Sökning: "Zonal modeling"

Visar resultat 1 - 5 av 6 avhandlingar innehållade orden Zonal modeling.

1. 1. Development of Zonal Models for Analysis of Engine Knock

   Författare :Shahrokh Hajireza; Värmeöverföring; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; homogeneous autoignition; engine knock; Zonal modeling; SI engine; hot-spot autoignition; exothermic centers; wall heat transfer; application of detailed chemical kinetic mechanism of n-heptane and iso-octane; Motors and propulsion systems; Motorer; framdrivningssystem;

   Sammanfattning : Autoignition in SI engines is an abnormal combustion mode and may lead to engine knock which is an undesired phenomenon in SI engines. It may cause damage and it is a source of noise in engines. Knock limits the compression ratio of the engine and a low compression ratio means low fuel conversion efficiency of the engine. LÄS MER

3. 2. Transonic flow: large eddy simulation, numerical methods and subgrid modeling

   Författare :Christian Wollblad; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; LES; SGS modeling; Transonic flow; semi-implicit numerical scheme; shock wave turbulent boundary layer interaction;

   Sammanfattning : Shock wave turbulent boundary layer interactions (SWTBLI) commonly arise in turbomachinery and aerospace applications and on the exterior of high speed aircrafts. In all these cases, SWTBLI can significantly change the flow and hence the physical load imposed by it. LÄS MER

4. 3. Assessment and Some Improvements of Hybrid RANS-LES Methods

   Författare :Sebastian Arvidson; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; LES; hybrid RANS-LES; zonal RANS-LES; embedded LES; PDH-LRN; log-layer mismatch; LES length scale; shock boundary-layer interaction;

   Sammanfattning : Motivated by numerical analysis of a shock/boundary-layer interacting (SBLI) flow in a duct, where some typical existing hybrid RANS-LES methods become awkward to give accurate predictions of the shock-induced corner separation bubble, a new hybrid RANS-LES method, has been proposed. The model is based on a low-Reynolds-number (LRN) $k-\omega$ RANS model, which is one of the few models that are capable of giving reasonable predictions for the SBLI flow in RANS computations. LÄS MER

5. 4. Methodologies for RANS-LES interfaces in turbulence-resolving simulations

   Författare :Sebastian Arvidson; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; zonal RANS-LES; aeronautics; RANS-LES interfaces; Hybrid RANS-LES; grey-area mitigation; log-layer mismatch; embedded LES; LES length scale; LES;

   Sammanfattning : Hybrid Reynolds-Average Navier-Stokes (RANS)-Large-Eddy Simulations (LES) techniques are now seen by the aeronautical industry as the most promising turbulence-resolving approaches for complex high-Reynolds-number turbulent flows with regard to cost and accuracy. However, connecting RANS and LES simulated flows is a challenging task and needs special attention in order to increase simulation robustness and accuracy. LÄS MER

7. 5. 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