MUSCLES. Presented by: Frank Wetze University of Karlsruhe (TH) - EBI / VB month review, 21 September 2004, Karlsruhe

Transcription

1 MUSCLES Modelling of UnSteady Combustion in Low Emission Systems G4RD-CT R&T project within the 5 th Framework program of the European Union: 1

2 Numerical computations of reacting flow field for the Lean Blow Out test case 2

3 EBI contributions to MUSCLES Goals: Investigations on the influence of turbulent mixing and reaction on lean blow-out characteristics Structure of work: Month 0 6: Extension of 2-domain-1step kinetic model for the combustion of highly diluted hydrocarbon/air mixtures Validation by means of laminar premixed flame calculations and comparison with detailed mechanisms Month 6 12: Implementation in existing JPDF model and testing of enhanced kinetic sub-module Month 12 18: Isothermal test case and calculations of isothermal flow fields Validation of isothermal PDF calculations on basis of existing experimental results Implementation of necessary modifications to the JPDF module Month 18 36: Comparison of calculated PDF with experimental data for reacting case Improvement of JPDF model in order to calculate lean extinction phenomena with the desired accuracy Calculation of lean blowout limits for different operating conditions 3

4 System under investigation combustion chamber 100 mm 100 mm 100 mm 220 mm 4

5 System under investigation simplified contour 100 mm 100 mm 100 mm 220 mm 5

6 System under investigation clipping region of geometry 6

7 System under investigation clipping of computational grid 7

8 System under investigation airblast atomizer nozzle secondary swirler atomizer lip primary swirler 8

9 Résumé: Boundary conditions numerical setup

10 Résumé: Boundary conditions numerical setup Boundary Conditions: - P th : 15kW 165kW - fuel: methane - global fuel equivalence ratio: 0.5 ; inlet-temperature: 373 K Numerical Setup: - 3D CFD-computations - CFX-TASCflow - RANS ε - k - turbulence model - Grid: 3D axisymmetric nodes 10

11 2-domain-1-step kinetic scheme CH 4 LPF Flamespeed 11

12 LPF Flame Structure φ=0.55 T U =373K p=1bar 12

13 First calculations for the reacting case 2-domain-1-step kinetic scheme for 373K first calculations for the reacting case some unsteadiness in the solution field of those variables received by the JPDF-look-up-table further investigations JPDF-look-up table not smooth enough and contains imperfections especially for mixture fraction and reaction progress mean and variance values near to 0 or 1 solution improvement of the tabulation program PrePDF create JPDF-look-up-tables with a higher refinement deliverable D2.6: preliminary version of PrePDF

14 Adiabatic Calculation φ=0.5 P th =29kW 14

15 Adiabatic Calculation φ=0.5 P th =58kW improved tables 15

16 Adiabatic Calculation φ=0.5 P th =59kW improved tables 16

17 Stability Diagramm 17

18 Definition of the local enthalpy-index adiabatic calculation of the reactive system very stable combustion diffusion flame temperature = f ( local stoichiometry ) ~ h N local enthalpy-index ~ ~ hloc f,c,tloc h f,c,t = ref ~ ~ h (f,c,t ) h (f,c,t ad ( ) ( ) ad ref ref ref ) ~ h ~ h ~ h ( f,c, ) loc T loc ( f,c, ) ad T ad ( f,c, ) ref T ref - local, total enthalpy: - total enthalpy of the local mixture - given by CFD-Computation - adiabatic, total enthalpy: - total enthalpy of the local mixture without heat loss (adiabatic) - reference, total enthalpy: - total enthalpy of the local mixture at the reference temperature T ref 18

19 JPDF look-up table Generation and Access Generation Access modified + transport equation for enthalpy 19

20 Conclusion - first CFD-calculations for the reactive test case quality of the 2-domain-1-step chemical kinetic scheme - new, special fit for the preheating temperature of 373K Problems with the resolution of the JPDF-look-up table for extreme values of the tabulation variables - improvement of PrePDF to feature higher table refinement deliverable D2.6 Lean Blow Out can be simulated using our JPDF-Model Much too stable simulated combustion at the current state of development - necessity to handle non-adiabatic combustion with the JPDF-module - definition of the local enthalpy-index - strategy for the extension of the JPDF-module 20

21 Conclusion - first CFD-calculations for the reactive test case quality of the 2-domain-1-step chemical kinetic scheme - new, special fit for the preheating temperature of 373K Problems with the resolution of the JPDF-look-up table for extreme values of the tabulation variables - improvement of PrePDF to feature higher table refinement deliverable D2.6 Lean Blow Out can be simulated using our JPDF-Model Much too stable simulated combustion at the current state of development - necessity to to handle non-adiabatic combustion with with the the JPDF-module - definition of of the the local enthalpy-index - strategy for the extension of of the the JPDF-module work in progress 21

22 Numerical computations of reacting flow field for the Lean Blow Out test case 22