Engine parts Turbochargers

turbocharged engine advantages disadvantages and turbocharged engine maintenance
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Part 2: Turbochargers, Engine Performance Metrics Reciprocating Internal Combustion Engines Prof. Rolf D. Reitz Engine Research Center University of Wisconsin-Madison 2014 Princeton-CEFRC Summer School on Combustion Course Length: 15 hrs (Mon.- Fri., June 23 – 27, 2014) Copyright ©2014 by Rolf D. Reitz. This material is not to be sold, reproduced or distributed without prior written permission of the owner, Rolf D. Reitz. 1 CEFRC1-2 , 2014 Part 2: Turbochargers, Engine Performance Metrics Short course outine: Engine fundamentals and performance metrics, computer modeling supported by in-depth understanding of fundamental engine processes and detailed experiments in engine design optimization. Day 1 (Engine fundamentals) Part 1: IC Engine Review, 0, 1 and 3-D modeling Part 2: Turbochargers, Engine Performance Metrics Day 2 (Combustion Modeling) Part 3: Chemical Kinetics, HCCI & SI Combustion Part 4: Heat transfer, NOx and Soot Emissions Day 3 (Spray Modeling) Part 5: Atomization, Drop Breakup/Coalescence Part 6: Drop Drag/Wall Impinge/Vaporization/Sprays Day 4 (Engine Optimization) Part 7: Diesel combustion and SI knock modeling Part 8: Optimization and Low Temperature Combustion Day 5 (Applications and the Future) Part 9: Fuels, After-treatment and Controls Part 10: Vehicle Applications, Future of IC Engines 2 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Turbocharging Pulse-driven turbine was invented and patented in 1925 by Büchi to increase the amount of air inducted into the engine. - Increased engine power more than offsets losses due to increased back pressure - Need to deal with turbocharger lag Improved 3 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Turbocharging Purpose of turbocharging or supercharging is to increase inlet air density, - increase amount of air in the cylinder. Mechanical supercharging - driven directly by power from engine. Turbocharger - connected compressor/turbine - energy in exhaust used to drive turbine. Supercharging necessary in two-strokes for effective scavenging: - intake P exhaust P - crankcase used as a pump Some engines combine engine-driven and mechanical (e.g., in two-stage configuration). Intercooler after compressor - controls combustion air temperature. 4 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Turbocharging Energy in exhaust is used to drive turbine which drives compressor Wastegate used to by-pass turbine Charge air cooling after compressor further increases air density - more air for combustion 5 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Regulated two-stage turbocharger Duplicated Configuration per Cylinder Bank LP stage Turbo-Charger with Bypass HP stage Turbo Compressor charger Bypass Charge Air Regulating valve Cooler EGR Cooler EGR Valve GT-Power R2S Turbo Circuit HP TURBINE Compressor Bypass EGR Valve EGR Cooler Charge Air Regulating valve Cooler Compressor HP stage Turbo Bypass charger LP stage Turbo-Charger with Bypass Regulating Valve LP Stage Bypass LP TURBINE 6 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Intercooler for IVC temperature control Q  P V  IVC Isentropic   PV  IVC Reduced Peak Temp (NOx) Improved phasing ( 1) T V  ln P IVC   TV  IVC ln T Pressure T ign /time of Compressor ignition Boost Q IVC TDC IVC TDC ln V ln V Boost explains 20% of the improved fuel efficiency of diesel vs. SI 7 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Automotive compressor Centrifugal compressor typically used in automotive applications Provides high mass flow rate at relatively low pressure ratio 3.5 Rotates at high angular speeds - direct coupled with exhaust-driven turbine - less suited for mechanical supercharging Consists of: stationary inlet casing, rotating bladed impeller, stationary diffuser (w or w/o vanes) collector - connects to intake system 8 CEFRC1-2, 2014 Anderson, 1990 Part 2: Turbochargers, Engine Performance Metrics Compressible flow – A review Area-velocity relations Tds dh dp /  Gibbs  for M1 for M1 Energy dhVdV  dPVdV Euler  d  dA dV  AV  Const    0 Subsonic nozzle Subsonic diffuser Supersonic diffuser Supersonic nozzle  AV dA0 dA 0 dA 0 dA 0 from AV  dV0 dV 0 dV 0 dV 0 from Euler  dP0 dP 0 dP 0 dP 0 kinetic energy pressure recovery kinetic energy dA dV 2  (M 1) AV 2 dA (1 M )  dP 2 AV  Traffic flow behaves like a supersonic flow 9 CEFRC1-2, 2014 Anderson, 1990 Part 2: Turbochargers, Engine Performance Metrics Model passages as compressible flow in converging-diverging nozzles PV m AV A RT Minimum area point A RT c P  1/ 2 0  P AM (P / P ) /(T /T ) 0 0 0 RT 0 With M=1: Fliegner’s formula Choked flow, M=1 1  1 2  2( 1) m () P A A/A M 10  1 RT 0 Subsonic Supersonic 2 solutions for Area Mach number relations  1 same area 2( 1) A 1 2 ( 1) 2  (1 M )  AM  12  1/ 2  1 11   0   1 A P21 P     0.528 0 1  reservoir P/P throat  ( ) 1 ( ) exit  0   A P  12 P   00  0 1 M ∞ 10 CEFRC1-2, 2014 Anderson, 1990 Part 2: Turbochargers, Engine Performance Metrics Isentropic nozzle flows  T  1 P  1 2 2  1 0 0  1 M  (1 M ) 1 1 Ex. Flow past throttle plate P 2 T 2 1 1 P P 0 1 y 1 0 P=P P b 0 Choked flow for P 53.5 kPa = 40.1cmHg 2 ambient reservoir WOT Choked m 1 P b P/P 0 y 0.528 40.1 76 M=1 Manifold pressure, P cmHg 1 0 x 11 CEFRC1-2, 2014 Anderson, 1990 Part 2: Turbochargers, Engine Performance Metrics Application to turbomachinery Fliegner’s Formula:  1 2  Variable Geometry Compressor/ 2( 1) m () P A M 10 turbine performance map  1 RT 0 Increased speed Choked flow m T /T “Corrected mass ref 0 flow rate” PP / 0 ref A measure of effective flow Reduced flow passage area area 1.0 1/0.528=1.89 P /P 0 Total/static pressure ratio 12 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Heywood, 1988 Compressor (T T ) outisen in   c (T T ) out in P 03 T P = P 3 out Heywood, Fig. 6-43 Air at stagnation state 0,in accelerates to P 2 inlet pressure, P , and velocity V . 1 1 Compression in impeller passages increases pressure to P , and velocity V . 2 2 P = P 0 0,in Diffuser between states 2 and out, recovers air kinetic energy at exit of impeller P 2 1 producing pressure rise to, P and V /2 c out 1 P low velocity V out W m h h   c a out in  1 a S   a m c T  p a P in Note: use exit static pressure and inlet total a out W1  c   pressure, because kinetic energy of gas  p c 0,in   leaving compressor is usually not recovered  13 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Heywood, 1988 Compressor maps Work transfer to gas occurs in impeller via change in gas angular momentum in rotating blade passage Surge limit line Speed/pressure limit line – reduced mass flow due to periodic flow reversal/reattachment in Non-dimensionalize blade passage boundary layers. tip speed (ND) by speed Unstable flow can lead of sound to damage At high air flow rate, operation is limited by choking at the minimum Pressure ratio evaluated area point within compressor using total-to-static pressures since exit flow Supersonic flow kinetic energy is not recovered Shock wave Heywood, Fig. 6-46 14 CEFRC1-2, 2014 Serrano, 2007 Part 2: Turbochargers, Engine Performance Metrics Compressor maps 3.0 Pressure GM 1.9L diesel engine Ratio (t/t) 2.8 190000 35000 40000 50000 70000 2.6 90000 110000 130000 150000 2.4 170000 180000 190000 2.2 Efficiency 0.8 (T/T) 2.0 180000 170000 0.7 1.8 150000 0.6 1.6 130000 Corrected Air Flow (kg/s) 1.4 0.5 110000 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 1.2 90000 70000 Corrected Air Flow (kg/s) 50000 35000 40000 1.0 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 15 CEFRC1-2, 2014 Reitz, 2007 Part 2: Turbochargers, Engine Performance Metrics Automotive turbines Naturally aspirated: P =P =P (5-7-8-9-1) intake exhst atm Boosted operation: Negative pumping work: W m() h h t g in 0,out P P – but hurts scavenging 7 1  1 g  P  g  P  0,out W m c T  1  t g P in t  3 4 P in    Expansion 2 Blowdown 5 Available work Compression (area 5-6-7) 1 9 6’’ P Turbine intake 6 P exhst Compressor 8 7 6’ P amb BDC TDC V P-V diagram showing available exhaust energy - turbocharging, turbocompounding, bottoming cycles and thermoelectric generators further utilize this available energy 16 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Turbochargers Radial flow – automotive; axial flow – locomotive, marine P 0 = P 0,in T P 1 2 V /2 c 1 P T 3   T 0 P 2 m  m corrected g p 3 p 0 out N N  corrected T 3 P T 0 3 0 P = P 3 out (T T ) out in   t (T T ) outisen in S 17 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Compressor selection To select compressor, first determine engine breathing lines. The mass flow rate of air through engine for a given pressure ratio is:  = IMP = PR atmospheric pressure (no losses) = IMT = Roughly constant for given Speed 18 CEFRC1-2, 2014 Part 2: Turbochargers, Engine Performance Metrics Engine breathing lines Engine Breathing Lines 1.4L Diesel, Air-to-Air AfterCooled, Turbocharged 3.8 3.6 Torque Peak (1700rpm) Trq Peak Operating Pnt 3.4 Rated (2300rpm) 3.2 Rated Operating Pnt 3 2.8 2.6 2.4 2.2 2 1.8 1.6 Parameter Torque Peak Rated Units 1.4 Horsepower 48 69 hp BSFC 0.377 0.401 lb/hp-hr 1.2 A/F 23.8 24.5 none 1 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000 11.000 12.000 13.000 14.000 Intake Mass Flow Rate (lb/min) 19 CEFRC1-2, 2014 Compressor Pressure RatioPart 2: Turbochargers, Engine Performance Metrics Heywood, 1988 . . W = W t c  a  1 a  1  g        Cp T m  g      p   p   g 3 fuel 2 4      1 1     1   t c mech          p Cp T p    1  a 1  3    m   air       20 CEFRC1-2, 2014