Effect of Superficial Gas Velocity on the Solid Temperature Distribution in Gas Fluidized Beds with Heat Production
The hydrodynamics and heat transfer of cylindrical gas–solid fluidized beds for polyolefin production was investigated with the two-fluid model (TFM) based on the kinetic theory of granular flow (KTGF). It was found that the fluidized bed becomes more isothermal with increasing superficial gas velocity. This is mainly due to the increase of solids circulation and improvement in gas solid contact. It was also found that the average Nusselt number weakly depends on the gas velocity. The TFM results were qualitatively compared with simulation results of computational fluid dynamics combined with the discrete element model (CFD-DEM). The TFM results were in very good agreement with the CFD-DEM outcomes, so the TFM can be a reliable source for further investigations of fluidized beds especially large lab-scale reactors
DEM modeling and simulation of a catalytic gas–solid fluidized bed reactor: a spouted bed as a case study
A combined model of discrete element method (DEM) and mass transfer was developed for investigating the local mass transfer throughout a catalytic gas–solid fluidized bed reactor. The mathematical models are based on the equations of mass conservation coupling with the equations of gas and particle motion. The realistic model of DEM, which calculates the contact force acting on the individual particles, is used for monitoring the movement of individual particles in the bed. The contact force is calculated from the concept of spring, dash-pot and friction slider. The flow field of gas is predicted by the Navier–Stokes equation. This DEM-mass transfer model provides the information regarding the particle movement and distribution, gas velocity, gas holdup, and conversion profiles in the bed. A spouted bed reactor for decomposition of ozone on oxide catalyst was chosen as a case study. It was found that the ozone conversion is non-uniform in the bed with very low values near the center but high near the wall. The simulation results show very good agreement with the experimental results of Rovero and co-workers and are in better agreement than the results obtained from the one-dimensional model developed by Mathur and Lim.
Computer-Aided System of Virtual Testing of Gas Turbine Engines
The article describes the concept of a virtual lab that includes subsystem of gas turbine engine simulation, subsystem of experiment planning, subsystem of measurement errors simulation, subsystem of simulator identification and others. The basis for virtual lab development is the computer-aided system of thermogasdynamic research and analysis “ASTRA”. The features of gas turbine engine transient modes simulator are described. The principal difference between the simulators of transient and stationary modes of gas turbine engines is that the energy balance of the compressor and turbine becomes not applicable. The computer-aided system of virtual gas turbine engine testing was created using the developed transient modes simulator. This system solves the tasks of operational (throttling, speed, climatic, altitude) characteristics calculation, analysis of transient dynamics and selection of optimal control laws. Besides, the system of virtual gas turbine engine testing is a clear demonstration of gas turbine engine working process and the regularities of engine elements collaboration. The interface of the system of virtual gas turbine engine testing is described in the article and some screenshots of the interface elements are provided. The developed system of virtual gas turbine engine testing provides means for reducing the laboriousness of gas turbine engines testing. Besides, the implementation of this system in the learning process allows the diversification of lab works and therefore improve the quality of training.