Water turbine blade blank profile measuring and machining allowance analyzing method

Abstract

The invention relates to a water turbine blade blank profile measuring and machining allowance analyzing method capable of effectively solving the problem of water turbine blade blank profile measurement and machining allowance analysis to ensure the manufacturing quality and precision of the water turbine blades, comprising the following technical solutions: measuring the blade blanks by using a digital close range photogrammetry to obtain the measuring point cloud data shapes of the blank profiles consequently, aligning a measuring coordinate system where the measuring point clouds are located to a design coordinate system where a CAD design model is located, establishing a differential relation of free-form surface parameters with respect to rigid rotation parameters by using an analytic method derived by the multivariate of Newton iteration method to obtain a Jacobian matrix and Hessian matrix which are available for a target equation; then performing the numerical optimization calculation based on the LM method and Newton iteration method, and performing report or graphical output and print on the result. The inventive method is scientific, advanced, stable and reliable, and has high accuracy, thereby ensuring the hydraulic stability, production efficiency and cavitation property, and bringing enormous economic and social benefits.

Description

1. Technical field [0001] The invention relates to a method for measuring the profile of a water turbine blade blank and analyzing a machining allowance. 2. Background technology [0002] The manufacturing quality and precision of turbine blades are directly related to the hydraulic stability, efficiency and cavitation performance of the generating set. Due to the complex shape of the blade, there are many parameters to describe, and the profile lines of each section from the blade tip to the blade root are different, and the difference is relatively large. The measurement of the blade profile is much more complicated than the shape measurement of those simple parameter workpieces. The traditional manufacturing of turbine blades adopts the process of "sand casting-three-dimensional sample inspection-manual shovel grinding". However, due to the disadvantages of poor rigidity, easy deformation, and high cost, the three-dimensional sample has become increasingly unable to meet...

AI Technical Summary

Problems solved by technology

[0004] At present, there are mainly the following methods for blade blank measurement: one is the three-coordinate machine measurement method, and its main disadvantages are the harsh requirements for the use environment, poor applicability of on-site measurement at the production site, and it is difficult to apply to large-scale blade measurement; the other is three-dimensional planning. The main disadvantage is that it needs a special measuring platform, it is a contact measurement, and it is only suitable for the measurement of small and medium-sized leaves; the third is the photoelectric theodolite measurement, articulated arm measurement or laser tracking measurement method. The main disadvantages are that the equipment cost is high, Complicated to use and less efficient for measuring large blades

[0005] At present, the methods of blade blank machining allowance analysis are divided into two types according to the alignment of the coordinate system between the measurement data model and the CAD design model: one is to use a step-by-step iterative search method for alignment, and its main disadvantage is that iterative Many times, slow convergence speed, high requirements for the initial value, and not the theoretical optimal solution, etc.; the second is to use the iterative closest point (ICP) method and its improved version to align the coordinate system, and its main disadvantage is poor calculation robustness, different The calculation result of the initial value of may be inconsistent

Images