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Fuel Injector Spray Angle & Pattern

Picture1 source:

Picture2 source:

Picture3 source:

The above are three spray models. The latter one is fuel injector spray. Consider I have a closed container which I can increase its pressure by any means such by pumping, reduce the volume like with piston, etc, and on the bottom side there is a small opening area a (i.e, a nozzle with diameter 1mm). My question is: How do I quantify the haze-ness/misty-ness or the level of atomization of that spray, including the size of the haze/mist it produced?

Note: The background of my question is that the most atomized the fuel in the combustion chamber the better the combustion, then I searched about fuel injector. But then I realized that I also frequently spray my garden to kill the insects that ruin the plants, and also in many occasions I used spray perfume or deodorant or room fragrant, and so on. There are many applications. In my observation, the spray output are different, more or less their output form are represented by those three pictures.

  • $\begingroup$ Combustion is also controlled by spray direction and pattern, not only the mist particle size or droplet size. Also, the pressure from your garden sprayer has little to do with the pressure from the injector - your garden sprayer is about 30 to 50 psi. An injector is around or exceeds 1000psi - in fact it can inject liquid into your bloodstream and can kill you. $\endgroup$
    – Solar Mike
    Commented Jan 23, 2023 at 17:25
  • $\begingroup$ Yes, of course. But the less atomized the fuel could lead to misfire for diesel engine as the pressure inside the combustion chamber is not enough to create heat to burn that diesel fuel. In gasoline case, the less atomized the fuel make less force as not all the fuel is burnt during the explossion. $\endgroup$ Commented Jan 24, 2023 at 16:09
  • $\begingroup$ From my understanding and from my observation, pressure we apply is very related to the nozzle size and the type of liquid we use. For the same spray tube, the atomization level will be different for diesel, gasoline, fresh water, and other liquid substance like we use with our parfume. $\endgroup$ Commented Jan 24, 2023 at 16:12
  • $\begingroup$ So check out water sprayed at 1500bar or 3000bar... $\endgroup$
    – Solar Mike
    Commented Jan 24, 2023 at 16:27

1 Answer 1


The degree of atomization is assessed by measuring the droplet size distribution and plotting the result as a histogram. The size distribution is measured by scattering light off the cloud of spray, capturing the scattered light, and then applying a generous amount of math magic to it.

You may find that the American Society for Testing and Materials (ASTM) has published a standard methodology for measuring the degree of atomization in a sprayed jet, that serves as an industry standard.

  • $\begingroup$ So, are you saying that the atomization level is not yet well quantified? Quantify means, there is measurement and formulation to get and to count it. In my mind, the atomization level are affected by pressure, viscosity, type of the liquid, and the size of the nozzle. So, what I expect is how to calculate, such as if I apply a certain pressure p to a liquid with viscosity u with the nozzle size a, I will get that atomization level I want without performing such measurement you mentioned. By so, I can design a fuel injector and other various spray. $\endgroup$ Commented Jan 24, 2023 at 16:05
  • $\begingroup$ Creating a certain droplet distribution, and quantifying the results are two totally different tasks. Niels is describing the latter. There are many ways to produce mist. $\endgroup$
    – Drew
    Commented Jan 24, 2023 at 18:37
  • $\begingroup$ If you want to analytically design a nozzle for a certain mist characteristic, you must first be able to define what that characteristic is. $\endgroup$
    – Drew
    Commented Jan 24, 2023 at 18:38
  • $\begingroup$ @Drew, as I learn from many sources that the more atomized the fuel the better for combustion. So, how to get the expected atomization, say, like in the 1st picture? As general, how to get a certain atomization level for certain liquid? I knw that different liquid sprayed from the same container with the same pressure will have different atomization level. To estimate the output, I need to know to have a formula that compile all parameters. $\endgroup$ Commented Jan 24, 2023 at 19:07

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