Enhancing Axial Flow Fan Performance in Air-Cooled Condensers: Tip Vortex Manipulators and Comparative Analysis of Numerical Simulation and Experimental Testing

TL;DR

This study investigates how blade tip modifications, specifically tip vortex manipulators, can enhance axial fan performance in air-cooled condensers through combined CFD simulations and experimental testing, revealing promising improvements and modeling challenges.

Contribution

The paper develops and tests new tip vortex manipulators for axial fans, combining CFD and experimental validation to assess their impact on fan efficiency and flow stability.

Findings

Tip modifications improve fan performance experimentally.

CFD simulations accurately predict unmodified fan behavior.

Discrepancies in performance predictions suggest fluid-structure interactions are important.

Abstract

Direct dry-cooled power plants typically operate numerous large-diameter axial flow fans in air-cooled condensers to facilitate the condensation of steam in the plant thermodynamic cycle. Enhanced fan efficiency may, at scale, lead to significant parasitic power reductions and subsequent increases in plant power output. The performance of these fans may be increased by adding blade tip modifications which act to control blade tip leakage flow. Previous studies have shown that manipulating the tip leakage vortex increases the blade-to-air momentum transfer and stabilizes the air flow structures as it traverses the fan blade. This paper takes a step towards the development of improved tip vortex manipulators for an ACC fan. Three-dimensional computational fluid dynamic simulations, and experimental testing of the modified and unmodified fan within an ISO test facility is performed. The results are then utilized to assess the accuracy of the simulation model, visualize the manipulated flow structures at the blade tip, and ultimately quantify the effect of the endplate designs on fan performance. Excellent correlation between numerical and test results for the unmodified fan is observed, and the benefit of blade tip modification on fan performance is again confirmed experimentally. The simulation model however fails to predict improvements in fan performance under modification, and simulated tip leakage flows are investigated for clarification. It is hypothesized that deflection of tip endplates under operation account for differences between simulation and experiment, and that fluid-structure interaction analyses could potentially resolve discrepancies.