Oil-Free Screw Compressor Startup Reliability via Shared Drain Control
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Solution Overview
Problem
Oil-free screw compressors face issues with startup reliability due to negative air pressure in the control pipeline, leading to condensate leakage, flow noises, and compressed air leakage, especially when transitioning from a loadless to a loaded mode, and existing drainage systems do not effectively prevent these issues.
Innovation Solution
The compressor incorporates a structure where the control pipeline doubles as a drain pipeline, with a drain valve that can be opened to atmosphere only when necessary, allowing adjustable drainage time and interval based on operational conditions, ensuring reliable startup and reduced leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control pipeline is opened to the atmosphere via an orifice to obtain required air pressure at startup, then the suction throttle valve becomes openable, but condensate leakage, flow noises, and compressed air leakage occur
Solution Approach 1:
The patent merges the control pipeline and drain pipeline into a single integrated pipeline system. The drain valve serves dual functions: controlling drainage during operation and opening the control pipeline to atmosphere during startup to provide required air pressure for the suction throttle valve. This eliminates the need for a separate orifice in the control pipeline, preventing condensate leakage, flow noises, and compressed air leakage while maintaining startup reliability.
Solution Approach 2:
The drain valve is designed with multi-functionality, serving both as a drainage control valve during operation and as an atmospheric vent for the control pipeline during startup. This universal component replaces the need for separate components (orifice in control pipeline + separate drain valve), eliminating the harmful effects associated with the orifice while maintaining both drainage and startup functions.
2Loss of energy
If drainage is performed intermittently to reduce compressed air leakage, then compressed air leakage is reduced, but reliable drainage control becomes more complex
Solution Approach 1:
The drainage system employs dynamic control through automated timing mechanisms that adjust the drain valve operation based on operational conditions. The drain valve opens intermittently according to predetermined time intervals and durations, dynamically adapting to different operational states (startup, operation, shutdown). This dynamic approach minimizes compressed air leakage while maintaining effective drainage, and the automated timing control simplifies the overall system compared to manual or complex mechanical control mechanisms.
Data Source
AI summary
A multi-stage oil-free screw compressor includes: a suction throttle valve for controlling air intake into the compressor; a piston assembly for operating the suction throttle valve; and a structure for supplying a working pressure to the piston assembly. In order to reduce startup load at the time of startup of the compressor, the suction throttle valve is fully closed while a secondary side of a compressor body is opened to the atmosphere. When a negative pressure and the air pressure, that provide the working pressure, are used for slightly opening the suction throttle valve in order to switch the compressor to a loaded mode after a motor for driving the compressor is accelerated to its top speed, the air pressure is provided by a control pipe line that is defined by the same pipe line that forms a drain pipe line. This permits the control pipe line to be opened to the atmosphere as needed during the startup time. Thus is provided the oil-free screw compressor achieving improved startup reliability.