Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

Tong-Miin Liou,Meng-Yu Chen

doi:10.1155/s1023621x01000161

Tong-Miin Liou, Meng-Yu Chen

Open Access

https://doi.org/10.1155/s1023621x01000161

Copy DOI

Abstract

Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.

Highlights

Centrifugal fans (Fig. 1) are widely applied throughout industry, such as the ventilation system of tunnel, air conditioning system of building, cooling system of electronic devices, etc
A large majority of previous research in centrifugal fans has focused on the impeller inlet and outlet flows not inside the impeller passage
The results show that at high flow rates (Q*= 143%) the stagnation line is on the inside of the tongue

Summary

INTRODUCTION

Centrifugal fans (Fig. 1) are widely applied throughout industry, such as the ventilation system of tunnel, air conditioning system of building, cooling system of electronic devices, etc. The conventional method of evaluating the performance from the conditions at a fan’s entrance and exit is insufficient. Measurements of flow in a centrifugal fan are difficult partly due to the complex geometry. A large majority of previous research in centrifugal fans has focused on the impeller inlet and outlet flows not inside the impeller passage. Among them, Raj and Swim (1981) used a single hot wire probe to measure the mean velocities and the velocity fluctuations at the impeller exit of a small forward curved (FC) centrifugal fan. Their results showed the impeller flow to be highly

Throttle

RESULTS AND DISCUSSION

CONCLUSIONS