TERS : Thermal Energy Recovery System

[trinidefender]

Is active clearance control permitted within the rules?

No. It has to be fixed geometry.

Many aircraft have a semi active system. Well I guess you can call it that. The outer tips of the blades are made of an abradable material that as the blades heat up and expand wears down bit by bit. This ensures that at the correct operating temperature limits the blades are still within spec clearance wise from the housing.

Don't have a clue if this used in F1 though

[gruntguru]

Interesting. I wonder if that has ever been done on radial inflow turbines. The region of critical clearance for a radial inflow turbine is the curved section of the impeller rather than the very tip.

[trinidefender]

Interesting. I wonder if that has ever been done on radial inflow turbines. The region of critical clearance for a radial inflow turbine is the curved section of the impeller rather than the very tip.

Bit of read but provides some useful information: http://www.google.com/patents/US5704759

Don't see why it can't be applied there. Has been applied to gas turbine blades whether they be aircraft, power station, ships or what have you for quite some time now.

[gruntguru]

Thanks trinidefender. It appears easier to implement on axial compressors where the blades are often individual components but no doubt it could be done on a centrifugal.

[Brian Coat]

Aero engines also control clearances actively by modulating airflow to the casing.

This is to allow for the fact that the engine is not so hot in cruise as in climb, so the clearances go up.

Is variable cooling fixed geometry?

[Brian Coat]

Aero engine abradable liner ensures minimum possible clearances at top of climb but they still vary with temperature and other effects.

I'm guessing that on a small device like a turbo this absolute limit can be found through experimentation, then the geometry optimised, but only for a certain running conditions.

This paper is interesting ...

http://www.imeche.org/docs/default-sour ... f?sfvrsn=0

[trinidefender]

Aero engines also control clearances actively by modulating airflow to the casing.

This is to allow for the fact that the engine is not so hot in cruise as in climb, so the clearances go up.

Is variable cooling fixed geometry?

When you say casing what do you mean exactly? The combustion chamber? Or the casing around the combustion chamber that is used to carry cooling and combustion dilution air flow? Or something else?

Well the abradable liner is actually to treat a different condition than only thermal expansion. It is used to also treat what is known as blade creep. After thousands of hours running the compressor blades can actually "grow" by up to a few millimetres. This helps the keep the clearances within spec as the blade grows outward toward the compressor housing. It also does the job of taking care of thermal expansion to however as it is on the compressor side and not the hot turbine side there isn't nearly as much thermal expansion.

[Brian Coat]

Apologies trinidefender I was talking about two different parts of the engine in the two posts and I did not make it clear.

Abradable liners of the type described in the patent above are used in the *compressor* and are different to those in the turbine.

"A few mm" of high temperature creep growth in compressor blades is puzzling me ...

Where the temperatures are higher at the back end of the compressor there is very often no liner. And some engines don't use abradable liners at all in the compressor. The creep growth you describe would be a disaster in such cases?

For clearance control I was referring to the *turbine* and I mean the turbine casing not the combustion casing, the geometry of which cannot be used to control clearances, of course. Here is a brief description of the method.
http://en.m.wikipedia.org/wiki/Active_t ... ce_control

Clearly a few percent of MGU-H efficiently would be very worth realising and there probably lots of things to try, even if the geometry is not allowed to be variable.

[gruntguru]

I'm sure it could be argued that active clearance control is not "variable geometry" - more a system to maintain "constant geometry"

[riff_raff]

The abradable coatings used in turbine engines are normally applied to the casing surface around the axial compressor stages. Leakage past the tips of the HP compressor blades can have a big effect on efficiency. And as the pressure across the stage becomes higher, like that in the final stages of a turbofan engine with a 50:1 PR, the tip leakage becomes more of an issue. It can also be difficult to control blade tip clearance with engines that have large, thin, flexible casings.

An abradable liner on the inner surface of a centrifugal compressor housing could be beneficial, as long as it could be made to work without damaging the tips of the compressor wheel. Leakage past the tips of a centrifugal compressor creates the same issue as in an axial compressor.

[trinidefender]

Apologies trinidefender I was talking about two different parts of the engine in the two posts and I did not make it clear.

Abradable liners of the type described in the patent above are used in the *compressor* and are different to those in the turbine.

"A few mm" of high temperature creep growth in compressor blades is puzzling me ...

Where the temperatures are higher at the back end of the compressor there is very often no liner. And some engines don't use abradable liners at all in the compressor. The creep growth you describe would be a disaster in such cases?

For clearance control I was referring to the *turbine* and I mean the turbine casing not the combustion casing, the geometry of which cannot be used to control clearances, of course. Here is a brief description of the method.
http://en.m.wikipedia.org/wiki/Active_t ... ce_control

Clearly a few percent of MGU-H efficiently would be very worth realising and there probably lots of things to try, even if the geometry is not allowed to be variable.

Well the thing is before the abradable liners were introduced, compressor blades had a much shorter lifespan. Now many aviation engine components have a much higher limit with a "on condition" maintainence program tacked on which can allow, in special cases' to allow the engine to go passed overhaul times. Before because there were no liners after very little blade creep the compressor blades would have to be changed. Very costly and time consuming considering all the blades have to be dynamically balanced as a set. Also as engines have got larger, so have compressors, diameter wise included. This obviously means more growth over time.

The turbine blades are designed differently but as to exactly why they don't use the liner, if they in fact don't, I'm not exactly sure. Maybe it has something to do with the 1000+ degree Celsius temps some of the turbines have to deal with.

[Brian Coat]

In RET this month Rob White was asked if MGU-H power is about 90kW: "You are in the ball park and have the right number of zeroes" or words to that effect.

Gnomic as usual but implies < 100 kW?

Probably no shock given you'd only need 120 kW in order to run round at full load with no braking!

[trinidefender]

In RET this month Rob White was asked if MGU-H power is about 90kW: "You are in the ball park and have the right number of zeroes" or words to that effect.

Gnomic as usual but implies < 100 kW?

Probably no shock given you'd only need 120 kW in order to run round at full load with no braking!

Question then. What is the time that is spent at full throttle on the longest track per lap?

If we can get this number then we can work out how much energy that the MGU-H will have to supply if the battery power supply is extended for the whole lap (or at least the time of that lap that full throttle is applied).

[godlameroso]

Spa has 22 seconds of full throttle from La Source to Les Combes, I think that's the longest full throttle stretch.

[trinidefender]

Spa has 22 seconds of full throttle from La Source to Les Combes, I think that's the longest full throttle stretch.

Can you give me a time figure for full throttle for the whole lap?