Intake Air Humidity 4

[beekeeper6]

I've read recently about newer engines that will include a humidity sensor so the ECU knows the humidity of the intake air. Now I understand how the humidity level of intake air affects combustion, but don't knock sensors and other existing technology already essentially cover this ground?

 

[mattsooty]

XXXLR8R,

I don't see how injecting water pre-turbine is going to offer you any benefits.

If its throttle response/smoke reduction you want then you need more boost, more quickly - and VNT turbos are a fairly mature technology which work fairly well.

However, wont cooling the exhaust gas before it reaches the turbocharger rob you of the ability to actually produce this boost?

Besides, surely the turbine wheel would need to be fashioned from a pretty heroic material to cope with the erosion caused by the water droplets and also the thermal shock caused when the water injection begins (unless you propose that it always be running).


MS

 

[tha89sx]

i agree with mattsooty

i dont see how removing the exhaust energy before the exhaust gets to the turbine will help in spooling the turbo, which is your ultimate goal is it not?

if you want better spool up you need to match your turbos properly

 

[dcasto]

The only thing I see that could work would be to inject water in the exhaust to make steam. There would be more pounds per hour going across the turbine and more work avaiable for the compressor. The thermodynamics say it will work, but the practicality and physical control would be difficult.

Things like, physically you'd condense water in the turbine, water saturated with CO2 and therfore very corrosive. If you over injected the water, you'd hit the turbo with liquid and the thing would self distruct.

 

[patprimmer]

Now that this thread has been successfully hijacked and we know exactly what you are getting at, a short shot of Nitrous Oxide in the inlet to compensate for extra fuel sure spools them up quick and removes smoke. A bit expensive to install and run though.

I have never seen your subject discussed before. It is different enough to the heading on this thread to deserve it's own heading.

I still recommend a site search as this site contains an enormous amount of information for those prepared to look, and no, I won't do it AGAIN for you.

Another way to overcome smoke, but not lag is to reduce fuel until boost builds or tie maximum fuel flow to boost.

In practical terms, as others have said, correct matching of components is the best way to reduce lag. Compounding a turbo and a positive displacement crank driven blower is another.

When you start your new thread, it will be best to cut and paste your question as asked here and the appropriate responses, then red flag your questions here and specific responses to it, BUT NOT responses relevant to other discussions. This course might attract the interest of several members with vast experience in the subject matter.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mishar]

Back to the original track (I hope).

I can see that water, evaporating in the intake manifold, LOWERS THE PRESSURE and increases intake air mass, than further evaporating in the cylinder RISES THE PRESSURE expanding to steam. Some smart water.

I think that neither will happen. Evaporating in the intake manifold it lowers temperature but adds volume of the steam, so that total volume and pressure will remain the same. Evaporating in the cylinder it would add pressure but lowers the temperature so pressure stays the same. Only effect, if I am right, is less oxygen in the process, mining less power. Off course if it would knock otherwise it’s good.

Trying to think this trough I was thinking how to simplify the problem in order to establish solid argument point. I came to the question: what will happen to the pressure of closed system if some water evaporates in it?

 

[patprimmer]

Some thermo calculations done previously do support the idea that as the steam evaporates you get out more than you put in.

The thermo calcs at the time were outside my sphere of knowledge, but were done by a member with good credibility, and not disputed by others with high levels of credibility.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mishar]

I think I found the link following the links you posted, but unfortunately there is no page there anymore. My thermodynamics is a bit rusty, but I wouldn’t mind polishing it a bit for the occasion.

Regarding credibility, experience teaches me always to save some skepticism, if possible. I’ve had quite a few perpetuum mobile discussions with very credible engineers. That’s so loveable idea. Nobody is immune.