RUDN Journal of Engineering ResearchRUDN Journal of Engineering Research2312-81432312-8151Peoples’ Friendship University of Russia named after Patrice Lumumba (RUDN University)1732910.22363/2312-8143-2017-18-3-299-307Research ArticleCAD OF TURBINE PROFILE TYPE A3K7 NACA BY THE METHOD OF NONLINEAR TRANSFORMATIONVinogradovL V<p>Vinogradov Leonid Valerievich, Candidate of Technical Sciences, assistant professor of the Department of technology of mechanical engineering, machine tools and instruments at the Academy of Engineering of the Peoples’ Friendship University of Russia. Research interests: computer aided design systems, turbines and turbo machinery.</p>vinogradov_lv@rudn.universityMamaevV K<p>Mamaev Vladimir Konstantinovich, senior professor of the the Department of technology of mechanical engineering, machine tools and instruments at the Academy of Engineering of the Peoples’ Friendship University of Russia. Research interests: computer aided design systems, turbines, acoustic and wave processes.</p>mamaev_vk@rudn.universityOschepkovP P<p>Oshchepkov Petr Platonovich, Candidate of Technical Sciences, assistant professor of the Department of technology of mechanical engineering, machine tools and instruments at the Academy of Engineering of the Peoples’ Friendship University of Russia. Research interests: computer aided design systems, internal combustion engines operation, alternative fuels.</p>oshchepkov_pp@rudn.universityPeoples’ Friendship University of Russia1512201718329930721112017Copyright © 2017, Vinogradov L.V., Mamaev V.K., Oschepkov P.P.2017<p>The paper presents the results of designing a turbine profile type A3K7 NACA using CAD, which realizes the method of nonlinear transformation. Girst transformation was used by the authors. All calculations and graphical representations were made in the computer algebra system Mathcad. For the calculation and graphical representations the middle line, defined by coordinates, is approximated with two linear segments in the regions of the leading and tailing edges with specified angles and three nonlinear segments in the form of second order Bezier curves. The coordinates of the matching points of neighbor sections are calculated using an iterative method with an optimization of the correlation index. The coordinate of the bending point was found using the condition of equality to zero of the second derivative of the interpolative contour. The coordinates of the junction point of the leading edge are determined in the paper as ab arc and a series of points of the contour, approximated by a second order Bezier curve. After determining the first and last point of the second order Bezier curve, the coordinated of the middle point on the intersection of tangential lines that start at the first and last point of the curve. After the approximation of three sections with second order Bezier curves the integral function of the blade back (convex side of the contour) of the profile A3K7 considering the leading and tailing edges are made as arcs.</p>turbinecomputer-aided designnonlinear transformationтурбинапрофильСАПРнелинейные преобразования[Holshevnikov K.V. Theory and calculation of aircraft impeller machine. M.: Engineering, 1970. 610 p.][Horlock J.H. Axial flow turbine (gas dynamics). M.: Mashinostroenie, 1972. 208 p.][Ivanov G.S. Designing of technical surfaces (mathematical modelling on the basis of nonlinear transformations). M.: Mashinostroenie, 1987. 192 p.][Statistical methods for processing of empirical data. Recommendations VNIINMASH. M.: Publishing House of standards, 1978. 230 p.][Gusakov S.V., Patrahaltsev N.N. Planning, conducting and data processing of experimental researches of internal combustion engines: Textbook. allowance. M.: publishing house of PFUR, 2004. 167 p.]