F1technical.net

@ she
as one who has also questioned the fashion for the buzzword 'heat'
in my steam-age way I reposted yesterday at 2030 on p420 of the Formula One 1.6 thread earlier references to exhaust recovery
particularly the position by Wright that their recovery cost no crankshaft power, this a hot topic in that thread
they sold 14000 such engines
there is also a reference etc to energy balance for these engines

regarding impediment to exhaust flow
to avoid the losses you mention, all piston engines necessarily create other losses in 'blowdown' (choked) from around 7 bar
ie much of use is lost in the exhaust before any recovery turbine
1940s work by the NACA showed (compounded) efficiency highest at high mean exhaust pressure, due to less KE loss in blowdown ?
(also around 5-6 Aug 2013 I posted in the above thread including a link to this (NACA 822) and commented on NACA 1602)

this operation, even into actual backpressure, is relevant to current F1
(of course for most aviation propulsion applications exhaust can be better used in other ways)

F1 mgu-h units are 80 kW or more, most of their output would be used real-time (near-continuous mgu-k motoring), not stored

Tommy Cookers wrote:[....]as one who has also questioned the fashion for the buzzword 'heat'[...]

I'll second your questioning....but it sounds green and therefore sexy

Tommy Cookers wrote:this operation, even into actual backpressure, is relevant to current F1
(of course for most aviation propulsion applications exhaust can be better used in other ways)

In the Porsche LMP1, (and in Scania Truck engines AFAIK), the "compounding" turbine is fitted after a more or less conventional turbocharger. In this location, it will not make use of the exhaust pulses anymore, but has to rely on residual pressure above athmosphere and flow velocity of exhaust. That's also the reason some insulate the exhaust piping before turbine(s), to avoid any cooling and therefore volume loss, which will result in reduced pressure and velocity.

I`ll need some help about MGU-H, MGU-K, principles. Hard to find well explained on the net. Any links – thanks? It`s often mentioned in media that MGU-H converts termal energy of exhaust hot gasses into electrical (and MGU-K braking energy)-How, by means of termocouples, termoionic generator or somehow else? I guess there is also generator braking option for charging batteries both for MGU-K and MGU-H?

Just make a bit of effort and read the whole threads in this forum.

irsq4 wrote: ... It`s often mentioned in media that MGU-H converts termal energy of exhaust hot gasses into electrical (and MGU-K braking energy)-How, by means of termocouples, termoionic generator or somehow else?

the mgu-k only propels the car or produces (for storage) electricity directly from engine power or by braking the car
the mgu-h only produces electricity (for storage or real-time use by the mgu-k) or turns the compressor part of the turbo
there is no heat-to-electricity conversion of the type you suggest
but the turbine part ot the turbo responds to exhaust pressure or velocity, so driving the mgu-h to produce electricity
in 1950s engines of this type the part of the exhaust energy that the turbine can respond to was about 35% of the total exhaust energy

the FIA should have called the mgu-h the mgu-internal energy, and called the mgu-k the mg-external energy
the energy from the mgu-k is not limited to KE recovery (and never was ie with KERS)
most of the energy exhausted from the cylinders can never be recovered via the turbine or similar expander device

given that we drive our road cars at a small % of their maximum power this design has less real-world efficiency benefit
(road driving is mostly accelerator manipulation to degrade engine efficiency and suitably vary the engine to load match)
no better than just buying a smaller conventional engine
(we don't know if detonation will allow enough boost at low speeds (by electrical driving the compressor) to satisfy the driver)

but it will contribute to the transition to electric-only driving in cities and urban areas
at a high cost to the buyer and to the non-buyer through the taxpayer hybrid subsidy

Tommy Cookers wrote:

irsq4 wrote: ... It`s often mentioned in media that MGU-H converts termal energy of exhaust hot gasses into electrical (and MGU-K braking energy)-How, by means of termocouples, termoionic generator or somehow else?

the mgu-k only propels the car or produces (for storage) electricity directly from engine power or by braking the car
the mgu-h only produces electricity (for storage or real-time use by the mgu-k) or turns the compressor part of the turbo
there is no heat-to-electricity conversion of the type you suggest
but the turbine part ot the turbo responds to exhaust pressure or velocity, so driving the mgu-h to produce electricity
in 1950s engines of this type the part of the exhaust energy that the turbine can respond to was about 35% of the total exhaust energy

the FIA should have called the mgu-h the mgu-internal energy, and called the mgu-k the mg-external energy
the energy from the mgu-k is not limited to KE recovery (and never was ie with KERS)
most of the energy exhausted from the cylinders can never be recovered via the turbine or similar expander device

given that we drive our road cars at a small % of their maximum power this design has less real-world efficiency benefit
(road driving is mostly accelerator manipulation to degrade engine efficiency and suitably vary the engine to load match)
no better than just buying a smaller conventional engine
(we don't know if detonation will allow enough boost at low speeds (by electrical driving the compressor) to satisfy the driver)

but it will contribute to the transition to electric-only driving in cities and urban areas
at a high cost to the buyer and to the non-buyer through the taxpayer hybrid subsidy

Thanks, it's termal recovery that confused me actaully. It regenerative braking that happens like on electriclocomotives etc. Electric energy is generated by altering frequency on coils (don't remember exactly anymore,). omega rotor<>omega magntic_field...

Would a native German speaker be willing to translate the following AMuS excerpt regarding -H and backpressure?
"Und dann gibt es da noch ein drittes Leiden, das Renault und offenbar auch Ferrari bremst. Wenn die MGU-H Elektrizität produziert, um sie entweder in der Batterie zu deponieren oder direkt in die MGU-K einzuspeisen, entsteht im Auspufftrakt ein Gegendruck. Der kostet den Motor Leistung, weil sich der Druck gegen die Entleerung der Brennräume stemmt.

"Die Kunst ist es", sagt Mercedes-Motorenchef Andy Cowell mit feinem Lächeln, "entweder die MGU-H so zu konstruieren, dass bei der Stromproduktion so wenig Gegendruck wie möglich erzeugt wird. Oder dass der Motor so gut wie möglich mit diesem Gegendruck leben kann." Mercedes hat das offenbar geschafft. Die Gegner nicht."

From the following article:http://www.auto-motor-und-sport.de/form ... 13488.html

I believe it's saying that while -H is harvesting, it's contributing additional exhaust back pressure. I assume it's saying that due to -H slowing the turbine, waste-energy velocity slows, but don't see how it's adding back pressure per se.

The final paragraph says something interesting about efficient harvesting vs constructing the ICE to account for additional back pressure, but don't understand the inference; how does one construct an MGU-H that minimalizes back pressure, or if taking the latter route, is the article talking about mechanical compensation such as larger/longer exhaust camshaft profiles and the like?

Any help's appreciated; AMuS is a wonderful resource, Google Translate is not.

It's a load on the turbine, so it will add backpressure.
I've alluded to this when people have been considering the mguh as the only thing needed for boost control.

You can look at it this way:

put a pin wheel by your mouth and blow it. Now add an inertial load to it, maybe a bigger one or a heavier one, or just rub you hand against it. Wouldn't you find that the air exiting your mouth is less free to blow out as the intertial load increases?
It's the same thing that happens when you harvest with MGUH. The back emf of the motor is added as a load as the generotor is speed up by the exhaust gases.

supertweet wrote:Would a native German speaker be willing to translate the following AMuS excerpt regarding -H and backpressure?
"Und dann gibt es da noch ein drittes Leiden, das Renault und offenbar auch Ferrari bremst. Wenn die MGU-H Elektrizität produziert, um sie entweder in der Batterie zu deponieren oder direkt in die MGU-K einzuspeisen, entsteht im Auspufftrakt ein Gegendruck. Der kostet den Motor Leistung, weil sich der Druck gegen die Entleerung der Brennräume stemmt.

"Die Kunst ist es", sagt Mercedes-Motorenchef Andy Cowell mit feinem Lächeln, "entweder die MGU-H so zu konstruieren, dass bei der Stromproduktion so wenig Gegendruck wie möglich erzeugt wird. Oder dass der Motor so gut wie möglich mit diesem Gegendruck leben kann." Mercedes hat das offenbar geschafft. Die Gegner nicht."

From the following article:http://www.auto-motor-und-sport.de/form ... 13488.html

I believe it's saying that while -H is harvesting, it's contributing additional exhaust back pressure. I assume it's saying that due to -H slowing the turbine, waste-energy velocity slows, but don't see how it's adding back pressure per se.

extracted energy means a pressure differential across the turbine, the exhaust output is fixed at atmospheric pressure so there has to be higher pressure before the turbine when extracting energy

supertweet wrote: The final paragraph says something interesting about efficient harvesting vs constructing the ICE to account for additional back pressure, but don't understand the inference; how does one construct an MGU-H that minimalizes back pressure, or if taking the latter route, is the article talking about mechanical compensation such as larger/longer exhaust camshaft profiles and the like?

Any help's appreciated; AMuS is a wonderful resource, Google Translate is not.

he just says,

the art is to construct a MGU-H that lowest possible back pressure or construct an engine that as best as possible can live with that back pressure. Mercedes has obviously made it, the competition not

extracted energy does not necessarily mean back pressure

because there is lots of energy in blowdown (the exhaust 'pulses') ie between EVO and BDC
a very useful amount (eg 10-15% to crankshaft power) is extractable without any increase in exhaust pressure after BDC
as stated by Wright, who made 14000 such aircraft engines in the 1950s
so can be called free energy

why is it free energy ??
the turbine work is not seen by the crankshaft as an additional impediment
because blowdown is a choked process, with great loss of useful pressure/velocity energy
choked by the exhaust port, not by whether there is an exhaust turbine or not
the energy extracted by the turbine is simply energy that would otherwise have been dissipated by more supersonic (shock) flow

greater amounts can be extracted if exhaust pressure after BDC is allowed to increase
this again reducing blowdown losses
in the 1940s it was shown that BTE was improved this way (improving total power for a given fuel quantity in 2014 F1)
even if exhaust pressure exceeded induction pressure (as long as the EVC was suitable for this ie relatively early)
this can also be called free energy

these two routes seem in principle complementary (though realisation of this would be design dependent)

Tommy Cookers wrote:extracted energy does not necessarily mean back pressure

because there is lots of energy in blowdown (the exhaust 'pulses') ie between EVO and BDC
a very useful amount (eg 10-15% to crankshaft power) is extractable without any increase in exhaust pressure after BDC
as stated by Wright, who made 14000 such aircraft engines in the 1950s
so can be called free energy

why is it free energy ??
the turbine work is not seen by the crankshaft as an additional impediment
because blowdown is a choked process, with great loss of useful pressure/velocity energy
choked by the exhaust port, not by whether there is an exhaust turbine or not
the energy extracted by the turbine is simply energy that would otherwise have been dissipated by more supersonic (shock) flow

greater amounts can be extracted if exhaust pressure after BDC is allowed to increase
this again reducing blowdown losses
in the 1940s it was shown that BTE was improved this way (improving total power for a given fuel quantity in 2014 F1)
even if exhaust pressure exceeded induction pressure (as long as the EVC was suitable for this ie relatively early)
this can also be called free energy

these two routes seem in principle complementary (though realisation of this would be design dependent)

TC Great explanation!!!

I hope you don't mind if I quote your post in another car forum I go to often?

I'm building a turbo compound system for my personal car and try to describe how back pressure can help with blow down and efficiency? I think I will just copy and paste your post?

Thanks!!!

@pgf pro
ok by me
for this you might find helpful Wright's p9-p13 in the paper linked below

reposting this as had given the wrong page number

Tommy Cookers wrote:@ she
as one who has also questioned the fashion for the buzzword 'heat'
in my steam-age way I reposted yesterday at 2030 on p402 of the Formula One 1.6 thread earlier references to exhaust recovery
particularly the position by Wright that their recovery cost no crankshaft power, this a hot topic in that thread
they sold 14000 such engines
there is also a reference etc to energy balance for these engines

regarding impediment to exhaust flow
to avoid the losses you mention, all piston engines necessarily create other losses in 'blowdown' (choked) from around 7 bar
ie much of use is lost in the exhaust before any recovery turbine
1940s work by the NACA showed (compounded) efficiency highest at high mean exhaust pressure, due to less KE loss in blowdown ?
(also around 5-6 Aug 2013 I posted in the above thread including a link to this (NACA 822) and commented on NACA 1602)

this operation, even into actual backpressure, is relevant to current F1
(of course for most aviation propulsion applications exhaust can be better used in other ways)

F1 mgu-h units are 80 kW or more, most of their output would be used real-time (near-continuous mgu-k motoring), not stored

reminding me that Wright's energy balance values showed ......
that only about 35% of the exhaust heat was in a form (KE) useable by an expander type recovery device (the turbine)
65% being nonuseable sensible heat (only good for cooking etc)
the 2014 CR will be maybe double the Wright's CR
improving ICE efficiency, reduced total exhaust heat but also reduce the % of that reduced total that's useable by the turbine ?

the Wright brochure (thanks to the original poster) shows on its p9 p12 p13 in a way that's priceless to us ......
and states that 'the cylinders are relatively unaware of the existence of the turbines'
http://www.enginehistory.org/Wright/TC%20Facts.pdf
12 of the 18 exhaust pipes are necessarily longer than normal 'stacks', IMO helping to lower exhaust pressure after BDC

IMO large losses in blowdown are unavoidable in any intermittent-combustion (eg piston) engine, even a Mazda rotary
http://www.rotaryeng.net/sum-turbo-comp.html
this from the Wright SAE transactions shows a best BSFC at altitude of 0.325 lb/hp-hr (more recovery at low ambient pressure)
despite Avgas having a significantly lower heat value/lb than good road fuel
another revelation is the large amount of Carbon Monoxide and Methane in the exhaust even with (sea level) lean cruise mixture
(not to mention takoff mixture)
suggesting substantial dissociation (chemical reabsorbtion of combustion heat) due to the high temperatures in-cylinder
a loss of thermodynamic efficiency and of power, presumably unavoidable by Wright

this seems 2014 relevant
though the 2014 high CR/ER would allow re-association in-cylinder due to the greater temperature drop with greater expansion
and there may be a 2014 way to reduce dissociation, possibly in the fuel chemistry
dissociation implies that a CR lower than ideal cannot be well compensated by the resulting increase in available recovery
and apparent gains suggested by (physical) thermodynamics seem to be subverted by the chemical thermodynamics
the right kind of lean-mixture running would also help with dissociation ? but seems unviable with the current fuel quanties

Tommy Cookers wrote:extracted energy does not necessarily mean back pressure

because there is lots of energy in blowdown (the exhaust 'pulses') ie between EVO and BDC
a very useful amount (eg 10-15% to crankshaft power) is extractable without any increase in exhaust pressure after BDC
as stated by Wright, who made 14000 such aircraft engines in the 1950s
so can be called free energy

why is it free energy ??
the turbine work is not seen by the crankshaft as an additional impediment
because blowdown is a choked process, with great loss of useful pressure/velocity energy
choked by the exhaust port, not by whether there is an exhaust turbine or not
the energy extracted by the turbine is simply energy that would otherwise have been dissipated by more supersonic (shock) flow

greater amounts can be extracted if exhaust pressure after BDC is allowed to increase
this again reducing blowdown losses
in the 1940s it was shown that BTE was improved this way (improving total power for a given fuel quantity in 2014 F1)
even if exhaust pressure exceeded induction pressure (as long as the EVC was suitable for this ie relatively early)
this can also be called free energy

these two routes seem in principle complementary (though realisation of this would be design dependent)

It’s my understanding that the Wright compound engine mechanically switched the exhaust flow from the turbine to the open exhaust at BDC to avoid turbine drag during the exhaust stroke.

I'm wondering how that was done

Tommy Cookers wrote:I'm wondering how that was done

Upon further reflection it occurs to me that I may have taken a simile literally, i.e. a blow down turbine is like switching to an open exhaust as opposed to a pressure turbine. Never mind.