[s-cars] water injection

[Larry C Leung]

I'm no expert, but things I'd consider:

1) Water is denser than gasoline, so an equal sized drop will
carry abot 30% more mass/drop, therefore, from Newton's
2nd Law (F=ma) each drop hitting the impellor blades will
increase the load by 30%, no clue on erosion effects

2) Gasoline has a MUCH higher vapor pressure, so it may
still atomize nearly completely before it hit the impellor of
the Corvair's Turbo, especially in such an environment of
high flow, swirl and turbulance. 

Just a few thoughts as to why the Corvair's turbo survived.
My instincts say I doubt that a turbo impellor would be 
happy having water thrown at it. From what I know, water
is also quite abrasive at high velocities, don't know about
gasoline. 

My $0.02

LL - NY




> Date: Sun, 24 Oct 2004 01:14:58 -0400
> From: kirbyasmith <kirbyasmith at gwi.net>
> Subject: Re: [s-cars] water injection
> To: Joe Pizzimenti <joe.pizzimenti at gmail.com>
> Cc: s-car-list at audifans.com
> Message-ID: <417B3A52.EA4B74D6 at gwi.net>
> Content-Type: text/plain; charset=us-ascii
> 
> While injecting after the intercooler is clearly the most thermally
> efficient approach, and before the turbo not recommended, there is 
> some
> question in my mind of just what damage occurs with upstream water
> injection, assuming it is a fine spray.  Turbo Corvairs were of 
> sucker
> architecture, and at full boost (about 10 psi into 2.7 liters), the
> Carter YH sidedraft carburator was certainly streaming gasoline 
> that
> hadn't yet vaporized right onto the compressor blades.
> 
> I never saw any sign of erosion on the blades of the OEM (TRW) 
> turbo
> compressor (reportedly good to 80 krpm) after 120 kmiles and 300 
> laps
> around Briar raceway, nor heard of erosion on the later available
> aftermarket compressor (good to 120 krpm).  This, of course, 
> doesn't
> prove upstream water injection wouldn't be bad for a K24/K26/etc. 
> Anyone know of any facts supporting the contention that upstream 
> water
>  damages compressors?
> 
> kirby
>  
>