scholarly journals Massively Parallel Large Eddy Simulation of Rotating Turbomachinery for Variable Speed Gas Turbine Engine Operation

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 703
Author(s):  
Nishan Jain ◽  
Luis Bravo ◽  
Dokyun Kim ◽  
Muthuvel Murugan ◽  
Anindya Ghoshal ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Massively Parallel ◽  
Rotor Speed ◽  
Tip Leakage Flow ◽  
Engine Operation ◽  
Large Eddy ◽  
The Impact

Gas turbine engines are required to operate at both design and off-design conditions that can lead to strongly unsteady flow-fields and aerodynamic losses severely impacting performance. Addressing this problem requires effective use of computational fluid dynamics tools and emerging models that resolve the large scale fields in detail while accurately modeling the under-resolved scale dynamics. The objective of the current study is to conduct massively parallel large eddy simulations (LES) of rotating turbomachinery that handle the near-wall dynamics using accurate wall models at relevant operating conditions. The finite volume compressible CharLES solver was employed to conduct the simulations over moving grids generated through Voronoi-based unstructured cells. A grid sensitivity analysis was carried out first to establish reliable parameters and assess the quality of the results. LES simulations were then conducted to understand the impact of blade tip clearance and operating conditions on the stage performance. Variations in tip clearance of 3% and 16% chord were considered in the analysis. Other design points included operation at 100% rotor speed and off-design conditions at 75% and 50% of the rotor speed. The simulation results showed that the adiabatic efficiency improves dramatically with reduction in tip gap due to the decrease in tip leakage flow and the resulting flow structures. The analysis also showed that the internal flow becomes highly unsteady, undergoing massive separation, as the rotor speed deviates from the design point. This study demonstrates the capability of the framework to simulate highly turbulent unsteady flows in a rotating turbomachinery environment. The results provide much needed insight and massive data to investigate novel design concepts for the US Army Future Vertical Lift program.

Active Control of Fuel Splits in Gas Turbine DLE Combustion Systems

2007 ◽  
Author(s):  
Ghenadie Bulat ◽  
Dorian Skipper ◽  
Robin McMillan ◽  
Khawar Syed
Keyword(s):  
Gas Turbine ◽  
Active Control ◽  
Control Algorithm ◽  
Pressure Fluctuations ◽  
Stability Limit ◽  
Operating Conditions ◽  
Direct Result ◽  
Operational Parameter ◽  
Engine Operation ◽  
The Impact

This paper presents a system for the active control of the fuel split within a two-stream Dry Low Emissions (DLE) gas turbine. The system adjusts the fuel split based upon the amplitude of combustor pressure fluctuations and burner metal temperature. The active control system, its implementation and its performance during engine tests on Siemens SGT-200 is described. The paper describes the active fuel split control algorithm. Engine test results are then presented for steady and transient loads with different rates of change of the engine operation temperature, including rapid load acceptance and load shedding. Additionally, cycling operating conditions were tested to evaluate the performance of the algorithm in typical island mode and mechanical drive applications. The active control algorithm was successful in providing stable and reliable control of the turbine allowing very low emissions levels to be attained without manual intervention. In fact it allows areas to be reached that until now were excluded. The impact of operational parameter changes (e.g. load change, ambient temperature, fuel composition etc.) on the engine operability proved the active control software’s ability to respond seamlessly. In addition, it prevented flameout and/or high pressure fluctuation while keeping burner temperatures within limits. Recorded emissions showed a reduction in NOx was achieved when the fuel split was controlled by the algorithm compared to standard operation. This was a direct result of the algorithm successfully identifying the lean stability limit and operating close to it.

Numerical Study of Influence of Rotor Tip Gap Increase due to Age Deterioration in 3-Stage Gas Turbine

2020 ◽  
Author(s):  
Koichi Yonezawa ◽  
Junichi Sakamoto ◽  
Kazuyasu Sugiyama ◽  
Shuichi Ohmori ◽  
Shuichi Umezawa
Keyword(s):  
Gas Turbine ◽  
Rotor Blade ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Age Related ◽  
Balance Analysis ◽  
Blade Tip

Abstract Influences of age-related deterioration on the increase in rotor tip gap width are discussed numerically. In the gas turbine examined in the present study, there are two kinds of geometries around the rotor blade tip. In the first stage, there is clearance between the blade tip and the casing without any seal structures. On the other hand, there is a shroud and seal fin on the rotor blade tip. The blade geometries were measured using a 3-D scanner in a working power plant, and the tip clearances were varied by changing the casing contour. Steady-state CFD simulations were carried out. Tip gap widths were varied by shifting the casing wall. For simplicity, the blade geometries were not changed. The influence of tip clearance was examined by changing the geometries in each stage separately. Boundary conditions were determined using the previously developed hybrid method of heat balance analysis and CFD simulation, which can simulate the operating conditions of a working gas turbine. The results showed that the turbine performance degradation could spread to the following stage. Observation of entropy fields revealed that the increase in the tip leakage flow affected the flow in the following nozzle, and the loss increased.

The Impact of Model Assumptions on the CFD Assisted Design of Gas Turbine Packages

2019 ◽  
Author(s):  
Gabriele Lucherini ◽  
Vittorio Michelassi ◽  
Stefano Minotti
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Structural Integrity ◽  
Ventilation System ◽  
Gas Diffusion ◽  
Computational Effort ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Fuel Gas ◽  
The Impact

Abstract A gas turbine is usually installed inside a package to reduce the acoustics emissions and protect against adverse environmental conditions. An enclosure ventilation system is keeps temperatures under acceptable limits and dilutes any potentially explosive accumulation of gas due to unexpected leakages. The functional and structural integrity as well as certification needs of the instrumentation and auxiliary systems in the package require that temperatures do not exceed a given threshold. Moreover, accidental fuel gas leakages inside the package must be studied in detail for safety purposes as required by ISO21789. CFD is routinely used in BHGE (Baker Hughes, a GE Company) to assist in the design and verification of the complete enclosure and ventilation system. This may require multiple CFD runs of very complex domains and flow fields in several operating conditions, with a large computational effort. Modeling assumptions and simulation set-up in terms of turbulence and thermal models, and the steady or unsteady nature of the simulations must be carefully assessed. In order to find a good compromise between accuracy and computational effort the present work focuses on the analysis of three different approaches, RANS, URANS and Hybrid-LES. The different computational approaches are first applied to an isothermal scaled-down model for validation purposes where it was possible to determine the impact of the large-scale flow unsteadiness and compare with measurements. Then, the analysis proceeds to a full-scale real aero-derivative gas turbine package. in which the aero and thermal field were investigated by a set of URANS and Hybrid-LES that includes the heat released by the engine. The different approaches are compared by analyzing flow and temperature fields. Finally, an accidental gas leak and the subsequent gas diffusion and/or accumulation inside the package are studied and compared. The outcome of this work highlights how the most suitable approach to be followed for industrial purposes depends on the goal of the CFD study and on the specific scenario, such as NPI Program or RQS Project.

Towards Large Eddy Simulation of Rotating Turbomachinery for Variable Speed Gas Turbine Engine Operation

2019 ◽  
Author(s):  
Nishan Jain ◽  
Luis Bravo ◽  
Dokyun Kim ◽  
Muthuvel Murugan ◽  
Anindya Ghoshal ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbine Engine ◽  
Operating Conditions ◽  
Variable Speed ◽  
Solution Quality ◽  
Engine Operation ◽  
Turbine Engine ◽  
Design Point ◽  
Large Eddy ◽  
Flow Through

Abstract In this work, massively parallel wall-modeled Large Eddy Simulations (LES) are conducted to simulate flow through a single stage power turbine sector of a gas-turbine engine under realistic operating conditions. The numerical framework in the current work uses finite volume based compressible CharLES solver that utilizes a moving Voronoi diagram based grid generation. To test grid sensitivity and evaluate the capability of the solver in predicting turbomachinery flows, three grids of varying resolution are used to simulate flow through the baseline gas-turbine under design operating conditions. After assessing the flow solution quality and establishing simulation parameters, LES simulations are conducted to investigate the performance of gas-turbine at off-design conditions. The conditions include the rotor design point at 100% speed, and off-design points at 75%, and 50% speeds subject to high temperatures from the combustor exit flow. The results showed that the internal flow becomes highly unsteady as the rotational speed of rotor deviates from the design point leading to reduced aerodynamic performance. This study demonstrates that the current framework is able to robustly simulate the unsteady flow in a three-dimensional moving rotor environment towards the design of variable speed gas-turbine engines for US Army Future Vertical Lift program.

Analysis of Solid Particle Ingestion and Dynamics in a Turbomachine Using Large-Eddy Simulation

2019 ◽  
Author(s):  
Benjamin Martin ◽  
Martin Thomas ◽  
Jérôme Dombard ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Large Eddy Simulation ◽  
Gas Turbine ◽  
Solid Particle ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Lagrangian Formalism ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy

Abstract Erosion of compressor and turbine blades operating in extreme environment fouled with sand particles, ash or soot is a serious problem for gas turbine manufacturers and users. Indeed, operation of a gas turbine engine in such hostile conditions leads to drastic degradation of the aerodynamic performance of the components, mostly through surface roughness modification, tip clearance height increase or blunting of blade leading edges. To evaluate associated risks, the computation of particle trajectories and impacts through multiple turbomachinery stages by Computational Fluid Dynamics (CFD) seems a decent path but remains a challenge. The numerical prediction of complex turbulent flows in compressors and turbines is however necessary in such a context and validations are still required. Recently, Large-Eddy Simulation (LES) has shown promising results for compressor and turbine configurations for a wide range of operating conditions at an acceptable cost. With this in mind, this article presents the assessment of a LES solver able to treat turbomachine configurations to predict solid particle motion. To do so, the governing equations of particle dynamics are introduced using the Lagrangian formalism and are solved to compute locations and conditions of impact, namely particle velocity, angle and radius. The fully unsteady and coupled strategy is applied to blade geometries for studying the main areas and conditions of impacts obtained with LES. For comparison, a one-way coupling computation based on a mean steady flow field where only the Lagrangian particles are advanced in time is performed to evaluate the gain and drawbacks of both methods.

Unsteady 3D Simulation of a Jet Fan With Symmetric Blades

2006 ◽  
Author(s):  
J. M. Ferna´ndez Oro ◽  
K. M. Argu¨elles Di´az ◽  
C. Santolaria Morros
Keyword(s):  
Tangential Velocity ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Wake Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Jet Fan ◽  
The Impact

This work develops the numerical modeling of a monoplane axial jet fan with symmetric blades. The goal of the study is the simulation of the flow inside a rotor with elliptic airfoils, where the Kutta condition cannot be satisfied. The unsteady 3D model includes tip clearance gridding and a sliding mesh technique to simulate transient effects. The flow patterns inside the blade passage and the wake-core structure will be studied at design operating conditions. Also, the interaction of the tip leakage flow with time-averaged structures will be analyzed in detail. Therefore, the impact of the tip vortex in the mean time performance of the jet fan will be introduced. The investigation shows how the tip leakage vortex modifies the blade loading on the suction surface. The leakage flow rolls-up in a vortical structure at the suction side, establishing a mixing mechanism that produces a low axial velocity region. As a result, the adverse pressure gradient is enhanced and a major flow separation overcomes. This feature is especially critical in case of a rotor with symmetric blades, where the flow is always detached at the trailing edge. The simulation is carried out using a commercial code, FLUENT, which resolves the Navier-Stokes set of equations. An extremely high dense mesh is introduced in the model, so tip leakage is expected to be well-captured. In addition, fully-developed detachment of the boundary layer requires superior discretizations and high quality meshes, so restrictive y+ criteria have been employed for both endwall boundaries and blade surfaces. Turbulence modeling is closed using URANS models. The Reynolds Stress Model (RSM) has been employed because of its suitable predictions for rotating flow passages. In addition, this model considers anisotropic turbulence, and effects of curvature and rotation are directly addressed in the transport equations. Therefore, swirl effects of the tip vortex are expected to be well-captured. The numerical results are compared with previous experimental data of velocity fields to validate the simulation. Axial and tangential velocity profiles were obtained using a five-hole probe. Complementary, the instantaneous wake flow structure was measured with a dual hot wire anemometer.

scholarly journals A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4136
Author(s):  
Clemens Gößnitzer ◽  
Shawn Givler
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Negative Impact ◽  
Operating Conditions ◽  
Engine Operation ◽  
Gas Engine ◽  
Cycle Simulation ◽  
Simulation Results ◽  
The Impact

Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier–Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are taken from a snapshot from a different cycle. Such a combination yields a new snapshot. With the combined snapshot, the simulation is continued until the end of combustion. The results obtained with combined snapshots show that the velocity field seems to have the highest impact on CCV. Turbulence intensity, quantified by the turbulent kinetic energy and turbulent kinetic energy dissipation rate, has a similar value for all snapshots. Thus, their impact on CCV is small compared to the flow field. This novel methodology is very flexible and allows investigation of the sources of CCV which have been difficult to investigate in the past.

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.

The Effect of Heat Transfer Coefficient Increase on Tip Clearance Control in H.P. Compressors in Gas Turbine Engine

2013 ◽  
Author(s):  
Godwin Ita Ekong ◽  
Christopher A. Long ◽  
Peter R. N. Childs
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Time Constant ◽  
Gas Turbine Engine ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Test Facility ◽  
Turbine Engine

Compressor tip clearance for a gas turbine engine application is the radial gap between the stationary compressor casing and the rotating blades. The gap varies significantly during different operating conditions of the engine due to centrifugal forces on the rotor and differential thermal expansions in the discs and casing. The tip clearance in the axial flow compressor of modern commercial civil aero-engines is of significance in terms of both mechanical integrity and performance. In general, the clearance is of critical importance to civil airline operators and their customers alike because as the clearance between the compressor blade tips and the casing increases, the aerodynamic efficiency will decrease and therefore the specific fuel consumption and operating costs will increase. This paper reports on the development of a range of concepts and their evaluation for the reduction and control of tip clearance in H.P. compressors using an enhanced heat transfer coefficient approach. This would lead to improvement in cruise tip clearances. A test facility has been developed for the study at the University of Sussex, incorporating a rotor and an inner shaft scaled down from a Rolls-Royce Trent aero-engine to a ratio of 0.7:1 with a rotational speed of up to 10000 rpm. The idle and maximum take-off conditions in the square cycle correspond to in-cavity rotational Reynolds numbers of 3.1×106 ≤ Reφ ≤ 1.0×107. The project involved modelling of the experimental facilities, to demonstrate proof of concept. The analysis shows that increasing the thermal response of the high pressure compressor (HPC) drum of a gas turbine engine assembly will reduce the drum time constant, thereby reducing the re-slam characteristics of the drum causing a reduction in the cold build clearance (CBC), and hence the reduction in cruise clearance. A further reduction can be achieved by introducing radial inflow into the drum cavity to further increase the disc heat transfer coefficient in the cavity; hence a further reduction in disc drum time constant.

scholarly journals A Trade-Off Study of Rotor Tip Clearance Flow in a Turbine/Exhaust Diffuser System

1987 ◽  
Author(s):  
Saeed Farokhi
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Tip Clearance ◽  
Pressure Recovery ◽  
Efficiency Gain ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Gas Turbine Power Plant

In a modern gas turbine power plant, the axial exhaust diffuser accounts for up to 10% of the generator power. An unshrouded rotor, due to its highly energetic tip clearance flow, improves the pressure recovery characteristic of the exhaust diffuser, while the power production within the blading suffers a loss as a result of the tip leakage flow. In this paper, these conflicting trends are thermodynamically investigated and nondimensional expressions are derived which facilitate the task of a gas turbine system designer. Conservatively, 1% thermal efficiency gain results from elimination of the last rotor tip clearance flow. The corresponding increase in thermal efficiency of a modern gas turbine power plant due to enhanced diffuser pressure recovery is less than one percent.

Sign in / Sign up

Export Citation Format

Share Document