Blade design

Types and Characteristics. The four basic fan wheel and blade designs and the corresponding performance curves are illustrated in Figure. 

Most rotating equipment includes electric motors or steam dryers that generate noise at a constant frequency. Air cooler fans are a source of noise that can be reduced by lowering the fan speed and increasing the number of blades. Pump motor noise can be reduced by including a shroud or fan cover that is accurately lined. Centrifugal compressor noise reduction can be achieved by blade design and the use of compressor pulsation noise reduction, silencers, and vibration isolation. 

Many other blade designs have been developed for specific applications. The double-naben blade (Fig. 18-41 is a good blade for mixes which ride, that is, form a lump which bridges across the sigma blade. 

The incorporation of the above blade cooling concepts into actual blade designs is very important. The most frequently used blade cooling designs are ... 

An expander-eompressor unit must be meehanieally tested and all meehanieal tests should be witnessed by the owner-purehaser or his representative. If the manufaeturer does not have the eapability of testing with the fully bladed eontraet rotor, a dummy wheel may replaee the eompressor impeller. This dummy wheel is a disk with no blades, designed to duplieate the weight, eenter of gravity, and moment of inertia of the aetual eompressor wheel. 

The expander design will be of axial entry (Figure 5-14), overhung rotor, stiff shaft construction with one or two rows of blading designed and constructed for 100,000 hrs of life and at least 3 yrs of uninterrupted continuous service. It is recognized that uninterrupted operation for this period of time involves factors beyond the Seller s control. 

Veloeity triangles at the mean seetion of the blading are to be submitted by the Seller. The blading shall be designed to minimize blade erosion eaused by tlie partieulate entrained in the flue gas witli tapered and twisted rotor and stator airfoils. The blade design used shall have at least tliree years of sueeess-ful operating time in FCC serviee for tlie frame proposed. 

This type of blade design is shown in Figure 9-16. The midchord region is convection-cooled, and the leading edges are both convection and film-cooled. The cooling air is injected through the blade base into two central... 

Provides more flow and less shear than the four bladed design. 

Figure 12-119D. Centrifugal blade design for backward, radiai, and forward tips. (Used by permission Fan Engineering, 8 Ed., 1983. Buffaio Forge Co., Howden Fan Co. Aii rights reserved.)...

This type of blade is well suited to streamline flow conditions and is used extensively on ventilating, air conditioning, and clean and dirty process gas streams. The backward blade does not catch dirt easily. The outstanding and important characteristic is the nonoverloading horsepower. This is the only commonly used blade style with this feature. It is important in process control and eliminates the need for oversized motors or other drivers. Speed of operation is high, which allows direct or belt connection to the driver. Certain streamlined blade designs provide the same basic characteristics with more efficient and quieter operation. The usual... 

Bott, T.R. and Sheikh, M.R. Brit. Chem. Eng. 9 (1964) 229. Effects of blade design in scraped-surface heat transfer. 

As with any source of energy, there are some drawbacks to wind power.The most significant is that the wind to drive the turbines may be intermittent and that it does not always blow when electricity is needed. Wind energy may only be available 40 percent of the year in some areas versus 90 percent for a fossil-fuel powered plant. New blade design can overcome this problem to a certain extent, as can storing the energy in batteries, but because of these potential drawbacks, the site of the wind farm is key to its success and vice versa. 

Cp is the aerodynamic efficiency factor. It is a function of the rotor blades design and angle as well as the relative speed of the rotor and wind (known as the tip speed ratio)... 

---