In this paper, the aerodynamic and mechanical design of a centripetal-flow Fan has been undertaken at a particular thermal environment in which the working fluid behaves as an ideal gas. A preliminary design (one-dimensional analysis) study was conducted at first, based on which three-dimensional modeling and optimization were subsequently applied to the design of the centripetal-flow Fan. The aerodynamic performance of the designed Fan and its operating characteristics in different working conditions were assessed by means of numerical simulations. Our results suggest that isentropic efficiency and pressure ratio of the centripetal-flow Fan at design operating conditions can reach 81. 14% and 1. 0833, respectively, which satisfy the requirements for Fans in commercial and industrial applications. From the Fan performance curves, it is found that as the mass flow rate increases, the efficiency of the Fan operating at the designed rotational speed first increases and then decreases. There exists an optimal mass flow rate which leads to the maximum efficiency of the Fan. Similarly, the Fan pressure ratio first increases as the mass flow rate increases, attains a maximum value and then decreases as the mass flow rate further increases. At off-design rotational speeds, although the Fan characteristic curves show the same tendency as those observed at the design condition. Moreover, the Fan characteristic curve becomes steeper with an increased rotational speed, which means that the variations of isentropic efficiency and pressure ratio with change in mass flow rate become much greater. The results of our present study confirm the feasibility of using the centripetal-flow Fan for various industrial applications.

Synthetic jets, whose size and weight can be reduced easily, have become an attractive alternative to continuous jets. Many experimental and numerical studies have been conducted on synthetic jets to investigate their fundamental flow characteristics, including jet structure, for applied research such as boundary layer control and enhanced fluid mixing. However, few studies have focused on fluid transportation devices using synthetic jets as a driving source. Therefore, several issues concerning fluid transport characteristics still need to be resolved. In addition, although optimum operation of devices using synthetic jets is essential for their practical use, few studies have focused on this issue. The present study experimentally demonstrates the influence of the dimensionless stoke L on the performance characteristics of a synthetic jet Fan under Reynolds number Re = 1800 and the same Fan geometry; here, the stroke l is nondimensionalized by the primary slot width b. Furthermore, numerical simulations are conducted to complement the experiment. Velocity and pressure measurements are performed using a hot-wire anemometer, differential pressure manometer, and pressure transducer. The influence of the dimensionless stroke L on the performance/efficiency curves, static pressure distribution on the duct surface, and unsteady flow characteristics are investigated. Moreover, the flow field inside the duct is observed through numerical simulation. The results show that the performance characteristics and pressure recovery process depend on the dimensionless stroke L, and an optimum range of dimensionless stroke L exists for operation.

This paper includes parametric study and optimization of non-linear ceiling Fan blades by combining the techniques of Design of Experiments (DOE), Response Surface Methods (RSM) and Computational Fluid Dynamics (CFD). Specifically, the nonlinear (elliptical) planform shape of ceiling Fan blade is investigated in conjunction with blade tip width, root and tip angle of attack. Sixteen cases are designed for three blade ceiling Fan using two level full factorial model. The flow field is modeled using Reynolds-Averaged-Navier-Stokes approach. The performance variables used to formulate a multi-objective optimization problem are volumetric flow rate, torque and energy efficiency. Response Surface Method is used to generate the optimized design for non-linear ceiling Fan blade profile. The results reveal that the interactions between the design variables play a significant role in determining the performance. It is concluded that the nonlinear forward sweep has a moderate effect on response parameters.

The present investigation is conducted to study the effect of Gurney flap configuration on the performance of a centrifugal Fan at different Reynolds numbers. Gurney flaps of different configurations, such as angle, quarter round and half round corresponding to a nominal height of 1. 2 mm (1. 94% of the impeller blade spacing at tip) height are attached to the pressure surface of the centrifugal Fan impeller blade tip. performance tests are carried out on the centrifugal Fan with a vaneless diffuser at five Reynolds numbers viz. 0. 30, 0. 41, 0. 55, 0. 69 and 0. 80×105 based on the impeller tip speed, impeller blade exit height and kinematic viscosity, both with and without Gurney flaps. From the performance curves it is found that Fan performance improves significantly with Gurney flaps at low Reynolds numbers and improves marginally at high Reynolds numbers. Gurney flap of angle configuration of height as small as 1. 94% of the impeller blade spacing at tip increases head coefficient by 5. 2% and increases the volume flow rate across the Fan by 5. 4% at the lowest Reynolds number of 0. 30×105. Even though there is increase in both head and flow coefficients with other Gurney flap configurations (quarter round and half round), they are always less than that for the angle Gurney flap. The effect of Reynolds number on the performance curves is found to be negligible with Gurney flaps, whereas the effect of Reynolds number on the performance curves of the impeller without Gurney flap is found to be considerable. Additional experiments conducted with Gurney flaps of two configurations, viz. angle and quarter round, with a larger height of 2. 5 mm (4. 05% of the impeller blade spacing at tip) attached on the pressure surface of the centrifugal Fan impeller blade tip have shown that the performance of the Fan with quarter round GF is better than the performance of the Fan with angle GF.

A better understanding of the flow field is crucial for improving the design of a turbomachine. In this work we investigate the performance of voluteless centrifugal Fan rotors. The study includes two parts: experiments and numerical simulations through Computational Fluid Dynamics (CFD) techniques. Our test system allows the analysis of the flow behavior of centrifugal Fan rotors maintaining the meridional shape without making substantial changes to their internal structure, but with different blade shapes, sizes, and blade numbers. To avoids irregular interference with the rotor flow from external components such as the collector a radial channel composed by two parallel discs was placed concentrically on the rotor axis at its outer periphery with special interest in measuring flow characteristics at the rotor outlet with a reliable accuracy. As an application case a typical centrifugal Fan rotor with ten blades of single curvature in the circular arc shape has been investigated. Two types of measuring systems were used: one, with an aerodynamic probe located in the centrifugal rotor outlet and, the other, with a load cell for measuring the rotor shaft power. A comparison of the results by these two measuring arrangements shows some important characteristics, such as the phenomenon of the flow recirculation within the rotor. The experimental performance curves related to non-dimensional flow such as the slip factor, and pressure coefficient, revealed good matching with numerical simulations, highlighting the remarkable reliability of our experimental setup.