Numerical Investigation of Combustion Instabilities in a Single Element Lean Direct Inject (LDI) Combustor Using Flamelet Based Approaches

2019 ◽  
Author(s):  
Saurabh Patwardhan ◽  
Pravin Nakod ◽  
Stefano Orsino ◽  
Carlo Arguinzoni
Keyword(s):  
Experimental Data ◽  
Equivalence Ratio ◽  
Single Element ◽  
Pressure Amplitude ◽  
Combustion Instabilities ◽  
Time Step ◽  
Impedance Boundary ◽  
Combustion Models ◽  
Flamelet Generated Manifold ◽  
Simulation Results

Abstract In this paper, high-fidelity large eddy simulations (LES) along with flamelet based combustion models are assessed to predict combustion dynamics in low-emissions gas turbine combustor. A model configuration of a single element lean-direct-injection (LDI) combustor from Purdue University [1] is used for the validation of simulation results. Two combustion models based on the flamelet concept, i.e., steady diffusion flamelet (SDF) model and flamelet generated manifold (FGM) model are employed to predict combustion instabilities. Simulations are carried out for two equivalence ratios of φ = 0.6, and 0.4 and the results in the form of mode shapes, peak to peak pressure amplitude and power spectrum density (PSD) are compared with the experimental data of Huang et al. [1]. The effect of variation in the time step size for transient simulations is also studied. The time step sizes corresponding to Acoustic Courant numbers of 4, 8 and 16 are tested. Further, two numerical solver options, i.e., pressure based segregated solver and pressure based coupled solver are used in understanding their effect on the solution convergence regarding the number of time steps required to reach the limit cycle of the pressure oscillations. An additional test for reducing the overall simulation time is explored using a truncated (half) calculation domain and applying an appropriate acoustic impedance boundary condition at the truncated location. The simulation results from this test for the equivalence ratio of φ = 0.6 are compared with the simulation results from the corresponding full domain test. Overall, the simulation results compare well with the experimental data and trends are captured accurately. A clear dominant acoustic mode of 4L is observed for the equivalence ratio of 0.6 that compares well with the experimental data. For the equivalence ratio of 0.4, simulation results show that there is no dominant frequency and the energy is distributed among the first five modes. It is consistent with the observations in the experiments. Both combustion models (SDF and FGM) used in this study capture the combustion instabilities accurately. It builds confidence in flamelet based combustion models for the use in combustion instability modeling which is traditionally done using finite rate chemistry models based on reduced kinetics.

Numerical Investigation of Combustion Instabilities in a Single-Element Lean Direct Inject Combustor Using Flamelet Based Approaches

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Saurabh Sudhir Patwardhan ◽  
Pravin Nakod ◽  
Stefano Orsino ◽  
Carlo Arguinzoni
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Direct Injection ◽  
Single Element ◽  
Combustion Instabilities ◽  
Gas Turbine Combustor ◽  
Combustion Dynamics ◽  
Lean Direct Injection ◽  
Combustion Models ◽  
Simulation Results

Abstract In this paper, high-fidelity large eddy simulations (LES) along with flamelet-based combustion models are assessed to predict combustion dynamics in low-emission gas turbine combustor. A model configuration of a single-element lean direct injection (LDI) combustor from Purdue University (Huang et al., 2014, “Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor,” 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, OH, July 28–30.) is used for the validation of simulation results. Two combustion models based on the flamelet concept, i.e., steady diffusion flamelet (SDF) model and flamelet generated manifold (FGM) model are employed to predict combustion instabilities. Simulations are carried out for two equivalence ratios of φ = 0.6, and 0.4. The results in the form of mode shapes, peak to peak pressure amplitude and power spectrum density (PSD) are compared with the experimental data of Huang et al. (2014, “Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor,” 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, OH, July 28–30.). The effect of variation in the time-step size hence acoustic courant number is studied. Further, two numerical solver options, i.e., pressure-based segregated solver and pressure-based coupled solver, are used to understand their effect on the solution convergence regarding the number of time-steps required to reach the limit cycle of the pressure oscillations. A truncated (half) domain simulation is performed by applying an appropriate acoustic impedance boundary condition at the truncated location. Overall, the simulation results compare well with the experimental data and trends are captured accurately in all simulations. It builds confidence in flamelet-based combustion models for the use in combustion instability modeling which is traditionally done using finite rate chemistry models based on reduced kinetics.

Impact of Combustion Models on Emissions Predictions From a Piloted Methane-Air Diffusion Flame

2019 ◽  
Author(s):  
Chitralkumar V. Naik ◽  
Hossam Elasrag ◽  
Rakesh Yadav ◽  
Ahad Validi ◽  
Ellen Meeks
Keyword(s):  
Mixture Fraction ◽  
Flame Structure ◽  
Direct Integration ◽  
Finite Rate ◽  
Modeling Approaches ◽  
Combustion Models ◽  
Eddy Simulation ◽  
Flamelet Generated Manifold ◽  
Simulation Results ◽  
Detailed Kinetics

Abstract Combustion models can have a significant impact on flame simulations. While solving finite rate chemistry typically yields more accurate predictions, they depend significantly on the detailed kinetics mechanism used. To demonstrate the effect, Large Eddy Simulation (LES) of Sandia Flame D [1] has been performed using various combustion models. Four different detailed kinetics mechanisms have been considered. They include DRM mechanism with 22 species, GRI-mech 2.11 with 49 species, GRI-mech 3.0 with 53 species [2], and Model Fuel Library (MFL) mechanism with 29 species [3]. In addition to the mechanisms, two modeling approaches considered are direct integration of finite rate kinetics (FR) and Flamelet Generated Manifold (FGM). The performance is compared between combinations of the mechanisms and combustion-modeling approaches for prediction of the flame structure and pollutants, including NO and CO. The mesh contains about half a million hexahedral cells and LES statistics were collected over ten flow throughs. Advanced solvers including dynamic cell clustering using the Chemkin-CFD solver in Fluent have been used for faster simulation time. Based on comparison of simulation results to the measurements at various axial and radial positions, we find that the results using the FGM approach were comparable to those using direct integration of FR chemistry, except for NO. In general, the simulation results are in good agreement with the experiment in terms of aerodynamics, mixture fraction and temperature profiles. However, kinetics mechanisms were found to have the most pronounced effect on emissions predictions. NO was especially more sensitive to the kinetics mechanism. Both versions of the GRI-mech fell short in predicting emissions. Overall, the MFL mechanism was found to yield the closest match with the data for flame structure, CO, and NO.

Simulation of Pollutant Emissions in a Small-Sized Combustion Chamber With a Gas Fuel for Various Regime Modes

2019 ◽  
Author(s):  
Nikita I. Gurakov ◽  
Ivan A. Zubrilin ◽  
Ivan V. Chechet ◽  
Vladislav M. Anisimov ◽  
Sergey S. Matveev ◽  
...  
Keyword(s):  
Experimental Data ◽  
Combustion Chamber ◽  
Equivalence Ratio ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Combustion Products ◽  
Pollutant Emissions ◽  
Eddy Simulation ◽  
Flamelet Generated Manifold ◽  
Combustion Processes

Abstract The study shows the results of the emission simulation in a small-sized combustion chamber. The influence of temperature and equivalence ratio on CO and CxHy in the combustion chamber was investigated. Experiments and calculations were carried out for the following modes: temperature at the inlet of the combustion chamber Tinlet = 323 ... 523 K; equivalence ratio φ = 0.2 ... 0.33; normalized flow rate at the inlet of the combustion chamber λ = 0.1 ... 0.3. The simulation of combustion of natural gas was carried out. The studies were conducted using CFD software and experimental methods. Measurements of the combustion products composition were carried out by the method of sampling collection and subsequent chromatographic analysis. The flow and combustion processes were simulated in a three-dimensional steady formulation using the Reynolds-averaged Novier-Stokes equations (RANS) and in a transient formulation using the Large Eddy Simulation (LES) method. The combustion processes were simulated by Flamelet Generated Manifold model in conjunction with the probability density function method (PDF). In addition to the above methods, the method of the reactor network model (RNM) was used to simulate the emission. As a result, a comparison of the calculated and experimental data of concentrations values of combustion products and emissions indices averaged over the combustion chamber outlet was conducted. According to the results of the calculated-experimental study obtained: - the simulated concentrations values of the main combustion products such as CO2 and H2O qualitatively and quantitatively coincide with the experimental data (the discrepancy is less than 5%) for all three approaches — RANS, LES, RNM; - when modeling CO emissions, the discrepancy between the calculated emission indices obtained by the RANS and LES methods is greatly underestimated relative to the experimental data, whereas the values calculated by the RNM method deviate from the experiment by less than 10%; - mass concentration values of unburned hydrocarbons obtained by the RANS method are overestimated relative to the experimental values, while using the LES with RNM methods, the discrepancy does not exceed 10%.

Effect of Equivalence Ratio on Propagation Process of Combustible Gas in Venting Tube

2012 ◽  
Vol 442 ◽  
pp. 402-406
Author(s):  
Shao Feng Ren ◽  
Xian Feng Chen ◽  
Yu Jie Wang ◽  
Yin Zhang
Keyword(s):  
Numerical Simulation ◽  
Equivalence Ratio ◽  
Turbulent Model ◽  
Propagation Process ◽  
Pressure Release ◽  
Combustion Models ◽  
Combustible Gas ◽  
Ratio Change ◽  
Simulation Results

To explore the effect of equivalence ratio on the propagation process of combustible gas in the venting tube, in the present study, the κ-ε turbulent model and the combustion models were implemented base on unaltered venting conditions and different equivalence ratio of methane-air. In particular, the numerical simulation results illustrate both speed and pressure were at maximum when equivalence ratio was 1.0. However, methane-air didn't reach the most sufficient combustion when equivalence ratio was 1.0. It was possible that the pressure release caught the equivalence ratio change and failed to generate detonation.

Impact of Flame Stretch and Heat Loss on Heat Release Distributions in Gas Turbine Combustors: Model Comparison and Validation

2016 ◽  
Author(s):  
Noah Klarmann ◽  
Thomas Sattelmayer ◽  
Weiqun Geng ◽  
Benjamin Timo Zoller ◽  
Fulvio Magni
Keyword(s):  
Experimental Data ◽  
Heat Loss ◽  
Model Comparison ◽  
Turbulent Flame ◽  
Combustion Process ◽  
Combustion Model ◽  
Qualitative Comparison ◽  
Combustion Models ◽  
Flamelet Generated Manifold ◽  
Flame Stretch

The work presented in this paper comprises the application of an extension for the Flamelet Generated Manifold model which allows to consider elevated flame stretch rates and heat loss. This approach does not require further table dimensions. Hence, the numerical overhead is negligible, preserving the industrial applicability. A validation is performed in which stretch and heat loss dependent distributions are obtained from the combustion model to compare them to experimental data from an atmospheric single burner test rig operating at lean conditions. The reaction mechanism is extended by OH*-kinetics which allows the comparison of numerical OH*-concentrations with experimentally obtained OH*-chemiluminescence. Improvement compared to the Flamelet Generated Manifold model without extension regarding the shape and position of the turbulent flame brush can be shown and are substantiated by the validation of species distributions which better fit the experimental in situ measurements when the extension is used. These improvements are mandatory to enable subsequent modeling of emissions or thermoacoustics where high accuracy is required. In addition to the validation, a qualitative comparison of further combustion models is performed in which the experimental data serve as a benchmark to evaluate the accuracy. Most combustion models typically simplify the combustion process as flame stretch or non-adiabatic effects are not captured. It turns out that the tested combustion models show improvement when stretch or heat loss is considered by model corrections. However, satisfactory results could only be achieved by considering both effects employing the extension for the Flamelet Generated Manifold model.

scholarly journals COMPUTATIONAL FLUID DYNAMIC ANALYSIS OF HIGHWAY BRIDGES EXPOSED TO HURRICANE WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 70 ◽  
Author(s):  
Mehrdad Bozorgnia ◽  
Jiin-Jen Lee
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Highway Bridges ◽  
Numerical Code ◽  
Time Step ◽  
Computational Fluid Dynamic Analysis ◽  
Two Phase ◽  
Simulation Results

In present paper, numerical code STAR CCM+ by CD-adapco which works based on compressible two-phase Navier Stokes equations is used to evaluate hydrodynamic forces exerted on prototype of I10 Bridge over Escambia Bay which was extensively damaged during Hurricane Ivan. Volume of Fluid (VOF) is used to capture dynamic free surface which is well suited for simulating complex discontinuous free surface associated with wave-deck interactions. 2D and 3D models were setup and properly configured. Simulations were conducted on High performance Computing and Communication Center (HPCC) at University of Southern California. Simulation results are compared to experimental data available from Hinsdale Wave Laboratory at Oregon State University. Comparison of experimental data to simulation results show the importance of proper mesh size and time step choice on accuracy of horizontal and vertical hydrodynamic force predictions applied to bridge superstructure.

Numerical Investigation of a Swirl Stabilized Methane Fired Burner and Validation With Experimental Data

2019 ◽  
Author(s):  
Federica Farisco ◽  
Philipp Notsch ◽  
Rene Prieler ◽  
Felix Greiffenhagen ◽  
Jakob Woisetschlaeger ◽  
...  
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Heat Release ◽  
Reaction Zone ◽  
Gas Turbines ◽  
Combustion Process ◽  
Operating Conditions ◽  
Main Reaction ◽  
Combustion Models ◽  
Flamelet Generated Manifold

Abstract In modern gas turbines for power generation and future aircraft engines, the necessity to reduce NOx emissions led to the implementation of a premixed combustion technology under fuel-lean conditions. In the combustion chamber of these systems, extreme pressure amplitudes can occur due to the unsteady heat release, reducing component life time or causing unexpected shutdown events. In order to understand and predict these instabilities, an accurate knowledge of the combustion process is inevitable. This study, which was provided by numerical methods, such as Computational Fluid Dynamics (CFD) is based on a three-dimensional (3D) geometry representing a premixed swirl-stabilized methane-fired burner configuration with a known flow field in the vicinity of the burner and well defined operating conditions. Numerical simulations of the swirl-stabilized methane-fired burner have been carried out using the commercial code ANSYS Fluent. The main objective is to validate the performance of various combustion models with different complexity by comparing against experimental data. Experiments have been performed for the swirl-stabilized methane-fired burner applying different technologies. Velocity fluctuation measurements have been carried out and validated through several techniques, such as Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). Laser Interferometric Vibrometry (LIV) provided information on heat release fluctuations and OH*-chemiluminescence measurements have been done to identify the position of the main reaction zone. During the first part of the CFD investigation, the cold flow has been simulated applying different turbulence models and the velocity flow field obtained in the experiments has been compared with the numerical results. As next, the study focuses on the numerical analysis of the thermo-chemical processes in the main reaction zone. Few combustion models have been investigated beginning from Eddy Dissipation Model (EDM) and proceeding with increased complexity investigating the Steady Flamelet Model (SLF) and Flamelet Generated Manifold (FGM). An evaluation of the velocity field and temperature profile has been performed for all models used in order to test the validity of the numerical approach for the chosen geometry. The best option for future investigations of gas turbines has been identified.

BEHAVIORAL MODEL OF A LINEAR VOLTAGE STABILIZER IN THE SPICE LANGUAGE

2019 ◽  
Author(s):  
Aleksey Malahanov
Keyword(s):  
Experimental Data ◽  
Behavioral Model ◽  
Voltage Stabilizer ◽  
Static Mode ◽  
Technical Description ◽  
Simulation Results ◽  
Chip Manufacturer ◽  
Linear Voltage

A variant of the implementation of the behavioral model of a linear voltage stabilizer in the Spice language is presented. The results of modeling in static mode are presented. The simulation results are compared with experimental data and technical description of the chip manufacturer.

scholarly journals Realization of a fractional-order RLC circuit via constant phase element

2021 ◽  
Author(s):  
Riccardo Caponetto ◽  
Salvatore Graziani ◽  
Emanuele Murgano
Keyword(s):  
Experimental Data ◽  
Carbon Black ◽  
Fractional Order ◽  
Constant Phase Element ◽  
Polymeric Matrix ◽  
Fractional Order Systems ◽  
New Device ◽  
Rlc Circuit ◽  
Simulation Results

AbstractIn the paper, a fractional-order RLC circuit is presented. The circuit is realized by using a fractional-order capacitor. This is realized by using carbon black dispersed in a polymeric matrix. Simulation results are compared with the experimental data, confirming the suitability of applying this new device in the circuital implementation of fractional-order systems.

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