Effect of Exit Pressure Pulsation on the Performance and Stability Limit of a Turbocharger Centrifugal Compressor

Abstract

It is well known that compressor surge imposes a significant limit on the flow range of a turbocharged internal combustion engine. The centrifugal compressor is commonly placed upstream of the inlet manifold, and hence, it is exposed to the intermittent flow regime of the inlet valves. Surge phenomena have been well studied over the past decades, and there still remains limited information with regard to the unsteady impact caused by the inlet valves. This study presents an experimental evaluation of such a situation. Engine representative pulses are created by a downstream system comprising a large volume, two rotating valves, a throttle valve, and the corresponding pipe network. Different pulsation levels are characterized by means of their frequency and the corresponding amplitude at the compressor inlet. The stability limit of the system under study is evaluated with reference to the parameter B proposed by Greitzer (1976, “Surge and Rotating Stall in Axial Flow Compressors—Part II: Experimental Results and Comparison With Theory,” ASME J. Eng. Power, 98(2), pp. 199–211; 1976, “Surge and Rotating Stall in Axial Flow Compressors—Part I: Theoretical Compression System Model,” ASME J. Eng. Power, 98(2), pp. 190–198). B describes the dynamics of the compression system in terms of volume, area, equivalent length, and compressor tip speed as well as the Helmholtz frequency of the system. For a given compressor, as B goes beyond a critical value, the system will exhibit surge as the result of the flow instability progression. The reduced frequency analysis shows that the scroll diffuser operates in an unsteady regime, while the impeller is nearly quasi-steady. In the vicinity of the surge point, under a pulsating flow, the instantaneous operation of the compressor showed significant excursions into the unstable side of the surge line. Furthermore, it has been found that the presence of a volume in the system has the greatest effect on the surge margin of the compressor under the unsteady conditions.

Influence of pressure pulsation on the performance of compression system and turbocharged engine

“…Marelli et al 10,11 used the Variable Valve Actuation (VVA) system to generate pressure waves resembling that in real engines.It is found that a hysteresis loop is formed and the compressor surge boundary will shift during the transients. Barrera-Medrano et al 12 adopted a rotary valve to simulate the pressure pulsation,similar results are found that the compressor operating point can go beyond the surge boundary. Galindo et al 13 investigated the influence of different pipeline designs at the compressor downstream.Results indicate that the pressure pulsation amplitude is greatly dependent on the pipe length.…”

Experimental study on performance of centrifugal compressor exposed to pulsating backpressure

“…Galindo et.al [17] shows in the experiment that remarkable improvement of surge margin up to 15% can be achieved by the pulsating backpressure depending on the rotational speed of the compressor. Barrera-Medrano et.al [18] further demonstrates that the influence is also coupled with the volume of pipes at compressor exit.…”

Improving Centrifugal Compressor Performance by Optimizing the Design of Impellers Using Genetic Algorithm and Computational Fluid Dynamics Methods

“…Moreover, [19] specified certain parameters for the objective function, including pressure ratio, efficiency and thrust, and changed the impeller profile from the hub to shroud, resulting in incredible improvements, including an efficiency increase of 4.5% and a pressure ratio increase of 16%. Investigating the effect of exit pressure pulsation on the performance and stability limit of a turbocharger centrifugal compressor, [20] showed that the presence of a volume in the system exerts the most significant effect on the surge margin of the compressor under unsteady conditions. Optimizing the aerodynamic design of the impellers of a centrifugal compressor using an inverse method based on the meridional viscous flow analysis [21] resulted in performance improvements and suppression of flow separations on the suction surfaces in the optimal design cases.…”