TERS : Thermal Energy Recovery System

[gruntguru]

Also On my setup in which I know its not close to what a DI F1 engine is, but my engine cams are design for a high boost turbo charged application, with only 8 degrees over lap.

I do see knock with a poor delta p on pump premium (400whp limit), but not on race fuel VP C16 (650whp limit) but, I do see power fall off from high exhaust pressure before the high pressure turbo starts by passing the exhaust around it to the low pressure turbo. This is my question with the F1 engines loading the turbine for power to feed the MGUH I would expect them to have to keep the intake pressure equal to or more then the exhaust pressure?

I hope that 8 degree overlap is measured at significant lift. Even without knowing what your engine is, 8 degrees measured at zero lift is not enough overlap.

Positive delta P is highly beneficial - particularly on thermally stressed engines. It is/was common practice for turbo diesel engines running in a narrow operating range to have significant overlap to utilise a positive DP to scavenge heat from the combustion chamber surfaces. Gasoline engines gain a further benefit from reduced knock but of course will waste fuel if a timed injection is not available.

[Tommy Cookers]

pgf pro's findings with -dP seem about the same as NACA's
anyway the cutoff value of -dP surely varies with eg rpm/gas velocity and tuned exhaust extractor effect (as well as EVC timing)

-dP makes more sense if the engine was NA or low boosted
so there seems less potential for -dP (or little need for it) in F1

F1 would use about 2.2 bar abs boost with near-stoi mixture and higher boost with lean mixture (more air)
so their exhaust pressure is high even at conventional +dPs

but current boosts around 3 bar abs do not prove that lean mixtures are being used

RETRO-EDIT (with apologies)
3 bar abs corresponds to a not-very-lean (or even near-stoi) mixture only if VE is depressed
(a high turbine loading via gu-h power setting gives a -dP but won't depress VE - thanks to gg for this correction)

but an (inlet) valve necessarily undersized to allow high CR and a compact combustion chamber (forecast by Gilles Simon) would

there is little downside to this lower VE and and overall it's beneficial due to the greater manifold and exhaust pressures

we know that the blowdown power recovery is higher than recovery of 'Brayton cycle power'
and about 11% of the 720 deg is blowdown, so 11% of Brayton power recovery could be credited to blowdown

high exhaust pressures are being used (for any AFR and boost/dP)
this gives high exhaust density so the load against the blowdown expansion is high
this will better conserve the pressure/velocity energy and so increase blowdown recovery

and (comparing the Wright with F1) the CR is in F1 much higher
so exhaust energy is much less, but proportion useful to blowdown is higher (sensible heat/mean pressure is not useful to blowdown)
and imo around 2 bar gauge (as F1) Wright could in principle develop about 27% recovery (everything maxed at high altitude)

F1's boost limit rule will only allow a low PR and so constrains 'Brayton power' at race-practical turbine and compressor efficiencies
that was their intent - they didn't want a hyperbar or a turbine-dominated compound engine

[pgfpro]

Also On my setup in which I know its not close to what a DI F1 engine is, but my engine cams are design for a high boost turbo charged application, with only 8 degrees over lap.

I do see knock with a poor delta p on pump premium (400whp limit), but not on race fuel VP C16 (650whp limit) but, I do see power fall off from high exhaust pressure before the high pressure turbo starts by passing the exhaust around it to the low pressure turbo. This is my question with the F1 engines loading the turbine for power to feed the MGUH I would expect them to have to keep the intake pressure equal to or more then the exhaust pressure?

I hope that 8 degree overlap is measured at significant lift. Even without knowing what your engine is, 8 degrees measured at zero lift is not enough overlap.

Positive delta P is highly beneficial - particularly on thermally stressed engines. It is/was common practice for turbo diesel engines running in a narrow operating range to have significant overlap to utilise a positive DP to scavenge heat from the combustion chamber surfaces. Gasoline engines gain a further benefit from reduced knock but of course will waste fuel if a timed injection is not available.

The OL numbers are based on 0.0394" or 1mm how ever you measure your soup off the seat.

[gruntguru]

Phew!!

[gruntguru]

. . . . but current boosts around 3 bar abs do not prove that lean mixtures are being used
eg they could be using a near-stoi mixture with a relatively high turbine loading from the gu-h power setting

3 Bar abs with moderate intercooling and normal VE (>100%) yeilds an intake mass flow which can only produce a lean mixture. Doesn't matter much what the turbine is doing - except to say high exhaust loading = higher EBP = lower scavenge mass flow = higher trapped mass = leaner mixture.

[wuzak]

F1's boost limit rule will only allow a low PR and so constrains 'Brayton power' at race-practical turbine and compressor efficiencies
that was their intent
they didn't want a hyperbar or a turbine-dominated compound engine

There isn't a boost limit rule in the current regulations.

[Tommy Cookers]

. . . . but current boosts around 3 bar abs do not prove that lean mixtures are being used
eg they could be using a near-stoi mixture with a relatively high turbine loading from the gu-h power setting

3 Bar abs with moderate intercooling and normal VE (>100%) yeilds an intake mass flow which can only produce a lean mixture. Doesn't matter much what the turbine is doing - except to say high exhaust loading = higher EBP = lower scavenge mass flow = higher trapped mass = leaner mixture.

Yes gg, I was wrong in this matter (and should have remembered it from a previous occasion)
ie even at a maximum conceivable -dP the mixture would need to be substantially lean for a boost of 3 bar

I was thinking about the benefit of raised exhaust pressure to blowdown power recovery
imo the higher density better conserving pressure/kinetic energy
conceptually a factor seperate from the effects om 'Brayton recovery' of greater PR/boost linked to leaner mixture
your figures show that 'Brayton recovery' is vulnerable at the higher PRs/higher leaning to eg compressor efficiency

presumably blowdown recovery is less vulnerable and rather unrelated to PR
raising PR might imply a need for earlier exhaust valve opening and some loss of crankshaft power

the Wright TC recovery at takeoff was 18%, apparently without cost to crankshaft power
the valve timing was the same as in the non-compound version of this engine

[Abarth]

At the end, this whole engineering exercise has been said to be beneficial for road cars.
And to put this into perspective, we need to look at mainly part load engine usage.

What I therefore really would like to see is how the blowdown recovery looks like at part loads.
Eg. to get a feeling about how much could be harvested in a production car when driving 130kph on a highway, without having too complicated arrangements of parallel turbines of different sizes and whatnot.

[Tommy Cookers]

I have often said that this so-called TERS will give about 10-20% 'free' power (as the NACA showed nearly 70 years ago)
and so can reasonably be regarded as increasing maximum engine efficiency by that 10-20%
ie we can get 10-20% more power at that same rate of fuel consumption

however,typically this does not lend itself to reduced fuel consumption (eg of road cars)
at partial torque/power the 'free' torque/power will be cancelled by increased throttling to contain output to that partial torque
this is how we drive the public highway
true, this effect would be slighty offset if the gearing were raised by the 3-4% permitted by the 10-20% output gain
(this situation is a parallel to the somewhat futile raising of CR/fuel Octane for road cars)
greater offset is of course available if the car has a large but conveniently empty store for energy recovery
though this is anyway not particularly efficient (compared with direct use of exhaust-recovered electrical energy)

to get the proper economy benefit from TERS we need to further downsize the engine correspondingly about 10-20%
(this beyond the already envisaged level of downsizing-by-turbocharging)
ie we should design our (electrically) turbo-compounded engine to the same power as the uncompounded engine we are replacing

though old-school downsizing by customer (buying only twice the engine power needed not five times) works with any engine type
as does the the elimination of throttling inefficiency by other means ie radical redesign of engine or transmission

one aim of the 2014 activity is to facilitate hybridisation by stealth and covert European (and Japanese ?) protectionism
this involves buying complicated and expensive cars
the 3 European parents of these F1 engines are all supported to some extent by 'public-interest' oriented investment

once, in 1991, the French govt campaigned (unsuccessfully of course) for EU policy to encourage the small-engined, simple cars
at one time also the Japanese govt encouraged these

fwiw - bumped from late 2013
since then the downsized road engine with a part-time electrically-driven radial flow/centrifugal compressor has been hinted at
benefits of F1 TERS technology in road cars depend rather on greater downsizing allowed by simultaneous ICE and electric motoring
and it will help towards all-electric city driving

[pgfpro]

At the end, this whole engineering exercise has been said to be beneficial for road cars.
And to put this into perspective, we need to look at mainly part load engine usage.

What I therefore really would like to see is how the blowdown recovery looks like at part loads.
Eg. to get a feeling about how much could be harvested in a production car when driving 130kph on a highway, without having too complicated arrangements of parallel turbines of different sizes and whatnot.

I think we could see some road car benefits from this new F1technology? From what I have learned from my own lean burn turbo compound car is that blow-down can help with light load freeway driving. On my car I'm running around 30:1 to 35:1 A/F ratios and have seen a major improvement from lean burn and its affects of zero loss intake pumping losses. I run at around -1 inch/hg to 1.5 psi at freeway speed. On my compound turbo system my high pressure turbo is the smaller of the two turbo's and because of its small turbine being more restrictive back pressure is higher then my earlier version large single turbo lean burn system. From my data logs I'm seeing around +1 to -1 engine delta p. My new goal is to install my very small muffler only 1.5" dia. compared to my 3" exhaust and run my boost activated 3" exhaust cut out when power is needed. This should increase back pressure and get me around -3 engine delta p. at light load freeway speed.

Now you could build a NA engine and just run a turbine to help with blow down recovery and produce energy from a MGUH system, but you would lose a lot of power from a down sized NA engine. Not good for when you need passing power or getting on the freeway power, or if your like racing power.

With all this said I do understand that lean burn engines on road cars would have to some type of new cat technology to deal with Nox. So that might not happen, but I think the manufacturers could down size the engines enough and run some lean burn with advance cold air egr systems to make this work???

The other thing that comes to mind is how much power at light load freeway speed will the MGUH be able to produce??? From my calculations not much. Enough to help with the battery charging system, and maybe that's enough with all the extra sub systems that use electricity today power steering etc.

Here is a flow chart my system on my car.

Turbo over lay.

[Tommy Cookers]

impressive stuff, can you remind us what you do to for successfull combustion at AFRs of 30-35 ?

[Tommy Cookers]

If MAP = BP the turbo machinery is a simple Brayton cycle - the combustor being replaced by the piston engine as its heat source ......

In the F1 case, the heat input to this Brayton cycle (Gas Turbine) is relatively fixed wrt PR. The surplus work (Wt - Wc) however, is dependent on PR. The theory behind this is well established ......
So interestingly, at 80% isentropic efficiency for the turbine and compressor, changing the PR has little effect on surplus energy to the MGUH. At lower efficiencies lower PR will be favoured and at higher efficiencies, higher PR will produce more surplus energy.

IMO
surely the turbo machinery (if MAP = BP) is running on a combination of 'Brayton power' as above and on blowdown power ?

the values in your examples use the PR after blowdown ie the mean ('default') exhaust pressure
they are ignoring the higher PR acting during blowdown
notionally MAP = BP (default exhaust pressure) for 3 strokes but MAP < mean exhaust pressure in 1 stroke (the power/blowdown)

this because the 6 blowdown pulses are substantially seperate and so preserved into the turbine
(not merged, this would eliminate blowdown power but raise mean exhaust pressure and so raise Brayton power)

[gruntguru]

If MAP = BP the turbo machinery is a simple Brayton cycle - the combustor being replaced by the piston engine as its heat source ......

In the F1 case, the heat input to this Brayton cycle (Gas Turbine) is relatively fixed wrt PR. The surplus work (Wt - Wc) however, is dependent on PR. The theory behind this is well established ......
So interestingly, at 80% isentropic efficiency for the turbine and compressor, changing the PR has little effect on surplus energy to the MGUH. At lower efficiencies lower PR will be favoured and at higher efficiencies, higher PR will produce more surplus energy.

IMO
surely the turbo machinery (if MAP = BP) is running on a combination of 'Brayton power' as above and on blowdown power ?

the values in your examples use the PR after blowdown ie the mean ('default') exhaust pressure
they are ignoring the higher PR acting during blowdown
notionally MAP = BP (default exhaust pressure) for 3 strokes but MAP < mean exhaust pressure in 1 stroke (the power/blowdown)

this because the 6 blowdown pulses are substantially seperate and so preserved into the turbine
(not merged, this would eliminate blowdown power but raise mean exhaust pressure and so raise Brayton power)

All the Brayton cycle calcs I presented earlier would assume BP = average exhaust pressure ie the pressure obtained if the cylinders discharged into a common plenum. An individual runner from cylinder to turbine would display this same average pressure but the blowdown pulses would be significantly higher and some other periods would be significantly lower (with proper wave tuning the lowest pressure at the valve would occur somewhere late in the exhaust stroke). So the Brayton analysis serves to illustrate how much surplus energy might be available in the absence of any blowdown energy recovery. Harnessing blowdown energy achieves: Substantially increases the turbine energy at a given BP.
Optimal wave tuning additionally allows: A higher BP (avg) without loss of scavenge benefits. The higher BP would easily amount to a negative DP as measured from average inlet and exhaust pressures.

Perhaps the main benefit of the newly permitted variable intake systems (optimising intake wave function over a wide operating range) is increased scavenge - allowing a higher EBP and higher MGUH recovery without the need to increase boost (at a cost of compressor energy and possibly compromising AFR).

[Tommy Cookers]

this seems consistent with the NACA findings and statement (that all engines were fine at -10" dP and many fine at -20" dP)

Wright describe their use of 'wave tuned' exhaust lengths to an extent anyway unavoidable in compounding 18 cylinders
('the other' 99.5% of aircraft engines chose to avoid such for good practical reasons)

while scavenge has a lot to do with the timing of exhaust valve closure
the timing of exhaust valve opening is hugely important to crankshaft power and power recovery (and to their relationship)
we might imagine that Wright worked on this for their operation at 1.15 - 2.25 bar abs MAP and big AFR range
we might imagine that in road cars EVO is a compromise between the needs of throttled and unthrottled operation
(unthrottled our cars start blowdown from a pressure of around 11 bar, that's why there's is so much potential for recovery)

regarding variable geometry inlet systems (effectively free, and more applicable to the less advanced of the F1engines ?) ....
we might also imagine that variable geometry exhaust systems would be ideal
and VVT seems compellingly attractive eg by manipulating EVO

but F1s engine by its built-in ability to manipulate MAP and BP by manipulating the mguh rpm is doing a good job
and it can move power from crankshaft to compound recovery at will, this largely covers the case for varying the EVO
what's not to like ? - Mercedes and Ferrari are surely have their 120 kw 'anytime' F1 already, and it's a road-plausible concept

recovery from sensible heat in coolant and exhaust the BeemerSteamer way gives better PU efficiency at road's partial powers ?
but the 100000rpm mgu-h now beats the BS on cost (given that a multi kW motor-generator is now needed for hybrid capability)
and has equal claim on the headline 'best efficiency'' (ie higher power)

[pgfpro]

impressive stuff, can you remind us what you do to for successfull combustion at AFRs of 30-35 ?

Thanks TC.
Here are some specs.
Engine:
2.0L 4G63 dual over head cams, 16 valve

modified 1g turbo pistons, spray-guided crown, with fuel capture port
this works in conjunction with my modified combustion chamber to produce a pre-chamber for stratified charge

modified head, spray-guided high heat air direct port, single valve open only to produce mass swirl during fuel mileage mode

custom camshafts

intake manifold, high heat air direct port w/adjustable port angle injection

high low pressure turbo compound system, to produce higher back pressure at freeway speed, waste gates open to divert 60% of the exhaust to the low pressure turbo at WOT for performance 600+whp

Full write up at
http://ecomodder.com/forum/showthread.p ... 28776.html
Thanks for the interest.