve that allows coolant to go from the reservoir back into the radiator if the coolant pressure drops) that should not be affected by outside air pressure.

I could be entirely wrong since I don't know much about spitfire's, but it seems logical,

or maybe the gauge is showing the coolant temp after  the radiators not before (but then again the manual should give correct figures)???

Hopefully this gets sorted for you guys soon.

 

[Barnacles]

55 minutes ago, novicebutdeadly said:

Could it act the same way that a car's radiator cap does??

When the engines coolant exceeds a certain pressure due to heat expansion it pushes up a release valve (spring) in the cap that allows coolant to escape.

If there is no overflow bottle (traditional type) it will vent on to the ground (or air for an aircraft), and only has a one way spring valve (if it has a overflow bottle it has a two way valve that allows coolant to go from the reservoir back into the radiator if the coolant pressure drops) that should not be affected by outside air pressure.

I could be entirely wrong since I don't know much about spitfire's, but it seems logical,

or maybe the gauge is showing the coolant temp after  the radiators not before (but then again the manual should give correct figures)???

Hopefully this gets sorted for you guys soon.

 

Generally the difference I think is that the aero engine's radiator cap has a valve to prevent the system drawing a vacuum as well as to prevent overpressure. Eg whilst descending.

[ZachariasX]

8 hours ago, novicebutdeadly said:

When the engines coolant exceeds a certain pressure due to heat expansion it pushes up a release valve (spring) in the cap that allows coolant to escape.

The Spit has a relif valve just behind the propeller, where coolant vapour is released in case of excessive heat. AFAIR it is the right side and gives the pilot a visible cue for overboiling coolant.

[CountZero]

i think there is more then few bugs now added to game with this new temp, i can see this new watter steam overheating starting from airplane but no messages give in techchat that airplane is overheating, so if your flying alone you dont know your overheating as you dont know at what temperatures now you start to overheat at diferant maps altitudes and so on, if your flying at 1-2km your ok but if you fly high your screwed now. They didnt bather to explain how this works now in game, do we trust in what techchat say or when effect starts ( they dont behave same) i had tm8 just fly normaly got watter steam for few min and then all of suden engine stoped, with no messages and all temps normal, so how the heck should we know when engine is overheating now when techchat dont work correctly for high alts. I think like some one say probably rads dont get correct info to open beter as you get higher and start to overheat for spitfire, low probably all works but high not.  Yesterday flaying on WoL i fly up to 6km and never get overheat message, but had steam coming out of airplane many times even on 100% open rads, so was the engine geting damaged when i see steam or when techchat says so like before, this is not explained when they added this new temp calculations.

Edited September 30, 2018 by 77.CountZero

[Talon_]

The Spitfire is definitely suffering from a bug. The Merlin 66 should not overheat in level flight at +25lbs boost manifold pressure in summer conditions, and we have only +18lbs boost pressure currently.

 

Furthermore you can see visually that the radiators fail to open.

Edited September 30, 2018 by Talon_

[PainGod85]

1 hour ago, Talon_ said:

The Spitfire is definitely suffering from a bug. The Merlin 66 should not overheat in level flight at +25lbs boost manifold pressure in summer conditions, and we have only +18lbs boost pressure currently.

 

Furthermore you can see visually that the radiators fail to open.

 

That's just the symptom. From what I'm piecing together in this thread, the Spit's coolant system behaves as if it wasn't pressurized.

 

Now, we know the maximum permissible constant temperature for the Merlin's water is 115 °C, and we also kow its maximum permissible temperature with a 5 minute time limit is 135 °C.

 

We also know the engine uses a 70/30 mix of water and glycol, which boils at 104 °C under slightly below normal pressure. This means at that point the liquid's vapor pressure is the same as the atmosphere's - 1013 hPa (or pretty much 1 bar, which I will be using from here on out).

Now, since the coolant lines are pressurized, let's invert and apply the old lab technician's rule of thumb: for every time external pressure is halved, the boiling point is expected to drop by 10 K.

Inverted, it means for every time the pressure in the system is doubled, the boiling point is expected to increase by 10 K.

 

104 °C - 1 bar

114 °C - 2 bar <- This is basically as close as we'll get to 115 °C with the method. Personally, if the glassware I've used in laboratories can withstand  high vacuum of 12 mbar, steel piping should have no issue at all with a mere 2-3 bar of absolute internal pressure.

124 °C - 4 bar

134 °C - 8 bar <- The same as above. Make it around 8.1 or even 8.5 bar just to be on the safe side.

 

We can expect the pressure inside the cooling system to be slightly above 8 bar bar absolute at 135 °C as the progression follows a logarithmic scale.

 

And now for the kicker: Since we're not flying our planes in a vacuum, we need to subtract our external pressure from the absolute pressure inside our system. That's 1 bar at sea level, around 0.5 bar at 5500 m and 0.25 bar at 10,500 m.

 

Which would make our delta-p anything from 7 to 7.75 bar at maximum permissible temperature, and anything from 1 to 1.75 bar at maximum continuous permissible temperature.

 

As an observation, the engine is probably incapable of heating the coolant system to 135 °C at very high altitude, since it reaches its critical altitude at around 5 km or so.

 

http://www.avialogs.com/index.php/en/aircraft/uk/supermarine/spitfire/ap-1565i-pilots-notes-for-spitfire-ixxi-xvi.html

http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0985/0901b80380985f78.pdf?filepath=/heattrans/pdfs/nore

 

@Talon_, since you volunteer at the Spitfire museum, what do the engineering notes say about testing the cooling system for leaks, and to which pressure differential to set the relief valve?

[unreasonable]

@PainGod85 I wondered about that, but hesitant to opine lacking an engineering background.

 

This is not on the Spitfire but the P-51: presumably somewhat related, but I will leave that to others to determine, and mentions pressure of up to 50lbs/sq inch (4.5 bars relative to vacuum) more or less in line with your 124 C estimate. 

 

https://www.aircorpsaviation.com/mark-on-maintenance-p-51-header-tanks/

[PainGod85]

Bear in mind 10 K is less than the minimum reduction I've personally encountered in a lab (with water, watery solutions of alcohols and various organic compounds, up to and including aromatics), so we can expect the 10 K increase in boiling point with the rule inverted to be less than what we will end up getting.

 

I haven't had the time to go look for a chart on how the glycol/water muxture's boiling point changes under pressure.

[-=PHX=-SuperEtendard]

It's a problem with either the Spit coolant boils too soon, or the radiators don't adjust correctly.

The automatic rads open when the temperature reaches around 120ºC, and mantains it. However at high altitude the coolant starts to "boil" at lower temperatures, so the radiator doesn't act in order to control this. For example, the plane can't reach it's level top speed at 6850 meters properly because when using +18 boost at 3000 RPM the coolant starts to get vented outside the radiators, and since they are lower than 120ºC, they don't open.

I don't know how the auto rads worked IRL, but with this logic I think they would have an altitude-regulated control, making them open at lower temperatures the higher the plane goes, to avoid the coolant being vented off.
 

[Poochnboo]

Let's see if I'm understanding this. Are you guys saying that the rads are reacting to air pressure rather than coolant temperatures? 

[Guest deleted@83466]

3 minutes ago, Poochnboo said:

Let's see if I'm understanding this. Are you guys saying that the rads are reacting to air pressure rather than coolant temperatures? 

 

No, they're saying that the coolant boils off at a lower temperature at a higher altitude, and the radiators don't keep the coolant cool enough to prevent it from vaporizing at those lower boiling points.

Edited September 30, 2018 by SeaSerpent

[Poochnboo]

I see. So the radiators are reacting to only one temperature, rather than compensating for the changes that occur at various altitudes.

2 minutes ago, SeaSerpent said:

No, they're saying that since the coolant boils off at a lower temperature at a higher altitude, and the radiators don't keep the coolant cool enough to prevent it from vaporizing at those lower boiling points.

 

[Guest deleted@83466]

8 minutes ago, Poochnboo said:

I see. So the radiators are reacting to only one temperature, rather than compensating for the changes that occur at various altitudes.

 

 

Well, or I would just guess that the relief valve just isn't allowing an adequate pressure differential between inside the system and outside.  I wouldn't be inclined to think that anything would or should change in the operation of the radiators themselves, only that the valve needs to allow higher differential.  So at lower altitude, your coolant could be overheating to dangerous levels, but you wouldn't necessarily be venting steam overboard.

Edited September 30, 2018 by SeaSerpent

[Talon_]

5 hours ago, PainGod85 said:

@Talon_, since you volunteer at the Spitfire museum, what do the engineering notes say about testing the cooling system for leaks, and to which pressure differential to set the relief valve?

 

Sadly the library is as basic as a less specific WW2 museum, most of the important stuff is in Farnborough or the National Archives. I'll ask around when I'm back in but don't expect anything too soon!!

[PainGod85]

1 hour ago, SeaSerpent said:

 

No, they're saying that the coolant boils off at a lower temperature at a higher altitude, and the radiators don't keep the coolant cool enough to prevent it from vaporizing at those lower boiling points.

 

1 hour ago, Poochnboo said:

I see. So the radiators are reacting to only one temperature, rather than compensating for the changes that occur at various altitudes.

 

 

No, we're saying the threshold for when the overpressure relief valve installed in the pressurized cooling circuit engages is improperly modeled. The relief valve should not be triggered until the coolant has reached a point above 135 °C at any altitude as that is the 5 minute manual limit. Personally, I would expect the relief valve to to be set to open at around 145 °C so the pilot doesn't have to baby the gauges during combat.

 

3 hours ago, -=PHX=-SuperEtendard said:

It's a problem with either the Spit coolant boils too soon, or the radiators don't adjust correctly.

The automatic rads open when the temperature reaches around 120ºC, and mantains it. However at high altitude the coolant starts to "boil" at lower temperatures, so the radiator doesn't act in order to control this. For example, the plane can't reach it's level top speed at 6850 meters properly because when using +18 boost at 3000 RPM the coolant starts to get vented outside the radiators, and since they are lower than 120ºC, they don't open.

I don't know how the auto rads worked IRL, but with this logic I think they would have an altitude-regulated control, making them open at lower temperatures the higher the plane goes, to avoid the coolant being vented off.
 

 

That would be an excessively complicated mechanical design, and probably prone to failure especially in wartime conditions. You're better off reinforcing the relevant piping to withstand higher pressures by adding 20 kg or so to the overall design than attempting to dynamically account for the 500 mbar the system is lacking at altitude because the engineers were somehow too stupid to use any kind of safety factor.

 

They were already playing the pressurized cooling system game, might as well engineer it in such a way the pipes will hold unless the pilot abuses it intentionally to cause relief valve activation.

[Poochnboo]

I had thought that the radiators simply work off of a thermostat.

[=EXPEND=13SchwarzeHand]

11 minutes ago, PainGod85 said:

The relief valve should not be triggered until the coolant has reached a point above 135 °C at any altitude as that is the 5 minute manual limit.

 

What makes you think that the release trigger has anything to do with the maximum allowed temperature? I´m wondering whether it would make sense to set the max allowed temperature at a something that is higher than the coolant release and rather at a level at which the engine takes damage. These two values do not have to be consistent as far as I can tell.

[Guest deleted@83466]

35 minutes ago, Poochnboo said:

I had thought that the radiators simply work off of a thermostat.

 

Probably.  And I'll bet the pressure relief valve is just a simple thing that closes or vents in relation to the differential pressure.   Like Black 2 says, I'm going to take a wild guess and say the valve doesn't "know" anything about the temperature of the coolant, it only opens or closes because of the pressure.  Again, I'll bet it simply needs to be tweaked to handle a higher relative pressure diff.

 

 

 

[BlitzPig_EL]

It shouldn't work off pressure differential.  ONLY on the internal pressure of the cooling system, that is all that matters.

[PainGod85]

24 minutes ago, BlitzPig_EL said:

It shouldn't work off pressure differential.  ONLY on the internal pressure of the cooling system, that is all that matters.

 

You don't understand how pressurized systems work. The only thing that determines when a pipe bursts (or a relief valve gets actuated, for that matter) is pressure differential. If you took the Spit's cooling system and pressurized it to 1004 bar while in a pressure chamber at 1000 bar, the valve would not be actuated, the same way it wouldn't be actuated if you pressurized it to 5 bar under a standard atmosphere.

 

The difference is the same, hence the valve behaves the same.

 

14 hours ago, =EXPEND=SchwarzeDreizehn said:

 

What makes you think that the release trigger has anything to do with the maximum allowed temperature? I´m wondering whether it would make sense to set the max allowed temperature at a something that is higher than the coolant release and rather at a level at which the engine takes damage. These two values do not have to be consistent as far as I can tell.

 

Because once a relief valve gets actuated, it generally dumps all your coolant in substantially less than 5 minutes.

E: Actually, they used a pop-off valve on the P-51. Odds are the same is true for the Spitfire.

Edited October 1, 2018 by PainGod85

[=EXPEND=13SchwarzeHand]

1 hour ago, PainGod85 said:

Because once a relief valve gets actuated, it generally dumps all your coolant in substantially less than 5 minutes. 

E: Actually, they used a pop-off valve on the P-51. Odds are the same is true for the Spitfire.

 

I´m sorry but i really think you are wrong. A pop off valve is usually a security device that - as the name points out - pops off in case the blow off valve doesnt work. The blow off valve in contrast to the pop of valve can shut itself again. I am very sure they used a pop off valve in the P-51 in addtition to the blow off valve.

 

So the pop off valve causes you to drain all your coolant. It would be very stupid to only install a pop of valve, becuase then you would loose all your coolant regardless if you stay at 135* for 5 minutes or not, because once its popped (which is when you reach 135*C) you are basically screwed, which is if I´m not mistaken, your view of how the cooling security system works. It canot work the way you describe it - or it would be an utter failure in engineering.

 

You also make the mistake of viewing the boiling point stated by An P. as the actual physical boiling point, but disregard that he might have actually meant the temp at which the blow off valve is activated, (again the blow off valve releases more or less coolant realtive to pressure and does not dump everything within 5 minutes) which taking everything into account is what he was probably actually talking about, but got lost in translation, as many things are when the moderators need to filter the Russian devs info to the english forum.

Edited October 1, 2018 by =EXPEND=SchwarzeDreizehn

[ZachariasX]

5 minutes ago, =EXPEND=SchwarzeDreizehn said:

So the pop off valve causes that you drain all your coolant.

As you say, the pop off valve is just another layer of security on top of the blow off valve. If the blow off valve is actuated by excessive pressure, you can see the steam escaping on the front right side next to the propeller (at least Mk.I and Mk.II had them in that location), giving a visual cue "that you are boiling". As soon as temp/pressure decreases, the valve will close again. I'm not so sure they had a pop off valve installed though, usually these are field modifications if you get the impression that the blow off valve is not reliable enough. And then it would pop at considerably higher pressures than when the blow off valve would get actuated. As for the pop off valve popping over Berlin in a P-51, there's really no difference to the engine blowing rods. There's really little safety mediated by that thing.

 

But the main point is that outside athmospheric pressure another specific amout of pressure that your internal system can toletate. If your system will whistle at 5 atmospheres internal pressure, at sea level it will actuate at 4 athmospheres pressure differential. At 10 km altitude, you have no more then 4.25 atm pressure in your system before it starts whistling.

[PainGod85]

3 minutes ago, =EXPEND=SchwarzeDreizehn said:

 

I´m sorry but i really think you are wrong. A pop off valve is usually a security device that - as the name points out - pops off in case the blow off valve doesnt work. The blow off valve in contrast to the pop of valve can shut itself again. I am very sure they used a pop off valve in the P-51 in addtition to the blow off valve.

 

So the pop off valve causes that you drain all your coolant. It would be very stupid to only install a pop of valve, becuase then you would loose all your coolant regardless if you stay at 135* for 5 minutes or not, because once its popped (which is when you reach 135*C) you are basically screwed, which is if I´m not mistaken, your view of how the cooling security system works. It canot work the way you describe it - or it would be an utter failure in engineering.

 

Quote

 

PRESSURIZED COOLANT SYSTEM (POP OFF VALVE)

The header tank assembly was provided from the factory with clamps, cap, and a pop-off valve P/N SA3817-C30 produced by Standard Aircraft Products. We recommend using a fresh new old stock valve with seals that have been replaced and tested to meet AN 03-1-21, Operation, Service and Overhaul Instructions with Parts Catalog for Coolant Relief Valves (Standard Aircraft).

 

 

This is for the P-51. And yes, being screwed once it pops was my point, thanks.

 

3 minutes ago, =EXPEND=SchwarzeDreizehn said:

You also make the mistake of viewing the boiling point stated by An P. as the actual physical boiling point, which has nothing to do with the temperature at which the blow off valve, which taking everythnig into account is what he was actually talking about, but got lost in translation.

 

I think you're missing a verb there. And I have no idea who or what An P. is supposed to be.

 

That said, what is even your point? I didn't directly connect the coolant's boiling point at normal ambient pressure to the one the liquid would have once pressurized.

[ZachariasX]

10 minutes ago, PainGod85 said:

This is for the P-51.

Ha, thanks! That is the one on the header tank then!

Spoiler

 

Also found this:

 

They installed several "safety devices". Must be likewise in the Spit.

Edit: The one you posted looks really like the "relief valve" it is labeled as on the drawing. It is not what we called a pop off valve in the sense that is a "predetermined breaking point", but just a valve operating in the very exact same fashion as on your steam cooker. And on the drawing they show two of those.

 

Edited October 1, 2018 by ZachariasX