Study On Aerodynamic Performance Of Axial-flow Impeller For Axial-flow Pneumatic Extinguisher

Axial-flow pneumatic extinguisher is a kind of new portable extinguishers and is different from the existing centrifugal pneumatic extinguisher. Axial-flow impeller is a core fire-fighting components of axial-flow pneumatic extinguisher. Therefore, the aerodynamic performance of axial-flow impeller will have a direct effect on the fire-fighting performance of axial-flow pneumatic extinguisher. This study is mainly aimed at experimental study and CFD numerical simulation of axial-flow impeller's aerodynamic performance about axial-flow pneumatic extinguisher and the results provide a theoretical basis for the design of high-efficiency axial-flow pneumatic extinguisher.Main contents and conclusions are as follows:1.According to fire-fighting fan performance requirements provided by the national standard GB/T 10280-1999《portable pneumatic extinguishers-technical specification》such as outlet flow volume, and considering the design idea of future axial-flow pneumatic extinguisher, the axial-flow fire-fighting fan aerodynamic performance test device was designed and manufactured. The free flow of driven air about high-speed rotating axial-flow impeller of the test device under laboratory conditions can be simulated. Axial-flow fire-fighting fan aerodynamic performance test device verifies aerodynamic performance of axial-flow impeller in the axial-flow fan and axial-flow fire-fighting fan respectively through the removable cone-shaped jet duct.2.The aerodynamic performance tests for axial-flow fan composed of the number of different leaves (Z=5,6,7) and blade angle (30°,34°,38°) of axial-flow impeller were carried out. The experimental results indicated that:When the blade angle of axial-flow impeller is 38°, the flow volume of No.5 axial-flow fan which the blade number Z=6 is 1406.1m3/h,closest to the design requirements, total pressure is 438.35Pa, power is 0.501kw, total pressure efficiency is 34.15%,basically meets the aerodynamic performance requirements of fire-fighting fan, and shaft power is much smaller than that of a portable pneumatic extinguisher.3. Numerical simulation results of axial-flow fan internal flow field showed that:when the blade angle of axial impeller is 38°, the outer edge speed of No.5 axial-flow fan which the blade number Z=6 is greater, low-speed area of hub outlet is smaller, outlet velocity of blade body is larger, rotation thrust is greater, numerical simulation results are consistent with aerodynamic performance test results.4.Axial-flow fire-fighting fan was formed after the cone-shaped jet duct was installed in the axial-flow fan, the aerodynamic performance tests for axial-flow fire-fighting fan composed of the number of different leaves (Z=5,6,7) and blade angle (30°,34°,38°) of axial-flow impeller were carried out. The experimental results indicated that:When the blade angle of axial-flow impeller is 38°, the flow volume of No.5 axial-flow fire-fighting fan which the blade number Z=6 is 1400.3m3/h,closest to the design flow volume, total pressure is 584.61Pa, power is 0.45kw, total pressure efficiency is 50.44%, integrated aerodynamic performance is well, basically meets the aerodynamic performance requirements of fire-fighting fan, and shaft power is much smaller than that of a portable pneumatic extinguisher. Therefore, the optimum blade angle of axial-flow impeller which is applied in the axial-flow fire-fighting fan is 38°, the optimum blade number is 6.5. Numerical simulation results of axial-flow fire-fighting fan internal flow field showed that: compared with the axial-flow fan, the function of conical jet duct in the axial-flow fire-fighting fan is to improve the speed and accelerate the formation of the air jet. When the blade angle of axial impeller is 38°, the flow volume of No.5 axial-flow fire-fighting fan which the blade number Z=6 is greater, refluence area of hub outlet is smaller, power consumption is lower. The internal velocity vector of conical jet duct is larger, distributed intensively, jet outlet velocity is higher, numerical simulation results are consistent with aerodynamic performance test results.