Modelling wall-flow diesel particulate filter regeneration processes

This research was aimed at providing a better understanding of regeneration processes in wall-flow diesel particulate filters (DPFs), with emphasis on the combustion of particulate matter (PM). A 1-D model was used to investigate the effects of inherent PM properties on DPF regeneration behaviour. These properties were mean particulate diameter, porosity and bulk density of the PM, as well as the kinetic parameters of PM oxidation, i.e. frequency factor and activation energy. A parametric study showed that the activation energy of the PM oxidation reaction was the most important parameter and this was followed by the associated frequency factor, bulk density and porosity and mean particulate diameter. Due to the importance of the kinetic parameters of the PM oxidation reactions, a new 1-D model with a multi-step reaction scheme that required no tuneable kinetic parameters for the PM oxidation reactions was developed. [Continues.

A diesel particulate filter regeneration model with a multi-step chemical reaction scheme

Diesel particulate filters (DPFs) are considered necessary in order to meet future global diesel engine emissions legislation. Various regeneration methods have been developed to clean DPFs by periodic oxidation of trapped particulate matter (soot). To achieve this goal, it is important to understand the fundamentals of the regeneration process. Previous soot oxidation regeneration models relied on tunable chemical kinetic parameters to achieve agreement between model and experimental results. In the work reported in this paper, a multistep chemical reaction scheme is incorporated in a model to study the thermal regeneration process. The regeneration model does not require tunable parameters and its results compare well with experimental findings. The effects on regeneration of various gas species are also studied, in addition to O2 and N2, such as CO and H2O that are present in the exhaust gas. The model is also used to demonstrate the effects of quenching the regeneration process and its impact on partial filter regeneration

The effects of soot properties on the regeneration behaviour of wall-flow diesel particulate filters

In recent years, significant effort has been put into studying the regeneration process of diesel particulate filters (DPFs) either through experiments or modelling. However, less attention is paid to understanding the important influence of soot properties on the regeneration process. In this paper, for the first time, five fundamental soot properties, namely activation energy, frequency factor of the reaction, soot bulk density, porosity and mean soot particulate diameter, are investigated. Sensitivity analyses are carried out for each of these parameters based on a one-dimensional generalized DPF regeneration model. It is found that activation energy is the most important factor in the regeneration process, followed by frequency factor, bulk density, porosity and mean particulate size. In addition, the results also indicate that the concentration of exhaust gas oxygen has a significant influence on the role played by each parameter. This clearly shows the importance of gas diffusion in the regeneration process

A finite-volume-based two-dimensional wall-flow diesel particulate filter regeneration model

Many existing diesel particulate filter (DPF) models do not sufficiently describe the actual physiochemical processes that occur during the regeneration process. This is due to the various assumptions made in the models. To overcome this shortcoming, a detailed twodimensional DPF regeneration model with a multistep chemical reaction scheme is presented. The model solves the variable density, multicomponent conservation equations by the pressure implicit with splitting of operators (PISO) scheme for inlet and outlet channels as well as the porous soot layer and filter wall. It includes a non-thermal equilibrium (NTE) model for the energy equation for porous media. In addition, for the first time, experiments on the DPF were conducted to determine the interstitial heat transfer coefficient inside the DPF porous wall. The results compare well with an in-house one-dimensional model and subsequently this was used in the new two-dimensional model. By using this detailed two-dimensional model, some interesting observations of the DPF regeneration process were revealed. These included flow reversals and asymmetry in the filter channels

An optimization framework for sandstone acidizing using design of experiment (DOE) and mathematical modelling

Fluoroboric acid (HBF4) serve as one of the alternatives for conventional mud acid in the application of sandstone wells stimulation. Various parameters such as formation temperature and acid injection velocity would significantly affect the performance of sandstone acidizing and hence determine the success rate of well stimulation. It is therefore undeniable that a deep understanding of the effects of these major parameters are of paramount importance. However, there is a scarcity of data available in the literature regarding the use of HBF4 in sandstone acidizing in comparison to the use of mud acid. In this work, an optimization framework is developed to study the combined effects of formation temperature and acid injection velocity to the change in porosity and pressure drop. Apart from porosity improvement, a pressure drop across the sandstone core would also give an indication to the acidizing performance. The optimization approach is achieved by using design of experiment (DOE) and response surface methodology, coupled with a mechanistic model for sandstone acidizing. The design of experiment used in this work is central composite design (CCD). Meanwhile, the mechanistic model that simulate a flow in porous media is being developed using COMSOL Multi-physics, which is a computational fluid dynamics (CFD) software that uses finite element method (FEM). In this optimization tool, a range of formation temperature was set between 41˚C and 88˚C, whereas the range of acid injection velocity was set between 1.79×10-5 m/s to 3.78×10-5 m/s. According to the results, the optimum condition studied was found out to be 88˚C and 3.78×10-5 m/s. Under such an operating condition, the favourable maximum porosity enhancement and pressure drop profile were obtained. The maximum porosity and pressure drop were up to 17% and 16.6979 kPa respectively. The porosity enhancement and pressure drop in the sandstone core showed an excellent agreement with the data predicted by the model. In general, this optimization study had proven that response surface methodology (RSM) could be applied to determine the acid performance in sandstone acidizing

Synthesis and Antifungal Evaluation of Magnetic Magnesium Oxide Nanoparticles Against Fusarium Oxysporum

Hybrid nanoparticles (NPs) have received much interest over the past decades because they have the potential to overcome the limits of single-component particles. This study proposes a hybrid magnetic magnesium oxide (m-MgO) NPs to combat the plant pathogenic fungus, Fusarium oxysporum (F. oxysporum). The m-MgO NPs were synthesized via ultrasonic mediated sol-gel method. UV-visible spectrometry confirms the successful formation of m-MgO NPs. In addition, the magnetic activity of m-MgO NPs was illustrated through a preliminary magnetic activity study. A disc diffusion assay was carried out to determine the effectiveness of m-MgO NPs to inhibit the growth of F. oxysporum. The results showed that the zone of inhibition was 7.58 ± 0.30 mm at 10 mg/mL, suggesting that the synthesized m-MgO NPs are an effective fungicide to inhibit the growth of F. oxysporum

Performance Enhancement of VAWT using Diffuser for Energy Extraction from Cooling Tower Exhaust Air

Renewable energy generation need to be accelerated to battle climate change and depletion of fossil fuel resources. Innovation to design wind recovery system which are efficient is vital to contribute green energy production. Many advancements in vertical axis wind turbines (VAWT) were made over the years however, it is still not as efficient as conventional turbines, and some countries does not have the luxury of strong consistent wind throughout the year. Therefore, this study focuses on extracting wind energy from unnatural sources, specifically for cooling tower exhaust air energy recovery. In this study, cycloidal diffuser with different shroud lengths was used to study the performance of a 3-bladed H-Darrieus VAWT (HDWT) with S-1046 airfoils under accelerated wind conditions in a 3-dimensional numerical study using shear stress transport k-ω turbulence model. The cycloidal diffuser with shroud length of 0.48D increased the HDWT power coefficient by 26.66% compared to the bare HDWT at tip speed ratio of 2.0. Aerodynamics around the energy extractor system was also discussed and this investigation has provided good understanding of the flow behaviour of the wind augmented HDWT under cooling tower exhaust air

Numerical simulation and experimental validation of microwave torrefaction for empty fruit bunches pellet

This study investigates the microwave heating and torrefaction process of empty fruit bunch (EFB) pellets. Finite element based COMSOL Multiphysics software was used to predict the microwave heating behaviour of EFB pellets during the torrefaction process. The simulated temperature data from multimode microwave system at 2.45 GHz frequency was used to compare and validate the experimental results. Quantitative validation of 10 min temperature profiles between 25-300 °C was performed by comparing the simulated and experimental results. RMSE and maximum different temperature profile were 16.42 and 38°C respectively which may cause by the moisture of pellet, exothermic reaction and placement of the thermocouple during microwave torrefaction process. The simulation work has successfully identified the hot spots of EFB pellets during microwave torrefaction. Hot spot happened in the temperature range of 250-450 °C and was observed near the waveguide and centre of the EFB pellets bed. This study provided a framework and required model parameters to predict temperature profile and hot spot location for a specific geometry of microwave cavity

Modelling wall-flow diesel particulate filter regeneration processes

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