Abstract:The use of high-speed radial impellers is very common in blowers for industrial application. It is also very common to manufacture these impellers using circular arc blades. The design process as well is almost always based on former impeller series and experimental data available. In this work, a method is presented to improve the efficiency of radial impellers with a combined analytical and numerical method. This method is based on an extended analytical formulation of the flow in radial impellers, allowing optimizing efficiency in the design stage. It is complemented by the mathematical implementation of a well-known qualitative principle of efficiency optimization according to Carnot. Finally, the torque-speed characteristic of the motor is included in the design stage. The blade shapes are computed using an inverse method. The design is then validated by means of computational fluid dynamics (CFD) computation with a commercial solver. Finally, a prototype was built and measurements were carried out in a test rig. It is also shown that the design method provided very good predictions leading to an efficiency increase of 13 per cent and a maximum flowrate increase of 11 per cent. The design point was also met. It is also shown that the numerical computations and measurements are in good agreement. An analysis of the CFD results is also presented, giving an insight view into the substantial flow information within the old and the new impellers. The method presented is a combined analytical and numerical method suited to design high-efficiency radial impellers considering also the torque-speed characteristic of the motor without the need of a previous impeller series or knowledge of experimental data.
Acoustics 08 Paris
7031With increasing number of electrical devices, e.g. air conditioning systems, used in homes and offices, noise pollution is becoming a more and more relevant topic. A large amount of this noise is generated by turbulent flows and laminar flows at leading and trailing edges, where mainly tonal noise is generated. The objective of our contribution is to simulate the generation as well as the propagation of noise inside of rotating devices. The acoustic source terms are obtained from the fluid dynamics solution by using Lighthill's acoustic analogy. The acoustic domain is decomposed into a rotating part and a fixed part. The coupling between these two parts is enforced at their interface by a mortar finite element method, which uses Lagrange multipliers in order to "glue" the geometrically independent parts together. The mortar method takes into account the movement of the rotating part by a moving nonmatching grid, that is recomputed at each time step.
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