Axial compressors rotors

Figure 4-15. Axial compressor with fixed stator blades, double-casing design, and forged monoblock rotor. Particularly suitable for compressing nitrous gases. There are no dead spaces provoking buildup of ammonium nitrate salt.

Figure 4-16. Axial compressor with adjustable stator blades, either partially or on all stages. Double-casing design and forged monoblock rotor. This design offers a wide operating range especially in combination with speed control.

The degree of reaction, R, in the axial compressor is defined as the ratio of the static differential pressure in the rotor to the static differential pressure developed across the stage. 

An alternate method not used too much at this time is the drum design. The drum construction is somewhat different from the disc, in that the rotor body is of cylindrical construction. By using the hollow drum, conical roots, of bolted construction, can be used for the rotor, again, allowing for stagger adjustments to fine tune the axial compressor to the application if the need arises. The setting is done to a gauge at the factory, as with the stators. 

Axial compressor blades are usually forged and milled. Precision casting has been used on occasion. The most common material used is a 12 chrome steel, in the AISI 400 series, and is also known as 400 series stainless steel. While the stator blades are occasionally shrouded, the rotor blades are free-standing. Lashing wires have been used on rotor blades, but are generally used to solve a blade vibrational stress problem. 

This definition of efficiency does not consider the work done on the shaft driving the compressor. To bring this in we should also consider the mechanical efficiency which takes into account the friction in the bearings, or between the rotors and the outer casing (if any). In the case of centrifugal and axial compressors, this is very high, almost certainly over 98%. We can then say that... 

For a dynamic compressor, a continuous totfUtng element (rotor) js used to increase gas velocity. Then, gas velocity is converted to static pressure at compressor outlet. Dynamic compressor is classified as centrifugal or axial compressor. For centrifugal compressor, the rotating element is an impeller, and gas flow is in either radial or mixed flow direction. For axial compressor, the rotating element is a bladed rotor and gas flow is in the axial directioa... 

Compression ratio generated at each rotor or stator section is low. Therefore, a lot more rotor and tat sections arc required to achieve a compression ratio. Due to the low overall compression ratio, interstage cooling is usually not required for an axial compressor. 

Fig. 5.30. Step-by-step view of the compression process within a screw compressor. Shaded portion represents one volume of gas as it passes through the compressor (diagram courtesy of Sullair). (a) Refrigerant is drawn axially into the compressor rotors as they turn past the intake port in the housing, (b) The rotors have now turned past the intake port gas is trapped in the compressor housing and rotor cavities. (c)As the rotors continue to turn, the lobes reduce the volume in the cavities to compress the trapped gas. (d)The process is completed as the compressed gas is discharged through the discharge port...

As the rotors are drawn past the intake port, gas is axially drawn into the compressor rotors (see Fig. 5.30a). As the rotor blades turn past the intake port, the gas becomes trapped, as in Fig. 5.30b. As the rotors push the gas forward, the cavities in which the gas is trapped become smaller (see Fig. 5.30c). Compressed gas is then discharged into the exit port after the process is completed. 

The parameters of rotating machinery needed for the SOFC-GT can be achieved by a single-stage radial compressor and a two-stage axial turbine. A similar construction with very similar parameters is presented in Fig. 5.75 an exemplary compressor rotor is shown in Fig. 5.76. 

Many users consider rotaiy compressors, such as the Rootes -type blower, as turbomachines because their behavior in terms of the rotor dynamics is very close to centrifugal and axial flow machineiy. Unhke the reciprocating machines, the rotary machines do not have a veiy high vibration problem but, like the reciprocating machines, they are positive displacement machines. 

Screw-Type This type of rotary compressor, as shown in Fig. 10-80, is capable of hancmng capacities up to about 4.248 X lO" m m (25,000 fF/min) at pressure ratios of 4 1 and higher. Relatively small-diameter rotors allow rotative speeds of several thousand rev/min. Unhke the straight-lobe rotary machine, it has male and female rotors whose rotation causes the axial progression of successive sealed cavities. These machines are staged with intercoolers when such an... 

Axial-Flow Compressors. An axial-flow eompressor eompresses its working fluid by first aeeelerating the fluid and then diffusing it to obtain a pressure inerease. The fluid is aeeelerated by a row of rotating airfoils or blades (the rotor) and diffused by a row of stationary blades (the stator). The... 

Figure 1-20 shows multistage high-pressure axial flow turbine rotor. The turbine rotor depicted in this figure has a low-pressure compressor followed by a high-pressure compressor. There are also two turbine sections, and the... 

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