Laboratory Testing of Fans with High Swirl
1.6 Test Rig & Instrumentation
ISO 5801 "Fans — Performance testing using standardized airways" and AMCA 210, "Laboratory methods of testing fans for certified aerodynamic performance rating" are the primary test standards for commercial and industrial fans. Each of these standards details measurement equipment, fan test configurations, operational requirements, calculations, and expected uncertainties. Multi-nozzle inlet and outlet test chambers detailed in these standards provide flexibility to test a large range of fan sizes and provide the bulk of industry fan testing.
Mark Stevens and Marton Gyuro presented results of a round robin series of tests on three fans in 11 different labs at the Fan 2015 conference in Lyon. This testing showed good correlation from lab to lab, but also identified an area where further study was needed. Specifically, fans with a significant amount of swirl at their outlet showed significant difference between tests using inlet vs. outlet test chambers. CFD analysis was presented to illustrate the cause of these differences. While ISO 5801 and AMCA 210 each have requirements regarding the ratio of fan area to chamber area, the test results presented suggested that these requirements should be much more stringent than current requirements.
This paper presents results of fan performance tests specifically designed to determine acceptable area ratios required for accurate ratings for fans with high swirl. Two axial fan sizes were tested on three different sized test chambers in both inlet and outlet configurations, resulting in six different area ratios ranging from 6 to 136. The fans were designed with removable straightening vanes in order to provide both high swirl and low swirl conditions at their discharge.
Test results confirmed that the area ratios required for accurate and repeatable fan tests results are higher than current standards require, though not as high as suggested in the previous round robin testing. The required area ratios also depend on the shape of the test chamber, whether the cross section is round or square.