Strength Numerical Analysis And Structure Improvement Design Of Super-large Fan Pipes And Test Cabin For Aviation Engines

Super-large fan pipes and test cabin are important components of the wind tunnel system for testing aviation engines.Because of the complex structure and varied working conditions with the loads including internal pressure,external pressure,fatigue and earthquake loading,design by rules is hard to precisely design the wind tunnel system,let alone the fatigue analysis and design.In this paper,numerical analysis of super-large fan pipes and test cabin was performed with ANSYS and some unreasonable structures were improved.Main contents and conclusions are as follows.(1)Finite element models for the super-large fan pipes and test cabin were established with ANSYS,and strength assessment under different loading cases was performed conforming to JB4732-1995(confirmed in 2005)Steel Pressure Vessels----Design by Analysis Code.Results showed that the strength of the super-large fan pipes meets the strength requirements.Except the strength of the connection of prechamber,baffle plate and extension nozzle on the prechamber,all other parts on the cabin also meets strength requirments with a large safety margin.(2)Six different structures were proposed to improve the structures of the connection of baffle plate,head and extension nozzle of the prechamber.Compared the six structures,it was found that if the structure of cicular arc baffle plate were adopted,the strength could satisfy the requirement even if the thickness of the cicular arc baffle plate and extension nozzle on the prechamber were thinner in some extent.(3)Fatigue analysis for the super-large fan pipes and test cabin was conducted as the equipments would undertake alternating loads.The cumulative fatigue damage factors were calculated according to the fatigue design curve,and the values of corner pipe,stable pipe,prechamber and cabin are 0.5196,0.0761,0.003 and 0.6396,respectively,meaning that the super-large fan pipes and the test cabin could meet the requirements of fatigue strength.(4)Modal analysis was conducted to calculate the natural vibration period of the test cabin and the seismic horizontal acceleration was obtained according to the seismic responding curves.Analyzing the test cabin under the earthquake condition showed that the strength of the equipment was satisfied.(5)Stability analysis of super-large fan pipes and test cabin under external pressure condition was performed,Results showed the buckling load coefficients of corner pipe,stable pipe and test cabin are 48.56,18.52 and 4.13.In order to increase the buckling load coefficient to more than 7 as specialy required by the user,stiffen ribs are added on the test cabin and after that,the buckling load coefficient is 15.29.(6)The design of the door of the test cabin includes many stiffen ribs and proves to be very conservative.In this paper,the door of the test cabin was specially concerned by conducting light-weight design after studying the influence of the thickness of the door,the height?the thickness and distributions of the stiffen ribs on the stability of the door.It is found that the total weight of the door was reduced by 44.32%with the improved structure.