Reaction blading

Fig. P-76 guide blades (reaction member) (aerofoil shapes illustrated)...

FIG. P-76 Simplified schematic of the blading of a torque converter guide blades (reaction member). (Source J. M. Voith GmbH.)... 

Benzoylpropionitrile. To a mixture of 21 4 g. of p dimethylamino propiophenone hydrochloride, 13 0 g. of potassium cyanide in a 500 ml. flask, add 260 ml. of boiling water heat the heterogeneous mixture under reflux for 30 minutes. Part of the dimethylamine, which is eliminated in the reaction, distils collect this in dilute hydrochloric acid. Cool the reaction mixture in ice the oil sohdifies and crystals form from the aqueous layer. Collect the solid (crude p benzoylpropiouitrile, 10-5 g.) by suction filtration and recrystallise it from benzene - light petroleum (b.p. 40-60°) it separates as almost colourless blades, m.p. 76°. 

Purely aqueous polymerization systems give copolymers that are not wetted by the reaction medium. The products agglomerate and plug valves, nozzles, and tubing, and adhere to stirrer blades, thermocouples, or reactor walls. These problems do not occur in organic media or mixtures of these with water. 

A commercial design based on semicontinuous operation was developed for manufacture of silicate powders (27). A slurry, prepared containing the feed materials and water, is fed to the reactor tank and heated by circulating a heat-exchange fluid in channels located on the outside vessel wall. A six-bladed stirrer is operated at about 100 rpm in order to keep reagents well mixed. Once the slurry reaches the operating temperature, the vessel heat is maintained until reaction is complete. For most fine-particle products, this time is less than 1 hr. 

The polyesterification reaction is normally carried out in stainless steel vessels ranging from 8,000—20,000 L, heated and cooled through internal cods (Fig. 1). Blade agitators revolving at 70—200 rpm ate effective in stirring the low viscosity mobde reactants, which ate maintained under an inert atmosphere of nitrogen or carbon dioxide during the reaction at temperatures up to 240°C. 

Granules can be precipitated and formed by extmding the viscous reaction mixture through a circular die containing several holes over which a knife blade rotates to cut the strands into granules (91). The granules are simultaneously slurried in dilute acetic acid to harden the particles for further washing. 

Turboexpanders can be classified as either axial or radial. Axial flow expanders have either impulse or reaction type blades and are suitable... 

Because of the smaller blade angle the reaction stage is more efficient than the impulse stage, but it requires more stages for the same... 

An example of a typical turboexpander is shown in Fig. 29-46. Radial-flow turbines are normally single-stage and have combination impulse-reaction blades, and the rotor resembles a centrifugal-pump impeller. The gas is jetted tangentially into the outer periphery of the rotor and flows radially inward to the eye, from which the gas is jetted backward by the angle of the rotor blades so that it leaves the rotor without spin and flows axially away. 

The reaction turbine, shown schematically in Figure 2-2, is generally more efficient. In its primary (stationary) nozzles only half the pressure energy of the gas stream is converted to velocity. The rotor with a blade speed matching the full-jetted stream velocity receives this jetted gas stream. In the rotor blades the other half of the pressure energy is used to jet the gas backward out of the rotor and, hence, to exhaust. Because half the pressure drop is taken across the rotor, a seat must be created around the periphery of the rotor to contain this pressure. Also, the pressure difference across the rotor acts on the full rotor area and creates a large thrust load on the shaft. 

Figure 2-2. Steam turbine using reaction blading. (Source GHH-Borsig.)...

Depending on the operating conditions, the first few stages are of 50% reaction to obtain maximum capacity for the selected speed. In the downstream stages, where Mach numbers are lower due to the higher gas temperatures, 80% reaction blading is used to reduce the... 

The control of leakage loss across die blades in a reaction expander is extremely important. Maintaining adequate clearance implies preventing mechanical rubs while at die same time minimizing die loss effect on expander efficiency. 

The two types of turbines—axial-flow and radial-inflow turbines—can be divided further into impulse or reaction type units. Impulse turbines take their entire enthalpy drop through the nozzles, while the reaction turbine takes a partial drop through both the nozzles and the impeller blades. 

The 50% reaction turbine has been used widely and has special significance. The velocity diagram for a 50% reaction is symmetrical and, for the maximum utilization factor, the exit velocity (V4) must be axial. Figure 9-11 shows a velocity diagram of a 50% reaction turbine and the effect on the utilization factor. From the diagram IV = V4, the angles of both the stationary and rotating blades are identical. Therefore, for maximum utilization. 

The 50% reaction turbine has the highest efficiency of all the various types of turbines. Equation (9-15) shows the effect on efficiency is relatively small for a wide range of blade speed ratios (0.6-1.3). 

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