Simulation and Optimization of the Nozzle Section Geometry for a Suspension Abrasive Water Jet

In order to improve the life cycle and cutting ability of a suspension abrasive water jet nozzle at the same time, hydrodynamics technology, an enumeration method and multiparameter orthogonal optimization are used to optimize the nozzle section geometry, taking the inlet diameter coefficient of the nozzle, the axial length coefficient of the contraction section and the contraction section curve as optimization variables, and selecting the peak velocity and the unit flow erosion rate as the indicators, it is concluded that the optimal contraction section curve is a Widosinski curve, the optimal inlet diameter coefficient of the nozzle is 0.333 and the optimal axial length coefficient of the contraction section is 2.857. Compared with the commercial product single cone nozzle, the performance of the optimal section nozzle improves by 5.64% and the life cycle increases by 43.2%. On this basis, the effects of operating parameters, including inlet pressure, abrasive particle flow rate and abrasive particle size, are further studied. It is determined that the optimal section nozzle has the best performance under the above operating parameters. It is demonstrated that by optimizing the nozzle section geometry, the cutting capacity and life cycle of the nozzle are improved, the performance of the nozzle can be significantly improved and the optimization of the performance of the nozzle is realized.

Classification of young males’ shoulder shapes based on cross-sectional morphological characteristics

This paper focused on the different characteristics of the shoulder cross-section curves closely related to the shape to subdivide the shoulder shapes. In this paper, 213 young college male students aged 18-26 were selected to measure the shoulder data with three-dimensional body scanner. With the help of imageware12.0 and matlabr2012b software, the cross-section curves which could be used to classify the shoulder shapes were extracted, and the method of subdividing the shoulder shapes with the curvature radius of the characteristic points of the cross-section curve and the ratio of sagittal to frontal diameter was established. K-means clustering method was used through dynamic clustering, the optimal classification number of shoulder shapes was determined to be 4 categories by variance analysis, and the shape differences of each shoulder shape were quantified; by comparing the curve shape of shoulder section, the curve change characteristics of 4 categories of shoulder section were further qualitatively described.

Research of particle movement on rough surface formed by screw movement of sinusoid under action of own weight

The differential equations of particle movement on a rough surface which is formed by the helical motion of a sinusoid under the action of the force of own weight were obtained in the article. The sinusoid is the axial cross-section curve of the helical surface and is located in the vertical plane. The obtained equations were solved by numerical methods and the trajectories of the particle on the helical surface were constructed. In addition, graphs of the change in the particle velocity and its distance from the axis of the surface were found, as a result of which the conditions when stabilization of the particle movement is possible were found. It is shown that in the general case, as a result of acceleration, the particle moves away from the axis of the surface and stops in one of its gutters. The depth and density of the gutters are controlled by changing the constant coefficients parameters. Also, a partial case at zero depths of the gutter, when the sinusoid turns into a straight line and the particle moves on the surface of the helical conoid, were considered.

An approximation of geodesic circle passing through three points on an ellipsoid

In this paper we present an approximation method for a geodesic circle passing through three points on an oblate ellipsoid. Our method uses a prolate ellipsoid passing through the three points, and the new approximation curve is the intersection of the oblate and prolate ellipsoids, which can be obtained algebraically without iterations. The advantage of our approximation method is that it yields a significantly smaller approximation error. Compared to the plane section curve passing through the three points on the oblate ellipse, our method reduces the approximation error by at least 98\hspace{0.1667em}\% when the radii of geodesic circles are 100 km∼1000 km on the surface of the Earth. We illustrate the results using numerical examples.

Bionic Design for Reducing Adhesive Resistance of the Ridger Inspired by a Boar’s Head

The main feature of the boar’s head used to root around for food is the front part, which is similar to the ridger in terms of function, load, and environment. In this paper, the boar’s head was selected as the biological prototype for developing a new ridger. The point cloud of the head was captured by a 3D scanner, and then, the head surface was reconstructed using 3D coordinates. The characteristic curves of the front part of the boar’s head were extracted, and then, five cross-sectional curves and one vertical section curve were fitted. Based on the fitted curves, five kinds of bionic ridgers were designed. The penetrating resistances of the bionic ridgers and traditional ridger were tested at different speeds in an indoor soil bin. The test results showed that bionic ridger B had the best penetrating resistance reduction ratio of 16.67% at 4.2 km/h velocity. In order to further evaluate the performance of the best bionic ridger (bionic ridger B), both the bionic ridger and traditional ridger were tested in a field under the same working conditions. The field results indicate that the bionic ridger reduces penetrating resistance by 6.91% compared to the traditional ridger, and the test results validate that the bionic ridger has an effect on reducing penetrating resistance.

Matching Algorithm for Profile Error Calculation of Blade Surface

The blade is one of the key part of aero engine because its shape precision and surface quality significantly influence the performance, efficiency and reliability of the engine. The blade surface is generally obtained by precision finishing process, which is a repeated work of profile error measurement, profile error calculation and error correction manufacturing. For profile error calculation, the matching of measurement points and ideal blade surface must be firstly performed. However there is few detailed work reported on matching algorithm. In this paper, a new matching algorithm for profile error calculation was proposed. Firstly, the coarse matching method based on characteristics of blade section curves between measurement points and its corresponding ideal section curve was studied. Then the Sigular Value Decomposition (SVD)-Iterative Closest Point (ICP) precision matching method was adopted to improve the matching precision. After that, the weight calculation method was applied to balance the profile errors among different section curves. Simulation work was performed to validate the proposed matching algorithm. Results shows that micrometer-order matching accuracy of the blade section curves could be obtained through the above-mentioned three matching steps.

Design Method and Performance Effects of Curvature-Smooth Centrifugal Compressor Blades

Blade curvature has an important effect on the pressure distribution over the blade surface as well as the quality of airfoil machining, but curvature smoothing method in design environments is little studied. A new geometry generator is developed for the design of curvature-smooth airfoils. The sections of an airfoil can be initially designed by a conventional method, and each of the sections is then regenerated by fitting a fifth order B-spline curve. The first order differential of the curvature with respect to arc length of the blade surface is used as a curvature smoothness measure. The distance between discrete points and the curve, and the integral of the square of the first derivative along the streamwise section curve are simultaneously minimized in the fitting process. The design of a transonic centrifugal compressor for turbocharger application is presented to study the effects of the curvature-smooth blade on centrifugal compressor performance. A numerical study was carried out and the results are discussed.

Virtual remanufacturing: Cross-section curve reconstruction for repairing a tip-defective blade

Remanufacturing of damaged blades has been widely discussed in the field related with aero maintenance. Cross-section curve is the key factor for rebuilding 3D airfoil of a damaged blade. This paper focuses on how to reconstruct the cross-section curves of a tip-defective blade. The difficulty in the reconstruction of the cross-section curve is in broken region, where some data points are absent. In this paper, a method for reconstructing the cross-section curve in small-scale broken region of the blade tip is proposed. This method involves 3D noncontact digitization, methodology of obtaining the cross-section plane, cross-section curve reconstruction of the unbroken region, and cross-section curve deduction of the broken region. At last, an error analysis is carried out so as to indicate that the proposed method is appropriate for reconstructing the cross-section curve of the small-scale broken blade tip.