Date of Award
2005
Degree Type
Thesis
Degree Name
Master of Engineering Science
Program
Mechanical and Materials Engineering
Supervisor
Dr. R. J. Martinuzzi
Second Advisor
Dr. G. A. Kopp
Abstract
When designing stators it is necessary to know the angle of the velocity at the leading edge so that the stator can be properly aligned with the flow in order to maximize the fan efficiency. While initial sizing methods provide estimates for velocity and swirl angle downstream of the fan, there are many assumptions made. Commonly experimental techniques are used to validate the flow angle. In this study, velocity measurements and flow angle information for an automotive engine cooling fan module obtained with Laser Doppler Velocimetry (LDV) and a five hole probe (5HP). The purpose of the measurements was twofold: to provide insight as to the flow field upstream of the stators to see if assumptions made in initial 2D stator design methods were valid and to determine the applicability of both methods for measuring this type of flow. The LDV measurements were made in random and coincidence mode, and these measurements were compared to the mean phase averaged velocities. It was found that while these methods varied by less than 5%, the three methods were still outside of the uncertainty, and therefore the former methods introduced uncertainty to the data. It was clear from the LDV data that large velocity gradients downstream of the fan blade and upstream of the stator blade exist, and that these gradients are likely due to radial flow rather than an upstream influence of the stators. It was noted that while the initial design methods may be capable of giving a reasonable approximation of the flow entering the stator, to determine the more detailed components of the flow like radial variations and phase averaged velocities, it is necessary to use experimental methods. The probability density function of many of the measurements were found to be bi-modal and not Gaussian in nature. One mode represented the main passage blade flow, and the other represented the flow in the blade wake. When designing stators for blades with bi modal distributions, it was recommended to use the mode representing the main passage flow to achieve best stator efficiency. Finally, it was observed that the five hole probe is an inadequate device for making detailed velocity measurements downstream of an axial automotive engine cooling fan. LDV measurements showed the intrusive nature of the device and the velocity values were further biased because the five hole probe could not measure the dynamic component of the flow. While the cost and ease of use makes the five hole probe appear to be an attractive device for measuring this type of flow, the study showed that it is only somewhat useful in predicting trends in the flow,and not accurate in measuring mean velocities or flow angles as it is intended.
Recommended Citation
Holmes, William J., "EXPERIMENTAL INVESTIGATION OF VELOCITIES DOWNSTREAM OF AN AXIAL FLOW FAN FOR GUIDE VANE DESIGN" (2005). Digitized Theses. 5116.
https://ir.lib.uwo.ca/digitizedtheses/5116