The presented work focuses on numerical and experimental analyses of biodiesel fuel's influence on the injection characteristics of a mechanically-controlled injection system, and on the operating conditions of aheavy-duty diesel engine. Addressed are mineral diesel fuel and neat biodiesel fuel made from rapeseed oil. The influence of biodiesel on mechanically controlled injection system characteristics was tested experimentally on an injection system test-bed. The injection test-bed was equipped with a glass injection chamber in order to observe the development of the fuel-spray by using a high-speed camera. The results of the experimental measurements were compared to the numerical results obtained by using our own mathematical simulation program. This program has been used to analyze the influences of different fuel properties on the injection systemćs characteristics. The photos taken with a high-speed camera were compared to the simulation results obtained by using the AVL FIRE 3D CFD simulation program. This software was used to simulate the fuel-spray development during different stages of the injection process. Furthermore, the influence of biodiesel fuel on the engine operating condition of a heavy-duty diesel engineand its' emission formation was tested experimentally on an engine test-bed, and numerically by using the AVL BOOST software. It was found out that the tested biodiesel could be used as an alternative fuel for heavy-duty diesel engines.
COBISS.SI-ID: 17091350
Turbulent flow over various geometries is studied numerically. Incompressible set of Navier–Stokes equations is considered and solved by boundary domain integral method (BDIM). Governing equations are written in velocity–vorticity form. Turbulence models used are based on eddy-viscosity hypothesis. Integral form of equations, discretization and the solution algorithm are presented. The algorithm is tested with two separate test cases. The first is the turbulent channel flow for two different Reynolds numbers: Reτ=180 and Reτ=395. Results show very good agreement with corresponding DNS data. The second test case is the flow over backward facing step for Reynolds number Reh=5000, which shows good agreement with literature data on mean reattachment length.
COBISS.SI-ID: 17349910
In this paper acceleration and computer memory reduction of an algorithm for the simulation of laminar viscous flows and heat transfer is presented. The algorithm solves the velocity-vorticity formulation of the incompressible Navier-Stokes equations in 3D. It is based on a combination of a subdomain boundary element method (BEM) and single domain BEM. The CPU time and storage requirements of the single domain BEM are reduced by implementing a fast multipole expansion method. The Laplace fundamental solution, which is used as a special weighting function in BEM, is expanded in terms of spherical harmonics. The computational domain and its boundary are recursively cut up forming a tree of clusters of boundary elements and domain cells. Data sparse representation is used in parts of the matrix, which correspond to boundary-domain clusters pairs that are admissible for expansion. Two 3D benchmark numerical examples are used: the lid-driven cavity and the onset of natural convection in a differentially heated enclosure.
COBISS.SI-ID: 13066774
The paper studies the properties and sedimentation characteristics of sludge flocs, as they appear in biological wastewater treatment (BWT) plants. The flocs are described as porous and permeable bodies, with their properties defined based on conducted experimental study. The derivation is based on established geometrical properties, high-speed camera data on settling velocities and non-linear numerical model, linking settling velocity with physical properties of porous flocs. The numerical model for derivation is based on generalized Stokes model, with permeability of the floc described by the Brinkman model. As a result, correlation for flocs porosity is obtained as a function of floc diameter. This data is used in establishing a CFD numerical model of sedimentation of flocs in test conditions, as recorded during experimental investigation. The CFD model is based on Euler-Lagrange formulation, where the Lagrange formulation is chosen for computation of flocs trajectories during sedimentation. The results of numerical simulations are compared with experimental results and very good agreement is observed.
COBISS.SI-ID: 14734358
Visualisation of a flow field was performed within the rotor blade passage of anaxial flow fan operating under rotating stall conditions. A PIV system was used to capture the velocity field at an 80% span of the rotor blade. PIV triggering was synchronized with the observed bladesʼ passing, and over 1000 PIV images were obtained. These were then phase-locked averaged, and a sequence of 36 images was composed. The successive images represented the evolution of a flow field within the blade passage with 10° angular steps and made it possible for the structure and behaviour of the flow within the rotor blade passage to be analysed under rotating stall conditions. The initiation and development of flow distortion were clearly shown to be influenced by the advance of the rotating stall cell and the restoration of normal flow with the rotating stall cell moving away.
COBISS.SI-ID: 17444118