Efficient control algorithm for start-stop operation of a refrigeration unit powered by engine
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Solution Overview
Problem
Current start-stop operation modes in transport refrigeration units are not optimized for efficiency, leading to suboptimal fuel conservation and cooling performance, as they do not consider modifications to engine speeds, runtime, and compressor displacement capacity.
Innovation Solution
A method and system for controlling a refrigeration unit powered by an engine, where the engine operates at reduced speeds during start-stop operations, with a controller adjusting engine speed and compressor displacement capacity to minimize fuel consumption and optimize cooling efficiency by extending the delay period and increasing compressor capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine operates at reduced speeds during start-stop operations, then fuel consumption is reduced, but the cooling performance deteriorates
Solution Approach 1:
The system dynamically adjusts engine speed based on operational phase: reduced speed during delay period for fuel savings, then increased speed during active cooling for adequate cooling performance. This dynamic speed adjustment resolves the contradiction between fuel consumption and cooling performance.
Solution Approach 2:
The refrigeration system uses periodic start-stop operation with alternating phases: a delay period with reduced engine speed followed by an active cooling period with normal engine speed. This periodic action allows fuel savings during idle periods while maintaining cooling capability during active periods.
2Use of energy by moving object
If the delay period is extended to allow reduced engine speed, then fuel consumption is reduced, but the time to reach setpoint temperature increases
Solution Approach 1:
The system performs preliminary cooling action during the delay period at reduced speed to lower the temperature before the main cooling phase. This preliminary action reduces the total cooling load required later, compensating for the extended delay period and reducing overall time to reach setpoint temperature.
Solution Approach 2:
The system changes operational parameters by adjusting engine speed and compressor displacement capacity based on the extended delay period. The compressor displacement is increased to compensate for the longer delay, ensuring that cooling performance is maintained despite the extended time before active cooling begins.
3Productivity
If the compressor displacement capacity is increased to compensate for reduced engine speed, then cooling performance is maintained, but device complexity increases
Solution Approach 1:
The compressor is designed with variable displacement capacity that can be adjusted to serve multiple functions: standard displacement during normal operation and increased displacement during start-stop operations with extended delay periods. This multi-functionality allows the same component to maintain cooling performance across different operational modes without adding separate systems.
Solution Approach 2:
The compressor displacement capacity is dynamically adjusted based on operational conditions. During start-stop operations with extended delay periods, the displacement is increased to compensate for reduced engine speed. This dynamic adjustment maintains cooling performance without requiring permanently oversized components, thus avoiding excessive complexity.
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
This approach reduces fuel consumption and enhances cooling efficiency by optimizing engine speed and compressor displacement, allowing the refrigeration unit to reach setpoint temperature with minimal fuel usage while maintaining effective cooling performance.
Implementation Method 1
a compressor operatively coupled to the engine
Implementation Method 2
Refrigeration systems serve to remove heat from a substantially enclosed area and transfer the heat to an environment external to the enclosed area
Data Source
AI summary
A refrigeration unit and a method for controlling same during start-stop operation is provided. The refrigeration unit may include an engine operable between at least a low engine speed and a high engine speed, a compressor operatively coupled to the engine, and a controller operatively coupled to each of the engine and the compressor. The controller may be configured to operate the engine at a reduced low speed during a delay period, extend the delay period based on the reduced low speed, increase a displacement capacity of the compressor based on the extended delay period, and operate the engine at a reduced high speed.