Two-Stage Screw Compressor Idle Control With Variable-Speed Stages
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling twin-screw compressors during idle operation result in high energy consumption and require complex design elements like throttle valves and intake regulators, which increase manufacturing costs.
Innovation Solution
A method that controls the compressor stages independently with variable speed, using a blow-off valve and reducing rotational speed to idle speeds, eliminating the need for throttle valves and intake regulators, while maintaining outlet pressure and temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a throttle valve and intake regulator are used to control idle operation, then the compressor can maintain constant pressure conditions in both stages, but energy consumption increases significantly and device complexity increases
Solution Approach 1:
The patent removes the throttle valve and intake regulator from the system entirely. Instead of using these components to control idle operation, the system relies on the blow-off valve and the natural compression characteristics of the two stages, thereby eliminating the source of high energy consumption and mechanical complexity associated with throttle control
Solution Approach 2:
The patent changes the control parameter from throttle position to rotational speed. By controlling the rotational speed of the compressor stages during idle operation, the system achieves pressure stability without the energy losses and complexity of throttle valve control
2Reliability
If a throttle valve and intake regulator are used to control idle operation, then the compressor can maintain constant pressure conditions in both stages, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent removes the throttle valve and intake regulator from the system entirely. Instead of using these components to control idle operation, the system relies on the blow-off valve and the natural compression characteristics of the two stages, thereby eliminating the source of high energy consumption and mechanical complexity associated with throttle control
3Reliability
If the blow-off valve is opened during idle operation, then compressed air can be vented to prevent pressure overshoot, but energy is wasted through the blow-off
Solution Approach 1:
The patent dynamically adjusts the rotational speed of the compressor stages during idle operation. By reducing the speed of the first stage while maintaining or adjusting the second stage speed, the system minimizes the volume flow requiring blow-off, thereby reducing energy waste while maintaining pressure control
Solution Approach 2:
The patent changes the control parameter from blow-off valve position to rotational speed. By controlling the rotational speed of the compressor stages during idle operation, the system achieves pressure stability with minimal blow-off requirement, thereby reducing energy loss
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
Significantly reduces energy consumption and simplifies the compressor design, allowing quick transition to load operation with reduced wear and temperature fluctuations.
Implementation Method 1
a first compressor stage compresses a gaseous medium, usually air, and feeds it to a second compressor stage, which further compresses the medium
Data Source
Figure 1
Figure 2
AI summary
The disclosure relates to a method for controlling a screw compressor with at least one first and one second compressor stage, both compressor stages being driven separately from one another and with variable speed. According to the disclosure, the following steps are carried out: detecting a volume flow taken at the outlet of the second compressor stage; Adjusting the speed of both compressor stages when the volume flow taken fluctuates in a range between a maximum value and a minimum value; Opening a relief valve when the volume flow falls below the minimum value; reducing the speed of at least the first compressor stage to a predetermined idle speed (V1L) to reduce the volumetric flow delivered from the first to the second compressor stage. The disclosure also relates to a compressor with a screw compressor, which comprises at least a first and a second compressor stage, with both compressor stages being driven separately from one another and with variable speed, and with a control unit being provided which is configured to carry out the aforementioned method.