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LES Software for the Design of Low Emission Combustion Systems for Vision 21 Plants, Quarterly Report: April - June 2004

Description: Three SIMVAL LES calculations were completed this quarter: {phi} (equivalence ratio) of (1) 0.55, (2) 0.625, and (3) 0.7. The predictions were first analyzed, and then compared to existing experimental data of pressure dynamics, NO{sub x}, and CO emissions. It appears that the combustor flowfield changes for the {phi} of 0.55 case (compared to the other two cases), and this flowfield change results in a slight reduction in the pressure dynamics compared to the {phi} of 0.625 case. The predicted pressure rms values were 1.0 psi or less for the three cases. Good agreement was seen between predicted and measured NO{sub x} emissions for the cases with {phi} = 0.55 and {phi} = 0.625. The CO predictions were higher than the measurements, but possible reasons were identified. A new SIMVAL dataset recorded June, 2004, is being processed and will be transmitted to CFDRC in the near future. The previous two datasets had known deficiencies. This new dataset will be compared to the LES predictions in the next quarter.
Date: July 2004
Creator: Meredith, Karl V. & Smith, Clifford E.

LES Software for the Design of Low Emission Combustion Systems for Vision 21 Plants, Quarterly Report: January - March 2003

Description: Application and testing of the new combustion Large Eddy Simulation (LES) code for the design of advanced gaseous combustion systems is described in this 10th quarterly report. CFD Research Corporation has developed the LES module within the parallel, unstructured solver included in the commercial CFD-ACE+ software. In this quarter, validation and testing of the combustion LES code was performed for the DOE-Simval combustor. Also, Beta testing by consortium members was performed for various burner and combustor configurations. In the two quarters ahead, CFDRC will validate the code on the new DOE SimVal experiments. Experimental data from DOE should be available in June 2003, though LES calculations are currently being performed. This will ensure a truly predictive test of the software. CFDRC will also provide help to the consortium members on running their cases, and incorporate improvements to the software suggested by the beta testers. The beta testers will compare their predictions with experimental measurements and other numerical calculations. At the end of this project (October, 2003), a final released version of the software will be available for licensing to the general public.
Date: April 2003
Creator: Cannon, Steven & Smith, Clifford

LES Software for the Design of Low Emission Combustion Systems for Vision 21 Plants, Quarterly Report: July - September 2001

Description: Further development of a combustion Large Eddy Simulation (LES) code for the design of advanced gaseous combustion systems is described in this fourth quarterly report. CFD Research Corporation (CFDRC) is developing the LES module within the parallel, unstructured solver included in the commercial CFD-ACE+ software. In this quarter, in-situ adaptive tabulation (ISAT) for efficient chemical rate storage and retrieval was further tested in the LES code. A more efficient PK binary tree data structure is being developed and implemented to replace the original BSP-tree structure. Implementation of the Linear Eddy Model (LEM) for subgrid chemistry has also started. In addition, Georgia Tech has shown that a chemical neural net (1-step chemistry) trained at certain turbulent conditions can be used at different turbulent conditions without expensive chemical kinetic integrations. Initial evaluations of the code accuracy have also been carried out. The evaluations cases included the unstable DOE-NETL combustor and a lid-driven cavity. Next quarter, the ISAT algorithm for efficient chemistry will be tested for the unstable DOE-NETL combustor. Initial flame calculations, with the LEM subgrid chemistry model are planned. Also, demonstration of the neural net approach, for chemical kinetics speed-up, should be demonstrated for more advanced chemistry (8-species and 19-species mechanisms).
Date: October 2001
Creator: Cannon, Steve; Adumitroaie, Virgil; McDaniel, Keith & Smith, Cliff

LES Software for the Design of Low Emission Combustion Systems for Vision 21 Plants, Quarterly Report: July - September 2004

Description: Work in this quarter focused on the continued running of two SIMVAL cases: {phi} (equivalence ratio) of (1) 0.55 and (2) 0.625. Comparisons were made between RANS and LES predictions for the {phi} of 0.625 case. The LES calculation showed a different flow pattern in the combustor compared to the RANS calculation, in particular the combustor recirculation flow pattern on the centerline is dramatically different. To demonstrate that the LES solution is accurate (and the RANS is not), non-reacting cases based on the Lilley experiment (Lilley, 1985) were run. Results from the Lilley cases verified that the LES calculations more closely match experimental velocity measurements for highly swirled, turbulent flows with a downstream constriction. In particular, RANS predictions show a strong centerline recirculation zone in the combustor, while LES predictions show positive axial velocity on the centerline, and an annular recirculation zone around the centerline. Animation files were also created this quarter, so as to better demonstrate the LES predictions.
Date: October 2004
Creator: Meredith, Karl V. & Smith, Clifford E.

LES Software for the Design of Low Emission Combustion Systems for Vision 21 Plants, Quarterly Report: October - December 2004

Description: Vision 21 combustion systems will require innovative low emission designs and low development costs if Vision 21 goals are to be realized. In this three-year project, an advanced computational software tool will be developed for the design of low emission combustion systems required for Vision 21 clean energy plants. The combustion Large Eddy Simulation (LES) software will be able to accurately simulate the highly transient nature of gaseous-fueled turbulent combustion so that innovative concepts can be assessed and developed with fewer high-cost experimental tests. During the first year, the project included the development and implementation of improved chemistry (reduced GRI mechanism), subgrid turbulence (localized dynamic), and subgrid combustion-turbulence interaction (Linear Eddy) models into the CFDACE+ code. University expertise (Georgia Tech and UC Berkeley) was utilized to help develop and implement these advanced submodels into the unstructured, parallel CFD flow solver, CFD-ACE+. Efficient numerical algorithms that rely on in situ look-up tables or artificial neural networks were implemented for chemistry calculations. In the second year, the combustion LES software was evaluated and validated using experimental data from lab-scale and industrial test configurations. This code testing (i.e., alpha testing) was performed by CFD Research Corporation's engineers. During the third year, six industrial and academic partners used the combustion LES code and exercised it on problems of their choice (i.e., beta testing). Final feedback and optimizations were then be implemented in the final release version of the combustion LES software that will be licensed to the general public. An additional one-year task was added for the fourth year of this program entitled, ''LES Simulations of SIMVAL Results''. For this task, CFDRC performed LES calculations of selected SIMVAL cases, and compared predictions with measurements. In addition to comparisons with NO{sub x} and CO exit measurements, comparisons were made to measured pressure oscillations. Possible gaps ...
Date: April 2005
Creator: Smith, Clifford E.