The aerodynamic characteristics of centrifugal compressors are examined with special attention given to the range of flows normally in the unstable region. They are examined for the intended purpose of extending the compressor’s useful stable range. Two such means are investigated, but a close coupled aerodynamic resistance designed to achieve negative combined slope showed the greater promise. A number of experiments are performed in which the geometry and location of the close coupled control devices are varied. It is shown that with adequate design, stable operation is possible down to 40 percent of the normal surge flow. This can be done with hardware the configuration of which is practical and with attendant additional losses which are not prohibitive. The rationale and the empirical work are devoted to the single stage case but an examination is made of the stability considerations for the case of multi-stage machines.
A pump which operates by setting up a vortex in a chamber in front of the impeller is often called a vortex pump. Vortex pumps by virtue of this design have a large free and open flow passage which permits the pumping of solid materials without danger of obstruction. They are thus in common use as materials handling pumps. A one-dimensional analytical model of such a pump is created, handling a Newtonian single-phase fluid. Calculated performance parameters are compared with those measured on a laboratory model. Overall pump characteristics are also computed and compared to those of a number of test pumps of various geometries. Finally, an examination is made of the similitude parameters governing this style of pump.
While the operating characteristics of a compressor with a dual-entry impeller are similar to those of the more conventional single-entry machine, its stall behavior can have peculiarities of its own. These arise from the fact that the two impeller halves operate in parallel; each has inlet conditions that may occasionally be imperfectly matched. These conditions can result in instability. The necessity to eliminate these difficulties has stimulated considerable work at AiResearch Manufacturing Company of Arizona. As a result, the mechanism of the phenomenon has become well understood and brought well under control. The more fundamental aspects of this research are described herein.
A field investigation was made to determine the source and character of pressure pulsations in the boiler feed system of a central power station. By systematic equipment elimination, it was concluded that the oscillation are caused by rotating stall in the boiler feed pump as it enters into resonance with the piping circuit. An analysis is carried out of the equivalent linear system under harmonic conditions. The analytical model provides reasonable agreement with the observations for the three tested piping configurations. Some insight is provided in the mechanism of the pulsations and the dynamic impedances of typical component equipment.
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