Opposed Nozzles

Opposed Jet Mills. These mills are, in some ways, similar to the fluidized-bed machine however, in this case two opposed nozzles accelerate particles, causing them to collide at a central point (Fig. 16). A turbine classifier is again used to separate the product that has achieved the desired fineness from that which must be internally recycled for further grinding. 

SAXON A tubular hrework containing a pair of opposing nozzles that is designed to rotate by virtue of a central pivot. 

TOURBiLLioNS Fircworks designed to revolve on the ground and then ascend. They consist of tubes with opposing nozzles and small wings. They used to be known as aeroplanes in the UK during the 1950s. 

Fig. 17.6 Illustration of an opposed-nozzle diffusion-flame configuration.

Fig. 17.8 Schematic of an opposed-nozzle configuration, leading to twin, strained, premixed flames.

In the lower part of the gasifier, CWS is injected with 02 via two opposed nozzles. The reaction temperature in this first stage is normally 1350-1400 °C and the pressure is about 3 MPa. The molten slag runs down the gasifier and is discharged... 

Stagnation Large strain centre but non-homogeneous Birefringence Opposed nozzles low i] convenience of a wide range of e Wall effects (e.g. shear) Lubricant Stability of flow... 

Fig. 6.4-9 Forced agglomeration by ihe interaction of two atomized clouds of droplets from opposing nozzles [6.4.1.1]...

Some of the basic conclusions of the simulation work are summarized as follows Residence time of particles in the ISD decreases with increasing Reynolds number of the jet (stream) but increases with spacing between the opposing nozzles. Particles entering closer to the jet mid-plane tend to have... 

There is another technique that can be used with low viscosity (100 mPa s) nonspinnable fluids and which allows high strain rates (>10 s ). A modified opposing jets device (253) is employed that consists of opposing nozzles through which the fluid is sucked or blown out. Extensional viscosity is determined from... 

Fuller and co-workers (1987 Mikkelsen et al., 1988) have attempted to make the opposed-nozzle device more quantitative by measuring the torque on the arm that holds the nozzle down into the beaker. Torque is detected by a rebalance transducer that maintains the gap constant. 

Opposed-nozzle (or jet) device creates a uniaxial ex-tensional flow by sucking in surrounding fluid. Flow creates a force that tends to pull the nozzles together and is measured by the torque on one of the flow tubes. 

Measured extensional viscosities versus rate for glycerin-water compared to predictions from flow of a Newtonian liquid between opposed nozzles. The upturn in the expulsion data is due to secondary flows as the Reynolds number exceeds 1. Adapted from Schunk et al. (1990). 

In the low viscosity range, the opposed-nozzle device seems most attractive. Like entrance pressure drop, it is an indexer, but the flow from opposed nozzles is more nearly extensional. 

Schematic of opposed-nozzle extensional rheometer. Stepper motor A moves a pair of syringes B, which suck (or blow) the test liquid from the beaker C through a matched pair of nozzles D. Screw E can translate arm F to change the gap between the nozzles. Arm G pivots around the inlet tube at H. Torque on the tube is measured by a rebalance transducer /. From Rheometrics (1991).

The other important commercial design for extensional measurements on low viscosity fluids is the opposed nozzle device shown in Figure 8.5.2 (Fuller et al., 1987 Mikkelsen et al., 1988). In addition to the opposed-nozzle configuration, if the arm G is turned 90°, the device can also be operated as fiber spinning and tubeless siphon rheometers (Cai et al., 1992). 

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