bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automated Combustor Preliminary Design Using Tools of Different Fidelity
Authors: Angersbach Andreas , Bestle Dieter , Eggels Ruud 
Published: November 2013

The design of a modern aero-engine combustor is a highly complex and multi-disciplinary task. The combustor design is strongly driven by severe emission regulations and ACARE 2020/2050 goals. Furthermore, new designs have to be developed within short turn-around times. This paper describes a novel approach of an automated preliminary aero-thermal design process of a rich-burn combustor combining 1D, 2D and 3D design tools in order to speed up the design loop and provide improved combustor designs in an early design stage.
The automated design process includes a knowledge-based preliminary design tool, an 1D network solver, a parametric 3D geometry model, a meshing tool, and 3D-CFD analysis. At first, a preliminary combustor design is created based on industrial in-house design rules. The preliminary design tool provides a 2D geometry model and cooling layout. It is coupled with an 1D network solver to calculate the air distribution inside the combustor. The design process includes two state-of-the-art combustor cooling schemes, effusion cooling and impingement effusion cooling. An air flow model for both cooling schemes is created within the network, respectively. The computed air distribution is subsequently used to generate boundary conditions for a 3D-CFD analysis. To perform the CFD calculations, a parametric 3D geometry model of a combustor sector has been developed based on a 2D preliminary design which takes into account mixing port properties, fuel injector, and combustor wall cooling. After an automated meshing 3D-CFD computations are performed. As a result, quick automatic estimation of combustor emissions, size and efficiency can be obtained within the design process. A CFD parameter study of a mixing port variation and their effect on the emissions of NOx and soot is performed using the described layout process.
Investigation of the Effect of Perforated Sheath on Thermal-Flow Characteristics Over a Gas Turbine Reverse-Flow Combustor: Part 1 — Experiment
Authors: Wang Liang , Wang Ting 
Published: November 2013

Reverse-flow combustors have been used in heavy, land-based gas turbines for many decades. A sheath is typically installed over the external walls of the combustor and transition piece to provide enhanced cooling through hundreds of small jet impingement cooling, followed by a strong forced convention channel flow. However, this cooling is at the expense of large pressure loss. With the modern advancement in metallurgy and thermal-barrier coating technologies, it may become possible to remove this sheath to recover the pressure loss without causing thermal damage to the combustor chamber and the transition piece walls. However, without the sheath, the flow inside the dump diffuser may exert nonuniformly reduced cooling on the combustion chamber and transition piece walls. The objective of this paper is to investigate the difference in flow pattern, pressure drop, and heat transfer distribution in the dump diffuser and over the outer surface of the combustor with and without a sheath. Both experimental and computational studies are performed and presented in Part 1 and Part 2, respectively. The experiments are conducted under low pressure and temperature laboratory conditions to provide a database to validate the computation model, which is then used to simulate the thermal-flow field surrounding the combustor and transition piece under elevated gas turbine operating conditions.
The experimental results show that the pressure loss between the dump diffuser inlet and exit is 1.15% of the total inlet pressure for the non-sheathed case and 1.9% for the sheathed case. This gives a 0.75 percentage point (or 40%) reduction in pressure losses. When the sheath is removed in the laboratory, the maximum increase of surface temperature is about 35%, with an average increase of 13%–22% based on the temperature scale of 23 K, which is the temperature difference of bulk inlet and outlet temperature.
An Experimental Study of Mist/Air Film Cooling on a Flat Plate With Application to Gas Turbine Airfoils: Part 2 — Two-Phase Flow Measurements and Droplet Dynamics
Authors: Zhao Lei , Wang Ting 
Published: November 2013

A Phase Doppler Particle Analyzer (PDPA) system is employed to measure the two-phase mist flow behavior including flow velocity field, droplet size distribution, droplet dynamics, and turbulence characteristics.
Based on the droplet measurements made through PDPA, a projected profile describing how the air-mist coolant jet flow spreads and eventually blends into the hot main flow is proposed. This proposed profile is found to be well supported by the measurement results of the turbulent Reynolds stresses. The coolant film envelope is identified with shear layers characterized by higher magnitudes of turbulent Reynolds stresses. In addition, the separation between the mist droplet layer and the coolant air film is identified through the droplet measurements — large droplets penetrate through the air coolant film layer and travel further into the main flow.
With the proposed air-mist film profile, the heat transfer results on the wall presented in Part 1 are re-examined and more in-depth physics is revealed. It is found that the location of optimum cooling effectiveness is coincided with the point where the air-mist coolant stream starts to bend back towards the surface. Thus, the data suggests that the “bending back” film pattern is critical in keeping the mist droplets close to the surface, which improves the cooling effectiveness for mist cooling.
Influence of Nonlinear Flame Models on Sustained Thermoacoustic Oscillations in Gas Turbine Combustion Chambers
Authors: Campa Giovanni , Cinquepalmi Marina , Camporeale Sergio Mario 
Published: November 2013

In the recent years a great interest has been devoted to the understanding of the nonlinear dynamics characterizing the thermoacoustic combustion instabilities. Although linear techniques are able to predict whether the non-oscillating steady state of a thermoacoustic system is “asymptotically” stable (without oscillations) or unstable (increasing oscillations), a thermoacoustic system can reach a permanent oscillating state (the so called “limit cycle”), even when it is linearly stable, if a sufficiently large impulse occurs. A nonlinear analysis is able to predict the existence of this oscillating state and the nature of the bifurcation process.
The aim of this work is to investigate the behavior of gas turbine combustion chambers in presence of nonlinear flame models. The bifurcation diagrams, obtained by using a continuation technique in the frequency domain, give the amplitude of the oscillations as a function of a chosen flame parameter. The Helmholtz equation is used to model the combustion chamber and nonlinear terms are introduced in the flame model, starting from the classical k–τ formulation. A three-dimensional finite element method (FEM) is used for discretization of the computational domain and a solver of quadratic eigenvalue problems is combined with Newton technique in order to identify the points of the bifurcation diagram. First, a simple Rijke tube configuration, as can be found in the literature, is examined in order to obtain bifurcation diagrams. Then, the nonlinear analysis is extended to simplified annular configurations. The obtained results show how the nonlinear behavior is influenced by varying some control parameters, such as the time delay, yielding useful indications to designers and experimentalists.
Cooling Structure Optimization for a Rib-Roughed Channel in a Turbine Rotor Blade
Authors: Chi Zhongran , Ren Jing , Jiang Hongde 
Published: November 2013

Cooling design for the air-cooled turbine blades is a critical issue in modern gas turbine engineering. Advances in CFD technology is providing new prospects for turbine cooling design, as the optimum cooling structures of the blades could be designed through the optimization search coupled with the Conjugate Heat Transfer (CHT) analysis. In this paper, the optimization study for the rib arrangement of a rib-roughed channel in a rotor blade is discussed.
The optimization study introduced is realized utilizing a parametric analysis platform, which consists of the parametric design and mesh generation tool and the commercial CHT solver ANSYS CFX. For the optimization study, firstly a group of Design of Experiments (DoE) analysis of a rib-roughed rectangular channel is performed in order to find the optimum rib arrangement and to explore the objective of the optimization search. Then, the optimization search of the optimum rib arrangement is performed for a rib-roughed channel within a rotor blade based on the multi-island Genetic Algorithms (GA) of iSIGHT. During optimization search, a constant pressure drop is assumed within the cooling system, and the CHT simulations are approached for the interior only in order to make the search computationally faster.
According to the DoE analysis, minimizing the averaged wall temperature on blade surface is chosen as the optimization objective for the design of rib arrangement. The results of the GA search shows that the optimal rib arrangement with best cooling performance can be decided, and the optimal mass flow rate for the cooling channel is found simultaneously. The optimum schemes of the rib arrangement found by the DoE analysis and GA search are quite identical, which further validates the feasibility of design optimization for the blade cooling structure with the GA and CHT simulations.
Variable Asymmetric Turbine for Heavy Duty Truck Engines
Authors: Schmidt Sebastian , Rose Martin G. , Müller Markus , Sumser Siegfried , Chebli Elias , Streule Thomas , Stiller Michael , Leweux Johannes 
Published: November 2013

Turbochargers with variable turbine geometry (VGT) are established in diesel engines for passenger cars because of the beneficial effect on transient operation. The variability permits the reduction of exhaust back pressure, resulting in lower fuel consumption. There are only a few applications in heavy duty truck engines due to increased mechanical complexity and vulnerability to failure.
This paper presents a turbine concept with a simple variability developed for a heavy duty engine. The variability is achieved upstream of the rotor by changing the sectional area of the volute. This can be done through a rotationally movable ring which shifts the circumferential position of the volute tongues. These separate both scrolls of a double segment turbine and can be rotated by an electric actuator.
The performance maps measured at the hot gas test stand show the large variability of the flow parameter and the high efficiency levels over the operating range of the variable asymmetric turbine (VAT).
The flow field is computed by the use of 3D-CFD simulations in order to analyze the loss-generating mechanisms that occur within the machine.
Test runs on an engine test stand demonstrate the high potential of the concept concerning reduction of fuel consumption and a wide scope of realizable EGR rates in order to reduce NOx emissions in a cost-effective way. The resultant large mass flow variability allows the deletion of the waste gate and enables efficiency improvements.
Numerical Investigation of Flow and Heat Transfer in Gas Turbine Serpentine Passage Cooling and Comparison With Experimental Data
Authors: Kathiravan S. , De Prosperis Roberto , Ciani Alessandro 
Published: November 2013

Due to recent advancements made in computational technology, CFD tools are capable of accurately capturing complex physical phenomenon. The proposed novel CFD methodology improves the prediction reliability and capability of Gas Turbine Blade heat transfer and secondary flow behaviour.
This paper discusses a robust CFD based methodology to validate the complex gas turbine blade cooling design using detailed 3D flow & conjugate heat transfer analysis. Both primary and secondary flow domains along with blade metal are considered in one single integrated CFD model. This will capture the coupled heat transfer and tip vortices mixing effects and hence accurately predict the secondary cooling flow. The secondary flow path geometry consists of serpentine passages with turbulator features in the flow path to improve the effective heat transfer. Several sensitivity studies were performed using the above model to understand the impact of turbulator fillets, tip hole coating thickness, domain interface and suitably accounted for in the full scale simulation. The numerical simulation results were extensively validated with GE industrial Frame5 gas turbine prototype test thermocouple data and thermal profiles (span-wise) obtained from metallographic images. This novel method gives a thorough understanding of flow-thermal physics involved in serpentine cooling and helps to optimize effective cooling flow usage.
Experimental and Theoretical Investigation of Thermal Effectiveness in Multi-Perforated Plates for Combustor Liner Effusion Cooling
Authors: Andreini Antonio , Facchini Bruno , Picchi Alessio , Tarchi Lorenzo , Turrini Fabio 
Published: November 2013

State-of-the-art liner cooling technology for modern combustors is represented by effusion cooling (or full-coverage film cooling). Effusion is a very efficient cooling strategy based on the use of multi-perforated liners, where metal temperature is lowered by the combined protective effect of coolant film and heat removal through forced convection inside each hole. The aim of this experimental campaign is the evaluation of the thermal performance of multi-perforated liners with geometrical and fluid-dynamic parameters ranging among typical combustor engine values. Results were obtained as adiabatic film effectiveness following the mass transfer analogy by the use of Pressure Sensitive Paint, while local values of overall effectiveness were obtained by eight thermocouples housed in as many dead holes about 2 mm below the investigated surface. Concerning the tested geometries, different porosity levels were considered: such values were obtained both increasing the hole diameter and pattern spacing. Then the effect of hole inclination and aspect ratio pattern shape were tested to assess the impact of typical cooling system features. Seven multi perforated planar plates, reproducing the effusion arrays of real combustor liners, were tested imposing 6 blowing ratios in the range 0.5–5. Test samples were made of stainless steel (AISI304) in order to achieve Biot number similitude for overall effectiveness tests.
To extend the validity of the survey a correlative analysis was performed to point out, in an indirect way, the augmentation of hot side heat transfer coefficient due to effusion jets. Finally, to address the thermal behaviour of the different geometries in presence of gas side radiation, additional simulations were performed considering different levels of radiative heat flux.
Investigations on Nusselt Number Enhancement in Ribbed Rectangular Turbine Blade Cooling Channels of Different Aspect Ratios and Rotation Numbers
Authors: Nouri Behnam , Lehmann Knut , Kühhorn Arnold 
Published: November 2013

In the drive for higher cycle efficiencies in gas turbine engines, turbine blades are seeing an increasingly high heat load. This in turn demands improvements in the internal cooling system and a better understanding of both the level and distribution of the internal heat-transfer. A typical approach to enhance the internal cooling of the turbine blade is by casting angled ‘low blockage’ ribs on the walls of the cooling channels. The objective of the present paper is to determine the detailed Nusselt number distribution in rectangular internal channels with ribs. This knowledge can be used to guide the overall design e.g. to achieve high levels of heat-transfer where required. The effects of rotation as well as the interaction effects of the position and direction of ribs on opposite walls of the cooling channel have been investigated.
Numerical calculations have been carried out using the commercial CFD code Fluent to investigate the local Nusselt number enhancement factor in rectangular ducts of different aspect ratios (0.5, 1 and 2) which have 45° or 90° angled ribs located on two opposite walls. This has been studied for different Rotation number Ro (0–0.45) and with a Reynolds number >30000.
The first series of studies has been carried out with the same experimental setup as by Han [1]. The geometry was slightly changed to avoid the effect of high heat transfer at the entry.
This study identifies important vortical structures, which are dependent on the direction and the position of the ribs. This has a profound effect on the distribution of heat-transfer within the passage. It is shown that the two smooth walls of the duct have different average Nusselt number ratio Nu/NuFD enhancement depending on the rib angle.
In addition, based on numerical investigations, simple correlations have been developed for the rotational influence of the internal Nusselt number distribution. A major finding is that the effect of rotation is dominant for low aspect ratio channels and the local enhancement due to the rib position and angle is more dominant for high aspect ratio channels.
Noise Test of Revised Notched Nozzle Using a Jet Engine
Authors: Ishii Tatsuya , Tanaka Nozomi , Oishi Tsutomu , Ishii Yutaka 
Published: November 2013

This paper describes engine noise tests conducted in an outdoor environment using a revised notched nozzle. A notch is a small dent formed at the nozzle edge that penetrates into the primary jet. The notched nozzle is expected to improve the acoustic performance with less deterioration in aerodynamic performance relative to that of a conventional nozzle. The slight penetration of the notch causes small disturbances immediately after the nozzle, driving the subsequent mixing process in the shear layer. This mixing process helps suppress both large-scale vortices in the far downstream region and excessive shear stress near the nozzle.
The authors have researched and developed various notched nozzles. Previous engine tests using a 6-notched nozzle showed that the notch itself caused additional noise by increasing the sound pressure level at higher frequencies. To counter this problem, a revised 18-notched nozzle was developed through computational and experimental studies. The authors’ previous paper [Ishii, et al.; ASME Paper GT2012-69507, 2012] showed that this nozzle increased the noise reduction toward the side direction of the nozzle under hot-jet conditions. However, there remain some unsolved issues. One issue is the scale of the nozzle. Another issue is the test conditions, such as the different effective cross-sectional areas.
In this light, a larger-scale nozzle with a diameter five times larger than that in the hot-jet model was prepared so as to adjust the nozzle aerodynamic performance. Noise tests of this nozzle were carried out using a turbojet engine together with far-field and phased array microphones, and the revised notched nozzle was found to show improved noise reduction performance compared to the previous design.
Statistical Methods for a Stochastic Analysis of the Secondary Air System of a Jet Engine Low Pressure Turbine
Authors: Antinori Giulia , Muller Yannick , Duddeck Fabian , Fischersworring-Bunk Andreas 
Published: November 2013

In this paper several stochastic methods are evaluated with respect to their applicability for the analysis of fluid networks. The methods are applied for the analysis of a 1D flow model of the Secondary Air System (SAS) of a three stages low pressure turbine (LPT) of a jet engine.
The stochastic analysis is comprised of a sensitivity analysis followed by an uncertainty analysis. The sensitivity analysis is performed to gain a better understanding of the SAS physics and robustness, to identify the important variables and to reduce the number of parameters involved in the simulations for the uncertainty analysis. The uncertainty analysis, using probability distributions derived from the manufacturing process, allows to determine the effect of the input uncertainties on responses such as pressures, fluid temperatures and mass flow rates.
A review of the most common and relevant sampling methods is performed. A comparison of the respective computational cost and of the sample points distribution is proposed with the aim of finding the most suited method. The study shows that some of the sampling methods can not be recommended since they produce spurious correlations between independent input variables.
With regards to the sensitivity analysis, many literature sources state that the Pearson correlation method is only valid for linear models when assessing the importance of input variables. As the SAS is highly non-linear, non-parametric variance based methods are introduced here to make up for the limitations of the correlation method. Following the results of the study, it is recommended to combine the sampling method with a non-parametric variance based method. Thus, the main effects as well as all the interactions among variables are captured.
Heat-Flux Measurements for a Realistic Cooling Hole Pattern With Multiple Flow Conditions
Authors: Nickol Jeremy B. , Mathison Randall M. , Dunn Michael G. 
Published: November 2013

Predicting cooling flow migration and its impact on surface heat flux for a turbine operating at design-corrected conditions is a challenging task. While recent data sets have provided a baseline for comparison, they have also raised many questions about comparison methods and the proper implementation of boundary conditions. Simplified experiments are helpful for bridging the gap between the experimental and computational worlds to develop the best procedures for generating predictions and correctly comparing them to experiments. To this end, a flat-plate configuration has been developed that replicates the cooling hole pattern of the pressure side of a high-pressure turbine blade.
The heat transfer for this configuration is investigated for a range of flow properties of current interest to the industry using a medium-duration blowdown facility. Heat-flux measurements are obtained using double-sided Kapton heat-flux gauges arrayed in two rows in the axial direction along the centerline of the hole pattern. Gauges are located upstream of the holes, in between rows of holes, and extending far downstream of the last row of holes. New parameters are proposed for analyzing the data including a corrected Stanton number and the length-corrected heat flux reduction parameter. These parameters are used for exploring the influence of Reynolds number and blowing ratio on local heat transfer. In addition, the temperatures of the main flow and the test section walls were varied to determine the effect of cooling on the local adiabatic wall temperature and to enable comparisons using the adiabatic cooling effectiveness.