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subcritical71 wrote: ↑

30 Oct 2018, 16:36

Good points hurril. I still struggle (for myself) in this case of the nene 10. I could go either way honestly. And if it would be considered a single stage could you then modify one half of the 'stage' so that the pumping characteristics can be shifted slightly to give a better overall operation of the turbo? That would be really interesting.

The Nene had a single stage compressor with double sided impeller.

The Rolls-Royce R also had a single stage compressor with double sided impeller, as did the early Sabre versions.

The trick with the F1 regulations is that not only do they ban 2 stage supercharging, they also limit the turbo to one turbine wheel and one compressor wheel.

For mine, the double sided compressor would be OK so long as the impeller was one piece. If you had two pieces mounted back to back its legality would be questionable.

The double sided compressor may become more attractive if the 2021 rules move ahead with the elimination of the MGUH. For while the current rules favour large compressors (I am guessing they are more efficient), the lower inertia of a smaller, double sided, impeller would improve spool up/reduce lag.

A double sided impeller, which consists of two impellers arranged in back-to-back configuration with the back-disks eliminated, enables a single centrifugal compressor to have flow capacity similar to two compressors working in ‘parallel’ but with smaller packaging size. Inertia of rotating group is reduced and transient response is improved. The question is, will a one piece double sided impeller still classify as a ‘one single impeller by the rule makers?.

saviour stivala wrote: ↑

01 Nov 2018, 07:03

A double sided impeller, which consists of two impellers arranged in back-to-back configuration with the back-disks eliminated, enables a single centrifugal compressor to have flow capacity similar to two compressors working in ‘parallel’ but with smaller packaging size. Inertia of rotating group is reduced and transient response is improved. The question is, will a one piece double sided impeller still classify as a ‘one single impeller by the rule makers?.

Good question! But don't you think that such an arrangement would have to be of a lower efficiency? Otherwise: why not do it now? Supporting the compressor work with electrical energy isn't a free lunch so if there is a way to reduce inertia _and_ that that is good, then they would already be doing it. High inertia also implies more energy to "brake off" by the MGU-h.

wuzak wrote: ↑

01 Nov 2018, 01:44

The double sided compressor may become more attractive if the 2021 rules move ahead with the elimination of the MGUH. For while the current rules favour large compressors (I am guessing they are more efficient), the lower inertia of a smaller, double sided, impeller would improve spool up/reduce lag.

I would expect it not to change. There is still torque fill with the MGUK as the compressor spools much like the NSX.

I do wonder how much combustion processes and valve timing will change since the power demand by the turbine should drop with no H.

hurril wrote: ↑

01 Nov 2018, 11:51

saviour stivala wrote: ↑

01 Nov 2018, 07:03

A double sided impeller, which consists of two impellers arranged in back-to-back configuration with the back-disks eliminated, enables a single centrifugal compressor to have flow capacity similar to two compressors working in ‘parallel’ but with smaller packaging size. Inertia of rotating group is reduced and transient response is improved. The question is, will a one piece double sided impeller still classify as a ‘one single impeller by the rule makers?.

Good question! But don't you think that such an arrangement would have to be of a lower efficiency? Otherwise: why not do it now? Supporting the compressor work with electrical energy isn't a free lunch so if there is a way to reduce inertia _and_ that that is good, then they would already be doing it. High inertia also implies more energy to "brake off" by the MGU-h.

Why would such an arrangement be of lower efficiency?.
Who can tell what they are really using inside there now?.

saviour stivala wrote: ↑

01 Nov 2018, 20:02

hurril wrote: ↑

01 Nov 2018, 11:51

saviour stivala wrote: ↑

01 Nov 2018, 07:03

A double sided impeller, which consists of two impellers arranged in back-to-back configuration with the back-disks eliminated, enables a single centrifugal compressor to have flow capacity similar to two compressors working in ‘parallel’ but with smaller packaging size. Inertia of rotating group is reduced and transient response is improved. The question is, will a one piece double sided impeller still classify as a ‘one single impeller by the rule makers?.

Good question! But don't you think that such an arrangement would have to be of a lower efficiency? Otherwise: why not do it now? Supporting the compressor work with electrical energy isn't a free lunch so if there is a way to reduce inertia _and_ that that is good, then they would already be doing it. High inertia also implies more energy to "brake off" by the MGU-h.

Why would such an arrangement be of lower efficiency?.
Who can tell what they are really using inside there now?.

Right. But the question was whether or not removing the MGU-h would cause anyone to change some aspect of the turbo or not. If you want to lighten the impeller in an effort to reduce the inertia because inertia is bad, then surely it would be bad with an MGU-h too? Energy isn't free to be wasted in either situation. Plus: a turbo-MGU-h-system is bound to have a huge inertia anyway so a case could actually be made for using a lighter impeller _with_ an MGU-h.

Whenever there is a change of characteristics of the engine towards better combustion, there is the need to adjust the turbocharger and MGU-H, and this means new turbine blades and compaction blades for better recuperation and that is a lot of very expensive work of coordination and simulations on very expensive to run special test stands.

saviour stivala wrote: ↑

01 Nov 2018, 20:02

hurril wrote: ↑

01 Nov 2018, 11:51

Good question! But don't you think that such an arrangement would have to be of a lower efficiency? Otherwise: why not do it now? Supporting the compressor work with electrical energy isn't a free lunch so if there is a way to reduce inertia _and_ that that is good, then they would already be doing it. High inertia also implies more energy to "brake off" by the MGU-h.

Why would such an arrangement be of lower efficiency?

Efficiency of turbomachinery increases with size for a number of reasons. Leakage paths (clearances) become relatively less problematic, surface area to volume ratio increases (skin friction increases) etc. If you look at a number of turbo compressor maps you will find that the efficiency trends upwards with flow capacity.

gruntguru wrote: ↑

02 Nov 2018, 00:09

saviour stivala wrote: ↑

01 Nov 2018, 20:02

hurril wrote: ↑

01 Nov 2018, 11:51

Good question! But don't you think that such an arrangement would have to be of a lower efficiency? Otherwise: why not do it now? Supporting the compressor work with electrical energy isn't a free lunch so if there is a way to reduce inertia _and_ that that is good, then they would already be doing it. High inertia also implies more energy to "brake off" by the MGU-h.

Why would such an arrangement be of lower efficiency?

Efficiency of turbomachinery increases with size for a number of reasons. Leakage paths (clearances) become relatively less problematic, surface area to volume ratio increases (skin friction increases) etc. If you look at a number of turbo compressor maps you will find that the efficiency trends upwards with flow capacity.

Fully agree, not contesting that. "Thermodynamics:-Large flow systems are more efficient than smaller flow systems", But this is different to the previous argument of the advantage of a double sided impeller single centrifugal compressor flow capacity being similar to two compressors working in parallel.

saviour stivala wrote: ↑

02 Nov 2018, 08:47

gruntguru wrote: ↑

02 Nov 2018, 00:09

saviour stivala wrote: ↑

01 Nov 2018, 20:02

Why would such an arrangement be of lower efficiency?

Efficiency of turbomachinery increases with size for a number of reasons. Leakage paths (clearances) become relatively less problematic, surface area to volume ratio increases (skin friction increases) etc. If you look at a number of turbo compressor maps you will find that the efficiency trends upwards with flow capacity.

Fully agree, not contesting that. "Thermodynamics:-Large flow systems are more efficient than smaller flow systems", But this is different to the previous argument of the advantage of a double sided impeller single centrifugal compressor flow capacity being similar to two compressors working in parallel.

What would the drawback be with using such a double-sided impeller in an MGU-h-system?

What would be the pro/con and practicality of using a constant speed with the surplus bled off, possibly to cooling?
A heavier unit could be used as it would not have rapid acceleration/deceleration. I know it would be a no go with an exhaust only unit, but if it was topped up with battery power would it still cost to much in energy terms to cover lag?

Big Tea wrote: ↑

02 Nov 2018, 12:58

What would be the pro/con and practicality of using a constant speed with the surplus bled off, possibly to cooling?

the con would be disqualification. Air entering the compressor must exit via the exhaust.

henry wrote: ↑

02 Nov 2018, 15:17

Big Tea wrote: ↑

02 Nov 2018, 12:58

What would be the pro/con and practicality of using a constant speed with the surplus bled off, possibly to cooling?

the con would be disqualification. Air entering the compressor must exit via the exhaust.

Ah, right. Filed under crap then.

Big Tea wrote: ↑

02 Nov 2018, 15:22

henry wrote: ↑

02 Nov 2018, 15:17

Big Tea wrote: ↑

02 Nov 2018, 12:58

What would be the pro/con and practicality of using a constant speed with the surplus bled off, possibly to cooling?

the con would be disqualification. Air entering the compressor must exit via the exhaust.

Ah, right. Filed under crap then.

Could it not be 'bled off' into the engine exhaust, essentially bypassing the ICE, and subsequently exiting from the engine exhaust?

subcritical71 wrote: ↑

02 Nov 2018, 15:33

Big Tea wrote: ↑

02 Nov 2018, 15:22

henry wrote: ↑

02 Nov 2018, 15:17

the con would be disqualification. Air entering the compressor must exit via the exhaust.

Ah, right. Filed under crap then.

Could it not be 'bled off' into the engine exhaust, essentially bypassing the ICE, and subsequently exiting from the engine exhaust?

I was trying to think of where it could be used beneficially, such as cooling, but it could run a generator and be ducted back in I suppose?

I am full of useless ideas though