Based on the three combustion similarity rules for the single value condition

the existence of similarity was theoretically explored in spray mixture formation processes. The Bosch long tube method and high-speed shadowgraphy were employed to investigate the similarity of diesel injection rate and non-evaporating spray characteristics respectively with two different size diesel nozzles. The results show that the normalized spray penetration distance and injection rate can be well scaled for all the three rules

while the similarity rule that keeps the injection pressure constant is more preferable for scaling the spray angle. The other two similarity rules

which decrease the injection pressure

will result in smaller spray angle and lower excess air ratio.