Three-dimensional CFD modelling of a photocatalytic parallel-channel microreactor

2021 ◽  
Vol 229 ◽  
pp. 116051
Author(s):  
Ahmed Yusuf ◽  
Giovanni Palmisano
2019 ◽  
Vol 15 (2) ◽  
pp. 246-255
Author(s):  
Tri Ratna Bajracharya ◽  
Rajendra Shrestha ◽  
Ashesh Babu Timilsina

 Pelton turbine is a high head-impulse type turbine. The high-speed jet strikes the symmetrical semi ellipsoidal buckets, thus transferring the momentum within short period of time, impulse. The conversion of potential energy of water to kinetic energy in the form of jet is done by a nozzle with internally fitted spear or needle, the assembly in known as injector. The jet quality includes but is not limited to jet velocity, velocity distribution ‘velocity profile’, core location etc. In this study, the modeling of flow in Pelton turbine injector is done by commercial Computational Fluid Dynamics (CFD) solver on a three-dimensional flow domain. The results obtained from CFD modelling are then compared against the experimental observations and previously published literatures. The jet streamline, jet velocity profile and jet core location are then studied. As observed experimentally, the mean jet diameter reduces as the nozzle opening decreases. In addition, like the experimental observations, the jet first contracts and then expands. The diameter of the contraction is then normalized with nozzle exit diameter and is plotted for both experimental observations as well as the results of the numerical simulation. The maximum error between experimental and numerical analysis of jet contraction is 20%. The jet core is located at region axially ahead of needle tip.


Author(s):  
T. J. Foster ◽  
C. W. Wilson ◽  
M. Pourkashanian ◽  
A. Williams

Aircraft fitted with afterburner systems for increased thrust have been observed to have NOx emissions with a higher proportion of nitrogen dioxide (NO2) than non-augmented aircraft. These emissions are generally characterised by a brown plume and has implications for aircraft visibility and stealth as well as environmental considerations. This paper describes the CFD modelling of NOx emissions from a modern afterburner system with particular emphasis on the formation of nitric oxide (NO) and the subsequent conversion of NO to NO2. A commercial CFD code, was used to solve a three dimensional model of a “burn then mix” afterburner system under investigation. A post processor package has been developed and was used to calculate both NO and NO2 concentrations. Four reheat settings were investigated; minimum, 25%, 50% and maximum reheat. For all conditions investigated the bulk of NOx emission was found in the core, stemming from the vitiated combustor air flow. NOx was also formed in the bypass stream, the production zone was found to be close to the fuel sprayers and flame stabiliser at minimum reheat, but moved downstream towards the exit nozzle as reheat power was increased. The model showed that for all the conditions under investigation, over 90% of the NOx produced in the reheat system was formed via the thermal-NO route. The model has been compared with centre-line traverse data measured at the exit nozzle of the engine on a sea level static test bed. The predicted NOx emissions agreed quantitatively with the experimental measurements to within ± 5%.


2017 ◽  
Vol 212 ◽  
pp. 121-135 ◽  
Author(s):  
Rani Puthukulangara Ramachandran ◽  
Mohsen Akbarzadeh ◽  
Jitendra Paliwal ◽  
Stefan Cenkowski

Author(s):  
Tom Saenen ◽  
John R. Thome

A novel fully dynamic model of a microchannel evaporator is presented. The aim of the model is to study the highly dynamic parallel channel instabilities that occur in these evaporators in more detail. The numerical solver for the model is custom-built and the majority of the paper is focused on detailing the various aspects of this solver. The one-dimensional homogeneous two-phase flow conservation equations are solved to simulate the flow. The full three-dimensional conduction domain of the evaporator is also dynamically resolved. This allows for the correct simulation of the complex hydraulic and thermal interactions between the microchannels that give rise to the parallel channel instabilities. The model uses state-of-the-art correlations to calculate the frictional pressure losses and heat transfer in the microchannels. In addition, a model for inlet restrictions is also included to simulate the stabilizing effect of these components. In the final part of the paper, initial validation results of the model are presented, in which stability results of the model are compared to existing experimental data from literature. Finally, some representative dynamic results are also given to demonstrate some of the unique capabilities of the model.


2021 ◽  
Vol 65 (2-4) ◽  
pp. 330-336
Author(s):  
Camilla Lops ◽  
Nicola Germano ◽  
Sabino Matera ◽  
Valerio D’Alessandro ◽  
Sergio Montelpare

Nowadays, Double Skin Façades (DSFs) are popular technologies adopted for both new and existing buildings. Since their introduction, new configurations and materials started to be tested to improve the DSF energy behaviour and function. Such complex technologies, able to improve comfort conditions of occupied spaces and decrease building energy requirement, are strictly related to the design phase that should be carefully evaluated. The correct prediction of air fluxes inside the DSF cavity, in fact, is highly influenced by the adopted analysis hypothesis and settings. Moreover, the absence of multiple experimental campaigns and empirical validations in the sector represents the major concerns for scientists and researchers. Among the possible numerical approaches for studying DSFs, Computational Fluid Dynamics (CFD) analyses confirm to be the most suitable solution. The CFD modelling activity presented in this paper intends to compare various Double Façade configurations by adopting bi- and three-dimensional domains and different turbulence models. According to the obtained results, 2D simulations can predict airflows inside and around the DSF channel with good approximation and reasonable computational effort. Moreover, the velocity profiles estimated by the turbulence formulations are in good accordance, underling only a few slight variations in proximity to the DSF layers.


2019 ◽  
Author(s):  
CLAUDIA CASTRO-FACCETTI ◽  
DUNCAN BORMAN ◽  
ANDREW SLEIGH ◽  
AMIRUL KHAN ◽  
MÓNICA ELJAIEK-URZOLA

2010 ◽  
Vol 51 (3) ◽  
pp. 110-116 ◽  
Author(s):  
Swati Mohanty ◽  
Tobias Baier ◽  
Friedhelm Schönfeld

Author(s):  
P. Di Martino ◽  
S. Colantuoni ◽  
L. Cirillo ◽  
G. Cinque

A fully-elliptic three dimensional computational fluid dynamic (CFD) code based on pressure-correction techniques has been used in the design of an advanced turbine single annular reverse-flow combustor (AR1600) under development at Alfa Romeo Avio (ARA). Fuel injection was handled using a Lagrangian liquid droplet spray model coupled to the gas phase equations, which are solved in an Eulerian frame of reference. Turbulent transport is described by the standard k-ε model. The combustion model utilizes a conserved scalar formulation and an assumed shape probability density function to account for chemistry-turbulence interaction. The numerical algorithm employs structured nonorthogonal curvilinear grids, node-centered variable arrangement and Cartesian velocity components. The code was validated on a similar combustor (AR318 turboprop engine of 600 SHP). The numerical results agree well with the test measurements available for this chamber. The aerothermal design of AR1600 (1600K exit temperature) has the same gemetrical constraints of AR318 (tip and root diameters for compressor outlet and turbine inlet), but the lenght is shorter to reduce surface area for less cooling and to utilize the excess air for more efficient mixing and combustion.


Sign in / Sign up

Export Citation Format

Share Document