Pressure Drop Analysis of Square and Hexagonal Cellsand its Effects on the Performance of Catalytic Converters

Abstract

Stringent emission regulations around the world necessitate the use of high-efficiency catalytic converters in vehicle exhaust systems. Therefore, determining the optimum geometry of the honeycomb monolith structure is necessary. This structure requires a high surface area for treating gases while maintaining a low pressure drop in the engine. In the present paper, an adapted sub-grid scale modeling is used to predict the pressure loss of square-and hexagonal-cell-shaped honeycomb monoliths. This sub-grid scale modeling represents the actual variations in the pressure drop between the inlet and outlet for various combinations of wall thickness and cell density. A comparison is made between the experimental and numerical results established in literature. The present approach is found to provide better and more comprehensive results than the single channel technique.

Effects of the internal structures of monolith ceramic substrates on thermal and hydraulic properties: additive manufacturing, numerical modelling and experimental testing

“…The model predicts the minimum pressure drop for the lowest flow rate (0.4 kg/h) as 41 Pa with a linear increase of the pressure drop with the increase in the mass flow rate, resulting in pressure drop of 117 Pa at the highest examined flow rate (1.1 kg/ h). Similar trend, where the pressure drop shows a linear dependency to the mass flow rate, is found in the literature [47,57]. It can be concluded that the CFD prediction results for pressure drop agree well with experimentally measured pressure drops.…”

“…13. In the mass flow rate range of interest, the pressure drop of the honeycomb varies linearly with the mass flow rate [47,56,62]. Considering the flow in the honeycomb channels is fully laminar, the viscous effects are the main contributor to the pressure drop in the studied mass flow rate range [60].…”

“…In order to aid the design of the lattice structures, a numerical approach using computational fluid dynamics (CFD) is used to predict the effect of the internal structure of the substrate on fluid dynamics, pressure drop and temperature distribution. The main focus of the numerical study is on the physical behaviour of the flow within the substrate; therefore, the chemical reactions are not taken into the account for simplification and to place the interest strictly on the flow behaviour driven by the geometry change, which is a common practice when investigating fluid flow in substrates [1,30,47]. The main idea is that, with the lattice design, the temperature distribution in radial and axial direction of the substrate will be considerably different than of the traditional honeycomb substrate, concluding that the geometry can influence the temperature distribution.…”

“…The pressure loss of substrates is highly dependent on the channel design, geometry, length, and hydraulic diameter of the channels [47]. The substrates must be designed in a way to offer high surface area for catalytic reactions, low back-pressure, and fast light-off without compromises in mechanical properties.…”

Understanding Flow through Catalytic Converters

“…Flow uniformity was increased by utilizing higher cell density monoliths with smaller hydraulic diameter and by splitting the monolith into two parts separated by a gap [8][9][10][11]. Lower flow uniformity was observed in 3D steady state and transient numerical simulations in systems with higher monolith-to-inlet diameter ratios [12,13].…”