Single Screw Compressor
The single screw compressor addresses leakage issues in VVR slides by using a two-stage slide configuration with notch alignment, improving efficiency and VR control without compromising manufacturing complexity.
Patent Information
- Application Number
- JP2021549429
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2019-02-22
- Filing Date
- 2020-02-20
- Publication Date
- 2025-11-28
- Estimated Expiration
- 2040-02-20
AI Technical Summary
Conventional screw compressors with variable volume ratio (VVR) slides suffer from leakage paths that reduce efficiency due to the need for clearance at the slide bore, which allows discharge to suction leakage and intermediate pressure leakage, regardless of the slide's position.
A single screw compressor design with a two-stage configuration and a slide that includes a notch between sealing portions, allowing precise alignment of discharge ports for high VR and a constant path for low VR, minimizing leakage by eliminating unnecessary clearance.
The design achieves efficiency comparable to a fully modulated VVR slide by reducing leakage, enhancing performance and manufacturing ease while maintaining precise VR control.
Smart Images
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a single screw compressor with a variable volume ratio (VR). [Background technology]
[0002] Screw compressors have traditionally used slides to control the compressor capacity and / or volume ratio of the compression process.
[0003] A capacity control slide, such as that shown in Figure 1, conventionally operates in an axial plane along the rotor. The suction end of the slide delays the start of compression by opening a bypass port during the initial rotation of the main rotor, thereby effectively reducing the compressor's displacement (capacity). At the same time, the discharge port is delayed from opening, maintaining a nearly constant VR throughout most of the compression stroke.
[0004] Currently, variable frequency drives are commonly used to control the capacity of screw compressors, however slides are retained to provide the variable volume ratio capability.
[0005] As operating conditions change, the required built-in volume ratio must be changed to accommodate those changing conditions if optimal efficiency is to be achieved. An example of a variable volume ratio slide is shown in Figure 2. It can be considered a modification of a traditional capacity-controlled slide. This is achieved by extending the suction end of the slide so that none of the bypass ports for suction are open during the slide's full axial travel. The slide's VR ports are then designed to provide a varying volume ratio as the rotor grooves open through the slide's VR ports toward the discharge ports.
[0006] Conventional VVR slides have the disadvantage that the slide must extend from the discharge port to the end of the rotor. Therefore, even when the slide is in its highest VR position (moving toward the rotor's discharge end), the suction end of the rotor is sealed and suction bypass is not possible. For the slide to move freely, clearance must be present at the slide bore. This clearance provides a direct leakage path from discharge to suction and, to a lesser extent, allows intermediate pressure sealed by the slide to leak into suction. This leakage occurs regardless of the slide's position, resulting in an undesirable reduction in compressor efficiency. Figure 3 shows a schematic of the slide in place within the compressor, and Figure 4 illustrates the slide's leakage path 1. Summary of the Invention
[0007] The purpose of the present invention is to improve base efficiency by eliminating leakage paths from discharge to suction.
[0008] The present invention employs a simple two-stage configuration, and the reduced leakage effect allows it to rival the efficiency of a precise, fully modulated variable VR slide.
[0009] The present invention provides a single screw compressor comprising: a main rotor and at least one gate rotor; a casing for the main rotor, the casing having a discharge port at a discharge end of the casing; and a slide slidable within a bore in the casing adjacent the main rotor; The slide has a notch between the first and second sealing portions of the slide, and the slide is slidable between a high volume ratio position in which the notch is within the casing to provide a path to the discharge port and a low volume ratio position in which the slide is beyond the discharge end of the casing to provide a constant discharge path to the bore of the casing.
[0010] In one embodiment, the first or upstream sealing portion of the rotor has a surface facing outward from the notch that lies substantially in a plane perpendicular to the axes of the slide and main rotor, for ease of manufacturing.
[0011] In an alternative embodiment, the rotor first sealing portion has a surface facing outward from the notch that is inclined relative to a plane perpendicular to the axis of the slide and main rotor at an angle substantially equal to the pitch angle of the main rotor, thereby providing precise VR control. [Brief explanation of the drawings]
[0012] The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:
[0013] [Figure 1] FIG. 1 shows the known volume control slide mentioned above.
[0014] [Figure 2] FIG. 2 shows the known VR controlled slide mentioned above.
[0015] [Figure 3] FIG. 3 shows a known VR control slide and its leakage path. [Figure 4] FIG. 4 shows a known VR control slide and its leakage path.
[0016] [Figure 5] FIG. 5 shows a slide according to an embodiment of the present invention.
[0017] [Figure 6] FIG. 6 shows the slide of FIG. 5 in position on a compressor. [Figure 7] FIG. 7 shows the slide of FIG. 5 in a different position on the compressor.
[0018] [Figure 8] FIG. 8 shows a slide according to an alternative embodiment.
[0019] [Figure 9] FIG. 9 shows the slide of FIG. 5 in position on a compressor. [Figure 10] FIG. 10 shows the slide of FIG. 5 in a different position on the compressor. DETAILED DESCRIPTION OF THE INVENTION
[0020] FIG. 5 shows a slide according to the invention, with a seal 2, a seal 4 and a notch 6.
[0021] Figure 6 shows the slide of Figure 5 positioned towards the main casing, along with the main rotor. Cutout 6 provides a precise high VR discharge port.
[0022] Figure 7 shows how low VR is achieved: the slide is withdrawn from the casing beyond the main rotor so that VR comes from ports 8 which remain in the casing.
[0023] The slide of Figures 5-7 is a simple slide. The high VR slide discharge port provided by the notch 6 is precisely aligned with the rotor groove, but when the slide is withdrawn beyond the rotor, the low VR constant port that is left behind does not meet the precise VR requirements.
[0024] Figures 8-10 show an alternative slide with a high VR cutout similar to the slide of Figures 5-7, but this slide also has a correct low VR that remains in the casing when removed over the rotor, as shown in Figure 10.
[0025] The simple slides of Figures 5-7 are easier to manufacture and compromise VR less in low VR operating conditions than in high VR conditions, while the precise VR slides of Figures 8-10 provide the highest efficiency.
Claims
[Claim 1] a main rotor and at least one gate rotor; a casing for the main rotor, the casing having a discharge port at a discharge end of the casing; a slide slidable within a bore in the casing adjacent the main rotor; It is equipped with In a single screw compressor, the slide has a notch (6) between the first sealing portion (2) and the second sealing portion (4) of the slide, the slide is slidable between a high volume ratio position where the notch (6) is in the casing to provide a path to the discharge port, and a low volume ratio position where the slide is beyond the discharge end of the casing to provide a fixed discharge path to the bore of the casing; When the slide moves from the high volume ratio position to the low volume ratio position, the first sealing portion of the slide moves toward the discharge end, a first or upstream sealing portion (2) of the slide having a first surface facing outward from the notch; an end of the hole is disposed closer to the discharge end of the casing than the suction end of the casing, and at the high volume ratio position, the first surface is disposed adjacent to the end of the hole so as to face the end of the hole, and is disposed closer to the discharge end of the casing than the suction end of the casing; In the low volume ratio position, the entire slide is positioned out of correspondence with the screw of the main rotor; the first surface is inclined at an angle substantially equal to the pitch angle of the main rotor relative to a plane perpendicular to the axes of the slide and the main rotor; Single screw compressor.
Citation Information
Patent Citations
Screw compressor and refrigeration cycle device
WO2017149659A1
Refrigeration cycle device
WO2017203608A1