Honda Power Unit Hardware & Software

[basti313]

The 'Skunkworks' term has always seemed a little silly to me.

True. We also have one in our company...basically when they start hoping on the skunkworks it is time to leave the company. Because it means they are more or less out of ideas how to make the needed step with normal engineering. They need a new idea and do not really have a suitable one for the usual engineering.

[basti313]

being compressed to 500 bar will make the fuel hot anyway ?

Will only raise the temperature slightly. Not much energy required to compress a liquid. I will see if I can find some thermodynamic tables for compressed liquid hydrocarbons.

EDIT. Couldn't find tables for HC but water will increase in temp by 3.44 *C when compressed from 1 bar to 500 bar.

Water is not compressible...not sure how you can get the value. I would rather see it for a compressible fluid like fuel, I think your order of magnitude is ok. You can just roughly calculate it with the volume difference, which is not big in compresses liquids in comparison to gases.

[Bence]

Lateral thinking is absolutely beneficial - even desireable, when things are just too settled or don't produce appropriate results. A Skunkworks team or Old Boys Club, is based on people who intuitively "know" what would be/work better, but because of the usual circular corporate thinking wouldn't allow them to act. Therefore, a rogue faction is needed. Many engineers spent hundreds of nights working on projects which were not part of the official programme.

And when you think of revolutionary solutions in the automotive field, you can thank them to these lateral thinkers. Thinking and questioning everything is the real power of a truly unlimited mind. And it will produce remarkable solutions.

One example: Koenigsegg's direct drive. Just one 2.85 final drive, no tranny. The ICE and the electric motors work in a perfect yin-yang harmony.

[ringo]

being compressed to 500 bar will make the fuel hot anyway ?

Will only raise the temperature slightly. Not much energy required to compress a liquid. I will see if I can find some thermodynamic tables for compressed liquid hydrocarbons.

EDIT. Couldn't find tables for HC but water will increase in temp by 3.44 *C when compressed from 1 bar to 500 bar.

Water is not compressible...not sure how you can get the value. I would rather see it for a compressible fluid like fuel, I think your order of magnitude is ok. You can just roughly calculate it with the volume difference, which is not big in compresses liquids in comparison to gases.

Water is not compressible but it can still be pressurized. The heat in the fuel is mainly from the inefficiency of the pump.
I believe pressurizing the fuel is more to do with the spray pattern and penetration of the injector into the combustion chamber; among other things.

[Tommy Cookers]

...... Koenigsegg's direct drive. Just one 2.85 final drive, no tranny. The ICE and the electric motors work in a perfect yin-yang harmony.

this would appear to unlock the hydraulic coupling, so allowing the EM to draw less current than it would otherwise want to draw
it's perverse to describe this as increasing the power (as some do)
and it seems to be a non-torque-multiplying coupling

[godlameroso]

being compressed to 500 bar will make the fuel hot anyway ?

Will only raise the temperature slightly. Not much energy required to compress a liquid. I will see if I can find some thermodynamic tables for compressed liquid hydrocarbons.

EDIT. Couldn't find tables for HC but water will increase in temp by 3.44 *C when compressed from 1 bar to 500 bar.

Water is not compressible...not sure how you can get the value. I would rather see it for a compressible fluid like fuel, I think your order of magnitude is ok. You can just roughly calculate it with the volume difference, which is not big in compresses liquids in comparison to gases.

It's still tricky because increasing the pressure also inhibits the ability to vaporize fuel, because as we all know, boiling points tend to rise with pressure.

[basti313]

Will only raise the temperature slightly. Not much energy required to compress a liquid. I will see if I can find some thermodynamic tables for compressed liquid hydrocarbons.

EDIT. Couldn't find tables for HC but water will increase in temp by 3.44 *C when compressed from 1 bar to 500 bar.

Water is not compressible...not sure how you can get the value. I would rather see it for a compressible fluid like fuel, I think your order of magnitude is ok. You can just roughly calculate it with the volume difference, which is not big in compresses liquids in comparison to gases.

It's still tricky because increasing the pressure also inhibits the ability to vaporize fuel, because as we all know, boiling points tend to rise with pressure.

Well, vaporizing the fuel is not really a problem. The compressed air is always hot enough - the air needs to be cooled by the fuel for more performance... The question is when it exactly the fuel vaporizes and when it starts burning. In modern F1 this is not only a fuel supplier problem, but when we look at the knocking, all comes together:
- fuel
- injection strategy
- compaction ratio
- air temperature

Especially the last point is hard to change...if your intercooler is too week you may be loosing performance, just because you can not make your fuel and injection strategy work.

[godlameroso]

Do you suppose that's why some PU manufacturers are using more than one IC? Perhaps to have more control over charge cooling?

[gruntguru]

Water is not compressible...not sure how you can get the value. I would rather see it for a compressible fluid like fuel, I think your order of magnitude is ok. You can just roughly calculate it with the volume difference, which is not big in compresses liquids in comparison to gases.

It's still tricky because increasing the pressure also inhibits the ability to vaporize fuel, because as we all know, boiling points tend to rise with pressure.

Well, vaporizing the fuel is not really a problem. The compressed air is always hot enough - the air needs to be cooled by the fuel for more performance... The question is when it exactly the fuel vaporizes and when it starts burning. In modern F1 this is not only a fuel supplier problem, but when we look at the knocking, all comes together:
- fuel
- injection strategy
- compaction ratio
- air temperature
Especially the last point is hard to change...if your intercooler is too week you may be loosing performance, just because you can not make your fuel and injection strategy work.

In response to various points above.

1. Everything is compressible - including solids and liquids. The heat of compression comes from the work required which is the integral of P.dV For liquids and solids, dV (the change in volume) is very small so the work done is also very small (eg Compressors need a lot more energy than pumps. Air gets very hot when compressed in a compressor or a piston engine compression stroke).

2. The value can calculated knowing the compressibility u of the liquid 0.46E-6 (kPaE-1) for water and 1.2E-6 for n-octane
So the work is W=(P2+P1)/2 x (V2-V1) (trapezoidal area under a straight line on a P-V chart)
= (P2+P1)/2 x uV(P2-P1)
= P2/2 x uVP2 (P1<<P2)
= (uVP2^2)/2
= (0.46E-6 x 0.001 x (50E3)^2)/2 = 0.575 KJ/kg (water) and 1.5 KJ/kg (octane)
Specific heat for water is 4.2 kJ/(kg.K) so each kilogram of water will increase temp by 0.575/4.2 = 0.13*C
Specific heat for octane is 2.1 kJ/(kg.K) so each kilogram will increase temp by 1.5/2.1 = 0.71*C
This the temperature rise for a 100% efficient pump, however pumps tend to have high efficiency (above 90%) so the actual heating will be no more than 10% higher.
I will fix the error in my earlier post.

3. Vaporisation occurs after the injector nozzle when the pressure is much lower than 500 bar. Vaporisation before the nozzle is extremely undesirable.

4. Intercooling is not required to increase air density (higher boost will create all the airflow needed for the limited fuel). Intercooling has a negative effect on energy recovery and on fuel vaporisation. (Honda found it desirable to reduce the intercooling to improve efficiency on the RA168e). Intercooling is needed mainly to control knock and limit combustion chamber thermal stress.

[Tommy Cookers]

and remember of course, that any octane in our motor fuel will be iso-octane (its octane number=100)
not normal octane (n-octane), its octane number is negative (-12 iirc)

[basti313]

Do you suppose that's why some PU manufacturers are using more than one IC? Perhaps to have more control over charge cooling?

Sure. Depending on the outside temperature and overall cooling it may be necessary to change the IC. But I guess most adjustments of the IC will be done by flow control of the water. I was not sure, why they are so keen on water/air intercoolers, but this may be the reason.

2. The value can calculated knowing the compressibility u of the liquid 0.46E-6 (kPaE-1) for water and 1.2E-6 for n-octane

Nice calculation. Upvote for that!

3. Vaporisation occurs after the injector nozzle when the pressure is much lower than 500 bar. Vaporisation before the nozzle is extremely undesirable.

Sure. But according to the numbers of Merc there are 400Bar in the combustion chamber after compressing the air. So we surely need quite a lot of heat to vaporize the fuel and I guess the margins to knocking are really small.

Intercooling is needed mainly to control knock and limit combustion chamber thermal stress.

Sure. That is what I wanted to tell with my post too.

[PlatinumZealot]

The fuel is atomized before vaporization. When atomized the surface area of the fuel increases millions of times.

Vapourization si different from atomization. Vapourization is dependent on the vapour pressure and temeprature. The fuell will still vapourize when sprayed into the combustion chamber because the fuel vapour pressure in the chamber would still be almost zero just at the point of spraying. It will increase as more fuel evaporates.

The atomization helps increase the surface area with reduces surface tension and aid vaporization.

I dont remember the technical details and i never did any course in aerosols so that is about as deep is I can go.

[basti313]

The fuel is atomized before vaporization.

.........

I dont remember the technical details and i never did any course in aerosols so that is about as deep is I can go.

WTF??? Sorry, but this is pure nonsense. I do not even know where to start with arguments...this is first class chemistry.

[gruntguru]

3. Vaporisation occurs after the injector nozzle when the pressure is much lower than 500 bar. Vaporisation before the nozzle is extremely undesirable.

Sure. But according to the numbers of Merc there are 400Bar in the combustion chamber after compressing the air. So we surely need quite a lot of heat to vaporize the fuel and I guess the margins to knocking are really small.

400 Bar is peak combustion pressure - usually about 15* ATDC but probably a bit earlier in these "rapid combustion" engines.

Presumably all (certainly most) of the fuel is injected much earlier than that.

[Jef Patat]

The fuel is atomized before vaporization.

.........

I dont remember the technical details and i never did any course in aerosols so that is about as deep is I can go.

WTF??? Sorry, but this is pure nonsense. I do not even know where to start with arguments...this is first class chemistry.

When I was at university this was physics and not chemistry. I don't see where PlatinumZealot is incorrect. Instead of spreading nonsense: here are facts:

https://en.wikipedia.org/wiki/Spray_(liquid_drop)

Drop size is critical because the large surface area of a finely atomized spray enhances fuel evaporation rate. Dispersion of the fuel into the combustion air is critical to maximize the efficiency of these systems

If you master your first class chemistry that well, I hope you remember some physics and it should make perfect sense. Atomize first to have a bigger surface and with that bigger surface comes easier vaporization.