Pressure drop characteristics of soot generated by a DPG and a ...

Pressure drop characteristics of sootgenerated by a DPG and a Euro IV, 2 litrediesel engineGreg Inman, Andrew Todd, Kingsley Reavell,Tim Hands

Introduction The DPG is part of the Cambustion DPF Testing System which tests DieselParticulate Filters for– Backpressure vs soot load– Regeneration characteristics– Filtration efficiency (with a soot monitoring system) This is done by loading filters with soot generated in a Diesel burner, atflows and temperatures similar to engine conditions. This work compares the backpressure produced by the soot from the DPGburner with that from and engine. Effects causing variability in the backpressure associated with– Engine cold starts– High flow conditionswere measured in these tests and are discussed.2

The Cambustion DPG More repeatable and rapid testing of DPGs than engine tests Burner conditions unaffected by DPF backpressure Automated, unattended testing except for loading & weighing the filter.3

4DPG Schematic

DPG Flow – Temperature CapabilityStandard LD versionDPG - LD Operating Temperature : Flow Rate Capability800700regener ationmode600DPF in let temperature º C500400300200max imum syst em loading capabilit ystandard loadingconditions100burner off condit ions00 100 200 300 400 500 600 700 800 900DPF flow kg / hr5

DPG Flow – Temperature CapabilityNew MD VersionDPG - Medium Duty Operating Temperature : Flow Rate Capability800700DPF inlet temperature ºC600500400300200regen / warm upmax possibleloading limitsIncreased fuel flow: approximately doubled loading &regeneration flowstypical loading setpoint100burner off conditions00 100 200 300 400 500 600 700 800 900DPF flow kg/ hr6

DPG Application for Dp vs Soot Mass TestingInstrument : instrument repeatability90802 parts, nominally identical are clearly distinguished on all instruments.Uncoated 2.8 l SiC filters70Backpressure mbar60504030part 1part 22010pore filling and cake formation behaviour clearly quantified00 2 4 6 8 10 12 14 16Corrected soot mass (g)7

DPG Flow Sweep Testing504540Blown Bench MeasurementsDPG measurements at 50 CBackpressure mbar3530252015DPG measurements ambient temp10500 100 200 300 400 500 600 700Flow rate m3n/hr DPG measures backpressure vs flow up to ~ 600 m 3 /h For comparison with engine results, Reynolds number should be the same– Cold flow test at a lower flow rate than the engine!– This keeps the balance of viscous & inertial pressure drops the same.8

Previous Engine Correlation WorkT Hands et al, DEER 2007:Pressure drop vs soot load for Engine soots compared with DPG soot100Transient CycleHigh Load Steady StateDPG80Normalised Pressure drop60402000 5 10 15 20 25 30 35Total Soot (g)9 Difference between cycle & steady state engine soot Engine soot backpressure measured on engine: less accurate Other private data also shows significant variation between engines

New Test Programme DPF canned for easy connection to engine Load on engine or DPG. Cold flow test at 0g, 5g, 15g, 20g & 30g on DPG– Improved accuracy compared with engine backpressure measurementdue to accurate & stable temperature and flow Original plan:regenwarmup0gweighflow testload5gweighflow testload15gweighflow testload20gweighflow testload30gweighflow test10Engine / DPGDPG

Engine Details 2l Common rail Diesel engine Stage 4 emissions compliant Mounted on dynamic dyno– Comparisons made with cycle soot Fitted with Diesel Oxidation Catalyst upstream of DPF– In this test programme, the DPG testing was not fitted with the DOC. This is tosimulate best the application of the DPG for testing filters which are then usedwith an upstream DOC, currently the majority application.– For single brick systems, the engine soot would differ mainly via higher levels ofvolatile components. All tests performed on the same DPF:– 5.66” dia x 10” 4.1 l– Uncatalysed SiC.11

Soot Loading Conditions Engine – 3 conditions used– NEDC – approx 3g/h for this engine– ‘Rural’ drive cycle – 6g/h– Steady state accelerated soot loading (modified engine operating points) – 10g/h DPG– All tests at approx 10 g/h setpoint12

Effect 1: Backpressure ‘Relaxation’ in flow test27g load908070Flow test sweeps flow up and then down.First flow test shows reduced pressure on downsweep60504030201000 50 100 150 200 250 300 350 400Equivalent flow (m3/hr)first flow testrepeatfirst flowtesttestFurther repeats then stable up and down same trajectoryShape closer to expected quadratic13

High Flow Relaxation Conclusions Deposited soot is disturbed by high flow conditions Once relaxation has occurred, soot is then stable. Flow tests all repeated twice in this work, and data quoted from repeat.14

Backpressure reduction in multistage loading (1)120100Equivalent delta p @ 300m3/hour (mbar)806040Accelerated soot loadLoaded to 14.3g and then on to 19.7gBackpressure lower at 19.7g than 14.3!2000 5 10 15 20 25Soot load (g)15

Backpressure Reduction In multistage loading (2)1009080Pressure drop at 300m³/hr (mbar)7060504030Loaded and flowtested same dayPart loaded andtopped up from cold,then flow testedSS Engine sootloads201000 5 10 15 20 25 30 35Sootload (g)16

DPG soot subjected to cold start on engine10090Flow test80Load on DPGPressure drop at 300m³/hr (mbar)7060504030Flow testEngine cold startFlow testLoad on DPGFlow testDPG sootloads20Engine cold start10Flow test00 5 10 15 20 25 30 35Sootload (g)17

Cold Restart Backpressure Reduction16016maf_kgh_mes140DPF Indelta pMAF constant1412012MAF (kg/hr), Temperature (°C)1008060Engine StartedSpeed increasedto 2000rpmPressure drop decreasing1086dP (mbar)404202Dry gas enetering DPF 'Wet' gas entering DPF (Condensate heating)0030 35 40 45 50 55 60 65 70Time (s)18

Recovery of Reduced Backpressure160140120Part loaded to 17g on DPGCold start on EngineLoading continued to 29.5gCompared with continuous load to 29g1008060402000 5 10 15 20 25 30DPF dP corr DPF dP corr DPF dP corr19

Effect of Cold Start - summary Regardless of soot type, engine cold start appears to cause reduction inbackpressure Does not occur with restart in loading on DPG Reduction in backpressure is visible in real time during engine start Possibly connected with condensation & re-evaporation of water from sootcake, damaging the structure. Reduction in backpressure not fully recovered with further loading. All engine loaded data in the comparison is therefore loaded directly fromzero to the final weight.– Significant increase in the amount of testing required.20

Backpressure vs Soot Load Engine & DPG120100NEDC Soot (3g/hr)Accelerated Steady State Soot (10g/hr)Rural Drivecycle Soot (6g/hr)DPG Soot (10g/hr)EmptyCoated DPF DPG Soot (10g/hr)Pressure drop at 300m³/hr (mbar)80604020All cycles produce effectively identicalbackpressureDPG also the same, except for possible slightincrease at very high loads00 5 10 15 20 25 30 35Sootload (g)21

Conclusions Significant effects on backpressure measurement noted in this work:– Relaxation of soot at high flow rates– Permanent reduction in backpressure by engine cold start With these effects avoided, all engine cycles produced very similarbackpressure vs soot load. DPG soot also behaves the same as engine soot. Inconsistent with earlier experience– Previous tests did not carefully avoid effects above– Increased variability in engine rather than DPG tests– Different behaviour of different engines.22

Further Work There is scope for further work:– Variation in soot behaviour between different engines.– Effect of different filter types (catalysed, materials)– Investigation of effects at very high loads– Comparison of regeneration behaviour of engine & DPG soot – ongoing.23

AcknowledgementsThanks to all the coauthors who did more of this work than me, and alsoRay Brand and Jason Sumner who did most of the testing.24