| Air conditioner(household and comercial used)with fan system, is a rapidly used and big consumption appliance. Not only because this low-pressure system is necessary in the air conditioner and widely applying in the engineering, but also has very good performance in the subject compared with power fan. Firstly, it has very clear peculiarity on construction, designing and inflow system; Secondly, though the wind pressure is low, it has a rapid range on wind scale and needs low noice. It is a very high requirement to the aeroacoustic, so it is difficult to make research to the inflow system of this low-pressure fan system, expecially to the vortex sound phenomena in the inflow and its reciprocity. We have very simple knowledge on it and needs further research. The research shows that, by knowing the construction details and speciality of inflow dimple, and trying to match the dimple and current triangle, can make the fan sytem has good aeroacoustic performance. So, this paper is going to provide the gist for air conditioner fan system characteristic and noice reducing, by simulation and testing on air conditioner wind whirls, air duct structure design, performance and dispersed noice radiance connected system.The basic design method and the test principle of the self designed high accuracy air volume test apparatus are given in detail. The internal flow characteristics in the self designed air volume test apparatus at two kinds of send( the side send/ the up send) under which have multi flow measure scope( the nozzles open to count 9/3/1) are simulated. The result indicates that design can attain the accuracy requests of the flow measure. The side send method has better measurement accuracy than the up send method. Under the same send method the small flow scope measurement accuracy is higher. The tallest measurement accuracy of the side send is in the distance of 1/3-2/3 full capacities. The result indicates that the separating flow at the turning jam the measuring flow passage, and affect the coming flow uniformity relative to the nozzles, and at last affect measurement accuracy of the equipment at the up send. Through comparing the rectification effect at two kinds of send, the rectification mechanism that the orifice plate unit accelerates mainstream and dissipates vortex is discussed. The thesis aims to make a contribution for designing the similar external characteristics service test and further evaluating the equipment precision.This paper analyzed the unsteady evolvemnet process of vortices in cross flow fan at start, speed change ,stop process using CFD simulation.And the distribute characteristic of the eccentric vortex generated in the fan at different work condition was also analyzed in the paper. The flow and evolution mechanism of the eccentric vortex was further disclosured,and the important influx characteristic data was provided for improving the design and the denoise of the fan. The result about the flow mechanism of the eccentric vortex indicated that it was the eccentric vortex brought about the throughflow,but not the occurrence of throughflow formed the eccentic vortex at the start process. At the stop process,the velocity reduced fast from the upperstream to the downstream. The eccentric vortex near the fan inside crossed the blades to get down to shed off ,and it led the cross flow district in the fan extension,then sped the current velocity reduce.At the speed change process,the position of the eccentric vortex almost did not change, it was just represented by the variety of the current velocity in the fan.The result about the distribute characteristic of the eccentric vortex at different work condition indicated that when the outlet pressure increased, the eccentric vortex roll region (the low energy flow body gathered district near the inside fan round) expanded ,and the cross flow region decreased. The position of the core of the eccentric vortex moved toward the casing side,away from the tongue side along the reversed rotational direction of the rotor with the increasing of the outlet load. The position of the core of the core of the eccentric vortex was nearly unchanged under the same outlet background pressure,even though the rotational speed of the rotor was changed.A new variable tip clearance tongue is used in the cross-flow fan of the split type room air-conditioner. Experimental results show that the fan using the new variable tip clearance tongue has a better aerodynamic performance, and has a better noise characteristic. In this paper, the fan using the new variable tip clearance tongue with the skew blades along the span, the fan using the conventional tongue with the skew blades, and the fan using the conventional tongue with the straight blades along the span are contrasted in internal flow, aerodynamic performance and noise characteristics. Internal flow characteristics simulated numerically show the movement of eccentric vortex along the span with the variable tip clearance which is different with the fan using the conventional tongue. The research discusses the mechanism that the variable tip clearance tongue affects internal flow and reduces noise of the fan.A numerical flow analysis and experimental research have been designed to study the internal flow in the multi-blade fan. The researched fan was configured by a new-style inclined volute and a straight volute, respectively.The numerical results showed that the inclined volute could improve the pressure and the velocity distribution characteristic in the tongue clearance of the multi-blade fan. The new designed inclined volute could diminish the clearance vortex that exited near the chassis side of the multi-blade fan.The experimental results showed that the inclined volute could increase the static pressure and volume flow of the multi-blade fan to a certain degree, and the inclined volute could reduce the noise(especially the blade passing by frequency noise) and eliminate the aerodynamic whistle noise of the multi-blade fan. The application of the unequally spaced blades in the multi-blade centrifugal fan is researched in the paper.The modulator approach using sine function for the blades distribution is introduced. Distribute blades the set of even cent in rotation direction, at satisfying the dynamic balance request of blades revolution, at the same time, attain to good effect to make the passage noise decrease using the unequally spaced blades distribution. Four ways of the blades distribution are compared in the paper,and it indicates that using the unequally spaced blades has the effcet for noice reducing with the constant wind rate.Try to use the diagonal fan in the air condition outdoors machine. Considering the mechanism which the overall matching of the diagonal rotor and the volute increase efficiency and decrease loss, the volute model lines are designed according to the free flowing track. Through the internal flow matching analysis, the symmetry air-inlet style and the asymmetry air-inlet style of the diagonal rotor to the volute are compared. It is indicated that the asymmetry style has a better static pressure distribution in the volute, and avoids the intermediate layer separation due to the double direction vortex, reduces the dissipation loss, and improve external characteristic, as the single vortex in the asymmetry style replaces the double direction vortex in the symmetry style. Leading edge skewed-swept diagonal rotor can better improve the stall characteristic in low flow rate area and expand the surge margin, compared with conventional diagonal rotor. It can also efficiently restrain the conglomeration of low-momentum fluid near the wall region and reduce loss of secondary flow by sweeping and skewing the blade properly. Diagonal fans' overall performances are improved by using leading edge skewed-swept blades.Introduced the research of some air duct design resolving 'the heat jumps to stop' problem in the outdoors machine. Mainly involve the problem-solving influence with improving the air ducting and the mesh enclosure. The experimental results and the compute results show that the structure form of the air ducting and the mesh enclosure have the influence not only for the send straightness , but also for the noiseses. The extreme limit temperature of 'the heat jumps to stop' can be promoted with improving the air ducting and the mesh enclosure.It is supported by the National Natural Science Foundation of China (No: 50676035 ) and the Doctorate Foundation of the Ministry of Education(No: 20060487036)... |
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