| The aeroacoustic noise reduction of an indoor unit in an air-conditioner has become an important issue and caused more attention at the present time.The purpose of this dissertation is to research the aerodynamic characteristics and aeroacoustics of an indoor unit in an air-conditioner, especially the cross-flow fans. For this purpose, both CFD simulation and experimental investigation are performed on the prototype fan under three different rotational speeds. The flow characteristics are summerized and the analysis of aerodynamic noise includes location of the source and mechanism of source generated and the characteristics of noise propagation. Finally a model for cross-flow fan aerodynamic noise prediction is put forward and verified eventually.The CFD technology is empoyed to simulate the internal aerodynamic flow in a cross-flow fan model. Both two-dimensional and three-dimensional calculation model are used under steady and unsteady condition at three different rotational speeds (800rpm, 1000rpm, 1200rpm). A detailed analysis and summary to the internal flow field are carried out.Such work lays the foundation of aerodynamic noise simulation and noise model.Combined with results of CFD simulation, noise mechanism of the cross-flow fan is analyzed. Using Lighthill's acoustic analogy method and the sound source item analysis in the linear Euler equations, Lilly equation and Powell vortex sound equations, the location of aerodynamic noise source and source characteristics are summerized.The simulation based on the Ffowcs Williams-Hawkings integral equation method and finite element simulate seperately, is carried out in the frequency domain by two-step method. The characteristics of the spectrum, directivity of sound pressure and contours of sound pressure are simulated and analysed at different rotational speed particularly; the sound propagation with the influence of volute is analysised using wave equation finite element method combined with Lighthill's acoustic source terms.In the time domain, generation and propagation of aerodynamic noise are simulated using the two-step method and CAA respectively .Based on the CE/SE method, a computational fluid dynamics and computational aeroacoustics software CFDCA is developed. In response to the characteristics in the cross-flow fan, both the flow and noise propagation are simulated based on the unstructured mesh CE/SE scheme. Using the Navier-Stokes equations as the governing equations, the large eddy simulation (LES) model and sliding mesh model are used in the simulation. By solving Euler equations and no-reflection boundary condition in the far field, the results of aeroacoustics field is obtained. Through analysis, the time-domain noise characteristics of the cross-flow fans are summerized.Experiment is carried out to study the characteristic of aeroacoustics source and propagation of noise caused by cross-flow fan. Pressure fluctuations near the inlet, stabilizer, outlet of rotor and sound-far field are measured with high precision microphones in an anechoic chamber with the blackground noise of 19dB (A). The FFT, time-frequency transform based on FFT and wavelet are performed in order to analize the results at time domain and frequency domain. The aerodynamic characteristic of the cross-flow fans is measured on the own-designed automatic testing instrument according to GB 1236-2000 standards.The calculated charactertics of flux-rotational speed and noise are compared with the results of experiments. Some agreementes and variances are detected and discussed.Based on the characteristics of the flow field in cross flow fan, this paper presents a "two stages through-flow model" to describe the characteristics of its influx. Given on the characteristics of internal flow and aerodynamic noise of the cross flow fans and consulting to centrifugal fans and axial fan aerodynamic noise model, an aeroacoustics model of cross-flow fan is presented. On the basis of the conclusions of this paper, the parameteres of the model are determined according to experimental data of this paper. In order to verify the applicability of the model, a corss flow fan on the reference [165,166] is computed using this model, the comparision between the experimental results and the simulated results show that the model is correct.
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