CONVENTIONAL AND ELECTRICALLY HEATED DIESEL OXIDATION CATALYST MODELING IN GT-SUITE

Transcription

1 CONVENTIONAL AND ELECTRICALLY HEATED DIESEL OXIDATION CATALYST MODELING IN GT-SUITE G. Cerrelli, P. Ferreri GM Global Propulsion Systems - Torino GT-Conference 2018, Frankfurt

2 AGENDA Background and motivation Diesel Oxidation Catalyst basics and modeling Components description Modeling approach and methodology overview Models development: Page 3 Page 4 Page 5 Page 6 conventional Diesel Oxidation Catalyst electrically Heated Catalyst Models assessment in engine-scale conditions Summary and future work Page 7 Page 13 Page 15 Page 30 Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE

3 Background and motivation Diesel Aftertreatment Systems development challenges: emissions limits tightening competing requirements different regulatory frameworks increasing complexity upcoming CO 2 regulations Many aspects to be optimized: tailpipe emissions fuel economy system cost Integration between testing and physical-based numerical simulation is a key factor to reduce development time and cost Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 3 /31

4 Diesel Oxidation Catalyst basics and modeling Diesel Oxidation Catalyst (DOC) functionalities HC/CO conversion NO 2 /NOx ratio increase exotherm Assumptions 1-D discretization (e.g.: temperature = f(x)) diffusion (external, internal) global kinetics steady-state for surface and gas phases Governing equations transport of mass, energy, momentum Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 4 /31

5 Components description Conventional DOC Electrically Heated Catalyst (EHC) single ceramic brick square channels 114 g/ft 3, Pt:Pd = 3:1 two metallic bricks (heated slice + main matrix) sinusoidal channels coating similar to ceramic Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 5 /31

6 Modeling approach and methodology overview calibration loops kinetics development SIM vs EXP reactor-scale model model up-scaling SIM vs EXP chemical reactions selection reactions rate expression selection reactor data geometry update external heat transfer kinetics adaptation to real exhaust gas engine data full-size catalyst model Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 6 /31

7 Models development: conventional Diesel Oxidation Catalyst Reactor-scale testing: two types of tests extensive tests matrix Test ID CO C 3 H 6 C 10 H 22 NO NO 2 [#] [ppm] [ppmc1] [ppmc1] [ppm] [ppm] LO#1 800 LO# LO# LO# LO# LO# LO# LO# LO# LO# LO# LO# Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 7 /31

8 Models development: conventional Diesel Oxidation Catalyst Core sample substrate model setup washcoat substrate Metric Unit Value Frontal area [mm 2 ] 507 Length [mm] 76.2 Cells density [cpsi] 400 Channel shape [-] square Wall thickness [mil] 3.5 Substrate material [-] cordierite Washcoat average thickness [µm] 40 Washcoat material [-] alumina Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 8 /31

9 Models development: conventional Diesel Oxidation Catalyst Chemical reactions set Mechanism Site Chemical reaction CO oxidation PGM CO + 0.5O 2 CO 2 HC oxidation PGM C 3 H O 2 CO 2 + H 2 O C 10 H O 2 10CO H 2 O reversible NO oxidation PGM NO + 0.5O 2 NO 2 NO 2 reduction by HC PGM C 3 H 6 + 9NO 2 9NO + 3CO 2 + 3H 2 O C 10 H NO 2 31NO + 10CO H 2 O NO 2 reduction by CO PGM CO + NO 2 CO 2 + NO HC split in two families NO 2 formation equimolar NO 2 reduction to NO HC SCR (NO reduction by HC) HC storage PGM zeolite C 3 H 6 + 9(1+y )NO 3CO 2 + 3H 2 O + 4.5(1-y )N 2 + 9y N 2 O C 10 H (1+y )NO 10CO H 2 O (1-y )N y N 2 O C 10 H 22 + z C 10 H 22 (z) C 10 H 22 (z) C 10 H 22 + z Heavy HC storage Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 9 /31

10 Models development: conventional Diesel Oxidation Catalyst Reaction rate expressions ({ }) ( ϑ ) r = k f X g i i j k Example: CO oxidation CO + 0.5O 2 CO 2 1 I i k i = Ai exp Ei R T 1 rco = kco { CO} { O 2 } ICO s A i = pre-exponential multiplier E i = activation energy f({x j }) = function of concentrations g(θ k ) = function of coverages T s = surface temperature I i = inhibition function Inhibition function: eco eno { } { } { } I = 1+ K CO 1+ K NO 1+ K C H i i ehc i,, 3 6, 3 6 i CO i NO i C H i K = A exp E j = CO, NO, C H ji, ji, j 3 6 R T s Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 0/3 1

11 Models development: conventional Diesel Oxidation Catalyst Reaction rate expressions ({ }) ( ϑ ) r = k f X g i i j k Example: CO oxidation CO + 0.5O 2 CO 2 1 I i k i = Ai exp Ei R T 1 rco = kco { CO} { O 2 } ICO s A i = pre-exponential multiplier E i = activation energy f({x j }) = function of concentrations g(θ k ) = function of coverages T s = surface temperature I i = inhibition function Inhibition function: eco eno { } { } { } I = 1+ K CO 1+ K NO 1+ K C H i i ehc i,, 3 6, 3 6 i CO i NO i C H i K = A exp E j = CO, NO, C H ji, ji, j 3 6 R T s 11 chemical reactions 48 parameters calibration done by both manual attempts and optimization loops Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 1/3 1

12 Models development: conventional Diesel Oxidation Catalyst Example of simulations vs experiments matching CO Test conditions 800 ppm C 3 H 6 C 10 H 22 NO NO ppmc1 400 ppmc1 100 ppm 100 ppm O 2 12 % CO 2 5 % H 2 O 5 % N 2 balance SV (std) /h Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 2/3 1

13 Models development: electrically Heated Catalyst Full-size substrate model setup actual channel shape square equivalent channel shape equivalence based on conservation of: heat capacity permeability gas/wall heat transfer mass diffusion for heated slice and main matrix Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 3/3 1

14 Models development: electrically Heated Catalyst Full-size substrate model setup actual channel shape square equivalent channel shape equivalence based on conservation of: heat capacity permeability gas/wall heat transfer mass diffusion for heated slice and main matrix Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 4/3 1

15 Models assessment in engine-scale conditions exhaust mass flow [g/s] Temp_IN [degc] full-size tested catalyst Temp_OUT [degc] CO, THC, O 2, CO, THC, O 2, NOx, NO, CO 2 NOx, NO, CO 2 Electrical power supply (EHC) Full-size catalysts experimental characterization: 1.6L L4 engine driving cycles flow temperature from thermocouples emissions from analyzers real aged components H 2, H 2 O from estimation THC = C 3 H 6 + DF (1:4) on C1 basis full-size simulated catalyst simulated emissions and temperature DF = unburned Diesel fuel = C 14.6 H 24.8 Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 5/3 1

16 Models assessment in engine-scale conditions: conventional DOC WLTP temperature and CO conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 6/3 1

17 Models assessment in engine-scale conditions: conventional DOC WLTP temperature and CO conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 7/3 1

18 Models assessment in engine-scale conditions: conventional DOC WLTP temperature and CO conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 8/3 1

19 Models assessment in engine-scale conditions: conventional DOC WLTP THC and NO/NO 2 conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 1 9/3 1

20 Models assessment in engine-scale conditions: conventional DOC WLTP THC and NO/NO 2 conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 0/3 1

21 Models assessment in engine-scale conditions: conventional DOC WLTP THC and NO/NO 2 conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 1/3 1

22 Models assessment in engine-scale conditions: conventional DOC WLTP THC and NO/NO 2 conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 2/3 1

23 Models assessment in engine-scale conditions: electrically Heated Catalyst FTP-75 temperature vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 3/3 1

24 Models assessment in engine-scale conditions: electrically Heated Catalyst FTP-75 temperature vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 4/3 1

25 Models assessment in engine-scale conditions: electrically Heated Catalyst FTP-75 temperature vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 5/3 1

26 Models assessment in engine-scale conditions: electrically Heated Catalyst FTP-75 emissions conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 6/3 1

27 Models assessment in engine-scale conditions: electrically Heated Catalyst FTP-75 emissions conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 7/3 1

28 Models assessment in engine-scale conditions: electrically Heated Catalyst FTP-75 emissions conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 8/3 1

29 Models assessment in engine-scale conditions: electrically Heated Catalyst FTP-75 emissions conversion vs time simulations vs experiments Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 2 9/3 1

30 Summary and future work 1-D models of a conventional and an electrically heated DOC have been developed in the present study a satisfactory agreement between simulations and experiments has been detected in engine-scale driving cycles conditions, showing the effectiveness of the applied methodology future work will focus on: ageing status improvement of NO 2 prediction engine-out THC speciation impact of uneven flow and temperature distributions at catalyst inlet general geometry option exploration Conventional and Electrically Heated Diesel Oxidation Catalyst Modeling in GT-SUITE 3 0/3 1

31 Acknowledgments: Continental Emitec GmbH Thank you for you attention. Any questions? Giuseppe Cerrelli Computational & Experimental Area Vehicle Systems General Motors Global Propulsion Systems C.so B. Telesio, Torino (TO) Italy Tel