Booster Compressor Control for Direct-Drive Refrigeration Capacity
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Solution Overview
Problem
Direct drive compressors in refrigerated vehicles face insufficient capacity during idling and low-speed operations, leading to overheating and potential compressor damage, and existing solutions like electrically driven variable speed compressors are costly and inefficient.
Innovation Solution
An electrically powered variable speed booster compressor is integrated in series with the direct drive compressor to boost suction pressure and act as a pressure limiter, eliminating the need for a compressor pressure regulator and enhancing capacity during high-demand periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct drive compressor is used in refrigerated vehicles, then the system is simple and cost-effective at higher speeds, but the compressor capacity becomes insufficient during idling and low-speed operations
Solution Approach 1:
The patent combines a direct drive compressor with an electrically driven variable speed compressor in a hybrid configuration. The direct drive compressor handles high-speed operations efficiently, while the electrically driven compressor supplements capacity during low-speed and idling conditions, resolving the contradiction between system simplicity and adequate compressor capacity across all operating conditions.
Solution Approach 2:
The patent introduces a variable speed electrically driven compressor that can dynamically adjust its operating speed to match cooling demands. This dynamic capability allows the system to maintain adequate compressor capacity during idling and low-speed operations when the direct drive compressor alone would be insufficient, while keeping the overall system relatively simple.
2Productivity
If an electrically driven variable speed compressor is used to solve capacity insufficiency, then compressor capacity is improved, but the system cost and electrical demand increase substantially
Solution Approach 1:
The patent uses a variable speed electrically driven compressor only partially - specifically during low-speed and idling conditions when the direct drive compressor is insufficient. This partial application of electrical drive capability provides the needed capacity supplement without requiring a full electrical drive system, thereby reducing costs and electrical infrastructure requirements while still solving the capacity problem.
3Reliability
If a compressor pressure regulator is used to limit compressor load during pull down, then compressor overload is prevented, but the regulator becomes unreliable and requires frequent field adjustments
Solution Approach 1:
The patent employs a control system that monitors operating conditions (such as suction pressure, temperature, and compressor runtime) and dynamically adjusts the variable speed electrically driven compressor's operation. This feedback-based control provides reliable compressor protection during pull-down operations without requiring manual pressure regulators, eliminating the reliability and adjustment problems associated with mechanical regulators.
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
The booster compressor effectively addresses capacity insufficiencies and prevents compressor overload, ensuring reliable operation and reducing the risk of damage, while also eliminating the need for costly and unreliable pressure regulators.
Implementation Method 1
an electrically powered variable speed booster compressor is integrated in series with the direct drive compressor to boost suction pressure
Data Source
AI summary
A transport refrigeration system with a direct drive compressor arrangement is provided with a variable speed electrically driven booster compressor that operates in series with the direct drive compressor. The speed of the booster compressor is controlled to either boost or decrease the system capacity. The booster compressor also acts to regulate the flow of refrigerant from the evaporator during periods of operation in which the direct drive compressor might otherwise become overloaded.