The composition of the single stage centrifugal compressor
Impeller is a cantilever type design, is located in the free end of shaft. According to the design of the compressor, use half open or closed impeller. For low pressure increase, that is, relative to the lower blade tip speed, using closed impeller, because the closed impeller has a steep curve. Impeller can be accurate milling, or welding design. Often use both corrosion resistance and can meet the strength requirements of duplex stainless steel material, also can use other CrNi alloy steel and special materials such as titanium alloy.
Accelerated gas flows into the shell and tube type after leaving the impeller diffuser, the flow velocity is reduced, high kinetic energy is converted to static pressure. Centrifugal compressor housing mostly by CrNi alloy steel casting or welded together, the size of the shell thickness and external reinforcement choice should pay attention to must not exceed allowable deformation, it is particularly important to the operation of the vacuum conditions.
Compressor of helical gear is integrated within the compressor. As a result, the gear does not need to connect between the compressor shaft and shaft section. Thrust ring in the pinion shaft. The thrust ring to send low residual axial thrust of the spindle.
Bearing and lubrication system
Bearings must ensure stable and no vibration of the centrifugal compressor operation conditions, to withstand the pinion shaft of high-speed rotation. As a result, the radial tilting pad bearings can be used for high speed small gear shaft, gear shaft running on polyhedral fluid dynamic pressure bearing, thrust bearing of the rest of the axial thrust.
By the pressurized oil lubrication. To this end, installed a standardized lubrication system, it is composed of oil tank, the main oil pump, oil pump, oil filter, oil cooler.
A variety of different types of prime mover can be used to drive the steam compressor again. For each operating mode, drive on the basis of its efficiency and available power type selection. Commonly used motor as drive device, motor has a considerable advantage is due to their standardized protection type and size, lower power/weight ratio, power/volume ratio, price/performance ratio, as well as the maintenance of the minimum requirements.
Can use two types of three-phase asynchronous motor, low pressure motor and high pressure. Usually under the condition of voltage 400 v or 690 v power supply, low pressure motor can respectively under 630 kW and 1250 kW power operation. High voltage motor and frequency converter can be used to power up to 6000 kW. Can use the inverter in the three-phase asynchronous motor variable speed operation.
If waste steam can be recycled and used as a variable speed steam turbine compressor of the prime mover is desirable. Although in this case, a single stage steam turbine efficiency is lower, but if it is due to price reasons, it becomes relatively minor.
Surveillance and safety equipment
To discover anomalies arising from the compressor work, provide early warning and prevent the mechanical damage of the equipment, equipment loss need a lot of surveillance and safety equipment. Usually includes the following contents:
- the impeller speed
- vibration monitoring
- tank of liquid level
- Oil pump
- oil cooler
- oil filter pressure difference
- the flow of oil
- bearing temperature
- motor winding temperature
- motor bearing temperature
- the compressor shell temperature
- shaft axial displacement of the indicator
- centrifugal compressor surge protection
The control of the compressor
Usually by mechanical steam again compressor heating evaporation device can stable operation within a certain scope, such as quality parameters such as flow rate, pressure, temperature fluctuations over time. Often hope evaporation can change on a wide range (that is, the part load operation), so must change the different heating rate. Equipment processing capacity change is achieved by changing the temperature or pressure distribution curve. The changes in the design of the compressor equipment performance must be considered and the balance of the design task. Equipment of operational use so-called or performance curve to describe the equipment characteristic curve, it reflects the essential of saturated steam temperature and suction the relationship between the steam mass flow rate. The operation of the equipment performance to a great extent, should through the test to decide, or at least should be estimated. To steam and optimal operation of compressor equipment, evaporator and the compressor characteristic curve must be consistent.