Screw Compressor Having Slide Valve With Flexible Volume Ratio

Abstract

A screw compressor includes a casing, a screw, an air entry, an air outlet, a slide valve with a flexible volume ratio, and first and second air cylinders. The slide valve is disposed between the first and second air cylinders and includes a slide valve main body. Two ends of the slide valve seal the first and second air cylinders. The first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and the second air cylinder is connected to a last closed spiral flute through a second connection pipe. The slide valve searches for balance under the driving of pressures in the first and second air cylinders. The screw compressor having a slide valve with a flexible volume ratio can enable the volume ratio of the compressor to be automatically adjusted to an optimal state.

What is claimed is: 
     
         1 . A screw compressor having a slide valve with a flexible volume ratio, wherein the screw compressor comprises a casing, a screw, an air entry, an air outlet, a slide valve, a first air cylinder and a second air cylinder;
 the slide valve is disposed between the first air cylinder and the second air cylinder;   the slide valve comprises a slide valve main body, and two ends of the slide valve main body are respectively a first end surface and a second end surface; sectional areas of the first end surface, the second end surface and the slide valve main body are the same, and the first end surface and the second end surface seal the first air cylinder and the second air cylinder respectively;   the first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and in the first air cylinder, a pressure generated by the first end surface corresponds to an exhaust pressure; the second air cylinder is connected to a last closed spiral flute through a second connection pipe, and in the second air cylinder, a pressure generated by the second end surface corresponds to a pressure at a compression end of the compressor, that is, an average pressure in the last closed spiral flute before the compressor exhausts;   the slide valve searches for balance under the driving of pressures in the first air cylinder and the second air cylinder, so as to achieve an optimal volume ratio of the compressor;   if the pressure generated by the first end surface is greater than that generated by the second end surface, that is, the exhaust pressure is greater than the pressure at the compression end of the compressor, the slide valve moves towards the second air cylinder, so as to increase the pressure at the compression end of the compressor;   if the pressure generated by the first end surface is less than that generated by the second end surface, that is, the exhaust pressure is less than the pressure at the compression end of the compressor, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor; and   an elastic mechanism is disposed in the second air cylinder, wherein one end of the elastic mechanism is connected to the second air cylinder, and the other end is connected to the second end surface; the elastic mechanism ensures unloading and starting of the compressor.   
     
     
         2 . A screw compressor having a slide valve with a flexible volume ratio, wherein the screw compressor comprises a casing, a screw, an air entry, an air outlet, a slide valve, a first air cylinder and a second air cylinder;
 the slide valve is disposed between the first air cylinder and the second air cylinder;   the slide valve comprises a slide valve main body, and two ends of the slide valve main body are respectively a first end surface and a second end surface; the first end surface and the second end surface respectively seal the first air cylinder and the second air cylinder;   the first air cylinder is connected to the air outlet of the compressor through a first connection pipe, and the second air cylinder is connected to a last closed spiral flute through a second connection pipe; and   the slide valve searches for balance under the driving of pressures in the first air cylinder and the second air cylinder.   
     
     
         3 . The screw compressor having a slide valve with a flexible volume ratio as in  claim 2 , wherein,
 sectional areas of the first end surface, the second end surface and the slide valve main body are the same, or not the same, or different from one another.   
     
     
         4 . The screw compressor having a slide valve with a flexible volume ratio as in  claim 2 , wherein,
 the first air cylinder is connected to the air outlet of the compressor through the first connection pipe, and in the first air cylinder, a pressure generated by the first end surface is in direct proportion to an exhaust pressure; and   the second air cylinder is connected to the last closed spiral flute through the second connection pipe, and in the second air cylinder, a pressure generated by the second end surface is in direct proportion to a pressure at a compression end of the compressor, that is, in direct proportion to an average pressure in the last closed spiral flute before the compressor exhausts.   
     
     
         5 . The screw compressor having a slide valve with a flexible volume ratio as in  claim 2 , wherein,
 if a pressure generated by the first end surface is greater than that generated by the second end surface, the slide valve moves towards the second air cylinder, so as to increase a pressure at a compression end of the compressor; and   if the pressure generated by the first end surface is less than that generated by the second end surface, the slide valve moves towards the first air cylinder, so as to decrease the pressure at the compression end of the compressor.   
     
     
         6 . The screw compressor having a slide valve with a flexible volume ratio as in  claim 2 , wherein,
 an elastic mechanism is disposed in the second air cylinder, one end of the elastic mechanism is connected to the second air cylinder, and the other end is connected to the second end surface; the elastic mechanism ensures unloading and starting of the compressor.   
     
     
         7 . The screw compressor having a slide valve with a flexible volume ratio as in  claim 2 , wherein,
 the slide valve is disposed on one side of the screw.   
     
     
         8 . The screw compressor having a slide valve with a flexible volume ratio as in  claim 2 , wherein,
 the screw compressor is a twin-screw compressor or a tri-rotor screw compressor.