Performance testing of an axial flow fan in an A-frame test facility

[摘要] ENGLISH ABSTRACT: The primary objective of this research and experimental investigation is to determine the performance of an axial flow fan in an A-frame test facility. Commissioning of the A-frame test facility required certain modifications which allowed the facility to be used for testing purposes. Modifications include a new fan drive system, fan bridge, heat exchanger and structural supports. The bell mouth roundness was improved upon, achieving a more constant tip clearance around the casing, and all air leaks around the facility were sealed to prevent loss of mass flow. Tests were conducted on the B2-fan, according to standardised fan testing procedures in ISO 5801 (2007) Type-A, to obtain the fan characteristics at selected blade angles. The measurements recorded at the A-frame test facility included outlet velocity, inlet velocity, fan torque and rotational speed measurements. The outlet velocity profiles differ for the two heat exchanger outlets, but the total volumetric flow rate differs only by 3% for the two sides. It was also found that the velocity profile stays similar with a change in blade angle, but increases in magnitude as the blade angle is increased. Pressure measurements according to ISO 5802 (2008), at the walls of the plenum chamber, were regarded as unusable due to it being much lower than the expected pressure.With the use of the system draft equation from Kröger (2004, 8.1.30) it was possible to calculate a recovery coefficient for the A-frame plenum chamber at different blade angle settings of the B2-fan, with values of 0.505, 0.685 and 0.412 for the 28º, 31º and 34º blade angles respectively. The recovery coefficient calculated for the M-fan equalled 0.143 and 0.322 for the 34º and 35º blade angles respectively. This value represents the portion of kinetic energy that is converted back into a pressure. The sensitivity of the recovery coefficient to change in volumetric flow rate and heat exchanger loss coefficient was also investigated with the use of a Monte Carlo simulation. The importance of accurately measuring the volumetric flow rate is shown by a normal distribution of the recovery value with the use of the mean and standard deviation of the volumetric flow rate. A functional A-frame test facility can now be used to test different heat exchanger and fan configurations. By changing the fan, heat exchanger type or area, the performance of the A-frame setup can be analysed for various heat exchanger and fan configurations.

[发布机构] Stellenbosch University