Multi-Stage Transport Refrigeration Power Control Against Engine Stall
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Solution Overview
Problem
Refrigeration systems in transport face challenges with power management due to limited engine capacity, leading to potential stalling or underutilization of power, especially in multi-stage compression cycles, where aggressive engagement of higher stages can cause engine overload or inefficient suction throttling.
Innovation Solution
Implementing a controller to monitor engine performance parameters and selectively control power supply to refrigeration stages, allowing for smooth transition between single and higher stages in a serial configuration, or independent power control in parallel stages, to maximize power utilization and prevent 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 refrigeration effect 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 RPM, load, and other parameters, and selectively engages or disengages higher compression stages to match available engine power, preventing stalling while maximizing cooling capacity when power is available.
Solution Approach 2:
The system implements a closed-loop control mechanism where the controller monitors engine performance parameters and uses this feedback to adjust the engagement of compression stages. When engine performance declines or power reserve is insufficient, the controller reduces engagement of higher stages to prevent stalling, creating a feedback-based adaptive power management system.
2Reliability
If a higher stage of the multi stage compression cycle is passively engaged to prevent engine overload, then engine stalling is avoided, but the available engine power is under-utilized by the refrigeration unit
Solution Approach 1:
The system transitions from passive to dynamic engagement control. Instead of always delaying higher stage engagement, the controller actively monitors engine power reserve and performance parameters, engaging higher compression stages as soon as sufficient power reserve is detected, thereby maximizing power utilization while maintaining stalling prevention.
Solution Approach 2:
The system performs preliminary assessment of engine power reserve and performance parameters before engaging higher compression stages. The controller evaluates whether sufficient power reserve exists and proactively adjusts stage engagement accordingly, enabling timely engagement that maximizes power utilization without causing overload.
3Power
If traditional suction throttling is used to manage power overload in higher stages, then engine power demand is reduced, but the midstage injection flow becomes inefficient and troublesome
Solution Approach 1:
The system extracts and removes the inefficient suction throttling mechanism from the power management approach. Instead of throttling midstage injection flow, the system selectively engages or disengages entire compression stages based on power availability, eliminating the problematic throttling operation while maintaining effective power demand management.
Solution Approach 2:
The controller acts as an intermediary that manages power demand by controlling stage engagement rather than throttling flow. This intermediary control mechanism replaces the direct but inefficient suction throttling approach with a higher-level strategic control that engages/disengages stages based on power reserve assessment.
Data Source
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.