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11.
Biodiesel usage at low temperature
Breda Kegl, 2008, izvirni znanstveni članek

Ključne besede: internal combustion engines, buses, biodiesel fuel, rapeseed oil, fuel injection system, low temperatures
Objavljeno: 01.06.2012; Ogledov: 859; Prenosov: 62
URL Povezava na celotno besedilo

12.
Simplified modeling of detailed chemistry description in premixed turbulent combustion by BEM
Niko Samec, Leopold Škerget, 2002, izvirni znanstveni članek

Opis: A simplified modeling of premixed turbulent combustion based on detailed chemical kinetics and simplified mixing is presented. The main conservation equations of mass energy and species mass have been solved numerically applying boundary doma integral method for diffusive coonective transport equation with constant and linear source term. The model has been applied to the particular case of the premixed charge in a spark-ignited internal combustion engine. The model predictions are in good agreement with measurements.
Ključne besede: combustion, turbulence, numerical modelling, boundary element method, internal combustion engines
Objavljeno: 01.06.2012; Ogledov: 751; Prenosov: 52
URL Povezava na celotno besedilo

13.
Numerical and experimental study of water/oil emulsified fuel combustion in a diesel engine
Niko Samec, Breda Kegl, Robert W. Dibble, 2002, izvirni znanstveni članek

Opis: Numerical and experimental studies were made on some of the chemical and physical properties of wateržoil emulsified fuel (W/OEF) combustion characteristics. Numerical investigations of W/OEF combustion's chemical kinetic aspects have been performed by simulation of water/n-heptane mixture combustion, assuming a model of a homogenous reactor's concentric shells. The injection and fuel spray characteristics are analyzed numerically also in order to study indirectly the physical effects of water present in diesel fuel during the combustion process. The experimental results of W/OEF combustion in the DI diesel engine are also presented and discussed. The results of engine testing in a broad field of engine loads and speeds have shown a significant pollutant emission reduction with no worsening of specific fuel consumption.
Ključne besede: internal combustion engines, Diesel engines, combustion, emissions, numerical modelling
Objavljeno: 01.06.2012; Ogledov: 1231; Prenosov: 65
URL Povezava na celotno besedilo

14.
Calculation of thermophysical and thermochemical properties during hydrocarbon combustion
Jurij Avsec, Franc Zgaga, Milan Marčič, 2002, izvirni znanstveni članek

Opis: A mathematical model is presented for computing the chemical and thermophysical properties in the process of combustion of natural gas. To identify the parameters of state of combustion products, their composition hasto be known, which may be determined from chemical equilibrium. The computation is performed with the use of chemical potentials and statistical thermodynamics, featuring all important molecular contributions (translation, rotation, vibration, and intermolecular potential energy). A thermal equation of state with two virial terms is used. The real gas mixture is treated as consisting of four components: carbon dioxide, nitrogen, carbon monoxide, and water. Virial coefficients are dependent on temperature and mole fractions of the real components. Mixed terms are taken into account. The caloric equation of state is based on statistical thermodynamics for an ideal gas. Corrections are made in accordance with the second law of thermodynamics and the thermal equation of state. As the whole computation is based on matrix algebra, increasing the number of components presents no problems. We tested our model in the high-pressure region (100 bar) and the low-pressure region (1 bar), in the temperature range 500 - 6000°K. Our model is compared with other analytical models presented in the literature and shows relatively good agreement. At the same time we tested the influence of real conditions on the chemical and thermophysical properties of combustion products.
Ključne besede: statistical thermodynamics, thermodynamical properties, combustion of natural gas, mathematical models, thermodynamic functions of state, equation of state, virial coefficients
Objavljeno: 01.06.2012; Ogledov: 1185; Prenosov: 67
URL Povezava na celotno besedilo

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Experimental investigation review of biodiesel usage in bus diesel engine
Breda Kegl, Marko Kegl, 2017, izvirni znanstveni članek

Opis: This paper assembles and analyses extensive experimental research work conducted for several years in relation to biodiesel usage in a MAN bus Diesel engine with M injection system. At first the most important properties of the actually used neat rapeseed biodiesel fuel and its blends with mineral diesel are discussed and compared to that of mineral diesel. Then the injection, fuel spray, and engine characteristics for various considered fuel blends are compared at various ambient conditions, with special emphasis on the influence of low temperature on fueling. Furthermore, for each tested fuel the optimal injection pump timing is determined. The obtained optimal injection pump timings for individual fuels are then used to determine and discuss the most important injection and combustion characteristics, engine performance, as well as the emission, economy, and tribology characteristics of the engine at all modes of emission test cycles test. The results show that for each tested fuel it is possible to find the optimized injection pump timing, which enables acceptable engine characteristics at all modes of the emission test cycles test.
Ključne besede: bus diesel engine, fuel injection, fuel spray, combustion, emission, engine performance, tribology characteristics, optimized injection pump timing
Objavljeno: 07.07.2017; Ogledov: 359; Prenosov: 202
.pdf Celotno besedilo (3,81 MB)
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18.
Analysis of the effect of the swirl flow intensity on combustion characteristics in liquid fuel powered confined swirling flames
Marko Klančišar, Tim Schloen, Matjaž Hriberšek, Niko Samec, 2016, izvirni znanstveni članek

Opis: This article examines the implementation of CFD technology in the design of the industrial liquid fuel powered swirl flame burner. The coupling between the flow field and the combustion model is based on the eddy dissipation model. The choice of the LES (Large Eddy Simulation) turbulence model over standard RANS (Reynolds Averaged Navier-Stokes) offers a possibility to improve the quality of the combustion-flow field interaction. The Wall Adapting Local Eddy-Viscosity (WALE) sub-grid model was used. The reaction chemistry is a simple infinitely fast one step global irreversible reaction. The computational model was setup with the Ansys-CFX software. Through the detailed measurements of industrial size burner, it was possible to determine the natural operational state of the burner according to the type of fuel used. For the inlet conditions, axial and radial velocity components were calculated from known physical characteristics of both the fuel and air input, with the initial tangential velocity of the fuel assumed as 18% of the initial axial fuel velocity. Different swirl number (S) values were studied. Addition of a surplus (in comparison to conventional flame stabilization) of tangential air velocity component (W), the rotational component increases itself with a considerably high magnitude, contributing to the overall flame stabilization. The level of S especially influences the turbulent energy, its dissipation rate and turbulent (Reynolds) stresses. In the case of high swirl number values (S > 0,65) it is possible to divide the flow field in three principle areas: mixing area (fuel-air), where exothermal reactions are taking place, central recirculation area and outer recirculation area, which primarily contains the flow of burnt flue gases. The described model was used to determine the flow and chemical behavior, whereas the liquid atomization was accounted for by LISA (Linear Instability Sheet Atomization) model incorporating also the cavitation within injection boundary condition. The boundary conditions were determined based on the data from the experimental hot water system. Depending on system requirements, especially with continuous physical processes as well as the results of experimental measurements, the paper reports on determination of the mixing field and its intensity in the turbulent flow, the description of heat release and interaction of turbulent flow field and chemical kinetics in the case of confined swirling flames.
Ključne besede: CFD, fluid dispersion, combustion, industrial burner, confined swirling flame, two-phase flow
Objavljeno: 04.08.2017; Ogledov: 559; Prenosov: 228
.pdf Celotno besedilo (1,08 MB)
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