Research On Quantitative Evaluation Technology Of Forming Accuracy For Corrugated Plate Of Plate Heat Exchanger

In the petrochemical,hydraulic equipment,nuclear power plant and other industrial fields,plate heat exchanger as a general fluid heat exchange equipment,has been widely used in recent years with its unique advantages in high-efficiency heat exchange.As the core pressurebearing parts of the heat exchange system,corrugated plate has a complex surface geometry and its service environment is very bad.The quantitative evaluation to the forming accuracy of corrugated plate plays an important role in ensuring the plate manufacturing quality and the reliable operation of heat exchange system.In this paper,aiming at the current situation that the accuracy evaluation of corrugated plate relies too much on manual work,it is difficult to meet the automatic detection requirements of high precision,high efficiency and full inspection.On the basis of in-depth analysis of the characteristics for these existing digital detection technologies,a technical scheme based on point laser triangulation method is developd to realize the quantitative evaluation for the forming accuracy of corrugated plate.Limited by the complex detection conditions and the strict test requirements,the following technical problems will be faced in the implementation process of such scheme:(1)due to the limitation of effective scanning field of point laser sensor,the single sampling scale is limited,so there is a problem of low measurement efficiency;(2)due to the limitation of optical measurement technology,the system measurement accuracy will be affected by the interference of optical characteristics,morphology structure,measurement conditions and other factors;(3)due to the discrete characteristics of laser point cloud and the large-scale complexity of plate shape,the high-precision and efficiency detection to the forming accuracy of corrugated plate cannot be realized by the overall processing to measurement data.In view of the above problems,this paper studies the construction of digital inspection system,sampling planning,measurement error correction,and the detection for the characterization parameters of forming accuracy.The specific research work is as follows:Construct a digital inspection system for forming accuracy of corrugated plate.According to the specific detection standard,a detection system scheme is designed,which uses the mechanical arm to integrate dual laser displacement sensors to beam synchronously scanning,and an experimental detection platform is built using a CNC machine tool.The calibration deviation of the system is 0.036 mm,which shows that the measurement system can meet the test requirements to the forming accuracy of corrugated plate.Research the scanning path planning method for the high-efficiency extraction of plate topography data.In view of the problem that the laser displacement sensor is difficult to achieve rapid measurement,it is revealed that the quality distribution law to the forming process of corrugated plate,that is the forming defects such as wall thickness out of tolerance mainly occurs in both ends of the flow guide zone;a total sampling strategy is proposed to implement high-density sampling and sparse sampling respectively for the flow guide area and heat exchange zone;and an adaptive sampling method based on the curvature change of measured points is constructed to realize the effective simplification of data sampling.The experimental evaluation results indicate that the sampling planning method constructed in this paper can greatly improve the measurement efficiency(the maximum is about 33%),and can provide a good technical foundation for the rapid realization of system sampling.Research the accuracy control method for the high-precision extraction of plate topography data.Aiming at the problem that the oil film attached on the surface of the plate and the irregular change of curvature can easily affect the system measurement accuracy,an error correction model related to the properties(refractive index and thickness)of the attached oil film is proposed.Through the tilt test,it is revealed that when the measured target is in the center of the measuring range of the laser probe,the influence about the variation of probe scanning depth on the sampling accuracy can be approximately ignored;accordingly,error correction model related to the incident angle and azimuth angle of the laser probe is proposed.The evaluation results for these error compensation models show that the maximum comparison deviation of the former is 20%,and that of the latter is about 65%.Research a high-precision and fast extraction method to the characterization parameters of plate forming accuracy.Aiming at the problem that those parameters cannot be directly obtained from the discrete measurement points,by using the point model reconstruction,a detection method for the corrugation depth is developed,which is based on the extraction to the maximum/minimum value about the regression model of those segmented section subregions;a piecewise hybrid reconstruction method with the pattern of "straight line + curve" is proposed to realize the high-precision reconstruction to the cross-section contour,and the normal model analysis is used to obtain the thickness information of measured plate.The relative average deviation between the proposed method and the traditional method is 2.1%and 10% respectively,and the change trend of these comparison data shows a high consistency.In summary,in order to meet the requirement of the transformation from manual sampling to automatic inspection,the quantitative evaluation of corrugated plate based on point laser triangulation is studied in this paper.The research work has important engineering application value for realizing full inspection and testing of corrugated plate forming quality,improving product qualification and service reliability,and realizing intelligent quality inspection equipment for industrial complex parts.