Heat transfer modelling in honeycomb wall-flow diesel particulate filters

Abstract

Heat transfer in wall-flow monoliths has gained in interest because of the widespread adoption of these systems by automotive industry to fulfil soot emission regulations and the importance of heat exchange on the regeneration process control to avoid damaging the monolith. This paper presents a heat transfer model for wall-flow diesel particulate filters coupled with an unsteady compressible flow solver. The heat exchange between the gas and the solid phase is based on a bi-dimensional discretisation of the porous medium both in axial and tangential directions. The monolith can be discretised in the radial direction to account for the heat fluxes towards the environment through the monolith and the canister, which is also coupled with the inlet and outlet ducts of the filter. The model is validated against experimental data obtained in a flow test rig. A test campaign under non-reacting conditions has been conducted to show the capability for thermal response prediction. Tests cover clean and soot loaded monolith, continuous flow under steady and transient thermal conditions, and pulsating flow. In this case, the characteristics of the pressure waves in amplitude and frequency are similar to those that the monolith can undergo depending on its location along the exhaust line.

Experimental assessment of a pre-turbo aftertreatment configuration in a single stage turbocharged diesel engine. Part 2: Transient operation

“…Figure 18(a) shows that the DPF inlet temperature when the mechanical compressor is included is approximately the same as that obtained with the single stage turbocharging architecture, despite of the differences in fuel and mass flow (the same maximum equivalence ratio is kept). The increase of the mass flow across the DPF monolith keeping constant gas temperature reduces the heat transfer due to the lower dwell time [39] and leads to a higher rate of temperature increase at the DOC inlet, as represented in Figure 18(b). As a consequence, the VGT inlet temperature increase is also accelerated.…”

“…The main components of the engine are indicated in Figure 15: cylinders, in which the combustion process is modelled as a function of the crank angle and the engine operating conditions using an interpolation methodology on a rate of heat release database [14]; charge air and EGR coolers, which are modelled as pipe beams with inlet and outlet volumes [35]; specific models for compressors [36] and turbines [37]; and aftertreatment systems with focus on fluid dynamic aspects for accurate pressure drop and acoustic prediction [38] besides the influence of the heat transfer effects [39] and the consideration of clean [40] and soot loaded substrate [41] in the case of the DPF.…”

Analysis of heavy-duty turbocharged diesel engine response under cold transient operation with a pre-turbo aftertreatment exhaust manifold configuration

“…The conductive radial heat transfer [25] is governing this temperature decrease that finally produces the gas temperature drop at the HPT inlet shown in Figure 6(a).…”

“…The solution of the different concentric channel beams is coupled by means of the heat transfer model [25] which accounts for the gas to solid heat exchange in the monolith channels, the thermal inertia and the heat losses towards the environment. Diesel engine with pre-turbo aftertreatment architecture.…”

Application of the two-step Lax and Wendroff FCT and the CE-SE method to flow transport in wall-flow monoliths

“…In the case of the wall-flow DPF, the models are usually simplified to quasi-steady incompressible flow because of the traditional placement of this element at the engine tailpipe [17]. However, the improvement of the wall-flow DPF modelling regarding aspects such as the prediction of the acoustic response [20], the heat transfer [9] or the evaluation of pre-turbo aftertreatment systems [1,2] is leading to the consideration of unsteady and compressible flow effect [16,20].…”