Modeling and experimental validation of subgrid scale scalar variance at high Schmidt numbers

Molybdenum Disulphide Precipitation in Jet Reactors: Introduction of Kinetics Model for Computational Fluid Dynamics Calculations

In our previous work, we used the population balance method to develop a molybdenum disulphide kinetics model consisting of a set of differential equations and constants formulated to express the kinetics of complex chemical reactions leading to molybdenum disulphide precipitation. The purpose of the study is to improved the model to describe the occurring phenomena more thoroughly and have introduced computational fluid dynamics (CFD) modelling to conduct calculations for various reactor geometries. CFD simulations supplemented with our nucleation and growth kinetics model can predict the impact of mixing conditions on particle size with good accuracy. This introduces another engineering tool for designing efficient chemical reactors.

Rheological Properties of Engine Oil with Nano-Additives Based on MoS2 Materials

To enhance oil’s tribological and rheological properties, various nano-additives are used. An example of such a nano-additive is nanosized molybdenum disulfide (MoS2). Due to its unique properties, MoS2-based materials used as lubricants have attracted significant attention. In our previous work, we developed a novel, scalable, and low-cost method for MoS2-based materials production using an impinging jet reactor. Hybrid nanostructures based on MoS2 and carbon nanomaterials (MoS2/CNMs) decreased the friction factor of the base oil. In the present study, a mathematical model that accounts for the viscous heating effects in rheograms was formulated. The model was used to interpret the results of rheological measurements conducted for the base oil 10W40 and its mixtures with different nanosized lubricant additives. The model of the non-isothermal Couette flow allowed us to correct the rheograms of the engine oils in the region of high shear rates where viscous heating effects become significant. The temperature correlations for the consistency and flow behavior indexes were proposed. The nanohybrid suspensions of MoS2 in the base oil were found to have the lowest apparent viscosity at low temperatures, typical for the cold engine startup.

Production and Properties of Molybdenum Disulfide/Graphene Oxide Hybrid Nanostructures for Catalytic Applications

Molybdenum disulfide (MoS₂) can be an excellent candidate for being combined with carbon nanomaterials to obtain new hybrid nanostructures with outstanding properties, including higher catalytic activity. The aim of the conducted research was to develop the novel production method of hybrid nanostructures formed from MoS₂ and graphene oxide (GO). The nanostructures were synthesized in different weight ratios and in two types of reactors (i.e., impinging jet and semi-batch reactors). Physicochemical analysis of the obtained materials was carried out, using various analytical techniques: particle size distribution (PSD), thermogravimetric analysis (TGA), FT-IR spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Due to the potential application of materials based on MoS₂ as the catalyst for hydrogen evolution reaction, linear sweep voltammetry (LSV) of the commercial MoS₂, synthesized MoS₂ and the obtained hybrid nanostructures was performed using a three-electrode system. The results show that the developed synthesis of hybrid MoS₂/GO nanostructures in continuous reactors is a novel and facile method for obtaining products with desired properties. The hybrid nanostructures have shown better electrochemical properties and higher onset potentials compared to MoS₂ nanoparticles. The results indicate that the addition of carbon nanomaterials during the synthesis improves the activity and stability of the MoS₂ nanoparticles.

Large Eddy Simulations of Reactive Mixing in Jet Reactors of Varied Geometry and Size

We applied large eddy simulation (LES) to predict the course of reactive mixing carried out in confined impinging jet reactors (CIJR). The reactive mixing process was studied in a wide range of flow rates both experimentally and numerically using computational fluid dynamics (CFD). We compared several different reactor geometries made in different sizes in terms of both reaction yields and mixing efficiency. Our LES model predictions were validated using experimental data for the tracer concentration distribution and fast parallel chemical test reactions, and compared with the k-ε model supplemented with the turbulent mixer model. We found that the mixing efficiency was not affected by the flow rate only at the highest tested Reynolds numbers. The experimental results and LES predictions were found to be in good agreement for all reactor geometries and operating conditions, while the k-ε model well predicted the trend of changes. The CFD method used, i.e., the modeling approach using closure hypothesis, was positively validated as a useful tool in reactor design. This method allowed us to distinguish the best reactors in terms of mixing efficiency (T-mixer III and V-mixer III) and could provide insights for scale-up and application in different processes.