| Indoor unit of air-conditioning consist on cross-flow fan(CFF) and heat exchanger. The aerodynamic and aeroacoustic properties of indoor unit have become the more and more important issues recently. Due to its unique geometry, CFF is widely used in indoor air-conditioning systems. However, the internal flow structure of CFF is so different from other types of fan, such as eccentric vortex inside the impeller. The eccentric vortex structure makes the efficiency of cross-flow fan system greatly reduced. Therefore, it is of great value for not only the engineering application but also the theoretical research to investigate the internal flow structures, especially in the theory of origin and development of the eccentric vortex. There is a random noise generated when the air across the heat exchanger. This noise has direct influence on air-conditioned indoor unit comfortable. Thus, it is necessary to investigate the generated environment of the noise and the mechanism, and provide reliable theoretical foundation for the design of air conditioner indoor unit.The research object in the present study is the CFF of an indoor unit of airconditioning. The investigation of rule of eccentric vortex is the basis of the study on experimental and CFD simulation when the CFF is started and developed. According to the results, the control method of energy losses of eccentric vortex has been carried out, named inlet guide vanes(IGVs) which are located near the tongue. The eccentric vortex energy loss can be controlled effectively and the performance of CFF can be improved by adjusting the angle of IGVs. At the same time, the research object in the present study is the heat exchanger of an indoor unit of air-conditioning. The generated environment has been measured by aeroacoustic experiment when the flows cross the heat exchanger. The mechanism has been analyzed by hot experiment and CFD simulation. According to the results, the model of the Hill-hill noise can be established which can fit to the noise of flow cross the heat exchanger.The theory of eccentric vortex is the key of the cross-flow fan theoretical. In present study, the image of eccentric vortex is accurately captured by flow visualization experimental method during the CFF is start and development. At the same time, the commercial software FLUENT have been employed to simulate the unsteady internal flow of the CFF. Compared with the flow visualization results, the stabilized reason of eccentric vortex has been carried by mass and energy conservation. The influence of eccentric vortex is analyzed by using vortex dynamics theory when the flow back to the blade and the shedding vortices can be generated by flow separation. According to these results, the theory of eccentric vortex is carried out completely.In present study, the method of adjustable inlet guide vanes which were installed near the tongue has been developed based on the theory of eccentric vortex. The flow separation can be reduced effectively by IGVs when the flow back in the blade. Thus, the region of eccentric vortex is decreased, the region of through flow is increased, and the performance of the cross flow fan can be improved by IGVs. The appropriate angle of IGVs is determined by the total pressure, relative to the total pressure, torque coefficient and other parameters using CFD simulation. The simulation results are verified by aerodynamic performance of experimental. Compared with the prototype, the results show that the power consumption with IGV can be reduced by about 2% in the constant flow condition.This paper focuses on the random noise of the flow through the heat exchanger. The investigation of generated environment is basis of the study on aeroacoustic experiment. The noise of characteristic is determined by velocity of flow, angle of flow, layers of heat exchanger, geometry of fin surface and the cavity number. The type of noise is determined by the relationship between the velocity of flow and frequency as an acoustic noise. The mechanism has been analyzed by hot experiment and CFD simulation. According to the results of experiment and CFD simulation, the acoustic model of Hill-hill noise is carried out which fit to the heat exchanger noise. The Hill-hill noise of the cavity shear layer self-oscillation frequency prediction formula is established by experimental data. The generated environment and mechanism of Hill-hill noise is analyzed. |
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