Mixed-flow machines

Engineers quickly recognized that turbines could be arranged iu a variety of ways. For example, water could be fed to the wheel internally (as Fourneyron s machine did), externally, axially, or by a combination. Between 1830 and 1850 a host of European and American engineers experimented with almost every conceivable arrangement. The turbines that resulted— the most popular being the mixed-flow Francis turbine—quickly demonstrated their superiority to traditional vertical wheels in most respects. Turbines were... 

If the constant speed characteristic of a pump is superimposed on a system curve, there is usually one intersection point, shown in Figure 32.39. If a flat system curve is being matched with a mixed or axial flow machine there can be flow instability, as illustrated in Figure 32.40, which is only corrected by changing pump speed or the static lift, or selecting a different pump. 

Fiqure 4.2 (a) Continuous-flow machine with 45-ps dead time, (b) Exploded view of the mixing chamber. Turbulent flow of the two liquids over the platinum sphere gives improved mixing. [Courtesy of M. C. Ramachrandra Shastry and H. Roder.]... 

Figure 4 A schematic representation of the experimentai approach for time-resoived XAS measurements. XAS provides local structural and electronic information about the nearest coordination environment surrounding the catalytic metal ion within the active site of a metalloprotein in solution. Spectral analysis of the various spectral regions yields complementary electronic and structural information, which allows the determination of the oxidation state of the X-ray absorbing metal atom and precise determination of distances between the absorbing metal atom and the protein atoms that surround it. Time-dependent XAS provides insight into the lifetimes and local atomic structures of metal-protein complexes during enzymatic reactions on millisecond to minute time scales, (a) The drawing describes a conventional stopped-flow machine that is used to rapidly mix the reaction components (e.g., enzyme and substrate) and derive kinetic traces as shown in (b). (b) The enzymatic reaction is studied by pre-steady-state kinetic analysis to dissect out the time frame of individual kinetic phases, (c) The stopped-flow apparatus is equipped with a freeze-quench device. Sample aliquots are collected after mixing and rapidly froze into X-ray sample holders by the freeze-quench device, (d) Frozen samples are subjected to X-ray data collection and analysis.

For the near ambient pressure cathode air blower application, the best machine is clearly a mixed flow... 

Quadronics (L,iquid Dynamics) Extractor (Doyle et al., U.S. Patent 3,114,707, 1963, and others paper at AlChE meeting, St. Louis, February 1968) This is a horizontally rotated device, a variant of the Podbielniak extractor, in which either fixed or adjustable orifices may be inserted as a package radially. These permit control of the mixing intensity as the liquids pass radially through the extractor. Flow capacities, depending on machine size, range from 0.34 to 340 mVh (1.5 to 1500 gal/min). 

A Uniroyal patent originated the principle of using pins protruding into the extruder barrel to disrupt the laminar flow of compound, and this principle was further developed by Troester in their QSM (cross-flow mixing) machines. The protrusion of pins into the barrel necessitated a modification to the screw design to accommodate them. Many papers can be found in the literature dealing with this type of pin extruder. 

A vertically arranged rotor system consisting of protruding arms revolves within a cylindrical chamber fitted with stationary deflector protrusions. The combination of the movable rotor and static protrusions effectively mix the diced rubber feed and solvent by turbulent flow. It is usual to have at least three speed possibilities and thus lump-free preparation of the product is possible in relatively short mixing times. Mixing times for these machines is considerably less than for the Z-blade mixer. 

In order to use the stopped-flow technique, the reaction under study must have a convenient absorbance or fluorescence that can be measured spectrophotometri-cally. Another method, called rapid quench or quench-flow, operates for enzymatic systems having no component (reactant or product) that can be spectrally monitored in real time. The quench-flow is a very finely tuned, computer-controlled machine that is designed to mix enzyme and reactants very rapidly to start the enzymatic reaction, and then quench it after a defined time. The time course of the reaction can then be analyzed by electrophoretic methods. The reaction time currently ranges from about 5 ms to several seconds. 

---