Fuel Atomisation

[Arnaud Westenberg]

Bernd Felsche wrote:

 > How many Joules are going to be absorbed in the vapourization process?
 > Unless you're evaporating water, you won't be removing significant
 > heat without running very rich mixtures.

Running very rich mixtures to aid cooling is quite a common strategy, 
especially in racing applications. So delaying vaporization until the 
charge is in the cylinder, without the need to go extra rich, would 
result in the benefits Greg mentioned.

 > Reduces the pressure by how much to vapourize a liquid droplet into a
 >  gas?

 >> Good atomization also leads to more uniform distribution of the fuel
 >>  throughout the charge, leading to better, faster combustion (also
 >>  more power and efficiency here).

 > And increases the tendency to detonate (knock).

The faster flame propagation would expose the end gasses _shorter_ to 
the increased temp/pressures, hence reduce the tendency to knock.

Besides the vaporization heat absorbed by the fuel during compression, 
the faster burn rate of the more homogeneous distributed fuel allows for 
  more ignition retard. Obviously the retard results in lower 
compression end pressures and temperatures, reducing the tendency to knock.

___

Arnaud

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