Honda Power Unit Hardware & Software

[trinidefender]

That is correct. However there is a range of outcomes from "Maximise ICE crankshaft power regardless of turbine output" through to "Maximise turbine output regardless of crank output". Somewhere between these two is a sweet spot where total output is maximised. ICE crankshaft power will not be maximal at this sweet spot.

but in principle we are not designing an engine around this sweet spot, we are designing around another spot because in principle the rules do not allow free choice of turbine power we are designing an engine to work around mean turbine power dictated by the 120 kW mu-k limit the mean turbine power required depends on how much mean mu-k power comes from braking recovery (minus spoolup) energy brake recovery is kept quite low by a torque limit rule (though BR is very circuit-specific) so about 90 kW seems to be needed from the turbine (90 kW mean throughout WOT time) this seems to match the iirc 80 kW (presumably continuous rating?) stated for the MM unit precedent shows axial turbine power adds up to 18% to crank power essentially 'free' ie with negligible loss of crankshaft power this is what blowdown running is all about (exhaust pressure not significantly above ambient after exhaust BDC) our mep and CR suggest we can have around 12-15% 'free' but to have 120 kW mu-k freely available we need more turbine power than this dictating a design that has raised exhaust pressure aka 'backpressure' (significantly above ambient throughout) other precedent shows this is competitive (backpressure with boost raised may cost no crankshaft power and increase turbine power) Merc exhaust suggests this (pressure running of the turbine), but F's and R's is compatible with this (an element of pressure)

so the Honda exhaust system should tell us something

btw 120 kW assumes 95% efficiency at the motor (of electrical power to crankshaft by coupling gear) - so we might get 122 kW

I disagree - we are almost certainly designing around the "sweet spot".

With electrical efficiency of 95% for both MGUK and MGUH, nett turbine power would need to be 133 kW to supply 120 kW of work at the MGUH.

For 3.5 bar MAP, 3.0 bar exhAP, MAF = 0.056 kg/s, Exh MF = 0.059 kg/s, EGT = 800*C, turb & comp efficiencies = 0.8 :-

Compressor power = 90kW
Turbine power = 137kW
Nett power = 47kW

These numbers are steady flow (pressure turbine) so the turbine power will be higher courtesy of blowdown energy - say another 50kW, for a total Nett power of 97 kW. We are still 36kW short of the 133 required to drive the MGUK at 120kW continuously - the question is - is enough braking energy harvested to make up the shortfall (and provide some spare energy for spool up and emergency power techniques (where the compressor andthe MGUK ar both driven from the ES to maximise crankshaft power)). The answer is almost certainly no. Assuming (generously) that time under brakes is 25% of time under full throttle, and that harvesting is 120 kW throughout braking events, there will be 30kW available during full throttle events from braking regen'.

Even without the above analysis, it is known that the cars deplete the ES while running at race speed, so clearly any extra power from the MGUH would be useable.

gruntguru take it for what you will but I think you should revise your exhaust gas temperature. The maximum continuous T5 (T5 is just a term used by this particular manufacturer for the temperature reading obtained between the first and second stage turbines) limit for normal dual engine running in our helicopters is 893 degrees Celsius. Our single engine max T5 is 926 degrees. Note that these figures are for the extremely restrictive world of aviation where things like engine limitations are kept quite conservative for obvious reasons. So that is 926 degrees C after having passed through one turbine and with the reliability being the main concern.

For reference our 2 minute power T5 limit is 944 degrees C and the 30 second T5 limit is 996 degrees C. Note that the application date for engine certification was December 4th, 2003 with it being actually designed quite a while before that.

In light of what I know and the information provided I would think 1000 degrees C would be a safe bet for a maximum exhaust gas flow temp.

[gruntguru]

Yes, I agree the turbine will tolerate a much higher temperature (900*C is common in turbo installations) but I figure the temp will be a lot lower due to lean operation. Must do some sums and come up with a better guesstimate.

Note. Recip exhaust is lower temp than GT due to in-cylinder expansion. OTOH GT's run much leaner than typical recip (mainly to reduce EGT).

[Tommy Cookers]

I disagree - we are almost certainly designing around the "sweet spot".
With electrical efficiency of 95% for both MGUK and MGUH, nett turbine power would need to be 133 kW to supply 120 kW of work at the MGUH.

For 3.5 bar MAP, 3.0 bar exhAP, MAF = 0.056 kg/s, Exh MF = 0.059 kg/s, EGT = 800*C, turb & comp efficiencies = 0.8 :-
Compressor power = 90kW
Turbine power = 137kW
Nett power = 47kW

is 3.5 bar induction pressure enough to get the required air massflow with a 3 bar exhaust pressure ?
or have I misunderstood ?

[gruntguru]

I disagree - we are almost certainly designing around the "sweet spot".
With electrical efficiency of 95% for both MGUK and MGUH, nett turbine power would need to be 133 kW to supply 120 kW of work at the MGUH.

For 3.5 bar MAP, 3.0 bar exhAP, MAF = 0.56 kg/s, Exh MF = 0.59 kg/s, EGT = 800*C, turb & comp efficiencies = 0.8 :-
Compressor power = 90kW
Turbine power = 137kW
Nett power = 47kW

is 3.5 bar induction pressure enough to get the required air massflow with a 3 bar exhaust pressure ?
or have I misunderstood ?

Not sure if I understand your question either - so this may be the wrong answer.

The back pressure will only have a small effect on the mass flow. It is possible to run BP somewhat higher than MAP - the downsides would be loss of scavenging, EGR, heat etc.

On MAP. 10,500 rpm, 110% VE, air density 1.2kg/m3, 3.5 PR gives 0.647 kg/s with intercooling back to ambient 20*C
With CAT = 70*C massflow drops to 0.55

Fuel flow is 0.027 so AFR = 0.55/0.027 = 19.8

[Tommy Cookers]

yes, on thinking, the dP of +0.5 bar seems ok (eg related to NA F1)
I just did a shopping trip, using mostly a dP of -0.8 bar
if I had driven a motorway I might have reached -0.1 bar
(and have flown at a dP only to about +0.7 bar but have seen flying at around +4 bar)

your nett power figure doesn't seem very far from values that others produced in the past using more conventional AFR and boost

yes it's easier believe this is near 'sweet spot' running if we imagine that the compressor was crankshaft-driven

[gruntguru]

An efficient turbo installation will have a positive dp. What they are running in F1 will depend how much energy they choose to extract from the MGUH. The Garrett paper (Diesel TC) referenced earlier had a positive dp. The scavenging and cylinder cooling benefits are even more important with an SI turbo compound like F1.

I assume your shopping trolley is a diesel? Is the BP gauge standard or did you install it? In full load running the dp will increase as the headers heat up then stabilise. Wastegates and throttling will reduce dp.

[Forza]

[ringo]

Not sure if I understand your question either - so this may be the wrong answer.

The back pressure will only have a small effect on the mass flow. It is possible to run BP somewhat higher than MAP - the downsides would be loss of scavenging, EGR, heat etc.

Your mass flow is not affected by the backpressure, mass flow is based on the mass of air you take into the engine, and that same quanity of mass has to leave the engine at the same rate, unless the engine would be accumulating mass. I see what you are trying to say, but back pressure is not a cause, it's an effect.

On MAP. 10,500 rpm, 110% VE, air density 1.2kg/m3, 3.5 PR gives 0.647 kg/s with intercooling back to ambient 20*C
With CAT = 70*C massflow drops to 0.55

Fuel flow is 0.027 so AFR = 0.55/0.027 = 19.8

This seems more alligned to finding mass flow, but don't try to relate back pressure to this. After you find this mass flow, that's what it's going to be. The back pressure is simply the intermediate pressure before the turbine and after the exhuast stroke. This can be found by using some thermo equations.

from my calcs, it reduces as you engine speed increases and boost decrease. at max power it's about 7 bar.
Keep in mind by boost is around 1 barg at 11,000 rpm. But thg back pressure is more dependent on your combustion efficiency, temperatures, pressure etc.

[ringo]

Your boost pressure is simply not going to be lower than you back pressure.
The additional energy added to the flow by the fuel and it's combustion will not allow it to be of a lower pressure than the intake pressure.
I only see that happening if there was no combustion and heat was drawn from the engine. This is not likley possible.
I hope i have interpreted the discussion correctly. if not i stand to be corrected.

[gruntguru]

Couple of points Ringo.
1. BP will affect mass flow slightly because there will be reduced scavenging, in fact if BP is much higher than MAP, exhaust may flow into the intake during overlap.

2. BP will be determined by the turbine characteristics (mainly housing A/R) and turbine speed which is determined by the MGUH and the harvesting load chosen. It is certainly possible to increase the BP above MAP but I doubt they would do that for obvious airflow, detonation and cooling reasons.

3. "at max power it is about 7 bar" What are you referring to here?

[Töm87]

What are the expectations for Honda?
Do people think they'll be on the Mercedes level or even slightly better?
Or is it more likely they'll be in the neighborhood of Renault and Ferrari?

[marcush.]

What are the expectations for Honda?
Do people think they'll be on the Mercedes level or even slightly better?
Or is it more likely they'll be in the neighborhood of Renault and Ferrari?

It depends on Daimlers stance in the engine freeze matter I believe...If Mercedes decides to keep the freeze Honda will have the optimised Daimler PU and Mercedes will only be in a position to make small gains as will Ferrari and Renault .

The pecking order should be Honda -Mercedes -Renault -Ferrari then

If it´s open -Mercedes has the chance to build on the experience won this year and find the next golden bullet...
giving them the opportunity to once more dominate -or fail...It´s a matter of confidence in your abilities to allow the unfreeze ..but I firmly believe it´s the only chance for Daimler to have any hope to remain the top PU in 2015. ...

Honda has all the insight into what Daimler did ,no question about this.it´s nothing like they had no access to all the detail
even though they surely have no access to the code -still you can learn a lot about what going on from what the PU does do

No wonder Mclaren were treated like orphans from Mercedes side ... but still they learned an awful lot from the leader in class. Daimler made a big mistake here allowing Mclaren to run their PU this year.They would have done a lot better supplying a cosworth unit to them ....

[goonerf1]

What are the expectations for Honda?
Do people think they'll be on the Mercedes level or even slightly better?
Or is it more likely they'll be in the neighborhood of Renault and Ferrari?

My gut feeling is the performance figures will be pretty similar to Merc's. It'll be getting the driveability sorted that takes the time.

Tiny engines plus electrical systems are so perfectly Japanese that I just can't see them making a shoddy PU to be honest .

[SiLo]

A year on the test bed does not equate to a a year of racing. Plus, we all know Mercedes starting building way before anyone else. I wouldn't be surprised if they had a longer lead time than even Honda at this point.

I'm going to say that they won't be on the same level as Mercedes when it comes to drivability, but possibly power they will. Only a guess mind.

[nacho]

I still think no matter how well Mercedes tries to keep things secret, the data about their engine can be either directly observed or calculated/deducted. The question is how much Honda would need it but surely it won't be worse knowing what the greatest engine is doing. At least they have a lot better reference points than Renault and Ferrari.