In order to improve the efficiency and decrease the noise level of centrifugal blowers at the same time, we have developed a “slit diffuser” which has a slit structure that connects the flow passages ...of neighboring diffuser vanes. We investigated the influence of slit structure in terms of performance, internal flow field, as well as noise level. We obtained the following conclusions. Compared with non-slitted diffusers, for the diffusers with slits, the stagnation area generated from the diffusers decreases near the slits and there is less diversion of the mainstream flow. Owing to the flow that goes through the slits from the pressure side to the suction side, the stagnation inside the diffuser is improved and the adiabatic efficiency increases by 0.8%. Compared with non-slitted diffusers, it is possible with slit diffusers to reduce the blade-passing frequency noise and to suppress the acoustic resonance.
In general, the blowers mounted on the wind mills are designed to supply cooling effect to the power generator for the extraction of heat, but it is noticed that the axial blowers currently deployed ...in the windmills tend to produce insufficient cooling effect and generate high level of noise. Thus, sufficient cooling and low noise level are key parameters in the design of blowers. This study of forward-curved centrifugal blower focuses on improving the performance of an industrial blower and implementing the performance characteristics of the system derived from high-fidelity three-dimensional CFX analyses. The objective of the present study is to estimate the aerodynamic and aero acoustic parameters like mass flow rate and noise level of axial blower and centrifugal blower. The blowers are modelled and analysed using Ansys CFX solver based on industry requirements. It is observed from the analysis that centrifugal blower is more preferable to achieve sufficient cooling effect with low noise level.
This study experimentally investigates the unstable flow in a five-stage centrifugal blower with inlet guide vanes (IGVs) upstream of the first stage. Performance characteristics of the blower were ...obtained under three IGVs opening conditions. Measurements of the unsteady pressure were performed using six high-response pressure transducers. To distinguish rotating stall from surge, three of these transducers were located thirty degrees apart in the circumferential direction at the vaneless space upstream of the diffuser vane. Three types of pressure fluctuation in the low flowrate region were confirmed. The first one occurred in the positive slope region of the total-system head curve with the largest amplitude and the lowest frequency under the full opening condition of IGVs. The second one was the spike-like fluctuation propagating in the circumferential direction in the vaneless space. The last one appeared under the partial opening condition of IGVs with smaller amplitude and higher frequency than those of the first one. It was confirmed that this pressure fluctuation oscillated at the same phase in the vaneless space and occurred even in the steeply negative slope region of the total-system head curve under the minimum opening condition of IGVs. It was considered that the first one was deep surge and the second one was rotating stall. The last one was considered to be mild surge. Under the minimum opening condition of IGVs, the slope of the head curve of the first stage becomes steeply negative by prewhirl. This negative slope stabilizes the total system of the blower. By contrast, the slope of the head curve of the other stages becomes positive in the low flowrate region. This positive slope destabilizes the total system of the blower. Therefore, even if the total-system head curve keeps a steeply negative slope, the system operating point is considered to oscillate slightly, corresponding to mild surge situation, due to these stability balances.
The effect of inlet radius and bell mouth radius on flow rate of centrifugal blower were numerically simulated using a commercial CFD program, FLUENT. In this research, a total of eight numerical ...models were prepared by combining different values of bell mouth radii and inlet radii (the cross section of bell mouth was chosen as a circular arc in this research). The frozen rotor method combined with a realizable k-epsilon turbulence model and non-equilibrium wall function was used to simulate the three-dimensional flow inside the centrifugal blowers. The inlet radius was then revealed to have significant impact on flow rate with the maximum difference between analyzed models was about 4.5% while the bell mouth radius had about 3% impact on flow rate. Parallel experiments were carried out to confirm the results of CFD analysis. The CFD results were thereafter validated owning to the good agreement between CFD results and the parallel experiment results. In addition to performance analysis, noise experiments were carried out to analyze the dependence of sound quality on inlet radius and bell mouth radius with different flow rate. The noise experiment results showed that the loudness and sharpness value of different models were quite similar, which mean the inlet radius and the bell mouth radius didn’t have a clear impact on sound quality of centrifugal blower.
Vehicular air conditioning systems are directly affected by the ducts and fans of the ventilation system. This paper presents an experimental study of the influence of the geometry of the air ducts ...and fans on the performance of an automotive air conditioning system. The flow rate, pressure drops and power requirement demand were evaluated for different geometrical and operational conditions. A test bench was used that constituted the air-box of an automotive air conditioning system, composed of the air ducts, the centrifugal blower, and an instrumental panel. Two different geometrical fans and ducts were tested. The experimental results showed a great potential for performance improvement. Significant gains were achieved for the pressure drop, flow rate and air distribution at the branch ducts with the modifications implemented. The experimental results also showed that the power consumption slightly increased with the considered modifications.
While performing numerical simulations, it is general industrial practice to neglect the clearance gap between the impeller and the inlet duct. In the present work, the effect of clearance gap on the ...performance of an industrial sized centrifugal blower is simulated for two volutes of width ratios and various flow coefficients. The results show that the clearance has a positive effect at low mass flow rates. This is observed in the pressure rise (1.3%) as well as in efficiency (0.7%). At higher mass flow rates, it has a negative effect with a drop in efficiency of 1% and pressure drop of about 1.4%. The effect of clearance gap on volute with higher width ratio is smaller when compared with the volute with smaller width ratio.
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