Atomization vs Vaporization

Steve.Flanagan at VerizonWireless.com Steve.Flanagan at VerizonWireless.com
Tue Dec 11 15:37:25 GMT 2001


Robert,

Good info,

But what can we do as engine tuners to  control Atomization vs Vaporization?

I am asking specifically for a turbo application.  

The only things I can play with are Intercooler Temp (which I want as cold
as possible), Boost (which I also want as high as possible),  Fuel Pressure,
and Injector Pulse width.

Are you better off with a Harder - Shorter spray or a Softer - Longer spray
(High fuel pressure vs Low Fuel pressure?) 

Here is a question I asked a week or two ago:

Does the temp of the Air coming out of the intercooler effect the
atomization process?  Can too cold of an air charge hurt atomization????????

One last thing, what effect does a temp change on air do the requirement for
the fuel?  Lets say you can get the air charge to go from 130 deg C to say
100 deg C,  how much fuel should be added.  Can you simply use the PV=nrT
(converting to Deg K) formula and consider it a linear function.  

Thanks

Steve

-----Original Message-----
From: Robert Harris [mailto:bob at bobthecomputerguy.com]
Sent: Monday, December 10, 2001 12:54 PM
To: diy_efi at diy-efi.org
Subject: Atomization vs Vaporization


Revist Ideal Gas Laws.

The absorbtion of heat in the intake tract and the cylinder prior to
combustion is not to affect the energy release of combustion, it is to both
reduce the work of induction and to increase the amount of the inducted
charge.

The heat of vaporization of fuel is large with respect to the inducted air
mass and thus can cause significant changes in the temperature and thus
total
quantity of inlet charge.

Liquid fuel atomized to 10 microns or less ( you will see that number many
times ) burns not as a liquid - droplet by droplet - as essentially
identical
to a pre-mixed gas.

A liquid "vaporized" has transitions to a gas state - with a significant
size
change.  Water expands approx 1800 times going to steam - fuel significantly
less, but the resultant vapor molecule is orders of magnitude greater in
size
than the liquid.

Atomized - preferably to 10 micron or less - fuel absorbs heat - thus
cooling
the intake charge and increasing the fresh charge inductable - without
appreciatory changing the size of the fuel particle

Vaporization the fuel absorbs the heat, but since a state change is
involved,
it greatly expands the space occupied by the fuel.  The benefits of cooling
are offset by the loss of space by vaporization.

Atomize - not vaporize.


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