C_6_Centrifugals-离心压气机设计

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

Compressors (C) C_6: Centrifugal compressorsProf. Michael Casey MA, DPhil, FIMechE, CEng, FASMERetired Professor of Thermal Turbomachinery in the University of StuttgartAn educational course on compressors based on lectures given by the author in the University of StuttgartMichael CaseyVersion: August 2015Compressors C_6_CentrifugalsPage 1

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

ContentsC_6.1: Introduction and definitionsC_6.2: Velocity triangles and energy transferC_6.3: Losses in centrifugal compressors C_6.4: Design of impeller inlet C_6.5: Design of impeller exit C_6.6: Impeller blade geometry C_6.7: Design of diffuser C_6.8: Volute C_6.9: Return channelC_6.10: Centrifugal compressor performance characteristicsMichael CaseyVersion: August 2015CompressorsC_6_CentrifugalsPage 2

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.1Centrifugal compressors Also known as radial compressors – but usually have axial inlet flow and radial outlet flow so are really mixed flow compressors All open impellers (no shroud) appear very similar (at first sight)– – – – Back-sweep at outlet of - 30 to - 50° Inlet blade angles at tip of – 60° Splitter vanes – every second blade cut back at the inlet Inlet diameter at tip around 0.7 of outlet diameter Pressure ratios between 1.5 and 10 Comparison with axial compressors– Less flow for given overall size due to smaller inlet area – Lower efficiency than an axial compressor (complex flow passages) – Higher work and pressure ratio for same rotational speed (centrifugal effect) A single radial stage can typically replace 3 axial stages – Centrifugals have flatter speed-line performance curves than axialsMichael CaseyVersion: August 2015CompressorsC_6_CentrifugalsPage 3

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.2What distinguishes a centrifugal compressor?The flow experiences a marked radius change as it passes through the rotor Axial RadialCentrifugals Diagonal MixedMichael CaseyVersion: August 2015CompressorsC_6_CentrifugalsPage 4

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.3Where are centrifugal compressors used? Radial compressor applications– Turbochargers – Gas turbines APU’s and small and micro sized gas turbine Larger gas turbines – Last stage of axial-centrifugal compressor Multistage compressors for industrial gases – gas transport in pipelines – air-liquefaction plants – large refrigeration plant – Centrifugal fans for air conditioning – Blowers process gases mining ventilationMichael CaseyVersion: August 2015CompressorsC_6_CentrifugalsPage 5

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.4Some examplesTurbocharger (ABB)Single stage compressor (MAN Turbo)Multistage compressor (MAN Turbo)Ventilator fan (EBM Papst)Compressors C_6_Centrifugals Page 6Michael CaseyVersion: August 2015

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.5Compressor stage componentsCollector / housing / voluteImpeller inlet (inducer) Casing Impeller blade3 Diffuser exitStator vane, diffuser. (vaned or vaneless) 2 Impeller exit / diffuser inlet Hub surface Rotating impeller (rotor)Source: Atlas CopcoInlet guide vanes (optional) 0 IGV Inlet 1 Impeller InletCompressorsMichael CaseyVersion: August 2015C_6_CentrifugalsPage 7

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.6Impeller geometry The most important geometric parameters– Impeller outlet width ratio 0.04 < b2/D2 < 0.10 – Tip clearance gap j > 0.5 mm – Blade number (at outlet) 12 < z < 32 – Splitter vanes and blade thickness (t) – Axial length L / D2 ~ 0.35 D1s – Inlet diameter ratios D1s / D2, ~ 0.7, D1h / D2 ~ 0.25 D1n – Blade angles Inlet tip b1s,= - 60°, Outlet b2 ,~-40°- b2L jb2D2Michael CaseyVersion: August 2015CompressorsC_6_CentrifugalsPage 8

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.7Centrifugal compressor performance map Work input and pressure ratio increases roughly with the square of the speed and the volume flow increases roughly linearly with speed (~ parabola)– Low speed has very low boost pressure with low volume flows Along a speed line the pressure ratio increases as the volume flow decreases but close to the peak pressure rise becomes flatter before the flow becomes unstable (surge or rotating stall) Surge line ~Parabola The map splits into three regions– Low flow - unstable region (left) – Normal flow - stable region (middle) – High flow - maximum flow limited by choke Unstable region = konst. Choke 100% 80% n 60% Speed lines The design point should lie in the stable region close to peak efficiencyOperation in unstable region not allowed:– Pressure and flow fluctuations – Mechanical blade vibrations – Noise140% 0 See also chapter C_8Version: August 2015 Compressors VC_6_Centrifugals Page 9Michael Casey

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.8Reference plane notation Notation for stage reference planes– – – – 0 1 2 3 upstream of stator (inlet guide vane, if present) impeller inlet, downstream of IGV impeller outlet, diffuser inlet 3 diffuser outletS 2DiffuserStage Impeller Diffuser1 to 3 1 to 2 2 to 31RImpellerMichael CaseyVersion: August 2015CompressorsC_6_CentrifugalsPage 10

Lecture of Casey, Compressor design. Casey教授在清华讲座,压气机设计

C_6.1.9Velocity triangle notation Notation – Meridional direction used instead of axial or radial direction – cu and wu positive in rotational direction cm – cu and a positive as shown below cr – wu and b negative as shown …… 此处隐藏：6572字，全部文档内容请下载后查看。喜欢就下载吧 ……