Investigation Of Non-axisymmetric Flow Behaviors In Centrifugal Compressor Under Inlet Distortion

Centrifugal compressor as an important part of small aircraft engine and the recycling turbocharger, is widely used in industry, agriculture and other industries. Centrifugal compressor in use process, on the one hand, because of its downstream adopt spiral case with circumferential asymmetry geometric structure, will cause the volute and compressor internal flow field changes, with a circumferential non-uniformity, which led to the decrease of the working performance of the compressor, on the other hand, the bent pipes are usually adopted in the intake inlets of the vehicle turbocharger centrifugal compressors due to the limitation of the arrangement of the engine. Air flowing through the pipe, under the action of centrifugal force and viscous force will cause the compressor inlet flow field in complex total pressure and swirl distortion. The compressor performance and stability of the scope of work have a significant impact.Based on this, this article adopts the method of experiment and numerical simulation, to a certain type of turbocharger on the use of centrifugal compressor as the research object, has carried out the axisymmetric centrifugal compressor internal flow characteristics and 180 ° bend and a centrifugal compressor volute coupling under the action of the centrifugal compressor performance and internal flow characteristics of research work. The results show that the compressor shroud static pressure distributions in the circumferential direction keep with the same characteristics of axisymmetric distortion form in volute. In the process of reverse transmission of downstream flow field distortion to the upstream, its impact on the upstream is gradually wakening. When shroud circumferential high pressure zone of the impeller outlet spreads to the impeller inlet, it exists phase difference with the impeller outlet high circumferential position. Under different mass conditions, the static pressure’s non-uniform distribution leads to the differences of the circumferential distribution of the blade tip leakage flow. Under the small mass-flow condition, the leakage flow decreases firstly, increases then and decreases again; Under the large mass-flow condition, the leakage flow increases firstly and then keeps the continuous decreases. Besides, the flow field distortion area at the bent pipe outlet will vary with the change of the relative circumferential position bent pipe and asymmetric structure of the volute. This changes the coupling effect of distortion flow field of the impeller outlet and varies the compressor performance. The interaction of these two kinds of distortion flow fields will affect the circumferential uniformity of the impeller internal flow field. When the low static pressure area at the bent pipe outlet and the high static pressure at impeller export act on the same blade channel outlet region, the flow field distributions in the impeller internal is the most uneven, in this case, the compressor performance is lower than that of the other bent pipe installation angle. In order to ensure the performance degradation degree of the centrifugal compressor is small after the installation of the bent pipe, the high static pressure of the bent pipe outlet and the high static pressure of the impeller outlet should be act on the same blade channel. Based on this principle, the installation circumferential position range of the bent pipe for the small efficiency drop of the compressor is determined.