Turbine blades materials

In [655] measurements of the concentration profiles were presented which were measured in a vessel with contoured bottom (see Fig. 5.18a) and a 45°-pitched-blade turbine. Material system glass beads in water. 

A design is only as effieient as the performanee of the seleeted eomponent materials. The eombustor liner and turbine blades are the most eritieal eomponents in existing high-performanee, long-life gas turbines. The extreme eonditions of stress, temperature, and eorrosion make the gas turbine blade a materials ehallenge. Other turbine eomponents present operational problem areas, but to a lesser degree. For this reason, gas turbine blade metallurgy will be diseussed for solutions to problem areas. Definition of potential solutions will also relate to other turbine eomponents. 

Figure 5-5G. Curved-blade turbine, devei-oped especlaily for agitating fibrous materials such as paper stock. Also used on oil well drilling muds. This impeller gives fast, thorough turnover without need for the usual tank baffling or mid-feather construction. Courtesy of Lightnin (formerly Mixing Equipment Co.), a unit of General Signal.

Figure 5-5T. Standard six-blade vertical curved blade turbine impeller. Gives good efficiency per unit of horsepower for suspensions, mixing fibrous materials. Gives high pumping capacity. Courtesy of Philadelphia Gear Corp.

Figure 5-5S. Four-blade, vertical Figure 5-5T. Standard six-blade fiat blade turbine Impeller. Very vertical curved blade turbine versatile, one of the most used impeller. Gives good efficiency in wide application range. Cour- per unit of horsepower for sus-tesy of Philadelphia Gear Corp. pensions, mixing fibrous materials. Gives high pumping capacity. Courtesy of Philadelphia Gear Corp.

Once the emulsifier is well blended into the carbohydrate melt, the flavoring material is added. An emulsion is formed using a flat bladed turbine type agitator (about 4i inches in diameter). The time of agitation is typically about 5 min. The next step involves pressurization of the extrusion vessel with either nitrogen or carbon dioxide. While others have mentioned pressurization of the vessel for extrusion, Miller and Mutka (8) have optimized this parameter for encapsulation efficiency, they found 7-50 psi most suitable for improving encapsulation efficiency. At pressures above 100 psi, they found some emulsions broke and encapsulation efficiency was very poor. 

Many types of multishaft mixers do not require planetary motion. Instead the mixers rely on an anchor-style impeller to move and shear material near the tank wall, while another mixer provides a different type of mixing. The second or third mixer shafts may have a pitched-blade turbine, hydrofoil impeller, high-shear blade, rotor-stator mixer, or other type of mixer. The combination of multiple impeller types adds to the flexibility of the total mixer. Many batch processes involve different types of mixing over a range of viscosities. Some mixer types provide the top-to-bottom motion that is missing from the anchor impeller alone. 

It is to be expected that this lowest stirrer speed Wniin is dependent upon the material system and the stirrer type. Van Heuren and Beck [202] established for the 6-blade turbine stirrer that ... 

Fig. 6.1 Volume density distribution <73 (dp) as a function of dp for the 6-blade turbine stirrer at four different stirrer speeds in the material system trichloroethene/water (y> = 0.2) from [166]... 

Kipke [276] investigated the effect of different stirrer types and their d/D ratios on the droplet size and its distribution. This study utilized the already mentioned coalescence-prone camauba wax/water system (type 2442 p = 825 kg/m, pj = 2 mPa s at 95°C). The wax/water dispersion could be frozen in with ice water and the droplet size distribution determined by sieving. The stirrer types investigated were 2-stage Intermig d/D — 0.5 0.6 0.7) propeller stirrer (d/D = 0.31 0.37) pitched-blade turbine d/D = 0.31) 6-blade turbine stirrer, Pfaudler impeller stirrer (d/D = 0.575). The experimental data are presented in Fig. 6.7. It is evident that in this material system the droplet size distribution extended to dp/d32 = 0.4-1.5. 

The above-discussed particle size distributions are shown, for the sake of comparison, as logarithmic normal distributions in Fig. 6.8 for the 6-blade turbine stirrer and different material systems. It emerges, that, with the exception of car-nauba wax, all organic liquids in the range investigated behaved similarly in this... 

A pilot-plant reactor, a scale model of a production unit, is of such size that 1 g charged to the pilot-plant reactor is equivalent to 500 g of the same material charged to the production unit The production unit is 2 m in diameter and 2 m deep and contains a six-blade turbine agitator 0,6 m in diameter. The optimum agitator speed in the pilot-plant reactor is found by experiment to be 330 r/min. a) What are the significant dimensions of the pilot-plant reactor (b) If the reaction mass has the properties of water at 70°C and the power input per unit volume is to be constant, at what speed should the impeller turn in the large reactor (c) At what speed should... 

Flat-blade turbines pump liquid outward by centrifugal force. Liquirl that is di.splaced by the blade is replacerl by flow from the top and bottom. Suction comes from the center, and delivery is on the circumference of the blade. The primaiy flow is radial. This is the most widely used type of mechanical agitator. The number of blades vary from 4 to 12. This turbine is used primarily for liquid—liquid dispersion, Turbines with curved blades are used for higher-viscosity materials. 

A major application of superalloys is in turbine materials and jet engines, both disc and blades. Initial disc alloys were Inco 718 and Inco 901, produced by conventional casting ingot, forged billet, and forged disc route. These alloys were developed from austenitic steels, which are still used in industrial turbines, but were later replaced by Waspaloy and Astroloy as stress and temperature requirements increased. These alloys were turbine blade alloys with a snitably modified heat... 

For the repair of wind turbine blades, Gurit has developed the prepreg SPRINT , SparPreg , which requires no de-bulking. They have also developed the RENUVO blade-repair system for the repair and maintenance of wind turbine blades. SparPreg material is said to provide the following benefits in spar manufacture ... 

Figure 10.1 illustrates a typical section of fibre lay-up through a Gurit manufactured wind turbine blade. Further information on the manufacture of turbine blades, the materials used, their description and properties may be obtained from the Gurit Handbook - Materials for Wind Turbine Blades. 

Figure 5-19 shows an example of the dispersion of a chemical tracer in a stirred tank. A standard pitched blade turbine is used to mix two waterlike materials. The neutrally buoyant tracer is injected at time zero as a blob above the impeller, as shown on the top left in the figure. The flow field is calculated using the sliding mesh and LES models, and the dispersion of the tracer is derived from the flow field. The blob is stretched and the chemical is mixed with the rest of the fluid over time. It is interesting to see that despite the fact that there are four impeller blades and four baffles, the concentration field is not symmetric because of the off-axis injection. The consequence is that the full tank needs to be modeled instead of a 90° section. Bakker and Fasano (1993b) presented a successful comparison between blend time predicted by CFD and calculated from experimental correlations. 

The Rushton turbine is constructed with six vertical blades on the disk. Standard relative dimensions consist of blade length of D/4, blade width of D/5, and the disk diameters of 0.66 and 0.75D. The backswept turbine has six curved blades with a power number 20% lower than the Rushton turbine. The backswept nature of the blades prevents material buildup on the blades. It is also less susceptible to erosion. Typical applications include general waste and fiber processing in pulp and paper industries. 

---