bluuebunny/crossref_metadata_2025 huggingface dataset:
SCREENING OF GENES RESPONSIBLE FOR β-GLUCAN SYNTHESIS IN GRAIN VARIETIES
Authors: Ismagulova G.A. , Baizhumanova S.S. , Iskakova G.A. , Baisaparova D.O. , Mendesh A.M. , Tussipova A.A. , Skiba Yu.A. , Maltseva E.R. , Naizabayeva D.A. , Esimbekova M.A. , Mukin K.B.
Published: October 2022

Currently, β-glucan has a great importance for human life. Because it reduces the risks of many chronic diseases such as diabetes, cancer and digestive disorders. Due to these properties, β-glucan is a natural substance that can be used in pharmaceutical preparations for the prevention and treatment of many chronic diseases. Therefore, an analysis was made for crops rich in sources of β-glucans - 100 varieties of wheat, 50 varieties of barley and 50 varieties of oats, and a collection of genomic DNA was made. Each variety was screened to identify the genes responsible for the synthesis of β-glucans. In the frames of this study, 10 genes were considered.  As a result, these genes have been identified in barley, wheat, and oat varieties.
 For the isolation of β-glucan, the methods of acid extraction, microwave, and heating at high temperature were used. A modified method for isolating β-glucan from oatmeal was developed. According to the results, the acid extraction method proved to be more effective. It is easy to obtain pure β-glucan by this method, and the use of citric acid is safer and more affordable than conventional acids. The improved acid extraction method showed that the concentration of pure β-glucan per 10 g of wheat grain was 66.6%, and the total yield of β-glucan extract increased to 11.3%.
ISOLATION AND SCREENING OF ACTIVE CULTURES OF LACTIC ACID BACTERIA FOR INCLUSION IN THE COMPOSITION OF THE STARTER IN THE PREPARATION OF CHEESE FROM WHEY
Authors: Tynybayeva I.K. , Zhakupova G.N. , Tultabayeva T.Ch. , Nurtayeva A.B. , Sagandyk A.T. , Bekbay S.K. , Sarmurzina Z.S.
Published: October 2022

The starter cultures used to develop fermented milk products play a critical role in ensuring the quality of the final product in terms of organoleptic properties, nutritional value, and storage. The quality of the product depends on the strain and is due to differences between strains in the presence and activity of metabolic pathways. The selection of competitive bacterial cultures and the development of bacterial starters are fundamental to establishing and maintaining industrial microorganism collections. The process of creating bacterial starters takes a lot of time and includes the main stages of work: the isolation of microbes from various sources, their development, the selection of promising strains with industrially active properties, and the subsequent isolation of pure cultures as part of a consortium of bacterial starters. Potential probiotics were isolated from samples of fermented milk products - cottage cheese, butter, etc. home-made in the Akmola region, then identified and characterized. In this study, new probiotic bacteria were selected with high antibacterial activity against pathogenic microorganisms for humans and sensitivity to antibiotics. 4 strains of the studied isolates showed resistance to antibiotics and test strains. As a result of identification by MALDI-TOF MS-biotyping, it was found that the isolates isolated from domestic fermented milk products belong to the species Leuconostoc mesenteroides, Enterococcus faecium 2 pcs, Lactobacillus paracasei.
Enhancement of Low Operating Load Limit and Engine Characteristics by Hydrogen Addition in a Biogas-Fueled Spark-Ignition Engine
Authors: Bundele Hiresh , Varma Penmatsa Sandeep , Kurien Caneon , Mittal Mayank
Published: October 2022

Biogas is a renewable gaseous fuel and has the potential to replace fossil fuels for spark-ignition engines; however, a higher volumetric proportion of CO2 in biogas degrades the engine characteristics significantly. Biogas upgradation techniques are limited by higher fuel costs, and strenuous modifications would be required for improving engine physical parameters. In this study, experimental investigations were performed with hydrogen-enriched biogas to enhance low operating load limit and engine characteristics, and to the best of authors' knowledge, studies related to operating range and low load enhancement by hydrogen addition in biogas fueled engines are not reported in literature. Gaseous-fuels blending setup was developed to fabricate the gaseous fuel mixtures in desired proportions and moderate amounts of hydrogen (5, 10, 20, and 30% by vol.) were blended with biogas. The experiments were conducted on a single-cylinder SI engine operated at the compression ratio of 10:1 and 1500 rpm for stationary applications. It was found that the coefficient of variation (COV) of indicated mean effective pressure decreased from 10% in case of biogas to 8.69, 6, 3.05, and 1.66%, respectively, for 5, 10, 20, and 30% hydrogen cases at 6 N·m loading condition. Low operating load limit enhanced from 6 N·m in case of biogas to 5.3, 2.2, 1.5, and 0.8 N·m, respectively, for 5, 10, 20, and 30% of hydrogen share in the fuel mixture and brake thermal efficiency also improved with hydrogen enrichment. Carbon-based emissions decreased with hydrogen addition, whereas oxides of nitrogen increased but it was well below the baseline case with pure methane. Overall results indicated that hydrogen enrichment enhances the low load limit and engine characteristics of biogas-fueled SI engines for stationary power generation applications in rural areas.
Atomic-to-Continuum Multiscale Modeling of Defects in Crystals With Nonlocal Electrostatic Interactions
Authors: Jha Prashant K. , Marshall Jason , Knap Jaroslaw , Dayal Kaushik
Published: October 2022

This work develops a multiscale modeling framework for defects in crystals with general geometries and boundary conditions in which ionic interactions are important, with potential application to ionic solids and electric field interactions with materials. The overall strategy is posed in the framework of the quasicontinuum multiscale method; specifically, the use of a finite element inspired kinematic description enables a significant reduction in the large number of degrees-of-freedom to describe the atomic positions. The key advance of this work is a method for the efficient and accurate treatment of nonlocal electrostatic charge–charge interactions without restrictions on the geometry or boundary conditions. Electrostatic interactions are long range with slow decay and hence require consideration of all pairs of charges making a brute-force approach computationally prohibitive. The method proposed here accounts for the exact charge–charge interactions in the near-field and uses a coarse-grained approximation in the far-field. The coarse-grained approximation and the associated errors are rigorously derived based on the limit of a finite body with a small periodic lengthscale, thereby enabling the errors in the approximation to be controlled to a desired tolerance. The method is applied to a simple model of gallium nitride, and it is shown that electrostatic interactions can be approximated with a desired level of accuracy using the proposed methodology.
Dynamic Characteristics and Experimental Research of Dual-Piston Axial Oscillation Drag Reduction Tool
Authors: Tian Jialin , Tang Lei , Yan Baoyong , Song Haolin , Mao Lanhui
Published: October 2022

Aiming at the problem of low drilling efficiency of oil and gas wells due to the high friction during the drilling, a dual-piston axial oscillation drag reduction tool (DAOT) is proposed to reduce friction for long drill string in this paper. Using the proportional experiment methods based on the ground experiment conditions, pressure drop, axial displacement, and acceleration of DAOT were tested with different input parameters. The pressure drop calculation model was established by fluid mechanisms applied, and the axial excitation displacement model to the damped elastic rod subjected to axial external excitation was deduced. Furthermore, combining with the same parameters as the experiment and field application, the dynamic characteristics are studied by numerical calculation methods to identify proposed models. The results show that the correctness of the models is verified, the working pressure drop, axial displacement, working frequency, and axial oscillating force are all dependent on the input flow, the working frequency is positively correlated with the input flow, and the more the input flowrate, the great is its influence on the oscillating force. The application of DAOT can reduce extremely the friction force of drill string and improve availably the drilling efficiency. These conclusions can be of benefit for optimizing multi-piston axial oscillating tool and DAOT field applications.
Analyzing the Multiscale Impacts of Implementing Energy-Efficient HVAC Improvements Through Energy Audits and Economic Input–Output Analysis
Authors: Shook Phillip , Choi Jun-Ki , Kissock Kelly
Published: October 2022

Heating, ventilation, and air-conditioning (HVAC) systems are usually an industry’s highest consumer of energy, most of which goes toward space cooling in buildings. Industrial energy-efficiency audits not only benefit manufacturers but also generate significant economic and environmental benefits to localities, states, and the nation. This article analyzes the micro- and macro scale impacts of implementing energy-efficient HVAC systems by integrating the industrial building energy data with the macroeconomic regional economic flow model. Micro-scale data include 10 years of historical energy, cost, and carbon dioxide savings achieved from energy-efficient HVAC implementation offered to manufacturers through industrial energy audits. The data were integrated into the macroeconomic modeling framework to illuminate the cascading regional economic impacts of implementing energy-efficient HVAC recommendations in manufacturing facilities. Results show that if recommendations had been implemented throughout all manufacturers in the region, $656 M energy costs would have been directly saved, 7.8 million metric tons of carbon dioxide emissions would have been avoided, and 4387 jobs could have been created, resulting in a total annual economic impact of $899 M stemming from direct, indirect, and induced impacts. The results offer insight into how industrial energy systems can be designed and provide models for how communities can accomplish a net-zero society.
Verification of a Free-Surface Pressure Term Extension to Represent Ships in a Nonhydrostatic Shallow-Water-Equations Solver
Authors: Dempwolff León-Carlos , Windt Christian , Goseberg Nils , Martin Tobias , Bihs Hans , Melling Gregor
Published: October 2022

In recent years, increasing ship sizes and associated increasing wave loads have led to a demand for prediction tools quantifying the ship-induced loads on waterways. Depth-averaged numerical models, using a free-surface pressure term, are a prominent method to obtain the relevant design parameters. These models incorporate the wave deformation processes due to attributes of complex bathymetries, while allowing for an efficient simulation of large computational domains. The nonhydrostatic shallow-water-equations (SWE) model REEF3D::SFLOW uses a quadratic pressure approximation and high-order discretization schemes. This paper presents the implementation of a pressure term to account for the displacement of the free surface by solid moving objects. Two test cases verifying the implementation are shown based upon the analytical one-dimensional solution of the wave propagation due to surface pressure and the estimation of Havelock angles. These verification tests are the first step toward a holistic model, combining a large scale model with computational fluid dynamics (CFD) simulations near waterway banks.
Additive Manufacturing Versus Investment Casting for a Gas Turbine Component: a Social Life Cycle Comparison
Authors: Serra Angela , Gandini Sergio , Colantoni Simone , Buia Giulio , Fantaccione Luca , Bartocci Pietro , Fantozzi Francesco
Published: October 2022

Currently the Energy Industry and Industrial Power Plants are committed to support sustainable development balancing environmental, economic, and social benefits. As the first two aspects are fully covered by environmental lifecycle assessment and life cycle costing, the third one is covered only for the portion regarding human health while other aspects, like local employment, contribution to economic development, supplier’s relationship, are not so easy to be measured. Social life cycle assessment (S-LCA) is considered a powerful tool to measure and improve a company’s sustainability. Yet there is not a unique way of measuring how a company or even a product is impacting on the well-being of the society. In general, S-LCA is seen as an opportunity to improve a company’s reputation, it can help handling social aspects in the lifecycle of a product or service. S-LCA methodology is evolving since 1996 when first attempt to evaluate the social impact of a product rose and many methodologies and databases are now available; at present the phase of S-LCA development is the research of standardization. A use case of S-LCA application to a gas turbine component will be presented comparing the impact of moving the production of one component from Investment Casting to Additive Manufacturing plus insourcing coating execution: proving the benefit of applying S-LCA to products.

The findings allow comparing design and manufacturing alternatives to maximize sustainability of a product manufacturing.
Comparison of Time-Accurate and Steady-State Predictions of Heat Transfer and Pressure for a Rotating Cooled Turbine
Authors: Sperling Spencer , Christensen Louis , Mathison Randall , Aksoy Hakan , Liu Jong , Nickol Jeremy
Published: October 2022

Axial gas turbines set up highly complex unsteady flow fields, and the incorporation of cooling further complicates the flow. Due to time and computational resource constraints, the design cycle for modern gas turbines relies heavily on steady-state computational fluid dynamics simulations, which approximate time-averaged unsteady turbine flows as steady. Steady modeling provides good predictions of pressure loading but struggles with heat transfer predictions for cooled turbines. The present study incorporates experimental and computational research on a modern gas turbine stage to provide a detailed assessment of steady gas turbine modeling techniques.

Comparisons are performed among steady simulation and unsteady simulation results and time-averaged experimental data to examine the quality of computational predictions. While steady results provide good agreement with experimental pressure data, heat transfer results are less satisfactory. The largest areas of discrepancy between experiment and steady simulation are on the suction surface near the leading edge and on the pressure surface near film cooling hole rows. Unsteady simulations narrow disagreements to within unsteadiness limits. Analysis of the main gas path identifies elements of main flow unsteadiness causing augmentation in time-averaged heat transfer.

Results of this research provide a unique perspective on modeling techniques for gas turbines. The results indicate steady approximations of time-averaged heat transfer are of limited use for much of the turbine blade due to a large amount of unsteadiness in the main gas path. However, a characterization of the unsteadiness in the turbine in both experimental and computational results can help engineers to better represent the time-averaged performance with steady simulations.
Effect of Bristle Diameter on Operational Modal Assessment and Seating Load of Brush Seals
Authors: Duran Ertuğrul Tolga
Published: October 2022

Brush seal technology is frequently preferred leakage performance system in turbomachinery due to its superior clearance control capability arising from flexible structure of bristles that can compensate rotor transients. Operational modal characteristics of a brush seal is critical for the durability and stability of bristles since they operate under dynamic loadings of pressure fluctuations, flow swirls and bucket tip induced excitations. Pressurized seal modes within the frequency range of turbine operational loadings should be avoided to eliminate the stability related bristle losses and failures. Turbine condition pressure load should also be sufficiently high enough to seat the brush seal with proper contact of bristles to minimize the effect of dynamic loadings. This paper presents details of non-linear finite element analyses of brush seals for the operational modal assessment. Simulations at turbine conditions are conducted by including all interactions and critical seal modes are determined for assessing the risks for stability and durability. Seating load of the design of interest is also identified with the aid of brush seal simulations at turbine conditions. Effect of bristle diameter on the operational modes and seating load of brush seal is analyzed by running set of non-linear finite element simulations for the pressurized seal.
Amplitude and Wavelength Effects for Wavy Channels
Authors: Corbett Thomas M. , Thole Karen A. , Bollapragada Sudhakar
Published: October 2022

To improve the efficiency and durability of gas turbine components, advancements are needed in cooling technologies. To accomplish this task, some manufacturers are turning to additive manufacturing (AM), as it offers the ability to both rapidly iterate on component design, as well as incorporate unique internal cooling structures directly into parts. As one example, wavy microchannels can be readily integrated into turbine components. This study investigates wavy channels of varying channel amplitude and wavelength through experimental measurements of heat transfer and pressure loss. In addition to experimental testing, CFD predictions were made to identify internal flow features that impacted performance.

Five channel geometries were integrated into test coupons that were additively manufactured out of Hastelloy-X using direct metal laser sintering. True coupon geometric characteristics and wall roughness values were captured non-destructively using computed tomography (CT) scans. Geometric analyses indicated that coupons were reproduced accurately with minimal deviation from design intent. Experimental results indicated that decreasing the channel wavelength and increasing the channel amplitude resulted in substantial increases in both bulk friction factor and Nusselt number with respect to the nominal case and were scaled using a relative waviness parameter. CFD simulations predicted significant mixing of flow in the cases with the smallest wavelength and greatest amplitude.
Effect of Compressor Unsteady Wakes on a Gas Turbine Combustor Flow
Authors: Soli Alessandro , Adoua Richard , Langella Ivan , Denman Paul , Garmory Andrew , Page Gary J.
Published: October 2022

In gas turbines, combustor inlets are characterised by significant levels of unsteady circumferential distortion due to compressor wakes and secondary flows, together with additional radial non-uniformity induced by the adverse pressure gradients in the pre-diffuser. This can cause non-uniform velocity distributions across the fuel injector, although the exact interaction mechanism, and the effects it has on the downstream air-fuel mixing, is not fully understood. This paper investigates the flow in an a single sector of a fully featured isothermal rig comprising of compression and combustion systems, exploiting the synchronous coupling of a compressible unsteady RANS simulation with a low-Mach LES. Validation against five-hole probe measurements shows that the coupled approach can correctly predict distortion onset and development, with no solution discontinuity at the coupling interface, and is able to preserve unsteady information. The coupled prediction is then compared against a standalone combustor simulation carried out using a circumferentially uniform inlet profile, showing that the additional turbulence from the wakes interacts with the injector, reducing the coherence of the precessing vortex core and potentially affecting the air-fuel mixing characteristics.
Influence of Different Flow Solvers and Off-Design Conditions on the Determination of Fan-Rotor Wakes for Broadband Noise Prediction
Authors: Meier zu Ummeln Robert , Moreau Antoine , Schnoes Markus
Published: October 2022

The acoustic interaction of fan-rotor wakes with the downstream stator vanes is considered as an important noise source of an aircraft engine. The turbulence induced by the rotor generates a stochastic acoustic source that appears as broadband noise in the acoustic spectrum. During the preliminary design phase of an engine, established meanline and throughflow solvers usually do not resolve turbulence and associated unsteady flow parameters. But such solvers provide rotor pressure losses that can be used to estimate the mean and turbulent rotor wakes. A crucial step is the deduction of turbulence parameters from the mean wakes. A semi-empirical model for rotor-wake turbulence estimation is presented in this paper. The meanline method and the throughflow solver are compared to three-dimensional computational flow simulations investigating the capabilities of the different solvers to provide flow data for broadband wake interaction noise prediction. The methods are applied to a representative modern fan stage at a comprehensive number of operating points, comprising several speed lines from surge to choking conditions. Microphone measurements are consulted to assess the noise predictions. The evaluation confirms the applicability of the meanline and throughflow method in combination with the turbulence model for broadband noise estimation during the preliminary design phase. The underestimated turbulence in the tip region of the fan is found to be negligible even during off-design conditions.
Numerical Analysis of Blade Platform Leakage in Axial Compressors
Authors: Petermann Jannik , Pommerening Marvin , Gümmer Volker , Becker Bernd
Published: October 2022

This paper deals with the complex interacting flow between the main flow in the gas path of compressors and the hub gap leakage in the rotor blade row when considering the real geometry of the platform. The results of the present investigation agreed well with previous findings while complementing the overall compressor model. Significant local differences of the flow field between simplified endwalls and a real geometry case were detected when both circumferential and streamwise platform gaps were taken into account. At design conditions, rotor hub leakage caused by inter-platform gaps of 2.6% passage pitch reduced polytropic rotor efficiency and total pressure ratio by as much as 3.2% and 2.3%, respectively, relative to the smooth endwall setup. Front circumferential leakage was found to intensify with the presence of inter-platform leakage. The latter contributed to the formation of a large recirculation region and increased secondary flow close to the blade’s trailing edge on its suction side. A steep deterioration of the row performance from zero to non-zero midpassage massflow was observed, implying that emphasis should be placed on the avoidance of any inter-platform leakage. Flow vectors, surface streamlines, and schematic leakage paths illustrate the aerodynamic conditions under the influence of endwall leakage.
Optimized Film Cooling Flow on a Contoured Endwall Within a Transonic Annular Cascade
Authors: Burdett Timothy A. , Ullah Izhar , Wright Lesley M. , Han Je-Chin , McClintic John W. , Crites Daniel C. , Riahi Ardeshir
Published: October 2022

Film cooling was measured on the endwall of a five-vane annular cascade in a blowdown wind tunnel at an exit Mach number of 0.9. The adiabatic film cooling effectiveness was calculated from the partial pressure of oxygen measured with binary pressure sensitive paint (BPSP). Cylindrical film cooling holes were located in the upstream and passage regions with the coolant-to-mainstream mass flow ratio (MFR) independently varied for each region. One row was located upstream of the vanes and supplied by an upstream plenum. Two rows were located in the passage between two vanes and supplied by a downstream plenum. Three total MFRs were investigated: 1%, 1.5%, and 2%. For a given total MFR, four combinations of upstream and downstream MFRs were compared to an even split of coolant. Coolant-to-mainstream density ratios (DRs) of 1.0 and 2.0 were investigated. The most efficient use of coolant hinged on balancing the downstream MFR for the second row due to the endwall pressure gradient preventing coolant from exiting the holes or a high jet velocity causing liftoff. For this row, selecting the optimum MFR increased the area-averaged film cooling effectiveness by up to 200% with a reduction in row 1 of less than 25%. At high downstream MFRs, increasing the density ratio delayed liftoff and increased film cooling effectiveness in row 2 by 65%. However, at low MFRs, increasing the density ratio reduced film cooling effectiveness in row 2 by 60%.
Microstructural Evolution of Wrought and AM Haynes 188 Under Long Term Thermal Exposure
Authors: Gowreesan Vamadevan , Greaves Wayne , Pardhi Yogi , Barrios Karen
Published: October 2022

Haynes 188 is a cobalt-based superalloy used in hot section gas turbine components due to its excellent oxidation resistance and elevated temperature stability. Parts made from Haynes 188 are traditionally manufactured from wrought or forged material. Additive manufacturing (AM) may be a less time consuming and more cost-effective alternative, particularly for replacement parts. Additionally, necessary design changes can be quickly introduced into service using additive manufacturing. It is important to understand the effect of long-term thermal exposure on additively manufactured parts before they are put into demanding high temperature applications. Data on the effect of long-term thermal exposure on wrought Haynes 188 is readily available in the open literature. However, such data for additively manufactured Haynes 188 is scarce.

This paper discusses an experimental study that investigated the microstructural evolution in wrought and AM Haynes 188 under long-term thermal exposure. Optical metallography and scanning electron microscopy (SEM) were performed on wrought and AM Haynes 188 in the virgin and long-term thermally exposed conditions. Mechanical test samples from the coupons were then extracted and tested in both conditions. Lastly, the fracture surfaces of the mechanical test specimens were evaluated by SEM fractography and metallography of sections through the fracture surfaces. The findings help to understand how long-term thermal exposure affects the microstructure and mechanical properties of wrought and AM Haynes 188. Most importantly, it illustrates a significant difference in microstructural response of the two materials to long term thermal exposure and its effect on mechanical properties.
Some Properties of the Exit Velocity Triangle of a Radial Compressor Impeller
Authors: Casey Michael , Robinson Chris
Published: October 2022

A diagram is described which demonstrates important aspects of the exit velocity triangle of a radial compressor impeller with no inlet swirl. Although this diagram is based on work dating back to 1941, it is not widely known in the radial compressor community. It aids the selection of the exit velocity triangle for impellers and gives significant insight into impeller-diffuser matching. It can be used to analyse performance maps from both experimental and CFD studies.

Important aspects made clear in the diagram are as follows:

• The degree of reaction and the de Haller number of the impeller are both determined primarily by the work coefficient, and both decrease as the work coefficient increases.

• The degree of reaction is also affected by the exit flow coefficient and for typical backswept impeller designs it remains nearly constant at off-design flow conditions.

• The inlet and exit velocity triangles can be shown in the same diagram to visualize the deceleration of the relative velocity along the casing streamline and of the meridional velocity across an impeller, together with the acceleration of the relative flow on the hub streamline.

• The slope of the impeller gas path work coefficient versus exit flow coefficient in this diagram at off-design conditions provides a new approach to estimate the mean slip factor from a measured or calculated compressor performance map.

• Different impeller design styles can be categorized in this diagram to show that different impellers are needed for use with vaned and vaneless diffusers.

• The absolute velocity at the diffuser inlet of a backswept impeller increases with a decrease in flow rate along the operating line, which is an important aid to compressor stability.
Part-Load of Steam Rankine Cycles for Solar Salts-Based Concentrating Solar Power Plants
Authors: Belverato Davide , Martelli Emanuele , Binotti Marco , Pilotti Lorenzo , Giaconia Alberto
Published: October 2022

This work proposes two ad hoc part-load control strategies for steam cycles adopted in concentrated solar power plants. The control strategies are designed to keep the molten salt temperature above the minimum allowed value set by solidification issues in the 30–100 % load range. Particularly critical is the temperature of molten salts in contact with the heat exchanger tubes, the so called skin temperature. The first control strategy adopts a turbine with controlled extraction and readmission valve while the second strategy employs a throttling valve and a feedwater preheating loop. Off-design simulations show that both strategies are capable of avoiding the molten salts solidification issue but at the cost of a non negligible penalty (up to −1.9 percentage points) in power block efficiency at low loads (30–50%). The off-design analysis considers also the effect of ambient temperature variations and the optimization of the cooling fan rotational speed. The results are used to derive best-fit polymonials relating the power block efficiency to the ambient temperature and load.
Conjugate Heat Transfer Characteristics in a Vane Blade With Different Dimple/Protrusion/Pin Fin Configuration for Trailing Region
Authors: Du Wei , Luo Lei , Wang Songtao
Published: October 2022

The high inlet temperature of gas turbine induces high heat load and serious thermal stress problem in the trailing because of the structural and aerodynamic limitations. Thus, it is vital to further improve the cooling performance in the trailing edge area. The configuration with dimple/protrusion/pin fin is proposed to increase the heat transfer and decrease the blade surface temperature in the trailing region. This paper numerically investigated the conjugate heat transfer characteristics in a vane blade with different dimple/protrusion/pin fin configurations for trailing region. There are three different dimple/protrusion locations (in the middle of two rows of pin fin, near the leading edge of each pin fin, a near the trailing edge of each pin fin) and two different dimple/protrusion depth are considered in this paper.

The inlet temperature for the hot gas is 1678K, the mass flow ratio of the cooling air is 6.3% of the hot gas. Seven different configurations for the dimple/protrusion/pin fin are involved. The temperature distribution, aerodynamic efficiency and cooling air loss are analyzed. It is found that the configurations of dimple/protrusion/pin fin have significant effect on the temperature distributions and aerodynamics of gas turbine. The pure pin fin configuration has the highest temperature in the trailing region and the pin fin combined with the protrusion configuration has the lowest temperature in the trailing region. The trailing edge temperature can drop up to 20 K after adoption the dimple/protrusion.
Operation of Large Industrial Gas Turbines During Periods of Low Electricity Demands
Authors: Ingistov Steve , Vassiliev Vladimir , Savic Sasha , Mulder Sebastiaan
Published: October 2022

When grid power demand is low or the power price is negative, running a gas turbine at Full Speed No Load (FSNL) provides a way to avoid producing power, while maintaining the ability to both generate process steam for industrial purposes in a Heat Recovery Steam Generator (HRSG) and to respond quickly to sudden surges in grid power demand. In this paper, turbine thermodynamics of FSNL, closure of inlet guide vanes (IGV), and compressor bleed rates are analysed for General Electric’s 7EA gas turbine using the software Thermoflow.

This study shows that FSNL can be achieved only by bleeding of compressor mass flow through two available bleeds, one in the front section of the compressor, and one in the back section of the turbine. This paper shows that bleeding from bleed 1 will lower compressor work, saving fuel, but it will also drop the exhaust temperature too low, preventing steam production. With extraction from bleed 2, the exhaust temperature remains high. Either way, the exhaust energy is reduced due to reduction of mass flow, but steam generation in reduced amount is possible. The extracted mass flow is choked and limited by the critical section in the flow path of the compressor bleed. In this study, the required minimal size of the slot in bleed 2 is identified for a range of IGV positions.
Assessment of the Flow Field and Heat Transfer in an NGV Using Magnetic Resonance Velocimetry, Thermochromic Liquid Crystals and CFD
Authors: Bruschewski Martin , Wüstenhagen Carolin , Domnick Clemens , Krewinkel Robert , Shiau Chao-Cheng , Grundmann Sven , Han Je-Chin
Published: October 2022

Computational Fluid Dynamics (CFD) is the standard tool in the turbomachinery industry to analyze and optimize internal cooling systems of turbine components, but the code applied has to be validated. This paper presents a combined experimental and numerical study on the flow field and heat transfer in a cooling system consisting of a three-pass serpentine with rib turbulators and trailing edge ejection. The cooling geometry is taken from a stator vane currently used in an industrial gas turbine and operates at a coolant inlet Reynolds number of 45,000. As an experimental technique, magnetic resonance velocimentry (MRV) was used to obtain the three-dimensional time-averaged velocity field of the isothermal flow. The measurements were conducted in a large-scale model and resulted in 3.2 million velocity vectors and a measurement uncertainty of 6.1% of the bulk inlet velocity. The local wall heat transfer was measured in a separate experiment using thermochromic liquid crystals (TLC). These measurements yielded the distribution of the heat transfer coefficient on both the pressure and the suction side internal walls with a measurement uncertainty of 12%. The experimental data are used as reference for the numerical study. In total, eight turbulence models are evaluated here, including one-equation, two-equation, algebraic and differential Reynolds stress models, and a scale-adaptive simulation. The results show the differences between the velocity fields and the heat transfer coefficient distribution, allowing for the identification of the optimum turbulence model for this particular type of flow.
Identification of Fluctuation Modes for a Cylindrical Film Cooling Hole Using the Spectral Proper Orthogonal Decomposition Method
Authors: Rosafio Nicola , De Cosmo Giove , Salvadori Simone , Carnevale Mauro , Misul Daniela Anna
Published: October 2022

Film cooling is the main technology adopted to guarantee safe working conditions of vanes and blades in high-pressure turbine stages. Recent experimental investigations highlighted that unsteady interaction between the coolant jet and the hot gas contributes to the lateral dispersion of cold flow over the cooled surface. Hence, considering the harsh working environment of these devices, a fair prediction of their thermal performance requires accurate modelling of the interaction between cold and hot gases. In this paper, an experimental setup originally studied at the University of Karlsruhe during the EU-funded TATEF project is numerically investigated to determine the influence of high-frequency unsteady fluctuations on the thermal performance of the cooling device. The case study consists of a film cooling hole positioned on a flat plate, working at engine-like conditions. Unsteady Reynolds-Averaged Navier-Stokes equations are solved for a compressible flow in transonic regime on a hybrid mesh. Turbulence is modelled using the Scale-Adaptive Simulation method to correctly predict the interaction between the coolant and the main flow. Three different sets of conditions are analyzed by varying the blowing ratio from 0.5 to 1.5, aiming at highlighting the unsteady mechanisms occurring for different penetrations of the coolant into the hot gas. Time-averaged unsteady results are compared with the available experimental data to determine to what extent hybrid modelling allows for correctly predicting film cooling performance at different blowing ratios. Instantaneous solutions are then analyzed to investigate the time-dependent flow field in the vicinity of the jet exit section and on the cooled surface. Spectral Proper Orthogonal Decomposition is enforced to identify the principal fluctuation modes associated with the time-dependent coolant penetration into the main flow.
Large Eddy Simulation Based Optimization of a Fan-Shaped Cooling Hole Geometry to Enhance Cooling Performance
Authors: Agarwal Shubham , Gicquel Laurent , Duchaine Florent , Odier Nicolas , Dombard Jérôme , Bonneau Damien , Slusarz Michel
Published: October 2022

In this study, a shaped hole optimization approach based on Large Eddy Simulations and Efficient Global Optimization (EGO) is presented. The shape of a fan-shaped hole used for turbine film cooling is then optimized to maximize the film cooling performance and the numerical problem is modeled using flow configurations close to those in real gas turbine conditions. Four of the most important geometrical parameters defining a cooling hole shape, namely the depth of the expanded section, the hole inclination angle and the forward and the lateral expansion angles are selected as the design variables to obtain the optimal hole shape. Forty design cases at start are selected via an Optimal Latin Hypercube Sampling method (OLHS) and further more are added during the successive iteration steps of the optimization algorithm. The handling of these design cases including the CAD creation of the geometries, computational domains, meshes and finally the numerical setup is handled by the LES based autonomous tool which has been previously validated [1]. Finally, the Bayesian based EGO [2] method along with the Expected Improvement (EI) as the acquisition function is used to maximize the surface averaged film cooling effectiveness as the objective function. After several database enrichment steps to reduce the overall modal error of the response surface an optimal shape of the cooling hole with the highest cooling performance is obtained. The optimal geometry thus obtained has a significantly higher cooling performance than the reference hole shape which is also confirmed via the study of the fluid flow distribution in both the cases. Overall, this study shows that, Large Eddy Simulations can be successfully coupled along with an EGO based optimization approach to obtain the optimal shaped cooling hole in a computer-aided optimization setting.
Using Machine Learning for Loss Prediction in a Hybrid Meanline Modeling Method to Deliver Improved Radial Turbine Performance Prediction
Authors: Ren Pangbo , Stuart Charles , Spence Stephen , Inomata Ryosuke , Kobayashi Takayuki , Morita Isao
Published: October 2022

Low fidelity modelling approaches remain attractive due to an unrivalled ability to predict full turbine performance maps quickly compared to high fidelity approaches such as CFD, especially in the preliminary design process. As improvements in performance on a component level approach a point of diminishing returns, the ability to efficiently optimize the complete charging system for a given duty is a topic attracting significant research interest. In the case of turbocharging applications, existing engine and powertrain simulations require turbine maps to calculate the turbine performance, which are usually obtained from experimental testing. Unfortunately, the need for extrapolation is unavoidable because of the limited range of testing data available, leading to inaccuracies especially at off-design conditions. To enable intensive modelling and optimization of complete vehicle powertrains for different drive cycles, the current piece of work seeks to combine the advantages of machine learning techniques and physical meanline modelling to facilitate faster, more accurate predictions of complete turbocharger maps.

This paper presents a novel methodology for turbocharger turbine rotor and nozzle performance prediction based on hybrid modelling. The turbine rotor and nozzle were parameterized to conduct CFD simulations for a wide variety of turbine geometries, which were used to form a database to train an Artificial Neural Network (ANN). The predicted losses provided by the ANN were then utilized in the meanline code, substituting for the conventional empirical loss models. As well as removing the need for empirical loss models, modifications were undertaken to the meanline approach to further enhance modelling accuracy. Firstly, in order to accurately characterize the stage mass flow capacity, the losses occurring in the nozzle and rotor were subdivided into those occurring before and after the throat. A second novel aspect is that the aerodynamic blockage level at the rotor throat was implemented as a variable rather than a constant value. By training the ANN to predict the variation of blockage with geometry and operating condition, a more accurate depiction of the changing secondary flow fields could be achieved.

The capabilities of the hybrid meanline modelling method were evaluated on several unseen test cases. The resulting predictions of efficiency and mass flow rate demonstrated strong correlation with CFD results and experimental test results. The hybrid meanline modelling method therefore displays great potential in wide range radial turbine performance prediction with enhanced accuracy in comparison to traditional approaches.
The New Chapter of Transonic Compressor Cascade Design at the DLR
Authors: Munoz Lopez Edwin J. , Hergt Alexander , Grund Sebastian
Published: October 2022

The approach to design compressor blades has been transformed over the years by the advent of efficient numerical optimization algorithms and increasing computing power. This has allowed designers to focus on finding the best optimization methodology for a desired application. However, transonic flow conditions on compressor blades still present considerable modeling and optimization challenges, making the optimization of even a 2D blade section a non-trivial undertaking. This paper then focuses on the design of a new state-of-the-art transonic compressor cascade for future wind tunnel test campaigns at the DLR. For this purpose, a thorough review was performed of similar cascades previously tested at the DLR’s Transonic Cascade Wind Tunnel. From this review, a main reference was picked corresponding to a modern cascade with notably good efficiency at high aerodynamic loading. The data gathered informed the definition of the optimization’s design strategy applied with the DLR’s in-house optimizer, AutoOpti. The process chain was evaluated with the DLR’s CFD solver for turbomachinery applications, TRACE, by performing RANS simulations with the k-ω SST turbulence model and γ-ReΘ transition model. The optimization was set to minimize two separate objective functions: the first one focused on the efficiency at the aerodynamic design point, while the second one was focused on the efficiency over the cascade’s working range. The result is a Pareto front of cascades with a wide variety of design characteristics and a considerable improvement in efficiency over the working range of about 24%. This improvement was achieved while maintaining a similar aerodynamic blade loading, quantified by a maximum increase of 3% of the de Haller number. Further post-optimization analyses were performed to select the “best” cascade for future wind tunnel test campaigns. The significant improvements obtained with respect to the reference and with a wide variety of cascade designs demonstrates that there is still much to be learned about blade design through optimization; even for 2D cascades and specially in transonic flow conditions.
Experimental Analysis of the Leakage Characteristics of Three Types of Annular Segmented Seals
Authors: Fourt Erwan , Arghir Mihai , Jolly Pascal , Andasmas Mohamed
Published: October 2022

This paper presents an experimental analysis of the leakage characteristics of three kind of segmented seals. The segments of the first seal has smooth pads while the second seal has pads with pockets. The pads of the third seal are smooth but the rotor is textured with inclined grooves. The pockets or the textures lift the segments from the rotor and create a radial clearance. This is reflected by the leakage flow rate, the friction torque and the seal’s temperature. These characteristics are hereby measured on a dedicated test rig. The presented results are dimensionless, the measured values for the three types of seals types being divided by the same maximum value. This makes it possible to compare the performance of different segmented seal technologies. The assumptions made on the position of the segment during the tests (opened or closed against the rotor) are thus verified.
Multi-Fidelity Simulation for Secondary Air System Seal Design in Aero Engines
Authors: Nasti Adele , Voutchkov Ivan I. , Toal David J. J. , Keane Andrew J.
Published: October 2022

Secondary air system seals in aero engines sit at the intersection between all the major aspects of the physics of the system. Their behavior is affected by the air system, the thermal physics, the effect of flight loads and is highly dependent on the engine component movements, the operating conditions, and the supporting hardware. Due to the number of functional and physical interfaces in the engine, seal design is therefore a highly coupled multi-physics problem and requires multiple iterations during the design process to converge to a solution that meets system requirements and optimizes engine specific fuel consumption.

At different stages of the design process, simulation models with different levels of fidelity can be built. Due to the long runtimes of high-fidelity coupled multi-disciplinary models and to the iterative nature of the process, seal design in industry presents significant computational cost challenges, in particular in the phases of the design that require multiple simulation runs.

Multi-fidelity computational techniques for surrogate modelling and optimization such as Kriging and co-Kriging have been demonstrated on a number of industrial applications and have the potential to significantly reduce the number of function evaluations for computationally expensive optimization problems, improve the accuracy of the predictions of surrogate models and allow the development of improved simulation strategies for a specific product design.

This paper demonstrates the use of multi-fidelity simulation techniques on aero engine secondary air system seal design and shows how these techniques can be used in the context of system, sub-system and component design. This is achieved by combining results from a simple two-dimensional Finite Element Analysis with those from a coupled secondary air system-thermomechanical model.

Depending on the stage of the design process and on the specific design decisions being made, the use of computational power in simulation often comes down to a trade-off between reduced overall computational time and improved result accuracy. Multi-fidelity simulation frameworks provide the environment to drive holistic choices on the simulation strategy, reducing the cost of the design and offering agility in the industrial response to market changes or new technologies. Moreover, this methodology establishes an infrastructure for updating the virtual product at each step of the product lifecycle, allowing experimental or service data to feed the system-level simulation models to produce a digital twin.