Research On System Of 3D Surface Temperature Field Reconstruction For Engine Component

At present,temperature sensitive paint temperature measurement technology has been widely used to measure the temperature distribution of the wall surface of aeroengine hot end components.However,most of the temperature sensitive paint temperature sensing systems are based on two-dimensional images,these can not intuitively reflect the surface temperature field of the whole target to be measured.Therefore,this thesis will focus on the temperature sensing technology based on three-dimensional information,combine with three-dimensional reconstruction technology and temperature measurement method of temperature sensitive paint,design and develop a three-dimensional surface temperature field reconstruction system for engine components that displays surface temperature information of engine components in three-dimensional temperature field.The main work of this thesis is reflected as follows:(1)Research on three-dimensional measurement methods of engine components.In order to obtain the point cloud information of the engine components,and considering that the system requires high precision of reconstruction,this thesis has adopted the three-dimensional reconstruction method based on structured light under binocular vision.First,a set of designed gray code coding patterns are projected onto the surface of the object to be measured by the projector,and the images are acquired simultaneously by the binocular camera.Then,the acquired images are decoded to obtain a matching relationship between the left and right images.Finally,combined with the internal and external parameters of the camera obtained by Zhang Zhengyou’s camera calibration method,the three-dimensional coordinate values of the engine components are calculated by the triangulation method,thereby realizing the three-dimensional measurement of the engine components.The experimental results show that the method can obtain accurate three-dimensional coordinate information of the surface of the engine component.(2)Research on the method of acquiring the complete surface point cloud of engine components.A method for acquiring the integral point cloud of the engine component surface has been proposed by using the three-dimensional measurement method based on structured light.The method is divided into two stages: point cloud registration and point cloud refinement.In the point cloud registration phase,the align of multi-angle point cloud data is completed by manually selecting corresponding points.In the phase of point cloud refinement,a point cloud refinement algorithm with gray features preserving is proposed to solve the problems of redundancy of the registered point cloud data and uneven distribution between thickness and spacing.First,the voxel grid method is used to downsample the registered point cloud to remove redundant data.Then,the point cloud is resampled by the improved weighted locally optimal projection algorithm to generate the point cloud data with the original shape feature and uniform distribution.Finally,searching the nearest neighbor point of the resample point in the registered point cloud data by using kd-tree method,and then mapping the gray information of the nearest neighbor point to the coordinate position of the resampled point.The experimental results show that the method can obtain a complete point cloud of the engine component surface.(3)Design of a three-dimensional temperature field reconstruction system for engine component surfaces.Aiming at the requirements in function,performance and operation to the three-dimensional temperature interpretation of engine components,combining with practical function analysis,a three-dimensional surface temperature field reconstruction system for engine components has been designed.The system is mainly composed of three modules: 3D reconstruction module,point cloud data processing module and temperature automatic interpretation module.The 3D reconstruction module is used to realize camera calibration and three-dimensional measurement of engine components.The point cloud data processing module is used to obtain complete surface of components.The temperature automatic interpretation module provides three ways of user interaction for three-dimensional temperature interpretation.Finally,the system is simulated by the engine flame tube.The test results show that the performance of this system is stable,the reconstruction accuracy is high and the error is less than 0.5mm,the interpretation temperature is correct,and the temperature error is controlled within 5 degrees Celsius.