Screw compressor and refrigeration cycle device
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Solution Overview
Problem
Screw compressors with economizer ports face performance deterioration during low-load operations due to increased leak-to-discharge ratios and dead volume issues, leading to unstable refrigeration cycles and reduced coefficients of performance.
Innovation Solution
A screw compressor design with an electric motor for variable rotation speed, featuring a bypass device and economizer port on one compression chamber, allowing for no-load operation during low-load conditions to reduce dead volume and enhance performance across a wide operation range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the screw compressor operates at low rotation speed during low-load conditions, then the capacity is reduced to match demand, but the ratio of leak to discharge amount increases and performance deteriorates
Solution Approach 1:
The compressor is divided into two independent compression chambers, each capable of independent operation. During low-load conditions, one chamber is deactivated while the other continues to operate, allowing the system to maintain optimal operating characteristics at reduced capacity without suffering from increased leak ratios that would occur if the entire system operated at low speed
Solution Approach 2:
The system dynamically switches between different operational modes: full-load operation with both chambers active, and low-load operation with one chamber deactivated. This dynamic reconfiguration allows the active chamber to always operate at optimal speed and pressure differentials, preventing the performance deterioration that would occur with continuous low-speed operation
2Adaptability or versatility
If the economizer port is provided in the compression chamber where the bypass port is not opened, then the economizer operation can be implemented, but under low-load conditions the economizer gas less easily flows in, the cycle becomes unstable, and the coefficient of performance is deteriorated
Solution Approach 1:
The economizer port is specifically positioned in the first compression chamber, which is equipped with both bypass and economizer ports. This localized configuration allows the economizer to function effectively when needed while the second chamber remains dedicated to standard compression operations, ensuring stable refrigeration cycle performance across varying load conditions
3Device complexity
If the economizer port is provided only in one compression chamber, then the structure is simplified, but during low-load operation the volume portion of the economizer ports and channels becomes a dead volume causing recompression loss and acting as a leak channel
Solution Approach 1:
During low-load operation, the system extracts or deactivates the economizer function by closing the economizer port in the active compression chamber. This prevents refrigerant from entering the economizer channels where it would otherwise become trapped as dead volume, causing recompression losses and leakage. The economizer infrastructure remains in place for simplicity but is selectively isolated when not needed
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The configuration enables high coefficients of performance during both high-load and low-load operations by minimizing leak and recompression losses, ensuring efficient refrigeration capacity and stability.
Implementation Method 1
a screw rotor (3) having a plurality of screw grooves (5a) formed on an outer circumferential surface... the first gate rotor (6b), the screw groove (5a) and the casing (1) forming, by surrounding, a first compression chamber (5b)... Compressing refrigerant gas to increase pressure and reduce volume
Implementation Method 2
a bypass device including a first slide valve (8a), which is provided only on the first compression chamber (5b) side and configured to slide in the direction of the rotational axis of the screw rotor (3) and to allow the first compression chamber (5b) and a low-pressure chamber to communicate with each other
Implementation Method 3
an intermediate cooler to perform heat exchange between refrigerant and refrigerant to increase, for example, a capacity and improve performance... An economizer pipe (108) one end of which is connected to a pipe between the intermediate cooler (104) and the decompression device (105)... an economizer port (1c) provided in the casing (1) only on the first compression chamber (5b) side to communicate with the first compression chamber (5b)
Data Source
Figure 1
Figure 2~3
Figure 4~4(c)
AI summary
A screw compressor according to an embodiment of the present invention includes an electric motor an rotation speed of which can be changed, a screw rotor including a plurality of screw grooves on an outer circumferential surface, a screw shaft to transmit a driving force of the electric motor to the screw rotor and rotate the screw rotor, a first gate rotor and a second gate rotor respectively disposed on both sides of the screw rotor point-symmetrically with respect to the screw shaft and including, in outer circumferential portions, a plurality of teeth meshed with the screw grooves, a casing having a cylindrical shape to house the screw rotor inside a cylinder, a bypass device to cause a first compression chamber, which is a space surrounded by the first gate rotor, the screw groove, and the casing, and a low-pressure chamber having a suction pressure atmosphere to communicate, and an economizer port provided in the casing to cause fluid flowing from an outside to flow into the first compression chamber.