Vane angle

A positive vane angle produees prewhirl in the direetion of the impeller rotation, and a negative vane angle produees prewhirl in the opposite direetion. The disadvantage of positive prewhirl is that a positive inlet whirl veloeity reduees the energy transfer. Sinee Vg is positive aeeording to the Euler equation defined by... 

Figure 5-24. Vector tip triangle without slip, showing the effect of different exit vane angles.

Vane angle, 152 Vapor, 15, 17, 20 Vector triangle, centrifugal, 151, 153... 

It is apparent, therefore, that the required vane angle in the diffuser is dependent on the throughput, the speed of rotation, and the angle of the impeller blades. The pump will therefore operate at maximum efficiency only over a narrow range of conditions,... 

Two compressors are similar when they have the same compressor constant. In similar compressors all impeller and discharge-vane linear dimensions are in the same ratio as their impeller diameters, while their impeller and discharge vane angles are respectively equal. For the same revolutions per minute the quantities delivered by sinailar compressors will vary as the cubes of their diameters the pressures will vary as the squares of their diameters, and the shaft powers will vary as the fifth powers of their diameters. For the same wheel speed the quantity and the power will vary as the square of the diameter, while the pressure will remain constant. 

The different swirlers in the table are labeled by the different vane angles of inner, intermediate, and outer air passages. The flow was ducted through the TARS nozzle and exited to ambient atmosphere. The outlet of the TARS was located at the inlet dump plane of the combustion chamber. This location was defined as z/ii = 0, where R is the radius of the TARS outlet. 

The effect of swirl distribution in the burner on droplet size and velocity distribution, flow, and flame characteristics is reported. Three examined swirl distributions are 50°/30 , 50 /—30°, and 65°/30 , where the first number indicates the swirl vane angle of the inner annulus and the second number refers to that at the outer annulus. Three airflow distributions of 25%/75%, 50%/50%, and 75%/25% were examined for each swirl distribution. The first percentage number indicates the fraction of the total combustion airflow through the inner annulus, while the second number refers to that at the outer annulus. The results presented here are for swirl distributions of 65 /30° and 50 /30° only, where the total airflow was held constant to maintain a fixed equivalence ratio of 0.4. 

LOSS OF HEAD CIRCULATORY FLOW. A basic assumption in the theory of the ideal pump was that of complete guidance, so the angle between vectors and M2 equals the vane angle 2- Th guidance is not perfect in the real pump, and the actual stream of fluid leaves at an angle considerably less than /Jj- The physical reason is that the velocity in a given cross section is far from uniform. The effect is the result of an end-to-end circulatory flow of liquid within the impeller channels superimposed on the net flow through the channel. Because of circulation, the... 

Kinetic-energy correction factor a , at station a a, at station b ttj,., at station b also angle between absolute and peripheral velocities in pump impeller oci, at suction aj, at discharge Vane angle in pump impeller at suction / 2, at discharge also ratio, diameter of orifice or venturi throat to diameter of pipe Ratio of specific heats, Cp/c ... 

The principle of these vanes is that they act like discs in a disc centrifuge separator. By virtue of the vane angle the effective settling distance for the solids is much reduced. 

We use the following notation Dov, Dm for the outer and inner diameter of the vane assembly, respectively Dmid for the geometric mean diameter of vane equals (DovDiv) / I for the horizontal separation between two adjacent vane elements / for the horizontal width of a vane element Ny for the number of vane elements (also equals number of vane openings) t for the vane thickness (3 for the vane angle relative to the horizontal and ay,hy for the length and... 

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