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Reversible axial fans are used to achieve air (gas) flow in both directions. An axial fan only has an impeller that can achieve the reverse flow by changing the direction of the impeller rotation. In order to obtain the same performance for both directions, the profiles of the impeller blades should be completely symmetrical, in the shape of the ellipse. This paper presents the design and performance for a reversible axial fan with blades that have a slightly doubly curved profile. The shape of the profile, whose design is shown here, was previously obtained on the basis of the numerical simulation in the profile cascade. For the experimental tests, an axial reversible fan model with double curved profiles of the blades was made. Fan performance was obtained by testing a fan for three blade positions on a standard test installation. The performance curves were compared with the performance of the reversible axial fan blades with straight profiles. The fan with doubly curved profile blades achieved a greater increase in pressure and flow than the fan with straight profiles, with approximately the same efficiency. Low pressure axial reversible fans are used in drying chambers for wood and such a design can achieve higher drying efficiency. [ABSTRACT FROM AUTHOR]

This paper presents the fabrication and performance characterization of miniature axial fans that are developed using 2D blade profiles. 12 prototypes, with an outer diameter of 5 mm, having different blade angles and blade profiles were fabricated using UV photolithography with SU-8 as photoresist. Tests were conducted at 3 different speeds to examine the applicability of similarity laws. The results show that cambered profiles generated much higher pressure and flow rate as compared to a flat plate profile. For flat plate profiles, a maximum pressure of 0.55 Pa and a flow rate of 9.9 cm/s are generated with a blade angle of 42° when the fan is operating at 20,000 rpm. This is much lower than that obtained by cambered profiles where a maximum pressure of 1.15 Pa and a flow rate of 14.6 cm/s are generated with a blade angle of 60°. The effects of increasing blade number and blade angle have a positive effect on the flow rate delivered and pressure generated but the effects of increasing blade number is more effective in enhancing fan performance. The results also show that dynamic similarity is observed for rotational speeds of 15,000 and 20,000 rpm. [ABSTRACT FROM AUTHOR]

A parametric study on the geometry of an impeller in a forward-curved blades centrifugal fan for residential ventilation has been carried out in this work. Numerical analysis of a forward-curved blades centrifugal fan was carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. A validation of numerical results was conducted by comparison with experimental data for the pressure and efficiency. The impeller separated by an annular plate was employed, and the annular plate height and the angle between the upper and lower impellers were selected as the geometric parameters to investigate their effects on the efficiency of the forward-curved blades centrifugal fan. Additionally, the impeller geometry having the highest efficiency was tested with the number and exit angle of blades. The results show that the impeller with properly installed annular plate improves the aerodynamic performance of the forward-curved blades centrifugal fan. [ABSTRACT FROM AUTHOR]

The effect of the pitch of the blades in an axial fan with an UK-2M impeller 2.8 m in diameter on the characteristics of a horizontal three-section air cooler (AC), the six-tier heat-exchange sections of which consist of bimetallic finned tubes with rolled aluminum fins (tube-finning factor of 20.4; medium cooled – gasoline) is analytically investigated. It is found that for the same power consumed by the fan drive, the pitch of the fan blades in the interval from 15 to 25° will not affect the thermal flux of the AC. Recommendations are given for selection of energy-expedient pitches of the blades during AC operation, and also for thermal analyses of units under design. [ABSTRACT FROM AUTHOR]