Optimal Design Of Low Noise Marine Centrifugal Fan Based On Blade Outlet Angle

Marine centrifugal fan is the core of marine ventilation system,with large energy consumption and high noise.Centrifugal fans directly affect energy conservation of ships and prevention of noise pollution.Improving fan efficiency and reducing fan noise have become the key technologies for the development of shipbuilding industry.In this paper,the method of computational fluid dynamics is used to optimize the design of marine centrifugal fan to meet the requirements of cabin ventilation,installation space and noise.The internal flow field and noise characteristics of fans with different blade outlet angles are studied by fan optimization model,which provides theoretical and technical support for the design of high efficiency and low noise centrifugal fans.Based on the fan design requirements,the aerodynamics sketch design of CT6-35 centrifugal fan was carried out based on the noise control foundation of model machine and the fan design theory.Based on the numerical simulation and experimental verification of the model machine,the optimization design of the fan is carried out by using the numerical calculation method.The blade inlet angle,blade outlet angle,impeller outlet width and impeller inlet diameter were selected by sensitivity analysis.Then,genetic algorithm is used to optimize structural parameters which have a greater influence on the performance of the structural parameters of the fan(outlet blade angle,impeller outlet width),the optimized fan blade outlet angle is 62 °,the impeller outlet width is 45 mm.Compared with the original design,after optimization,the matching between impeller and volute is increased,the area of vortex in the blade passage is reduced,the flow separation is weakened,and the stability is improved.Under the premise of full pressure standard and noise standard,the fan efficiency reaches 81.2%,which is 3.4 % higher than the original design.Through steady and unsteady numerical calculations,the effects of blade outlet angle on flow loss,vortex flow characteristics,pressure pulsation and sound field of dipole source in fan are studied by numerical calculation of flow visualization,FFT and acoustic harmonic boundary element methods.The results show that with the increase of blade outlet angle,the vortex in the passage expands to other passages along the direction of impeller rotation,the area and strength of the vortex increase,the flow loss caused by the vortex and the energy loss in the process of hydrostatic and static pressure conversion in the volute basin are the main reasons for the decrease of fan efficiency.At the same time,the pressure pulsation in the volute area and the increase of the noise from the dipole source are not conducive to the noise control of the fan.When the blade outlet angle is 72°,the pressure pulsation in the volute basin is about 2 times that when the blade outlet angle is 52 °.The impeller rotating dipole source noise has little influence on the blade outlet angle,the volute wall dipole source noise increases with the increase of the blade outlet angle.