Scroll Compressor Back Pressure Control Valve
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Solution Overview
Problem
In scroll compressors with a gas injection cycle, optimizing back pressure is challenging due to variations in injection pressure, which can lead to insufficient or excessive force on the orbiting scroll, resulting in refrigerant leakage, decreased compression efficiency, and mechanical issues like galling of wraps.
Innovation Solution
A back pressure control valve adjusts the pressure in the back pressure chamber based on suction, discharge, and injection pressures to maintain a target back pressure, optimizing the force on the orbiting scroll and enhancing compression efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the injection pressure is high, then the back pressure may be insufficient and the force pressing the orbiting scroll against the fixed scroll may become weak, but this causes leakage of gaseous refrigerant from the compression chamber and decrease in compression efficiency
Solution Approach 1:
The back pressure control valve dynamically adjusts the back pressure parameter based on the injection pressure to maintain optimal pressing force. When injection pressure varies, the valve modifies the back pressure accordingly to prevent both insufficient pressing force and excessive pressing force, thereby preventing refrigerant leakage and maintaining compression efficiency.
Solution Approach 2:
The back pressure control valve operates as a feedback control mechanism that responds to changes in injection pressure. By continuously monitoring the injection pressure and adjusting the back pressure in response, the system maintains the optimal pressing force on the orbiting scroll, preventing refrigerant leakage and compression efficiency loss.
2Force
If the injection pressure is low, then the back pressure may be excessive, but this causes increased drive force making the orbiting scroll revolve, resulting in decrease in compression efficiency and galling of wraps of the scrolls
Solution Approach 1:
The back pressure control valve dynamically adjusts the back pressure parameter downward when injection pressure is low. This prevents excessive back pressure that would otherwise increase the drive force on the orbiting scroll, reduce compression efficiency, and cause galling of the scroll wraps.
Solution Approach 2:
The back pressure control valve functions as a feedback control system that detects low injection pressure and responds by reducing back pressure. This feedback mechanism prevents the adverse effects of excessive back pressure, including increased scroll revolution drive force, reduced compression efficiency, and wrap galling.
3Device complexity
If the back pressure is not optimized according to injection pressure, then the system structure remains simple, but this results in refrigerant leakage, decreased compression efficiency, and mechanical issues like galling of wraps
Solution Approach 1:
The back pressure control valve serves as an intermediary component between the injection system and the compression chamber. It mediates the relationship between injection pressure and back pressure, ensuring that the pressing force on the orbiting scroll remains optimal regardless of injection pressure variations, thereby preventing refrigerant leakage and mechanical failures.
Solution Approach 2:
The back pressure control system is designed to be dynamic rather than static. The back pressure control valve can adjust the back pressure in real-time according to injection pressure changes, enabling the system to adapt to varying operating conditions and maintain reliable compression operation without excessive structural complexity.
Data Source
AI summary
An object is to optimize a back pressure pressing an orbiting scroll against a fixed scroll in a scroll compressor to which an injection cycle is applied. A back pressure control valve (400) adjusting back pressure (Pm) in a back pressure chamber (H4), adjusts the opening degree of a first valve body (424) increasing and decreasing the flow rate of lubricant which has been separated from gaseous refrigerant compressed in a compression chamber and is supplied to the back pressure chamber (H4), in accordance with suction pressure (Ps) in a suction chamber (H1), discharge pressure (Pd) in a discharge chamber (H2), and injection pressure (Pinj). Then, the back pressure control valve (400) increases and decreases the lubricant flow rate in accordance with injection pressure (Pinj) as well as suction pressure (Ps) and discharge pressure (Pd), to adjust back pressure to target back pressure varying in accordance with injection pressure (Pinj).