Pile-slab structure roadbed is a new form of ballastless track for high speed railway. Due to lack of corresponding design code, based on the analysis of its structure characteristics and application requirements, it ...Pile-slab structure roadbed is a new form of ballastless track for high speed railway. Due to lack of corresponding design code, based on the analysis of its structure characteristics and application requirements, it is proposed to carry out load effect combination according to ultimate limit state and serviceability limit state, and the most unfavorable combination of each state is chosen to carry through design calculation for pile-slab structure. Space model of pile-slab structure can be simplified as a plane flame model, by using the orthogonal test method, and the design parameter of pile-slab structure is optimized. Moreover, based on the engineering background of Suining-Chongqing high-speed railway, the dynamic deformation characteristics of pile-slab structure roadbed are further researched by carrying on the indoor dynamic model test. The test results show that the settlement after construction of subgrade satisfies the requirement of settlement control to build ballastless track on soil subgrade for high-speed railway. Slab structure plays the role of arch shell as load is transmitted from slab to pile, and the vertical dynamic stress of subgrade soil is approximately of ＂K＂ form distribution with the depth. The distribution of pile stress is closely related to soil characteristics, which has an upset triangle shape where the large dynamic stress is at the top. Pile compared with soil shares most dynamic stress. Pile structure expands the depth of the dynamic response of subgrade has limited effect on dynamic response. These results can provide subgrade. and improves the stress of subgrade soil, and the speed of train scientific basis for pile-slab structure roadbed used on soil展开更多
With the increasing demand of higher travelling speed,a new streamlined high-speed maglev train has been designed to reach a speed of 600 km/h.To better capture the flow field structures around the maglev train,an imp...With the increasing demand of higher travelling speed,a new streamlined high-speed maglev train has been designed to reach a speed of 600 km/h.To better capture the flow field structures around the maglev train,an improved delayed detached eddy simulation(IDDES)is adopted to model the turbulence.Results show that the new maglev train has good aerodynamic load performance such as small drag coefficient contributing to energy conservation.The main frequencies of aerodynamic forces for each car have a scattered distribution.There are two pairs of counter-rotating large vortices in the non-streamlined part of the train that make the boundary layer thicker.Many high-intensity vortices are distributed in the narrow space between skirt plates or train floor and track.In the gap between the train floor and track(except near the tail car nose),the main frequency of vortex shedding remains constant and its strength increases exponentially in the streamwise direction.In the wake,the counter-rotating vortices gradually expand and reproduce some small vortices that move downward.The vortex has quite random and complex frequencydomain distribution characteristics in the wake.The maximum time-averaged velocity of the slipstream occurs near the nose of the head car,based on which,the track-side safety domain is divided.展开更多
In this paper a numerical investigation has been presented on the stall mechanism of a highly loaded Single Stage Low Speed Fan designed for the research test facility to be installed at North Western Polytechnic Univ...In this paper a numerical investigation has been presented on the stall mechanism of a highly loaded Single Stage Low Speed Fan designed for the research test facility to be installed at North Western Polytechnic University (NWPU) Xi’an, China. The results presented are for the design point, near stall and just stall operating conditions at design speed. Design point studies have been found to be an indicative of stall area. Unsteady method of domain scaling has been used to compute the results at near stall and just stall conditions. It has been found that unlike the conventional tip leakage flow of the rotor, stator hub section is mainly responsible for the stall of the fan. The flow mechanism has been discussed with correlation to the design variables and previous investigations. Commercial CFD code NUMECA FINE/Turbo has been used for computations; results have been compared with results obtained from commercial CFD code ANSYS-CFX. The loss prediction of latter code is conservative than the former. The stall mechanism predicted by both codes is analogous.展开更多
Focusing on the aeroelastic stability of thin panel structure of airframe component such as engine nozzle of high-speed flight vehicles,a nonlinear aeroelastic model for a two-dimensional heated panel exposing both su...Focusing on the aeroelastic stability of thin panel structure of airframe component such as engine nozzle of high-speed flight vehicles,a nonlinear aeroelastic model for a two-dimensional heated panel exposing both surfaces to the airflow with different aerodynamic pressures is established.The von Karman large deflection plate theory and the first-order piston theory are used in the formulation of aeroelastic motion.The critical conditions for aeroelastic stability and the stability boundaries are obtained using theoretical analysis and numerical computations,respectively.The results show that the panel is more prone to become unstable when its two surfaces are subject to aerodynamic loading simultaneously;only if the sum of the aerodynamic pressures on both surfaces of the panel satisfies flutter stability condition,can the panel be likely aeroelastically stable;compared with the general panel flutter problem that only one surface is exposed to the airflows,the present condition makes the panel become aeroelastically unstable at relatively small flight aerodynamic pressure.展开更多
基金Foundation item： Project（2013CB036405） supported by the National Basic Research Program of China Project（KZZD-EW-05） supported by the Key Research Program of the Chinese Academy of Sciences
文摘Pile-slab structure roadbed is a new form of ballastless track for high speed railway. Due to lack of corresponding design code, based on the analysis of its structure characteristics and application requirements, it is proposed to carry out load effect combination according to ultimate limit state and serviceability limit state, and the most unfavorable combination of each state is chosen to carry through design calculation for pile-slab structure. Space model of pile-slab structure can be simplified as a plane flame model, by using the orthogonal test method, and the design parameter of pile-slab structure is optimized. Moreover, based on the engineering background of Suining-Chongqing high-speed railway, the dynamic deformation characteristics of pile-slab structure roadbed are further researched by carrying on the indoor dynamic model test. The test results show that the settlement after construction of subgrade satisfies the requirement of settlement control to build ballastless track on soil subgrade for high-speed railway. Slab structure plays the role of arch shell as load is transmitted from slab to pile, and the vertical dynamic stress of subgrade soil is approximately of ＂K＂ form distribution with the depth. The distribution of pile stress is closely related to soil characteristics, which has an upset triangle shape where the large dynamic stress is at the top. Pile compared with soil shares most dynamic stress. Pile structure expands the depth of the dynamic response of subgrade has limited effect on dynamic response. These results can provide subgrade. and improves the stress of subgrade soil, and the speed of train scientific basis for pile-slab structure roadbed used on soil
基金Project supported by the National Natural Science Foundation of China(No.51605397)the National Key R&D Program of China(No.2016YFB1200602-15)the Sichuan Provincial Science and Technology Support Program(No.2019YJ0227),China。
文摘With the increasing demand of higher travelling speed,a new streamlined high-speed maglev train has been designed to reach a speed of 600 km/h.To better capture the flow field structures around the maglev train,an improved delayed detached eddy simulation(IDDES)is adopted to model the turbulence.Results show that the new maglev train has good aerodynamic load performance such as small drag coefficient contributing to energy conservation.The main frequencies of aerodynamic forces for each car have a scattered distribution.There are two pairs of counter-rotating large vortices in the non-streamlined part of the train that make the boundary layer thicker.Many high-intensity vortices are distributed in the narrow space between skirt plates or train floor and track.In the gap between the train floor and track(except near the tail car nose),the main frequency of vortex shedding remains constant and its strength increases exponentially in the streamwise direction.In the wake,the counter-rotating vortices gradually expand and reproduce some small vortices that move downward.The vortex has quite random and complex frequencydomain distribution characteristics in the wake.The maximum time-averaged velocity of the slipstream occurs near the nose of the head car,based on which,the track-side safety domain is divided.
文摘In this paper a numerical investigation has been presented on the stall mechanism of a highly loaded Single Stage Low Speed Fan designed for the research test facility to be installed at North Western Polytechnic University (NWPU) Xi’an, China. The results presented are for the design point, near stall and just stall operating conditions at design speed. Design point studies have been found to be an indicative of stall area. Unsteady method of domain scaling has been used to compute the results at near stall and just stall conditions. It has been found that unlike the conventional tip leakage flow of the rotor, stator hub section is mainly responsible for the stall of the fan. The flow mechanism has been discussed with correlation to the design variables and previous investigations. Commercial CFD code NUMECA FINE/Turbo has been used for computations; results have been compared with results obtained from commercial CFD code ANSYS-CFX. The loss prediction of latter code is conservative than the former. The stall mechanism predicted by both codes is analogous.
基金supported by the National Natural Science Foundation of China (Grant Nos.11072198,11102162)111 Project of China (GrantNo. B07050)
文摘Focusing on the aeroelastic stability of thin panel structure of airframe component such as engine nozzle of high-speed flight vehicles,a nonlinear aeroelastic model for a two-dimensional heated panel exposing both surfaces to the airflow with different aerodynamic pressures is established.The von Karman large deflection plate theory and the first-order piston theory are used in the formulation of aeroelastic motion.The critical conditions for aeroelastic stability and the stability boundaries are obtained using theoretical analysis and numerical computations,respectively.The results show that the panel is more prone to become unstable when its two surfaces are subject to aerodynamic loading simultaneously;only if the sum of the aerodynamic pressures on both surfaces of the panel satisfies flutter stability condition,can the panel be likely aeroelastically stable;compared with the general panel flutter problem that only one surface is exposed to the airflows,the present condition makes the panel become aeroelastically unstable at relatively small flight aerodynamic pressure.
