Full-scale measurements of thrust and power of inverter-driven jet-fans

Full-scale measurements of the performance of a jet fan operating at speeds ranging from 20% to 100% of full-speed are presented. The purpose of the tests was to assess predicted power savings resulting from using several fans at low speed to deliver the same thrust as fewer fans at full-speed. The measurements allow for electrical losses in cables and in inverters used to achieve variable-speed control. The expected savings are confirmed and quantified. The tests were conducted in a factory environment enabling high quality measurements to be obtained, thereby leaving no room for doubt about the savings. However, further tests in a tunnel environment are still required to complete the work - to assess whether multiple low-thrust jets have the same influence on tunnel air flows as fewer higher-thrust jets with equal total thrust. Although the principal objective of the paper is to present unambiguous experimental evidence, a theoretical background is also presented, highlighting some difficulties with a conventional analysis of jet-fan performance.