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2009-12-06 18:27:57

knowledge of DPF
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  1. composition of PM and %
    • solid fraction--SOL / carbon soot (carbon and ash)
    • soluble organic fraction--SOF (from oil and fuel)
    • sulfate particulates--SO4 (sulfuric acid,water)
    • ↑ SOF%:↓ load, ↑ EGR, active DPF regeneration
    • high load high speed, low PM emission(?)
  2. what is "filtration"?
    • 1, depth ~ : PM accumulated on filter porosity
    • 2, cake ~: PM forms a prosity layer
  3. why choose honeycomb structure?
    ↑ surface↑ efficiency (modify back P-> ↓ v of gas passing-> time ↑-> η
  4. why asymmetric DPF cell designs? usually use?
    • haigher soot storage, lower pressure drop with high soot loading
    • actagon/squre
  5. what mechanisms of particles deposition does depth filtration rely on?
    • diffusional deposition
    • inertial deposition
    • flow-line interception
  6. 3 phrases of regeneration, and reactions
    • filtration
    • passive regeneration 300~400˚C(slow) :NO2+C->NO+CO, NO2+C->0.5N2+CO2
    • active regeneration 600˚C(fast) :C+O2->CO2/CO (with fuel add Ce, Fe can be 380~450˚C)
    • *J.M.CRT:C+NO2->NO+CO/CO2, but not good for PV, regen time=30min, need sulfur deactive catalyst
  7. What is the effect of fuel additive
    • without fuel add is for-life solution (>20000km)
    • with fuel add is maintenance required.
  8. what control the activation of regeneration?
    what is the objective of strategy of O2based?
    what strategy can use?
    • air flow meter sensor, inlet DPF temp sensor, DPF press drop sensor
    • monitoring PM loading, inlet T>600, O2>5%
    • pilot & main inj. timing retarded, after & post injection activation(IDLE:also multiple inj), inj P variation,
    • EGR reduction or deactivation
    • inlet fresh air reduction(?)
    • Torque correction
  9. what assessment used for catalyzed DPF critical regeneration events?
    • thermal shock test (activation of RGN at 1750rpm 1,5bar for 2 min, until the combustion start--P drop peak)
    • measurement of DPF T evolution
  10. why DPF regeneration management is more critical if use BIODIESEL on standard diesel engines without modification?
    • regeneration rate of BDF is twice as fast as that of Diesel. (higher regeneration efficiency)
    • Biofuel has lower soot mass limit than conventional diesel.
    • higher max T and T gradient
  11. DPF requirement:
    • high filtration efficiency (>90%)
    • high thermal resistance (no damage up to 1200˚C)
    • high mechanical resistance (isostatic strength>4 Mpa)
    • high chemical inertia
    • high porosity (>42%)
    • low pressure drop (<7kPa @ 600 m3/h)
  12. the function of filter wall active "layer"
    • catalyze soot combustion during RGN, minimize residual soot
    • reduce CO&HC emission during regeneration
  13. DPF design preferance
    • volume: ↑better for technical function (↓RGN frequency & ∆P, ↑ oil change interval & ash tolerance), worse for cost ,wight, vehicle intergration
    • Length/diameter:↓better for reliability, RGN frequency, ∆P 宁胖不瘦
  14. the material used for DPF
    outside can
    • outside can: metallic
    • mat: ceramic(外圈第二层)
    • monolith: cement(flexible enough when temperature change, componsate the stress)
    • segment: SiC
  15. why use Close Coupled PDF from E4 to Euro 5?
    • 1) 50˚C increase of exhaust T <- exhaust T is a function of distance from outlet turbine
    • 2) -35% time to reach the same reg T3) ↑ viscosity, ↓ oil dilution
  16. 1)ECU sensors for DPF? 2)Vehicle mission profile will have impact on? 3)What is Soot Loading Driving Parameters? 4)What is regeneration activation driving Parameters? 5)When will RGN activated? 6)What parameters have impact on RGN duration?
    • 1) 2 ex gas T: outlet pre cat, inlet DPF Pressure: DPF P drop
    • 2) soot loading estimation, regeneration efficiency
    • 3) Mission Profile, Car inertial weight, Car Road Load
    • 4) DFP Soot Load, Mission Profile, No perception by driver
    • 5) when most favorable condition is detected & accelerator pedal is released to minimize T variation
    • 6) RGN duration is optimized for each mission profile, only effective when TinDPF>580˚C, and is interrupted if time > 20min
  17. other 2 statistical model for ECU
    • 1) residual soot map
    • 2) oil quality driving parameter
  18. Why additive DPF?
    additive is added in the fuel not just on the monolith, so the contact is optimized, get higher T
  19. additive should make sure the optimal DP regeneration behavior. what kind of behaviour?
    • Faster soot oxidation with additive.
    • lower soot burn off with additive.
    • fast, uniform and complete soot combustion(should provide high surface area->small cristallite size)
  20. 2 different chemical species of fuel additive
    • 1,organometallic salts: Fe2O3 (highly efficient to decrease combustion temperature)
    • 2,Eolys: Ce-Ce/Fe-Fe (a colloidal dispersion of a iron oxide--ensure perfect dispersion and stability)
  21. what is add blue? what's difference between it with fuel additive?
    • add blue is for SCR, selective catalytic reduction sys, it is (NH2)2CO, it is added after DOC
    • fuel additive is added in fuel tank(i think), it is Fe2O3 or others.
  22. all reaction functions
    • DOC(catalyst): NO+CO->CO2+N2, HC + O2 -> CO2 + H2O, CO + O2 -> CO2
    • DFP(reduce soot)(regeneration):CO+O2->CO2, C+O2-> CO2 [for catalysed filter: C+NO2->CO2+NO, NO+O2->NO2]
    • 3way catalyst oxygen sorageCO+CeO2 ->CeO3+CO2, Ce2O3+O2->CeO2
  23. recently development of FBC:
    • New Eolys: reduce on-board volume, better inter gration, extend maintaenance interval, reduce ash
    • On-Board Multifunction FBC: co-additive: flexible to different fuel qualities
    • new Octosquare design: more ash storage
  24. 1)stability check for FBC,
    2)trap regeneration test
    • 1)the stability is checked by following the evolution of the active matter(Fe-Ce) concentration during ageing test
    • 2)draw profile, important point: start of regeneration, soot burn rat @50%, soot burn rate@100%
    • masure: back pressure
    • criteria: constant back pressure at end of regeneration
  25. effect of FBC
    • loading decrease before regeneration
    • long interval
    • low back P
    • BUT: may reduce regeneration target T ->fuel penalty + oil dilution
  26. comparasion between catalysed DPF and Eoly A-DPF
    • EOLY A-DPF:
    • more contact points with soot, high porous
    • longer regeneration intervals and lower T
    • C-DPF:
    • risk of non homogeneous regeneration:
    • hot spot and future uncontrolled, partial regeneration with DP residual->fuel penalty
    • so, need higher maintenance, secondary emissions
  27. solution for commercial vehicles and heavy duty vehicles(sweeper, excavator, dumper)
    • DPF and DeNOx combination
    • special ECU like plug-in
    • Micro thermal injector
  28. explain how DPF, FBC works
  29. How to make good catalyst