{"id":1066,"date":"2020-09-16T11:54:54","date_gmt":"2020-09-16T09:54:54","guid":{"rendered":"https:\/\/www.lfm.polimi.it\/?page_id=1066"},"modified":"2020-10-20T17:35:56","modified_gmt":"2020-10-20T15:35:56","slug":"impeller-diffuser","status":"publish","type":"page","link":"https:\/\/www.lfm.polimi.it\/?page_id=1066","title":{"rendered":"Impeller-Vaned Diffuser interaction"},"content":{"rendered":"
\n\t\t\t\t\t\t\t

\n\t\t\t\t\t\tImpeller \u2013 Vaned Diffuser Interaction In A Centrifugal Compressor\t\t\t\t\t\t<\/h4>\n\t\t\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t

\n\t\t\t\t\t\tTest At Design and Off Design Conditions\t\t\t\t\t\t<\/h1>\n\t\t\t\t\t\t<\/div>\n<\/div><\/div><\/div><\/div><\/div>
<\/div>
\t\t\t\t
\n\t\t\t\t\t\t\t
  • \n\t\t\t\t\t\t
    \n\t\t\t\t
    \n\t\t\t\t\t\t\t\t\t\t
    \n\t\t\t\t\t\t\"\"\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\t<\/li>\n\t\t\t\t
  • \n\t\t\t\t\t\t
    \n\t\t\t\t
    \n\t\t\t\t\t\t\t\t\t\t
    \n\t\t\t\t\t\t\"\"\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\t<\/li>\n\t\t\t\t
  • \n\t\t\t\t\t\t
    \n\t\t\t\t
    \n\t\t\t\t\t\t\t\t\t\t
    \n\t\t\t\t\t\t\"\"\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\t<\/li>\n\t\t<\/ul>\t\t\t\t
      \n\t\t\t\t\t\t\t\t\t\t\t
    1. <\/a><\/li>\n\t\t\t\t\t\t\t\t\t\t\t
    2. <\/a><\/li>\n\t\t\t\t\t\t\t\t\t\t\t
    3. <\/a><\/li>\n\t\t\t\t\t\t\t\t\t<\/ol>\n\n\t\t\t\t
      \n\t\t\t\t\t\n\t\t\t\t\t\t<\/em>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\n\t\t\t\t
      \n\t\t\t\t\t\n\t\t\t\t\t\t<\/em>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div><\/div><\/div><\/div>
      <\/div><\/div><\/div>
      <\/div>
      \n
      \n\t

      The experimental work was performed at the LFM of Energy Dept. of the Politecnico di Milano, on a closed loop test rig for compressors and turbines. The test campaign was carried out in the centrifugal section using air as working gas and imposing the ambient pressure at the stage inlet. The tested impeller is a centrifugal transonic unshrouded rotor with a radial discharge section. The diffuser height being greater than the impeller blade one, the configuration is at smoke-shelf at the tip side .<\/h3>\n

      The test rig is instrumented to allow overall performance measurements and detailed analysis of the flow within the impeller, at the impeller discharge and within the diffuser. In order to allow impeller \u2013 vaned diffuser interaction analyses, the diffuser can be rotated by a stepping motor. The diffuser discharges the flow in a volute characterised by a rectangular section that acts as a plenum. The measurements\u00a0 have been taken by means of a FRAPP at four different radial positions, for 15 tangential positions on the diffuser pitch and for 12 points on the blade height.<\/h3>\n

      The compressor head was measured by two transducers connected to pressure taps at the inlet and outlet of the machine; the flow rate was measured by a Venturi nozzle manufactured according to the EN ISO 5167-3 standard. The rotational speed was taken by a pick-up located on the compressor shaft; the same device was used as key-phasor for the phase-resolved measurements. Steady temperature measurements in the vaneless diffuser were taken by a total temperature Kiel probe, which implemented a T type thermocouple.<\/h3>\n

      <\/h3>\n

      As centrifugal compressors find a huge number of applications in industry and in aero-engine, the detailed analysis and comprehension of the impeller \u2013 vaned diffuser interaction is of interest to improve the efficiency and the operating range. A wide experimental campaign devoted to the understanding of the impeller \u2013 diffuser interaction is carried out; in particular the work focuses on the features occurring when the compressor works in off design conditions. Data were taken at 3 operating points (near surge, best efficiency and maximum flow rate point) in the impeller - vaned diffuser gap by a fast response probe; the single stage compressor runs at 12500 RPM giving peripheral Mach number of 0.77.<\/h3>\n

      At first, data are reduced to evidence the main impeller flow features which are compared at different flow rates. Furthermore time mean diffuser effects on the impeller are commented and finally the impeller - diffuser interaction is discussed. Results evidence the effect of the diffuser on the impeller, mainly in terms of static pressure and flow velocity, which have a strong dependence on the flow rate.<\/h3>\n<\/div>\n<\/div><\/div><\/div>
      <\/div><\/div><\/div>
      <\/div>
      \n
      \n\t\t\"\"\n\t<\/div>\n\n<\/div><\/div><\/div>
      \n
      \n\t

      Impeller time-mean aerodynamics:\u00a0 Flow development inside the rotor channel (CFD)<\/strong><\/h3>\n