Have you watched the atomization of a 5-hole nozzle vs a 7-hole nozzle during testing in person? What I mean by this is the actual throttling of the needle on the seat. The discharge rate of a different nozzle design effects this far more than the hole count.
No, but I have watched the sunset in the Hamptons.
Again, I don't disagree with the point you're making but you are missing my point. My point has nothing to do with hole count, but rather orifice size. A smaller orifice will result in a smaller average droplet size,
all other factors being equal. The only reason I brought up hole count was to bridge this theoretical discussion to a practical case involving a comparison of comparably flowing injectors.
Atomization will also be affected by the pressure of the environment the jet is being sprayed into because a higher environmental pressure will break down surface tension on the droplets resulting in a lower droplet size. Assuming both injectors are used in the same engine, this factor is equal and does not favor either a larger orifice or smaller orifice injector
with respect to atomization. As an aside, a higher environmental pressure will adversely affect a jet of smaller droplets more so than the larger droplets owing to the lower inertia of the smaller droplets so this does have implications for jet penetration and the suitability of certain injectors for certain applications.
Injection pressure also will affect the degree of atomization, and for similar reasons to above a higher injection pressure will result in smaller droplets. Since this factor is adjustable I think it is reasonable to consider it equal for both, or at least it could be made that way, and so it also does not favor a larger or smaller orifice injector
with respect to atomization.
So with the other primary factors that affect droplet size being more or less equal this brings us back to orifice size as the chief determinant of droplet size.
As far as throttling goes, that will result in a sudden expansion of the fluid stream which will increase the divergence of the stream, or in other words fan out the spray more. This however will be accompanied by a decrease in intermolecular collisions which manifests itself as a pressure decrease. This decreases, rather than increases, the opposition to surface tension and should have the tendency of reducing droplet breakup meaning it will not decrease the average size of the individual droplets.
I assume you're saying that you observed the throttling to be greater with the 5 hole injectors versus the 7 hole injectors, but correct me if I'm wrong. If that's what you're saying then I would anticipate broader jets from the 5 hole injector in contrast to the 7 hole injector. I would not however anticipate a change in the size of the droplets themselves which was my original point. With that said, from what you're saying about the throttling I'm going to guess that the 5 hole injector you observed in comparison to the 7 hole injector showed a greater fuel dispersion per jet. That doesn't surprise me and in fact I listed dispersion as an advantage of 5 hole injectors over 7 hole injectors in my prior post.
As an aside, I think you and I are in agreement on just about every point but there are two different conversations going on at the same time which is blurring this. One is the discussion of the fluid dynamics and chemistry in general, and the other is the recurring 7 hole vs 5 hole injector debate. I've been trying to stick to the former and avoid the latter because it always turns out unproductive. Also, for the record, anything I've linked references to or have explained in detail in my posts is not an attempt to educate you but so that anybody reading this who is not familiar with the underlying science has a starting point to begin researching these things and learning for themselves. An educated consumer is a happy consumer and things have come a long way from the days of buying a 90 hp injector.
