Matching compressor characteristics

Rodgers, C., Influence of Impeller and Diffuser Characteristic and Matching on Radial Compressor Performance, SAE Preprint 268B, January 1961. 

The motor and gear combination must provide the proper input speed to the compressor. Therefore, speed selection should consider whctRei the 1,800 rpm, or the 1,200 rpm motor and the corresponding gear provides the more economical combination. Before selecting motor speed, motor characteristics should be obtained for both speeds. The speed-torque and speed-current curves, power factor and efficiency values should be compared and evaluated. The most important considerations in matching the motor to a compressor are ... 

Figure 12-112. Performance characteristics for a typical single-stage rotary helical rotor compressor, using matching helical rotors. (Used by permission Fairbanks, Morse, Co. for earlier editions. [Company no longer exists producing compressors, 1998, per research information.])...

Electric motors are the most common drivers for the m ority of pumps, compressors, agitators, and similar equipment in the process industries. Process engineers should obtain the assistance of a qualified electrical engineer before completing motor specifications ior the wide variety of equipment applications and respective power sources. The use of standard specifications for the various types and classes of motors is helpful and reduces repetitious details. Be certain that the type of motor is properly matched to the service, atmosphere, load characteristics, and available type and power factor of the electrical energy to drive the motor. Some basic guides are summarized, but they cannot be used as all-inclusive rules to fit all plant or equipment condi-... 

Another operational limit in the CFB system involves gas suppliers. Three types of gas suppliers, i.e., a reciprocating compressor, a blower with throttle valve, and a compressor, are commonly used in the CFB system. For blower operation, as the gas flow rate decreases, the pressure head of the blower increases. For compressor operation, the pressure head of the compressor can be maintained constant with variable gas flow rates. The interactive behavior between a CFB system and a blower can be illustrated in Fig. 10.9, where dashed curves refer to the blower characteristics and solid curves refer to the riser pressure drop. At point A, the pressure drop across the riser matches the pressure head provided by a blower thus, a stable operation can be established. Since the pressure drop across the riser in fast fluidization increases with a decrease in the gas flow rate at a given solids circulation rate, a reduction in the gas flow rate causes the pressure drop to move upward on the curve in the figure to point B with an increase in the pressure drop of Spr. In the case shown in Fig. 10.9(a), with the same reduction in the gas flow rate, i.e., SQ, the increase in the pressure drop, Spr, from point A to point B is greater than that which can be provided by... 

To make up the difference between the expected expander returned power and the required compressor input power. Meruit designed an air system using a commercially available positive-displacement compressor driven by an electric motor in tandem with Meruit s turbocompressor. Meruit designed a family of compressor and expander wheels with var5dng characteristics (specific speed, dimensional ratios, etc.) representing different compromises in providing performance compatible with the DOE specifications. After extensive evaluation, a compressor wheel was chosen to provide a desired pressure curve over a wide range of mass flows, and a turbine wheel was matched to it. The chosen compressor wheel is intended to trade peak efficiency for extended turndown performance. 

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