Electronic Throttle Valve Control for Compressor Flooding in TRUs
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Solution Overview
Problem
Transport refrigeration units (TRUs) face the risk of liquid refrigerant flooding in the compressor during heating/defrosting modes or transitions, leading to dilution of lubricating oil and potential mechanical failures.
Innovation Solution
Implementing a method to control the electronic throttle valve (ETV) by measuring refrigerant discharge temperature and comparing it to the saturated discharge temperature, closing down the ETV when the difference is below a certain threshold to prevent liquid refrigerant from entering the compressor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the TRU operates in heating/defrosting mode or transition mode, then the refrigeration system can provide heating or defrosting function, but liquid refrigerant may flood the compressor causing dilution of lubricating oil and mechanical failures
Solution Approach 1:
The control system detects the heating/defrosting mode or transition mode condition in advance and proactively closes the electronic throttle valve before liquid refrigerant can flood the compressor. This preliminary action prevents the harmful effect from occurring in the first place
Solution Approach 2:
The electronic throttle valve acts as an intermediary device between the refrigerant source and the compressor. By controlling the valve opening, it mediates the refrigerant flow to prevent liquid refrigerant from reaching the compressor while still allowing the system to operate in heating/defrosting mode
2Reliability
If the electronic throttle valve is closed down to prevent liquid flooding, then compressor reliability is improved, but refrigerant flow control complexity increases
Solution Approach 1:
The control system continuously monitors system conditions (temperature, pressure, mode of operation) and uses this feedback to automatically adjust the electronic throttle valve position. This closed-loop control achieves reliable flood prevention through automated decision-making based on real-time system state
3Productivity
If liquid refrigerant floods the compressor, then refrigerant circulation continues, but lubricating oil is diluted and mechanical components suffer from reduced lubrication
Solution Approach 1:
The electronic throttle valve extracts or removes liquid refrigerant from the flow path before it can enter the compressor. By closing or modulating the valve, it prevents the harmful liquid refrigerant from reaching the compressor while maintaining necessary refrigerant circulation through the system
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
Reduces the risk of compressor flooding and subsequent mechanical failures by limiting the amount of liquid refrigerant entering the compressor, ensuring proper lubrication and operation.
Implementation Method 1
an electronic throttle valve (ETV) that is configured to control a volume of a refrigerant flowing into the compressor
Implementation Method 2
a compressor, a condenser, an expansion device (e.g. an expansion valve) and an evaporator, which form a refrigeration circuit
Implementation Method 3
an expansion device (e.g. an expansion valve) and an evaporator, which form a refrigeration circuit
Implementation Method 4
a compressor, a condenser, an expansion device (e.g. an expansion valve) and an evaporator, which form a refrigeration circuit
Data Source
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AI summary
A method to reduce/prevent liquid refrigerant flooding in the compressor is disclosed herein. The method may include closing down the ETV when there is a risk of compressor flooding. The method may include closing down the ETV to a desired value when there is a risk of the compressor flooding. A failure to provide the superheated refrigerant vapor in a desired superheat temperature by the compressor may indicate a risk of the compressor being flooded by liquid refrigerant. The method may include measuring a refrigerant discharge temperature of the compressor, and closing down the ETV when a difference between the refrigerant discharge temperature of the compressor and a refrigerant saturate temperature is below a desired temperature threshold.