Experimental study of the effect of various collision angles and critical conditions on marine engine’s twin-spray collision process

To enhance the fuel-gas mixing and phase transition process, the fuel is injected by twin injectors in a large-bore low-speed two-stroke marine engine, while the cylinder condition has reached the transcritical and supercritical conditions. The twin-injector configuration has a great potential for further optimization, but the exploration on the outcome of collision and phase transition was still limited. Therefore, this work aims to study the effect of various collision angles (60°, 90°, 120°, 150°) and critical conditions (sub/trans/supercritical) on the twin-spray collision process using optical techniques. A wide range of experimental cases are conducted to provide an analysis and database for future modeling validation. The post-collisional spray structures, spatial distribution, and periphery features are analyzed to characterize the droplet’s collision. The results show that with the collision angle increasing, the higher collision velocity enhances the mass transfer while the minor vertical component results in a smaller axial dispersion. Because of the trade-off relationship between the vertical velocity component and pre-collision penetration, a higher reduction in droplet momentum results in a slighter collision behavior. At the collision angle of 150°, the subcritical condition tends to result in an off-axis collision. Under the transcritical (P) condition, the probability of head-on collision increases and presents a wider spatial distribution. But under the supercritical condition, because of the existence of the liquid collision, the thermal conversion among phases is accelerated, while the ambient resistance is reduced. Moreover, an exponential correlation of collision liquid length is formulated to predict the axial dispersion based on various critical conditions.

Modelling and Dynamic Simulation of One-Dimensional Isothermal Axial Dispersion Tubular Reactors with Power Law and Langmuir-Hinshelwood-Hougen Watson Kinetics

In this paper, the modelling, numerical lumping and simulation of the dynamics of one-dimensional, isothermal axial dispersion tubular reactors for single, irreversible reactions with Power Law (PL) and Langmuir-Hinshelwood-Hougen-Watson (LHHW)-type kinetics are presented. For the PL-type kinetics, first-order and second-order reactions are considered, while Michaelis-Menten and ethylene hydrogenation or enzyme substrate-inhibited reactions are considered for the LHHW-type kinetics. The partial differential equations (PDEs) developed for the one-dimensional, isothermal axial dispersion tubular reactors with both the PL and LHHW-type kinetics are lumped to ordinary differential equations (ODEs) using the global orthogonal collocation technique. For the nominal design/operating parameters considered, using only 3 or 4 collocation points, are found to adequately simulate the dynamic response of the systems. On the other hand, simulations over a range of the design/operating parameters require between 5 to 7 collocations points for better results, especially as the Peclet number for mass transfer is increased from the nominal value to 100. The orthogonal collocation models are used to carry out parametric studies of the dynamic response behaviours of the one-dimensional, isothermal axial dispersion tubular reactors for the four reaction kinetics. For each of the four types of reaction kinetics considered, graphical plots are presented to show the effects of the inlet feed concentration, Peclet number for mass transfer and the Damköhler number on the reactor exit concentration dynamics to step-change in the inlet feed concentration. The internal dynamics of the linear (or linearized) systems are examined by computing the eigenvalues of the linear (or linearized) lumped orthogonal collocation models. The relatively small order of the lumped orthogonal collocation dynamic models make them attractive and useful for dynamic resilience analysis and control system analysis/design studies.

Biosorption of CD2+ and PB2+ with Cocoa Bark: Experimentation, Mathematical Modeling and Simulation Numerical

Cocoa shell is a potential adsorbent for the removal of pollutants from wastewater. The goal of this study was to compare, model and simulate the removal of Pb2+ and Cd2+ in a fixed bed column using cocoa shell. The experimental studies were carried out in a laboratory burette with a bed height of 10.5 cm, a volumetric flow of 2 mL/min, and a metal concentration of 10 mg/L. The empirical models of Thomas, Dose-Response, and Wang were used to study the dynamic behavior of biosorption, in addition a mathematical model based on a differential mass balance of the column was proposed to study the effect of the axial dispersion phenomenon. The results indicated that the active sites of cocoa shell have a higher affinity for the Pb2+ cation, with breakthrough and saturation times higher than Cd2+. The Dose-Response model was the one that presented the best fit with experimental data, confirming that the adsorption capacity of the cocoa shell is superior with Pb2+. The axial dispersion phenomenon is relevant and should not be neglected in the approach of laboratory scale models. Keywords: cocoa shell, biosorption, heavy metals, numerical simulation. Resumen La corteza de cacao es un potencial adsorbente para la eliminación de contaminantes de aguas residuales. El objetivo de este estudio fue comparar, modelar y simular la remoción de Pb2+ y Cd2+ en columna de lecho fijo utilizando corteza de cacao. Los estudios experimentales se llevaron a cabo en una bureta de laboratorio con una altura de lecho de 10.5 cm, flujo volumétrico de 2 mL/min, y concentración de metal de 10 mg/L. Los modelos empíricos de Thomas, Dosis-Respuesta, y Wang fueron usados para estudiar el comportamiento dinámico de la biosorción, adicionalmente un modelo matemático basado en un balance de masa diferencial de la columna fue planteado para estudiar el efecto del fenómeno de dispersión axial. Los resultados señalaron que los sitios activos de la corteza de cacao tienen mayor afinidad por el catión Pb2+, con tiempos de ruptura y saturación superiores a la del Cd2+. El modelo Dosis- Respuesta fue el que presento mejor ajuste con los datos experimentales, confirmando que la capacidad de adsorción de la corteza es superior con Pb2+. El fenómeno de dispersión axial es relevante y no debe ser despreciado en el planteamiento de modelos a escala de laboratorio. Palabras Clave: Corteza de cacao, biosorción, metales pesados, simulación numérica.