Numerical Analysis And Optimization Of Influencing Factors On Sampling Accuracy Of Automatic Biochemical Analyzer

The automatic biochemical analyzer is an automatic detection device that provides various biochemical detection items,and plays an important role in the diagnosis,treatment and prevention of diseases.With the continuous improvement of the detection accuracy requirements in the modern biochemical field,these research fields have also put forward higher requirements for the sampling accuracy of the automatic biochemical analyzer.At present,the optimization analysis of automatic biochemical analysis instruments is mainly aimed at hardware systems and software systems.Both of these research ideas ignore the influence of various factors in the sampling system on the sampling accuracy of the automatic biochemical analyzer.Therefore,this paper uses CFD technology to analysis of multiple factors of sample addition accuracy in the sampling system.First,the operating principle of the automatic biochemical analyzer is analyzed to confirm the necessity of taking the sampling system as the research object.Then,the components of the sampling system and the influencing factors of the sample addition accuracy are analyzed in more detail.Confirm that the sampling process of the sampling needle and the startup process of the precision plunger pump are the key research objects.The sampling process of the sampling needle is realized by the VOF model in the FLUENT software.By simulating the sampling needles with different diameter-changing position,it was found that the sample-adding needle with a diameter-changing position of 6.5 mm is more conducive to improving the dripping efficiency of liquid drops,avoiding the splashing phenomenon of satellite liquid drops and the hanging phenomenon of liquid drops at the needle mouth at the end of sample-adding.By simulating the sampling needles with different chamfer angles,it was found that the chamfering treatment of the sampling needle can effectively promote the droplet dripping and reduce the splash of satellite droplets.The 45-degree chamfered sampling needle is more conducive to reducing the adsorption force on liquid drops at the initial stage of sample adding,while the 30-degree chamfered sample adding needle is more conducive to avoiding pressure pulses generated when liquid drops drop.The starting process of the precision plunger pump is realized by the dynamic grid technology in the FLUENT software.Through the simulation of precisionplunger pumps with different initial starting frequencies,it was found that the increase of initial starting frequency causes the initial pressure pulse in the sampling system to increase obviously,but has little influence on the secondary pressure pulse.Finally,an experimental platform was built to verify the effectiveness of the simulation,and through further analysis,it was found that the sample suction error volume would increase with the increase of the initial start frequency,and the stability of the sample addition would increase with the increase of the initial start frequency.Larger and smaller,the combined effect of the above two factors makes the sampling error the smallest when the initial starting frequency is 360 Hz.In addition,this paper analyzes and compares the three speed control curves of the precision plunger pump,and designs a new type of speed control curve based on the S-shaped speed control curve.The curve realizes the uniform movement of the plunger of the precision plunger pump in the initial start-up period by controlling the time step,significantly reduces the variation coefficient of sample suction and the variation coefficient of sample addition,and improves the sampling accuracy and the sampling stability of the automatic biochemical analyzer.