A double-stage ejector for preventing vortex generation

Abstract

The present invention provides a two-stage ejector for preventing vortex generation, comprising a cavity, a valve seat, and a nozzle. One end of the cavity forms an outlet, a nozzle is mounted within a mixing chamber, and a valve seat is mounted at the nozzle inlet. The nozzle is provided with two independent jet channels. The valve seat communicates with a second air inlet. The valve core of the valve seat operates to connect the second air inlet with the first jet channel or with both jet channels. The nozzle comprises a primary nozzle and a secondary nozzle. The primary nozzle is located within the mixing chamber, and the secondary nozzle is mounted at one end of the primary nozzle, with one end of the secondary nozzle inserted into the internal cavity of the primary nozzle. The space between the secondary nozzle housing and the internal cavity of the primary nozzle forms the first jet channel, and the central hole within the secondary nozzle forms the second jet channel. One end of the secondary nozzle extends beyond the end face of the primary nozzle. The present invention can prevent vortex generation at the nozzle outlet.

Description

Technical Field

[0001] The present invention relates to the field of ejectors or fuel cells, and in particular to a double-stage ejector capable of preventing vortex generation. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are highly efficient electrochemical energy conversion devices that use hydrogen as fuel and produce water through a reaction. Their power generation efficiency is not limited by the Carnot cycle, making them ideal for meeting future society's demand for efficient, clean, and economical energy systems. To achieve high-efficiency operation of fuel cell systems, a hydrogen supply system is used to oversupply the fuel cell stack. Therefore, any unreacted hydrogen that passes through the stack needs to be recovered and reused to improve efficiency.

[0003] At present, in order to address the shortcomings of the ejector's narrow working range and weak adaptability to the variable load of the fuel cell stack, some inventions have been made to improve the front end of the traditional single-stage ejector, including designing multiple nozzles or dual channels to achieve dynamic hydrogen supply. Although the shortcomings of the poor adaptability of the ejector have been alleviated, the simultaneous operation of multiple inlets will cause the intake air to mix with each other, resulting in energy loss, while reducing high-speed flow energy and the ability to entrain the ejection flow. At the same time, the front-end speed is high, and the total speed drops sharply when directly converging, which will produce unstable flow phenomena such as vortexes and oscillations, resulting in uneven mixing of the airflow in the suction chamber and slow flow of the mixed gas boundary layer. A strong shock wave will be formed in the isochoric mixing tube and move to the diffuser, affecting the diffusion effect and the ejector outlet pressure, thereby reducing the supply pressure entering the fuel cell stack, and ultimately failing to effectively improve the working efficiency of the fuel cell stack system under this mode. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention provides a two-stage ejector that prevents the generation of vortices. By extending one end of the secondary nozzle beyond the end face of the primary nozzle, the effect of axial steps at the outlets of the two ejection channels is achieved, thereby preventing the front end of the multi-channel ejector from causing unstable phenomena such as vortices and oscillations due to the simultaneous mixing of multiple airflows. By changing the outer contour surface of the secondary nozzle, the jet gas is guided to move forward along the wall, maintaining a relatively high speed and uniform mixing with the outlet gas of the first ejection channel. At the same time, the radial velocity of the jet gas is reduced by the diffuser section at the outlet of the secondary nozzle, which eases the mixing process of the outlet gas of the second ejection channel with the outlet gas of the first ejection channel and the jet gas, reducing energy loss, and utilizing gas shear stress to make the gas mix evenly, so that the gas enters the mixing chamber with a high-speed and stable airflow, and is stably supplied to the fuel cell stack.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A two-stage ejector for preventing vortex generation comprises a cavity, a valve seat, and a nozzle. One end of the cavity is an outlet, and the other end of the cavity is provided with a first air inlet. A mixing chamber connected to the first air inlet is provided in the cavity. A nozzle is installed in the mixing chamber, and a valve seat is installed at the inlet of the nozzle. Two independent jet channels are provided in the nozzle. The valve seat is connected to the second air inlet. The second air inlet is connected to the first jet channel or to both jet channels through the action of the valve core of the valve seat.

[0007] The nozzle includes a primary nozzle and a secondary nozzle, the primary nozzle is located in the mixing chamber, and the primary nozzle is installed on the other end of the cavity; the secondary nozzle is installed at one end of the primary nozzle, and one end of the secondary nozzle is inserted into the internal cavity of the primary nozzle, the space between the secondary nozzle shell and the internal cavity of the primary nozzle is the first jet channel, and the center hole in the secondary nozzle is the second jet channel; one end of the secondary nozzle extends out of the end face of the primary nozzle to prevent vortexes from being generated at the nozzle outlet.

[0008] Furthermore, the internal cavity of the first-stage nozzle is provided with a transition section, a tapered section and an injection section in sequence according to the flow direction; the shell of the second-stage nozzle is provided with a first-section shell, a second-section shell and a guide end in sequence according to the flow direction; the guide end is inserted into the injection section so that the cross-section of the outlet of the first jet channel is annular; one end of the guide end extends out of the end face of the injection section.

[0009] Furthermore, the valve seat includes a shell, an electromagnetic winding, an elastic element and a valve core; a second air inlet is provided on the shell for connecting to the hydrogen supply system; a movable valve core is installed in the cavity of the shell, and an electromagnetic winding is installed in the cavity of the shell, and the valve core is moved in the cavity of the shell by energizing the electromagnetic winding; a plurality of connecting holes connected to the first jet channel are provided on the other end of the secondary nozzle; a plurality of through holes are distributed around the valve core, and the phase angles of the through holes and the connecting holes correspond one to one; the elastic element is installed between the valve core and the inner wall of the shell cavity, and when the electromagnetic winding is de-energized, the valve core is fitted with the end face of the other end of the secondary nozzle through the elastic element, so as to block the connection between the second jet channel and the through hole; when the electromagnetic winding is energized, the valve core is moved toward the second air inlet, so as to connect the first jet channel and the second jet channel with the second air inlet respectively.

[0010] Furthermore, the outer contour of the first section shell is cylindrical, the outer contour of the second section shell is conical, and the injection section is a tapered hole, which is used to form a gradually expanding annular outlet at the outlet of the first jet channel.

[0011] Furthermore, the outer contour surface of the guide end is provided with a first guide surface and a third guide surface in sequence according to the flow direction. One side of the first guide surface smoothly transitions with the second section shell, and applies a supporting force to the gas at the outlet of the first injection channel to keep the gas at the outlet of the first injection channel moving horizontally; the inner hole of the guide end located at the outlet of the second jet channel is provided with a second guide surface, which radially diverts and constrains the gas at the outlet of the second injection channel to keep the gas at the outlet of the second injection channel moving horizontally before the two injection channels are mixed; the third guide surface is a tapered cone surface, and the mixed gas composed of the gas at the outlet of the second injection channel and the gas entering the mixing chamber is obliquely cut into the gas at the outlet of the first injection channel along the third guide surface, so as to alleviate the mixing of the two airflows.

[0012] Furthermore, the inclination angle of the third guide surface increases with the increase of the axial length of the guide end.

[0013] Furthermore, the angle between the third guide surface and the axial direction is 8 to 15 degrees.

[0014] Furthermore, the injection section is a tapered hole, and the taper of the third guide surface is the same as that of the tapered hole of the injection section, but in the opposite direction.

[0015] Furthermore, a diffuser section is provided at the outlet of the second guide surface, the taper of the inner contour of the diffuser end is a positive taper θ, and the taper of the third guide surface of the guide nozzle is greater than the taper of the inner contour of the diffuser section.

[0016] Furthermore, the distance from one end of the secondary nozzle extending from the end face of the primary nozzle to the cross section at the outlet of the mixing chamber is NXP, and NXP is 0.8 to 1.1Dm, where Dm is the nominal diameter of the outlet of the mixing chamber.

[0017] The beneficial effects of the present invention are:

[0018] 1. The dual-stage ejector disclosed herein prevents vortex generation. By extending one end of the secondary nozzle beyond the end face of the primary nozzle, it creates an axial step at the exit of each ejection channel. This prevents instabilities such as vortexes and oscillations caused by the simultaneous mixing of multiple airflows at the front end of the multi-channel ejector. The distance from the end of the secondary nozzle extending beyond the end face of the primary nozzle to the cross-section of the mixing chamber outlet is NXP. When NXP is 0.8 to 1.1 Dm, optimal entrainment and airflow mixing are achieved.

[0019] 2. The double-stage ejector for preventing vortex generation described in the present invention has the guide end inserted into the injection section so that the cross-section of the first jet channel outlet is annular, and the outer contour surface of the guide end is provided with a first guide surface and a third guide surface in sequence according to the flow direction. The first guide surface applies a supporting force to the gas at the outlet of the first ejection channel, so that the gas at the outlet of the first ejection channel maintains horizontal movement; the third guide surface is a tapered cone surface, and the mixed gas composed of the gas at the outlet of the second ejection channel and the gas entering the mixing chamber is inclined along the third guide surface to cut into the gas at the outlet of the first ejection channel, thereby alleviating the mixing of the two airflows.

[0020] 3. The double-stage ejector for preventing vortex generation described in the present invention has a second guide surface provided on the inner hole of the guide end located at the outlet of the second jet channel. By radially diverting and restricting the gas at the outlet of the second ejection channel, the gas at the outlet of the second ejection channel keeps moving horizontally before the two ejection channels are mixed.

[0021] 4. The double-stage ejector for preventing vortex generation described in the present invention has a conical hole in the injection section, and the taper of the third guide surface is the same as that of the conical hole in the injection section, but in the opposite direction, which can ease the mixing process of the two-stage nozzle gas and maintain a higher flow rate when the flow rate of the first air inlet is low.

[0022] 5. The double-stage ejector for preventing vortex generation described in the present invention reduces the radial velocity of the jet gas through the diffusion section at the outlet of the secondary nozzle, alleviates the mixing process of the gas at the outlet of the second ejection channel, the gas at the outlet of the first ejection channel and the jet gas, reduces energy loss, and utilizes gas shear stress to mix the gas evenly, so that the gas enters the mixing chamber with a high-speed and stable airflow and is stably supplied to the fuel cell stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a structural diagram of the double-stage ejector for preventing vortex generation described in the present invention.

[0025] Figure 2 This is a structural diagram of the double-stage ejector of Example 1.

[0026] Figure 3 for Figure 2 A partial enlarged view of the .

[0027] Figure 4 This is a structural diagram of the secondary nozzle of Example 1.

[0028] Figure 5 This is a structural diagram of the double-stage ejector of Example 2.

[0029] Figure 6 for Figure 5 A partial enlarged view of the .

[0030] Figure 7 This is a structural diagram of the secondary nozzle of Example 2.

[0031] Figure 8 This is the structural diagram of the double-stage ejector of Example 3.

[0032] Figure 9 for Figure 8 A partial enlarged view of the .

[0033] Figure 10 This is a structural diagram of the secondary nozzle of Example 3.

[0034] Figure 11 It is the specific position diagram of NXP distance in the present invention.

[0035] Figure 12 This is a simulation diagram of the existing double-stage ejector working in a single stage.

[0036] Figure 13 This is a simulation diagram of the existing double-stage ejector working in two stages.

[0037] Figure 14 This is a simulation diagram of the double-stage ejector of Example 1 of the present invention when working in a single stage.

[0038] Figure 15 This is a simulation diagram of the double-stage ejector of Example 1 of the present invention when working in two stages.

[0039] In the picture:

[0040] 1-Cavity; 1-1-Mixing chamber; 2-First air inlet; 3-Valve seat; 3-1-Shell; 3-2-Electromagnetic winding; 3-3-Spring; 3-4-Valve core; 3-5-Vent; 3-6-Second air inlet; 3-7-Volume-variable cavity; 4-Nozzle; 4-1-First-stage nozzle; 4-1-1-Transition section; 4-1-2-Tapered section; 4-1-3-Injection section; 4-2-Second-stage nozzle; 4-2-1-First-section shell; 4-2-2-Second-section shell; 4-2-3-Guiding end; 4-2-4-Connecting hole; 4-2-3-1-First guide surface; 4-2-3-2-Second guide surface; 4-2-3-3-Third guide surface; 4-2-3-4-Diffuser section. DETAILED DESCRIPTION

[0041] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "axial", "radial", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0043] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0044] like Figure 1 As shown, the double-stage ejector for preventing vortex generation described in the present invention includes a cavity 1, a valve seat 3 and a nozzle 4. One end of the cavity 1 is an outlet, and the other end of the cavity 1 is provided with a first air inlet 2. A mixing chamber 1-1 connected to the first air inlet 2 is provided in the cavity 1. A nozzle 4 is installed in the mixing chamber 1-1, and a valve seat 3 is installed behind the nozzle 4. Two independent jet channels are provided in the nozzle 4. The valve seat 3 is connected to the second air inlet 3-6. The valve core of the valve seat 3 is actuated to connect the second air inlet 3-6 to the first jet channel or to the two jet channels. In the field of fuel cells, the first air inlet 2 is generally connected to the mixture of unreacted hydrogen and water vapor in the fuel cell stack; the second air inlet 3-6 is connected to the hydrogen supply equipment; the valve core actuation is controlled according to the output power of the fuel cell, so that the ejector can have good performance when working under different output powers of the fuel cell.

[0045] The nozzle 4 includes a first-level nozzle 4-1 and a second-level nozzle 4-2. The first-level nozzle 4-1 is located in the mixing chamber 1-1 and is installed on the other end of the cavity 1; the second-level nozzle 4-2 is installed at one end of the first-level nozzle 4-1, and one end of the second-level nozzle 4-2 is inserted into the internal cavity of the first-level nozzle 4-1. The space between the outer shell of the second-level nozzle 4-2 and the internal cavity of the first-level nozzle 4-1 is the first jet channel, and the center hole in the second-level nozzle 4-2 is the second jet channel; one end of the second-level nozzle 4-2 extends out of the end face of the first-level nozzle 4-1 and extends into the mixing chamber 1-1, which is used to prevent vortexes from being generated at the outlet of the nozzle 4, and to prevent unstable phenomena such as vortexes and oscillations from being caused by the simultaneous mixing of multiple airflows at the front end of the multi-channel ejector. Figure 11 As shown, the distance from the end of the secondary nozzle extending beyond the primary nozzle end face to the cross-sectional area at the outlet of mixing chamber 1-1 is NXP. When NXP is between 0.8 and 1.1 Dm, the entrainment and airflow mixing effects are optimal. The cross-sectional area at the outlet of mixing chamber 1-1 can be understood as the interface between the outlet of the mixing chamber's isobaric chamber and the outlet of the mixing chamber's isochoric chamber. Dm is the nominal diameter of the mixing chamber outlet.

[0046] Example 1

[0047] like Figure 2 、 Figure 3 and Figure 4As shown, the nozzle 4 includes a primary nozzle 4-1 and a secondary nozzle 4-2, the primary nozzle 4-1 is located in the mixing chamber, and the primary nozzle 4-1 is installed on the other end of the cavity 1; the secondary nozzle 4-2 is installed at one end of the primary nozzle 4-1, and one end of the secondary nozzle 4-2 is inserted into the internal cavity of the primary nozzle 4-1, the space between the outer shell of the secondary nozzle 4-2 and the internal cavity of the primary nozzle 4-1 is the first jet channel, and the center hole in the secondary nozzle 4-2 is the second jet channel; The internal cavity of the first-stage nozzle 4-1 is sequentially arranged according to the flow direction, including a transition section 4-1-1, a tapered section 4-1-2, and an injection section 4-1-3. The housing of the second-stage nozzle 4-2 is sequentially arranged according to the flow direction, including a first section 4-2-1, a second section 4-2-2, and a guide end 4-2-3. The guide end 4-2-3 is inserted into the injection section 4-1-3, forming a circular cross-section at the exit of the first jet channel. One end of the guide end 4-2-3 extends beyond the end surface of the injection section 4-1-3 and into the mixing chamber 1-1. The single-sided clearance between the guide end 4-2-3 and the injection section 4-1-3 is larger than the clearance fit used in traditional mechanical designs, such as the commonly used clearance fits of H7 / h6, H8 / f7, G7 / h6, and F8 / h7. Preferably, after the guide end 4-2-3 is inserted into the injection section 4-1-3, the single-side gap between the guide end 4-2-3 and the injection section 4-1-3 does not exceed 0.1 mm, which is determined based on the flow rate and pressure required for the low power output of the fuel cell and combined with the annular first jet channel.

[0048] The valve seat 3 includes a shell 3-1, an electromagnetic winding 3-2, a spring 3-3 and a valve core 3-4; the shell 3-1 is provided with a second air inlet 3-6 for communicating with the hydrogen supply system; a movable valve core 3-4 is installed in the cavity of the shell 3-1, and an electromagnetic winding 3-2 is installed in the cavity of the shell 3-1, and the valve core 3-4 is moved in the cavity of the shell 3-1 by energizing the electromagnetic winding 3-2; the other end of the secondary nozzle 4-2 is provided with a plurality of connecting holes 4-2-4 communicating with the first jet channel; the periphery of the valve core 3-4 is distributed as follows: The dry through hole 3-5 has a one-to-one correspondence with the phase angle of the through hole 3-5 and the connecting hole 4-2-4; the spring 3-3 is installed between the valve core 3-4 and the inner wall of the cavity of the shell 3-1. When the electromagnetic winding 3-2 is de-energized, the valve core 3-4 is fitted with the end face of the other end of the secondary nozzle 4-2 through the spring 3-3, so as to block the connection between the second jet channel and the through hole 3-5; when the electromagnetic winding 3-2 is energized, the valve core 3-4 is moved toward the second air inlet 3-6, so as to connect the first jet channel and the second jet channel with the second air inlet 3-6 respectively.

[0049] Working process: When the fuel cell output power is less than the set power, the electromagnetic winding 3-2 is de-energized, and the spring force of spring 3-3 causes the valve core 3-4 to mate with the other end face of the secondary nozzle 4-2, thereby connecting only the first jet channel to the second air inlet 3-6. The gas ejected from the first ejection channel creates a low-pressure area a at the nozzle outlet within the mixing chamber 1-1. When the fuel cell output power is greater than or equal to the set power, the electromagnetic winding 3-2 is energized, causing the valve core 3-4 to overcome the spring force of spring 3-3 and move toward the second air inlet 3-6. The first and second ejection channels are respectively connected to the second air inlet 3-6. The gases ejected from the first and second ejection channels jointly create a low-pressure area b within the mixing chamber. Low-pressure area A can entrain and mix the gas from the first air inlet 2, which then flows through the secondary nozzle 4-2 into low-pressure area b, thereby mixing the gas from the first air inlet 2 and the gas from the second air inlet 3-6 within the mixing chamber 1-1. The outlet of the chamber 1 is connected to the fuel cell stack.

[0050] The outer contour of the first section shell 4-2-1 is cylindrical, the outer contour of the second section shell 4-2-2 is conical, and the injection section 4-1-3 is a tapered hole, which is used to form a gradually expanding annular outlet at the outlet of the first jet channel.

[0051] The outer contour surface of the guiding end 4-2-3 is provided with a first guide surface 4-2-3-1 and a third guide surface 4-2-3-3 in sequence according to the flow direction. One side of the first guide surface 4-2-3-1 is smoothly transitioned to the second section shell 4-2-2, and a supporting force is applied to the gas at the outlet of the first introduction channel to keep the gas at the outlet of the first introduction channel moving horizontally at a high speed; the inner hole of the guiding end 4-2-3 located at the outlet of the second jet channel is provided with a second guide surface 4-2-3-2, which is used to keep the gas at the outlet of the second introduction channel moving horizontally at a high speed before the two introduction channels are mixed by radially diverting and constraining the gas at the outlet of the second introduction channel; the third guide surface 4-2-3-3 is a tapered cone surface, and the third guide surface 4-2-3-3 applies a supporting force to the mixed gas composed of the gas at the outlet of the first introduction channel and the jet gas. The supporting force is perpendicular to the wall movement direction of the mixed gas, so that the gas keeps moving at a high speed after mixing.

[0052] Example 2

[0053] On the basis of Example 1, Example 2 is as follows Figure 5 and Figure 6As shown, the second-section housing 4-2-2 is located within the converging section 4-1-2. The second-section housing 4-2-2 and the converging section 4-1-2 have the same taper. The injection section 4-1-3 is a tapered hole, and the taper of the third guide surface 4-2-3-3 is the same magnitude as the taper of the injection section 4-1-3, but in the opposite direction. That is, if the taper of the outer contour of the third guide surface 4-2-3-3 is positive β, then the taper of the injection section 4-1-3 is negative α. This creates a gradually diverging annular outlet at the exit of the first jet channel, generating a large low-pressure area a. Furthermore, the smaller cross-sectional area of ​​the first ejection channel enables a higher flow rate to be maintained even when the first inlet flow rate is low. The angle β between the third guide surface 4-2-3-3 and the axial direction is 4 to 15 degrees.

[0054] In embodiment 2, the first guide surface 4-2-3-1 is very short. In some embodiments, the outer contour surface of the guide end 4-2-3 is only the third guide surface 4-2-3-3. Figure 7 shown. Figure 7 In the embodiment, the inclination angle of the third guide surface 4-2-3-3 increases as the axial length of the guide end 4-2-3 increases. Figure 7 The third guide surface 4-2-3-3 has two sections, forming a first angle β1 and a first angle β2 respectively. The first angle β2 is greater than the first angle β1. In this way, the third guide surface 4-2-3-3 applies shear stress to the entrained jet gas. The mixed gas composed of the gas at the outlet of the second introduction channel and the gas entering the mixing chamber is inclined along the third guide surface 4-2-3-3 to cut into the gas at the outlet of the first introduction channel and mix, which can greatly alleviate the mixing process of the two airflows.

[0055] Example 3

[0056] On the basis of Example 1 or Example 2, Example 3 is as follows Figure 8 and Figure 9 As shown, the second section shell 4-2-2 is located in the tapered section 4-1-2, and the second section shell 4-2-2 and the tapered section 4-1-2 have the same taper. The outlet of the second guide surface 4-2-3-2 is provided with a diffuser section 4-2-3-4, which is tapered or in an arc shape with a gradual curve. Figure 10 As shown, the cone angle θ of the inner contour of the diffuser section 4-2-3-4 can be selected from 5° to 10°. The cone angle of the third guide surface 4-2-3-3 is 2β, and the cone angle 2β of the third guide surface 4-2-3-3 is greater than the cone angle θ of the inner contour of the diffuser section 4-2-3-4.

[0057] Simulation analysis:

[0058] Working condition settings: To compare the beneficial effects of the structure of the present invention compared to the existing technology, a unified working condition is used to simulate the single-stage injection and dual-stage injection modes. Under the single-stage injection condition, only the first injection channel is open. At this time, the fuel cell stack output current is 62.2A, the mass flow rate of pure hydrogen entering from the second air inlet is 0.19g / s, and the temperature is 25°C. The absolute pressure of the high-temperature mixed gas entering from the first air inlet is 131kPa, and its average temperature is 67°C. The composition of the mixed gas, measured by volume fraction, is H2:N2:H2O = 90%:5%:5%. Under the dual-stage injection condition, the first and second injection channels are opened simultaneously. At this time, the fuel cell stack output power is 155.5A, the mass flow rate of pure hydrogen entering from the second air inlet is 0.49g / s, and the temperature is 25°C. The absolute pressure of the high-temperature mixed gas entering from the first air inlet is 206 kPa, and its average temperature is 71° C. The composition of the mixed gas is measured by volume fraction, and the composition is H2:N2:H2O=85%:7%:8%.

[0059] like Figure 12 As shown, in the single-stage injection of the prior art, since the flow velocity at the outlet of the second jet channel of the secondary nozzle 4-2 is relatively high, there is a velocity boundary layer in the high-speed flow near the outlet of the second jet channel, and part of the fluid falls off due to the slow flow to form a vortex. When the working time is longer, the volume of the vortex core increases, which will affect the high-speed flow, reduce its kinetic energy, reduce the entrainment capacity, and combine to form an unstable flow to enter the mixing chamber, forming shock waves and other phenomena, affecting the diffusion effect and the outlet pressure, thereby reducing the supply pressure entering the fuel cell stack and affecting the working efficiency of the fuel cell stack system.

[0060] like Figure 13 As shown, in the prior art dual-stage ejector, since the first and second ejection channels are opened simultaneously, the second ejection channel has a larger cross-sectional area, which creates a low-pressure area near the high-speed flow at the outlet of the secondary nozzle 4-2, attracting the gas at the outlet of the primary nozzle for mixing. Therefore, the simultaneous operation of the two nozzles causes the intake air to mix with each other, resulting in energy loss and reduced high-speed flow energy. This affects the entrainment efficiency, causing instabilities such as shock waves and oscillations in the mixing chamber, and ultimately moving into the diffuser, affecting the diffuser effect and the ejector outlet pressure, thereby affecting the operating efficiency of the fuel cell stack system.

[0061] Taking the structure of Example 1 as an example, Figure 14 As shown in the figure, one end of the secondary nozzle extends out and the nozzle end face achieves the effect of axial steps at the outlet of the two injection channels. As can be seen in the figure, by guiding the high-speed flow gas at the outlet of the first injection channel, the following is avoided: Figure 12 The vortex and airflow near the nozzle outlet are unstable, and they mix closer to the isobaric chamber outlet and enter the isochoric chamber in a stable confluent form; Figure 15 As shown, one end of the secondary nozzle extends out of the end face of the primary nozzle, achieving the effect of axial steps at the outlets of the two ejection channels, preventing the front end of the multi-channel ejector from causing unstable phenomena such as vortexes and oscillations due to the simultaneous mixing of multiple airflows. In addition, the outer angle of the guide nozzle is reasonably set to guide the jet gas to move forward along the wall, maintaining a relatively high speed and uniform mixing with the outlet gas of the first ejection channel. At the same time, by reducing the radial velocity at the end of the guide nozzle, the mixing process of the outlet gas of the second ejection channel with the outlet gas of the first ejection channel and the jet gas is eased, energy loss is reduced, and the gas shear stress is used to make the gas mix evenly, enter the mixing chamber with a high-speed and stable airflow, and stably supply it to the fuel cell stack. As can be seen in the figure, the high-speed flow gases of the first ejection channel and the second ejection channel achieve a smooth transition and convergence at the end of the outlet axial step, avoiding the following: Figure 13 The mixed flow is uneven due to the vortex appearing near the nozzle outlet. At the same time, the second ejection channel is extended. Figure 13 In comparison, the high-speed area of ​​the outlet gas is generally offset to a position closer to the outlet of the isobaric chamber, and the kinetic energy loss is reduced.

[0062] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0063] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A double-stage ejector for preventing vortex generation, characterized in that: The device comprises a cavity, a valve seat and a nozzle, wherein one end of the cavity is an outlet, the other end of the cavity is provided with a first air inlet, a mixing chamber connected to the first air inlet is provided in the cavity, a nozzle is installed in the mixing chamber, a valve seat is installed at the inlet of the nozzle, two independent jet channels are provided in the nozzle, the valve seat is connected to the second air inlet, and the second air inlet is connected to the first jet channel or to the two jet channels through the action of the valve core of the valve seat; The nozzle includes a primary nozzle and a secondary nozzle, the primary nozzle is located in the mixing chamber, and the primary nozzle is installed on the other end of the chamber; the secondary nozzle is installed at one end of the primary nozzle, and one end of the secondary nozzle is inserted into the internal cavity of the primary nozzle, the space between the secondary nozzle shell and the internal cavity of the primary nozzle is the first jet channel, and the center hole in the secondary nozzle is the second jet channel; one end of the secondary nozzle extends out of the end face of the primary nozzle to prevent vortexes from being generated at the nozzle outlet; the distance from the end of the secondary nozzle extending out of the end face of the primary nozzle to the cross section at the mixing chamber outlet is NXP, and NXP is 0.8~1.1Dm, where Dm is the nominal diameter of the mixing chamber outlet; The internal cavity of the first-stage nozzle is sequentially provided with a transition section, a gradually contracting section, and an injection section according to the flow direction; the shell of the second-stage nozzle is sequentially provided with a first-section shell, a second-section shell, and a guide end according to the flow direction; the guide end is inserted into the injection section so that the cross-section of the first jet channel outlet is annular; one end of the guide end extends out of the end face of the injection section; the outer contour of the first-section shell is cylindrical, the outer contour of the second-section shell is conical, and the injection section is a tapered hole, which is used to form a gradually expanding annular outlet at the outlet of the first jet channel; The outer contour surface of the guide end is provided with a first guide surface and a third guide surface in sequence according to the flow direction. One side of the first guide surface smoothly transitions with the second section shell, and applies a supporting force to the gas at the outlet of the first injection channel to keep the gas at the outlet of the first injection channel moving horizontally; the inner hole of the guide end located at the outlet of the second jet channel is provided with a second guide surface, which radially diverts and constrains the gas at the outlet of the second injection channel to keep the gas at the outlet of the second injection channel moving horizontally before the two injection channels are mixed; the third guide surface is a tapered cone surface, and the mixed gas composed of the gas at the outlet of the second injection channel and the gas entering the mixing chamber is obliquely cut into the gas at the outlet of the first injection channel along the third guide surface, so as to alleviate the mixing of the two airflows.

2. The double-stage ejector for preventing vortex generation according to claim 1, characterized in that: The valve seat includes a shell, an electromagnetic winding, an elastic element and a valve core; a second air inlet is provided on the shell for connecting with the hydrogen supply system; a movable valve core is installed in the cavity of the shell, and an electromagnetic winding is installed in the cavity of the shell, and the valve core is moved in the cavity of the shell by energizing the electromagnetic winding; a plurality of connecting holes connected to the first jet channel are provided on the other end of the secondary nozzle; a plurality of through holes are distributed around the valve core, and the phase angles of the through holes and the connecting holes correspond one to one; the elastic element is installed between the valve core and the inner wall of the shell cavity, and when the electromagnetic winding loses power, the valve core is fitted with the end face of the other end of the secondary nozzle through the elastic element, so as to block the connection between the second jet channel and the through hole; when the electromagnetic winding is energized, the valve core is moved toward the second air inlet, so as to connect the first jet channel and the second jet channel with the second air inlet respectively.

3. The double-stage ejector for preventing vortex generation according to claim 1, characterized in that: The inclination angle of the third guide surface increases as the axial length of the guide end increases.

4. The double-stage ejector for preventing vortex generation according to claim 1, characterized in that: The angle between the third guide surface and the axial direction is 8 to 15 degrees.

5. The double-stage ejector for preventing vortex generation according to claim 1, characterized in that: The injection section is a tapered hole, and the taper of the third guide surface is the same as that of the tapered hole of the injection section, but in the opposite direction.

6. The double-stage ejector for preventing vortex generation according to claim 1, characterized in that: A diffuser section is provided at the outlet of the second guide surface. The taper of the inner contour of the diffuser section is a positive taper θ. The taper of the third guide surface is greater than the taper of the inner contour of the diffuser section.

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