Sökning: "Premixed"

Visar resultat 21 - 25 av 149 avhandlingar innehållade ordet Premixed.

1. 21. Detailed Numerical Simulations of Turbulent Premixed Flames at Moderate and High Karlovitz Numbers

   Författare :Henning Carlsson; Strömningsteknik; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Direct numerical simulation; Large eddy simulation; Turbulent premixed combustion; Flow-flame interaction; High Karlovitz number;

   Sammanfattning : In generally accepted and applied flamelet combustion models, a turbulent flame is mainly assumed distorted by the large-scale turbulence eddies, whereas small-scale turbulence effects on the local flamelet structures are neglected. However, in a lot of industrial applications rather high turbulent intensities are often imposed, which induce turbulence scales at ranges smaller than the flame thickness. LÄS MER

3. 22. On the Impact of Piston Motion and In-Cylinder Charge Composition on Energy Release, Auto Ignition and Emission Formation in Premixed Charge Internal Combustion Engines

   Författare :Ola Stenlåås; Förbränningsmotorer; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; bränslen; sprängämnen; Carbochemistry; petrochemistry; fuels and explosives technology; Petrokemi; Internal Combustion Engine; Emission; SI; Spark Ignition; HCCI; Homogeneous Charge Compression Ignition; zone model; Chemical Kinetic; Engine simulation; Reformed Methanol; Hydrogen; Knock; Auto Ignition; NO; Piston Motion; Nitric Oxide; Premixed Charge;

   Sammanfattning : The results presented in this thesis can be divided into four areas of investigation: Investigation of the effect of new volume-crank angle relations on engine emissions, power and efficiency; investigation of nitrogen oxides effect on auto ignition and knock in SI engines; investigation of premixed SI and HCCI engine operation with the alternative fuels hydrogen and reformed methanol gas (RMG); software development of a detailed chemical kinetics zonal engine model. Model development of the in-house two-zone chemical kinetic code focused on expansion of the Jacobian matrix to allow simulations of variable in-cylinder charge. LÄS MER

4. 23. Turbulent premixed flames in a model gas turbine combustor: fuel sensitivity and flame dynamics

   Författare :Francesco Pignatelli; Strömningsteknik; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Fuel flexibility; Premixed turbulent combustion; DNS; Optical diagnostic;

   Sammanfattning : The demand for energy security and reduction of greenhouse gas emissions has led to a surge of interest in the development of high-efficiency and low-emission gas turbine engines that can run on alternative low carbon content fuels, such as hydrogen-enriched fuel and syngas. However, the combustion characteristics of these fuels can significantly alter the flame characteristics and operability range of existing combustors. LÄS MER

5. 24. Fundamental studies of non-premixed combustion in turbulent wall jets using direct numerical simulation

   Författare :Zeinab Pouransari; V. Arne Johansson; Christer Fureby; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Turbulence; non-premixed combustion; global reaction; direct numerical simulation; wall-jet; heat release; mixing scales; heat transfer; Other engineering mechanics; Övrig teknisk mekanik;

   Sammanfattning : The present thesis deals with the fundamental aspects of turbulent mixingand non-premixed combustion in wall-jet flows. Direct numerical simulations(DNS) of compressible turbulent flows are performed in a wall-jet configura-tion, which has a close resemblance to many industrial combustion applica-tions. LÄS MER

7. 25. Modelling effects of flame development on stationary and oscillating premixed turbulent combustion

   Författare :Pratap Sathiah; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; flame development; Keywords: Premixed turbulent flame; Flame Speed Closure model;

   Sammanfattning : The vast majority of contemporary models of premixed turbulent flames applied to multi-dimensional RANS numerical simulations of combustion in gas turbine engines and aero-engine afterburners focus on fully-developed flames, characterized by fully-developed turbulent diffusivity, thickness, and burning velocity. However, abundant experimental data obtained from statistically stationary premixed flames clearly show that a typical turbulent flame develops as it is convected by mean flow from a stabilization zone. LÄS MER