Variable speed compressor control scheme for lubricant control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Transport climate control systems face lubricant depletion during high-intensity pulldown operations, particularly after door openings and maintenance events, leading to insufficient lubricant recovery.
Innovation Solution
Incorporating a lubricant recovery period into the pulldown operation, utilizing a controller to predict and manage compressor speed and capacity for efficient lubricant return to the sump, ensuring adequate lubrication before shutdown or maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transport climate control system operates at maximum capacity during pulldown operations, then the cooling performance is improved, but the lubricant level in the sump is depleted
Solution Approach 1:
The controller performs preliminary action by detecting when the lubricant level is below a threshold and proactively initiating a mode switch to reduce compressor capacity. This prevents lubricant depletion before it occurs by anticipating the problem based on lubricant level sensors and automatically adjusting operation to allow lubricant recovery.
Solution Approach 2:
The system dynamically adjusts the compressor capacity based on real-time lubricant level conditions. The controller switches between high-capacity mode (for rapid cooling) and reduced-capacity mode (for lubricant recovery), creating a dynamic operating system that adapts to changing lubricant levels rather than operating at fixed maximum capacity.
2Productivity
If successive pulldown operations are performed after door openings, then the climate control responsiveness is improved, but the lubricant in the sump is further reduced
Solution Approach 1:
The system uses feedback from lubricant level sensors to automatically adjust compressor operation. When successive pulldown operations are performed and lubricant levels drop below thresholds, the controller receives feedback and automatically reduces capacity to allow lubricant recovery, preventing further depletion while maintaining climate control functionality.
Solution Approach 2:
The controller implements periodic action by alternating between high-capacity pulldown operations and reduced-capacity recovery periods. This periodic switching allows the system to perform necessary cooling operations while periodically allowing lubricant to return to the sump, preventing cumulative lubricant depletion from successive operations.
3Use of energy by moving object
If the compressor operates at low capacity, then energy consumption is reduced, but lubricant recovery is insufficient
Solution Approach 1:
The system changes operating parameters by switching between distinct capacity modes (high capacity for cooling, reduced capacity for recovery) rather than operating continuously at low capacity. This parameter change allows the system to achieve adequate lubricant recovery while minimizing unnecessary energy consumption that would occur with continuous low-capacity operation.
Data Source
AI summary
A transport climate control system includes a controller. When a pulldown operation is scheduled or performed, the controller can incorporate operation in a lubricant recovery mode into the pulldown operation, and operate the transport climate control system to perform the pulldown operation including the operation in the lubricant recovery mode. The lubricant recovery mode can include operation under conditions such as mass flow rates, compressor speed and/or compressor capacity supporting lubricant circulation, so as to return lubricant to the sump.