Variable Speed Compressor Blowdown Valve Shutdown Control
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Solution Overview
Problem
Conventional rotary air compressors experience backflow due to negative pressure gradients when stopped, especially without an inlet valve, leading to potential damage and inefficiencies.
Innovation Solution
A compressor system with a blowdown valve and variable speed drive that reduces pressure by adjusting compressor speed and opening the blowdown valve in response to shutdown signals, eliminating the need for an inlet valve and minimizing backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the compressor is stopped without an inlet valve, then the system complexity is reduced and costs are lowered, but backflow occurs through the inlet causing potential damage and inefficiencies
Solution Approach 1:
The blowdown valve opens before the compressor stops to preemptively equalize pressure and eliminate the negative pressure gradient that causes backflow. This preliminary action prevents the harmful effect before it can occur during shutdown
Solution Approach 2:
The blowdown valve acts as an intermediary device that mediates between the compressed air system and the atmosphere, controlling pressure equalization during shutdown to prevent backflow through the inlet
2Reliability
If the blowdown valve is opened immediately upon shutdown signal, then backflow is prevented, but energy is wasted by releasing compressed air
Solution Approach 1:
The compressor speed is dynamically adjusted to a low set point rather than stopping immediately, and the blowdown valve timing is dynamically controlled based on system state. This dynamic approach balances backflow prevention with energy conservation by maintaining minimal operation during pressure equalization
Solution Approach 2:
The system changes operational parameters by setting compressor speed to a low set point and controlling blowdown valve timing. These parameter changes optimize the balance between preventing backflow and minimizing energy loss from compressed air release
3Use of energy by moving object
If the compressor speed is reduced to a low set point, then energy consumption is reduced, but the compressor may not meet minimum flow requirements
Solution Approach 1:
The system uses periodic cycling between low set point operation and shutdown states. During each cycle, the compressor operates at low speed to meet minimal flow needs while consuming reduced energy, then shuts down when flow demand is satisfied by stored compressed air
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 system effectively reduces backflow and energy consumption by strategically managing compressor speed and pressure relief, maintaining efficient operation and reducing system complexity and costs.
Implementation Method 1
A blowdown valve is movable between a closed position and an open position in which at least a portion of the flow of compressed fluid passes through the blowdown valve to reduce the pressure of the flow of compressed fluid
Implementation Method 2
a compression device operable between a first speed and a second speed to produce a flow of compressed fluid at a pressure
Data Source
AI summary
A compressor system operable to shutdown in response to a shutdown signal. The compressor system includes a compression device operable between a first speed and a second speed to produce a flow of compressed fluid at a pressure. A blowdown valve is movable between a closed position and an open position in which at least a portion of the flow of compressed fluid passes through the blowdown valve to reduce the pressure of the flow of compressed fluid. A sensor is positioned to measure the pressure and a controller is operable to move the blowdown valve to the open position and set the speed of the compression device to a low set point speed in response to the shutdown signal.