Thermocompressors Spindle operated

For spindle operated thermocompressors, shown in Figure 18-2(b), the nozzle design is quite different from that of fixed nozzle units. The nozzle and spindle assembly combines a rounded entrance orifice with a straight section into which a tapered spindle is guided. Operation is much like that of a needle valve. The length of the spindle travel is based upon the design requirements. 

Spindle operated units can be provided with either manually or automatically operated spindles. Thermocompressors with manually-operated spindles are designed for applications where loads will remain steady but where changes in operating conditions may occur and when operating conditions are not sufficiently established and some flexibility in nozzle orifice size is preferred.Thermocompressors with automatically-controlled spindles are used where pressure, suction, or discharge conditions vary and it is necessary to control discharge pressure or flow. 

A characteristic performance curve for a spindle-operated thermocompressor is shown in Figure 18-4. 

Figure 18-4 Characteristic performance curve of spindle operated thermocompressor.

Thermocompressors can be of two basic types fixed nozzle types or units with a reguiating spindle. Fixed-nozzle thermocompressors are more efficieni and are used when the thermocompressor can be operated under steady-loac conditions. Thermocompressors with regulating spindles are designed for use when performance approaches critical conditions and changes in suction loac and suction and discharge pressures are expected. 

Spindle regulated jets are usually not acceptable except for thermocompressors. A discussion of their application is given in Chapter 18. For critical vacuum pumps, regulating spindles are an ineffective means of control and can lead to unstable jet operation. 

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See also in sourсe #XX -- [ ]

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