Principle Of Static Guide Vane Adjustment For Vertical Multi-stage Pipeline Centrifugal Pump

Jan 29, 2025

When not adjusted, the installation angle of the static guide vanes of the vertical multi-stage pipeline centrifugal pump is zero. The static guide vanes of the vertical multi-stage pipeline centrifugal pump have little effect on the inlet airflow, and the airflow will flow radially into the impeller blades. When the installation angle of the static guide vanes of the vertical multi-stage pipeline centrifugal pump is adjusted to be greater than zero, it can be seen that the airflow will flow into the impeller blades, resulting in simultaneous changes; The change will inevitably cause a change in the flow rate, and the change will cause a change in the theoretical total pressure PT. If the pre rotation is positive, the theoretical total pressure PT of the fan will be smaller, which will cause the performance curve to shift downwards, thereby moving the operating point towards the low flow area and reducing the flow rate.
In fact, another factor that cannot be ignored when increasing the installation angle of the static guide vanes of the vertical multi-stage pipeline centrifugal pump is that the static guide vanes of the vertical multi-stage pipeline centrifugal pump have a certain throttling effect on the airflow velocity and change its direction, resulting in an increase in local resistance loss and impact loss inside the fan, leading to a decrease.
Due to the advantages of simple construction, small device size, reliable operation, easy maintenance and management, and low initial investment, the static guide vane adjustment of vertical multi-stage pipeline centrifugal pumps is widely used in centrifugal fans. In addition, when the adjustment amount is small, the energy-saving effect of static guide vane adjustment in vertical multi-stage pipeline centrifugal pumps is not worse than that of variable speed adjustment. However, as the adjustment amount increases, its throttling effect gradually increases and the adjustment efficiency continuously decreases. Based on this characteristic, for centrifugal fans with a large adjustment range, a combined adjustment method of vertical multi-stage pipeline centrifugal pump static guide vanes and dual speed motors can be used to achieve high adjustment economy throughout the entire adjustment range.
Therefore, the centrifugal induced draft fans of large units in thermal power plants have widely adopted this joint adjustment method. The static guide vanes of the vertical multi-stage pipeline centrifugal pump of axial flow and mixed flow fans are adjusted to meet the performance requirements of the fan when the load changes. Some axial flow and mixed flow (also known as radial acceleration axial flow) fans have adjustable installation angles at the inlet of the vertical multi-stage pipeline centrifugal pump static guide vanes. This adjustment method, which adjusts the flow rate during operation by changing the installation angle of the static guide vanes of the vertical multi-stage pipeline centrifugal pump, is called the static guide vane adjustment of the vertical multi-stage pipeline centrifugal pump.
The construction and adjustment principles of the static guide vanes of vertical multi-stage pipeline centrifugal pumps for axial and mixed flow fans are similar to those of the axial guide vanes of centrifugal fans. Compared with the axial guide vane adjustment performance of centrifugal fans, the static guide vane adjustment of vertical multi-stage pipeline centrifugal pumps for radial acceleration axial flow fans and axial flow fans can be adjusted for both positive pre rotation (reducing flow rate) and a certain degree of negative pre rotation (increasing flow rate) (even if the installation angle of the static guide vane of the vertical multi-stage pipeline centrifugal pump is 0>0 °). When selecting a fan, the 100% rated load flow operating point (MCR point) of the unit can be selected at the highest efficiency point, while the maximum flow point considering safety flow (TB point: the point corresponding to the design parameters) can be selected on the high flow side of the highest efficiency point (negative pre swirl regulation). Therefore, it has higher operational economy than centrifugal fans that can only perform positive pre rotation adjustment for inlet flow regulation. Therefore, many boiler induced draft fans in thermal power plants use vertical multi-stage pipeline centrifugal pumps with static guide vane adjustment for radial acceleration axial flow fans.
Variable speed regulation refers to the adjustment method of changing the performance curves of pumps and fans by changing the speed, while keeping the pipeline performance curve unchanged, in order to change their operating conditions.
The variable speed regulation of pumps and fans can generally be divided into two categories: one is the variable speed regulation of fixed speed motors through transmission devices; Another type is to use a variable speed prime mover to directly drive the variable speed regulation of the pump and fan. The commonly used variable speed adjustment methods for power plant pumps and fans are shown below. Only a brief introduction will be given to the working principles, characteristics, and applications of several typical variable speed adjustment methods that are widely used.
Variable speed regulation of fixed speed electric motor through transmission device
The variable speed regulation of hydraulic coupling is a type of blade type transmission machinery that uses liquid (mostly oil) as the working medium and utilizes liquid kinetic energy to transfer energy. It is also known as hydraulic coupling or liquid power transmission device (abbreviated as HKD). According to their different application scenarios, they can be divided into four types: ordinary type (standard type, clutch type), torque limiting type (safety type), traction type, and speed regulating type. The speed regulating type is used for energy-saving pump and fan speed regulation.
The application of hydraulic couplings in energy-saving speed regulation of pumps and fans. Due to the use of hydraulic couplings for variable speed regulation, blade pumps and fans have significant energy-saving effects compared to throttling regulation. Therefore, variable speed hydraulic couplings have been widely used as speed control devices for pumps and fans, especially in enterprises such as thermal power plants, mines, steel plants, and refineries.