Numerical Analysis on the Oil Pumping Process for ... - ESSS

Company ProfileItaly• Market and Technological Leader in Hermetic Compressorsfor Refrigeration;• It offers complete cooling solutions in the development ofinnovative and high performance products for thecommercial and household refrigeration segments;• Almost 10 thousand employees worldwide;Mission:"Provide innovative solutionsfor a better quality of life".

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Design to high efficiency compressorsImprovements on the:ManifoldMechanismsupportElectricmotorHighEfficiencyMechanicalPower LossesLubricationAssure:Low noiseQuality and ReliabilityIt is very important to reliability and highefficiency in refrigeration compressors.Low costs

Oil Supply System for Reciprocating Compressors• The lubricant oil is speed upby the centrifugal force untilthe secondary bearing, then itis carried mechanically by thelubrication groove.Oil hole - mainbearingOil hole -secondary bearingOutlet for the pistonOil hole – eccentricbearingCrankcaseLubricationgroove... and about thepumping head?CrankshaftOil pumpInlet – oil from case

Oil Supply System for Reciprocating Compressors• Modeling the simplified problem...dpprzdr pzrdzin rigid body motion: p g a p e rzh0r1 p er p kz 2R1 r 2g2 R a za 0 0a 2 r r gk (a e2rr a e a k )zp z p1h122h2 2r r gz z r2g1 h2where,01R4g21

Oil Supply System for Reciprocating Compressors• and introducing a bottom hole... ur t ururrurur uzurz2ur p 1 u rrrrurr 12ru2r22 uzr2urr2u grQcP 2 ucdA A2r r 2rr c42 ru0c0dr• The open area of the pump’sorifice is unable to support thepumping pressure. So, the oilflows down through the hole.• “The pressure drop in the orificecan be determined by taking intoaccount of inflow and outflowthrough the hole”. (Itoh, 1992)

Oil Supply System for Reciprocating Compressors• The main variables at mechanical kit thatinfluences in the pumping head are:– Inlet and outlet diameter;– Blade presence– Oil viscosity;– Shaft speed;– Lubrication groove and orifices– Oil pump imersion;– Geometric deviationsOperationconstraintsPumpconstraintsAssemblyconstraintsEx.: concentricity between pumpand rotation axisShaftconstraints

CFD 3D Simulation with ICEM/CFX‣ Meshing in the ICEM:• Easier to generate the interface domainsand control the quality mesh.• Tetraedric mesh + prisms (near the wallto increase the resolution).

CFD 3D Simulation with ICEM/CFX‣ Some options to input for the CFX analysis:• Transient analysis• Biphasic flow (oil based water + air)• Time simulation 2s (step 0.01s)• Buoyancy model• Homogeneous model for multiphase and heat transfer• Laminar flow• Imersion 10mm• Angular speed 3000rpm

CFD 3D Simulation with ICEM/CFX‣ and to raise the oil…1. To rotate the Pump’s walls• The geometry must be axisymmetric• It does not support eccentric pump2. To rotate the inside domain3. To deforme the mesh (not analyzed)

Outlet FlowCFD 3D Simulation with ICEM/CFX‣ Mesh evaluation:Number of elements

CFD 3D Simulation with ICEM/CFX‣ Transient flow behaviorInitial timeTime step 5Time step 50Link to movieTime step 200

<strong>Numerical</strong> Results‣ Drives for the simulation• Evaluate the oil flow sensivity relative to the pump variables:• Outlet diameter• Inlet diameter• Blade presence

Experimental Test• Bench Test:• The crankshaft rotation iscontrolled by an inverter.• The oil flow is evaluatedby infrared sensors. Itcalculates the time to theoil speed up in a knownvolume.

Outlet Flow<strong>Numerical</strong> Results:‣ Blade evaluation:1,2Superficialvelocity Z1,00,80,6it increases themomentum for the fluid.0,40,20,0Without BladeWith Blade0 50 100Time step150 200Superficialvelocity Z

Outlet Flow<strong>Numerical</strong> Results:‣ Outlet flow: 3 pump models:1,61,4This pump is able to providegood results, but is hard toassure the concentricitybetween the bottom end andthe rotation axis in themanufacturing process.1,21,00,80,60,40,20,0REFERENCEPump RefPrototype Concentric PumpPrototype Eccentric Pump0 20 40 60 80 100 120 140 160 180 200Time step

Outlet FlowOutlet Flow<strong>Numerical</strong> Results:‣ Outlet diameter evaluation:1,21,11,00,9Δ~10%Assemblyconstraint:to definetolerancesfor the outletdiameter0,80,70,610,50,40,30,2Outlet -0.4mmOutlet REF0,950,9ExperimentalresultsΔ~10%0,10,00 50 100 150 200 250 300Time stepOutlet +0.4mmAbove upper value (Outlet +0.4mm) the outflow isinsensitive to increase the outlet diameter.0,850,8Outlet REF Outlet - 0.4mmOutlet diameter (mm)

Outlet Flow<strong>Numerical</strong> Results:‣ Inlet diameter evaluation:1,41,31,21,11,00,90,80,70,60,50,40,30,20,10,0Inlet -0.5mmInlet REFInlet +0.5mmInlet +1.0mmInlet +1.5mm0 50 100 150 200 250 300The relation between the inletdiameter and the outlet flow is notlinear:- if the inlet is smaller, it constrictsthe flow;- if it is greater, the pumpingpressure drops due the open area.An optimum point must be find.Time step

Experimental Results:‣ Flow x Inlet x Outlet• The statistical analysis ofthe experimental resultsshows the similar directionfrom numerical simulation.

Concluding remarks• The sensitivity analysis for the oil supply process has beenperformed.• The CFX/ICEM proven to be effective for this kind ofapplication. It is a powerful tool since it allows time andcosts reduction looking for the geometric variables andtolerances in the prototype evaluation.• The CFX still provide others analysis on the flow behaviorfor this application like: use of the turbulence models,comparison between the different models to speed up theflow (domain motion, rotation wall, deformed mesh).

Concluding remarks• The total time simulation could be optimized if the meshingwas made in the Workbench.• Next steps:– Evaluate the oil flow considering also the crankshaft’s constraints.– Work to optimize the mesh (simulation time).

Thank you for theattention!Diego Sacomoridiego_sacomori@embraco.com.br