Spit Mk9 Post 3.006 Update

[unreasonable]

2 hours ago, JtD said:

I've only been reading up a little on the radiator relief valves fitted in various aircraft. The relief valve in the Spitfire was mentioned to relief itself at about 0.25at overpressure. Which might be enough for a glycol mix to reach the referenced water temperature limits. I also had a quick look at my Hurricane documents, and there the relief valve limit is also 0.25at, but followed by quite a bit of extra info which implies it's not all that simple. Before a bug report goes out, it would be nice to know the details of the Spitfire V and IX.

 

The point of relief valves is not so much to not damage the radiators, it's more about preventing the water from becoming hot enough to damage the engine. In this sense, time limits coming with temperature limits might also refer to losses of (pressurized) coolants.

 

Yes but only at sea level?  That is only 2500m worth of altitude.  Do any of your documents give instructions for pilots to observe temperature levels at altitude other than the standard numbers given in the PNs?  I cannot find any - if anything, the A2A manual suggests trying to keep your coolant at about 100 C.  A bug report has already been posted: with a bit of luck it might induce the devs to explain what their reasoning is. 

 

By comparison, since it is on the way, the P-51 manual says it's cooling system is pressurized to 30 PSI,  ie 2.1at with a maximum of 121 C and a desired range of 100-110 C. There is nothing in the manual to indicate that these temperature limits changed with height presumably because this level of pressurization is sufficient to maintain a boiling point above the maximums at maximum altitude.   

Edited October 3, 2018 by unreasonable

[CountZero]

Auto radiators stop function abow 5000m on stalingrad summer map (same on moscow autumn) i just run few tests on. I start in air in qm at 8000m after few min start to overheat and then i look from outide view and started to dive to see at what altitude my rads will start to react, and when i dived belwo 5000m they opend automaticly to full as engine is overheated all the time, then i climb abow 5000m and they close full even though my engine is overheated. So it reacts on that qm stalingrad summer up to 5000m abow that its like you dont have radiators and if you get overheated you need to open them manualy as they dont react.

Edited October 3, 2018 by 77.CountZero

[Talon_]

rad system

 

 

Spoiler

 

Radiator pneumatic system

 

Spoiler

 

 

@PainGod85

This part labeled "control cylinder"

 

Spoiler

 

Please note I am having to translate all annotations from a bad scan of a swedish document

 

RADIATOR FLAP ASSEMBLY:

 

Spoiler

 

Edited October 3, 2018 by Talon_

[Talon_]

Thanks to @Inkompetent it seems like part number 80 in the first diagram just behind the prop spinner is a thermostat for the header tank, showing the temperature after cooling.

 

I also found this from DCS which supports this:

 

 

 

My conclusion is that the Spitfire should maintain adequate pressure to not boil off coolant below 125 degrees on the gauge until ceiling.

Edited October 3, 2018 by Talon_

[unreasonable]

2.5 lb/in2 ? Is that a typo for 25, or does that mean the over-pressure compared to SL atmosphere? ie 14.7+2.5 = 17.2 lb/in2 in the system? 

 

In non-technical language does this mean that the valve system is working off the system pressure only, and the outside pressure is therefore irrelevant?

Edited October 3, 2018 by unreasonable

[HBPencil]

If those docs are Swedish, wouldn't they be for the Griffon rather than the Merlin? The first one has 'S 31' on it, the Swedish designation for the PR.XIX.

[Talon_]

On 10/4/2018 at 1:11 AM, HBPencil said:

If those docs are Swedish, wouldn't they be for the Griffon rather than the Merlin? The first one has 'S 31' on it, the Swedish designation for the PR.XIX.

 

They used the same cooling design right down to the engine-driven water pump, which had to be adapted to fit the Griffon engine.

On 10/4/2018 at 12:56 AM, unreasonable said:

In non-technical language does this mean that the valve system is working off the system pressure only, and the outside pressure is therefore irrelevant?

 

My suggestion is that the engine-driven pump header tank valve assembly just maintains adequate pressure up to +30psi over ambient at any altitude, maintaining boiling point at 135 degrees in-system.

Edited October 31, 2018 by Talon_

[MiloMorai]

Wouldn't the pump be only for the circulation of the coolant?

[Talon_]

Sorry yes I meant the header tank valve maintains the pressure. It's almost 2AM here!

Note the valve allows air both ways.

[unreasonable]

39 minutes ago, Talon_ said:

 

They used the same cooling design right down to the engine-driven water pump, which had to be adapted to fit the Griffon engine.

 

My suggestion is that the engine-driven pump header tank valve assembly just maintains adequate pressure up to +2.5psi over ambient at any altitude, maintaining boiling point at 135 degrees in-system.

 

Still not sure I have got this completely clear - do you mean +2.5 psi over ambient as in at SL or at the relevant altitude?  In the case of the latter, which is something like that which the game seems to be modelling as of now, it would not maintain a fixed boiling point since it would not maintain a fixed pressure. 

 

Still not sure if the valve is working on the pressure difference between inside and outside, or the absolute pressure inside alone. It would certainly be possible to design either: a spring in a vacuum chamber, for instance, will exert a force independent of the ambient pressure.

 

Sleep!

 

 

[JtD]

To share what I found so far:

 

Spitfire VIII F, LF, HF manual:

 

It's what it says in every Spitfire manual I have.

 

It should be emphasized that it is a "thermostatically" controlled relief valve and it might be more than just a pre-loaded spring as it is in simpler systems, like that of a Yak-1. I suppose that valve works the same way it does on the Hurricane, description below (just focus on the valve bits). Bottom line, it's +2.5lbs while it's cold (just thermal expansion of the coolant), +3.5lbs above saturated steam pressure and +30lbs maximum. Which would make sense and the last figure agrees with the P-51 description.

 

Edited October 4, 2018 by JtD

[unreasonable]

I think I have looked at every Spitfire PN except the Mk.VIII and the +2.5 psi is not mentioned in any of them    Good find though, especially the Hurricane stuff. 

 

Assuming Spitfire system = Hurricane system, does this mean that the game is interpreting the maximum pressure in flight as ambient plus 2.5 psi when it should be ambient plus 30 psi?

If the latter, then a glycol/water mix boiling at 104 C at SL unpressurized would have a boiling point of about 137 C at SL with 30 psi overpressure, and 125 C in outer space at 30 psi.  Which are pretty much in line with the recommended maximums.                                                                                                                                                                                                                                        Given your credibility with the developers I hope you can get this to their attention.

 

[JtD]

I left a PM with AnPetrovich, hopefully he finds the time to read it. I think on the bottom line the 30psi should be used, for consistency (P-51, Hurricane, Spitfire) and common sense. How else would the figures from the PN's make sense?

[[CPT]Crunch]

Spit V on a winter map, from just under 70 to 110 degrees in forty seconds when shutting rads from full open, than opening them will drop the temp right back in nearly the same amount of time.  Very hard to believe a coolant and system can dump and gain that fast, talk about thermal transfer efficiency.  Might be something goofy going on there also.

[PainGod85]

On 10/4/2018 at 1:56 AM, unreasonable said:

2.5 lb/in2 ? Is that a typo for 25, or does that mean the over-pressure compared to SL atmosphere? ie 14.7+2.5 = 17.2 lb/in2 in the system? 

 

In non-technical language does this mean that the valve system is working off the system pressure only, and the outside pressure is therefore irrelevant?

 

I read that as saying 'no less than' 2.5 PSI.

[Barnacles]

11 hours ago, [CPT]Crunch said:

Spit V on a winter map, from just under 70 to 110 degrees in forty seconds when shutting rads from full open, than opening them will drop the temp right back in nearly the same amount of time.  Very hard to believe a coolant and system can dump and gain that fast, talk about thermal transfer efficiency.  Might be something goofy going on there also.

Happens similarly in 109s and P40 too. 

[Talon_]

 

Got a picture of the header tank + valve for you guys on an earlier Merlin III engine.