Performance centrifugal compressor

Figure 3-9. Typical centrifugal compressor performance characteristics.

Lapina, R. P., Escalating Centrifugal Compressor Performance, Proce-, Compressor Technology, Vol. T, Houston, TX Gulf Publishing Compa-ti>. 1982. 

Figure 12-62. Representative centrifugal compressor performance with inlet guide vanes. (Used by permission A C Compressor Corporation.)...

Quick Approximation Method for Centrifugal Compressor Performance... 

The Operating System. Regardless of calculated centrifugal compressor performance, the machine will operate only on or along its operating curve to fit the system of which it is a part. This is quite similar to the system performance of a centrifugal pump. Friction, other pressure drops of the system, and how friction varies with operating conditions determine machine performance. 

Lapina, R. P, Estimating Centrifugal Compressor Performance, Process Compressor Technology, V. 1, Gulf Publishing Co., Book Div., Houston, TX. 

Figure 19-3 depicts a typicel centrifugal compressor performance map... 

Figme 7b Centrifugal compressor performance i high compression ratio. [5 ... 

The compressors operating range is between two major regions as seen in Fig. 10-74, which is a performance map of a centrifugal compressor. These two regions are. surge, which is the lower flow limit of... 

The performance of a centrifugal compressor (discharge to suction-pressure ratio vs. the flow rate) for different speeds is shown in Fig. 11-87. Lines of constant efficiencies show the maximum efficiency. Unstable operation sequence, called surging, occurs when compressors fails to operate in the range left of the surge envelope. It is characterized by noise and wide fluctuations of load on the compressor and the motor. The period of the cycle is usually 2 to 5 s, depending upon the size of the installation. 

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. 

Compressor performance can be represented in various ways. The commonly accepted practice is to plot the speed lines as a function of the pressure delivered and the flow. Figure 3-9 is a performance map for a centrifugal compressor. The constant speed lines shown in Figure 3-9 are constant aero-dynamic speed lines, not constant mechanical speed lines. 

Figure 3-10 shows a similar performance map for an axial-flow compressor. Note the smaller operational flow range for the axial-flow compressor as compared to the centrifugal compressor. Figure 3-11 shows a typical compressor map presented from a slightly different viewpoint. On this map. 

Deniz, S., Greitzer, E. and Cumpsty, N., 1998, Effects of Inlet Flow Field Conditions on the Performance of Centrifugal Compressor Diffusers Part 2 Straight-Channel Diffuser, ASME Paper No. 98-GT-474. 

Klassen, H.A., Effect of Inducer Inlet and Diffuser Throat Areas on Performance of a Low-Pressure Ratio Sweptback Centrifugal Compressor, NASA TM X-3148, Lewis Research Center, January 1975. 

Figure 1-3 presented a general form performance curve for each of the compressors. The centrifugal compressor exhibited a relatively flat curve compared to the other machines. Flat is defined as a relatively low head rise for a volume change. Translated to pressure terms, it means a relatively low pressure change for a given volume change. It is important to understand some of the basics that contribute to the curve shape. 

Ai the risk of misleading the reader, this section will just touch a few points concerning maintenance. One frequently asked question is, what is critical and what needs special consideration when performing maintenance on the centrifugal compressor While there are many areas that... 

As was discussed in the centrifugal compressor chapter, there is a geometric rdaiionship that can be used to determine performance. 

Obviously this test applies only to the centrifugal compressor. The manufacturer normally performs this test whether specified or not. Since the user does have an interest in the test, some discussion of the parameters is in order. API 617 mandates the test, which includes the requirement to spin the impeller at a speed of 115% of the maximum continuous speed for a duration of one minute. 

Sayyed, S., Aerodynamic Shop Testing Multistage Centrifugal Compressor and Predicting Gas Performance, ASME 78-PET-28, New York American Society of Mechanical Engineers, 1978,... 

In general configuration the centrifugal compressor resemhles a centrifugal pump. However, the significant difference in performance requirements lies in the compress-ihility of the gas. A dynamical analogy between these two... 

Centrifugal compressors are not items that the process company or its mgineers should attempt to design in great detail. Rather, it is more important that they be in a strong position to (a) specify what is needed for the process, (b) understand the manufacturer s recommendations, and (c) evaluate the recommended design and performance in the process situation. Also see reference 117. 

Figure 12-59. Performance ranges for special high-speed/high-pressure, single-stage Sundstrand Compressors (except model HMC 5000) centrifugal compressors. Special impellers are available for performance outside the envelopes shown. Performance varies with the gas involved. (Used by permission Sundstrand Compressors Bui. 450, April, 1995. Sundstrand Fluid Handling Corporation.)...

Figure 12-61A. Typical performance map of centrifugal compressor. (Used by permission Fullermann, J. Report, Centrifugal Compressors, 1963. Cooper Energy Services, Cooper-Bessemer Rotating Products Div., Cooper-Cameron Corporation. Originally printed Advances in Petroleum Chemistry and Refining, Interscience Publishers Div., John Wiley and Sons. No longer in publication. All rights reserved.)...

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