The Inlet Flow Structure of a Centrifugal Compressor Stage and Its Influence on the Compressor Performance

Abstract

The performance of centrifugal compressors can be seriously degraded by inlet flow distortions that result from an unsatisfactory inlet configuration. In this present work, the flow is numerically simulated and the flow details are analyzed and discussed in order to understand the performance behavior of the compressor exposed to different inlet configurations. In a previous work, complementary to this present work, experimental tests were carried out for the comparison of a centrifugal compressor stage performance with two different inlet configurations: one of which was a straight pipe with constant cross-sectional area and the other a 90-deg curved pipe with nozzle shape. The comparative test results indicated significant compressor stage performance difference between the two different inlet configurations. Steady-state compressor stage simulation including the impeller and diffuser with three different inlets has been carried out to investigate the influence of each inlet type on the compressor performance. The three different inlet systems included a proposed and improved inlet model. The flow from the bend inlet is not axisymmetric in the circumferential and radial distortion, thus the diffuser and the impeller are modeled with fully 360-deg passages.

Optimization of the inlet air line of an automotive turbocharger

“…It is possible to consider the inlet distortions as the primary cause of the rotating stall phenomena as it is the main factor affecting the uniformity of the flow [4]. Surge and efficiency are known to be significantly influenced by the flow discharge characteristics on the impellers, which mainly depend on the behaviour of the airflow through the inducer [5]. Some distortions, evidenced in the flow, are caused by the elements that compose the inlet configuration line, inducing undesirable instabilities that reduce the compressor efficiency or produce compressor surge [6].…”

Experimental Investigation of a Forced-Response Condition in a Multistage Compressor

“…This is due to the fact that researchers may use different combinations of distortion, such as a combination of pressure and flow angle distortion, at different magnitudes and quantified through various means and averaging schemes. Engeda et al (2003) created inlet distortion using a 90-degree circular bend upstream of the compressor, as did Kim et al (2001), Kang et al (2012), and Engeda et al (2003). Zemp et al (2010) used different mesh screens to generate a lobed distortion patterns.…”

“…This is often a subject of concern when a significant bend, or change in flow direction exists. Engeda et al (2003) showed that flow angle distortion changes the incidence angle at the impeller inlet, causing efficiency loss and total pressure loss as well as vibrational problems, depending on the type and intensity of the distortion.…”

Numerical investigation on the effect of inlet acceleration on inlet flow distortion in a centrifugal fan

“…The results showed that the influence of inlet environment on the performance of the whole machine is very significant. Then on the basis of their own work, they added guide vanes in the bend, the results showed that the efficiency is improved by 3% [7].…”