Advanced combustion modelling with ANSYS FLUENT and Tabkin

Transcription

1 Advanced combustion modelling with ANSYS FLUENT and Tabkin F.A. Tap and P. Schapotschnikow ANSYS Belgium Conference 2011 Dacolt is a trading name of Dacolt International BV, registered under number at the Dutch chamber of commerce.

2 Contents Introduction Tabkin software for CFD look-up tables Dacolt PSR+PDF combustion model Integration with ANSYS FLUENT 12.1 Validation study: lifted n-heptane spray flame Industrial application: main burner for sulphur recovery unit Summary and outlook 2

3 About Dacolt Dacolt offers software and services for CFD modeling of industrial combustion applications Services: CFD consultancy Software development Software: Tabkin Combustion Web Apps About Dacolt: Based in Maastricht, the Netherlands Enhanced Solutions Partner of Ansys, Inc. 3

4 Combustion & CFD Large difference in time and length scales between flow and chemistry CFD codes typically resolve the flow scales Sub-grid modeling required for: Combustion chemistry Interaction between turbulence and chemistry Detailed chemistry required for: Combustion physics: auto-ignition in Diesel engines, knock in SI engines, flash-back in gas turbines, lifted flames in industrial burners,... Pollutant emissions: NOx, soot, CO,... Diesel engine simulation, courtesy of PSA Peugeot Citroën Observed trends in combustion modeling: Recent models use CFD look-up tables (FGM, FPI, ECFM-{3Z,CLEH},...) Increasing complexity of reaction mechanisms Look-up tables for combustion chemistry: Detailed chemistry effects and turbulence interaction with low CPU overhead 4

5 Use of CFD look-up tables in advanced combustion models 1. Chemical reactions are computed upfront and stored in look-up table 2. Combustion look-up table is read by CFD code 3. Chemical reactions are interpolated from look-up table during CFD simulation Computational effort for chemistry done prior to CFD simulation 5

6 Dacolt introduces Tabkin Software-as-a-Service package for generation of CFD lookup tables Features: Easy and powerful user interfaces Robust solvers Table visualisation Various combustion model exports Scalable CPU resources Turn-key solution for CFD look-up tables for ANSYS FLUENT 6

7 Advanced combustion model using Tabkin: Dacolt PSR+PDF An advanced combustion model has been devised: Using CFD look-up tables Based on detailed chemical kinetics Use of Tabkin in the CFD process Fields of application: Steady-state: non-premixed and flameless burners Unsteady: Diesel engines, HCCI, PCCI, SI engines knock,... Features: Progress variable / mixture fraction approach Turbulence / chemistry interaction: presumed PDF Complex chemistry model: homogeneous reactor 7

8 Implementation in Ansys Fluent 12.1 Dacolt has partnered with ANSYS, Inc. to investigate the latest technologies for reactive flow CFD simulations Dacolt PSR+PDF offers detailed chemical kinetics at CPU cost comparable to standard equilibrium PDF model Efficient parallel implementation through UDFs Steady-state and unsteady variants Well-defined thermo-chemistry 8

9 Typical working cycle using Tabkin (1) Secure login (5) Visualise and analyse look-up table online (2) Set-up look-up table generation (4) Download lookup table to local system and run CFD (3) Look-up table generation is executed on cloud resources 9

10 Lifted n-heptane spray flame from Engine Combustion Network (ECN) Test case ( Constant-volume vessel, high-pressure spray injection Diesel engine-like ambient conditions Variation of ambient oxygen concentration 21, 15, 12, 10 or 8 vol-% O2 CFD simulation Turbulent, two-phase, reacting flow 3D URANS CFD with ANSYS FLUENT 12.1 Auto-ignition, flame development and stabilisation of a lifted flame Dacolt PSR+PDF combustion model 108 mm CFD look-up tables from Tabkin n-heptane reaction mechanism 500+ species, reactions ECN video for 21% O2 10

11 Set-up look-up table calculation 11

12 Analyse look-up table 12

13 Download look-up table and run CFD 18 13

14 CFD results: typical ignition sequence 21 vol-% ambient oxygen concentration t = 0.2 ms t = 0.35 ms (ignition) t = 0.5 ms t = 1.0 ms t = 2.0 ms Temperature contours 14

15 CFD results: auto-ignition delay 15

16 CFD results: flame lift-off 16

17 CFD results: heat release modes 17

18 CFD results: flame structure 21% O2 15% O2 12% O2 10% O2 8% O2 Temperature contours after 2 ms 18

19 Industrial application CFD Consultancy for Duiker, the leading Dutch manufacturer of main burners for sulphur recovery units Dacolt PSR+PDF has been used to model key physics: Fast oxidation reactions and slow Claus reactions Flame lift-off 2D axi-symmetric and full 3D simulations on industrial scale 19

20 Summary Dacolt and Ansys have partnered for combustion model development An advanced combustion model named Dacolt PSR+PDF has been elaborated and implemented in ANSYS FLUENT 12.1 Tabkin is used to generate the required CFD look-up tables for combustion chemistry A lifted n-heptane spray flame test case has been presented Key physics are captured for varying ambient O2 content: Auto-ignition Flame lift-off Application of Dacolt PSR+PDF and Tabkin to industrial burners 20

21 Outlook Various test cases are under investigation at Dacolt: Diesel engine Delft Jet-in-Hot-Co-flow flameless burner Further integration of Tabkin with ANSYS FLUENT Enhancement of Tabkin with flamelet-based models 21

22 Advanced combustion modelling with ANSYS FLUENT and Tabkin F.A. Tap and P. Schapotschnikow ANSYS Belgium Conference 2011 Dacolt is a trading name of Dacolt International BV, registered under number at the Dutch chamber of commerce.