JPS61169688A - Screw fluid machinery - Google Patents

Abstract

PURPOSE:To prevent the thermal deformation of a casing accompanied by the temperature rise of the discharged gas and permit the operation with the high discharge pressure having a high-temperature, by forming a cooling-water flow passage on the outer periphery of the discharge passage of the oil free screw fluid machinery. CONSTITUTION:A vacant chamber 15 for the flow of cooling water is formed in a casing 1, and the cooling water is allowed to flow into an effluence port 15b from in an inflow port 15a. In this case, an annular flow passage 21 for the cooling water is formed by a partitioning wall 20 on the outer periphery of a discharged-gas passage 14. The cooling water is allowed to flow in the casing 1 through an annular passage 21 from the inflow port 15a, and the cooling effect in the vicinity of the outer periphery of the discharged-gas passage 14 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a screw fluid machine in which a water cooling jacket is formed in a casing surrounding a screw rotor.

[Background of the invention]

In devices operated at high temperatures, such as oil-free screw fluid machines, a water cooling jacket is formed in the casing surrounding a pair of male and female screw rotors to prevent thermal deformation of the casing due to heat generation.

In a screw fluid machine, a pair of male and female screw rotors are housed inside a casing, and a suction passage is formed on one side of the casing and a discharge passage is formed on the other side.

By rotating the male rotor, the female rotor is driven to rotate via a timing gear, etc., and working gas is introduced from the suction passage into the toothed space formed by the single rotor, and the sealed gas is compressed to a predetermined pressure by the screw rotor. Then, it is discharged outside the machine from the discharge passage and used for the desired purpose.

However, since the so-called oil-free screw fluid machine, in which oil is not injected into the screw rotor, is operated at high temperatures, the casing may be thermally deformed due to heat generation. As a countermeasure to the above, a structure is known in which a water cooling jacket is provided on the outer circumference of the rotor to reduce the heat generation of the recasing using cooling water, as disclosed in US Pat. No. 2,410,172.

Therefore, as for the temperature distribution of the screw casing of the screw compressor, due to the temperature increase of the compressed discharge gas, the temperature is highest near the discharge passage, and the temperature decreases as the distance from the discharge passage increases.

However, in conventional devices, no consideration has been given to actively cooling the vicinity of the discharge passage; rather, the shape of the cooling water stagnates near the discharge passage, and furthermore, the cross-sectional area of the passage of the cooling water is too small. The vicinity of the discharge passage is formed wide,
The structure is such that the flow velocity of the cooling water slows down near the discharge passage, reducing heat transfer of the cooling water.

As mentioned above, the casing near the gas discharge passage is not sufficiently cooled, and the screw casing cylinder near the discharge passage may be affected by the temperature rise of the discharge gas, especially in screw compressors where the gas discharge pressure is high and the heat generated by compression is large. The screw compressor may become deformed and come into contact with the rotating male and female rotors, making it impossible for the screw compressor to continue operating.
There was a problem in that the discharge pressure could not be set too high.

[Purpose of the invention]

The present invention was invented in view of the above problems, and prevents thermal deformation of the casing due to the temperature rise of the discharge gas of a screw fluid machine, eliminates contact between the screw rotor and the casing, and prevents the discharge gas from becoming hot. The object of the present invention is to provide a screw fluid machine that can be operated even at a high discharge pressure.

[Summary of the invention]

Cooling of the casing by the water cooling jacket is mainly performed by heat transfer between the high temperature casing and low temperature cooling water, and in the case of turbulent heat transfer, the heat transfer coefficient α is expressed by the following equations.

Nu=0.023XRe'・8XPr"'-
42) Xd Re=□...
(3) v"Q/d"
-(4) where Nu is the Nusselt number, λ is the thermal conductivity of the casing, d is the equivalent diameter of the cooling water passage, and Re
is the Reynolds number of the cooling water, vtQ is the flow rate and flow rate of the cooling water, and Pr, y are the Prandtl number and kinematic viscosity coefficient.

In equations (1), (2), (3), and (4), if the physical property values of Q and λl P r t γ are constant, in order to increase the heat transfer coefficient α, the equivalent diameter d of the cooling water passage must be reduced. You'll know what to do.

In order to achieve the intended purpose, the present invention forms a void space in the water cooling jacket also on the outer periphery of the discharge passage, and surrounds the outer periphery of the discharge passage with a partition wall with an appropriate space. It has the feature of forming a cooling water flow path along with the screw fluid machine, increasing the cooling capacity of the water cooling jacket near the gas discharge passage where the temperature is highest due to the heat generated by the screw fluid machine, and preventing thermal deformation of the casing due to heat generation. It is.

[Embodiments of the invention]

An embodiment of the present invention will be described below based on the drawings.

The figures show an oil-free screw compressor; FIG. 1 is a longitudinal cross-sectional view, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line ■-■.

The casing includes a screw casing 1, a suction casing 2 disposed on its driving side end face, and an end casing 3 attached to the other side. A male rotor 4 degrees and a female rotor 5 are meshed with each other in the screw casing 1 and housed in the screw casing 1 with a small gap therebetween. The rotors 4 and 5 have a stepped rotor shaft 4a.
, 4b.

5a and 5b are arranged in series, and the shaft is supported by a roller bearing 6, and is further supported by a ball bearing 7 to restrain movement in the axial direction. Also, the rotor shafts 4a, 4b, 5a.

A sealing member 8 is fitted between the large diameter portion of 5b and the casing to prevent compressed gas from leaking within the casing 1 and to prevent oil supply from the bearings 6 and 7 from entering the screw casing 1. prevent.

The male rotor 4 is a drive side rotor, and a pinion 9 is attached to the tip of the rotor shaft 4a, and this pinion meshes with a gear 10 connected to an electric motor (not shown) to transmit power. The rotor shaft 4b on the other side.

Timing gears 11 and 12 that connect the WI rotor are attached to the shaft end of the rotor 5b, and both rotors 4 and 5 rotate synchronously in a non-contact manner while maintaining a small gap.

A suction passage 13 is formed on one side of the screw casing 1, and a discharge passage 14 is formed on the other side. The suction passage 13 is connected to a suction chamber 13a formed in the end of the casing 1 and the suction casing 2, and communicates with a suction space formed by the teeth of the screw rotors 4 and 5 via the chamber 13a.

In addition, the screw casing 1 includes a screw rotor 4,
A cavity 15 for a water cooling jacket is formed surrounding the casing 5 and further extending to the end casing 3 side. This vacant room 1
5 is isolated from the suction chamber 13a via a partition wall 16, and has an inlet 15a on one side of the screw casing 1 and an outlet 1 on the other side.
5b is provided. As shown in a developed view in FIG. 4, an annular partition wall 20 with one side cut out is provided in the cavity 15 on the outer periphery of the discharge passage 14, and surrounds the outer periphery of the discharge passage 14 and connects the inlet. 15a and through the inflow hole 19,
An annular flow passage 21 having a small cross-sectional area is formed, with 9 serving as an inlet and the cutout 20b serving as an outlet.

The operation of the screw compressor having the above structure will be explained below. The power of the electric motor is transmitted to the male screw rotor 4 through gears 10 and 9, and the rotor 4 rotates, and the female screw rotor 5 is transmitted through timing gears 11 and 12 to a single screw that rotates in a non-contact manner. The rotation of the rotors 4 and 5 causes the working gas to flow from the suction passage 13 through the suction chamber 13a.

The compressed gas is sucked into the tooth-shaped space of the screw rotor and discharged from the discharge passage 14 to the outside of the machine.

The compression process will be explained using FIG. 5. First, the volume of the compression chamber changes from v0 to vl due to the engagement of the rotors. At this time, the pressure increases from the suction pressure P, to Pi, and the temperature of the working gas also increases with the compression. The changes up to this point show the changes from the suction port to the discharge port, where - is the design pressure ratio P.

P.

cormorant. The temperature rise of gas due to compression is P when the negative value is large.

It becomes very large. After the discharge port, the pressure increases once due to the pressure drop during discharge, but as the volume decreases, the pressure decreases and becomes the discharge pressure P4 at the point of zero volume. In this manner, the P-■ change shown in FIG. 5 is continuously performed by the engagement of the rotors.

Due to the compression action, the temperature of the working gas increases and this heat is transferred to the casing. To prevent the temperature of the casing from rising, cooling water is poured into the water cooling jacket to cool the casing.
The cooling water flows in from the inlet 15a, passes through the inlet hole 19, flows through the annular flow passage 21 around the discharge passage 14, and then flows through the space 15 as shown by arrows in FIGS. 1 and 4, It flows out of the machine from the outlet 15b.

Therefore, in the above-mentioned circulation of the cooling water, the cold water first flows near the discharge passage 14 where the temperature becomes high, and this portion is actively cooled with low-temperature water. In addition, since the passage around the discharge passage 14 is formed with an annular passage 21 having a small cross-sectional area on the outer periphery of the passage 14, the cooling water flowing through the road 21 flows at an increased flow rate, so that the cooling capacity of the passage 14 is increased. is enhanced.

The cooling efficiency of the casing portion near the discharge passage 14 is improved by both of the above.

〔Effect of the invention〕

As explained above, according to the present invention, the casing is actively cooled near the discharge passage where the temperature is high, and the cooling efficiency is improved. Deformation can be prevented, and contact between the rotor and the casing can be prevented.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a screw compressor showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the nn arrow in Fig. 1, and Fig. 3 is a sectional view taken along the ■-■ arrow in Fig. 1. Figure 4 is IV-I of Figure 3.
V arrow cross-sectional developed view, Figure 5 is P-v of the screw compressor
It is a line diagram. DESCRIPTION OF SYMBOLS 1...Screw casing, 4...Male screw rotor, 5...Female screw rotor, 13...Suction passage 9.14...Discharge passage, 15...Vacancy (water cooling jacket) ), 30th

Claims (1)

[Claims] 1. A pair of male and female screw rotors are housed inside a casing in mesh with each other, a suction passage is formed on one side of the casing, a discharge passage is formed on the other side, and a water cooling system surrounds the screw rotor within the casing. In a screw fluid machine in which a jacket has a cavity inside, the cavity is also formed at the outer periphery of the discharge passage, and the outer periphery of the discharge passage is surrounded by a partition wall with an appropriate space, and the outer periphery of the discharge passage is surrounded by a partition wall. A screw fluid machine characterized by forming an annular cooling water flow path. 2. The screw fluid machine according to claim 1, wherein the cooling water flow path is connected to the empty chamber flow path via a flow path along the outer periphery of the discharge passage.