A Study on Design Optimization of Centrifugal Fan of High Voltage Generator by Numerical Analysis

Case Studies: Aerodynamics

A generator is a device that converts the mechanical energy provided by an engine, a gas turbine, a steam turbine, etc. to electric energy. Heat is generated during the energy conversion process and the internal temperature of the generator is increased. A cooling fan is used to suppress the generator temperature characteristic within the numerical value in the standard. Choosing a cooling fan in a generator cooling design is a key core technology. The required air volume and required static pressure must be satisfied and the influence of the mechanical loss and noise must be considered. If the fan selection is not appropriate, it will affect the generator performance and increase the. Therefore, an effective cooling fan design is important for the selection of an optimal cooling fan.
The high voltage generator consists of a rotor, a stator, a winding, a cooling fan, and a heat exchanger. The internal structure is complicated, and the flow resistance is generated as the cooling channel is either enlarged or reduced. Flow resistance is an important factor in determining the operating point of the fan. The system resistance is generally calculated by an equivalent circuit program or a numerical analysis based on the empirical formula. The air flow rate of the fan operating point of a 5 MW class high voltage generator is about 5.94 m³/s and the static pressure is about 1087 Pa. We provided the system resistance curve according to the fan operating point to a fan specialist company and designed four kinds of fans according to the shape of the blades. We performed a numerical analysis and an ANSI/AMCA standard 210-99 specification fan performance test to verify the performance of the fans. We used the ANSIS ICEM-CFD grid generation program to analyze the fan performance characteristics through a numerical analysis, and generated about 6 million grids. We expected turbulent flow so we used the STANDARD model. The comparison of the performance curves through the numerical analysis and the performance tests. As a result of the comparison, we could obtain a reliable analysis result.