Dual Hybrid Turbo

[Kowalski]

I found this today

http://www.greencarcongress.com/2006/06 ... plies.html

The article isn't particularly new (June 2006) but the technology is interesting and fairly clever (the turbo in particular).

How integrated are the two turbos, i.e. is it one shaft or two?

Is this not news to anybody?

[CitroJim]

Now that's interesting A good find!

Two shafts by the looks of it with a sort of diverter valve to decide which of the turbos spool up. It'll be fun when that and the two wastegates get all carboned up and stick...

One bit makes no immediate sense whatsoever though

This geometry also makes it possible to significantly reduce swirl by limiting thermal losses against the walls. These developments allow greater homogeneity of the air-fuel blend, resulting in a significant improvement to the engine’s overall efficiency

Conventional diesel theory suggests that good mixture homogenisation is only achieved with high levels of swirl, the higher the better and in fact all diesel engines, be they DI or IDI, go all out to get as much swirl as possible Or are they just using a bit of "bull baffles brains" and a set of words that look good. A kind of "spin" perhaps?

I guess what they're trying to say is that running a lot of boost all the time allows them to reduce the compression ratio a bit and the additional boost pressure makes up for what would otherwise be lost with less swirl. It'll be certainly quieter and will, I guess, run more like a petrol engine than a traditional diesel.

Those injection pressures You don't want a leak on the common rail

[Kowalski]

Conventional diesel theory suggests that good mixture homogenisation is only achieved with high levels of swirl, the higher the better and in fact all diesel engines, be they DI or IDI, go all out to get as much swirl as possible Or are they just using a bit of "bull baffles brains" and a set of words that look good. A kind of "spin" perhaps?

I guess what they're trying to say is that running a lot of boost all the time allows them to reduce the compression ratio a bit and the additional boost pressure makes up for what would otherwise be lost with less swirl. It'll be certainly quieter and will, I guess, run more like a petrol engine than a traditional diesel.

I think you're right about the swirl, you do need to mix your air and fuel to get them to burn and since the air goes in on its own first then the fuel is added, lots of in cylinder swirl is needed.

What they're saying about swirl has to do with their combustion chamber design rather than the turbo. I think that they've tried to reduce the amount of heat that they lose through the cylinder walls which can cause cold spots where the fuel didn't burn so well.

Personally, I don't see the reduced compression ratio as good for economy and using the turbo all of the time is bad too since the turbo causes backpressure which means the engine has to work harder to run the turbo.