Filtration Efficiency and Pressure Drop Performance of Ceramic Partial Wall Flow Diesel Particulate Filters

International Journal of Engine Research

Payne

2016

The honeycomb monolith is the most prevalent geometry in automotive exhaust aftertreatment, with applications including oxidation catalysts, partial-flow and wall-flow filters. Particle collection mechanisms at the leading edge of honeycomb monoliths and in open channels are usually neglected by engineers of these devices. Under specific conditions however, these phenomena can make an appreciable contribution to overall particle collection and deposits on channel walls may affect catalyst performance. In the current study, experimental measurements of deposit loading, capture efficiency and pressure drop at constant flow conditions are presented for three flow-through monoliths with different cell densities and lengths, while particle distribution is varied in an additional case. The processed results reveal the evolution of deposit distribution at the leading edge, the entry zone inside the channel and the remaining part of the monolith. Next a one-dimensional transient mathematical model is proposed, which takes into account interception at the edge and coupled diffusion-interception inside the channel. After fitting the model parameters, all experimental cases are predicted with sufficient accuracy with the exception of loadings extended beyond 12 hours. Finally, further application of the model reveals the negative effect of flow rate on collection efficiency and the potential to maximize or minimize collection efficiency using various cell designs.

Section: Experimental Results and Model Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental testing and mathematical modelling of diesel particle collection in flow-through monoliths

International Journal of Engine Research

Payne

2016

“…Mathematical modelling has also been used in damaged PF studies, 15–17 employing the well-validated model of Bissett and Shadman model 18,19 with modifications only in the boundary conditions. 20–22 The main assumption is that particles follow the exhaust gas streamlines and thus are collected when flow is diverged through the wall. Using this model, Haralampous and Dritselis 17 calculated axial deposit profiles and filtration efficiency maps for the complete engine operation range.…”

Section: Introductionmentioning

confidence: 99%

Filtration efficiency and pressure drop modelling of particulate filters with rear plug damage

International Journal of Engine Research

Μαστρόκαλος

Tzorbatzoglou

2020

A model suitable for wall-flow particulate filters with partial rear plug damage is developed and experimentally validated in this work. A ceramic filter with 16% of the rear plugs mechanically removed is tested at steady-state conditions on the engine bench and transient driving cycle conditions on the chassis dynamometer. After decanning of the monolith, destructive analysis is conducted to identify deposit loading variations and scanning electron microscopy is used to study the deposit structures in the channels. It is shown that channels without rear plugs develop distinct deposit structures in the entry zone. Hence, a local pressure loss coefficient is applied to model the effect of entrance flow constrictions, taking also into account deposit restructuring phenomena at higher flow rates. In addition, a deep-bed filtration submodel is used to capture the effect of non-uniform wall velocities on deposit accumulation in the wall. The modified model is first fitted to the engine bench data and then validated in a wider range of conditions using the driving cycle tests. With the exception of prolonged steady-state loading conditions, good pressure drop and filtration efficiency predictions are obtained throughout the tests in conjunction with correct deposit property profiles. Notably, the cold-start worldwide harmonized light vehicles test cycle shows that the current European on-board diagnosis threshold limit for particulate mass is too relaxed to trigger a malfunction indication for moderate filter faults. In conclusion, the model can be applied in damaged particulate filter studies for the assessment of leaked particulate mass, the specification of more effective legislation limits and the development of rigorous on-board diagnosis systems and algorithms.

“…For example, Samaras [21] and Finch et al [22] showed that monitoring of the back-pressure in failed PFs, in which the rear plugs were removed artificially, is not adequate for on-board diagnostic purpose. There are also some numerical works utilizing 1D models for flawed PFs without rear plugs [23][24][25][26]. The above-mentioned studies rely on the initial work of Bisset [1] and incorporate proper model adjustments to account for the missing plugs.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Flow and Particle Deposition in Wall-Flow Filters with Intact or Damaged Exit

Tzorbatzoglou

Μαστρόκαλος

2019

Fluids

We examine the time-dependent three-dimensional gas-particle flow in an intact wall-flow filter consisting of channels alternatively plugged at each end and a partially damaged filter in which the rear plugs are removed. Our focus is placed on highlighting the differences in the flow pattern and the deposition process between the two geometries. The Navier–Stokes equations are solved for the fluid flow coupled with a Brinkman/Forchheimmer model in order to simulate the flow in the porous walls and plugs. Discrete particle simulation is utilized to determine the nanoparticle trajectories. Using this scheme, we are able to characterize the main features of the flow fields developing in the intact and damaged filters with respect to the Reynolds number and identify those affecting the transport and deposition of particles that have three representative response times. We present fluid velocity iso-contours, which describe the flow regimes inside the channels, as well as in regions upstream and downstream of them. We provide evidence of local recirculating bubbles at the entrance of the channels and after their exit, whereas back-flow occurs in front of the rear plugs of the intact channels. We show that the flow leaves the channels as strong jets that may break up for certain flow parameters, leading to turbulence with features that depend on the presence of the rear plugs. The removal of the rear plugs affects the flow distribution, which, in turn influences the flow rates along the channels and through the walls. We describe the particle trajectories and the topology of deposited particles and show that particles follow closely the streamlines, which may cross the surface of permeable walls for both flow configurations. The distribution of deposited particles resembles the spatial variation of the through-wall flow rate, exhibiting two peak values at both ends of the intact filter channel, and one local maximum near the entrance of the damaged filter channel that is diminished at the exit. We also investigate in detail the particle deposition on the frontal face and indicate that particle accumulation at the edges of the entrance is favored for particles with low response times in flows with high fluid mass rates for both intact and damaged filters. Finally, we examine the filtration efficiency for the defective channels without rear plugs and show that fewer particles are captured as the Reynolds number is increased. A smaller reduction of the filtration efficiency is also predicted with increasing particle size.