Water Injection (Was: Re: Wide Ratio O2)

[David Piper]

Naturally, you should design the nozzle for fine atomization and sufficient
pressure for choked flow.  Keep absolute pressure upstream at least 2X
downstream.  In addition to damage due to physical impingment on the
impeller leading edges, the liquid cavitates with millions of tiny toroidal
shapped droplets colapsing on the compressor blade while vaporizing during
exposure to the large velocity gradient present at the inducer.  The
toroidal shape focuses the tensor to a very small area which increases the
pressure to extreme levels and eventually removes metal from stress fatique.
The effect is gradual and slight but cummulative; more noticable near center
axis of blade on its leading edges.  Never lost a compressor blade.  May
actually improve efficiency similar to extrude honing?  Never have seen any
machine design that makes use of this fascinating physical phenomenon of the
toroidal shapes capability of concentrating force.

TurboDave

At 11:07 AM 3/23/98 +0000, you wrote:
>Peter,
>
>What causes the erosion?  Are the water droplets eroding the turbine 
>blade just from their mechanical impact against the turbine blade, 
>traveling at near the speed of sound, or is it a chemical thing, or 
>both?  If you injected an atomized stream of fuel upstream of the 
>turbo, would the same thing happen??
>	Just curious.  Just sitting here trying to hone my hat to a fine 
>point.
>
>Zack
>
>
>> From:          PNefdt <PNefdt at aol.com>
>> Date:          Mon, 23 Mar 1998 21:09:12 EST
>> To:            diy_efi at efi332.eng.ohio-state.edu
>> Subject:       Re: Water Injection (Was: Re: Wide Ratio O2)
>> Reply-to:      diy_efi at efi332.eng.ohio-state.edu
>
>> I'm new here, so Hi.
>> The Volvo Group-A (think it was) turbos, used a second Bosch fuel injection
>> system to inject water. This was to inject water AFTER the turbo, otherwise
>> compressor blade erosion occurs.
>> 
>> Regards, Peter.
>> 
>> 
>
>