Venturi mixer and natural gas engine

Abstract

This application relates to a Venturi mixer and a natural gas engine. The Venturi mixer includes a primary Venturi tube and a secondary Venturi tube. Air enters through the inlet of the primary Venturi tube, and a natural gas inlet is located at its outlet, allowing natural gas to enter the primary Venturi tube. The inlet of the secondary Venturi tube is connected to the outlet of the primary Venturi tube, and an exhaust gas inlet is located at its inlet, allowing exhaust gas to enter the secondary Venturi tube. By incorporating the primary Venturi tube, a negative pressure is created inside, accelerating the air as it enters the primary Venturi tube, which then flows into the secondary Venturi tube. The secondary Venturi tube also creates a negative pressure inside, generating suction for the natural gas and exhaust gas, enhancing the driving force for exhaust gas recirculation, thereby improving the exhaust gas recirculation rate.

Description

Technical Field

[0001] This application relates to the field of engine technology, and in particular to Venturi mixers and natural gas engines. Background Technology

[0002] With increasingly stringent emission regulations, EGR (Exhaust Gas Recirculation) technology has seen significant development in the engine field. In natural gas engines, EGR technology is also being used more and more widely. Introducing EGR can suppress knocking in natural gas engines, reduce NOx (nitrogen oxides) emissions, and improve engine fuel economy.

[0003] The combustible mixture in a natural gas engine consists of three parts: air, EGR exhaust gas, and natural gas. An EGR natural gas engine's mixer is divided into a gas mixer and an exhaust gas mixer. The gas mixer mixes natural gas with fresh air, while the exhaust gas mixer mixes the gas mixture formed in the gas mixer with the EGR exhaust gas taken from the exhaust pipe.

[0004] However, in related technologies, there are issues such as insufficient EGR intake driving force and low EGR rate, especially under low and medium load conditions of the engine. Due to the low EGR pressure on the exhaust side, more EGR cannot be introduced to increase the EGR rate, resulting in relatively low thermal efficiency of the engine under low and medium load conditions. Summary of the Invention

[0005] Therefore, it is necessary to provide a Venturi mixer and natural gas engine to address the problems of insufficient EGR intake driving force and low EGR rate.

[0006] A Venturi mixer, comprising:

[0007] A primary venturi tube, wherein the inlet of the primary venturi tube is configured to allow air to enter, and the outlet end of the primary venturi tube is provided with a natural gas inlet, wherein the natural gas inlet is configured to allow natural gas to enter the primary venturi tube;

[0008] A secondary venturi tube is provided, the inlet of which is connected to the outlet of the primary venturi tube. An exhaust gas inlet is provided at the inlet end of the secondary venturi tube, which is configured to allow exhaust gas to enter the secondary venturi tube. The air, the natural gas and the exhaust gas are mixed in the secondary venturi tube and then discharged from the outlet of the secondary venturi tube.

[0009] In one embodiment, the diameter at the minimum diameter of the first-stage Venturi tube is smaller than the diameter at the minimum diameter of the second-stage Venturi tube.

[0010] In one embodiment, the secondary venturi tube includes:

[0011] The first connecting pipe has its inlet connected to the outlet of the first-stage venturi tube. The diameter of the first connecting pipe gradually increases from the end connected to the first-stage venturi tube to the other end. The exhaust gas inlet is located on the first connecting pipe.

[0012] The second connecting pipe has its inlet connected to the outlet of the first connecting pipe, and its diameter gradually decreases from the end connected to the first connecting pipe to the other end.

[0013] In one embodiment, the diameter at the minimum diameter of the second connecting pipe is not less than the diameter at the minimum diameter of the first-stage venturi pipe.

[0014] In one embodiment, the secondary venturi tube further includes:

[0015] A transition pipe, the inlet of which is connected to the outlet of the second connecting pipe, and the diameter of the transition pipe gradually increases from the end connected to the second connecting pipe to the other end.

[0016] A natural gas engine gas supply system includes a mixer outlet pipe and a Venturi mixer as described above, wherein the inlet of the mixer outlet pipe is connected to the outlet of the secondary Venturi pipe.

[0017] In one embodiment, the outlet diameter of the mixer outlet pipe is not less than the inlet diameter of the first-stage venturi tube.

[0018] In one embodiment, the mixer outlet pipe includes:

[0019] The main exhaust pipe has its inlet connected to the outlet of the secondary venturi tube.

[0020] A bypass pipe is provided, with both ends connected to the main exhaust pipe. The two connection points between the bypass pipe and the main exhaust pipe are arranged at intervals along the flow direction of the airflow in the main exhaust pipe. The diameter of the bypass pipe is smaller than the diameter of the main exhaust pipe. The airflow in the main exhaust pipe flows back to the main exhaust pipe through the bypass pipe.

[0021] In one embodiment, at least two bypass pipes are provided, and when there are more than two bypass pipes, the lengths of the bypass pipes are in a geometric sequence.

[0022] In one embodiment, the ratio of the diameter of the bypass pipe to the diameter of the main outlet pipe is less than 0.5.

[0023] The aforementioned Venturi mixer, by incorporating a primary Venturi tube, creates a negative pressure within it, accelerating air as it enters. This accelerated air then flows into a secondary Venturi tube. The secondary Venturi tube, also creating a negative pressure, exerts suction on the natural gas and exhaust gases, enhancing the drive for exhaust gas recirculation and thus increasing the exhaust gas recirculation rate. This is particularly beneficial under low-load conditions in natural gas engines, where the low exhaust gas pressure limits the intake of more exhaust gas to improve the recirculation rate. In this case, the Venturi mixer in this embodiment can draw in more exhaust gas, enhancing the drive for exhaust gas recirculation and increasing the recirculation rate under low-load conditions, thereby improving the engine's thermal efficiency under these conditions. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the planar structure of a natural gas engine gas supply system provided in one embodiment of this application.

[0025] Figure 2 This is a schematic diagram of the planar structure of a Venturi mixer provided in one embodiment of this application.

[0026] Figure 3 This is a three-dimensional structural diagram of a natural gas engine gas supply system provided in one embodiment of this application.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Venturi mixer;

[0029] 11. First-stage Venturi tube; 110. First throat; 111. Natural gas inlet; 112. Air inlet;

[0030] 12. Secondary Venturi tube; 120. Second throat; 121. First connecting pipe; 1211. Exhaust gas inlet; 122. Second connecting pipe; 123. Transition pipe;

[0031] 2. Mixer outlet pipe; 21. Main outlet pipe; 22. Bypass pipe. Detailed Implementation

[0032] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0033] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0034] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0036] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0037] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0038] See Figure 1 , Figure 1 A schematic plan view of a natural gas engine gas supply system provided in one embodiment of this application is shown. The natural gas engine gas supply system includes a Venturi mixer 1 and a mixer outlet pipe 2. Figure 1 The structure of Venturi mixer 1 is shown in the dashed box on the left. Figure 1 The structure of the mixer outlet pipe 2 is shown in the dashed box on the right. The Venturi mixer 1 mixes air, natural gas, and EGR exhaust gas, and the mixed gas is supplied to the natural gas engine (not shown in the figure) via the mixer outlet pipe 2. In this embodiment, both the Venturi mixer 1 and the mixer outlet pipe 2 are improved. By improving the Venturi mixer 1, the EGR intake drive capability is enhanced, increasing the EGR rate in the low-load range of the engine, thereby improving the thermal efficiency of the natural gas engine. By improving the mixer outlet pipe 2, the exhaust pulse kinetic energy is fully utilized, enhancing the mixing function and improving the intake uniformity of each cylinder of the engine, thus improving the combustion consistency of each cylinder.

[0039] See Figure 2 , Figure 2 A schematic diagram of the planar structure of a Venturi mixer provided in one embodiment of this application is shown below. Figure 1 and Figure 2 The structure of the Venturi mixer 1 is described in detail.

[0040] Specifically, the Venturi mixer 1 includes a primary Venturi tube 11 and a secondary Venturi tube 12. The inlet of the primary Venturi tube 11 is configured as an air inlet 112, which is used to supply air into the primary Venturi tube 11. The outlet end of the primary Venturi tube 11 is configured as a natural gas inlet 111, which is used to supply natural gas into the primary Venturi tube 11. The inlet of the secondary Venturi tube 12 is connected to the outlet of the primary Venturi tube 11. The inlet end of the secondary Venturi tube 12 is configured as an exhaust gas inlet 1211, which is used to supply exhaust gas into the secondary Venturi tube 12. After the air, natural gas, and exhaust gas are mixed in the secondary Venturi tube 12, they are discharged from the outlet of the secondary Venturi tube 12.

[0041] By setting up a primary Venturi tube 11, a negative pressure is created inside the primary Venturi tube 11, causing air to accelerate into it. The accelerated air then enters the secondary Venturi tube 12. The secondary Venturi tube 12 also creates a negative pressure inside, generating suction for the natural gas and exhaust gas, enhancing the driving force for exhaust gas recirculation and thus improving the exhaust gas recirculation rate. This is particularly useful under low-load conditions in natural gas engines, where the exhaust gas pressure is low, limiting the introduction of more exhaust gas to increase the exhaust gas recirculation rate. In this case, the Venturi mixer in this embodiment can draw in more exhaust gas, enhancing the driving force for exhaust gas recirculation and improving the exhaust gas recirculation rate under low-load conditions, thereby increasing the engine's thermal efficiency under these conditions.

[0042] It should be noted that, according to the Venturi effect, when wind blows over an obstruction, the air pressure near the upper port on the leeward side of the obstruction is relatively low, thus creating an adsorption effect and causing airflow. Therefore, in some embodiments, obstructions are placed inside the primary Venturi tube 11 and the secondary Venturi tube 12 to draw airflow into the tubes. In this embodiment, the first throat 110 is formed by reducing the diameter at one end of the primary Venturi tube 11, and similarly, the second throat 120 is formed by reducing the diameter at one end of the secondary Venturi tube 12. Because the diameters of the first throat 110 and the second throat 120 are abruptly reduced, they obstruct the airflow, thereby creating an adsorption force on the airflow at the inlet of the Venturi tubes.

[0043] Optionally, the ratio of the diameter of the first throat 110 to the inlet diameter of the first-stage venturi tube 11 is generally between 0.45 and 0.55 to accelerate the air. At the same time, the size of the first throat 110 needs to take into account the air intake requirements of the natural gas engine, and the throttling effect of the first throat 110 should not affect the total air intake of the natural gas engine.

[0044] Optionally, the minimum diameter of the first-stage venturi 11 is smaller than the minimum diameter of the second-stage venturi 12. That is, the diameter of the second throat 120 is larger than the diameter of the first throat 110, so as to enable the second-stage venturi 12 to draw in natural gas and exhaust gas.

[0045] The outlet diameter of the secondary venturi tube 12 should not be less than the effective diameter of the natural gas engine intake passage. Generally, the outlet diameter of the secondary venturi tube 12 should not be less than the inlet diameter of the primary venturi tube 11.

[0046] Optionally, the natural gas inlet 111 and the exhaust gas inlet 1211 are arranged at the inlet of the secondary venturi tube 12. Considering the risk of condensate freezing and blockage and the high gas density of the exhaust gas, in this embodiment, the natural gas inlet 111 and the exhaust gas inlet 1211 are arranged at the upper part of the corresponding venturi tube.

[0047] The primary Venturi tube 11 and the secondary Venturi tube 12 can be integrated into a single unit, connected to form a two-stage Venturi mixer 1, which is relatively easy to manufacture and makes it easier to ensure sealing. It is understood that in some other embodiments, the primary Venturi tube 11 and the secondary Venturi tube 12 can also be configured as separate units, sealed together by snap-fit ​​or threaded connection. An auxiliary pipe can also be provided to connect the primary Venturi tube 11 and the secondary Venturi tube 12. In other embodiments, the gas from the outlet of the primary Venturi tube 11 can be directly introduced into the vicinity of the second throat 120 in the secondary Venturi tube 12 through an auxiliary pipe, and various enhancement effects can be achieved by adjusting the distance between the auxiliary pipe and the second throat 120 or by designing the auxiliary pipe.

[0048] Specifically, such as Figure 1 and Figure 2 As shown, the secondary venturi tube 12 includes a first connecting pipe 121 and a second connecting pipe 122. The inlet of the first connecting pipe 121 is connected to the outlet of the primary venturi tube 11, and the diameter of the first connecting pipe 121 gradually increases from the end connected to the primary venturi tube 11 to the other end. An exhaust gas inlet 1211 is located on the first connecting pipe 121. The inlet of the second connecting pipe 122 is connected to the outlet of the first connecting pipe 121, and the diameter of the second connecting pipe 122 gradually decreases from the end connected to the first connecting pipe 121 to the other end. Optionally, the first connecting pipe 121 and the second connecting pipe 122 can also be an integral, one-piece structure.

[0049] The exhaust gas inlet 1211 is located at one end of the inlet of the first connecting pipe 121. By configuring the first connecting pipe 121 with a gradually increasing diameter from the end connected to the first-stage Venturi tube 11 to the other end, a gradually increasing space is provided for the entry of natural gas and exhaust gas, thereby reducing the resistance of natural gas and exhaust gas entering the second-stage Venturi tube 12. By configuring the diameter of the second connecting pipe 122 with a gradually decreasing diameter from the end connected to the first connecting pipe 121 to the other end, the aforementioned second throat 120 is formed at the outlet of the second connecting pipe 122, thereby creating a Venturi effect within the second connecting pipe 122 to create suction on the natural gas and exhaust gas entering the first connecting pipe 121, accelerating the flow of natural gas, especially exhaust gas, into the second connecting pipe 122.

[0050] Generally, the diameter at the minimum diameter of the second connecting pipe 122 is not less than the diameter at the minimum diameter of the first-stage venturi pipe 11, so as to realize the function of the second connecting pipe 122 for the intake of natural gas and exhaust gas.

[0051] Furthermore, in order to facilitate connection with the mixer outlet pipe 2, the secondary venturi tube 12 also includes a transition pipe 123. The inlet of the transition pipe 123 is connected to the outlet of the second connecting pipe 122. The diameter of the transition pipe 123 gradually increases from the end connected to the second connecting pipe 122 to the other end, so as to achieve the same diameter as the mixer outlet pipe 2, thereby facilitating the sealed connection between the transition pipe 123 and the mixer outlet pipe 2.

[0052] In some embodiments, the primary venturi tube 11, the first connecting tube 121, the second connecting tube 122, and the transition tube 123 are an integral structure. It is understood that in some other embodiments, one or more of the tubes can be set separately, as long as the same effect can be achieved after assembly.

[0053] The inlet of the mixer outlet pipe 2 is connected to the outlet of the secondary venturi pipe 12, that is, the inlet end of the mixer outlet pipe 2 is connected to the outlet end of the transition pipe 123. Generally, the outlet diameter of the mixer outlet pipe 2 is not less than the inlet diameter of the primary venturi pipe 11.

[0054] Figure 3 A three-dimensional structural schematic diagram of a natural gas engine gas supply system provided in one embodiment of this application is shown. The following is in conjunction with… Figures 1-3 The structure of the mixer outlet pipe 2 is described in detail.

[0055] In a manifold single-point injection natural gas engine, the air-fuel mixture uniformity can be divided into temporal and spatial dimensions. Temporal uniformity refers to the uniformity of air intake in each cylinder over a period of time as the cylinder valves open and close sequentially. Spatial uniformity refers to the uniformity of the air-fuel mixture within the intake chamber space after the mixer at a specific moment. Experimental studies have shown that temporal uniformity is more important than spatial uniformity because even if the spatial uniformity of the air-fuel mixture is excellent, the effects of exhaust pulses and valve opening and closing can still lead to uneven air intake in each cylinder, resulting in suboptimal engine performance.

[0056] In this embodiment, the mixer outlet pipe 2 is improved to address the aforementioned problems. Specifically, the mixer outlet pipe 2 includes a main outlet pipe 21 and a bypass pipe 22. The inlet of the main outlet pipe 21 is connected to the outlet of the secondary venturi tube 12, and the inlet of the main outlet pipe 21 is specifically connected to the outlet of the transition pipe 123. The diameter of the main outlet pipe 21 is the same as the outlet diameter of the transition pipe 123 for easy connection. Both ends of the bypass pipe 22 are connected to the main outlet pipe 21, and the two connection points between the bypass pipe 22 and the main outlet pipe 21 are arranged at intervals along the flow direction of the airflow in the main outlet pipe 21. The diameter of the bypass pipe 22 is smaller than the diameter of the main outlet pipe 21, and the airflow in the main outlet pipe 21 flows back to the main outlet pipe 21 through the bypass pipe 22.

[0057] As the intake and exhaust valves of the natural gas engine open and close, the exhaust gas entering the intake manifold exhibits a certain regular pressure fluctuation. Within the mixer outlet pipe 2, when the EGR exhaust pressure is high, the proportion of EGR in the intake gas is high; conversely, when the EGR exhaust pressure is low, the proportion of EGR in the intake gas is low. In other words, the proportion of EGR is uneven along the spatial dimension of the intake manifold. In this embodiment, by setting a bypass pipe 22 to bypass the main outlet pipe 21, some gas can shorten its journey and reach the natural gas engine inlet earlier. This allows for the balancing of EGR pulse fluctuations before the natural gas engine inlet, balancing the impact of exhaust pulses and valve opening and closing on the exhaust gas in the mixture. This achieves uniform EGR intake across all cylinders of the engine over time, thereby improving the consistency of each cylinder and enhancing the overall performance of the engine.

[0058] Optionally, refer to Figure 3 The main exhaust pipe 21 is configured with a bent structure, and the main exhaust pipe 21 is bent into a V shape. The bypass pipe 22 is set in the V-shaped space of the main exhaust pipe 21 to shorten the airflow path.

[0059] Optionally, at least two bypass pipes 22 are provided. When there are more than two bypass pipes 22, the lengths of the bypass pipes 22 are in a geometric sequence to achieve a better balance effect.

[0060] Furthermore, the ratio of the diameter of the bypass pipe 22 to the diameter of the main outlet pipe 21 is generally less than 0.5. At this ratio, a better EGR pulse fluctuation balance effect can be achieved.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A Venturi mixer, characterized in that, include: A primary venturi tube (11) is provided with an inlet for air to enter and a natural gas inlet (111) is provided at the outlet end of the primary venturi tube (11) for natural gas to enter the primary venturi tube (11). A secondary venturi tube (12) is provided with an exhaust gas inlet (1211) at its inlet end. The exhaust gas inlet (1211) is configured to allow exhaust gas to enter the secondary venturi tube (12). The air, the natural gas and the exhaust gas are mixed in the secondary venturi tube (12) and discharged from the outlet of the secondary venturi tube (12). The secondary venturi tube (12) includes: The first connecting pipe (121) has its inlet connected to the outlet of the first-stage venturi tube (11). The diameter of the first connecting pipe (121) gradually increases from one end connected to the first-stage venturi tube (11) to the other end. The exhaust gas inlet (1211) is located on the first connecting pipe (121). The inlet of the second connecting pipe (122) is connected to the outlet of the first connecting pipe (121), and the diameter of the second connecting pipe (122) gradually decreases from the end connected to the first connecting pipe (121) to the other end.

2. The Venturi mixer according to claim 1, characterized in that, The diameter at the minimum diameter of the first-stage Venturi tube (11) is smaller than the diameter at the minimum diameter of the second-stage Venturi tube (12).

3. The Venturi mixer according to claim 1, characterized in that, The diameter at the minimum diameter of the second connecting pipe (122) is not less than the diameter at the minimum diameter of the first-stage venturi pipe (11).

4. The Venturi mixer according to claim 3, characterized in that, The secondary venturi tube (12) also includes: The transition pipe (123) has its inlet connected to the outlet of the second connecting pipe (122), and the diameter of the transition pipe (123) gradually increases from the end connected to the second connecting pipe (122) to the other end.

5. A natural gas engine gas supply system, characterized in that, Includes a mixer outlet pipe (2) and a Venturi mixer as described in any one of claims 1-4, wherein the inlet of the mixer outlet pipe (2) is connected to the outlet of the secondary Venturi pipe (12).

6. The natural gas engine gas supply system according to claim 5, characterized in that, The outlet diameter of the mixer outlet pipe (2) is not less than the inlet diameter of the first-stage venturi pipe (11).

7. The natural gas engine gas supply system according to claim 5, characterized in that, The mixer outlet pipe (2) includes: The main exhaust pipe (21) is connected to the outlet of the secondary venturi pipe (12). A bypass pipe (22) is provided, with both ends of the bypass pipe (22) connected to the main outlet pipe (21). The two connection points of the bypass pipe (22) and the main outlet pipe (21) are arranged at intervals along the flow direction of the airflow in the main outlet pipe (21). The diameter of the bypass pipe (22) is smaller than the diameter of the main outlet pipe (21). The airflow in the main outlet pipe (21) flows back to the main outlet pipe (21) through the bypass pipe (22).

8. The natural gas engine gas supply system according to claim 7, characterized in that, There are at least two bypass pipes (22). When there are more than two bypass pipes (22), the lengths of the bypass pipes (22) are in a geometric sequence.

9. The natural gas engine gas supply system according to claim 7, characterized in that, The ratio of the diameter of the bypass pipe (22) to the diameter of the main outlet pipe (21) is less than 0.5.

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