Compressor Flooded Start Management Using Bump Start Cycles
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Solution Overview
Problem
Conventional vapor compression systems face issues with 'flooded starts' of compressors, where liquid refrigerant accumulates in the compressor sump during extended shutdowns, potentially causing damage and noise, due to the lack of effective methods to manage liquid refrigerant during start-up.
Innovation Solution
A method involving a series of 'bump starts' is implemented, where the compressor is initiated with short power cycles to evaporate liquid refrigerant from the sump, with pressure and temperature readings used to determine the need for additional cycles until no liquid remains, ensuring a safe and reliable start.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor is started after extended shutdown, then the system can resume operation, but liquid refrigerant accumulates in the compressor sump causing flooded start damage
Solution Approach 1:
The system performs preliminary actions before normal compressor operation by detecting liquid refrigerant in the sump and executing bump start cycles. These preliminary cycles evaporate the accumulated liquid refrigerant through brief compressor activations, ensuring the sump is clear before sustained operation begins, thus preventing flooded start damage while enabling system resumption
Solution Approach 2:
The system uses feedback from pressure differential sensing across the filter drier to determine the presence of liquid refrigerant in the sump. This feedback mechanism triggers the appropriate response (bump start cycles or normal operation) based on the detected condition, creating a closed-loop control system that adapts to the actual state of the compressor
2Reliability
If bump start cycles are performed to evaporate liquid refrigerant, then compressor damage is prevented, but additional time and energy are consumed
Solution Approach 1:
The system applies partial action by performing only the necessary number of bump start cycles required to evaporate the liquid refrigerant. Rather than continuous operation or excessive cycling, the controller executes just enough brief compressor activations to clear the sump, then transitions to normal operation, optimizing the balance between protection and time efficiency
3Speed
If liquid refrigerant is present in the sump during start-up, then the compressor can begin operation quickly, but permanent damage to compression elements occurs
Solution Approach 1:
The system applies preliminary anti-action by detecting the presence of liquid refrigerant and counteracting its harmful effects before they can damage the compression elements. The bump start cycles create controlled evaporation that removes the liquid refrigerant threat before normal high-speed operation begins, preventing liquid slugging while enabling quick system resumption
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
This approach effectively manages flooded starts by ensuring only the necessary number of bump starts are performed, reducing the risk of compressor damage, noise, and extending motor life by ensuring only vapor is present at system initiation.
Implementation Method 1
initiating an initial bump start of the compressor; terminating the initial bump start; determining whether a working fluid in a liquid state remains in a sump of the compressor
Data Source
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Figure 2
AI summary
A method is provided for managing a flooded start of a compressor in a vapor compression system. Following an initial bump start, a determination is made as to whether working fluid in a liquid state remains in the sump of the compressor. If working fluid in a liquid state remains in the compressor sump, an additional bump start of the compressor is completed, followed by another determination as to whether working fluid in a liquid state still remains in the compressor sump. If working fluid in a liquid state remains in the compressor sump, another bump start of the compressor is initiated and the sequence repeated until no working fluid in the liquid state remains in the compressor sump. A normal start of the compressor may be initiated after determining no working fluid in the liquid state remains in the compressor sump.