Chin radiator with horizontal radiator matrix

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z42

Senior Airman
649
422
Jan 9, 2023
In the interminable discussion threads about liquid cooling radiators on this site and elsewhere, one complaint against chin style radiators is that there isn't space to tuck a big radiator matrix up into the fuselage, similar to the P-51, as the engine gets in the way.

I was looking at the Red A03, a current day 6L V-12 aero diesel engine producing around 400 kW . The manufacturer also provides a chin style radiator for easy integration into existing aircraft, and an interesting detail there is that the radiator cores are mounted (more or less) horizontally.
red-a03-Airvent.jpg


This provides a relatively low frontal area installation, although in this case it doesn't really make much, if any, use of the Meredith effect, and also it seems the radiator exhaust is directed downwards rather than backwards.

One can see a few pictures of aircraft with this installation at Aircraft with RED engines – RED Aircraft

Was anything like this experimented with in the WWII era? It seems some of the later annular radiators used slanted radiator cores, IIRC on the Ta 152 and on the post-war annular radiator prototypes for the Napier Sabre, but I'm not aware of any chin style radiators with this kind of arrangement.
 
Inlet is maybe suitable for "chin" style installation, but it seems the radiator matrix is not at all parallel to the incoming airflow....

And what about outlet(s) ??

I bet the general aerodynamic balance is not really good !
 
I looked at the web site but all the videos are missing.

The interesting part, to me, was in the Yak conversion

The YAK-18T is a single-engine aircraft. Types such as these have a greater requirement for the utmost reliability. The RED A03 features two-cylinder bank redundancy, each of which is capable of independent operation. This significantly increases safety in the operation of the engine. The FADEC also stores and monitors engine data, allowing early identification of potential problems. This can also serve to reduce the potential downtime when maintenance is required.
 
I looked at the web site but all the videos are missing.

I noticed that too. Though if you search for "Red A03" on YouTube you can find videos showing aircraft with the engine mounted.


The interesting part, to me, was in the Yak conversion

The YAK-18T is a single-engine aircraft. Types such as these have a greater requirement for the utmost reliability. The RED A03 features two-cylinder bank redundancy, each of which is capable of independent operation. This significantly increases safety in the operation of the engine. The FADEC also stores and monitors engine data, allowing early identification of potential problems. This can also serve to reduce the potential downtime when maintenance is required.

I have to admit I don't understand exactly what has been done to improve fault tolerance, compared to a "standard" road or marine diesel engine. My guess would be several independent high pressure fuel injection systems (pumps, common rail distribution, injectors, plus electronics to control it), though still with only one injector per cylinder. So if one of the injection systems fail the engine can continue operating albeit with reduced power.

As for the FADEC storing and monitoring engine data, I think that is fairly standard for FADEC systems these days.
 
but it seems the radiator matrix is not at all parallel to the incoming airflow....

Yes, that was kind of the main point in my initial message that started this thread..

And what about outlet(s) ??

I bet the general aerodynamic balance is not really good !

I wouldn't be so sure about that. A couple of points:

  • If you look at the kind of aircraft they're targeting, they have max speed in the 300-350 km/h range. Quite a big difference in drag at 300 km/h vs 700 km/h for a late WWII fighter.
  • Given how the GA market works, such a complete firewall forward package is probably necessary to have any chance of success. Radiators mounted somewhere else on the airframe would just drive the expense and complexity of a conversion project beyond reach.
  • Compared to WWII, today we have a better understanding of aerodynamics and CFD allows quick iteration of a design.
  • I would also guess that today we can produce more efficient radiator matrixes than in the WWII days.
 
Yes, that was kind of the main point in my initial message that started this thread..



I wouldn't be so sure about that. A couple of points:

  • If you look at the kind of aircraft they're targeting, they have max speed in the 300-350 km/h range. Quite a big difference in drag at 300 km/h vs 700 km/h for a late WWII fighter.
  • Given how the GA market works, such a complete firewall forward package is probably necessary to have any chance of success. Radiators mounted somewhere else on the airframe would just drive the expense and complexity of a conversion project beyond reach.
  • Compared to WWII, today we have a better understanding of aerodynamics and CFD allows quick iteration of a design.
  • I would also guess that today we can produce more efficient radiator matrixes than in the WWII days.

Yes, but what I meant is that, on one hand, the engine radiator matrixes are purely and simply perpendicular to the incoming air flow, and that nothing is provided for evacuation, otherwise lower multiple parallel small slots or rear larger slots in the cowling. Most of them seems to only benefit engine cooling. Where does the flow leaving intercoolers pass?

In short, it seems to me that none of the three flows passing through this system (intake, engine cooling, intercooler) are really ducted. And it is not because the equipped planes are said "slow" that we can ignore the elementary laws of aerodynamics.
 
Yes, but what I meant is that, on one hand, the engine radiator matrixes are purely and simply perpendicular to the incoming air flow, and that nothing is provided for evacuation, otherwise lower multiple parallel small slots or rear larger slots in the cowling. Most of them seems to only benefit engine cooling. Where does the flow leaving intercoolers pass?

In short, it seems to me that none of the three flows passing through this system (intake, engine cooling, intercooler) are really ducted. And it is not because the equipped planes are said "slow" that we can ignore the elementary laws of aerodynamics.
If you look at the pictures of aircraft with this setup, they seem to have exit flaps underneath the radiator. Sure, no extra thrust from the Meredith effect when the exhaust is directed downwards, but at 300 km/h probably not a huge deal.

As for the general approach of having the radiator matrix not perpendicular to the airflow, that doesn't need to be a problem. E.g. F1 cars do it. The plenum just has to be designed to provide an even pressure distribution across the radiator matrix. Perhaps requiring lots of wind tunnel testing in the WWII days, but today should be doable with CFD.

But I agree with one point you make, however, namely based on the pictures I don't understand the intercooler airflow.
 
If you look at the pictures of aircraft with this setup, they seem to have exit flaps underneath the radiator. Sure, no extra thrust from the Meredith effect when the exhaust is directed downwards, but at 300 km/h probably not a huge deal.

As for the general approach of having the radiator matrix not perpendicular to the airflow, that doesn't need to be a problem. E.g. F1 cars do it. The plenum just has to be designed to provide an even pressure distribution across the radiator matrix. Perhaps requiring lots of wind tunnel testing in the WWII days, but today should be doable with CFD.

But I agree with one point you make, however, namely based on the pictures I don't understand the intercooler airflow.

Like both you and Bretoal2 I too do not understand all the airflows because there is too little information available.

I do however understand the concept behind the "horizontal" coolers and will try and explain.
Lets take a mythical cooler 1 cubit square and 1 knuckle thick. If the cooler is mounted vertically so that the matrix is in line with the airflow the frontal area is 1 square cubit but the air flowing through it is only a fraction of that because of the volume of the matrix itself. This is demonstrated in the P-51 installation where the scoop is far smaller than the frontal area of the radiator/oil cooler itself and Meredith effect is included.

Now lay the matrix horizontal and the frontal area is only 1 knuckle by one cubit plus the area of the scoop, which is the perfect size for the volume of air required, plus the area of the exhaust. Far smaller.

Now let us go one stage further again. If the matrix is mounted at an angle so that the front is at the bottom of the scoop and the back is at the top of the scoop then the total frontal area is now only only 1 knuckle by one cubit plus the area of the exhaust and is the perfect size for the volume of air required. Again we have reduced the frontal area with no loss of cooling effect. Some Meredith effect could be obtained by having internal shutters that restrict airflow to prevent over cooling but I suspect they just follow automotive practice and use thermostats. That eliminates the shutters and the resultant weight savings would offset the lost thrust to a certain extent.
 
This is demonstrated in the P-51 installation where the scoop is far smaller than the frontal area of the radiator/oil cooler itself
This has nothing to do with the actual matrix passage section, but attempts to improve the radiator efficiency by slowing air flow while increasing its pressure. This is called the venturi effect.

and Meredith effect is included.
The Meredith effect is not inherent to the system, but is only caused by the ducts and exit nozzle which ends the assembly. Unless I'm mistaken, I don't see the slightest duct or nozzle in any of the Red A03 installations. Which confirms that we need to stop talking about the Meredith effect all the time, a true Meredith effect is very rare... ALL radiators heat the air passing through them, the difference is what happens behind it !!
 
Like both you and Bretoal2 I too do not understand all the airflows because there is too little information available.

I do however understand the concept behind the "horizontal" coolers and will try and explain.
Lets take a mythical cooler 1 cubit square and 1 knuckle thick. If the cooler is mounted vertically so that the matrix is in line with the airflow the frontal area is 1 square cubit but the air flowing through it is only a fraction of that because of the volume of the matrix itself. This is demonstrated in the P-51 installation where the scoop is far smaller than the frontal area of the radiator/oil cooler itself and Meredith effect is included.

Now lay the matrix horizontal and the frontal area is only 1 knuckle by one cubit plus the area of the scoop, which is the perfect size for the volume of air required, plus the area of the exhaust. Far smaller.

Now let us go one stage further again. If the matrix is mounted at an angle so that the front is at the bottom of the scoop and the back is at the top of the scoop then the total frontal area is now only only 1 knuckle by one cubit plus the area of the exhaust and is the perfect size for the volume of air required. Again we have reduced the frontal area with no loss of cooling effect. Some Meredith effect could be obtained by having internal shutters that restrict airflow to prevent over cooling but I suspect they just follow automotive practice and use thermostats. That eliminates the shutters and the resultant weight savings would offset the lost thrust to a certain extent.
No, this is not the idea behind horizontal or angled radiators. The problem is that the heat transfer between the coolant and the air is proportional to the temperature difference. So a horizontal radiator, or equivalently a very thick radiator with a small frontal area is much less efficient than a thin one with the same volume, as at the back of the thick radiator the air has already been heated by quite a lot and thus transfers heat less efficiently.

Rather, the idea is to turn the airflow. So if you have a horizontal radiator the air entering the scoop makes a 90 degree turn as it passes through the radiator matrix. And then if you want thrust from the radiator exhaust it makes another 90 degree turn in order to exhaust straight rearwards.

See figure 13 in https://www.arpnjournals.org/jeas/research_papers/rp_2016/jeas_0316_3840.pdf for a F1 radiator.

The tricky part is how to achieve this. Inside the radiator matrix there are baffles or channels directing the air, but the intake (and exhaust) plenum must be shaped to generate a constant pressure across the radiator face, to make sure all parts of the radiator receive the same airflow.
 
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There was an interesting article on F1 cooling F1TV a couple of weeks back, where they mentioned micro-tube exchangers. I had never heard of them before, but it appears F1 teams are making use of this interesting technology.
Why Microtubes?: Mezzo Technologies
The circular arrangement appears to lend itself to making use of the Meredith effect.
Microchannel heat exchangers are indeed fascinating. An impressive example being the micro-tube heat exchanger on the Sabre air breathing rocket engine, which cools down the inlet air, which reaches up to 1000C at hypersonic speeds, down to - 150C. Using helium as the heat exchange fluid, ultimately dumping the heat into the liquid hydrogen fuel.

 

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