CN204253367U - The screw rod of screw vacuum pump - Google Patents

Abstract

The utility model provides a kind of screw rod of screw vacuum pump, belongs to vacuum pump technology field.The screw rod it solving existing screw vacuum pump cannot meet the problem of specific process conditions.In the screw rod of this screw vacuum pump, in suction unit, the spiral fluted number of turns is 0.75 ~ 1.25 circle; When on compression transition part, the spiral fluted number of turns is 1 circle, in exhaust portion, the spiral fluted number of turns is greater than 3 circles; When on compression transition part, the spiral fluted number of turns is greater than 1 circle, in exhaust portion, the spiral fluted number of turns is 1.75 ~ 4 circles.The screw rod of this screw vacuum pump makes vacuum pump ultimate vacuum higher, and performance is more stable, and manufacturing expense increases hardly, and then makes screw vacuum Type of pump more, and application is more extensive.Adopt the screw vacuum pump of this varying pitch screw to be wound around the number of turns by suitably improving spiral fluted, and then optimize compressed capability, improve the exhaust efficiency of exhaust portion, slow down exhaust portion air and can not arrange and excessive compression phenomenon, and then effectively reduce specific energy consumption.

Description

The screw rod of screw vacuum pump

Technical field

The utility model belongs to vacuum pump technology field, relates to a kind of screw vacuum pump, particularly a kind of screw rod of screw vacuum pump.

Background technique

Screw vacuum pump has long and convenience of maintenance period, environmental protection, highly reliable, high efficiency and the easy advantage such as manipulation, and thus refer and synthesize in a lot of technique, screw vacuum pump replacement water ring vaccum pump, sliding valve vacuum pump, other wet vacuum pump become inexorable trend.

Claimant once proposed a kind of screw rod of screw vacuum pump, and be documented in (application publication number: CN102937094A) in Chinese patent literature, adopt the vacuum pump of this screw rod relatively to provide the optimal selection of energy requirement, noise, internal operating temperature, structure space and manufacturing expense with vacuum pump before, also there is application advantage comparatively widely.

In the part of production environment of some electronic component, require that ultimate vacuum is at below 0.5Pa, and require to vacuumize for a long time.Still meet below 0.5Pa ultimate vacuum to make the vacuum pump of the above-mentioned screw rod of employing and vacuumize production requirement for a long time, at present, the technological scheme that those skilled in the art easily expect is the gap reduced between screw rod and screw rod and between screw rod and the pump housing, although the program can realize above-mentioned production requirement, but there is following defect: the requirement on machining accuracy of the parts such as screw rod and the pump housing improves, the assembly precision of vacuum pump also needs to improve, and thus produces the problem that manufacturing expense increases substantially; Expand with heat and contract with cold because parts exist simultaneously, after gap shrinks, lessen the Security that vacuum pump runs.

Summary of the invention

The utility model proposes a kind of screw rod of screw vacuum pump, the technical problems to be solved in the utility model how to improve ultimate vacuum and the guarantee vacuum pump safety in operation of screw vacuum pump, can not produce again the problem that manufacturing expense significantly improves.

The technical problem that will solve of the present utility model realizes by following technical proposal:

The screw rod of this screw vacuum pump, comprises the cylindrical body of rod, and the outer side surface of the body of rod has a spiral chute, spiral fluted two-port lays respectively in the both ends of the surface of the body of rod; One end of the body of rod is suction unit, and the other end is exhaust portion, is compression transition part between suction unit and exhaust portion; In suction unit, spiral fluted pitch is constant, and in exhaust portion, spiral fluted pitch is constant, and in exhaust portion, spiral fluted pitch is less than spiral fluted pitch in suction unit; On compression transition part, spiral chute one end connects with spiral chute in suction unit, and the other end connects with spiral chute in suction unit, and on compression transition part, spiral chute passes through, and pitch is non-linear gradual to be reduced; In suction unit, the spiral fluted number of turns is 0.75 ~ 1.25 circle; When on compression transition part, the spiral fluted number of turns is 1 circle, in exhaust portion, the spiral fluted number of turns is greater than 3 circles; When on compression transition part, the spiral fluted number of turns is greater than 1 circle, in exhaust portion, the spiral fluted number of turns is 1.75 ~ 4 circles.

Adopting the vacuum pump of this screw rod by the spiral fluted number of turns in increase exhaust portion and/or by improving the spiral fluted number of turns on compression transition part, realizing reduction ultimate vacuum.The compression transition length of this screw rod increases and/or the entire length of screw rod increases, and namely screw rod runs the growth of heating length, can reduce the temperature of screw rod and the operating temperature of vacuum pump inside, and then reduces screw rod temperature distortion amount.It can thus be appreciated that, adopt the vacuum pump of this screw rod can reduce screw rod machining accuracy and manufacture cost, the stability of vacuum pump can be ensured again.

In the screw rod of above-mentioned screw vacuum pump, it is 4 ~ 8 circles that described spiral fluted is wound around the number of turns.

In the screw rod of above-mentioned screw vacuum pump, on described compression transition part, spiral chute looping curve non-linear change tendencies meets following formula:

$f\left(t\right)={\mathrm{cpt}}_1+t_2[\mathrm{cp}(\frac{t}{t_2}-\frac{t_1}{t_2})-\frac{(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^3}{2}+\frac{(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^3(\frac{t}{t_2}-\frac{t_1}{t_2}-1)}{2}],t_1\≤t\≤t_1+t_2;$

Wherein: t ₁for the spiral fluted number of turns in suction unit; t ₂for the spiral fluted number of turns on compression transition part; p ₁for spiral fluted pitch on air input part; P is spiral fluted pitch in exhaust portion.

In the screw rod of above-mentioned screw vacuum pump, on described compression transition part, spiral chute pitch non-linear change tendencies meets following formula:

$f^{\′}\left(t\right)=\mathrm{cp}-\frac{3(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^2}{2}+\frac{3(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^2(\frac{t}{t_2}-\frac{t_1}{t_2}-1)}{2}+\frac{(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^3}{2},$ $t_1\≤t{\≤t}_1+t_2;$

Wherein: t ₁for the spiral fluted number of turns in suction unit; t ₂for the spiral fluted number of turns on compression transition part; p ₁for spiral fluted pitch on air input part; P is spiral fluted pitch in exhaust portion.

On compression transition part, spiral chute looping curve non-linear change tendencies also can adopt following proposal to replace with spiral chute pitch non-linear change tendencies on compression transition part: on described compression transition part, spiral chute looping curve non-linear change tendencies meets following formula:

$f\left(t\right)={\mathrm{cpt}}_1+\frac{c+1}{2}p(t-t_1)+\frac{t_2}{\mathrm{\π}}\frac{(c-1)p}{2}\sin (\frac{\mathrm{\π}}{t_2}t-\frac{\mathrm{\π}{t}_1}{t_2}),t_1\≤t\≤t_1+t_2;$

Wherein: t ₁for the spiral fluted number of turns in suction unit; t ₂for the spiral fluted number of turns on compression transition part; p ₁for spiral fluted pitch on air input part; P is spiral fluted pitch in exhaust portion.

In the screw rod of above-mentioned screw vacuum pump, on described compression transition part, spiral chute pitch non-linear change tendencies meets following formula:

$f^{\′}\left(t\right)=\frac{c+1}{2}p+\frac{(c-1)p}{2}\cos (\frac{\mathrm{\π}}{t_2}t-\frac{\mathrm{\π}{t}_1}{t_2}),t_1\≤t\≤t_1+t_2;$

Wherein: t ₁for the spiral fluted number of turns in suction unit; t ₂for the spiral fluted number of turns on compression transition part; p ₁for spiral fluted pitch on air input part; P is spiral fluted pitch in exhaust portion.

Compared with prior art, the screw rod of this screw vacuum pump makes vacuum pump ultimate vacuum higher, and performance is more stable, and manufacturing expense increases hardly, and then makes screw vacuum Type of pump more, and application is more extensive.

Adopt the screw vacuum pump of this varying pitch screw to be wound around the number of turns by suitably improving spiral fluted, and then optimize compressed capability, improve the exhaust efficiency of exhaust portion, slow down exhaust portion air and can not arrange and excessive compression phenomenon, and then effectively reduce specific energy consumption.

Accompanying drawing explanation

Fig. 1 is the structural representation of the screw rod of this screw vacuum pump.

Fig. 2 is the axial position of the screw rod of this screw vacuum pump and the relationship change schematic diagram being wound around the number of turns.

Fig. 3 is the pitch of the screw rod of this screw vacuum pump and the relationship change schematic diagram being wound around the number of turns.

In figure, 1, the body of rod; 2, spiral chute; 3, suction unit; 4, exhaust portion; 5, transition part is compressed.

Embodiment

Be below specific embodiment of the utility model and by reference to the accompanying drawings, the technical solution of the utility model is further described, but the utility model be not limited to these embodiments.

Embodiment one

As shown in Figure 1, the screw rod of this screw vacuum pump comprises the cylindrical body of rod 1, the outer side surface of the body of rod 1 has a spiral chute 2, the two-port of spiral chute 2 lays respectively in the both ends of the surface of the body of rod 1, one end of the body of rod 1 is suction unit 3, the other end is exhaust portion 4, for compress transition part 5 between suction unit 3 and exhaust portion 4; In suction unit 3, the pitch of spiral chute 2 is constant, and in exhaust portion 4, the pitch of spiral chute 2 is constant, and in exhaust portion 4, the pitch of spiral chute 2 is less than the pitch of spiral chute 2 in suction unit 3; On compression transition part 5, spiral chute 2 one end connects with spiral chute 2 in suction unit 3, and the other end connects with spiral chute 2 in suction unit 3, and on compression transition part 5, spiral chute 2 passes through, and pitch is non-linear gradual to be reduced.

The winding number of turns of spiral chute 2 is 4 circles, and the reduced overall of screw vacuum pump meets following formula than c: p ₁for the pitch of spiral chute on air input part 2; P is the pitch of spiral chute 2 in exhaust portion 4; 1.5≤c≤10.

In suction unit 3, the number of turns of spiral chute 2 is 0.75 circle; On compression transition part 5, the number of turns of spiral chute 2 is 1.25 circles, and in exhaust portion 4, the number of turns of spiral chute 2 is 2 circles.

The vacuum pump of this varying pitch screw is adopted to realize reducing ultimate vacuum by the number of turns improving spiral chute 2 on compression transition part 5; Make screw rod run heating length to increase simultaneously, reduce extruder temperature and vacuum pump internal operating temperature, and then reduce screw rod amount of deformation, thus both reduced screw rod machining accuracy and manufacture cost, the stability of vacuum pump can be ensured again.

As shown in Figure 2, the w in Fig. 2 represents the length of screw rod, and t represents the winding number of turns of spiral chute 2.On compression transition part 5, spiral chute 2 looping curve non-linear change tendencies meets following formula:

$f\left(t\right)=0.75\mathrm{cp}+1.25\×[\mathrm{cp}(\frac{t}{1.25}-0.6)-\frac{(c-1)p{(\frac{t}{1.25}-0.6)}^3}{2}+\frac{(c-1)p{(\frac{t}{1.25}-0.6)}^3(\frac{t}{1.25}-0.6)}{2}]$ $,0.75\≤t\≤2.$

In suction unit 3, in spiral chute 2 looping curve and exhaust portion 4, spiral chute 2 looping curve is linear change.

As shown in Figure 3, compress spiral chute 2 pitch non-linear change tendencies on transition part 5 and meet following formula:

$f^{\′}\left(t\right)=\mathrm{cp}-\frac{3(c-1)p{(\frac{t}{1.25}-0.6)}^2}{2}+\frac{3(c-1)p{(\frac{t}{1.25}-0.6)}^2(\frac{t}{1.25}-1.6)}{2}+\frac{(c-1)p{(\frac{t}{1.25}-0.6)}^3}{2},$ $0.75\≤t\≤2;$ W ' in Fig. 3 represents the pitch of spiral chute 2, and t represents the winding number of turns of spiral chute 2.

In suction unit 3, in the pitch of spiral chute 2 and exhaust portion 4, the pitch of spiral chute 2 is uniform pitch.

Embodiment two

The present embodiment with the structure of embodiment one and principle substantially identical, different place is: the winding number of turns of spiral chute 2 is 4 circles, and in suction unit 3, the number of turns of spiral chute 2 is 1 circle; On compression transition part 5, the number of turns of spiral chute 2 is 1.25 circles, and in exhaust portion 4, the number of turns of spiral chute 2 is 1.75 circles.

The vacuum pump of this varying pitch screw is adopted to realize reducing ultimate vacuum by the number of turns improving spiral chute 2 on compression transition part 5; Make screw rod run heating length to increase simultaneously, reduce extruder temperature and vacuum pump internal operating temperature, and then reduce screw rod amount of deformation, thus both reduced screw rod machining accuracy and manufacture cost, the stability of vacuum pump can be ensured again.

On compression transition part 5, spiral chute 2 looping curve non-linear change tendencies meets following formula:

$f\left(t\right)=\mathrm{cp}+1.25\×[\mathrm{cp}(\frac{t}{1.25}-0.8)-\frac{(c-1)p{(\frac{t}{1.25}-0.8)}^3}{2}+\frac{(c-1)p{(\frac{t}{1.25}-0.8)}^3(\frac{t}{1.25}-0.8)}{2}],$ $1\≤t\≤2.25.$

On compression transition part 5, spiral chute 2 pitch non-linear change tendencies meets following formula:

$f^{\′}\left(t\right)=\mathrm{cp}-\frac{3(c-1)p{(\frac{t}{1.25}-0.8)}^2}{2}+\frac{3(c-1)p{(\frac{t}{1.25}-0.8)}^2(\frac{t}{1.25}-1.8)}{2}+\frac{(c-1)p{(\frac{t}{1.25}-0.8)}^3}{2},$ $1\≤t\≤2.25.$

Embodiment three

The present embodiment with the structure of embodiment one and principle substantially identical, different place is: the winding number of turns of spiral chute 2 is 5.5 circles, and in suction unit 3, the number of turns of spiral chute 2 is 1 circle; On compression transition part 5, the number of turns of spiral chute 2 is 1 circle, and in exhaust portion 4, the number of turns of spiral chute 2 is 3.5 circles.

The vacuum pump of this varying pitch screw is adopted to realize reducing ultimate vacuum by the number of turns increasing spiral chute 2 in exhaust portion 4; Make screw rod run heating length to increase simultaneously, reduce extruder temperature and vacuum pump internal operating temperature, and then reduce screw rod amount of deformation, thus both reduced screw rod machining accuracy and manufacture cost, the stability of vacuum pump can be ensured again.

On compression transition part 5, spiral chute 2 looping curve non-linear change tendencies meets following formula:

$f\left(t\right)=\mathrm{cp}+[\mathrm{cp}(t-1)-\frac{(c-1)p{(t-1)}^3}{2}+\frac{(c-1)p{(t-1)}^3(t-2)}{2}],1\≤t\≤2.$

On compression transition part 5, spiral chute 2 pitch non-linear change tendencies meets following formula:

$f^{\′}\left(t\right)=\mathrm{cp}-\frac{3(c-1)p{(t-1)}^2}{2}+\frac{3(c-1)p{(t-1)}^2(t-2)}{2}+\frac{(c-1)p{(t-1)}^3}{2},1\≤t\≤2.$

Embodiment four

The present embodiment with the structure of embodiment one and principle substantially identical, different place is: the winding number of turns of spiral chute 2 is 5.5 circles, and in suction unit 3, the number of turns of spiral chute 2 is 1 circle; On compression transition part 5, the number of turns of spiral chute 2 is 2 circles, and in exhaust portion 4, the number of turns of spiral chute 2 is 2.5 circles.

Adopt the vacuum pump of this varying pitch screw by improving the number of turns of spiral chute 2 on compression transition part 5 and realizing reducing ultimate vacuum by the number of turns increasing spiral chute 2 in exhaust portion 4; Make screw rod run heating length to increase simultaneously, reduce extruder temperature and vacuum pump internal operating temperature, and then reduce screw rod amount of deformation, thus both reduced screw rod machining accuracy and manufacture cost, the stability of vacuum pump can be ensured again.

On compression transition part 5, spiral chute 2 looping curve non-linear change tendencies meets following formula:

$f\left(t\right)=\mathrm{cp}+2\×[\mathrm{cp}(\frac{t}{2}-0.5)-\frac{(c-1)p{(\frac{t}{2}-0.5)}^3}{2}+\frac{(c-1)p{(\frac{t}{2}-0.5)}^3(\frac{t}{2}-1.5)}{2}],1\≤t\≤3;$

On compression transition part 5, spiral chute 2 pitch non-linear change tendencies meets following formula:

$f^{\′}\left(t\right)=\mathrm{cp}-\frac{3(c-1)p{(\frac{t}{2}-0.5)}^2}{2}+\frac{3(c-1)p{(\frac{t}{2}-0.5)}^2(\frac{t}{2}-1.5)}{2}+\frac{(c-1)p{(\frac{t}{2}-0.5)}^3}{2},1\≤t\≤3.$

Embodiment five

The present embodiment with the structure of embodiment one and principle substantially identical, different place is: the winding number of turns of spiral chute 2 is 8 circles, and in suction unit 3, the number of turns of spiral chute 2 is 1.25 circles; On compression transition part 5, the number of turns of spiral chute 2 is 3 circles, and in exhaust portion 4, the number of turns of spiral chute 2 is 3.75 circles.

Adopt the vacuum pump of this varying pitch screw by improving the number of turns of spiral chute 2 on compression transition part 5 and realizing reducing ultimate vacuum by the number of turns increasing spiral chute 2 in exhaust portion 4; Make screw rod run heating length to increase simultaneously, reduce extruder temperature and vacuum pump internal operating temperature, and then reduce screw rod amount of deformation, thus both reduced screw rod machining accuracy and manufacture cost, the stability of vacuum pump can be ensured again.

On compression transition part 5, spiral chute 2 looping curve non-linear change tendencies meets following formula:

$f\left(t\right)=1.25\mathrm{cp}+3\×[\mathrm{cp}(\frac{t}{3}-\frac{1.25}{3})-\frac{(c-1)p{(\frac{t}{3}-\frac{1.25}{3})}^3}{2}+\frac{(c-1)p{(\frac{t}{3}-\frac{1.25}{3})}^3(\frac{t}{3}-\frac{1.25}{3}-1)}{2}],$ $1.25\≤t\≤4.25.$

On compression transition part 5, spiral chute 2 pitch non-linear change tendencies meets following formula:

$f^{\′}\left(t\right)=\mathrm{cp}-\frac{3(c-1)p{(\frac{t}{3}-\frac{1.25}{3})}^2}{2}+\frac{3(c-1)p{(\frac{t}{3}-\frac{1.25}{3})}^2(\frac{t}{3}-\frac{1.25}{3}-1)}{2}+\frac{(c-1)p{(\frac{t}{3}-\frac{1.25}{3})}^3}{2},$ $1.25\≤t\≤4.25.$

Embodiment six

The present embodiment with the structure of embodiment one and principle substantially identical, different place is: on compression transition part 5, spiral chute 2 looping curve non-linear change tendencies meets following formula: $f\left(t\right)=0.75\mathrm{cp}+\frac{c+1}{2}p(t-0.75)+\frac{1.25}{\mathrm{\π}}\frac{(c-1)p}{2}\sin (\frac{\mathrm{\π}}{1.25}t-\frac{0.75\mathrm{\π}}{1.25}),0.75\≤t\≤2;$

On compression transition part 5, spiral chute 2 pitch non-linear change tendencies meets following formula:

$f^{\′}\left(t\right)=\frac{c+1}{2}p+\frac{(c-1)p}{2}\cos (\frac{\mathrm{\π}}{1.25}t-\frac{0.75\mathrm{\π}}{1.25}),0.75\≤t\≤2.$

Claims (6)

1. the screw rod of a screw vacuum pump, comprise the cylindrical body of rod (1), the outer side surface of the body of rod (1) has a spiral chute (2), the two-port of spiral chute (2) lays respectively in the both ends of the surface of the body of rod (1); One end of the body of rod (1) is suction unit (3), and the other end is exhaust portion (4), for compress transition part (5) between suction unit (3) and exhaust portion (4); The pitch of the upper spiral chute (2) of suction unit (3) is constant, the pitch of the upper spiral chute (2) of exhaust portion (4) is constant, and the pitch of the upper spiral chute (2) of exhaust portion (4) is less than the pitch of the upper spiral chute (2) of suction unit (3); Upper spiral chute (2) one end of compression transition part (5) connects with the upper spiral chute (2) of suction unit (3), the other end connects with the upper spiral chute (2) of suction unit (3), and the upper spiral chute (2) of compression transition part (5) passes through, and pitch is non-linear gradual to be reduced; It is characterized in that, the number of turns of the upper spiral chute (2) of suction unit (3) is 0.75 ~ 1.25 circle; When the number of turns compressing the upper spiral chute (2) of transition part (5) is 1 circle, the number of turns of the upper spiral chute (2) of exhaust portion (4) is greater than 3 circles; When the number of turns compressing the upper spiral chute (2) of transition part (5) is greater than 1 circle, the number of turns of the upper spiral chute (2) of exhaust portion (4) is 1.75 ~ 4 circles.

2. the screw rod of screw vacuum pump according to claim 1, is characterized in that, the winding number of turns of described spiral chute (2) is 4 ~ 8 circles.

3. the screw rod of screw vacuum pump according to claim 1, is characterized in that, upper spiral chute (2) the looping curve non-linear change tendencies of described compression transition part (5) meets following formula:

$f\left(t\right)={\mathrm{cpt}}_1+t_2[\mathrm{cp}(\frac{t}{t_2}-\frac{t_1}{t_2})-\frac{(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^3}{2}+\frac{(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^3(\frac{t}{t_2}-\frac{t_1}{t_2}-1)}{2}],$ t ₁≤t≤t ₁+t ₂；

Wherein: t ₁for the number of turns of the upper spiral chute (2) of suction unit (3); t ₂for the number of turns of the upper spiral chute (2) of compression transition part (5); p ₁for the pitch of spiral chute on air input part (2); P is the pitch of the upper spiral chute (2) of exhaust portion (4).

4. the screw rod of screw vacuum pump according to claim 3, is characterized in that, upper spiral chute (2) the pitch non-linear change tendencies of described compression transition part (5) meets following formula:

$f^{\′}\left(t\right)=\mathrm{cp}-\frac{3(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^2}{2}+\frac{3(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^2(\frac{t}{t_2}-\frac{t_1}{t_2}-1)}{2}+\frac{(c-1)p{(\frac{t}{t_2}-\frac{t_1}{t_2})}^3}{2},$ t ₁≤t≤t ₁+t ₂；

Wherein: t ₁for the number of turns of the upper spiral chute (2) of suction unit (3); t ₂for the number of turns of the upper spiral chute (2) of compression transition part (5); p ₁for the pitch of spiral chute on air input part (2); P is the pitch of the upper spiral chute (2) of exhaust portion (4).

5. the screw rod of screw vacuum pump according to claim 1, is characterized in that, upper spiral chute (2) the looping curve non-linear change tendencies of described compression transition part (5) meets following formula:

$f\left(t\right)={\mathrm{cpt}}_1+\frac{c+1}{2}p(t-t_1)+\frac{t_2}{\mathrm{\π}}\frac{(c-1)p}{2}\sin (\frac{\mathrm{\π}}{t_2}t-\frac{\mathrm{\π}{t}_1}{t_2}),$ t ₁≤t≤t ₁+t ₂；

Wherein: t ₁for the number of turns of the upper spiral chute (2) of suction unit (3); t ₂for the number of turns of the upper spiral chute (2) of compression transition part (5); p ₁for the pitch of spiral chute on air input part (2); P is the pitch of the upper spiral chute (2) of exhaust portion (4).

6. the screw rod of screw vacuum pump according to claim 5, is characterized in that, upper spiral chute (2) the pitch non-linear change tendencies of described compression transition part (5) meets following formula:

$f^{\′}\left(t\right)=\frac{c+1}{2}p+\frac{(c-1)p}{2}\cos (\frac{\mathrm{\π}}{t_2}t-\frac{\mathrm{\π}{t}_1}{t_2}),$ t ₁≤t≤t ₁+t ₂；

Wherein: t ₁for the number of turns of the upper spiral chute (2) of suction unit (3); t ₂for the number of turns of the upper spiral chute (2) of compression transition part (5); p ₁for the pitch of spiral chute on air input part (2); P is the pitch of the upper spiral chute (2) of exhaust portion (4).