Momentum ratio

The average experimental value of the coefficient 0 is 1.7 with a standard deviation (og) of 0.05. Equation (7.160) allows one to calculate the momentum ratio (/rj2/foi) required to extend the length of zone I to the value equal to Xj, given that the distance between the directing nozzles is equal to The graph presented in Fig. 7.56 is plotted according to Eq. (7.160) for and X,2 equal to 6.2. The maximum value of reverse flow velocity (n,, .) was found to be in the cross-section at X equal to Xy... 

The flow becomes fully three-dimensional, i.e., the flow becomes unstable, when the momentum ratio is too large. This is typically when / s 0.6 ... 

In addition to the momentum ratio I, numerous other geometrical aspect ratios should be investigated. 

It should be noted that when additive flow has significant momentum, much more rapid blending is possible (so-called T mixer). An optimum value of momentum ratio between main flow and additive can be found (see Ref. 2 for details). 

The momentum ratio is very important in determining the type of atomization that will occur [13]. This is shown in Fig. 24.14. Three situations are exemplified, and as can be seen, the size of the droplets varies considerably when the momentum ratio is changed. Both front and side views are shown in the figure for all three cases. 

This equation can also be written in terms of the gas to liquid momentum ratio qOh >lQ, where... 

Keywords Momentum ratio Pintle nozzle Rocket injector... 

Figure 28.3 highlights some of the major design features of a pintle injector. The most important design variable is the total momentum ratio (TMR), defined as the ratio of radial-to-axial stream momenrnm... 

One can also find a functional form for the trajectory of the large droplets that are formed at the CBL. The path of these droplets represents the maximum spray penetration. Since they are not connected to the jet and are in direct contact with a strong gas flow, they do not necessarily follow a path of the form of (29.9) anymore. A schematic view of the trajectory of these drops is shown in Fig. 29. Ic with a local coordinate system attached to the CBL for convenience. In general most applications of LJICF are concerned with high momentum ratios for which the jet deflection is not pronounced. For those cases, it is fair to assume that the droplets formed at the CBL have a zero initial velocity in the x-direction as they separate fi om the jet and have an initial upward velocity of mj. As these droplets leave the jet, they lose their vertical velocity and speed up in the gas-streamwise direction and finally reach their terminal x-direction velocity. Of course, all these are true for one droplet without considering its interaction with other droplets and also with neglecting the effects of evaporation. With these assumptions, the equations governing the motion of the drop take the form... 

Fig. 29.5 (a) Calculated trajectories for various cases in comparison with the experiments ofWu et al. [1] (b) effect of Weber number on the trajectory at a constant momentum ratio. The experimental data of Wu et al. [1] for We = 160 are plotted for comparison (Pictures from Mashayek et al. [6]. Reprinted with permission of the American Institute of Aeronautics and Astronautics)... 

Momentum ratio Sheet thickness Sheet breakup length... 

The maximum value of O occurs near M1/M2 = 1, and that the liquid-phase mixing is relatively insensitive to momentum ratio at or near a momentum ratio of 1.0 [9, 46]. 

The spray mechanism can be best remembered by hjuyd, the momentum ratio of liquid and vapor. Spray factor is defined in equation (12.6) based on Lockett (1986) with the value of 2.78 as the spray limit. To avoid spray, one needs to increase weir loading, reducing vapor loading and/or hole diameter. 

---