Compressor speed

DATA INPUT Ambient Preseure Compressor Inlet Pressure Compressor Discharge Pressure Compressor Inlet Temperature Compressor Discharge Temperature Compressor Speed... 

The increase in compressor pressure ratio decreases the operating range of the compressor. The operating range of the compressor stretches from the surge line at the low flow end of the compressor speed line to the choke point... 

If the pressure coefficient is now, or was in an earlier step, 5% uiutei the 0.29 value, calculate a new mean blade velocity using the rounded off number of stages and the original pressure coefficient, 0.29. Use the calculated blade velocity in the subsequent step for compressor speed Calculate the speed. 

Step 5. Calculate a mean diameter in preparation for calculating the compressor speed. Use Equation 6.18. 

I he closer the motor and compressor speed-load curves are to each other, the longer the driver will take to reach full speed, and the hotter the motor will get (see Figure 7-2). 

As with the motor driver, the steam turbine must be matched to the compressor. Also, a turbine rating of 110% of the maximum power required by the compressor should be specified. This should be at the compressor s normal speed point. The turbine speed should include a maximum continuous speed 105% of the normal compressor speed. API Standards 611 and 612 cover general purpose and special purpose steam turbines 7, 8]. 

With the introduction of the new instruments, speed is basically taken for granted. It is a very important parameter for reciprocating compressors, however, because speed is one of the factors in generating displaced volume. For the axial and the centrifugal compressor, speed offers a multiple influence. In the fan laws stated in Chapter 5, speed was the common parameter in both capacity and head. In fact, since head is proportional to speed squared, it becomes quite important that the speed be accurate. 

A speed controller can help extend the operating range and efficiency of the compressor. As the flow rate increases, the compressor speed can be increased to handle the additional gas. Compressor speed will stabilize when the actual flow rate to be compressed equals the required flow rate for the cylinder at the preset suction pressure. As the flow rate decreases, the compressor slows until the preset suction pressure is maintained. 

A recycle valve is needed for surge control as well as for the conditions listed above for reciprocating compressors. At constant speed the head-capacity relationship will vary in accordance with the performance curve. For a constant compressor speed ... 

Reciprocating compressor capacity may easily be adjusted by changing compressor speed, changing compressor cylinder clearance, unloading compressor cylinder inlet valves, recycling gas from unit discharge to unit suction, or a combination of these methods. All these methods may be accomplished either manually by the operator or automatically by the control panel. 

Figure 16-12 shows the effect of ambient temperature on the horsepower output of a typical two-shaft gas turbine engine. At high temperatures the horsepower is limited by the maximum allowable power turbine inlet temperature. At low ambient temperatures, the available horsepower is limited by the maximum allowable air compressor speed. 

The horsepower output of a gas turbine is a direct function of flow rate across the power turbine, which is a function of air compressor speed and combustion temperature. Figure 16-13 shows the relationship between... 

Spherical roller bearings support of radial and thrust load, expecially when the shaft is long excellent paper mill machinery, air compressors, speed reducers, cranes... 

Figure 12-80. Compressor speed in rpm. (Used by permission Coie, S. L. Oil and Gas Journal, V. 58, No. 6, 1960. PennWeii Pub-iishing Company. Aii rights reserved.)...

For constant intake volume, compressor speed, efficiency, and no throtding, but with discharge pressure changing to reflect the effect of temperature ... 

Figure 13-6C. Effects of pulsation filter on orifice flow meter charts at 300 rpm compressor speed. (A) Before peak-to-peak differential pulsations were 160 psi, and (B) after installation of filter pulsation, levels dropped to 1.5 psi. (Used by permission von Nimitz, W. W., and O. Flanigan, Oil and Gas Journal, p. 60, Sept. 8, 1980. PennWell Publishing Company. All rights reserved.)...

After the anticipated disturbing frequencies have been determined, it is necessary to begin the sizing of the filter system. The cutoff frequency should be set at least one cycle per second below the lowest frequency to be filtered. The base frequency is determined from compressor speed and should be determined at the lowest anticipated compressor speed for variable-speed compressors. The following equation is used to determine cut-off frequency for a low-pass filter ... 

Material Capacity Suction pressure Suction temperature Discharge pressure Discharge temperature Compressor speed Single-cylinder, double-acting... 

The compressor speed may be reduced by two-speed electric motors or by electronic variation of the motor speed, down to a lower limit dictated by the inbuilt lubrication system. Many highspeed industrial machines are still driven by steam turbines and this gives the opportunity for speed control within the limits of the prime mover. 

Capacity control of these compressors is achieved by varying the compressor speed by means of an inverter motor. 

Suppose the openloop process transfer function relating controlled variable magnet temperature and manipulated variable compressor speed is... 

Gas turbines can be arranged either in single-shaft or split-shaft types. The single-shaft arrangement requires the turbine to provide power to drive both the compressor and the load. This means that the compressor is influenced by the load. The compressor efficiency is a function of the speed. When the load is increased, the compressor speed is slowed down, which is not desirable. It is very desirable to make the gas turbine a reliable shaft-driven propulsion system therefore, the compressor speed must be held constant. Hence, split-shaft gas turbines are developed. In this arrangement, there are two turbines each with its own independent shaft. The sole function of the first turbine is to drive the compressor at a steady speed without being influenced by the load. The net power of the gas turbine is produced by the second turbine as shown by Fig. 4.9. 

Control Devices In many installations the use of gas is intermittent, and some means of controlling the output of the compressor is therefore necessary. In other cases constant output is required despite variations in discharge pressure, and the control device must operate to maintain a constant compressor speed. Compressor capacity, speed, or pressure may be varied in accordance with requirements. The nature of the control device will depend on the function to be regulated. Regulation of pressure, volume, temperature, or some other factor determines the type of regulation required and the type of the compressor driver. 

If the compressor is suction-volume-limited, we say that it is speed-limited. If the compressor is driven by an AC motor, its speed is determined by the motor speed and any connecting gears. If the compressor is driven by a turbine, then the rated speed of the turbine limits the compressor speed. 

When antimony was injected, hydrogen production decreased to 58 SCF/BFF, and the load on the compressor was eased. Coke production decreased as evidenced by a decreased load on the air blower and the 17°F decrease in regenerator temperature. As the load on the compressor was eased, the compressor speed controller was effective, and this stabilized the refinery steam balance. Overall, the unit operated closer to steady state, and this helped... 

Metals passivation allows refiners to maximize the charge of lower value feeds. Injection of antimony into the Phillips Sweeny, Texas HOC decreased unit hydrogen production and decreased the process gas compressor speed about 500 rpm. This enabled the refinery to increase throughput 10% and process a more difficult to crack feedstock (14). Fifteen percent of Oriente crude from Ecuador was blended into the Phillips Borger, Texas refinery crude slate with the use of metals passivation at its HOC. Metals in the HOC feed and on the HOC catalyst increased significantly, but yield of hydrogen was still less than it had been prior to metals passivation (6). 

The liquid level in the flash drum is controlled by manipulating liquid product Lc. A temperature controller manipulates heat removal in the condenser to hold drum temperature constant. Compressor speed is controlled, which is assumed to fix the recycle gas flowrate FR. 

Recycle gas flowrate FR is held constant by fixing compressor speed. 

The control systems enabled in the simulation were i) the IHX flow balance controller, which acts through primary compressor speed to maintain equal flow rate on the hot and cold sides of the IHX ii) the bypass flow controller which acts through bypass valve loss coefficient to maintain a shaft speed set point. Additionally the pre-cooler and intercooler cold side flow rates are supplied as forcing functions. The flow rates were roughly matched to decay heat level. The PCU shaft set point is decreased from 60 Hz over time to have the shaft speed more or less track the decreasing reactor energy production rate. 

If the compressor serves a constant pressure process (point [1] on Figure 2.18) by speed variation and the process demand is reduced to point (2), the compressor speed has to be reduced to 80% (Curve II) where the operating efficiency is only 74%. In order to accomplish the same capacity reduction in a "mostly friction" system, it is necessary to reduce the compressor speed to 60% (Curve III), so that the compressor will operate at the new operating point (3) at 77% efficiency. 

Compressor speed is automatically controlled to ensure that the system can respond rapidly and accurately to changes in acid... 

Both axial and centrifugal compressors are subject to an unstable region of low flow operation called surge. This region is defined by the pressure-flow relationship which has a peak determined by the operating speed. For various compressor speeds, these peaks may be connected to determine a surge line, which defines a region of unstable operation at lower flows. 

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