The effects of the inlet position of blade on the performance of a centrifugal impeller are numerically investigated. The inlet position of the blade can be determined by the outer diameter, the leaning angle of the blade inlet, the shroud and hub angular momentums specified at the blade inlet. It is found that the flow fields of the optimal impeller are obviously superior to those of the impeller whose blade leading edge was installed at impeller eye. The range analyses reveal that angular momentum specified at the inlet hub is the least important factor in affecting the efficiency of impeller, while the outer diameter of blade leading edge plays the most important role in determining the pressure ratio.

View full abstract

In order to investigate the formation of the rotating stall in diffuser of pump-turbine in pump mode, the unsteady flow with radial rotating characteristics before the occurrence of rotating stall are investigated by detached eddy simulation. The results indicate that the unsteady flow patterns which occur in the return channel both at full and part load conditions contain two periodical disturbances with frequencies St≈0.042 and St≈0.085, and the Strouhal number St is frequency normalized by blade passing frequency of impeller. These periodical disturbances not only influence the pressure field but also cause rotating characteristics in diffuser channels. One is composed of 4 cells propagating at 0.073 times of impeller rotating speed. The other one is made up of 3 rotating cells with 0.2 times of backward impeller rotating speed. Meanwhile, there are two radial rotating characteristics which contribute the spectra peak at blade pass frequency in diffuser. One is at the inlet of diffuser propagating at impeller rotating speed with 7 cells, and the other one contains 4 cells with about 1.75 backward impeller rotating speed.

View full abstract

In this paper, the rotor and the volute of the squirrel-cage fan with dual inlet were optimized to improve its aerodynamic performance. The blade inlet angle, blade exit angle and diameter ratio of the impeller were chosen as optimization variables using the response surface methodology (RSM) to improve the total pressure. Furthermore, another three optimization variables were adopted on the basis of previous optimum results, which are the width of impeller, the location of the impeller annular plate and the location of cutoff respectively. The simulation and experimental results show that the total pressure of the optimal model has been greatly improved without noise increase in comparison with the original model.

View full abstract

This paper presents two optimized designs of a commonly-used fluid distribution manifold having one entrance and six exits. Numerical simulations were carried out to optimize the dimensions and mechanisms of these proposed designs for the sake of enhancing the uniformity of fluid distribution amongst the exits and reducing the formation of dead zones inside the manifold cavities. Particularly, to make the fluid distribution amongst exits more uniform, this study explored the relationship between entrance diameter and exit diameter. Furthermore, in order to reduce dead zone formations inside the manifold whilst still maintaining uniform fluid distribution, a conical cavity was designed. After that, blockers were designed to replace some exits, permitting a variable number of fluid distribution manifold exits, depending on the specific application. Both designs were found to be able to improve flow uniformity and dead zone reduction compared to the original commonly-used fluid distribution manifold, with the central-feeding distributor performing slightly better than the lateral-feeding distributor overall. From the perspective of manufacturing, each of these two fluid manifolds was made of two pieces with glue and rubber O ring used respectively as the bond between separate pieces. Preliminary experiments with these devices suggest similar results to those from the numerical studies. Based on real application requirements and limitations, the different fluid manifold designs with tunable dimensions can be utilized in various mechanical or biochemical devices to distribute fluid equally amongst several parallel components.

View full abstract