Can Water Dilution Avoid Flashback On a Hydrogen Enriched Micro Gas Turbine Combustion? – A Large Eddy Simulations Study

2021 ◽  
Author(s):  
Alessio Pappa ◽  
Laurent Bricteux ◽  
Pierre Bénard ◽  
Ward De Paepe
Keyword(s):  
Reaction Rates ◽  
Hydrogen Combustion ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Reference Case ◽  
Large Eddy ◽  
Pure Methane ◽  
The Impact ◽  
Water Dilution ◽  
Air Humidification

Abstract Considering the growing interest in Power-to-Fuel, i.e. production of H2 using electrolysis to store excess renewable electricity, combustion-based technologies still have a role to play in the future of power generation. Hydrogen combustion is well-known to lead to combustion instabilities. The high temperatures and reaction rates can potentially lead to flashback. In the past, combustion air humidification has proven effective to reduce temperatures and reaction rates. Therefore, humidification can open a path to stabilize hydrogen combustion. However, accurate data assessing the impact of humidification on the combustion is still missing for real mGT combustor geometries and operating conditions. This paper presents a comparison between pure methane and hydrogen enriched methane/air combustions, with and without air humidification, in a typical mGT combustion chamber (Turbec T100) using Large Eddy Simulations analysis. In a first step, the necessary minimal water dilution, to reach stable combustion with hydrogen, was assessed using a 1D approach. The one-dimensional unstretched laminar flame is computed for both pure methane (reference case) and hydrogen enriched cases. The results of this comparison show that the same level of flame speed as in the reference case can be reached by adding 10% (in mass fraction) of water. In a second step, high fidelity LES on the 3D geometry are performed to show that water dilution helped to lower the temperature and reaction rate of hydrogen at same levels as reference case, and thus prevents flashback, enabling the use of hydrogen blends in the mGT.

Can Water Dilution Avoid Flashback on a Hydrogen Enriched Micro Gas Turbine Combustion? A Large Eddy Simulations Study

2020 ◽  
Author(s):  
Alessio Pappa ◽  
Laurent Bricteux ◽  
Pierre Bénard ◽  
Ward De Paepe
Keyword(s):  
Gas Turbines ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Small Scale ◽  
Reference Case ◽  
Large Eddy ◽  
Pure Methane ◽  
Water Dilution ◽  
Air Humidification

Abstract Considering the growing interest in Power-to-Fuel, i.e. production of H2 using electrolysis to store excess renewable electricity, combustion-based technologies still have a role to play in the future of power generation. Especially in a decentralized production with small-scale cogeneration, micro Gas Turbines (mGTs) offer great advantages related to their high adaptability and flexibility, in terms of operation and fuel. Hydrogen (or hydrogen enriched methane) combustion is well-known to lead to flame and combustion instabilities. The high temperatures and reaction rates reached in the combustor can potentially lead to flashback. In the past, combustion air humidification (i.e. water addition) has proven effective to reduce temperatures and reaction rates, leading to significant NOx emission reductions. Therefore, combustion air humidification can open a path to stabilize hydrogen combustion in a classical mGT combustor. However accurate data assessing the impact of humidification on the combustion is still missing for real mGT combustor geometries and operating conditions. In this framework, this paper presents a comparison between pure methane and hydrogen enriched methane/air combustions, with and without combustion air humidification, in a typical mGT combustion chamber (Turbec T100) using Large Eddy Simulations (LES) analysis. In a first step, the necessary minimal water dilution, to reach stable and low emissions combustion with hydrogen, was assessed using a 1D approach. The one-dimensional unstretched laminar flame is computed for both pure methane (reference case) and hydrogen enriched methane/air combustion cases. The results of this comparison show that, for the hydrogen enriched combustion, the same level of flame speed as in the reference case can be reached by adding 10% (in mass fraction) of water. In a second step, the feasibility and flexibility of humidified hydrogen enriched methane/air combustion in an industrial mGT combustor have been demonstrated by performing high fidelity LES on a 3D geometry. Results show that steam dilution helped to lower the reactivity of hydrogen, and thus prevents flashback, enabling the use of hydrogen blends in the mGT at similar CO levels, compared to the reference case. These results will help to design future combustor towards more stability.

scholarly journals Comparison of Field Measurements and Large Eddy Simulations of the Scaled Wind Farm Technology (SWiFT) Site

2019 ◽  
Author(s):  
Myra L. Blaylock ◽  
Brent C. Houchens ◽  
David C. Maniaci ◽  
Thomas Herges ◽  
Alan Hsieh ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Wind Farm ◽  
Field Measurements ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Department Of Energy ◽  
Large Eddy ◽  
In Series ◽  
The Impact

Abstract Power production of the turbines at the Department of Energy/Sandia National Laboratories Scaled Wind Farm Technology (SWiFT) facility located at the Texas Tech University’s National Wind Institute Research Center was measured experimentally and simulated for neutral atmospheric boundary layer operating conditions. Two V27 wind turbines were aligned in series with the dominant wind direction, and the upwind turbine was yawed to investigate the impact of wake steering on the downwind turbine. Two conditions were investigated, including that of the leading turbine operating alone and both turbines operating in series. The field measurements include meteorological evaluation tower (MET) data and light detection and ranging (lidar) data. Computations were performed by coupling large eddy simulations (LES) in the three-dimensional, transient code Nalu-Wind with engineering actuator line models of the turbines from OpenFAST. The simulations consist of a coarse precursor without the turbines to set up an atmospheric boundary layer inflow followed by a simulation with refinement near the turbines. Good agreement between simulations and field data are shown. These results demonstrate that Nalu-Wind holds the promise for the prediction of wind plant power and loads for a range of yaw conditions.

scholarly journals Large Eddy Simulations of Strongly Non-Ideal Compressible Flows through a Transonic Cascade

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 772
Author(s):  
Jean-Christophe Hoarau ◽  
Paola Cinnella ◽  
Xavier Gloerfelt
Keyword(s):  
Compressible Flows ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Working Fluid ◽  
Viscous Effects ◽  
Large Eddy

Transonic flows of a molecularly complex organic fluid through a stator cascade were investigated by means of large eddy simulations (LESs). The selected configuration was considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non-ideal gas effects. A heavy fluorocarbon, perhydrophenanthrene (PP11), was selected as the working fluid to exacerbate deviations from the ideal flow behavior. The LESs were carried out at various operating conditions (pressure ratio and total conditions at inlet), and their influence on compressibility and viscous effects is discussed. The complex thermodynamic behavior of the fluid generates highly non-ideal shock systems at the blade trailing edge. These are shown to undergo complex interactions with the transitional viscous boundary layers and wakes, with an impact on the loss mechanisms and predicted loss coefficients compared to lower-fidelity models relying on the Reynolds-averaged Navier–Stokes (RANS) equations.

Prediction of liquid-liquid flow in an SMX static mixer using large eddy simulations

2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Paulina Pianko-Oprych ◽  
Zdzisław Jaworski
Keyword(s):  
Centrifugal Force ◽  
Liquid Flow ◽  
Concentration Distribution ◽  
Large Eddy Simulations ◽  
Dispersed Phase ◽  
Static Mixer ◽  
Phase Concentration ◽  
Large Eddy ◽  
Smx Static Mixer ◽  
The Impact

AbstractThe main purpose of the paper is to apply the large eddy simulations (LES) technique and to verify its use as a predicting tool for turbulent liquid-liquid flow in an SMX static mixer. LES modeling was carried out using the Smagorinsky-Lilly model of the turbulent subgrid viscosity for the Reynolds number of 5000 and 10000. The continuous phase was water and the dispersed phase was silicon oil. The investigation covers the effects of the density ratio between the phases. Three different cases of liquid densities were considered. The dispersed phase concentration distribution in the mixer cross-sections was compared with the corresponding time averaged results obtained formerly for the same configuration in a steady-state simulation using the standard RANS approach with the k-ɛ model. The dependency of the standard deviation of the dispersed phase concentration on the distance from the mixer inlet and the impact of the centrifugal force on the phase concentration distribution were investigated. The presented results for the SMX static mixer confirm conclusions of previous studies by Jaworski et al. (2006) obtained for a Kenics static mixer and show less a pronounced influence of the centrifugal force on the phase concentration distribution of the LES results in comparison to the RANS case.

scholarly journals High-resolution large-eddy simulations of sub-kilometer-scale turbulence in the upper troposphere lower stratosphere

2013 ◽  
Vol 13 (12) ◽  
pp. 31891-31932 ◽  
Author(s):  
R. Paoli ◽  
O. Thouron ◽  
J. Escobar ◽  
J. Picot ◽  
D. Cariolle
Keyword(s):  
Large Scale ◽  
Lower Stratosphere ◽  
Atmospheric Model ◽  
Large Eddy Simulations ◽  
Stratified Flows ◽  
Flow Topology ◽  
Upper Troposphere ◽  
Large Eddy ◽  
Scale Turbulence ◽  
The Impact

Abstract. Large-eddy simulations of sub-kilometer-scale turbulence in the upper troposphere lower stratosphere (UTLS) are carried out and analyzed using the mesoscale atmospheric model Méso-NH. Different levels of turbulence are generated using a large-scale stochastic forcing technique that was especially devised to treat atmospheric stratified flows. The study focuses on the analysis of turbulence statistics, including mean quantities and energy spectra, as well as on a detailed description of flow topology. The impact of resolution is also discussed by decreasing the grid spacing to 2 m and increasing the number of grid points to 8×109. Because of atmospheric stratification, turbulence is substantially anisotropic, and large elongated structures form in the horizontal directions, in accordance with theoretical analysis and spectral direct numerical simulations of stably stratified flows. It is also found that the inertial range of horizontal kinetic energy spectrum, generally observed at scales larger than a few kilometers, is prolonged into the sub-kilometric range, down to the Ozmidov scales that obey isotropic Kolmorogov turbulence. The results are in line with observational analysis based on in situ measurements from existing campaigns.

High Resolution Large Eddy Simulations to Evaluate Turbulence Properties Within a Real Helicopter Engine Combustor

2018 ◽  
Author(s):  
Charlie Koupper ◽  
Jean Lamouroux ◽  
Stephane Richard ◽  
Gabriel Staffelbach
Keyword(s):  
Gas Turbine ◽  
Turbulence Intensity ◽  
Numerical Scheme ◽  
Mesh Refinement ◽  
Large Eddy Simulations ◽  
Scale Model ◽  
Large Eddy ◽  
Set Up ◽  
High Level ◽  
The Impact

In a gas turbine, the combustor is feeding the turbine with hot gases at a high level of turbulence which in turns strongly enhances the heat transfer in the turbine. It is thus of primary importance to properly characterize the turbulence properties found at the exit of a combustor to design the turbine at its real thermal constraint. This being said, real engine measurements of turbulence are extremely rare if not inexistent because of the harsh environment and difficulty to implement experimental techniques that usually operate at isothermal conditions (e.g. hot wire anemometry). As a counterpart, high fidelity unsteady numerical simulations using Large Eddy Simulations (LES) are now mature enough to simulate combustion processes and turbulence within gas turbine combustors. It is thus proposed here to assess the LES methodology to qualify turbulence within a real helicopter engine combustor operating at take-off conditions. In LES, the development of turbulence is primarily driven by the level of real viscosity in the calculation, which is the sum of three contributions: laminar (temperature linked), turbulent (generated by the sub-grid scale model) and artificial (numerics dependent). In this study, the impact of the two main sources of un-desired viscosity is investigated: the mesh refinement and numerical scheme. To do so, three grids containing 11, 33 and 220 million cells for a periodic sector of the combustor are tested as well as centred second (Lax-Wendroff) and third order (TTGC) in space schemes. The turbulence properties (intensity and integral scales) are evaluated based on highly sampled instantaneous solutions and compared between the available simulations. Results show first that the duration of the simulation is important to properly capture the level of turbulence. If short simulations (a few combustor through-times) may be sufficient to evaluate the turbulence intensity, a bias up to 14% is introduced for the turbulence length scales. In terms of calculation set-up, the mesh refinement is found to have a limited influence on the turbulence properties. The numerical scheme influence on the quantities studied here is small, highlighting that the employed schemes dissipation properties are already sufficient for turbulence characterization. Finally, spatially averaged values of turbulence intensity and lengthscale at the combustor exit are almost identically predicted in all cases. However, significant variations from hub to tip are reported, which questions the pertinence to use 0-D turbulence boundary conditions for turbines. Based on the set of simulations discussed in the paper, guidelines can be derived to adequately set-up (mesh, scheme) and run (duration, acquisition frequency) a LES when turbulence evaluation is concerned. As no experimental counterpart to this study is available, the conclusions mainly aim at knowing the possible numerical bias rather than commenting on the predictivity of the approach.

Can Water Dilution Avoid Flashback on a Hydrogen Enriched Micro Gas Turbine Combustion? A Large Eddy Simulations Study

2021 ◽  
Author(s):  
Alessio Pappa ◽  
Laurent Bricteux ◽  
Pierre B\xe9nard ◽  
Ward De Paepe
Keyword(s):  
Gas Turbine ◽  
Large Eddy Simulations ◽  
Micro Gas Turbine ◽  
Large Eddy ◽  
Gas Turbine Combustion ◽  
Water Dilution

Large-Eddy Simulations of Heat Transfer Within a Multi-Perforation Synthetic Jets Configuration

2019 ◽  
Author(s):  
Soizic Esnault ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Heat Transfer ◽  
Flow Behavior ◽  
Synthetic Jets ◽  
Large Eddy Simulations ◽  
Heated Plate ◽  
Piston Displacement ◽  
Large Eddy ◽  
Grazing Flow ◽  
The Impact ◽  
Ejection Phase

Abstract Synthetic jets are produced by devices that enable a suction phase followed by an ejection phase. The resulting mean mass budget is hence null and no addition of mass in the system is required. These particular jets have especially been considered for some years for flow control applications. They also display features that can become of interest to enhance heat exchanges, for example for wall cooling issues. Synthetic jets can be generated through different mechanisms, such as acoustics by making use of a Helmholtz resonator or through the motion of a piston as in an experience mounted at Institut Pprime in France. The objective of this specific experiment is to understand how synthetic jets can enhance heat transfer in a multi-perforated configuration. As a complement to this experimental set up, Large-Eddy Simulations are produced and analysed in the present document to investigate the flow behavior as well as the impact of the synthetic jets on wall heat transfer. The experimental system considered here consists in a perforated heated plate, each perforation being above a cavity where a piston is used to control the synthetic jets. Placed in a wind tunnel test section, the device can be studied with a grazing flow and multiple operating points are available. The one considered here implies a grazing flow velocity of 12.8 m.s−1, corresponding to a Mach number around 0.04, and a piston displacement of 22 mm peak-to-peak at a frequency of 12.8 Hz. These two latter parameters lead to a jet Reynolds number of about 830. A good agreement is found between numerical results and experimental data. The simulations are then used to provide a detailed understanding of the flow. Two main behaviours are found, depending on the considered mid-period. During the ejection phase, the flow transitions to turbulence and the formation of characteristic structures is observed; the plate is efficiently cooled. During the suction phase the main flow is stabilised; the heat enhancement is particularly efficient in the hole wakes but not between them, leading to a heterogeneous temperature field.

scholarly journals Large Eddy Simulations with Conjugate Heat Transfer (CHT) modeling of Internal Combustion Engines (ICEs)

2019 ◽  
Vol 74 ◽  
pp. 51 ◽  
Author(s):  
Angela Wu ◽  
Seunghwan Keum ◽  
Volker Sick
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Wall Temperature ◽  
Conjugate Heat Transfer ◽  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Large Eddy Simulations ◽  
Temperature Fields ◽  
Large Eddy ◽  
The Impact

In this study, the effects of the thermal boundary conditions at the engine walls on the predictions of Large-Eddy Simulations (LES) of a motored Internal Combustion Engine (ICE) were examined. Two thermal boundary condition cases were simulated. One case used a fixed, uniform wall temperature, which is typically used in conventional LES modeling of ICEs. The second case utilized a Conjugate Heat Transfer (CHT) modeling approach to obtain temporally and spatially varying wall temperature. The CHT approach solves the coupled heat transfer problem between fluid and solid domains. The CHT case included the solid valves, piston, cylinder head, cylinder liner, valve seats, and spark plug geometries. The simulations were validated with measured bulk flow, near-wall flow, surface temperature, and surface heat flux. The LES quality of both simulations was also discussed. The CHT results show substantial spatial, temporal, and cyclic variability of the wall heat transfer. The surface temperature dynamics obtained from the CHT model compared well with measurements during the compression stroke, but the absolute magnitude was 5 K (or 1.4%) off and the prediction of the drop in temperature after top dead center suffered from temporal resolution limitations. Differences in the predicted flow and temperature fields between the uniform surface temperature and CHT simulations show the impact of the surface temperature on bulk behavior.

scholarly journals Wildfires as a source of airborne mineral dust – Revisiting a conceptual model using Large-Eddy simulations (LES)

2018 ◽  
Author(s):  
Robert Wagner ◽  
Michael Jähn ◽  
Kerstin Schepanski
Keyword(s):  
Conceptual Model ◽  
Mineral Dust ◽  
Large Eddy Simulations ◽  
Dust Particles ◽  
Strong Increase ◽  
Dust Emissions ◽  
Large Eddy ◽  
Fire Area ◽  
Fire Properties ◽  
The Impact

Abstract. Airborne mineral dust is a key player in the Earth system and shows manifold of impacts on atmospheric properties such as the radiation budget and cloud micro-physics. Investigations of smoke plumes originating from wildfires found significant fractions of mineral dust within these plumes – raised by strong turbulent winds related to the fire. The present study revisits the conceptual model describing the emission of mineral dust particles during wildfires by pyro-convection as described by the literature. This is achieved by means of high resolved Large-Eddy simulations (LES), conducted with the All Scale Atmospheric Model (ASAM). The impact of different fire properties representing typical grassland and shrubland fires, and different ambient atmospheric conditions on the fire-driven winds and their capability to mobilize mineral dust particles were investigated. Results from this study illustrate that the energy release of the fire leads to a strong increase in strength and frequency of occurrence of intense near-surface winds, which exceed typical threshold velocities inevitably required for dust emissions. The fire-induced modulations of the wind field can be transported up to some kilometers downstream of the fire area and are able to favor dust emissions also in some distance to the fire area. Although measurements showed already the importance of wildfires on dust emissions, pyro-convection is so far neglected as a dust emission process in atmosphere-aerosol models. The results presented in this study can be seen as the first step towards a systematic parameterization representing the connection between typical fire properties and related dust emissions, which eventually can be implemented in larger-scale aerosol models ultimately contributing to the reduction of uncertainties in the aerosol-climate feedback.

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