scholarly journals Soot Emission Simulations of a Single Sector Model Combustor Using Incompletely Stirred Reactor Network Modeling

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Savvas Gkantonas ◽  
Jenna M. Foale ◽  
Andrea Giusti ◽  
Epaminondas Mastorakos
Keyword(s):  
Mixture Fraction ◽  
Computational Cost ◽  
Chemical Mechanism ◽  
Lean Burn ◽  
Sector Model ◽  
Stirred Reactor ◽  
Low Emission ◽  
Aero Engine ◽  
Complex Chemistry ◽  
Reactor Network

Abstract The simulation of soot evolution is a problem of relevance for the development of low-emission aero-engine combustors. Apart from detailed CFD approaches, it is important to also develop models with modest computational cost so that a large number of geometries can be explored, especially in view of the need to predict engine-out soot particle size distributions (PSDs) to meet future regulations. This paper presents an approach based on Incompletely Stirred Reactor Network (ISRN) modeling that simplifies calculations, allowing for the use of very complex chemistry and soot models. The method relies on a network of incompletely stirred reactors (ISRs), which are inhomogeneous in terms of mixture fraction but characterized by homogeneous conditional averages, with the conditioning performed on the mixture fraction. The ISRN approach is demonstrated here for a single sector lean-burn model combustor operating on Jet-A1 fuel in pilot-only mode, for which detailed CFD and experimental data are available. Results show that reasonable accuracy is obtained at a significantly reduced computational cost. Real fuel chemistry and a detailed physicochemical sectional soot model are consequently employed to investigate the sensitivity of ISRN predictions to the chosen chemical mechanism and provide an estimate of the soot PSD at the combustor exit.

scholarly journals Soot Emission Simulations of a Single Sector Model Combustor Using Incompletely Stirred Reactor Network Modeling

2020 ◽  
Author(s):  
Savvas Gkantonas ◽  
Jenna M. Foale ◽  
Andrea Giusti ◽  
Epaminondas Mastorakos
Keyword(s):  
Particle Size ◽  
Soot Particle ◽  
Mixture Fraction ◽  
Computational Cost ◽  
Chemical Mechanism ◽  
Lean Burn ◽  
Sector Model ◽  
Stirred Reactor ◽  
Complex Chemistry ◽  
Reactor Network

Abstract The simulation of soot evolution is a problem of relevance for the development of low-emission aero-engine combustors. Apart from detailed CFD approaches, it is important to also develop models with modest computational cost so a large number of geometries can be explored, especially in view of the need to predict engine-out soot particle size distributions (PSDs) to meet future regulations. This paper presents an approach based on Incompletely Stirred Reactor Network (ISRN) modeling that simplifies calculations, allowing for the use of very complex chemistry and soot models. The method relies on a network of Incompletely Stirred Reactors (ISRs), which are inhomogeneous in terms of mixture fraction but characterized by homogeneous conditional averages, with the conditioning performed on the mixture fraction. The ISRN approach is demonstrated here for a single sector lean-burn model combustor operating on Jet-A1 fuel in pilot-only mode, for which detailed CFD and experimental data are available. Results show that reasonable accuracy is obtained at a significantly reduced computational cost. Real fuel chemistry and a detailed physicochemical sectional soot model are consequently employed to investigate the sensitivity of ISRN predictions to the chemical mechanism chosen and to provide an estimate of the soot particle size distribution at the combustor exit.

Flamelet Versus Detailed Chemistry LES for a Liquid Fueled Gas-Turbine Combustor: A Comparison of Accuracy and Computational Cost

2021 ◽  
Author(s):  
Megan Karalus ◽  
Piyush Thakre ◽  
Graham Goldin ◽  
Dustin Brandt
Keyword(s):  
Gas Turbine ◽  
Computational Cost ◽  
Chemical Mechanism ◽  
Lagrangian Model ◽  
Radial Temperature ◽  
Detailed Chemistry ◽  
Combustion Models ◽  
Flamelet Generated Manifold ◽  
Unburned Hydrocarbons ◽  
Complex Chemistry

Abstract A Honeywell liquid-fueled gas turbine test combustor, at idle conditions is numerically investigated in Simcenter STAR-CCM+. This work presents Large Eddy Simulation (LES) results using both the Flamelet Generated Manifold (FGM) and Complex Chemistry (CC) combustion models. Both take advantage of a hybrid chemical mechanism (HyChem) which has previously demonstrated very good accuracy for real fuels such as Jet-A with only 47 species. The objective of this work is to investigate the ability of FGM and CC to capture pollutant formation in an aero-engine. Comparisons for NOx, CO, Unburned Hydrocarbons, and Soot are made, along with the radial temperature pro?le. Computational costs are assessed by comparing the performance and scalability of the simulations with each of the combustion models. It is found that the CC case with clustering can reproduce nearly identical results to that without acceleration if CO is added as a clustering variable. With the Lagrangian model settings chosen for this study, the CC results compared more favorably with the experimental data than FGM, however there is uncertainty in the secondary breakup parameters. Sensitivity of the results to a key parameter in the spray breakup model are provided for both FGM and CC. By varying this breakup rate, the FGM case can predict CO, NOx, and Unburned Hydrocarbons equally well. The smoke number, however, is predicted most accurately by CC. The cost for running CC with clustering is found to be about 4 times that of FGM for this combustor and chemical mechanism.

The Influence of Dump Gap on Aerodynamic Performance of a Low-Emission Combustor Dump Diffuser

2013 ◽  
Author(s):  
Pei He ◽  
Jianqin Suo ◽  
Kaicheng Xie ◽  
Sutao Chen ◽  
Shanping Shen ◽  
...  
Keyword(s):  
Aerodynamic Performance ◽  
Loss Coefficient ◽  
Sudden Expansion ◽  
Lean Burn ◽  
Fuel Injectors ◽  
Flame Tube ◽  
Gap Ratio ◽  
Low Emission ◽  
Aero Engine ◽  
Low Nox Emission

In modern civil aero-engine gas turbine combustors, lean burn technology is widely adopted to achieve low NOx emission target. As such, most of the flow issued from the compressor is expected to flow into the combustor dome, compared with a typical value of 30% in conventional combustors. To accommodate this increased mass flow rate, lean module fuel injectors should be significantly larger than their conventional counterparts. This will change the combustor external aerodynamic layout such as a deeper flame tube together with an enlarged dump gap, which is the distance between the pre-diffuser outlet and the flame tube. The modification will potentially increase the total pressure loss due to enlarged turning within the dump region. Thus it is important to investigate the influence of the dump gap on the aerodynamic performance of the diffuser. Experiments have been carried out and presented in this paper. The tested geometry comprises a pre-diffuser, followed by a sudden expansion through which the main flow is divided into three passages, i.e., the combustor dome, the outer passage, and the inner passage. Up to 60% of the airflow issued from the pre-diffuser flows into the dome. It is found that the loss coefficient of pre-diffuser decreases as dump gap increases. The overall loss coefficient is relatively high when the dump gap ratio is smaller than 1.2 or larger than 2.8, and is relatively low and insensitive to dump gap with intermediate dump gaps. It is also found that the proportion of the pre-diffuser loss to the overall loss is larger than conventional dump diffuser.

Stability and Emissions of a Lean Pre-Mixed Combustor with Rich Catalytic/Lean-burn Pilot

2014 ◽  
Vol 12 (1) ◽  
pp. 77-89 ◽  
Author(s):  
Valeria Di Sarli
Keyword(s):  
Methane Combustion ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Lean Burn ◽  
Stirred Reactor ◽  
Highly Sensitive ◽  
Pilot Fuel ◽  
Homogeneous Reactor ◽  
Reactor Network ◽  
Operating Window

Abstract In this work, a reactor network model was developed to study homogeneous gas-phase methane combustion taking place under typical operating conditions of lean pre-mixed combustors piloted by rich catalytic/lean-burn (RCL) systems. In particular, the thermo-kinetic interaction between the pilot stream (i.e. the stream exiting the RCL stage) and the main feeding stream to the homogeneous reactor was investigated in terms of combustion stability and emissions. The homogeneous combustor was modeled as a perfectly stirred reactor (PSR). The pilot stream was mixed with the main feeding stream prior to entering the PSR. Numerical results have shown that the opportunity to stabilize combustion is strongly linked to the presence of hydrogen in the pilot stream. Combustion stability is highly sensitive to variations in fuel split between catalytic pilot and homogeneous reactor. The increase in pilot fuel split (and, thus, in the inlet hydrogen concentration to the PSR) enlarges the operating window of stable combustion (in terms of higher heat losses, lower preheat temperatures and lower residence times), while still achieving NOx and CO emissions lower than 9 ppm (at 15% O2). These results highlight the potential of the RCL technology as a valuable alternative to conventional diffusion flame-based pilots.

Large Eddy Simulation of ALSTOM’s Reheat Combustor Using Tabulated Chemistry and Stochastic Fields-Combustion Model

2014 ◽  
Author(s):  
Rohit Kulkarni ◽  
Birute Bunkute ◽  
Fernando Biagioli ◽  
Michael Duesing ◽  
Wolfgang Polifke
Keyword(s):  
Turbulent Flows ◽  
Mixture Fraction ◽  
Turbulent Flame ◽  
Computational Cost ◽  
Chemical Mechanism ◽  
Combustion Model ◽  
Atmospheric Conditions ◽  
Stochastic Fields ◽  
Tabulated Chemistry ◽  
Large Eddy

Large Eddy Simulations (LES) of natural gas ignition and combustion in turbulent flows are performed using a novel combustion model based on a composite progress variable, a tabulated chemistry ansatz and the stochastic-fields turbulence-chemistry interaction model. It is a significant advantage of this approach that it can be applied to industrial configurations with multi-stream mixing at relatively low computational cost and modeling complexity. The computational cost is independent of the chemical mechanism or the type of fuel, but increases linearly with the number of streams. The model is validated successfully against the Cabra methane flame and Delft Jet in Hot Coflow (DJFC) flame. Both cases constitute fuel jets in a vitiated coflow. The DJFC flame coflow has a non-uniform mixture of air and hot gases. The model considers this non-uniformity by an additional mixture fraction dimension, emulating a ternary mixing case. The model not only predicts flame location, but also the temperature distribution quantitatively. The LES combustion model is further extended to consider four stream mixing. It has been successfully validated for ALSTOM’s reheat combustor at atmospheric conditions. Compared to the past steady-state RANS (Reynolds Averaged Navier-Stokes) simulations [1], the LES simulations provide an even better understanding of the turbulent flame characteristics, which helps in the burner optimization.

Investigation of the Combustion Performance in a Three-Nozzle RQL Combustor

2016 ◽  
Author(s):  
Bing Ge ◽  
Yongbin Ji ◽  
Shusheng Zang ◽  
Yongwen Yuan ◽  
Jianhua Xin
Keyword(s):  
Air Flow ◽  
Lean Burn ◽  
Uniformity Coefficient ◽  
Performance And Emission ◽  
Combustion Performance ◽  
Sector Model ◽  
Exhaust Temperature ◽  
Whole Process ◽  
Axial Temperature ◽  
Two Peaks

RQL (Rich-burn/Quick-quench/Lean-burn) is a candidate to support fuel flexible stationary power generation. The equivalence ratio of rich-burn zone (Φr) and the quench air flow are paramount for implantation of the whole process. In this paper, an experimental test stand with multi-sector model combustor was established. Rich premixed combustion were used in rich zone. The experiments which pay attention to the impacts of Φr and quench air flow on the combustion performance and emission are conducted. The results show that the flame in RQL combustor is segmented when Φr >1.4, presenting flameless combustion in rich zone and a pale blue flame in lean zone. Axial temperature distribution is M-type. Two peaks appear at the head and tail of the combustion chamber, and the valley is located in the quench zone. The concentration of CO decreases rapidly in quench zone because of the injection of quench air. However, the concentration of NOx increases quickly at the same time. The outlet emissions of CO and NOx in RQL combustor are maintained at low level (<20ppm@15%O2). With a decrease of Φr from 1.4 to 1.2, the emission of NOx increases, and the emission of CO decreases. With jet-to-mainstream mass-flow ratio increases from 1.28 to 2.22., the concentration of NOx in outlet declines gently, but the CO emission increase. The average exhaust temperature depresses gradually, and the uniformity coefficient of exhaust temperature increases.

A Study of the NOx Emission in a Regenerative Industrial Furnace

2001 ◽  
Author(s):  
Qing Jiang ◽  
Chao Zhang
Keyword(s):  
Mixture Fraction ◽  
Combustion Process ◽  
Nox Emission ◽  
Moment Closure ◽  
Combustion Model ◽  
Industrial Furnace ◽  
Low Emission ◽  
Reduction Of Nox ◽  
Closure Method ◽  
Probability Density Function Pdf

Abstract A study of the nitrogen oxides (NOx) emission and combustion process in a gas-fired regenerative, high temperature, low emission industrial furnace has been carried out numerically. The effect of two additives, methanol (CH3OH) and hydrogen peroxide (H2O2), to fuel on the NOx emission has been studied. A moment closure method with the assumed β probability density function (PDF) for mixture fraction is used in the present work to model the turbulent non-premixed combustion process in the furnace. The combustion model is based on the assumption of instantaneous full chemical equilibrium. The results showed that CH3OH is effective in the reduction of NOx in a regenerative industrial furnace. However, H2O2 has no significant effect on the NOx emission.

Scale Resolving CFD Investigations of Aerothermal Field and Emissions of a Lean Burn Aeroengine Combustor

2021 ◽  
Author(s):  
S. Paccati ◽  
L. Mazzei ◽  
A. Andreini ◽  
S. Patil ◽  
S. Shrivastava ◽  
...  
Keyword(s):  
Pressure Fluctuations ◽  
Computational Cost ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Tetrahedral Mesh ◽  
Main Stream ◽  
Nox Emissions ◽  
Lean Burn ◽  
Emission Data ◽  
Hexahedral Elements

Abstract Due to the increasingly stringent international limitations in terms of NOx emissions, the development of new combustor concepts has become extremely important in order for aircraft engines to comply with these regulations. In this framework, lean-burn technology represents a promising solution and several studies and emission data from production engines have proven that it is more promising in reducing NOx emissions than rich-burn technology. Considering the drawbacks of this combustion strategy (flame stabilization, flashback or blowout or the occurrence of large pressure fluctuations causing thermo-acoustics phenomena) as well as the difficulties and the high costs related to experimental campaigns at relevant operating conditions, Computational Fluid Dynamics (CFD) plays a key role in deepening understanding of the complex phenomena that are involved in such reactive conditions. During last years, large research efforts have been devoted to develop new advanced numerical strategies for high-fidelity predictions in simulating reactive flows that feature strong unsteadiness and high levels of turbulence intensity with affordable computational resources. In this sense, hybrid RANS-LES models represent a good compromise between accurate prediction of flame behaviour and computational cost with respect to fully-LES approaches. Stress-Blended Eddy Simulation (SBES) is a new global hybrid RANS-LES methodology which ensures an improved shielding of RANS boundary layers and a more rapid RANS-LES “transition” compared to other hybrid RANS-LES formulations. In the present work, a full annular aeronautical lean-burn combustor operated at real conditions is investigated from a numerical point of view employing the new SBES approach using poly-hexcore mesh topology, which allows to adopt an isotropic grid for more accurate scale-resolving calculations by means of fully regular hexahedral elements in the main stream. The results are compared to experimental data and to previous reference numerical results obtained with Scale Adaptive Simulation formulation on a tetrahedral mesh grid in order to underline the improvements achieved with the new advanced numerical setup.

Flow Field and Hot Streak Migration Through a High Pressure Cooled Vanes With Representative Lean Burn Combustor Outflow

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Tommaso Bacci ◽  
Tommaso Lenzi ◽  
Alessio Picchi ◽  
Lorenzo Mazzei ◽  
Bruno Facchini
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Flow Field ◽  
Fuel Injection ◽  
Leading Edge ◽  
Flame Stabilization ◽  
Lean Burn ◽  
Aero Engine ◽  
University Of Florence ◽  
Hot Streak

Modern lean burn aero-engine combustors make use of relevant swirl degrees for flame stabilization. Moreover, important temperature distortions are generated, in tangential and radial directions, due to discrete fuel injection and liner cooling flows respectively. At the same time, more efficient devices are employed for liner cooling and a less intense mixing with the mainstream occurs. As a result, aggressive swirl fields, high turbulence intensities, and strong hot streaks are achieved at the turbine inlet. In order to understand combustor-turbine flow field interactions, it is mandatory to collect reliable experimental data at representative flow conditions. While the separated effects of temperature, swirl, and turbulence on the first turbine stage have been widely investigated, reduced experimental data is available when it comes to consider all these factors together.In this perspective, an annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at the THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners, and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central NGV aligned with the central swirler. In order to generate representative conditions, a heated mainstream passes though the axial swirlers of the combustor simulator, while the effusion cooled liners are fed by air at ambient temperature. The resulting flow field exiting from the combustor simulator and approaching the cooled vane can be considered representative of a modern Lean Burn aero engine combustor with swirl angles above ±50 deg, turbulence intensities up to about 28% and maximum-to-minimum temperature ratio of about 1.25. With the final aim of investigating the hot streaks evolution through the cooled high pressure vane, the mean aerothermal field (temperature, pressure, and velocity fields) has been evaluated by means of a five-hole probe equipped with a thermocouple and traversed upstream and downstream of the NGV cascade.

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