For an unpowered turbofan in flight, the airflow through the engine causes the fan to freewheel. This paper considers the flow field through a fan operating in this mode, with emphasis on the effects of blade row losses and deviation. A control volume analysis is used to show that windmilling fans operate at a fixed flow coefficient which depends on the blade metal and deviation angles, while the blade row losses are shown to determine the fan mass flow rate. Experimental and numerical results are used to understand how the loss and deviation differ from the design condition due to the flow physics encountered at windmill. Results are presented from an experimental study of a windmilling low-speed rig fan, including detailed area traverses downstream of the rotor and stator. Three-dimensional computational fluid dynamics (CFD) calculations of the fan rig and a representative transonic fan windmilling at a cruise flight condition have also been completed. The rig test results confirm that in the windmilling condition, the flow through the fan stator separates from the pressure surface over most of the span. This generates high loss, and the resulting blockage changes the rotor work profile leading to modified rotational speed. In the engine fan rotor, a vortex forms at the pressure surface near the tip and further loss results from a hub separation caused by blockage from the downstream core and splitter.
Skip Nav Destination
Article navigation
October 2016
Research-Article
Loss and Deviation in Windmilling Fans
Ewan J. Gunn,
Ewan J. Gunn
Mem. ASME
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: ejg55@cam.ac.uk
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: ejg55@cam.ac.uk
Search for other works by this author on:
Cesare A. Hall
Cesare A. Hall
Mem. ASME
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: cah1003@cam.ac.uk
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: cah1003@cam.ac.uk
Search for other works by this author on:
Ewan J. Gunn
Mem. ASME
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: ejg55@cam.ac.uk
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: ejg55@cam.ac.uk
Cesare A. Hall
Mem. ASME
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: cah1003@cam.ac.uk
Whittle Laboratory,
University of Cambridge,
1 JJ Thomson Avenue,
Cambridge CB3 0DY, UK
e-mail: cah1003@cam.ac.uk
1Corresponding author.
Manuscript received July 24, 2015; final manuscript received March 16, 2016; published online April 26, 2016. Assoc. Editor: Li He.
J. Turbomach. Oct 2016, 138(10): 101002 (9 pages)
Published Online: April 26, 2016
Article history
Received:
July 24, 2015
Revised:
March 16, 2016
Citation
Gunn, E. J., and Hall, C. A. (April 26, 2016). "Loss and Deviation in Windmilling Fans." ASME. J. Turbomach. October 2016; 138(10): 101002. https://doi.org/10.1115/1.4033163
Download citation file:
Get Email Alerts
Related Articles
High Resolution RANS Nonlinear Harmonic Study of Stage 67 Tip Injection Physics
J. Turbomach (May,2015)
Analysis and Prediction of Shock-Induced Vortex Circulation in Transonic Compressors
J. Turbomach (December,2015)
Effect of Inlet Distortion Features on Transonic Fan Rotor Stall
J. Turbomach (July,2018)
Related Proceedings Papers
Related Chapters
Fans and Air Handling Systems
Thermal Management of Telecommunications Equipment
Other Components and Variations
Axial-Flow Compressors
User-Interactive Futuristic Displays Based on PIC Microcontroller
International Conference on Computer and Computer Intelligence (ICCCI 2011)