26 replies to this topic

[Wuzak]

I'm trying to find out about the performance of the turbo and its role in exhaust energy recovery through the MGUH/ERS-H.

I have seen some estimates of power recovered between negligible and 100kW.

This report suggests a recovered power of around 7% of nominal crankshaft power would be achievable. They are basing there estimate on a 4 cylinder, 10,000rpm engine with turbocharger and separate power recovery turbine feeding back to the crankshaft through a set of gears.

Given that the estimates for the 2014 V6s are around 600-650hp, that would imply a maximum of between 42 and 45.5hp revovered by the ERS-H.

Some questions:
How much boost at 10,500rpm, the point at which maximum fuel flow is reached.
How much boost at 15,000rpm?
How much power to drive the compressor at these speeds/boost levels?
How much turbine power could be generated?

And, thus, how much power is available to the ERS-H?

In another discussion some people suggest that the 2014 turbos will make use of wastegates. I can't see the point myself. Anybody think they will use wastegates at all on these engines/

[jimjimjeroo]

I know nothing of the subject only to say, wouldn't the gear changes be too quick to employ any such waste gate? As far as I am aware, they only operate whilst the throttle is closed or lifted....?

[MatsNorway]

I would run a wastegate. If something fails and it will if you design it on the limit as you should in this development times.

[Wuzak]

I would run a wastegate. If something fails and it will if you design it on the limit as you should in this development times.

So, a wastegate as a backup, not primary turbo control?

[gruntguru]

Can't see much point in a wastegate. The MGU controls turbo speed. If it failed you could retire the car or perhaps control turbo speed with the engine map.

NA these engines would make a little less per litre than the current engines retuned for 10,500. So 700hp x 10,500 / 17,000 x 1.4/2.4 = 250hp

Required Boost = 650hp/250hp = 2.6 bar abs or 1.6 bar guage (23 psi)
At 15,000 rpm, required boost = 2.6 x 10,500/15,000 = 1.8 bar abs or 0.8 bar guage (12 psi)

These are absolute minimums. The engine would be optimised for 10,500 so required boost at 15k would be a fair bit higher. All boost levels would be also higher due to the engine being tuned for efficiency over power.

[RogerGraham]

Is it generally true that an engine will be most efficient running at the lowest revs where max fuel flow rate is achieved/allowed, i.e. 10,500rpm in this case, from lower friction losses and so on (assuming all else is "equal", e.g. that you can get enough air into the cylinders)?

[JimboJones]

Is it generally true that an engine will be most efficient running at the lowest revs where max fuel flow rate is achieved/allowed, i.e. 10,500rpm in this case, from lower friction losses and so on (assuming all else is "equal", e.g. that you can get enough air into the cylinders)?

Correct. This is why it's unlikely they will rev beyond 12500, as power will drop off too much due to friction.

As for boost level, you can actually work this out. Consider the 100kg/hr fuel flow limit, assume a value for lambda (say 1?), this gives a rough air flow rate. Then from the engine capacity and rpm you can estimate the compression required to squeeze all that air in. I think you'll find it's way higher than 2bar...

Whether teams run wastegates will be interesting. In qualifying, you won't need to recover energy like in a race as you can start on a full battery, so perhaps opening a wastegate could give even more power, as you're not choking the exhaust flow to harvest energy?

[Wuzak]

Whether teams run wastegates will be interesting. In qualifying, you won't need to recover energy like in a race as you can start on a full battery, so perhaps opening a wastegate could give even more power, as you're not choking the exhaust flow to harvest energy?

If you recover energy frm teh MGUH the energy stored in the battery can last longer.

[MatsNorway]

So, a wastegate as a backup

yes.

[bigleagueslider]

The wastegate on a conventional turbocharger system serves to limit the level of pressure produced within the intake manifold by diverting part of the exhaust energy directed to the turbine wheel, which in turn drives the intake compressor. A conventional turbocharger requires an energy balance between the compressor and turbine work. An electric M/G ERS connected to the turbo spool would be effective at adding/extracting energy to/from the turbo to maintain the desired levels of intake and exhaust manifold pressures. Thus a mechanical wastegate system would seem to be unnecessary.

An internal combustion engine will always achieve best thermal efficiency at operating conditions that result in the highest net positive between output and losses. This will normally be at operating conditions of low RPM, high BMEP, and WOT. The actual total fuel mass flow rate may be irrelevant under some operating conditions, since fuel mass flow would be dependent upon air mass flow at any given time.

The turbo M/G ERS can also recover braking energy by applying engine back-pressure loads at the exhaust turbine using the generator.

[Lightknight]

that would imply a maximum of between 42 and 45.5hp revovered by the ERS-H.

Some questions:
How much boost at 10,500rpm, the point at which maximum fuel flow is reached.
How much boost at 15,000rpm?
How much power to drive the compressor at these speeds/boost levels?
How much turbine power could be generated?

And, thus, how much power is available to the ERS-H?

In another discussion some people suggest that the 2014 turbos will make use of wastegates. I can't see the point myself. Anybody think they will use wastegates at all on these engines/

The boost at 10,500 will be pretty much the same- 2.5 bar 6000 or 12,000. It must be remembered that the MGU-h drives the turbine, not the reverse off throttle, so that max boost is available at all times. Obviously the amount of power to do this is drawn from the ERS. how much? 10 BHP - maybe more.

The main point to remember with the new unit the total allowed stored energy is 4Mj - about 160 BHP for 33.3 seconds. However, only 2Mj may be stored per lap, but 4Mj may be RELEASED on a lap. Because of the huge amount of torque available, this power needs to be carefully managed and doing this would be a full time job for the driver - so there is some computer control here - from 2014 we will see a new on-screen graphic showing how the ERS is being used and charged etc..

So from this we can see that 80BHP is being collected and stored per lap. I don't know the ratio between Kinetic and Heat but it would not surprise me if less than 50 BHP for 15 seconds is available- taking an allowance for the Electro - turbo boost. This motor will absorb quite a lot of power at times because the teams will have the turbo fully powered up off throttle for more engine breaking - maybe 10-12 seconds a lap . of course the potential for Kinetic recovery is always going to be higher but its problematic because it upsets breaking balance. Certainly the potential for Heat energy recovery is very high but that is very dependent on FIA regulations. The current max boost is 2.5 BAR and max rpm is 125,000. There is no wastegate because none is needed - indeed the whole idea is anathema -its a closed loop system, where excess power generated by the turbo is converted to electricity and effectively the turbo RPM is equally electrically governed to a max of 125,000 RPM and/or 2.5 BAR. Its a great system but clearly a bigger turbo, more RPM and more boost could recover more energy.

I have heard that the Mercedes power unit is producing 600 NM of Torque at 'some' RPM and a maximum output in excess of 810 BHP. This compares to 320 N for the V8 and max BHP of about 750 BHP. In other words by 2015 these units will produce well over 850 BHP - well and truly eclipsing the V8 - and with only 65% of the fuel too.

[Lightknight]

I know nothing of the subject only to say, wouldn't the gear changes be too quick to employ any such waste gate? As far as I am aware, they only operate whilst the throttle is closed or lifted....?

No wastegate at all. Full boost of 2.5 bar is available virtually 100% of the time. Excess boost is managed by increasing the energy generation fro the Turbo. Low boost is prevented by the generator reversing its role as an electric motor to drive the turbine to whatever boost is required.

[Lightknight]

So, a wastegate as a backup, not primary turbo control?

No wastegate. See my other posts here.

[Lightknight]

Can't see much point in a wastegate. The MGU controls turbo speed. If it failed you could retire the car or perhaps control turbo speed with the engine map.

NA these engines would make a little less per litre than the current engines retuned for 10,500. So 700hp x 10,500 / 17,000 x 1.4/2.4 = 250hp

Required Boost = 650hp/250hp = 2.6 bar abs or 1.6 bar guage (23 psi)
At 15,000 rpm, required boost = 2.6 x 10,500/15,000 = 1.8 bar abs or 0.8 bar guage (12 psi)

These are absolute minimums. The engine would be optimised for 10,500 so required boost at 15k would be a fair bit higher. All boost levels would be also higher due to the engine being tuned for efficiency over power.

2.5 Bar above atmospheric. The units produce, currently including ERS power, 810 BHP and 600 NM - and this is expected to rise to 850-860 in 2015. Its highly unlikely that they will rev over 12,500 given the current fuel flow limit. Don't forget that "tuning for efficiency" may not occur because of packaging considerations. The location of the Turbo and MGU-H in the Vee is a bit of an issue so a stoichiometric 12-13 is more likely to be used to reduce engine temperatures. Economy modes are likely to be quite complex I would suggest given the role of the ERS.

[Lightknight]

Is it generally true that an engine will be most efficient running at the lowest revs where max fuel flow rate is achieved/allowed, i.e. 10,500rpm in this case, from lower friction losses and so on (assuming all else is "equal", e.g. that you can get enough air into the cylinders)?

At a guess yes but what you need to know is the BMEP and BSpFC - not surprisingly no one is releasing this info. Frictional loses are always higher the more revs you have and are not straight line.

[Lightknight]

Correct. This is why it's unlikely they will rev beyond 12500, as power will drop off too much due to friction.

As for boost level, you can actually work this out. Consider the 100kg/hr fuel flow limit, assume a value for lambda (say 1?), this gives a rough air flow rate. Then from the engine capacity and rpm you can estimate the compression required to squeeze all that air in. I think you'll find it's way higher than 2bar...

Whether teams run wastegates will be interesting. In qualifying, you won't need to recover energy like in a race as you can start on a full battery, so perhaps opening a wastegate could give even more power, as you're not choking the exhaust flow to harvest energy?

They won't run wastegates because the MGU-H manages all that. The boost level is 2.5 Bar above atmo. Don't forget that they will need to charge the ERS for qualifying and they can charge up to the maximum of 4Mj and release all of this on one qualifying lap but they may want to run another qually lap after 2 cooling down laps - in which case they would want the ability for both the GGU K and H to function as normal so that they can start with a full ERS..

Opening a wastegate for more power? As I said it doesnt apply. I believe the Turbo will run at a more or less constant 2.5 bar or as required for best performance. Note that when off-throttle the Turbo is fully powered up by the MGU-H for a) instant throttle response and b) better engine braking performance.

[Lightknight]

The wastegate on a conventional turbocharger system serves to limit the level of pressure produced within the intake manifold by diverting part of the exhaust energy directed to the turbine wheel, which in turn drives the intake compressor. A conventional turbocharger requires an energy balance between the compressor and turbine work. An electric M/G ERS connected to the turbo spool would be effective at adding/extracting energy to/from the turbo to maintain the desired levels of intake and exhaust manifold pressures. Thus a mechanical wastegate system would seem to be unnecessary.

An internal combustion engine will always achieve best thermal efficiency at operating conditions that result in the highest net positive between output and losses. This will normally be at operating conditions of low RPM, high BMEP, and WOT. The actual total fuel mass flow rate may be irrelevant under some operating conditions, since fuel mass flow would be dependent upon air mass flow at any given time.

The turbo M/G ERS can also recover braking energy by applying engine back-pressure loads at the exhaust turbine using the generator.

Yes good response. Glad to see some people have got their heads around this! How people think a wastegate is required is strange - very 1980's in fact.

[RogerGraham]

It must be remembered that the MGU-h drives the turbine, not the reverse off throttle, so that max boost is available at all times. Obviously the amount of power to do this is drawn from the ERS. how much? 10 BHP - maybe more.

No wastegate at all. Full boost of 2.5 bar is available virtually 100% of the time. Excess boost is managed by increasing the energy generation fro the Turbo. Low boost is prevented by the generator reversing its role as an electric motor to drive the turbine to whatever boost is required.

Lightknight, I hope this isn't a dumb question, but I'm going to try paraphrasing your comments to see if I understand. Are you saying that:

1. the turbine is driven by the exhaust gases and by the MGU-h, i.e. the MGU-h adds whatever power is needed to keep the turbine/compressor RPMs such that boost is always at 2.5bar above atmospheric (or at least, whenever required)?

2. the MGU-h can take electrical power from the turbine, which obviates the need for a wastegate?


I'm assuming the turbine and compressor are still directly connected by a shaft. If so:

3. is there any potential efficiency/packaging/heat/other benefit in completely separating the turbine/MGU-h and compressor, with the compressor driven by its own electric motor? If so, are such arrangements disallowed by the apparently-quite-proscriptive rules?

[Wuzak]

1. the turbine is driven by the exhaust gases and by the MGU-h, i.e. the MGU-h adds whatever power is needed to keep the turbine/compressor RPMs such that boost is always at 2.5bar above atmospheric (or at least, whenever required)?

The MGUH can be used as a motor and a generator. It will be used to spool the turbo for better response, eliminating turbo lag.

There is no limit to boost.

2. the MGU-h can take electrical power from the turbine, which obviates the need for a wastegate?

The MGUH will generate power when the turbine has more power than is required to drive the compressor. At other times the compressor and turbine powers will be balanced, so the MGUH can be isolated from the turbo with a clutch.

And yes, its control of the turbo should elimnate the need for a wastegate.

3. is there any potential efficiency/packaging/heat/other benefit in completely separating the turbine/MGU-h and compressor, with the compressor driven by its own electric motor? If so, are such arrangements disallowed by the apparently-quite-proscriptive rules?

The regulations define a single turbocharger, with single stage compressor and turbine mounted on the same shaft, with a motor-generator unit attached via gears and clutch. So the arrangement you describe is outlawed.

[Kalmake]

The main point to remember with the new unit the total allowed stored energy is 4Mj - about 160 BHP for 33.3 seconds. However, only 2Mj may be stored per lap, but 4Mj may be RELEASED on a lap. Because of the huge amount of torque available, this power needs to be carefully managed and doing this would be a full time job for the driver - so there is some computer control here - from 2014 we will see a new on-screen graphic showing how the ERS is being used and charged etc..

That 2MJ limit is only for kinetic. I think I saw a Renault quote saying it will be no problem to get the other 2MJ from MGU-H.

Driver can't control the petrol/electric ratio at all, it's all preprogrammed.

[Wuzak]

That 2MJ limit is only for kinetic. I think I saw a Renault quote saying it will be no problem to get the other 2MJ from MGU-H.

Driver can't control the petrol/electric ratio at all, it's all preprogrammed.

Renault are saying greater than 2MJ from the MGUH. The power from the MGUH can be directly sent to the MGUK - the direct transfer between the two is unlimited.

[JimboJones]

They won't run wastegates because the MGU-H manages all that. The boost level is 2.5 Bar above atmo. Don't forget that they will need to charge the ERS for qualifying and they can charge up to the maximum of 4Mj and release all of this on one qualifying lap but they may want to run another qually lap after 2 cooling down laps - in which case they would want the ability for both the GGU K and H to function as normal so that they can start with a full ERS..

Opening a wastegate for more power? As I said it doesnt apply. I believe the Turbo will run at a more or less constant 2.5 bar or as required for best performance. Note that when off-throttle the Turbo is fully powered up by the MGU-H for a) instant throttle response and b) better engine braking performance.

hmmm. Lightnight, doesn't sound to me like you actually have a clue what you talking about, rather just running off a load of jargon - I can tell you're not an engineer.
"MGU-H manages all that" - does an MGUH allow you to completely remove the affect of the turbine on back pressure?
"they would want the ability for both the MGU K and H to function as normal so that they can start with a full ERS" - a wastegate would not prevent normal operation.
"Opening a wastegate for more power? As I said it doesnt apply" - so there are no back pressure power losses from running a turbo?

Yes good response. Glad to see some people have got their heads around this! How people think a wastegate is required is strange - very 1980's in fact.

so when a team turns up with a wastegate, it will be because we have traveled back in time to the '80s...

The units produce, currently including ERS power, 810 BHP and 600 NM - and this is expected to rise to 850-860 in 2015.

interested in your source of this info.

Economy modes are likely to be quite complex I would suggest given the role of the ERS.

Complex? why would there be any 'economy' modes at all on a fuel limited turbo engine?

[Wuzak]

why would there be any 'economy' modes at all on a fuel limited turbo engine?

Because the amount of fuel they can use for the race is also limited.

[MatsNorway]

I have no clue on engines overall but wastegate i feel is a good idea. Sure you can limit the rpm on the turbo by braking it and get some energy out of that or something. but if you where to keep the turbo down and the pressure rises it would demand a stronger exhaust turbine. Stronger means heavier and heavier means slower spool up.

And that will be interesting to hear the development on, if we get to.. Heavier turbo also means bigger Turbo KERS. I guess its safe to assume that a stronger turbo also got less efficiency. And surely there is a point where the turbo braking will actually hurt the engine power? Risk of knock or something due to high temperatures on exhaust side.

Overall i guess it will be a balance walk..

4Mj = Could be good for qual
2Mj = Race optimum

Assuming they don`t have to have full size batteries.

Edited by MatsNorway, 10 August 2013 - 14:52.

[JimboJones]

Because the amount of fuel they can use for the race is also limited.

In which case you would lift and coast like the current cars do. My point is you would never run below the maximum fuel flow rate, as you'd lose too much power down the whole straight.

[Wuzak]

In which case you would lift and coast like the current cars do. My point is you would never run below the maximum fuel flow rate, as you'd lose too much power down the whole straight.

The current cars have different fuel maps, some of which give lower power and better economy.

[JimboJones]

The current cars have different fuel maps, some of which give lower power and better economy.

Agreed. To fuel save, they run a leaner fuel map, at a small cost to power, as well as lift and coast.
However, the current V8s are only restricted by the air they can ram into engine, so they have the luxury of running richer than normal anyway, to get best performance. Put a bunch more fuel in and you'll get a little extra power. Conversely, take a bunch of fuel out, and you'll only lose a little power.
Next year, it is the fuel that's limited, so the turbos will deliver what is required to burn this in the most efficient way, i.e. develop most power. Therefore, taking a bit of fuel out will probably scale the power output. Saving 5% fuel will cost about 5% power, which makes it a very expensive way to save fuel.