Internal Flow Mechanism And Noise Analysis For Cross-flow Fan In Air-conditioning

With the improvement of living standards, people have raised a much higher demandfor the quantities and performance of air-condition, it is also reflected on its flow and itsnoise. Because the structure of the cross-flow fan is very simple and the flow that it blowout is uniformed and its noise is very low, cross-flow fan are often used in air conditioning,but because there is a eccentric vortex existing in the fan, people can not design thecross-flow fan by using the similarity method, the fact has made the people design thecross-flow fan by depending on the engineering experimental data, it lead to the high cost.The internal three-dimensional unsteady flow field of the cross-flow fan has beencalculated by a commercial CFD software in this paper, and the aero-acoustic noise waspredicted by the FW-H equations. It has proved that this method is feasible by contrastingthe simulated results and the experimental results. The internal three-dimensional unsteadyflow field and the aero-acoustic noise field of a improved impeller has been simulated, itcan provide a basis for the model design. The works contain aspects below:(1)The internal flow numerical simulation of the cross-flow fan: Conducting numericalsimulations of unsteady flow field to seven different rotate speeds of cross-flow fan byusing the large eddy simulation (LES), the internal flow distribution details and theevolution of the eccentric vortex in different speed have been showed, and the aero-acousticnoise was predicted by the FW-H equations, the results have been showed. And thesimulated results were compared with the experimental results, the difference between thetheoretical prediction and the experimental results has been analyzed.(2)The cross-flow fan have been designed by using the wing first wheel design method,and revised by using the engineering experimental value. We have designed four groups ofimpeller model and optimized these impeller models by using the numerical simulationmethod, we have get a suitable impeller model, and simulated the internal flow field andaero-acoustic field by using the above mentioned methods, the analysis of the simulatedresults have been showed and the characteristic performance curve has been forecasted.(3) The new designed model prediction results show that its rated flow is6%higherthan the rated flow of unimproved impeller model. The forecasted noise level is7.77lowerthan the original one. The new designed impeller model can meet the technical requirements. The methods and results used in this paper provide a basis for the furtherdesign of cross-flow fan.