Centrifugal E-Compressor Startup Heating for Liquid Refrigerant Ingestion
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Solution Overview
Problem
Centrifugal-type refrigerant E-compressors in battery electric vehicles (BEVs) are prone to failure or damage due to liquid refrigerant accumulation when the vehicle is switched off for extended periods, especially at low ambient temperatures, leading to increased starting torque requirements exceeding the capabilities of the electric motor and potential compressor damage.
Innovation Solution
A method involving an engine control unit (ECU) that monitors refrigerant state at the compressor inlet, activating a heating unit to vaporize any liquid refrigerant before starting the compressor, using existing PTC heaters for cabin heating to avoid additional components, and delaying compressor startup until the refrigerant is fully gaseous.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle is switched off for extended periods at low ambient temperatures, then liquid refrigerant accumulates in front of the compressor, but this causes increased starting torque requirements that exceed the electric motor's capabilities and may damage the compressor
Solution Approach 1:
The system performs preliminary heating of the compressor inlet area using PTC heaters before compressor startup. This preliminary action vaporizes accumulated liquid refrigerant, ensuring the refrigerant is in gaseous state before the compressor begins operation, thereby preventing liquid ingestion and reducing starting torque requirements.
Solution Approach 2:
The system changes the temperature parameter at the compressor inlet by activating PTC heaters. This parameter change transforms the refrigerant from liquid state to gaseous state, making it suitable for compression and reducing the torque required for startup.
2Reliability
If a heating unit is added to vaporize liquid refrigerant before compressor startup, then compressor reliability improves, but device complexity increases
Solution Approach 1:
The PTC heaters serve multiple functions: they provide cabin heating/defrosting during normal operation and simultaneously vaporize liquid refrigerant at the compressor inlet during startup conditions. This multi-functionality eliminates the need for dedicated heating components, maintaining system reliability while avoiding increased complexity.
Solution Approach 2:
The existing PTC heating system serves the dual purpose of cabin thermal management and refrigerant vaporization. The system uses its own existing heating capability to solve the liquid refrigerant accumulation problem, rather than requiring separate dedicated components.
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
Prevents compressor failure and damage by ensuring a gaseous state at startup, enhancing reliability and extending compressor life in BEVs.
Implementation Method 1
issuing a command to operate the heating unit to cause heat transfer to the refrigerant in the inlet to cause vaporization of liquid refrigerant
Implementation Method 2
heat transfer to the refrigerant in the inlet to cause vaporization of liquid refrigerant
Data Source
AI summary
An air conditioning system for an electric vehicle includes a refrigerant E-compressor made up of a centrifugal compressor and an electric motor for driving the compressor. The housing of the compressor defines a coolant passage for liquid coolant. A coolant unit pumps liquid coolant through the coolant passage during normal AC system operation to cool the motor. A method for preventing or mitigating harmful effects of liquid refrigerant being ingested by the compressor includes determining whether liquid refrigerant is likely present in the compressor inlet; if so, a heating unit raises the temperature of the liquid coolant to thereby heat and evaporate any liquid refrigerant before starting the compressor. Once the danger of liquid refrigerant is passed, the compressor is started and the heating unit is deactivated.