A Computational Fluid Dynamic Method for Rotating Stall in a Single Stage Axial Compressor PDF Download

Author: Philip L. Andrew
Publisher:
ISBN:
Category : Compressors
Languages : en
Pages : 140

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Author: Farzad Ashrafi
Publisher:
ISBN: 9781321613261
Category :
Languages : en
Pages : 106

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Book Description
Rotating stall is a well-known aerodynamic instability in compressors that limits the operating envelope of aircraft gas turbine engines. An innovative method for suppressing the most common form of rotating stall inception using an annular DBD plasma actuator had been proposed. A DBD plasma actuator is a simple solid-state device that converts electricity directly into flow acceleration through partial air ionization. However, the proposed concept had only been preliminarily evaluated with simple numerical simulations on an isolated axial rotor using a relatively basic CFD code. The current project provides both an experimental and a numerical assessment of this concept for an axial compressor stage as well as centrifugal compressor stage that are both part of a low-speed two-stage axial-centrifugal compressor test rig. The two configuration studied are the two-stage configuration with a 100 mN/m annular casing plasma actuator placed just upstream of the axial rotor leading edge, and the single-stage centrifugal compressor with the same actuator placed upstream of the impeller leading edge. The tested configuration were simulated with a sophisticated commercial RANS CFD code (ANSYS CFX) in which was implemented the latest engineering DBD plasma model and dynamic throttle boundary condition, using single-passage multiple blade row computational domains. The experiments show that the casing plasma actuator reduces the mass flow of the last stable point (stall point) by 19.28% for the axial compressor stage and 28.39% for the centrifugal compressor stage for which the impeller is the source of rotating stall. The CFD simulations indicate that in both types of compressors the actuator delays the stall inception by pushing the incoming/tip clearance flow interface downstream into the blade passage. In each case, the predicted percentage reduction in stalling mass flow matches the experimental value reasonably well. However, the CFD simulations over-predicts the mass flow of the stall point as well as the pressure rise of the centrifugal stage and under-predict the pressure rise of the axial stage. The main factors for the difference are likely slight discrepancies between the simulated and actual axial rotor blade geometry deformation and the inability of the simulation tool to accurately capture the total pressure loss in the hub region of the vaneless diffuser.

Author: Wade H. Shafer
Publisher: Springer Science & Business Media
ISBN: 1461573882
Category : Science
Languages : en
Pages : 414

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Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, SIld disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna and broader dissemination. tional publishing house to assure improved service Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 30 (thesis year 1985) a total of 12,400 theses titles from 26 Canadian and 186 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work.

Author: Gregory Paul Herrick
Publisher:
ISBN:
Category : Axial flow compressors
Languages : en
Pages :

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The quest to accurately capture flow phenomena with length-scales both short and long and to accurately represent complex flow phenomena within disparately sized geometry inspires a need for an efficient, high-fidelity, multi-block structured computational fluid dynamics (CFD) parallel computational scheme. This research presents and demonstrates a more efficient computational method by which to perform multi-block structured CFD parallel computational simulations, thus facilitating higher-fidelity solutions of complicated geometries (due to the inclusion of grids for "small" flow areas which are often merely modeled) and their associated flows. This computational framework offers greater flexibility and user-control in allocating the resource balance between process count and wallclock computation time. The principal modifications implemented in this revision consist of a "multiple grid-block per processing core" software infrastructure and an analytic computation of viscous flux Jacobians. The development of this scheme is largely motivated by the desire to simulate axial compressor stall inception with more complete gridding of the flow passages (including rotor tip clearance regions) than has been previously done while maintaining high computational efficiency (i.e., minimal consumption of computational resources), and thus this paradigm shall be demonstrated with an examination of instability in a transonic axial compressor. However, the paradigm presented herein facilitates CFD simulation of myriad previously impractical geometries and flows and is not limited to detailed analyses of axial compressor flows. While the simulations presented herein were technically possible under the previous structure of the subject software, they were much less computationally efficient and thus not pragmatically feasible; the previous research using this software to perform three-dimensional, full-annulus, time-accurate, unsteady, full-stage (with sliding-interface) simulations of rotating stall inception in axial compressors utilized tip clearance periodic models, while the scheme here is demonstrated by a simulation of axial compressor stall inception utilizing gridded rotor tip clearance regions. As will be discussed, much previous research --- experimental, theoretical, and computational --- has suggested that understanding clearance flow behavior is critical to understanding stall inception, and previous computational research efforts which have used tip clearance models have begged the question, "What about the clearance flows?". This research begins to address that question.

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781719380119
Category :
Languages : en
Pages : 36

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This paper describes a method to estimate key aerodynamic parameters of single and multistage axial and centrifugal compressors. This mean-line compressor code COMDES provides the capability of sizing single and multistage compressors quickly during the conceptual design process. Based on the compressible fluid flow equations and the Euler equation, the code can estimate rotor inlet and exit blade angles when run in the design mode. The design point rotor efficiency and stator losses are inputs to the code, and are modeled at off design. When run in the off-design analysis mode, it can be used to generate performance maps based on simple models for losses due to rotor incidence and inlet guide vane reset angle. The code can provide an improved understanding of basic aerodynamic parameters such as diffusion factor, loading levels and incidence, when matching multistage compressor blade rows at design and at part-speed operation. Rotor loading levels and relative velocity ratio are correlated to the onset of compressor surge. NASA Stage 37 and the three-stage NASA 74-A axial compressors were analyzed and the results compared to test data. The code has been used to generate the performance map for the NASA 76-B three-stage axial compressor featuring variable geometry. The compressor stages were aerodynamically matched at off-design speeds by adjusting the variable inlet guide vane and variable stator geometry angles to control the rotor diffusion factor and incidence angles. Veres, Joseph P. Glenn Research Center TURBOCOMPRESSORS; FLUID FLOW; COMPUTATIONAL FLUID DYNAMICS; COMPRESSIBLE FLUIDS; DESIGN ANALYSIS; GUIDE VANES; CENTRIFUGAL COMPRESSORS; SURGES; DIFFUSION; ROTORS; STATORS

Author: Jaideep Sahai Mathur
Publisher:
ISBN:
Category : Compressibility
Languages : en
Pages : 150

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Author: Massachusetts Institute of Technology. Gas Turbine Laboratory
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 31

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Author: Shashank Mishra
Publisher:
ISBN:
Category :
Languages : en
Pages : 149

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Book Description
The incompressible flow equations are function of the pressure gradients and not the pressure. The most important issue in solution of flow equations of incompressible fluid is the pressure gradient vector which is appearing as a source term in the momentum equation, but does not have any obvious equation coupling it with other dependent variables. Accurate numerical solutions are obtained for the incompressible Navier Stokes equations in primitive variables. Explicit finite difference scheme computer code is developed to solve incompressible flow equations. In this study, consistent with the physics of incompressible flows, the velocity and pressure gradient vectors are considered as the dependent variables. In this case, that satisfies continuity equation to machine zero, the pressure gradient vector increases the number of dependent variables which requires additional equations to close the system of governing equations. Additional equations are obtained by reformulating the continuity equation and adding a time derivative term for the pressure gradient. Upon, convergence of the numerical solution, the continuity equation will be satisfied to an arbitrary constant. To enforce that constant to be zero, the continuity equation is set to be zero on the boundary of the solution domain. It is important to note that the curl of the reformulated continuity equation automatically satisfies the curl of the pressure gradient identity. This scheme is applicable for two and three dimensions, inviscid and viscous flows. Multistage axial compressor has an advantage of lower stage loading as compared to a single stage. Several stages with low pressure ratio are linked together which allows for multiplication of pressure to generate high pressure ratio in an axial compressor. Since each stage has low pressure ratio they operate at a higher efficiency and the efficiency of multi-stage axial compressor as a whole is very high. Although, single stage centrifugal compressor has higher pressure ratio compared with an axial compressor but multistage centrifugal compressors are not as efficient because the flow has to be turned from radial at outlet to axial at inlet for each stage. The present study explores the advantages of extending the axial compressor efficient flow path that consist of rotor stator stages to the centrifugal compressor stage. In this invention, two rotating rows of blades are mounted on the same impeller disk, separated by a stator blade row attached to the casing. A certain amount of turning can be achieved through a single stage centrifugal compressor before flow starts separating, thus dividing it into multiple stages would be advantageous as it would allow for more flow turning. Flow characteristics of the novel multistage design are compared with a single stage centrifugal compressor. The flow path of the baseline and multi-stage compressor are created using 3DBGB tool and DAKOTA is used to optimize the performance of baseline as well novel design. The optimization techniques used are Genetic algorithm followed by Numerical Gradient method. The multi-stage compressor is more efficient with a higher pressure ratio compared with the base line design for the same work input and initial conditions.

Author: Robert W. Graham
Publisher:
ISBN:
Category : Axial flow compressors
Languages : en
Pages : 30

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Author: Bjørn H. Hjertager
Publisher: MDPI
ISBN: 3039281127
Category : Technology & Engineering
Languages : en
Pages : 256

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Book Description
“Engineering Fluid Dynamics 2018”. The topic of engineering fluid dynamics includes both experimental as well as computational studies. Of special interest were submissions from the fields of mechanical, chemical, marine, safety, and energy engineering. We welcomed both original research articles as well as review articles. After one year, 28 papers were submitted and 14 were accepted for publication. The average processing time was 37.91 days. The authors had the following geographical distribution: China (9); Korea (3); Spain (1); and India (1). Papers covered a wide range of topics, including analysis of fans, turbines, fires in tunnels, vortex generators, deep sea mining, as well as pumps.