Analysis of the Self-Excited Dynamics of a Heavy-Duty Annular Combustion Chamber by Large-Eddy Simulation

2019 ◽  
Author(s):  
Vittorio Michelassi ◽  
Roberto Meloni ◽  
Giovanni Riccio ◽  
Gianni Ceccherini
Keyword(s):  
Combustion Chamber ◽  
Operating Conditions ◽  
Test Facility ◽  
Heavy Duty ◽  
Mean Flow ◽  
Combustion Dynamics ◽  
Eddy Simulation ◽  
Stable Operating ◽  
Large Eddy ◽  
Accuracy Data

Abstract This paper discusses the use of LES to predict the performance of an annular combustion chamber in stable operating conditions and in presence of self-exited dynamics. The availability of high-accuracy data taken in a full-scale combustion test facility allowed an extensive validation of the prediction capability. The analysis focuses on a small size heavy duty annular gas turbine whose size allows to test and compute the entire 360° combustion chamber. The comparison with measurements confirms that, if the correct operating conditions are implemented, LES is capable to discern between stable and unstable operating conditions, as well as predict several other engineering relevant parameters, although the model is sometime affected by a limited shift in frequency. The post processing of LES results in presence of combustion dynamics is not a trivial task. Here the results of the simulations have been post-processed by means of a triple decomposition method to determine a mean flow, a deterministic unsteady flow at the main instability frequency and a turbulent stochastic flow. Such decomposition indicated the instability triggering mechanism together with the cross-talk mechanism between different components. This approach is currently used for design phase, while further validation is on-going to include different geometries and operating conditions with the goal of reducing both risks and number of tests.

Analysis of the Self-Excited Dynamics of a Heavy-Duty Annular Combustion Chamber by Large-Eddy Simulation

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Roberto Meloni ◽  
Gianni Ceccherini ◽  
Vittorio Michelassi ◽  
Giovanni Riccio
Keyword(s):  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
Operating Conditions ◽  
Test Facility ◽  
Heavy Duty ◽  
Mean Flow ◽  
Combustion Dynamics ◽  
Eddy Simulation ◽  
Stable Operating ◽  
Large Eddy

Abstract This paper discusses the use of large eddy simulation (LES) to predict the performance of an annular combustion chamber in stable operating conditions and in the presence of self-exited dynamics. The availability of high-accuracy data taken in a full-scale combustion test facility allowed an extensive validation of the prediction capability. The analysis focuses on a small size heavy duty annular gas turbine whose size allows to test and compute the entire 360 deg combustion chamber. The comparison with measurements confirms that, if the correct operating conditions are implemented, LES is capable to discern between stable and unstable operating conditions, as well as predict several other engineering relevant parameters, although the model is sometime affected by a limited shift in frequency.The post processing of LES results in presence of combustion dynamics is not a trivial task. Here, the results of the simulations have been postprocessed by means of a triple decomposition method to determine a mean flow, a deterministic unsteady flow at the main instability frequency, and a turbulent stochastic flow. Such decomposition indicated the instability triggering mechanism together with the cross-talk mechanism between different components. This approach is currently used for design phase, while further validation is on-going to include different geometries and operating conditions with the goal of reducing both risks and number of tests.

RANS and Large Eddy Simulation of Internal Combustion Engine Flows—A Comparative Study

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Xiaofeng Yang ◽  
Saurabh Gupta ◽  
Tang-Wei Kuo ◽  
Venkatesh Gopalakrishnan
Keyword(s):  
Large Eddy Simulation ◽  
High Speed ◽  
Combustion Engine ◽  
Flow Analysis ◽  
Partial Geometry ◽  
Computational Domain ◽  
Mean Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Simulations

A comparative cold flow analysis between Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) cycle-averaged velocity and turbulence predictions is carried out for a single cylinder engine with a transparent combustion chamber (TCC) under motored conditions using high-speed particle image velocimetry (PIV) measurements as the reference data. Simulations are done using a commercial computationally fluid dynamics (CFD) code CONVERGE with the implementation of standard k-ε and RNG k-ε turbulent models for RANS and a one-equation eddy viscosity model for LES. The following aspects are analyzed in this study: The effects of computational domain geometry (with or without intake and exhaust plenums) on mean flow and turbulence predictions for both LES and RANS simulations. And comparison of LES versus RANS simulations in terms of their capability to predict mean flow and turbulence. Both RANS and LES full and partial geometry simulations are able to capture the overall mean flow trends qualitatively; but the intake jet structure, velocity magnitudes, turbulence magnitudes, and its distribution are more accurately predicted by LES full geometry simulations. The guideline therefore for CFD engineers is that RANS partial geometry simulations (computationally least expensive) with a RNG k-ε turbulent model and one cycle or more are good enough for capturing overall qualitative flow trends for the engineering applications. However, if one is interested in getting reasonably accurate estimates of velocity magnitudes, flow structures, turbulence magnitudes, and its distribution, they must resort to LES simulations. Furthermore, to get the most accurate turbulence distributions, one must consider running LES full geometry simulations.

Integrated Large Eddy Simulation of Combustor and Turbine Interactions: Effect of Turbine Stage Inlet Condition

2017 ◽  
Author(s):  
Florent Duchaine ◽  
Jérôme Dombard ◽  
Laurent Gicquel ◽  
Charlie Koupper
Keyword(s):  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
Rotor Blade ◽  
Turbine Stage ◽  
High Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Stator Vane ◽  
Specific Configuration ◽  
Inlet Conditions

To study the effects of combustion chamber dynamics on a turbine stage aerodynamics and thermal loads, an integrated Large-Eddy Simulation of the FACTOR combustion chamber simulator along with its high pressure turbine stage is performed and compared to a standalone turbine stage computation operated under the same mean conditions. For this specific configuration, results illustrate that the aerodynamic expansion of the turbine stage is almost insensitive to the inlet turbulent conditions. However, the temperature distribution in the turbine passages as well as on the stator vane and rotor blade walls are highly impacted by these inlet conditions: underlying the importance of inlet conditions in turbine stage computations and the potential of integrated combustion chamber / turbine simulations in such a context.

Towards Improved Prediction of Aero-Engine Combustor Performance Using Large Eddy Simulations

2008 ◽  
Author(s):  
S. James ◽  
M. S. Anand ◽  
B. Sekar
Keyword(s):  
Gas Turbine ◽  
Radial Profile ◽  
Design Tool ◽  
Operating Conditions ◽  
Outlet Temperature ◽  
Gas Turbine Combustor ◽  
Systematic Assessment ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Aero Engine

The paper presents an assessment of large eddy simulation (LES) and conventional Reynolds averaged methods (RANS) for predicting aero-engine gas turbine combustor performance. The performance characteristic that is examined in detail is the radial burner outlet temperature (BOT) or fuel-air ratio profile. Several different combustor configurations, with variations in airflows, geometries, hole patterns and operating conditions are analyzed with both LES and RANS methods. It is seen that LES consistently produces a better match to radial profile as compared to RANS. To assess the predictive capability of LES as a design tool, pretest predictions of radial profile for a combustor configuration are also presented. Overall, the work presented indicates that LES is a more accurate tool and can be used with confidence to guide combustor design. This work is the first systematic assessment of LES versus RANS on industry-relevant aero-engine gas turbine combustors.

Modelling Strategies for Large-Eddy Simulation of Lean Burn Spray Flames

2017 ◽  
Author(s):  
S. Puggelli ◽  
D. Bertini ◽  
L. Mazzei ◽  
A. Andreini
Keyword(s):  
Large Eddy Simulation ◽  
Ambient Pressure ◽  
Nox Reduction ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Lean Burn ◽  
Eddy Simulation ◽  
Flamelet Generated Manifold ◽  
Large Eddy ◽  
Modelling Strategies

During the last years aero-engines are progressively evolving toward design concepts that permit improvements in terms of engine safety, fuel economy and pollutant emissions. With the aim of satisfying the strict NOx reduction targets imposed by ICAO-CAEP, lean burn technology is one of the most promising solutions even if it must face safety concerns and technical issues. Hence a depth insight on lean burn combustion is required and Computational Fluid Dynamics (CFD) can be a useful tool for this purpose. In this work a comparison in Large-Eddy Simulation (LES) framework of two widely employed combustion approaches like the Artificially Thickened Flame (ATF) and the Flamelet Generated Manifold (FGM) is performed using ANSYS® Fluent v16.2. Two literature test cases with increasing complexity in terms of geometry, flow field and operating conditions are considered. Firstly, capabilities of FGM are evaluated on a single swirler burner operating at ambient pressure with a standard pressure atomizer for spray injection. Then a second test case, operated at 4 bar, is simulated. Here kerosene fuel is burned after an injection through a prefilming airblast atomizer within a co-rotating double swirler. Obtained comparisons with experimental results show the different capabilities of ATF and FGM in modelling the partially-premixed behaviour of the flame and provides an overview of the main strengths and limitations of the modelling strategies under investigation.

Large-Eddy Simulation of an Integrated High-Pressure Compressor and Combustion Chamber of a Typical Turbine Engine Architecture

2020 ◽  
Author(s):  
Carlos Pérez Arroyo ◽  
Jérôme Dombard ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Nicolas Odier ◽  
...  
Keyword(s):  
High Pressure ◽  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
High Amplitude ◽  
Turbine Engine ◽  
Eddy Simulation ◽  
High Pressure Compressor ◽  
Large Eddy ◽  
Pressure Perturbations ◽  
Pressure Compressor

Abstract The design optimization of aviation propulsion systems by means of computational fluid dynamics is key to increase their efficiency and reduce pollutant and noise emissions. The recurrent increase in available computing power allows nowadays to perform unsteady high-fidelity computations of the different components of a gas turbine. However, these simulations are often made independently of each other and they only share average quantities at interfaces. In this work, the methodology and first results for a sectoral large-eddy simulation of an integrated high-pressure compressor and combustion chamber of a typical turbine engine architecture is proposed. In the simulation, the compressor is composed of one main blade and one splitter blade, two radial diffuser vanes and six axial diffuser vanes. The combustion chamber is composed of the contouring casing, the flame-tube and a T-shaped vaporizer. This integrated computation considers a good trade-off between accuracy of the simulation and affordable CPU cost. Results are compared between the stand-alone combustion chamber simulation and the integrated one in terms of global, integral and average quantities. It is shown that pressure perturbations generated by the interaction of the impeller blades with the diffuser vanes are propagated through the axial diffuser and enter the combustion chamber through the dilution holes and the vaporizer. Due to the high amplitude of the pressure perturbations, several variables are perturbed at the blade-passing frequency and multiples. This is also reflected on combustion where two broadband peaks appear for the global heat release.

Loss Predictions in the High-Pressure Film-Cooled Turbine Vane of the FACTOR Project by Mean of Wall-Modeled Large Eddy Simulation

2020 ◽  
Author(s):  
Mael Harnieh ◽  
Nicolas Odier ◽  
Jérôme Dombard ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Spatial Distribution ◽  
Large Eddy Simulation ◽  
Film Cooling ◽  
Total Pressure ◽  
Mean Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbine Vane

Abstract The use of numerical simulations to design and optimize turbine vane cooling requires precise prediction of the fluid mechanics and film cooling effectiveness. This results in the need to numerically identify and assess the various origins of the losses taking place in such systems and if possible in engine representative conditions. Large-Eddy Simulation (LES) has shown recently its ability to predict turbomachinery flows in well mastered academic cases such as compressor or turbine cascades. When it comes to industrial representative configurations, the geometrical complexities, high Reynolds and Mach numbers as well as boundary condition setup lead to an important increase of CPU cost of the simulations. To evaluate the capacity of LES to predict film cooling effectiveness as well as to investigate the loss generation mechanisms in a turbine vane in engine representative conditions, a wall-modeled LES of the FACTOR film-cooled nozzle is performed. After the comparison of integrated values to validate the operating point of the vanes, the mean flow structure is investigated. In the coolant film, a strong turbulent mixing process between coolant and hot flows is observed. As a result, the spatial distribution of time-averaged vane surface temperature is highly heterogeneous. Comparisons with the experiment show that the LES prediction fairly reproduces the spatial distribution of the adiabatic film effectiveness. The loss generation in the configuration is then investigated. To do so, two methodologies, i.e, performing balance of total pressure in the vanes wakes as mainly used in the literature and Second Law Analysis (SLA) are evaluated. Balance of total pressure without the contribution of thermal effects only highlights the losses generated by the wakes and secondary flows. To overcome this limitation, SLA is adopted by investigating loss maps. Thanks to this approach, mixing losses are shown to dominate in the coolant film while aerodynamic losses dominate in the coolant pipe region.

Lean-Burn Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition

2018 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Fuel Injector ◽  
Heavy Duty ◽  
Lean Burn ◽  
Spark Timing ◽  
Heavy Duty Diesel

Increased utilization of natural-gas (NG) in the transportation sector can decrease the use of petroleum-based fuels and reduce greenhouse-gas emissions. Heavy-duty diesel engines retrofitted to NG spark ignition (SI) can achieve higher efficiencies and low NOx, CO, and HC emissions when operated under lean-burn conditions. To investigate the SI lean-burn combustion phenomena in a bowl-in-piston combustion chamber, a conventional heavy-duty direct-injection CI engine was converted to SI operation by replacing the fuel injector with a spark plug and by fumigating NG in the intake manifold. Steady-state engine experiments and numerical simulations were performed at several operating conditions that changed spark timing, engine speed, and mixture equivalence ratio. Results suggested a two-zone NG combustion inside the diesel-like combustion chamber. More frequent and significant late burn (including double-peak heat release rate) was observed for advanced spark timing. This was due to the chamber geometry affecting the local flame speed, which resulted in a faster and thicker flame in the bowl but a slower and thinner flame in the squish volume. Good combustion stability (COVIMEP < 3 %), moderate rate of pressure rise, and lack of knocking showed promise for heavy-duty CI engines converted to NG SI operation.

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