bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermo-Economic Analysis of a Recompression Supercritical CO2 Cycle Combined With a Transcritical CO2 Cycle
Authors: Wang Xurong , Wu Yi , Wang Jiangfeng , Dai Yiping , Xie Danmei
Published: August 2015

The transcritical CO2 cycle (TCO2 cycle) exhibits good performance in low-grade waste heat recovery area. In this study, a TCO2 cycle was employed as a bottoming cycle to recover the waste heat in the topping recompression supercritical CO2 Brayton cycle (SCO2 cycle). A detailed system analysis was performed of a recompression SCO2 cycle combined with a TCO2 cycle to improve the efficiency of energy conversion. Thermodynamic analysis, calculation of heat exchangers’ area and economic analysis were considered. The SCO2 turbine expansion ratio, TCO2 turbine inlet pressure, high temperature recuperator (HTR) effectiveness and condensation temperature were studied to investigate their effect on the system performance. For the basic analysis, SCO2 turbine inlet temperature was conservatively selected to be 550 °C and the compressor outlet pressure set at 20 MPa. For these operating conditions the proposed combined SCO2-TCO2 cycle yielded about 46% thermal efficiency at a SCO2 turbine expansion ratio of 2.7 and TCO2 turbine inlet pressure of 10 MPa. Similarly, the capital cost per net power output of the combined cycle was found as 6.6 k$/kW, which was ∼ 6% more expensive than that of the recompression SCO2 cycle without the bottoming cycle under the same operating condition. An optimum TCO2 turbine inlet pressure and an optimum SCO2 turbine expansion ratio existed where the system thermal efficiency reached the maximum value. Furthermore, the system thermal efficiency was very sensitive to the changes in the condensation temperature and the HTR effectiveness. The HTR effectiveness also had a strong effect on the ratio of heat exchangers’ cost to the plant capital cost. Additionally, increasing SCO2 turbine inlet temperature would significantly improve the cycle overall thermal efficiency and decrease the plant capital cost per net power output.
Effect of Mistuning and Damping on the Forced Response of a Compressor Blisk Rotor
Authors: Beirow Bernd , Kühhorn Arnold , Figaschewsky Felix , Nipkau Jens
Published: August 2015

The forced response of an E3E-type high pressure compressor blisk front rotor is analyzed with regard to intentional mistuning and its robustness towards additional random mistuning. Both a chosen alternating mistuning pattern and artificial mistuning patterns optimized concerning the forced response are considered. Focusing on three different blade modes, subset of nominal system mode-based reduced order models are employed to compute the forced response. The disk remains unchanged while the Young’s modulus of each blade is used to define the particular mistuning pattern. The well established aerodynamic influence coefficient technique is employed to model aeroelastic coupling and hence to consider the strongly mode- and inter blade phase angle-dependent aerodynamic damping contribution.

It has been found that a reduction of the maximum forced response beyond that of the tuned reference can be achieved for particular mistuning patterns and all modes considered. This implies an exciting engine order which would cause a low nodal diameter mode in case of a tuned blisk. At best a nearly 50% reduction of maximum response magnitudes is computed for the fundamental bending mode and large mistuning. The solution proved to be robust towards additional random mistuning of reasonable magnitude, which is of particular interest with regard to a potential technical realization. In case of small mistuning as assumed for the first torsion and the longitudinal bending mode the advantage of achieving response magnitudes beyond the tuned reference gets lost indeed, if random mistuning is superimposed. However, mostly a lower response level is calculated compared to responses obtained from models adjusted to mistuning determined by experiment.
Investigation of Stator Induced Unsteadiness on a Centrifugal Impeller Using a Mach-Independent Non-Linear Harmonic Method
Authors: Tartinville Benoît , Hirsch Charles
Published: August 2015

The objective of this paper is to numerically investigate the unsteadiness generated by a bladed diffuser on an upstream centrifugal impeller. The Non-Linear Harmonic (NLH for short) time-spectral method has been retained here. The major advantage of such a method is that it requires much less computational effort than a standard unsteady simulation. In order to further reduce the computing time, the NLH method has been extended to low speed flows by using a preconditioning technic. Therefore, the NLH method can be accurately applied to any Mach number flow and even to purely incompressible fluids. This extension of the flow solver has been validated on a wide range of simple test cases at various reduce frequencies. Solutions have been compared to purely unsteady approach and also to experimental data. In a second step, the NLH method has been applied to a centrifugal impeller and its downstream diffuser. Numerical results have been analyzed and compared to the available experimental data showing the significant influence of the downstream diffuser on the impeller pressure load.
Experimental and Numerical Study on Optimizing the DLN Micromix Hydrogen Combustion Principle for Industrial Gas Turbine Applications
Authors: Funke H. H.-W. , Keinz J. , Kusterer K. , Haj Ayed A. , Kazari M. , Kitajima J. , Horikawa A. , Okada K.
Published: August 2015

Combined with the use of renewable energy sources for its production, hydrogen represents a possible alternative gas turbine fuel for future low emission power generation. Due to the difference in the physical properties of hydrogen compared to other fuels such as natural gas, well-established gas turbine combustion systems cannot be directly applied to Dry Low NOx (DLN) hydrogen combustion.

The DLN Micromix combustion of hydrogen has been under development for many years, since it has the promise to significantly reduce NOx emissions. This combustion principle for air-breathing engines is based on cross-flow mixing of air and gaseous hydrogen. Air and hydrogen react in multiple miniaturized diffusion-type flames with an inherent safety against flash-back and with low NOx-emissions due to a very short residence time of the reactants in the flame region.

The paper presents an advanced DLN Micromix hydrogen application. The experimental and numerical study shows a combustor configuration with a significantly reduced number of enlarged fuel injectors with high thermal power output at constant energy density. Larger fuel injectors reduce manufacturing costs, are more robust and less sensitive to fuel contamination and blockage in industrial environments.

The experimental and numerical results confirm the successful application of high energy injectors, while the DLN Micromix characteristics of the design point, under part load conditions and under off-design operation are maintained. Atmospheric test rig data on NOx emissions, optical flame structure and combustor material temperatures are compared to numerical simulations and show good agreement.

The impact of the applied scaling and design laws on the miniaturized Micromix flamelets is particularly investigated numerically for the resulting flow field, the flame structure and NOx formation.
Experimental and Numerical Investigation of Erosive Change of Shape for High-Pressure Compressors
Authors: Schrade Marcus , Staudacher Stephan , Voigt Matthias
Published: August 2015

Compressor performance and maintenance characteristics of jet engines are highly influenced by erosion caused by ingested, solid particles. For a meaningful prediction of these characteristics, an adequate modeling of the erosive change of shape of compressor blades is necessary. This article investigates the erosive change of shape of two different specimens (cylinder and compressor blade) out of aluminum alloy EN AW-6060 both experimentally and numerically. The erosion experiments were performed with a test rig using different amounts of standardized Arizona Test Dust A3 (particle sizes of 1–120μm) to acquire the time-dependent change of shape of the specimens. The shape of the specimens was digitized using a strip projection technique before and after each erosion test. The test rig provides boundary conditions specific for first stages of axial high-pressure compressors of jet engines in terms of relative fluid velocity (350ms−1) which is the main parameter of erosion. Numerical results were obtained with a model predicting the time-dependent change of shape of the specimens in 2D. The numerical model uses erosion rate curves that were experimentally determined in the same test rig using flat plates out of the aforementioned aluminum alloy. Thus, we were able to investigate experimentally the time-dependent erosive change of shape of the specimens and compare it with the numerical predictions. We conclude that the numerical model is a valid approach to predict erosive change of shape for different specimen geometries and materials, when erosion rate curves are available for these materials.
Effects of Flow Distortions as They Occur in S-Duct Inlets on the Performance and Stability of a Jet Engine
Authors: Rademakers Rudolf. P. M. , Bindl Stefan , Niehuis Reinhard
Published: August 2015

One of the research areas at the Institute of Jet Propulsion focuses on the design and optimization of s-shaped engine inlet configurations. The distortion being evoked within such inlet ducts should be limited to ensure an optimal performance, stability, and durability of the engine’s compression system.

Computational Fluid Dynamics (CFD) play a major role in the design process of bent engine inlet ducts. The flow within such ducts can be computed, distortion patterns can be visualized, and related distortion coefficients are easily calculated. The impact of a distortion on flow phenomena within the compressor system can, however, only be computed with major computational efforts and thus the quality of an s-duct design in development is usually assessed by analyzing the evoked distortion with suitable distortion coefficients without a true knowledge of the duct’s influence on the downstream propulsion system.

The influence of inlet distortion on both the performance and stability of the Larzac 04 jet engine was parameterized during experimental investigations at the engine test bed of the Institute of Jet Propulsion. Both pressure and swirl distortion patterns as they typically occur in s-duct inlet configurations were reproduced with distortion generators. Pressure distortion patterns were generated using seven types of distortion screens. The intensity of the distortion varies with the mesh size of the screen whereas the extension of the distortion is defined by the dimensions of the screen in radial and circumferential direction. A typical counter rotating twin-swirl was generated with a deltawing installed upstream of the compressor system.

First, the development of flow distortion was analyzed for several engine operating points (EOPs). A linear relation between the total pressure loss in the engine inlet and the EOPs was found. Secondly, the flow within the compressor system with an inlet distortion was analyzed and unsteady flow phenomena were detected for severe inlet distortions. Finally, the effect of both pressure and swirl distortion on the performance and stability of the test vehicle was parameterized. A loss in engine performance with increasing inlet distortion is observable. The limiting inlet distortion with respect to engine stability was found and moreover it was shown that pressure distortion has a stronger influence on the stability of the compressor system compared to a counter rotating twin-swirl distortion. The presented parameterization is essential for the s-duct design, which is under development for an experimental set-up with the Larzac 04 jet engine.
NOx Behavior for Lean-Premixed Combustion of Alternative Gaseous Fuels
Authors: Fackler K. Boyd , Karalus Megan , Novosselov Igor , Kramlich John , Malte Philip
Published: August 2015

Gaseous fuels other than pipeline natural gas are of interest in high-intensity premixed combustors (e.g., lean-premixed gas turbine combustors) as a means of broadening the range of potential fuel resources and increasing the utilization of alternative fuel gases. An area of key interest is the change in emissions that accompanies the replacement of a fuel. The work reported here is an experimental and modeling effort aimed at determining the changes in NOx emission that accompany the use of alternative fuels. Controlling oxides of nitrogen (NOx) from combustion sources is essential in non-attainment areas. Lean-premixed combustion eliminates most of the thermal NOx emission, but is still subject to small, though significant amounts of NOx formed by the complexities of free radical chemistry in the turbulent flames of most combustion systems. Understanding these small amounts of NOx, and how their formation is altered by fuel composition, is the objective of this paper. We explore how NOx is formed in high-intensity, lean-premixed flames of alternative gaseous fuels. This is based on laboratory experiments and interpretation by chemical reactor modeling. Methane is used as the reference fuel. Combustion temperature is maintained the same for all fuels so that the effect of fuel composition on NOx can be studied without the complicating influence of changing temperature. Also, the combustion reactor residence time is maintained nearly constant. When methane containing nitrogen and carbon dioxide (e.g., landfill gas) is burned, NOx increases since the fuel/air ratio is enriched in order to maintain combustion temperature. When fuels of increasing C/H ratio are burned leading to higher levels of carbon monoxide (CO) in the flame, or when the fuel contains CO, the free radicals made as the CO oxidizes cause the NOx to increase. In these cases, the change from high-methane natural gas to alternative gaseous fuel causes the NOx to increase. However, when hydrogen is added to the methane, the NOx may increase or decrease, depending on the combustor wall heat loss. In our work, in which combustor wall heat loss is present, hydrogen addition deceases the NOx. This observation is compared to the literature. Additionally, minimum NOx emission is examined by comparing the present results to the findings of Leonard and Stegmaier.
Numerical Investigation of the Thermo-Acoustic Influence of the Turbine on the Combustor
Authors: Farisco Federica , Panek Lukasz , Janus Bertram , Kok Jim B. W.
Published: August 2015

Lean premixed combustion technology became state-of-the-art in modern gas turbines for power generation to reduce NOx emissions. In these systems, thermo-acoustic oscillations are easily excited in the combustion chamber. Due to the high heat release density, extreme amplitudes can occur which reduce component life or may even cause damage to the engine. Knowledge of the acoustic behavior is required in order to understand and predict these instabilities. This study of the combustor-turbine interaction is focused on the reflection coefficient analysis. The interface between the combustion system and the first turbine stage is the focus area of this study. The rotating components need to be included as outlook of this work. Compressible Large Eddy Simulation (LES) resolving acoustics is applied based on the open source CFD code OpenFOAM. Five cases of increasing complexity are presented. The main idea is to begin the study based on simple geometries such as a convergent-divergent nozzle and two nozzles respectively convergent and divergent, to proceed with increased complexity by adding a vane section, and finally to investigate the behavior of a realistic turbine design. The real engine case consists of an authentic geometry including a can annular combustion chamber and turbine vane section. These cases are studied as basic generic tests in order to validate analytical formulae and to test the CFD methods applied. Calculations with acoustic excitation and non reflecting boundary conditions (NRBC) at the computational inlet and outlet domains are carried out to verify the plausibility of the acoustic set up. The forced response approach is applied provoking a wave excitation at the inlet of the combustion chamber. Multi-harmonic excitation with small amplitudes is used to stay in the linear range. The post-processing for all cases is performed using the two-microphone method in order to calculate the reflection coefficient and the acoustic impedance taking into account the effects of the mean flow.
Étude on Gas Turbine Combined Cycle Power Plant: Next 20 Years
Authors: Gülen S. Can
Published: August 2015

In 1992, United States Department of Energy’s Advanced Turbine Systems program established a target of 60% efficiency for utility scale gas turbine power plants to be achieved by the year 2000. Although the program led to numerous technology breakthroughs, it took another decade for an actual combined cycle power plant with an H class gas turbine to reach (and surpass) the target efficiency.

Today, another target benchmark, 65% efficiency, circulates frequently in trade publications and engineering journals with scant support from existing technology, its development path as well as material limits, and almost no regard to theoretical (e.g., underlying physics) and practical (e.g., cost, complexity, reliability and constructability) concerns.

This paper attempts to put such claims to test and establish the room left for gas turbine combined cycle (GTCC) growth in the next two decades. The analysis and conclusions are firmly based on fundamental thermodynamic principles with carefully and precisely laid out assumptions and supported by rigorous calculations. The goal is to arm the practicing engineer with a consistent, coherent and self-standing reference to critically evaluate claims, predictions and other futuristic information pertaining to GTCC technology.
Assessment of Recoverable vs Unrecoverable Degradations of Gas Turbines Employed in Five Natural Gas Compressor Stations
Authors: Botros K. K. , Hartloper C. , Golshan H. , Rogers D.
Published: August 2015

Gas Turbines (GT), like other prime movers, experience wear and tear over time, resulting in decreases in available power and efficiency. Further decreases in power and efficiency can result from erosion and fouling caused by the airborne impurities the engine breathes in. To counteract these decreases in power and efficiency, it is standard procedure to ‘wash’ the engine from time to time. In compressor stations on gas transmission systems, engine washes are performed off-line and are scheduled in such intervals to optimize the maintenance procedure. This optimization requires accurate prediction of the performance degradation of the engine over time. A previous paper demonstrated a methodology for evaluating various components of the GT gas path, in particular the air compressor side of the engine since it is most prone to fouling and degradation. This methodology combines Gas Path Analysis (GPA) to evaluate the thermodynamic parameters over the engine cycle followed by parameter estimation based on the Bayesian Error-in-Variable Model (EVM) to filter the data of possible noise due to measurement errors. The methodology quantifies the engine-performance degradation over time, and indicates the effectiveness of each engine wash. In the present paper, the methodology was extended to assess both recoverable and un-recoverable degradations of five gas turbine engines employed on TransCanada’s pipeline system in Canada. These engines are: three GE LM2500+, one RR RB211-24G, and one GE LM1600 gas turbines. Hourly data were collected over the past four years, and engine health parameters were extracted to delineate the respective engine degradations. The impacts of engine loading, site air quality conditions and site elevation on engine-air-compressor isentropic efficiency are compared between the five engines.
Free Vibration in a Mistuned Steam Turbine Last Stage Bladed Disk
Authors: Drewczynski Marcin , Rzadkowski Romuald , Maurin Artur , Marszalek Piotr
Published: August 2015

The design of blades in the last stage of a steam turbine is one of the most demanding engineering tasks in the turbomachinery field. Increasing turbine efficiency has led to the designing of higher tip-to-hub ratios. Slender blading conforms to reliability requirements, such as high blade stiffness and a high first mode natural frequency.

Several high vibration amplitude problems were reported regarding a slender last stage blading of a commercial low-pressure steam turbine. During maintenance it was decided that the blades would be geometrically mistuned to prevent self-excitation.

This paper presents a numerical study of LP steam turbine last stage bladed disk mistuning. Two different approaches to mistuning were applied and numerically compared: geometrical and material. The mode shapes and natural frequencies of the steam turbine bladed disk were calculated on the basis of an FEM model. The smallest range of mistuning (0,5Hz) in a bladed disk contaminates nodal diameters up to the fourth series. This should be taken into account when tip-timing method is adapted for steam turbine operation monitoring.
Transient Simulation of a Gas Turbine Disk Incorporating Heat Pipes Under Structural Aspects
Authors: Eisenmann Sina , Körner Roman , Hupfer Andreas
Published: August 2015

This paper investigates the results of a transient FEM simulation of a generic and simplified turbine disk with incorporated heat pipes under thermal and rotational loads. Therefore a startup process of the high temperature heat pipe from the frozen state is modeled by local variation of temperature-dependent material properties. Transient temperature distributions along the heat pipe and inside the turbine disk are investigated. Furthermore, the time dependent von Mises stresses as well as the temperature-induced stress components are evaluated over the disk radius and at the high loaded disk bore. By using the heat pipe, the temperature at the disk rim is reduced after a short time. During the startup process there is a short term increase of the von Mises stresses up to 2% at the high loaded disk bore. Furthermore there are heat pipe induced stress concentrations which reach high transient values.
A Wall-Function Based Model for Multi-Perforated Walls
Authors: Arroyo Callejo G. , Laroche E. , Millan P. , Leglaye F.
Published: August 2015

Effusion cooling is one of the most effective techniques to prevent combustor liner from being damaged. As effusion-cooled liners are comprised of a large number of sub-millimeters closely-spaced holes, full 3D numerical simulations of the combustion chamber are still unaffordable. Thus, aero-thermal models are needed to describe the main flow-liner interaction. The aim of this paper is to provide a homogeneous wall model for gas turbine combustor liners based on wall-function similarities. In order to develop such a model, a numerical database was built up covering a wide range of interest for gas turbine applications. The model proposed here consists of two modified wall-functions for both sides of a liner and an analytical model to take into account the heat exchange within the holes. As holes are not reproduced and coarse near-wall grids are sufficient, the computational cost of this methodology is very low. The performance and limitations of the model are discussed. The model has proved satisfactory in assessing the effect of a liner on the surrounding and vice-versa. Although discrepancies were observed for the first rows, momentum and heat fluxes between the flow and the impinged wall are reproduced with a good level of agreement. Overall effectiveness is predicted with a mean relative error of less than 5%.
Numerical Analysis of Honeycomb Labyrinth Seals: Cell Geometry and Fin Tip Thickness Impact on the Discharge Coefficient
Authors: Desando Alessio , Rapisarda Andrea , Campagnoli Elena , Taurino Roberto
Published: August 2015

The design of the newest aircraft propulsion systems is focused on environmental impact reduction. Extensive research is being carried out with the purpose of improving engine efficiency, enhancing crucial features, in order to decrease both fuel consumption and pollutant emissions. A lot of improvements to fulfill these objectives must be made, focusing on the optimization of the main engine parts through the utilization of new technologies. The leakage flow reduction in the turbo machinery rotor-stator interaction is one of the main topics to which numerous efforts are being devoted.

Labyrinth seals, widely employed in the aerospace field thanks to their simple assembly process and maintenance, can be the means to achieve these objectives.

This paper mainly focuses on the optimization of the labyrinth seal stator part, characterized, in modern Low Pressure Turbines (LPT), by a honeycomb cell pattern.

The first phase of this study deals with the implementation and validation of a Computational Fluid Dynamics (CFD) numerical model, by using the experimental data available in the literature. Discharge coefficients obtained by numerical simulations, performed at different clearances and pressure ratios on both smooth and honeycomb non-rotating labyrinth seals, are presented and compared to the literature data.

Then, for both convergent and divergent flow conditions, the effects on the discharge coefficient due to variations in several cell pattern parameters (i.e. cell diameter, depth and wall thickness) and fin tip thickness are shown. For these analyses the values of clearance and pressure ratio are set at a constant value.
Flow Analysis of 1.5 Stage Compressor With Variable-Camber Inlet Guide Vanes
Authors: Zhang Guochen , Liu Bo , Zhang Peng , Mao Xiaochen
Published: August 2015

Installing the variable-camber inlet guide vanes (VIGV) on aero-engine can both adjust inlet flow of next bladerow and change the pre-spin. In this paper, flow field is numerically predicted at different curvatures of the VIGV. The rotational speed set at 63% of design rotational speed, turbulence model is Spalart - Allmaras, and central difference scheme is chosen as the discrete scheme. Nonlinear harmonic method is adopted to analyzing how the unsteady flow and wake affect next blade row at different time step when curvatures of VIGV set to be 0° and −5°. The effect of wake on relative velocity and outlet flow angle at 0.25T, 0.5T, 0.75T and 1T from 10% to 90% height were analyzed. The results show that wake of rotor affects flow above 50% height, but it has less effect on flow near the hub. The wakes of VIGV have less effect on rotor, but the wake of rotors has more effect on next bladerow. Wake affects less flow of next bladerow when VIGV is adjusted to 0°. Overall, the velocity of −5° VIGV is higher than that of 0° VIGV in rotor passage, and total pressure ratio of −5° VIGV is higher than that of 0° VIGV. The scale of 0° VIGV vortex is bigger than that of −5° VIGV in first stators when the compressor operates near the surge line. Stability range of −5° VIGV is wider than that of 0° VIGV. The performance of the −5° VIGV is better than that of 0° VIGV when operating condition is close to surge line. On the whole, by installing VIGV the performance of aero-engine can be improved, which provides guidance for compressor designers.
Numerical Investigation of a Cantilevered Compressor Stator at Varying Clearance Sizes
Authors: Yang Chengwu , Lu Xingen , Zhang Yanfeng , Zhao Shengfeng , Zhu Junqiang
Published: August 2015

The clearance size of cantilevered stators affects the performance and stability of axial compressors significantly. Numerical calculations were carried out using the commercial software FINE/Turbo for a 2.5-stage highly loaded transonic axial compressor, which is of cantilevered stator for the first stage, at varying hub clearance sizes. The aim of this work is to improve understanding of the impact mechanism of hub clearance on the performance and the flow field in high flow turning conditions. The performance of the front stage and the compressor with different hub clearance sizes of the first stator has been analyzed firstly. Results show that the efficiency decreases as clearance size varies from 0 to 3% of hub chordlength, but the operating range has been extended. For the first stage, the efficiency decreases about 0.5% and the stall margin is extended. The following analysis of detailed flow field in the first stator shows that the clearance leakage flow and elimination of hub corner separation is responsible for the increasing loss and stall margin extending respectively. The effects of hub clearance on the downstream rotor have been discussed lastly. It indicates that the loss of the rotor increases and the flow deteriorates due to increasing of clearance size and hence the leakage mass flow rate, which mainly results from the interaction of upstream leakage flow with the passage flow near pressure surface. The affected region of rotor passage flow field expands in spanwise and streamwise direction as clearance size grows. The hub clearance leakage flow moves upward in span as it flows toward downstream.
Experimental and Numerical Heat Transfer Investigation of an Impinging Jet Array on a Target Plate Roughened by Cubic Micro Pin Fins
Authors: Brakmann Robin , Chen Lingling , Weigand Bernhard , Crawford Michael
Published: August 2015

A generic impingement cooling system for turbomachinery application is modeled experimentally and numerically to investigate heat transfer and pressure loss characteristics. The experimental setup consists of an array of 9 by 9 jets impinging on a target plate with cubic micro pin fins. The cubic micro pin fins have an edge length of 0.22 D and enlarge the target area by 150%. Experimentally heat transfer is measured by the transient liquid crystal (TLC) method. The transient method used requires a heated jet impinging on a cold target plate. As reference temperature for the heat transfer coefficient we use the total jet inlet temperature which is measured via thermocouples in the jet center. The CFD model was realized within the software package ANSYS CFX. This model uses a steady state - 3D - RANS approach and the shear stress transport (SST) turbulence model. Boundary conditions are chosen to mimic the experiments as close as possible. The effects of different jet-to-plate spacing (H/D = 3–5), crossflow schemes and jet Reynolds number (15,000–35,000) are investigated experimentally and numerically. The results include local Nusselt numbers as well as area and line averaged values. Numerical simulations allow a detailed insight into the fluid mechanics of the problem and complement experimental measurements. A good overall agreement of experimental and numerical behavior for all investigated cases could be reached. Depending on the crossflow scheme the cubic micro pin fin setup increases the heat flux to about 134%–142% compared to a flat target plate. At the same time the Nusselt number slightly decreases. The micro pin fins increase the pressure loss by not more than 14%. The results show that the numerical model predicts the heat transfer characteristics of the cubic micro pin fins in a satisfactory way.
Investigation on Water Film Induced Profile Losses in a Compressor Cascade
Authors: Neupert Niklas , Joos Franz
Published: August 2015

The share of renewable sources in the energy sector is increasing steadily leading to higher requirements towards plant flexibility for conventional plants to compensate for the highly fluctuating power supply. To enhance the flexibility of gas turbine power plants overspray fogging systems can be used. Opposed to this positive effect it was shown that a two-phase flow increases losses and minor turning of the blade row as shown by Ober [1]. The reason for this change in aerodynamic performance, however, is not yet fully understood. As shown by Wurz [2] the velocity profile of the airflow changes in the presence of a water film which is related to an increased roughness due to the waviness of the water film. However, the experimental data base for the effect of a water film on compressor airfoils and its effect on aerodynamics is small and the possibility to capture all relevant effects in numerical codes requires an enormous effort.

Therefore the objective of this study is to show the feasibility of modeling the influence of a water film as a region of increased surface roughness to estimate the aerodynamic effects on the compressor flow more easily. In the first part of the study the focus is directed to the water wall film pattern inspected experimentally at the transonic open loop wind tunnel at Helmut-Schmidt-University in Hamburg for two different airfoils. This study reveals the areas which are covered with a continuous water film. In the second part results of CFD calculations are presented. A reverse approach is used. Instead of simulating the water film in all details the focus is put on modeling the influence of a water film present. The regions previously being detected to be covered by water are defined as rough walls. The roughness height is varied to match experimentally measured losses published by Ober [1]. The results show the magnitude of influence of a wetted surface on the blade profile loss.
A Numerical Study on Characteristics of Swirl Premixed Flame Interaction Affecting NO Emission in a Gas Turbine Combustor
Authors: Park Junho , Cho Cheon Hyeon , Sohn Chae Hoon
Published: August 2015

Flame interaction between two neighboring burners in a gas turbine combustor is investigated numerically for pursuit of its effect on NOx emission from the burners. In a model chamber or liner, EV burners with double cone are installed. Two burners with the opposite rotating directions (L-R type burner) of air stream are adopted and the distance between them is variable from 74.2 mm to 222.6 mm by the step size of 37.1 mm and an additional distance of 171.3 mm is considered. Gaseous methane and air are adopted as fuel and oxidizer, respectively. From steady-state numerical analyses, flow, temperature, and NO concentration fields are calculated in all computational cases to find their correlation with NO formation. NO emission is evaluated at the exit of the model chamber with two burners as a function of burner distance. Swirl flows induced by EV burner are kept up to the liner exit, but with weaker swirl than that of the same rotating burners (L-L type burners). The case of shortest distance presents strong correlation between two flames while the other cases present weak correlation. In all cases of L-R type burners, NO emission is lower than that of L-L type burners, which results from change in swirl flow patterns. NO emission from L-R type burners with intermediate distances is greater than that from a single burner, but it is smaller than the latter with relatively shorter and longer burner distances.
Adaptive Surrogate-Based Multi-Disciplinary Optimization for Vane Clusters
Authors: Arsenyev Ilya , Duddeck Fabian , Fischersworring-Bunk Andreas
Published: August 2015

The presented work is part of a research project aimed towards multi-disciplinary robust shape optimization of low pressure turbine (LPT) vane clusters. Multi-disciplinary analysis for vane cluster optimization is used to evaluate design constraints, involving 3D aerodynamic Navier-Stokes simulation, transient thermal analysis, structural analysis and life prediction. The expense of these simulations combined with high-dimensional design space, makes the application of gradient-based or stochastic optimizers inefficient. To overcome these issues, a surrogate-based optimization approach is proposed here. High quality surrogate models are required for accurate description of the constraints with life prediction. Adaptive Global Surrogate-Based Optimizer, based on Gaussian-Process (GP) surrogate models and Expected Improvement infill criteria is employed, which allows to efficiently increase the surrogate quality while approaching the optimal solution at the same time. Additional techniques are introduced to deal with the geometry rebuild failure, as some combinations of the design parameters may produce infeasible geometry. The adaptive optimization method is successfully applied to the multi-disciplinary problem for the vane cluster shape optimization. The comparison of the method performance with a gradient-based optimizer indicates that a much lower number of true simulations is needed by the proposed method to find an optimal design. Successful optimization results shows the ability of the method to handle simulation crashes, caused by geometry rebuild failure.
Aerodynamic Investigations of an Advanced VIGV Design of Adjustable Geometry for Very High Flow Turning
Authors: Händel David , Niehuis Reinhard , Klausmann Jan
Published: August 2015

On the basis of experimental results the new design of a Variable Inlet Guide Vane (VIGV), as can be used for the control and regulation in multishaft compressors, is presented. Main goal of this investigation is a significant increase of the operating range and a reduction of the total pressure loss compared to a currently used basic design. For both designs 2D-cascades were build for detailed measurements in the High-Speed Cascade Wind Tunnel at the Institute of Jet Propulsion at the Universität der Bundeswehr München. The basic design exhibits a symmetric profile with only one segment. In contrast to that the new VIGV design consists of two symmetric vane segments which are arranged pivotable to each other. This provides the advantage of a symmetric profile for a fully opened VIGV associated with a low-loss level. For guidance of the flow, both vane segments can be rotated. Hence, the turning of the flow is split onto two segments. This avoids a huge flow separation on the suction side for high turning angles (Δβ > 30°) which is linked with a strong and abrupt loss increase. Due to the design, the new VIGV exhibits a gap between the two vane segments. Results with opened and sealed gap are presented and discussed. Using a sealing between the segments, a reduction of the profile loss could be detected for all investigated operating conditions. Even without a sealing in the gap, the “low-loss working range” is significantly increased. In addition, it is depicted that the presented results are valid for varying inflow velocities. This broadens the usability of the outcomes. Concluding, it is shown that all aims are achieved. Using the new VIGV design with sealing the low-loss working range can almost be doubled (Δβ > 55°) and the total pressure loss decreases in every working condition compared to the basic design.
The Effect of Confinement on the Structure and Dynamic Response of Lean-Premixed, Swirl-Stabilized Flames
Authors: De Rosa Alexander J. , Peluso Stephen J. , Quay Bryan D. , Santavicca Domenic A.
Published: August 2015

The effect of flame-wall interaction on the forced response of a lean-premixed, swirl-stabilized flame is experimentally investigated by examining flames in a series of three combustors, each with a different diameter and therefore a different degree of lateral confinement. The confinement ratios tested are 0.5, 0.37 and 0.29 when calculated using the diameter of the nozzle relative to the combustor diameter. Using both flame images and measured flame transfer functions, the effect of confinement is investigated and generalized across a broad range of operating conditions. The major effect of confinement is shown to be a change in flame structure in both the forced and unforced cases. This effect is captured using the parameter Lf,CoHR/Dcomb, which describes the changing degree of flame-wall interaction in each combustor size. The measured flame transfer function data, as a function of confinement, is then generalized by Strouhal number. Data from the two larger combustors is collapsed by multiplying the Strouhal number by the confinement ratio to account for the flow expansion ratio and change in convective velocity within the combustor. Trends at the transfer function extrema are also assessed by examining them in the context of confinement and by using flame images. A change in the fluctuating structure of the flame is also seen to result from an increase in confinement.
Thermoeconomic Analysis of CSP Air-Steam Mixed Cycles
Authors: Barberis Stefano , Traverso Alberto
Published: August 2015

This paper investigates the integration of Concentrating Solar Power technology in air-steam Mixed Cycles for power production. Starting from a state of the art of CSP plants and the undergoing research in hybridization of Gas Turbine plants, the paper investigates alternative plant configurations particularly regarding the integration of CSP technology with mixed cycles, assessed and compared with a through-life thermo-economic analysis.

Solar heat collected by on the market CSP mirrors at moderate temperatures (300°C–500°C) can be employed to increase conventional steam-injection gas turbine power plants performances. Solar concentrating collectors for current steam solar power plants can be used for such an application can be simpler and less expensive than collectors supposed to be used for hybrid GT CSP Plants which need high temperature systems (collectors and receivers).

The solar hybridization of mixed cycles could be a good opportunity to combine gas turbine technology and CSP systems thus augmenting efficiency and achieving power dispatchability, but avoiding dedicated combustion chambers for hybrid CSP purposes (one of the big technologic problems to combine CSP and Gas Turbine technology). Moreover, the availability of commercial steam injected gas turbines at intermediate power range (10–100MW) allows the realization of such hybrid mixed CSP power plants in their typical size, avoiding the need for very large solar fields and reducing the technological risk as well as the time to market.

Focus is on the design of the plant that was made analyzing different factor like solar share factor, water consumption and reintegration and LCOE. A comparison of this innovative hybrid CSP-STIG plant with traditional STIG, Integrated Solar Combined Cycles (ISCC) and a traditional Combined Cycle was made. The mixed cycles CSP plants are analyzed using the original software WTEMP for the design point analysis, whose library was updated with dedicated modules.

The analysis shows that combining CSP technology with existing mixed cycles lets cost-competitive plant configurations with a relatively short time to market.
Development of a Duct Silencer for Heavy Industrial Compressor Systems
Authors: Büssow Richard
Published: August 2015

Typical silencer in heavy industrial compressor systems consist of pressure vessels with baffles filled with mineral wool or similar material. With the presented silencer the sound damping is achieved with an acoustic liner covered with a multi-layer steel wire mesh. This special material makes it possible to build optimized silencers with very good damping characteristic. The transmission loss is optimized according to the emission spectra of the compressor. The blocking of the free passage is reduced so that an inline configuration without an additional pressure vessel can be achieved. Tests were performed with an external sound source and with a 10 MW compressor as sound source. This paper summarizes the design of the silencer and a possibility for sound measurements with flow during a shop test.
Progress in Open Rotor Research: A U.S. Perspective
Authors: Van Zante Dale E.
Published: August 2015

In response to the 1970s oil crisis, NASA created the Advanced Turboprop Project (ATP) to mature technologies for high-speed propellers to enable large reductions in fuel burn relative to turbofan engines of that era. Both single rotation and contra-rotation concepts were designed and tested in ground based facilities as well as flight. Some novel concepts/configurations were proposed as part of the effort. The high-speed propeller concepts did provide fuel burn savings, albeit with some acoustics and structural challenges to overcome. When fuel prices fell, the business case for radical new engine configurations collapsed and the research emphasis returned to high bypass ducted configurations.

With rising oil prices and increased environmental concerns there is renewed interest in high-speed propeller based engine architectures. Contemporary analysis tools for aerodynamics and aeroacoustics have enabled a new era of blade designs that have both high efficiency and lower noise characteristics. A recent series of tests in the U.S. have characterized the aerodynamic performance and noise from these modern contra-rotating propeller designs. Additionally the installation and noise shielding aspects for conventional airframes and blended wing bodies have been studied. Historical estimates of ‘propfan’ performance have relied on legacy propeller performance and acoustics data. Current system studies make use of the modern propeller data and higher fidelity installation effects data to estimate the performance of a contemporary aircraft system. Contemporary designs have demonstrated high net efficiency, ∼86%, at 0.78 Mach, and low noise, >15 EPNdB cumulative margin to Chapter 4 when analyzed on a NASA derived aircraft/mission. This paper presents the current state of high-speed propeller/open rotor research within the U.S. from an overall viewpoint of the various efforts ongoing. The remaining technical challenges to a production engine include propulsion airframe integration, acoustic sensitivity to aircraft weight and certification issues.
Experimental Test Rig for Combustor-Turbine Interaction Research and Test Results Analysis
Authors: Yin Hong , Liu Shi , Feng Yongxin , Li Mingfei , Ren Jing , Jiang Hongde
Published: August 2015

Lean premixed combustion technology has been adopted widely for heavy duty gas turbine application. At the combustor inlet section, the basic burner arrangement is multiple-swirl configuration. The multiple-swirl structure creates complicated swirling flow field downstream, which is characterized as non-uniform flow-field and has impacts on the turbine vane. The issue of combustor-turbine interaction effect has become quite prominent.

This paper introduces a new test rig for the combustor-turbine interaction research, which is designed to investigate the influence of multiple-swirl on the turbine vane system. The test rig consists of a combustor simulator and a first stage turbine vane with cooling system. Measurement techniques including the Pressure Sensitive Paint and five-hole probe are applied.

Preliminary test results show that the multiple-swirl combustor flow field has significant impact on the vane cooling system due to the residual swirl intensity at the combustor outlet. The stagnation line at the vane leading edge is obviously altered compared to uniform inflow. Film cooling effectiveness distribution has distinct characteristics under different conditions. The leading edge is most significantly influenced, while the pressure side film cooling system is affected slightly. Under certain condition, the suction side film cooling is influenced locally.