43results about How to "Improve flow quality" patented technology

The invention discloses a shock tunnel detonation double-driving method, which comprises the following steps of: 1) arranging a positive detonation igniter at one end close to an explosion-releasing section, of a shock tunnel detonation driving section and arranging a reverse detonation driving igniter at the end close to a driven section, of the detonation driving section; 2) igniting by the positive detonation igniter, thereby forming a positive driving detonation wave; 3) after transmitting the positive driving detonation wave along the detonation driving section for a preset period of time, igniting by the reverse detonation driving igniter, thereby forming a reverse driving detonation wave; and 4) tearing a diaphragm arranged between the driven section and the detonation driving section by the reverse driving detonation wave and forming a motion shock wave after intersecting the positive driving detonation wave with the reverse driving detonation wave. According to the method, the diaphragm arranged between the driven section and the detonation driving section is torn by the reverse driving detonation wave, the diaphragm is more regularly torn and a diaphragm fragment is difficult to form, thereby being small in interference effect on the flowing of the formed airflow and promoting the flowing quality of the driven air.

Disclosed is a bio-fertilizer composition for promoting growth of orchid plants. The composition comprises a symbiotic organism, a growth substance; and a medium, which is used to mix and evenly disperse the symbiotic organisms and the growth substance. The symbiotic organism is selected from the group consisting of Rhizoctonia sp. (BCRC930076) and Rhizoctonia sp. (BCRC930077). The bio-fertilizer composition according to the invention can promote the growth of orchid plants, increase the flowering rate and flowering quality, decrease the occurrence of root disease to prevent the usage of pesticide, and increase the beneficial components toward human health of medicinal orchids.

A method for designing gas turbine engine components using a coupled parametric analysis of part geometry and flow control is disclosed. Included are the steps of parametrically defining the geometry of the duct wall shape, parametrically defining one or more flow control actuators in the duct wall, measuring a plurality of performance parameters or metrics (e.g., flow characteristics) of the duct and comparing the results of the measurement with desired or target parameters, and selecting the optimal duct geometry and flow control for at least a portion of the duct, the selection process including evaluating the plurality of performance metrics in a pareto analysis. The use of this method in the design of inter-turbine transition ducts, serpentine ducts, inlets, diffusers, and similar components provides a design which reduces pressure losses and flow profile distortions.

The invention relates to the technical field of aerospace, and discloses an active control method and device for aerofoil drag reduction. A plurality of piezoelectric devices are uniformly arranged at the trailing edge of an aerofoil in advance, and when an aircraft takes off or flies at a low speed, the piezoelectric devices are controlled to dent so as to enable concave pits to be formed in the corresponding position of the aerofoil, so that the separation of the boundary layer is postponed and the pressure drag is reduced; when the aircraft flies at a high speed, the piezoelectric devices are controlled to be bulged so as to enable bumps to be formed in the corresponding position, so that the drag is reduced; or the piezoelectric devices are controlled to be in the periodic oscillation operating mode, so that the wake zone of the aerofoil is enabled to form a periodic vortex structure so as to control flow separation. The active control method and device for aerofoil drag reduction have the advantages that the aircraft is enabled to actively switch the corresponding drag reduction mode in different flight regimes, and the flight efficiency is improved.

The invention discloses a pantograph damper damping throttling device. One end of an oil cylinder is sealed through a guide bearing. A center hole is formed in the guide bearing which provides supporting and guiding for a piston rod. The other end of the oil cylinder is sealed through a bottom valve seat. A piston, a spring base, springs, a compression valve plate, an stretchable spring valve plate and a stop plate are installed on the piston rod. The oil cylinder is divided into a first cavity and a second cavity through the piston. Stretchable throttling holes and compression throttling holes are formed in the piston, wherein the stretchable throttling holes and the compression throttling holes are oppositely arranged. The compression valve plate located at the position, close to the end face of one side of the first cavity of the oil cylinder, of the piston covers the compression throttling holes and is pressed through the springs, and the springs are fixed on the spring base. The stretchable spring valve plate located at the position, close to the end face of one side of the second cavity of the oil cylinder, of the piston covers the stretchable throttling holes and is pressed through the stop plate, and the stop plate is fixed on the piston rod through a locking nut. The pantograph damper damping throttling device can overcome the technical defect that in the prior art, when the piston rod is stretched to the final stroke, damping force can not be adjusted and controlled at will.

The invention discloses a high-strength insulation material pantograph which comprises a sliding plate mechanism, a lifting frame, a supporting frame, an under frame, a driving system and an insulated cable, wherein the sliding plate mechanism is a current collection mechanism of an elastic floating-support sliding plate, and can reduce the influence of the engine vibration and the electric network height oscillation on the current collection quality; the lifting frame and / or supporting frame are / is made of a high-strength insulation material, thereby having several times of the electrical insulation property required by the catenary system and needing no support insulators, and the collected current of the sliding plate is transmitted by a special insulated cable; the driving system drives a drive bolt by an automatic gear shifting motor, thereby lifting the pantograph at variable speeds; the insulated cable of the invention is a braided wire cladded by special insulation rubber; and the under frame of the invention is directly fixed on the vehicle top. The invention has the advantages of good current collection quality and safe and reliable insulation, and can be widely used in high speed and high power electric locomotives and motor train units.

The invention relates to a rolling contact pantograph head which belongs to the technical field of stable current collection of a pantograph and catenary system. By the aid of the rolling contact pantograph head, frictional wear among pantograph and catenary is reduced effectively, the performance, of a pantograph, resisting impact from hard points of wires of a catenary is improved, off-line rate of the pantograph and catenary is lowered substantially, and current collection quality is improved. The rolling contact pantograph head comprises a roller, a left end cover, a right end cover, conductive blades, conductive liquid, a metal conductive shaft, a left conductive corner and a right conductive corner, wherein through holes are formed in the left end cover and the right end cover, the metal conductive shaft is arranged in the roller, the left end cover and the right end cover are arranged at the left and the right ends of the roller respectively, two ends of the metal conductive shaft penetrate the through holes of the left end cover and the right end cover respectively and are arranged out of spaces formed between the left and right end covers and the roller, a closed inner cavity is formed by the metal conductive shaft, the left end cover, the right end cover and the roller, the conductive liquid is arranged in the inner cavity, the conductive blades are arranged on the metal conductive shaft in the inner cavity, and the left conductive corner and the right conductive corner are arranged at two ends of the roller and are in seamless joint with the roller.

Disclosed is a double-row multi-roller type modular current-receiving device for an electric locomotive. According to the double-row multi-roller type modular current-receiving device for the electriclocomotive, two rows of metal rollers are annularly arranged on an insulating base; each rolling wheel is arranged in the manner that two insulating stand columns are fixed to the insulating base, compression springs sleeve the two insulating stand columns correspondingly, insulating blocks sleeve the insulating stand columns and are located above the compression springs, metal shells of the rollers are installed on metal shafts through two insulating bearings, the metal shafts are fixed to the two insulating blocks, the outer surface of an annular current receiving electric brush makes contact with the roller metal shells to receive current, the inner surface of the annular current receiving electric brush is fixed to the metal shafts, all the metal shafts are connected through cables and are then used for supplying power to vehicle-mounted power consuming equipment, and two pure carbon sliding plates are fixed to the insulating base through more than four springs. The friction forceand the friction noise of the current-receiving device and a rigid contact rail can be effectively reduced, and the double-row multi-roller type modular current-receiving device can adapt to the changes of locomotive traction power requirements and has good buffering performance, heat dissipation performance and rail attaching performance.

The invention discloses an air bag type pantograph closed-loop control device, comprising an air cleaner, an electrically controlled pressure regulating valve, a silencer, a reversing solenoid valve,a bow rising throttle valve, a falling bow throttle valve, a safety valve, a bow rising airbag, a pressure sensor, a bow head airbag and a control unit, wherein, the bow head airbag is connected between a carbon slide plate and a bow head bracket, the bow head airbag and the bow rising airbag are respectively connected with a reversing electromagnetic valve, and the pressure sensor is connected with an air path between the bow head airbag and the reversing electromagnetic valve. The pressure sensor, the electronically controlled pressure regulating valve and the reversing solenoid valve are respectively in signal connection with the control unit. The pressure data in the bow airbag installed between the carbon skate plate and the bow bracket is fed back to the control unit to realize the closed-loop control of pantograph-catenary contact force. The device can detect pantograph-catenary contact force in real time, and can adjust the pantograph-catenary dynamic contact force when pantograph is running at high speed according to the needs, so as to improve the quality of current collection and ensure the safe and reliable operation of the train.

The invention discloses a shock tunnel which comprises a driving section and a driven section, wherein the diameter of a channel in the driven section is larger than that of a channel in the driving section; a transition section is arranged between the driving section and the driven section; the diameter of a channel in the transition section is gradually enlarged from the driving section to the driven section; the diameter of a channel which is arranged in the transition section and is connected with one end of the driving section is the same as that of the channel in the driving section; and the diameter of a channel which is arranged in the transition section and is connected with one end of the driven section is the same as that of the channel in the driven section. The transition section is adopted to connect the driving section with smaller internal diameter and the driven section with larger internal diameter, and a streamlined gradient curved surface is adopted as the shape of the channel in the transition section, so that boundary layer separation, large separation and the formation of instable vortex can be avoided; therefore, the uniform stability of flow can be improved, the flow loss is less, and the flow quality is improved.

The invention discloses a high-speed pantograph multidisciplinary design method based on a collaborative optimization algorithm, and the method comprises the steps: analyzing design factors influencing the working performance of a high-speed pantograph based on a multidisciplinary design theory, and carrying out the disciplinary classification design of the design factors; carrying out numerical analysis on the design parameters of the subjects, deriving mathematical expressions of the design targets of the subjects, and establishing corresponding optimization design models; based on a globalsensitivity method, analyzing a coupling relation and coupling strength of design variables in the optimization design model of each subject; determining system-level and subject-level design variables according to the coupling strength of the design variables, and solving an optimization value of the design variables in the optimization model of each subject by adopting a multidisciplinary designcollaborative optimization algorithm; and analyzing an optimization result of the pantograph according to the optimization value of the design variable, and establishing a three-dimensional solid model of the pantograph. The working performance of the pantograph is improved, the pantograph net current collecting quality is improved, and a new design research idea is provided for the high-speed pantograph.

A low clearance single track tunnel contact wire positioning device comprises an arched base, a connecting double lug, a rotating double lug, an elastic insulated limiting positioner and a positioningwire clip; the arched base is fixed on the wall of a tunnel through a bolt; the connecting double lug is fixed at the front end of the arched base through a bolt pair; the rotating double lug is hinged to the front end of the connecting double lug through a pin shaft; the rear end of the elastic insulated limiting positioner is a bent section; the end part of the bent section is hinged between lower lugs at the front end of the rotating double lug through a bolt pin I; an elastic pull rod is mounted at the middle part of the bent section; the upper end of the elastic pull rod is hinged between upper lugs at the front end of the rotating double lug through a bolt pin II; and the positioning wire clip is fixed under the front end of the elastic insulated limiting positioner. According to the low clearance single track tunnel contact wire positioning device, shortcomings in the prior art are eliminated, the elastic uniformity of an overhead line system is improved, the current collectingquality of a pantograph type current collector is improved, and therefore, the safety running of a locomotive is guaranteed.

The invention provides a balloon catheter. The balloon catheter comprises a catheter body and a balloon body sleeving the catheter, the balloon body comprises an inner-layer balloon body and an outer-layer balloon body, and the inner-layer balloon body and the outer-layer balloon body directly and fixedly wrap the catheter body; the inner-layer balloon body is located in the outer-layer balloon body, a medium passage is formed between the inner-layer balloon body and the outer-layer balloon body, and an outer-layer medium inflowing hole and a medium reflowing hole which are communicated with the medium passage are formed in the catheter passage. According to the balloon catheter, by arranging the balloon body of the two layers, mediums can flow in the medium passage between the inner-layerballoon body and the outer-layer balloon body, flow into the medium passage through the outer-layer medium inflowing hole and then flow out of the medium passage through the medium reflowing hole, thereby achieving circulation; more mediums can be subjected to heat exchange on the inner surface in the outer-layer balloon body, the flow speed distribution is uniform, the flow quality of the mediums on the surface of the balloon body is improved, and the heat exchange efficiency is improved.

The invention provides a gyro directional platform for a pantograph of an electric locomotive, which belongs to the technical field of electrified railways. The technical problem of stability in operation of electric locomotive pantographs troubles the railway operation department for long. Limiters, oil pressure dampers and air springs are sequentially arranged in the direction of four corner intersection lines of a platform base plate from outside to the center, the air springs and the oil pressure damper are arranged between a top plate of the electric locomotive and the platform base plate, the limiters are mounted on the top plate of the electric locomotive, a gyro directional device consists of two X-axially mounted gyros with the Y-axis serving as the axis of symmetry and two Y-axially mounted gyros with the X-axis serving as the axis of symmetry, and the pantograph is mounted on the platform base plate through four insulators. Rigidity of the air springs can be changed by adjusting inflating pressure to enable optimal damping effect of the pantograph in the Z direction, a damping platform provides degrees of freedom for the gyro directional device in movement, and the pantograph is kept avoiding rotating around the X-axis and the Y-axis, so that off line is reduced, and current collection quality can be improved. The gyro directional platform is mainly used for mounting pantographs.

The invention discloses a single arm pantograph with a ternary system structure and relates to the technical field of wire net current receiving pantographs adopted on electric traction locomotives. The single arm pantograph comprises an underframe, a pantograph rising spring, a lower arm rod assembly, an upper arm rod assembly and a pantograph assembly, wherein the pantograph assembly comprises apantograph head support, a micro-motion spring, a connecting frame, a restoring spring, a sliding plate support and a sliding plate, the pantograph head support is used for connection with the upperend of the upper arm rod assembly, the sliding plate is fixed to the sliding plate support, the micro-motion spring is arranged between the pantograph head support and the connecting frame, the restoring spring is arranged between the connecting frame and the sliding plate support, and the micro-motion spring and the restoring spring are identical in displacement. The single arm pantograph adoptsthe ternary system structure provided with the pantograph rising spring, the restoring spring and the micro-motion spring, reduction mass of a pantograph head can be better dispersed, a pantograph off-line phenomenon is improved, a pantograph net following performance is improved, better current-receiving quality is obtained, the pantograph failure rate is reduced, and productivity effect of operation is improved.

The invention discloses a seamless contact rail expansion connecting device, which comprises an isosceles trapezoidal rail and two end rails respectively located at two longitudinal ends of the trapezoidal rail. An elastic fastener is arranged between the trapezoidal rail and the two end rails so that the trapezoidal rail closely contacts the two end rails in the longitudinal direction. The end rail and the back surface of the trapezoidal rail are also provided with an automatic centering part to keep the trapezoidal rail in the longitudinal center position of the two end rails in the processof sliding relative to each other. The invention provides a seamless contact rail expansion connection device, As an automatic centering part is arranged between the end rail and the trapezoidal rail,and the end rail and the trapezoidal rail are produced by cutting the same section of the main rail, the device ensures that the trapezoidal rail is kept in the middle position of the two end rails at all times when the contact rail is thermally expanded and cold contracted, and the trapezoidal rail does not produce the transverse height difference due to the machining error when the trapezoidalrail moves relative to each other, which is favorable for the current collector to smoothly pass through the expansion joint, and ensures the continuous and stable current collection between the current collector and the contact rail.

The active control type air valve plate comprises a bottom plate, a control unit and an air path unit are installed on the bottom plate, and the air path unit comprises an air inlet, a filter valve, apantograph rising electromagnetic valve, a pressure regulating valve, a high-frequency valve I, a high-frequency valve II, a safety valve, a pressure sensor I, a pressure sensor II, an air outlet, afeedback port and a pressure switch. The filter valve, the pantograph lifting electromagnetic valve and the pressure regulating valve are respectively fixed on the bottom plate; the high-frequency valve I, the high-frequency valve II, the safety valve, the pressure sensor I and the pressure sensor II are fixed on the bottom plate through the gas circuit block I; the pressure switch is fixed on thebottom plate through a gas circuit block II; the air outlet is formed in the air path block I, and the feedback port is formed in the air path block II. According to the invention, the average dynamic pressure of the pantograph and the contact network can be adjusted in real time, and the pantograph control unit can monitor the gas circuit in real time.

The invention provides a high-pressure gas flow rapid pressure reduction fairing device and method. The high-pressure gas flow rapid pressure reduction fairing device is of a revolving body structure,and sequentially comprises an inlet flange (1), a supersonic speed shock wave section (2), a straight section (5), a convergence section (10) and an outlet flange (11) along the gas flow direction. After a gas flow enters the device, the total pressure is rapidly reduced through two times of shock waves, and after multiple times of fairing treatment, the gas flow speed and uniformity are accurately controlled. The flow quality of fuel gas can be comprehensively improved, and proper gas flow inlet parameter conditions are provided for non-toxic treatment of downstream fuel gas.

The invention discloses a small-corner pantograph head design method. According to the method, corners of pantograph heads are optimized by utilizing mature dynamic software and an integrated generaloptimization algorithm library by using a method for relative position parameter coordinates of pantograph hinge points, so that deflection angles of the pantograph heads are remarkably decreased, thepantograph heads can achieve a nearly translational motion state in working ranges of pantographs, and contact areas between the pantographs and contact nets are increased, thereby effectively improving the current-receiving quality of the pantographs and decreasing the pantograph net damage.

The invention relates to a rolling contact pantograph head which belongs to the technical field of stable current collection of a pantograph and catenary system. By the aid of the rolling contact pantograph head, frictional wear among pantograph and catenary is reduced effectively, the performance, of a pantograph, resisting impact from hard points of wires of a catenary is improved, off-line rate of the pantograph and catenary is lowered substantially, and current collection quality is improved. The rolling contact pantograph head comprises a roller, a left end cover, a right end cover, conductive blades, conductive liquid, a metal conductive shaft, a left conductive corner and a right conductive corner, wherein through holes are formed in the left end cover and the right end cover, the metal conductive shaft is arranged in the roller, the left end cover and the right end cover are arranged at the left and the right ends of the roller respectively, two ends of the metal conductive shaft penetrate the through holes of the left end cover and the right end cover respectively and are arranged out of spaces formed between the left and right end covers and the roller, a closed inner cavity is formed by the metal conductive shaft, the left end cover, the right end cover and the roller, the conductive liquid is arranged in the inner cavity, the conductive blades are arranged on the metal conductive shaft in the inner cavity, and the left conductive corner and the right conductive corner are arranged at two ends of the roller and are in seamless joint with the roller.

The invention discloses a pantograph-catenary contact wear debris distribution control device and method. The device comprises a magnetic field control module, an environmental data collection module and a PC server; the magnetic field control module and the environmental data collection module are both connected to the PC server; the PC The server controls the current intensity of the magnetic field control module according to the data of the environmental data acquisition module, so that a specific magnetic induction intensity is generated in the contact area of ​​the pantograph-catenary friction pair, so that the distribution of wear debris in the contact area is in an optimal state; the present invention reduces the friction coefficient, improves the The surface roughness realizes the mechanical and electrical balance of the pantograph-catenary system, improves the severe mechanical wear of the pantograph slide plate and the catenary wire, and also improves the energy transmission efficiency and electrical contact characteristics of the pantograph-catenary system, and the structure is simple and the effect is Significant, with strong practical value and promotion value.

The invention provides a pantograph slide plate with a conductive fiber bundle structure, the pantograph slide plate comprises a slide plate base body and a conductive fiber bundle arranged on the slide plate base body, the conductive fiber bundle comprises a metal cylinder and a carbon fiber bundle fixed in the metal cylinder, the outer wall of the metal cylinder is provided with an external thread, and the plate surface of the slide plate base body is provided with a plurality of screw holes. The screw holes are through holes, internal threads of the screw holes are matched with external threads of the metal cylinder, a plurality of cleaning holes are further formed in the plate surface of the sliding plate base body, the cleaning holes are communicated with cleaning hole channels formed in the plate, and the cleaning hole channels are connected with an air supply port in the plate surface of the sliding plate base body. By adjusting the height of the conductive fiber, the contact surface of the conductive fiber at the seriously worn position is recovered to be in a flat state, and meanwhile, abrasive dust and dust in gaps of fiber bundles can be conveniently cleaned.

The invention discloses a conductor wire non-stress identification method and system based on target detection and a residual network, and belongs to the technical field of contact network conductor wire identification. An existing conductor wire stress recognition scheme is poor in recognition precision and large in error. According to the conductor wire non-stress identification method based on the target detection and the residual network, the stress condition of the conductor wire is accurately identified by using the target detection algorithm and the residual network, and compared with the existing priori knowledge and inclined stay wire angle difference scheme, the identification precision is higher, the error is smaller, and the data processing is more objective, accurate and efficient. Furthermore, the method can efficiently identify the state of the conductor wire, has good stability, can effectively avoid the damage of a contact network system, improves the current collection quality of a pantograph, is simple, practical and feasible in scheme, and has very high economic value.

The invention provides a novel hydraulic type inerter damping device, a piston is in clearance fit with a hydraulic cylinder, through holes are formed in the piston, and when the damping device works, part of working liquid flows into the working space on the other side of the piston through the clearance between the piston and the hydraulic cylinder and the through hole in the piston; non-linear damping force with a low speed index is generated by flowing of the working liquid, overlarge damping output can be limited, and the device is effectively protected. A ball and a plugging ball are arranged in a spiral return pipe communicated with the hydraulic cylinder, the other part of liquid rotates along the spiral return pipe, the ball and the plugging ball roll in a reciprocating mode under the action of pressure difference, and the mass amplification effect can be achieved through the conversion mode from linear motion of the piston to rotating motion of working liquid. The inertia force is improved, meanwhile, the coupling effect of the damping force and the inertia force in the spiral return pipe is weakened, the damping performance is improved, and dimethyl silicone oil is adopted as working liquid so that the damping output level can be increased.

The invention provides a pantograph-catenary relation detection method which comprises a catenary geometric parameter detection method, a pantograph-catenary contact force and hard point detection method and a pantograph-catenary arcing detection method, and hardware equipment applied to the pantograph-catenary relation detection method mainly comprises an information interaction system, vehicle-mounted detection equipment, pantograph-catenary detection equipment and communication processing equipment. The vehicle-mounted detection equipment is provided with a vehicle-mounted wireless network system, and the remote monitoring management center is provided with a vehicle-mounted wireless network system. According to the invention, each subsystem can work independently and can summarize, integrate and process information, and through an intelligent detection mode, various fault problems can be automatically identified, defect positions can be positioned, fault reports can be generated, normal operation and maintenance of equipment can be guided, and hard point calculation precision can be improved; data interaction with a remote monitoring center is realized through a 5G network, remote monitoring and data management are realized, detection data are fed back to related departments, and timely problem processing and remote monitoring operation are facilitated.

The invention provides a microchannel heat exchanger, a machining method and an air conditioner. The microchannel heat exchanger comprises a first flow collecting pipe and a second flow collecting pipe; multiple heat exchange flat pipes communicate between the first flow collecting pipe and the second flow collecting pipe; guide plates for guiding refrigerants to flow into each heat exchange flatpipe are arranged in the first flow collecting pipe and / or the second flow collecting pipe; the guide plates take the shape of arc surfaces, and the flow directions of the refrigerants are towards concave surfaces of the guide plates; and the radius of each guide plate in the same section in which the refrigerants in the first flow collecting pipe or the second flow collecting pipe are directly circulated is increased sequentially in the flow direction of the refrigerant. The microchannel heat exchanger, provided by the invention, are provided with the guide plates in the first flow collectingpipe and the second flow collecting pipe, and designs the radiuses of the guide plates to be increased sequentially in the flow directions of the refrigerants, so that the refrigerants are distributed more uniformly when flowing into the same batch of heat exchange flat pipes. The flow directions of the refrigerants are gradually changed by means of the arc surface-shaped guide plates instead ofbeing suddenly changed, so that the pressure drop is reduced, and the flow quality of the refrigerants is greatly improved.

The invention discloses a plane cascade wind tunnel outlet section back pressure adjusting device. A pressure box, an upper diffusion plate and a lower diffusion plate are all arranged at the downstream of the plane cascade and form the wind tunnel outlet section of the plane cascade, and an upper supporting part is fixedly arranged on the upper surface of the pressure box or the upper diffusion plate; the upper end of the upper supporting part is connected to the upper wall of the wind tunnel in an up-down adjustable mode, the lower supporting part is fixedly arranged on the lower surface of the lower diffusion plate, the lower end of the lower supporting part is connected to the lower wall of the wind tunnel in an up-down adjustable mode, and the lower surface of the upper diffusion plate is movably connected with an angle-adjustable throttling plate. Through adjusting the opening angle of the throttling plate, the outlet flow area of the plane cascade can be changed, and the back pressure of the wind tunnel outlet section of the plane cascade is further adjusted; the lower wall of the pressure box is of a porous structure, the interior of the pressure box is of a cavity structure, and the pressure box is used for sucking low-speed fluid on the lower wall face, restraining boundary layer development, improving the through-flow capacity, improving the periodicity of a cascade outlet and improving the flow quality of a wind tunnel.