Looks like Turbo compound for diesel trucks is becoming off the
    shelf.

    http://www.voithturbo.de/vt_en_paa_road_motorenkomponente_turbocompound.htm


    "TurboCompound
    According to the European Exhaust Gas Norm Euro 5, from October
    2009, the
    borderline value for the emission of soot particles from heavy
    commercial
    vehicles will be set at 0.02 g/kWh. Nitric oxide emissions must not
    exceed a
    value of 2 g/kWh. It is assumed that from 2012, regulations will be
    even
    stricter with the introduction of Euro 6. Engine-related measures
    aiming at
    meeting this Euro 6 norm lead to increased fuel consumption. By
    utilizing the
    thermal energies occurring within the exhaust fumes, TurboCompound
    systems help
    to save up to 3 percent fuel. Consequently, CO2 emissions also drop.
    Voith Turbo
    supplies hydrodynamic couplings and pre-assembled systems for such
    TurboCompound
    systems."

    The 3% is an under estimation. DD claims 5%. Voith is not making the
    turbine
    apparently.

    Note the trade off between Nitric oxide emissions and fuel consumption.

    Nitric oxide never hurt anybody :) OK send me the proof!

    Like CO2 plants probably love it :)

    Also I'll bet that particle filter adds back pressure.

    Paul Lamar

What is in the blue drum is a hydrodynamic coupling that isolates severe diesel
torque variations from being applied to the turbine. Detroit Diesel does it
better putting the coupling closer to the crank shaft in the train of gears.
However the efficiency of these devices is about 97% or worse. In other words 3%
of the HP recovered by the turbine is thrown away in this device. It would be
better to come up with a purely mechanical device to damp the torque pulses such
as a one way clutch or belt drive. So far the truck guys are copying the scheme
used in the R3350 TC.

It is encouraging and ironic that now that we have people building turbo
compound engines we are now discussing the best way to do it.

Paul Lamar


Hello !

Compoundig principle is to add the power recovered by the turbine to the motor (crank)shaft. That means coping with the
torque pulses.
As a world leader in hydrodynamic coupling devices with or without gearboxes, it is not surprising that Voight provides
hydrodynamic coupling based systems.
A clutch used as torque limiter is likely to have a power efficiency not better than the 97% announced by Voight.
Of course a belt drive would damp the torque pulses, perhaps with a slightly better efficiency, but a turbine speed control
device (waste-gate) is to be added in case or belt failure...
Another solution would be to use the power recovered by the turbine to electric power generation. The turbine high rev's
fits small an light weight permanent magnet generators. The turbine speed does not need to be proportionnal to the engine
rev's and it can be controlled by the rectifier.
On a 200 HP aircraft engine cruising à 75%, the 3% of power announced would mean up to 3 kW of electric power : Enough power
to get read of the standard (low power efficient and heavy) belt driven generator, and also to feed electric fans for engine
cooling (allowing reduction of cooling induced drag)

Philippe Dejean