A Roots pump with effective noise reduction

Abstract

The invention relates to the technical field of Roots pumps, and aims to provide a Roots pump with effective noise reduction. The technical scheme thereof is as follows: comprising a casing A, a reflux groove A is provided on the inner wall of an "8"-shaped cylinder of the casing A, the flow channel shape and area of ​​the reflux groove A are designed according to the laws of fluid mechanics and thermodynamics, and the reflux groove A can be used to control the reflux velocity of high-pressure gas; comprising a casing B and a wallboard B, a high-pressure gas cavity is provided inside the wallboard B, a high-pressure gas flow port is provided in the high-pressure gas cavity toward the side of the casing B, high-pressure gas outlets are provided on both side walls of the high-pressure exhaust cavity of the casing B, two reflux grooves B for buffering the high-pressure reflux gas are symmetrically provided on the end surface of the wallboard B toward the working cavity of the casing B, the flow channel shape and area of ​​the reflux groove B are designed according to the laws of fluid mechanics and thermodynamics, and the flow channel shape and area of ​​the reflux groove B are used to control the reflux velocity of the high-pressure gas. The invention has the advantages of effectively slowing down the reflux impact of high-pressure gas and reducing pump noise.

Description

Technical Field

[0001] The invention relates to the technical field of Roots pumps, and in particular to a Roots pump with effective noise reduction. Background Art

[0002] Roots pump is a positive displacement pump that uses two rotors with conjugated blades to move relative to each other in the working chamber to compress and transport gas. Since each impeller uses an involute, cycloid or circular envelope, the blade profile of each impeller is exactly the same, which can greatly reduce the complexity of impeller processing. CNC equipment is used during impeller processing. It is necessary to ensure that the two impellers can maintain a certain small gap between the two impeller surfaces when the two impellers rotate to any position under the premise that the center distance remains unchanged, so as to effectively control the leakage of high-pressure gas in the high-pressure chamber and ensure the efficient and stable operation of the Roots pump.

[0003] Existing three-leaf Roots pumps, such as Figure 1 and Figure 2 As shown, it includes a main oil tank 14 and an auxiliary oil tank 15. A housing A1 is arranged between the main oil tank 14 and the auxiliary oil tank 15. A working chamber 3 is arranged in the housing A1. A driving impeller coupling 16 and a driven impeller coupling 17 are arranged in the working chamber 3. A wall panel A2 is arranged at the end of the housing A1 along the length direction of the driving impeller coupling 16. A low-pressure air inlet 1001 is arranged on one side of the working chamber 3 of the housing A1. External power is input through the coupling at the shaft end of the driving impeller 4, and the driving impeller 4 drives the driven impeller 5 to rotate synchronously through the synchronous gear. The driving impeller 4 includes a first driving wheel blade peak 41, a second driving wheel blade peak 42 and a third driving wheel blade peak 43, and the driven impeller 5 includes a first driven wheel blade peak 51, a second driven wheel blade peak 52 and a third driven wheel blade peak 53. A high-pressure exhaust port 31 is provided on the other side of the working chamber 3 of the housing A1 , a high-pressure exhaust chamber 6 is provided outside the high-pressure exhaust port 31 , and a high-pressure exhaust port 7 is provided in the high-pressure exhaust chamber 6 .

[0004] like Figure 3 and Figure 4 As shown, the edge of the low-pressure air inlet 1001 is set as A', the position of the inner wall of the working chamber 3 at a distance of 120° from A' is set as B', and the intersection of the inner wall of the working chamber 3 and the high-pressure exhaust port 31 is set as C'. As the first driving wheel blade peak 41 rotates toward the inner wall of the working chamber 3 of the casing A1 and approaches the edge A' of the low-pressure air inlet 1001, at this time, the first driving wheel blade peak 41, the second driving wheel blade peak 42, the inner wall of the working chamber 3, and the wallboard A2 form a nearly closed cavity, which is called the elementary volume 13. At this time, since the first driving wheel blade peak 41 approaches the edge A' of the low-pressure air inlet 1001, the gas is blocked from being sucked into the elementary volume 13. At this time, it can be considered that the pressure of the elementary volume 13 is equal to that of the low-pressure air inlet 1001.

[0005] like Figure 4 and Figure 5 As shown, when the first driving wheel blade peak 41 approaches the edge A' of the low-pressure air inlet 1001, the second driving wheel blade peak 42 just approaches the inner wall B' of the working chamber 3. At this time, since the gap between the second driving wheel blade peak 42 and the inner wall of the working chamber 3 of the casing A1 and the impeller end face and the two wall panels A are very small, the high-pressure gas in the high-pressure exhaust chamber 6 does not leak significantly into the elementary volume 13, so the high-pressure gas will not cause obvious reflux gas impact on the elementary volume 13.

[0006] like Figure 6 and Figure 7 As shown, the active impeller 4 drives the driven impeller 5 to continue rotating through the synchronous gear, and drives the air in the cell volume 13 to move toward the high-pressure exhaust port 31. When the second active wheel blade peak 42 approaches the C' position where the high-pressure exhaust port 31 and the inner wall of the working chamber 3 meet, as the second active wheel continues to rotate, the gap between the second active wheel blade peak 42 and the C' position increases rapidly, and the cell volume 13 is connected to the high-pressure exhaust port 31. At this time, the high-pressure air in the high-pressure exhaust chamber 6 flows back into the cell volume 13 from the rapidly increasing gap, so that the pressure in the cell volume 13 increases rapidly to the pressure in the high-pressure exhaust chamber 6, thus generating a huge reflux air impact noise, which causes the Roots pump to have a large operating noise. It can be seen that if the high-pressure gas reflux process in the high-pressure exhaust chamber 6 becomes smooth and stable, the intensity of the high-pressure gas reflux impact can be reduced, which is the key point to reduce the operating noise of the Roots pump. Since the active impeller 4 and the driven impeller 5 in the working chamber 3 of the Roots pump are arranged in conjugate symmetry, the working principles of the left and right parts in the working chamber 3 of the Roots pump are the same. As the active impeller 4 and the driven impeller 5 continue to rotate synchronously and conjugately, as the high-pressure gas in the high-pressure exhaust chamber 6 flows back to the elementary volume 13 and is pressurized to the pressure of the high-pressure exhaust chamber 6, the impellers continue to rotate, and the high-pressure gas in the elementary volume 13 is continuously squeezed into the high-pressure exhaust chamber 6. At the same time, the low-pressure gas at the low-pressure inlet 1001 is continuously sucked into the elementary volume 13 formed subsequently, thereby realizing the continuous pressurization and delivery of the low-pressure gas by the Roots pump.

[0007] The Chinese patent with the announcement number CN205446032U discloses a Roots pump, including a casing, an air outlet, an air inlet, an air filter, and a muffler. An impeller is installed in the casing, and a roller is arranged at each end of the impeller. The impeller is fixed on a bearing, and a lubricating layer is arranged inside the casing. By arranging the air inlet filter, the air intake is filtered, thereby reducing the phenomenon of increased impeller working noise due to excessive dust in the air; the lubricating layer can reduce the friction loss of the inner wall of the casing and increase the service life of the casing.

[0008] Although this prior art can reduce air noise by filtering the intake air, it does not solve the problem of high-pressure gas reflux impact of Roots pumps in actual use, and the intake filter and silencer cannot reduce the noise intensity of the noise source, but can only play an auxiliary noise reduction effect. Therefore, only by reducing the high-pressure gas reflux impact can the noise of the Roots pump caused by the high-pressure gas reflux impact be effectively reduced, and the impact damage caused by the high-pressure gas reflux impact to the inside of the Roots pump can be reduced, the service life of the Roots pump can be extended, and the stability of the operation of the Roots pump can be maintained. Summary of the invention

[0009] The purpose of the present invention is to provide a Roots pump with effective noise reduction, which has the advantages of effectively alleviating the impact of high-pressure gas backflow and reducing the noise of the Roots pump.

[0010] The above technical objectives of the present invention are achieved through the following technical solutions:

[0011] A Roots pump with effective noise reduction comprises a casing A and a wall panel A, wherein the casing A comprises an "8"-shaped cylinder, wherein the "8"-shaped cylinder of the casing A and the wall panel A are combined to form a working chamber, wherein a low-pressure air inlet is arranged on one side of the working chamber, a high-pressure exhaust port is arranged on the other side of the working chamber, a high-pressure exhaust chamber is arranged outside the high-pressure exhaust port, and the high-pressure exhaust chamber is provided with a high-pressure exhaust port, and two identical reflux grooves A for controlling the reflux velocity of the high-pressure gas by utilizing the shape and area of ​​the flow channel are symmetrically opened on the wall of the "8"-shaped cylinder of the casing between the high-pressure exhaust chamber and the working chamber.

[0012] By adopting the above technical solution, when the Roots pump is started, the active impeller drives the driven impeller to rotate synchronously through the synchronous gear. When the first active impeller blade peak just rotates to the intersection of the inner wall of the casing working chamber and the inner wall of the low-pressure air inlet, at this time, the second active impeller blade peak just rotates to sweep the 120° arc range of the inner wall of the casing working chamber from the low-pressure air inlet. Here, it is also the position where the reflux groove A is about to open. The second active impeller blade peak continues to rotate, and the reflux groove A is opened. Since the gap between the second active impeller blade peak and the inner wall of the casing working chamber is very small, the high-pressure gas in the high-pressure gas chamber is forced to flow back to the elementary volume through the reflux groove to increase pressure. As the active impeller continues to rotate, the blade peak of the second active impeller sweeps across the reflux groove A at a uniform speed. Therefore, the flow area and shape of the reflux groove A will force the gas pressure in the elementary volume to increase linearly. When the blade peak of the second active wheel sweeps to the high-pressure exhaust port position as the impeller rotates, the pressure of the elementary volume is just equal to or close to the pressure of the gas in the high-pressure exhaust chamber, thereby greatly reducing the impact effect caused by the reflux of the high-pressure gas, thereby effectively reducing the noise of the Roots pump; the pressure change in the elementary volume of the working chamber on the other side is similar.

[0013] Furthermore, the flow channel shape and area of ​​the reflux groove A conform to the laws of fluid mechanics and thermodynamics, and the flow channel area of ​​the reflux groove A gradually expands.

[0014] By adopting the above technical solution, when the active impeller blade peak evenly sweeps the reflux groove A, since the flow channel shape of the reflux groove A is designed according to the laws of fluid mechanics and thermodynamics, the flow channel area of ​​the reflux groove A gradually expands, thereby forcing the gas pressure in the elementary volume to increase linearly, greatly reducing the impact effect caused by the reflux of high-pressure gas, thereby achieving the effect of further reducing the noise of the Roots pump.

[0015] Furthermore, the reflux groove A penetrates through the side wall of the "8"-shaped cylinder of the casing A close to the high-pressure exhaust chamber and is connected to the high-pressure exhaust chamber. The air inlet edge of the inner wall of the working chamber of the casing A located at the low-pressure air inlet is set as A, the starting edge of the reflux groove A opened on the inner wall of the working chamber is set as B, and the end edge of the reflux groove A opened on the inner wall of the working chamber is set as C. The end edge C of the reflux groove A is connected to the high-pressure exhaust chamber.

[0016] By adopting the above technical solution, when the active impeller drives the driven impeller to rotate synchronously through the synchronous gear and makes each blade peak of the impeller rotate and sweep the reflux groove A, the flow area and shape of the reflux groove A change in accordance with the laws of fluid mechanics and thermodynamics and are connected to the high-pressure exhaust chamber, thereby further ensuring that the gas pressure in the elementary volume increases linearly to the gas pressure in the high-pressure exhaust chamber, and finally achieving the effect of buffering and noise reduction.

[0017] Furthermore, the arc angle between the edge A of the air inlet and the starting edge B of the reflux groove A opened on the inner wall of the working chamber is α, α= , n is the number of impeller heads, and the angle between the edge A of the air inlet and the end edge C of the return groove A forms an impeller inclusion angle with an adjustable angle range.

[0018] By adopting the above technical solution, increasing the angle range of the impeller inclusion angle can prolong the high-pressure gas reflux time, thereby achieving the effect of further reducing the noise of the Roots pump.

[0019] Furthermore, a Roots pump with effective noise reduction may also include a casing B and a wall panel B, the casing B including an "8"-shaped cylinder, the "8"-shaped cylinder of the casing B and the wall panel B are combined to form a working chamber, a low-pressure air inlet is provided on one side of the working chamber, the edge of the low-pressure air inlet is set to A, a high-pressure exhaust port is provided on the other side of the working chamber, a high-pressure exhaust chamber is provided on the outer side of the high-pressure exhaust port, the high-pressure exhaust chamber is provided with a high-pressure exhaust port, a high-pressure gas chamber is provided inside the wall panel B, a high-pressure gas flow port is provided on the surface of the high-pressure gas chamber corresponding to the high-pressure exhaust chamber of the casing B, high-pressure gas outlets are provided on both side walls of the high-pressure exhaust chamber of the casing B, the high-pressure gas outlets are used to outlet the high-pressure gas in the high-pressure exhaust chamber of the casing B to the high-pressure gas chamber in the wall panel B, and two symmetrical reflux grooves B are provided on the end face of the wall panel B facing the working chamber of the casing B, which use the shape and area of ​​the flow channel to control the reflux speed of the high-pressure gas.

[0020] By adopting the above technical solution, when the Roots pump is started, the active impeller coupling drives the driven impeller to rotate synchronously through the synchronous gear. When the vertex of the outer edge of the first active impeller reaches position A, the second active impeller surface just covers the reflux groove B, and continues to rotate. The reflux groove B opens, and the high-pressure gas in the high-pressure cavity in the wall panel B is inflated into the unit volume through the reflux groove B on the wall panel B; the impeller continues to rotate, and when the first active impeller surface reaches the starting point of the reflux groove B, at this time, the pressure in the unit volume is equal to or close to the pressure in the high-pressure gas cavity, and the reflux pressure equalization ends. The reflux groove B will also force the gas pressure in the unit volume to increase linearly, thereby greatly reducing the impact intensity caused by the reflux of high-pressure gas and reducing air impact noise.

[0021] Furthermore, the flow channel shape and area of ​​the reflux groove B conform to the laws of fluid mechanics and thermodynamics, and the flow channel area of ​​the reflux groove B gradually expands.

[0022] By adopting the above technical solution, when the active impeller surface evenly sweeps the reflux groove B, since the flow channel shape of the reflux groove B is designed according to the laws of fluid mechanics and thermodynamics, the flow channel area of ​​the reflux groove B gradually expands, thereby forcing the gas pressure in the elementary volume to increase linearly, greatly reducing the impact effect caused by the reflux of high-pressure gas, thereby achieving the effect of further reducing the noise of the Roots pump.

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. A low-pressure air inlet is arranged on one side of the working chamber of the casing, and the "8"-shaped cylinder of the casing A is combined with the wallboard A to form a working chamber. A high-pressure exhaust port is opened on the other side of the working chamber, and a high-pressure exhaust chamber is arranged outside the high-pressure exhaust port. A reflux groove A for buffering high-pressure reflux gas is arranged on the "8"-shaped cylinder of the casing between the high-pressure exhaust chamber and the working chamber, thereby reducing the dynamic impact noise caused by the impact of high-pressure reflux gas on the gas in the unit volume, thereby achieving the effect of effectively reducing the noise of the Roots pump;

[0025] 2. The shape and flow area of ​​the reflux groove A are designed according to the laws of fluid mechanics and thermodynamics. The reflux groove A runs through the side wall of the working chamber of the casing A and communicates with the high-pressure exhaust chamber. The bottom of the reflux groove A is connected to the high-pressure exhaust port. The arc angle between the edge A of the air inlet and the starting edge B of the reflux groove A opened on the inner wall of the working chamber is 120°. By moving the edge A of the air inlet forward and the end point C of the reflux groove A backward, the inclusion angle can be increased to extend the reflux time of the high-pressure gas, thereby further reducing the noise of the Roots pump.

[0026] 3. By setting a high-pressure gas cavity inside the wall panel B, a high-pressure gas flow port is set on the side of the high-pressure gas cavity facing the casing B, and high-pressure gas outlets are opened on both side walls of the high-pressure exhaust cavity of the casing B. The high-pressure gas outlets guide the high-pressure gas in the high-pressure exhaust cavity of the casing B to the high-pressure gas cavity of the wall panel B. Two reflux grooves B for buffering the high-pressure reflux gas are symmetrically opened on the end surface of the wall panel B facing the working cavity of the casing B. When the vertex of the outer edge of the first active impeller reaches the A position, the end surface of the second active impeller just covers the reflux groove B, and continues to rotate. The reflux groove B opens, and the high-pressure gas is inflated into the elementary volume through the reflux groove B on the wall panel B. The impeller continues to rotate. When the end surface of the first active impeller reaches the starting point of the reflux groove B, at this time, the pressure in the elementary volume is equal to or close to the pressure in the high-pressure gas cavity, and the reflux pressure equalization ends at this time. Since the flow channel shape of the reflux groove B is designed according to the laws of fluid mechanics and thermodynamics, and the flow area and shape of the reflux groove B will force the gas pressure in the unit volume to increase linearly, thereby greatly reducing the impact intensity caused by the reflux of high-pressure gas and reducing air impact noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an overall cross-sectional view of an existing Roots pump in the background technology;

[0028] Figure 2 It is a cross-sectional view used in the background technology to reflect the positional relationship between the driving impeller and the driven impeller in the housing of the existing Roots pump;

[0029] Figure 3 It is a cross-sectional view used in the background technology to reflect the positional relationship between the driving impeller and the driven impeller in the initial starting state;

[0030] Figure 4 It is a cross-sectional view used in the background art to reflect the initial position relationship of the volume of the primitive unit in the working chamber of the Roots pump;

[0031] Figure 5 It is a cross-sectional view used in the background art to reflect the internal structural relationship of the working chamber when the elementary volume in the working chamber of the Roots pump is fully formed;

[0032] Figure 6 It is a cross-sectional view of the internal structure of the working chamber when the high-pressure gas reflux phenomenon occurs in the working chamber in the background technology;

[0033] Figure 7 It is a cross-sectional view of the internal structure of the working chamber of the Roots pump in the background technology when the high-pressure gas backflow effect in the working chamber is in the limit state;

[0034] Figure 8 It is a cross-sectional view used to reflect the positional relationship between the active impeller, the driven impeller and the return flow groove A in Embodiment 1;

[0035] Fig. 9 It is an overall schematic diagram for reflecting the positional relationship between the reflux groove A and the inner wall of the housing A in Embodiment 1;

[0036] Fig.10 A cross-sectional view showing the shape of the flow channel of the reflux groove A in Example 1;

[0037] Fig.11 This is a cross-sectional view used to reflect the positional relationship between the reflux groove A and the "8"-shaped cylinder in Example 1;

[0038] Fig.12 is a schematic diagram for illustrating the positional relationship between the return flow groove B and the wallboard B in Example 2;

[0039] Fig.13 It is a cross-sectional view used to reflect the positional relationship between the active impeller, the driven impeller and the return flow groove B in Embodiment 2;

[0040] Fig.14 It is a cross-sectional view used to reflect the position of the high-pressure gas cavity in the wall panel B in Example 2.

[0041] In the figure, 1, casing A; 1001, low-pressure air inlet; 2, wall panel A; 3, working chamber; 31, high-pressure exhaust port; 4, active impeller; 41, first active wheel blade peak; 42, second active wheel blade peak; 43, third active wheel blade peak; 5, driven impeller; 51, first driven wheel blade peak; 52, second driven wheel blade peak; 53, third driven wheel blade peak; 6, high-pressure exhaust chamber; 7, high-pressure exhaust port; 8, return flow groove A; 9, casing B; 91, high-pressure gas outlet; 10, wall panel B; 101, return flow groove B; 11, high-pressure gas chamber; 12, high-pressure gas flow port; 13, elementary volume; 14, main oil tank; 15, auxiliary oil tank; 16, active impeller coupling; 17, driven impeller coupling; 18, "8"-shaped cylinder. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0043] Embodiment 1:

[0044] A Roots pump that effectively reduces noise, such as Figure 8 As shown, the housing A1 includes an "8"-shaped cylinder 18, a low-pressure air inlet 1001 integrally formed on one side of the "8"-shaped cylinder 18, and a wall panel A2 (such as Figure 1 As shown in the figure, a working chamber 3 is formed, in which a pair of driving impellers 4 and driven impellers 5 with conjugated blades are arranged. The driving impeller 4 drives the driven impeller 5 to rotate synchronously through a synchronous gear. The driving impeller 4 includes a first driving wheel blade peak 41, a second driving wheel blade peak 42 and a third driving wheel blade peak 43, and the driven impeller 5 includes a first driven wheel blade peak 51, a second driven wheel blade peak 52 and a third driven wheel blade peak 53.

[0045] like Figure 8 and Fig. 9 As shown, a high-pressure exhaust port 31 is provided on one side of the working chamber 3 of the housing A1, a high-pressure exhaust chamber 6 is provided outside the high-pressure exhaust port 31, and the high-pressure exhaust chamber 6 is provided with a high-pressure exhaust port 7. A reflux groove A8 for buffering the high-pressure reflux gas is provided on the "8"-shaped cylinder 18 of the housing A1 located between the high-pressure exhaust chamber 6 and the working chamber 3. The flow channel shape and area of ​​the reflux groove A8 are designed according to the laws of fluid mechanics and thermodynamics, and the area of ​​the reflux groove A8 gradually increases, and the flow channel shape and area of ​​the reflux groove A8 are used to control the reflux speed of the high-pressure gas.

[0046] like Figure 8 and Fig. 9As shown, the reflux groove A8 penetrates the side wall of the "8"-shaped cylinder 18 of the casing A1 and is connected to the high-pressure exhaust chamber 6. The inner wall of the working chamber 3 of the casing A1 is located at the air inlet edge of the low-pressure air inlet 1001 and is set to A. The starting edge of the reflux groove A8 opened on the inner wall of the working chamber 3 is set to B, and the terminal edge of the reflux groove A8 opened on the inner wall of the working chamber 3 is set to C. The terminal edge C of the reflux groove A8 is connected to the high-pressure exhaust chamber 6. The arc angle between the air inlet edge A and the starting edge B of the reflux groove A8 opened on the inner wall of the working chamber 3 is α, α=(360°) / n, n is the number of impeller heads, and the angle between the air inlet edge A and the terminal edge C of the reflux groove A8 forms an impeller inclusion angle. The air inlet edge A can be moved forward, and the terminal edge C of the reflux groove A8 can be moved backward to increase the angle range of the impeller inclusion angle for extending the high-pressure gas reflux time.

[0047] like Fig.10 and Fig.11 As shown, the reflux groove A8 runs through the side wall of the working chamber 3 of the casing A1 and communicates with the high-pressure exhaust chamber 6, and the bottom of the reflux groove A8 is connected to the high-pressure exhaust port 31.

[0048] Embodiment 2:

[0049] A Roots pump that effectively reduces noise, such as Fig.12 , Fig.13 As shown, it includes a casing B 9 and a wall panel B 10. The "8"-shaped cylinder 18 of the casing B 9 and the wall panel B 10 are combined to form a working chamber 3. A low-pressure air inlet 1001 is provided on one side of the working chamber 3, and the edge of the low-pressure air inlet 1001 is set as A. A high-pressure exhaust port 31 is provided on the other side of the working chamber 3. A high-pressure exhaust chamber 6 is provided on the outer side of the high-pressure exhaust port 31, and the high-pressure exhaust chamber 6 is provided with a high-pressure exhaust port 7.

[0050] like Fig.12 and Fig.14 As shown, a high-pressure gas cavity 11 is provided inside the wall panel B10, and a high-pressure gas flow port 12 is provided on the side of the high-pressure gas cavity 11 facing the casing B9, and high-pressure gas outlets 91 are provided on both side walls of the high-pressure exhaust cavity 6 of the casing B9, and the high-pressure gas outlets 91 are used to guide the high-pressure gas in the high-pressure exhaust cavity 6 of the casing B9 into the high-pressure gas cavity 11 of the wall panel B10; two reflux grooves B101 for buffering the high-pressure reflux gas are symmetrically provided on the end surface of the wall panel B10 facing the working cavity 3 of the casing B9, and the flow channel shape and area of ​​the reflux groove B101 are designed according to the laws of fluid mechanics and thermodynamics, and the area of ​​the reflux groove B101 gradually increases, and the flow channel shape and area of ​​the reflux groove B101 are used to control the reflux speed of the high-pressure gas.

[0051] In Example 1 and Example 2, according to the ideal gas stagnation state adiabatic isentropic flow state equation: , where k is the gas constant, , is the Mach number of the airflow on the cross section, u is the airflow velocity on the flow channel, a is the local sound speed, and M=1 is the dividing point between supersonic flow and subsonic flow in the flow channel. When M=1, , for air k=1.4, 1.892929, Roots pump is used under standard atmospheric conditions, =1.892929 =1.892929 101.325kPa=191.80kPa.

[0052] When the output pressure of the Roots pump is higher than 191.80 kPa, the high-pressure gas in the high-pressure exhaust chamber 6 and the high-pressure gas chamber 11 flows back into the elementary volume 13 from the reflux port of the reflux groove A 8 or the reflux groove B 101. At this time, a supersonic flow will appear at the reflux port of the reflux groove A 8 or the reflux groove B 101, while a subsonic flow will appear when the pressure is lower than 191.80 kPa. The flow channel calculation of the reflux groove A 8 and the reflux groove B 101 is calculated according to the supersonic flow and subsonic flow states respectively.

[0053] The present patent application is also applicable to negative pressure Roots pumps. The present specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading the present specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A Roots pump with effective noise reduction, comprising a housing (1) and a wall panel A (2), characterized in that: The housing (1) comprises an "8"-shaped cylinder (18), the "8"-shaped cylinder (18) of the housing (1) and the wall panel A (2) are combined to form a working chamber (3), one side of the working chamber (3) is provided with a low-pressure air inlet (1001), the other side of the working chamber (3) is provided with a high-pressure exhaust port (31), a high-pressure exhaust chamber (6) is provided outside the high-pressure exhaust port (31), the high-pressure exhaust chamber (6) is provided with a high-pressure exhaust port (7), and two identical reflux grooves (8) are symmetrically provided on the wall of the housing (8) shaped cylinder (18) between the high-pressure exhaust chamber (6) and the working chamber (3) for controlling the reflux velocity of the high-pressure gas by utilizing the shape and area of ​​the flow channel; the flow channel shape of the reflux groove (8) is The shape and area conform to the laws of fluid mechanics and thermodynamics, and the flow channel area of ​​the reflux groove (8) gradually expands; the reflux groove (8) penetrates the side wall of the "8"-shaped cylinder (18) arranged on the housing (1) close to the high-pressure exhaust chamber (6) and communicates with the high-pressure exhaust chamber (6); the air inlet edge of the inner wall of the working chamber (3) of the housing (1) located at the low-pressure air inlet (1001) is set as A, the starting edge of the reflux groove (8) on the inner wall of the working chamber (3) is set as B, and the end edge of the reflux groove (8) on the inner wall of the working chamber (3) is set as C, and the arc angle between the air inlet edge A and the starting edge B of the reflux groove (8) on the inner wall of the working chamber (3) is α, α=(360°) / n , n is the number of impeller heads, the angle between the air inlet edge A and the terminal edge C of the return groove one (8) forms an impeller inclusion angle with an adjustable angle range; the terminal edge C of the return groove one (8) is connected to the high-pressure exhaust chamber (6), the air inlet edge A can be moved forward, and the terminal edge C of the return groove one (8) can be moved backward to increase the angle range of the impeller inclusion angle for extending the high-pressure gas reflux time; the flow channel calculation of the return groove one (8) is calculated separately according to the supersonic flow and subsonic flow states.

2. A Roots pump with effective noise reduction, comprising a casing 2 (9) and a wall panel B (10), characterized in that: The second housing (9) comprises an "8"-shaped cylinder (18), the "8"-shaped cylinder (18) of the second housing (9) and the wall panel B (10) are combined to form a working chamber (3), a low-pressure air inlet (1001) is provided on one side of the working chamber (3), the edge of the low-pressure air inlet (1001) is set as A, a high-pressure exhaust port (31) is provided on the other side of the working chamber (3), a high-pressure exhaust chamber (6) is provided on the outer side of the high-pressure exhaust port (31), the high-pressure exhaust chamber (6) is provided with a high-pressure exhaust port (7), a high-pressure gas chamber (11) is provided inside the wall panel B (10), and a high-pressure gas flow port (12) is provided on the surface of the high-pressure gas chamber (11) corresponding to the high-pressure exhaust chamber (6) of the second housing (9) ), high-pressure gas outlets (91) are provided on both side walls of the high-pressure exhaust chamber (6) of the second housing (9), and the high-pressure gas outlets (91) are used to discharge the high-pressure gas in the high-pressure exhaust chamber (6) of the second housing (9) to the high-pressure gas chamber (11) in the wall panel B (10), and two reflux grooves (101) are symmetrically provided on one side end surface facing the working chamber (3) of the second housing (9) for controlling the reflux velocity of the high-pressure gas by utilizing the shape and area of ​​the flow channel; the shape and area of ​​the flow channel of the second reflux groove (101) conform to the laws of fluid mechanics and thermodynamics, and the flow channel area of ​​the second reflux groove (101) gradually expands; the flow channel of the second reflux groove (101) is calculated according to the supersonic flow and subsonic flow states respectively.

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