Liquid Feeding Device Isothermal Pre-Compression Control
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Solution Overview
Problem
Liquid feeding devices in HPLC systems face challenges in maintaining stable flow rates due to temperature increases during pre-compression, leading to pulsation and reduced accuracy, which existing thermal compensation controls cannot fully address.
Innovation Solution
The liquid feeding device adjusts the pre-compression speed based on feeding pressure, compressivity, and the state of other plunger pumps to ensure the pre-compression process is performed isothermally, using sensors and control systems to determine optimal speeds and complete the process before transitioning to discharge, thereby minimizing temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If pre-compression operation is performed to increase pump chamber pressure before discharge, then pressure stability is improved, but temperature increase causes volumetric shrinkage and pulsation
Solution Approach 1:
The system performs preliminary cooling of the mobile phase in the pump chamber before pre-compression operation begins. This preliminary action removes heat that would otherwise be generated during compression, preventing temperature increase and volumetric shrinkage while still achieving the necessary pressure buildup for stable discharge
Solution Approach 2:
The system alternates between cooling periods and pre-compression periods in a cyclic manner. During cooling periods, the mobile phase is cooled to remove heat; during pre-compression periods, pressure is increased. This periodic alternation prevents continuous temperature buildup while maintaining pressure stability requirements
2Reliability
If pre-compression operation is performed to prevent backflow and stabilize pressure, then feeding flow rate stability is improved, but heat generation during compression reduces liquid feeding accuracy
Solution Approach 1:
The system uses temperature sensors to monitor mobile phase temperature in real-time during pre-compression operation. When temperature approaches thresholds that would cause volumetric shrinkage, the control system automatically adjusts or pauses pre-compression activity. This feedback mechanism maintains feeding flow rate stability while preventing temperature-related accuracy degradation
Solution Approach 2:
The system performs preliminary cooling of the mobile phase before initiating pre-compression operation. This preliminary heat removal ensures that subsequent compression occurs at controlled temperatures, preventing volumetric shrinkage and maintaining liquid feeding accuracy while still achieving pressure stabilization
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 effectively suppresses temperature increases and pulsation, enhancing the stability and accuracy of liquid feeding by ensuring the pre-compression process is completed isothermally, even under varying pressures and flow rates.
Implementation Method 1
When the pre-compression operation is performed, a mobile phase sucked into a pump chamber is compressed to generate heat, a temperature of the mobile phase increases
Implementation Method 2
After the above, in a process of flowing through a channel, the mobile phase discharged from the pump chamber is deprived of heat by a channel wall surface and the like to be cooled, and the volume shrinks
Data Source
AI summary
A liquid feeding device includes a discharge channel, a pump part, a feeding pressure sensor, a non-discharge pressure sensor, a pre-compression part, and a pre-compression speed determination part. The pump part has plunger pumps connected in series or parallel. At least one of the plunger pumps is a closed pump in which communication with the discharge channel is disconnected during a non-discharge time. The pre-compression part causes the closed pump that is after the suction process for sucking the liquid into a pump chamber is completed and during the non-discharge time to execute a pre-compression process to perform a discharge operation until a non-discharge pressure is substantially the same as a feeding pressure based on output of the feeding pressure sensor and output of the non-discharge pressure sensor. The pre-compression speed determination part determines a pre-compression speed of the closed pump in the pre-compression process.