Development and Validation of a Model for Centrifugal Compressors in Reversed Flow Regimes

Abstract

Turbochargers are widely used to help reduce the environmental impact of automotive engines. However, a limiting factor for turbochargers is compressor surge. Surge is an instability that induces pressure and flow oscillations that often damages the turbocharger and its installation. Most predictions of the surge limit are based on low-order models, such as the Moore-Greitzer model. These models tend to rely on a characteristic curve for the compressor created by extrapolating the constant speed lines of a steady-state compressor map into the negative mass flow region. However, there is little validation of these assumptions in the public literature. In this paper, we develop further the first-principles model for a compressor characteristic presented in Powers et al. [1], with a particular emphasis on reverse flow. We then perform experiments using a 58mm diameter centrifugal compressor provided by Cummins Turbo Technologies, where we feed air in the reverse direction though the compressor while the impeller is spinning in the forwards direction in order to obtain data in the negative mass flow region of the compressor map. This demonstrated experimentally that there is a stable operating region in the reverse flow regime. The recorded data showed a good match with the theoretical model developed in this paper. We also identified a change in characteristic behaviour as the impeller speed is increased which, to the authors knowledge, has not been observed in any previously published experimental work

Determination of a Numerical Surge Limit by Means of an Enhanced Greitzer Compressor Model

“…With a small B system, it was possible to operate the compressor to a mass flow rate of almost zero. In the years after, a few researchers were improving and applying the initial modeling approach and published the results for the scientific community [4][5][6][7][8][9][10]. Common to all of them is the fact that the compressor characteristic is modeled by a functional relationship.…”

Study of the Greitzer Model for Centrifugal Compressors: Variable Lc Parameter and Two Types of Surge

“…The most common method of compressor performance curve approximation used in the literature is the third order polynomial [5,16,[26][27][28] presented in Figure 2 and Equation (1). [29].…”

“…All unstable points are denoted with triangles. Positioning of those points is a matter of discussion [29] as the machine operates along the open cycle in this regime [2]. In this plot their position is determined by the average value of pressure oscillations and by the mass flow calculated from the measured dynamic pressure profile in the outlet pipe.…”