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Large Eddy Simulations with a Tabulated Conditional Moment Closure Moment Closure Model for Turbulent Premixed Combustion with Heat Loss
Title
Large Eddy Simulations with a Tabulated Conditional Moment Closure Moment Closure Model for Turbulent Premixed Combustion with Heat Loss.
Creator
Velez, Carlos, Vasu Sumathi, Subith, Martin, Scott, Kassab, Alain, Das, Tuhin, University of Central Florida
Abstract / Description
The Tabulated Premixed Conditional Moment Closure (T-PCMC) method has been shown to provide the capability to predict turbulent, premixed methane flames with detailed chemistry and reasonable run times in a RANS/URANS adiabatic environment. Here the premixed T-PCMC method is extended in a Large Eddy Simulation (LES) framework for non-adiabatic premixed flames, allowing heat loss to occur in the mixture before, during and after combustion. It is proposed that the LES framework is a more...
Show moreThe Tabulated Premixed Conditional Moment Closure (T-PCMC) method has been shown to provide the capability to predict turbulent, premixed methane flames with detailed chemistry and reasonable run times in a RANS/URANS adiabatic environment. Here the premixed T-PCMC method is extended in a Large Eddy Simulation (LES) framework for non-adiabatic premixed flames, allowing heat loss to occur in the mixture before, during and after combustion. It is proposed that the LES framework is a more suitable representation for both chemical and turbulent scales in premixed combustion. By resolving the high energy turbulent scales and modeling the small scale turbulence, it is expected that the resolution of the turbulence and transient effects are better captured in a LES framework leading to better predictions of the mixing rate and consequently the reaction rate, which is the main focus and source of error in combustion modeling. The LES T-PCMC model is implemented using the open source CFD software OpenFOAM for its open access to C++ source code and large library of turbulence and thermo-physical models. The proposed model validated with PIV and Raman measurements of a turbulent, enclosed reacting flame of a single jet and backward facing step geometry. The DLR data sets provide both unity (E.g.Methane) and non-unity (E.g. Hydrogen) Lewis number fuels, allowing for the proposed numerical model to be validated against both unity and non-unity Lewis # flames. Velocity, temperature and major/minor species are compared to the experimental data. Once validated, this model is intended to be useful for designing lean premixed combustors for gas turbines which operate primarily in the corrugated premixed combustion regime, where chemical and turbulent time scales are of the same order requiring adequate models for their interaction.LES results match the experimental data better than the Reynolds Averaged Navier-Stokes (RANS/URANS) solution and is able to better resolve the transient features of the flame with an increase in run time of only 50 %, when compared to URANS.
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Date Issued
2015
Identifier
CFE0006234, ucf:51058
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006234
AN OPTIMAL CONTROL APPROACH FOR DETERMINATION OF THE HEAT LOSS COEFFICIENT IN AN ICS SOLAR DOMESTIC WATER HEATING SYSTEM
Title
AN OPTIMAL CONTROL APPROACH FOR DETERMINATION OF THE HEAT LOSS COEFFICIENT IN AN ICS SOLAR DOMESTIC WATER HEATING SYSTEM.
Creator
Gil, Camilo, Simaan, Marwan, University of Central Florida
Abstract / Description
Water heating in a typical home in the U.S. accounts for a significant portion (between 14% and 25%) of the total homeÂÂÂÂ's annual energy consumption. The objective of considerably reducing the homeÂÂÂÂ's energy consumption from the utilities calls for the use of onsite renewable energy...
Show moreWater heating in a typical home in the U.S. accounts for a significant portion (between 14% and 25%) of the total homeÂÂÂÂ's annual energy consumption. The objective of considerably reducing the homeÂÂÂÂ's energy consumption from the utilities calls for the use of onsite renewable energy systems. Integral Collector Storage (ICS) solar domestic water heating systems are an alternative to help meet the hot water energy demands in a household. In order to evaluate the potential benefits and contributions from the ICS system, it is important that the parameter values included in the model used to estimate the systemÂÂÂÂ's performance are as accurate as possible. The overall heat loss coefficient (Uloss) in the model plays an important role in the performance prediction methodology of the ICS. This work presents a new and improved methodology to determine Uloss as a function of time in an ICS system using a systematic optimal control theoretic approach. This methodology is based on the derivation of a new nonlinear state space model of the system, and the formulation of a quadratic performance function whose minimization yields estimates of Uloss values that can be used in computer simulations to improve the performance prediction of the ICS system, depending on the desired time of the year and hot water draw profile. Simulation results show that predictions of the systemÂÂÂÂ's performance based on these estimates of Uloss are considerably more accurate than the predictions based on current existing methods for estimating Uloss.
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Date Issued
2010
Identifier
CFE0003266, ucf:48525
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003266
INTERACTION BETWEEN SECONDARY FLOW AND FILM COOLING JETS OF A REALISTIC ANNULAR AIRFOIL CASCADE (HIGH MACH NUMBER)
Title
INTERACTION BETWEEN SECONDARY FLOW AND FILM COOLING JETS OF A REALISTIC ANNULAR AIRFOIL CASCADE (HIGH MACH NUMBER).
Creator
Nguyen, Cuong, Kapat, Jayanta, University of Central Florida
Abstract / Description
Film cooling is investigated on a flat plate both numerically and experimentally. Conical shaped film hole are investigated extensively and contribute to the current literature data, which is extremely rare in the open public domain. Both configuration of the cylindrical film holes, with and without a trench, are investigated in detail. Design of experiment technique was performed to find an optimum combination of both geometrical and fluid parameters to achieve the best film cooling...
Show moreFilm cooling is investigated on a flat plate both numerically and experimentally. Conical shaped film hole are investigated extensively and contribute to the current literature data, which is extremely rare in the open public domain. Both configuration of the cylindrical film holes, with and without a trench, are investigated in detail. Design of experiment technique was performed to find an optimum combination of both geometrical and fluid parameters to achieve the best film cooling performance. From this part of the study, it shows that film cooling performance can be enhanced up to 250% with the trenched film cooling versus non-trenched case provided the same amount of coolant. Since most of the relevant open literature is about film cooling on flat plate endwall cascade with linear extrusion airfoil, the purpose of the second part of this study is to examine the interaction of the secondary flow inside a 3D cascade and the injected film cooling jets. This is employed on the first stage of the aircraft gas turbine engine to protect the curvilinear (annular) endwall platform. The current study investigates the interaction between injected film jets and the secondary flow both experimentally and numerically at high Mach number (M=0.7). Validation shows good agreement between obtained data with the open literature. In general, it can be concluded that with an appropriate film coolant to mainstream blowing ratio, one can not only achieve the best film cooling effectiveness (FCE or η) on the downstream endwall but also maintain almost the same aerodynamic loss as in the un-cooled baseline case. Film performance acts nonlinearly with respect to blowing ratios as with film cooling on flat plate, in the other hand, with a right blowing ratio, film cooling performance is not affect much by secondary flow. In turn, film cooling jets do not increase pressure loss at the downstream wake area of the blades.
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Date Issued
2010
Identifier
CFE0003546, ucf:48944
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003546