Closed loop capacity and power management scheme for multi stage transport refrigeration system
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Solution Overview
Problem
Refrigeration systems in transport face challenges with power management due to limited engine capacity, leading to unstable operation and inefficiencies in multi-stage compression cycles, where aggressive engagement of higher stages can cause engine stalling or underutilization of power.
Innovation Solution
A controller monitors engine performance parameters to throttle refrigeration power and configure a multi-stage compression cycle in either serial or parallel fashion, allowing for smooth power management by adjusting the operation of valves to maximize power utilization while mitigating engine overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a higher stage of the multi stage compression cycle is aggressively engaged to maximize cooling capacity, then the cooling performance is improved, but the engine is subjected to high probability of stalling due to power overload
Solution Approach 1:
The system dynamically adjusts the engagement of compression stages based on real-time engine performance parameters. The controller continuously monitors engine metrics and modulates the refrigeration power demand accordingly, transitioning between single stage and higher stage operation to maintain engine stability while maximizing cooling capacity when available.
Solution Approach 2:
The controller implements a closed-loop control system that monitors engine performance parameters and uses this feedback to throttle refrigeration power demand. When engine performance declines beyond a threshold, the controller reduces power demand to prevent stalling, and when performance is adequate, allows higher stage engagement for maximum cooling.
2Reliability
If a higher stage of the multi stage compression cycle is passively engaged to protect engine stability, then the engine stalling risk is reduced, but the available engine power is under-utilized by the refrigeration unit
Solution Approach 1:
The system dynamically adjusts the engagement of compression stages based on real-time engine performance parameters. The controller continuously monitors engine metrics and modulates the refrigeration power demand accordingly, transitioning between single stage and higher stage operation to maintain engine stability while maximizing cooling capacity when available.
Solution Approach 2:
The controller proactively monitors engine performance parameters and anticipates power availability changes. By detecting trends in engine performance before critical thresholds are reached, the controller can preemptively adjust refrigeration power demand to prevent stalling while maximizing power utilization during favorable conditions.
3Power
If traditional suction throttling is used to manage power overload in higher stage operation, then the power demand is reduced, but the midstage injection flow becomes inefficient and troublesome
Solution Approach 1:
The system extracts and removes the problematic suction throttling mechanism from the power management approach. Instead of throttling midstage injection flow, the controller directly modulates the engagement and power demand of compression stages, eliminating the inefficiencies and operational troubles associated with traditional suction throttling methods.
Data Source
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AI summary
A unit, such as a transport refrigeration unit 12, may include a plurality of components arranged in multiple stages. At least a portion of the components 18,20 may be arranged in a serial or parallel manner. A position associated with the plurality of components may be selected to control a load on a power source, such as an engine 30. For example, a position for each of the components may be selected so as to maximize a delivery of available power from the power source to the unit. In some embodiments, one or more controllers 32,34 may measure a parameter associated with the power source and select a position for one or more of the components. In some embodiments, an economized refrigeration cycle may be used. Capacity may be staged from a single stage compression cycle or mode to a multistage compression cycle or mode, with a corresponding increase in capacity via subcooling.