Injection velocity

Ultrasound. Liquid is fed over a surface vibrating at a frequency > 20 kHz. Fine atomization, small size, and low injection velocity. Low flow rate and need for ultrasound generator. 

Simulations are then performed for gas bubbles emerging from a single nozzle with 0.4 cm I.D. at an average nozzle velocity of lOcm/s. The experimental measurements of inlet gas injection velocity in the nozzle using an FMA3306 gas flow meter reveals an inlet velocity fluctuation of 3-15% of the mean inlet velocity. A fluctuation of 10% is imposed on the gas velocity for the nozzle to represent the fluctuating nature of the inlet gas velocities. The initial velocity of the liquid is set as zero. An inflow condition and an outflow condition are assumed for the bottom wall and the top walls, respectively, with the free-slip boundary condition for the side walls. 

Figure 5.4 Schematic of the geometrical configuration for hydrogen-air flame and sofid fuel. The geometry corresponds to the experimental setup. The initial shape of the HED fuel was a circular arc segment as shown above. The relevant material properties air density = 1.91 kg/m , hydrogen density = 0.0898 kg/m . For the turbulent quantities at the inlet k = (O.OSf/miet) = 9.59 (m/s), = C fc / /(0.03Liniet) = 6360 m /s , jjkt = Cfe = 0.00248 kg/ms. For the fuel sample, m.p. is 450 K, latent heat of fusion is 72.7 J/g. Dimensions in mm. Air inlet velocity 103.3 m/s, hydrogen injection velocity 800 m/s...

The reinforcement can be displaced significantly by fluid forces if the injection velocity is too high or equivalently if the injection pressure is too high compared with the friction forces... 

Consider the isothermal, incompressible, viscous flow between two closely spaced parallel plates that are separated by a height H (Fig. 5.13). There is a uniform injection velocity V from the lower boundary and a uniform exit velocity V0 from the upper plate. Flow enters the channel from the left with a mean velocity U. The net injection velocity is given as... 

Fig. 5.13 Flow between parallel plates with a uniform injection velocities through the plates.

Overall the system of equations (continuity and momentum) is third order, nonlinear, ordinary-differential equation, boundary-value problem. The boundary conditions require no-slip at the plates and specified wall-injection velocities,... 

Fig. 5.15 Relationship between the nondimensional injection velocity and nondimensional pressure gradient for the case where both the lower-wall and upper-wall velocities are equal at V.

Figure 5.14 illustrates the nondimensional velocity profiles (Eq. 5.122) for different values of the cross-stream velocity V. As should be anticipated, for sufficiently low injection velocity V, the parabolic Poiseuille profile is obtained. As the injection velocity increases, the axial velocity profile is skewed toward the upper wall. 

The parameter K represents the nondimensional axial pressure gradient (Eq. 5.120), and Eq. 5.125 provides the relationship between the pressure gradient and the wall-injection velocity V. As seen from Fig. 5.15, which graphs Eq. 5.125, the pressure gradient increases nonlinearly as the wall injection increases relative to the mean axial velocity U. In the limit of low Rev, K becomes constant at K = 12. In the limit ofhigh Rey, K — 2Rey. 

Consider a situation where there is no flow through the upper wall and the lower-wall injection velocity is Vi = V (AV = V). Under these circumstances the system can be summarized as... 

Figure 5.17 illustrates the nondimensional axial (i.e., u) and cross-channel velocity (i.e., 0) profiles for several values of Rev- It is apparent that increasing the injection velocity (Reynolds number) from below skews the velocity profile toward the upper wall of the... 

The flow at high Rep approaches the planar, finite-gap, stagnation flow between parallel plates. In this case, the injection velocity V dominates over the initial velocity U that enters the channel. The system of equations developed here are essentially the same as those for finite-gap planar stagnation flow. Indeed, it is only the relationship between K and the axial pressure gradient that distinguishes the two flows. 

J5 Consider the wall-injection problem in an axisymmetric setting, where a uniform injection velocity flows through the wall of a cylindrical tube. There is a mean velocity U that enters through one end of the tube. Following a procedure analogous to the flow-between-plates problem (Section 5.6), develop a solution for the velocity profiles and the wall shear stress as characterized by the product of a Reynolds number and a friction factor. 

The technical term for this is hydrodynamic focusing, flow of a sample stream within the center core of a sheath stream is called coaxial flow. The exact diameter of that central sample core within the sheath stream is related to, among other things, the rate at which the sample is injected into the sheath stream a 100 pm sheath stream may, depending on sample injection velocity, have a core width of perhaps 5-20 pm (Fig. 3.4). Because hydrodynamic focusing tends to confine the cell sample to this central core, there is little mixing of sample with sheath fluid (but diffusion of small molecules will occur). The reason that this type of coaxial sample flow suits flow cytometry... 

MPX functionality is arranged into three modules, the first of which is the Setup Xpert, a module that allows users to perform a variety of injection-velocity- and pressure-phase-related setup routines to fix certain defects, such as short shots, flash, burn marks, sink marks, etc. The objective of Setup Xpert is to achieve one good molded part with no defects. The basic process is that a user molds a part, then provides feedback to the MPX system regarding molded part quality. The MPX system then processes this feedback along with data being collected from the machine and (if necessary) determines a process change that will improve the result. 

In creating a process window for the combination of material, machine and heater used in this study, the first consideration was the moldability, which was dictated by the maximum injection pressure and the maximum clamp force. No changes in melt and mold temperature, injection velocity, or gate size could remedy this situation. Thus, an injection molding machine with higher injection speeds, pressures and clamp force was required to mold thin-walled syndiotactic polystyrene. 

Figure 10.1. Normal, radial and tangential injection velocity profiles for the burner configuration r = t/Rq and u = u/Uq where i o and Uq are respectively the SI radius and the bulk velocity.

Fine atomization, small size, and low injection velocity. 

It was noted by both groups that when a sufficiently high injection velocity was reached, the nonwetting continuous paths broke up and a new slug flow mechanism developed. This phenomenon was attributed to the extremely high flow rates involved and not investigated further. 

FIGURE 11.4. Profiles of droplet velocity, gas velocity, and droplet radius in a rocket motor with the drag parameter P2 = 1 l e dimensionless injection velocity =0.5... 

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