Compressors axial

Axial compressor is used for large flow and low head application. Its capacity is about 75,000 to 600,0(X) adin and too psig discharge pressure. 

Like centrifugal compressor, axial compressor needs shafr seal to reduce the gas leakage. It uses balance drum to reduce the axial hydraulic imbalance and thrust bearing for the remaining axial imbalance. Journal bearings are used for the radial hydraulic imbalance. 

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. 

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Axeen Axerophthol Axial compressors Axial impeller Arad [76963-41-2]... 

Ail compressor anti-surge (ON - OFF) control circuit, comprising transmitters, computers and pneumatic blo-w-off control valve Reverse flow protection (on axial compressors only) as supplementary protection device against surging, v. orkmg indepenciently of the control ciicuit Blow-off. silencer Expander emergency stop valve with pneumatic actuator and solenoid valve... 

Above a minimum intake flowrate of about 50,000 m /hr and depending on the required discharge pressure, axial compressors (Figure 4-15) offer certain advantages. Their polytropic efficiencies. 

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.

Figure 4-25. Nitric acid plant at Fredericia (Denmark) with a four-machine turbogroup and generator. Power output to district heating system = 0-27 MW Power output to electric grid = 0-5.8 MW Steam turbine = 10.8 MW Axial compressor = 8.2 MW Centrifugal compressor = 4.1 MW Expander = 7.4 MW Nitric acid production = 650 t/d.

Figure 4-27. Ammonium nitrate salt deposits in the inlet of a nitrous gas axial compressor.

Caution should be taken to prevent excessive acceleration. One solution is to provide for opening of the compressor discharge vent valve to increase the compressor flow and increase blower horsepower. This is effective with a centrifugal compressor, however, not with an axial compressor unless the compressor is provided with adjustable stator vanes that are reliable. This can be seen from the performance curve. The head versus flow curve for a given vane setting is extremely steep and opening the vent valve is ineffective. However, if the vanes operate fully open and the vent valve opens, the combined effect is satisfactory. The vent valve must not be oversized. 

Noise control is worth mentioning. The turboexpander and axial compressors are noise producers and consideration must be given to the need for providing noise abatement. Silencers on vents and noise insulation housings on machines should be considered and have been proven effective. 

Figure 4-81. Axial compressor antisurge and guide vane control.

Any downtime of an expander results in significant lost revenue. When this particular damage occurred, the user no longer obtained power from the process to drive the equipment. Instead, the user was forced to buy electricity to drive the axial compressor. Depending on the power capability of the expander, losses of 300,000 per month or greater may be experienced. 

Centrifugal compressors in general are used for higher-pressure ratios and lower-flow rates compared to lower-stage pressure ratios and higher-flow rates in axial compressors. Figure 6-3 is a map for centrifugal compressors that shows the effect of specific speed (A ) and specific diameter (Z) ) on their... 

As with other types of rotating machinery, an axial compressor can be described by a cylindrical coordinate system. The Z axis is taken as running the length of the compressor shaft, the radius r is measured outward from the shaft, and the angle of rotation 6 is the angle turned by the blades in Figure 7-2. This coordinate system will be used throughout this discussion of axial-flow compressors. 

Figure 7-3 shows the pressure, velocity, and total enthalpy variation for flow through several stages of an axial compressor. As indicated in Figure 7-3,... 

Axial compressors are high speed, large volume compressors but are smaller and somewhat more efficient than comparable centrifugal com-... 

The volume range of the axial starts at approximately 30,000 cfm. One of the largest sizes built is 1,000,000 cfm, though this size is certainly not common. The common upper range is 300,000 cfm. The axial compressor, because of a low pressure rise per stage, is exclusively manufacturetl as a multistage machine. 

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