Accurate determination of acousto-elastic natural frequencies in centrifugal compressors is important in order to avoid resonance events that may lead to machine failure. Compressors operating with CO2 at high pressures, especially near its transition to supercritical state, deal with a wide variation in density and speed of sound. Natural frequency behavior under these conditions is studied here. A finite element method (FEM) based coupled acousto-elastic solver has been developed to study the modal coupling and interactions between the impeller and the side-cavity modes for an idealized compressor geometry. Pressure in the side-cavities is increased up to a very high value of 20 MPa and existence of fluid-A nd structure-dominant acousto-elastic modes is observed. The variation of the natural frequencies of these modes with pressure exhibits contrasting trends as CO2 transitions from gaseous to supercritical state. © 2017 by ASME.

Sunetra Sarkar

Department of Aerospace Engineering

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Acousto-Elastic Interactions in High-Pressure CO2 Centrifugal Compressors

Journal of Vibration and Acoustics, Transactions of the ASME

Conventional acousto-elastic interaction studies on centrifugal compressors generally ignore the dissipative effects of visco-thermal phenomena present in all acoustic fluids. This work presents a numerically efficient framework for solving acousto-elastic problems, while taking visco-thermal effects into consideration, in centrifugal compressor-like geometries in the frequency domain. Compared to conventional acousto-elastic analyses, the framework enables the computation of a more realistic estimate of the frequency response of a centrifugal compressor. The acoustic fluid is modelled using Boundary Layer Impedance (BLI) model which accounts for dissipative visco-thermal effects through an impedance-like boundary condition. An improved finite element implementation is presented which reduces the computational time of the BLI acousto-elastic model to almost half, while not compromising on accuracy. To further reduce the computational cost, a Krylov subspace based reduced order model (ROM) is developed and implemented in the analysis. The ROM is specifically designed to handle frequency dependent system matrices encountered in the BLI acousto-elastic analysis. © 2018 Elsevier Ltd

Journal of Fluids and Structures

Boundary Layer Impedance model to analyse the visco-thermal acousto-elastic interactions in centrifugal compressors

This study focusses on developing a novel reduced order model for dynamic analysis of an acousto-elastic system, such as an impeller housed in a pressurised incompressible fluid filled chamber. Resolving the coupled dynamics of such systems require high-fidelity numerical models for both the structure and the fluid and are typically modelled using finite elements (FE) leading to FE equations with large ordered asymmetric matrices. The parameters for the system are obtained from measurements which are susceptible to uncertain errors and biases. This study proposes the development of a stochastic reduced order FE model based on integrating arbitrary PCE with SEREP. Numerical results reveal that the proposed method results in significant reduction in computational costs for dynamic analysis without compromising on accuracy. The reduced order model is shown to be useful for proper orthogonality check for quantifying the degree of correlation between experimentally observed and model based modes. © 2018 Elsevier Ltd

Probabilistic Engineering Mechanics

Reduced order modelling in stochastically parametered acousto-elastic system using arbitrary PCE based SEREP

Volume 7A: Structures and Dynamics

Experimental Investigation of Fluid Structure Interaction of Impeller Like Disks in Super Critical Carbon Dioxide

Sealing Technology

Turbomachinery and pump symposia take place in September

Journal of Turbomachinery

Natural Frequency Shift in a Centrifugal Compressor Impeller for High-Density Gas Applications

Communications in Computational Physics

Numerical Methods for Fluid-Structure Interaction — A Review

Computer Methods in Applied Mechanics and Engineering

Treatment of acoustic fluid–structure interaction by localized Lagrange multipliers and comparison to alternative interface-coupling methods

Journal	Journal of Vibration and Acoustics, Transactions of the ASME
Publisher	American Society of Mechanical Engineers (ASME)
ISSN	10489002
Open Access	No