bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Laser Shock Peening on Fatigue Life of Full Scale Turbine Blades
Authors: Chen Cao , Zhang Xiaoyong , Han Lei , Yan Xiaojun
Published: August 2017

Laser shock peening (LSP) is a promising surface treatment method for improving fatigue properties of turbine blades. The effect of LSP on combined low and high cycle fatigue (CCF) life of full scale turbine blade was investigated. The LSP is performed by YLSS-40 LSP equipment and the laser power density is 5.8 GW/cm2. Thirteen LSP treated turbine blades and thirteen untreated turbine blades were selected to carry out the contrast test at high temperature in a bench environment. Experimental results show that there exists a critical vibration stress of blades, below which the CCF life was significantly prolonged by LSP, and above which the LSP has no effect or an adverse effect on the CCF life. The safe life of blades can be significantly increased after treated by LSP when the total stress is below the yield stress. However, the situation is a bit different when the total stress is above the yield stress. Although the safe life of LSP blades is longer than that of untreated blades in this situation, but the median life of blades is decreased after treated by LSP. The effect of LSP on the scatter in life plays a greater role in improving the safe life that directly leads to the safe life of LSP blades longer than the safe life of untreated blades when the total stress is above the yield stress.
Effect of Stage Axial Distances on the Aerodynamic Performance of Three-Stage Axial Turbine Using Experimental Measurements and Numerical Simulations
Authors: Chen Yang , Zhong Zhuhai , Li Jun , Zhou Weijiu , Zhong Gangyun , Sun Qi , Ping Yan , Wang Shan
Published: August 2017

The stage axial distance significantly influences the aerodynamic performance of turbines under some constraints. Experimental measurements and numerical simulations are used to analyze the effect of stage axial distances on the aerodynamic performance of three-stage axial turbine in this work. The aerodynamic performance of three-stage axial turbine with three different stage axial distances is experimentally measured at the air turbine test rig of Dongfang Steam Turbine Co. LTD. Experimental results show that efficiency increases when the stage axial distance decreases for the geometry under study with relative stage distance ranged from 0.14 to 0.35, and the effect of stage axial distance on the optimization velocity ratio here is very limited. In addition, unsteady Reynolds-Averaged Navier-Stokes (RANS) simulations were carried out with nonlinear harmonic method to analyze the detailed flow field of the experimental three-stage axial turbine. The numerical aerodynamic efficiency of three-stage axial turbine is in good agreement with the experimental data. Furthermore, the small stage axial distance is preferred for the higher efficiency. The detailed flow field and aerodynamic parameters of three-stage axial turbine are also illustrated and discussed.
Micro-Gas Turbine Feed With Natural Gas and Synthesis Gas: Variation of the Turbomachines’ Operative Conditions With and Without Steam Injection
Authors: Renzi Massimiliano , Caligiuri Carlo , Rossi Mosè
Published: August 2017

In this work, the performances of a 100 kW Micro Gas Turbine (MGT) fed by Natural Gas (NG) and three different biomass-derived Synthesis Gases (SGs) have been assessed using a MATLAB® simulation algorithm. The set of equations in the algorithm includes the thermodynamic transformations of the working fluid in each component, the performance maps that describe the turbomachines’ isentropic efficiencies and pressure ratios as a function of the reduced mass flow rate and the reduced rotational speed, the performance and the pressure losses in each component, as well as the consumption of the other auxiliary devices.

The electric power output, achieved using SGs, turns out to be lower or higher with respect to the one produced with the NG, depending on the fuel Lower Heating Value (LHV) but also largely on the variation of the working fluid composition.

In this work, the effect of the steam injection on the MGT performance characteristics has been also investigated. Steam injection allows to obtain higher power and efficiencies using both NG and SGs at the rated rotational speed, mainly thanks to the increase of the turbine enthalpy drop and the reduction of the compressor consumption. Attention must be paid to the risk of the compressor stall, especially when using SGs, as the mass flow rate processed by the compressor decreases significantly.

Moreover, another advantage of adopting the steam injection technique lies in the increased flexibility of the system: according to the users’ needs, the discharged heat can be exploited to generate steam, thus to enhance the electric performances, or to supply thermal power.
A Comprehensive Investigation of Blade Row Interaction Effects on Stator Loss Utilizing Vane Clocking
Authors: Smith Natalie R. , Key Nicole L.
Published: August 2017

Blade row interactions drive the unsteady performance of high pressure compressors. Vane clocking is the relative circumferential positioning of consecutive stationary vane rows with the same vane count. By altering the upstream vane wake’s path with respect to the downstream vane, vane clocking changes the blade row interactions and results in a change in steady total pressure loss on the downstream vane. The open literature lacks a conclusive discussion of the flow physics governing these interactions in compressors. This paper presents the details of a comprehensive vane clocking study on the embedded stage of the Purdue 3-stage axial compressor. The steady loss results, including radial total pressure profiles and surface flow visualization, suggest a shift in the Stator 2 corner separations occurs between clocking configurations associated with the maximum and minimum total pressure loss. To better understand the flow mechanisms driving the vane clocking effects on the steady Stator 2 performance, time-resolved interrogations of the Stator 2 inlet flow field, surface pressure unsteadiness, and boundary layer response were conducted. The Stator 2 surface flows, both pressure unsteadiness and boundary layer transition, are influenced by vane clocking and interactions between Rotor 1 and Rotor 2, but neither of these results indicate a cause for the change in steady total pressure loss. Moreover, they are a result of upstream changes in the flow field: the interaction between the Stator 1 wake and Rotor 2 results in a circumferentially varying pattern which alters the inlet flow field for the downstream row, including the unsteadiness and frequency content in the tip and hub regions. Therefore, under different clocking configurations, Stator 2 experiences significantly different inlet blockage and unsteadiness from the Rotor 2 tip leakage flow and hub corner separation, which, in turn, shifts the radial blade loading distribution and subsequent loss development of Stator 2.
Uncertainty Quantification of Conjugate Heat Transfer of a Cooled Turbine Vane: Roughness Effect
Authors: Shi Wei , Li Weihong , Shi Bo , Li Xueying , Ren Jing , Jiang Hongde
Published: August 2017

HP turbine usually works in complex operation conditions and subjects to strong temperature variability and thermal gradients. For these reasons, some small variations caused by manufacturing process and operation conditions will yield great effect on the heat transfer performance and the life of hot components.

UQ is a state of the art that seeks to provide a framework for calculating the effects of input parameter uncertainty on model output variables. This study presents an investigation of the uncertainty quantification (UQ) of conjugate heat transfer of a typical high load HP cooled turbine vane, considering the influence of total inlet temperature, turbulence intensity and different surface roughness level. The non-intrusive Probabilistic Collocation Method, integrated with sparse grid quadrature has been used in the UQ analysis. The scaled sensitivity analysis is also carried out to assess the influence of each input uncertainty on the output response.

The UQ analysis implies that the increasing of surface roughness will enlarge uncertainty of metal wall temperature. As a result, it needs to amplify the safety margin coefficient in order to assess the turbine guide vane surface temperature distribution and service life.
Measurements and Modeling of the Dynamic Response of a Pilot Stabilized Premixed Flame Under Dual-Input Perturbation
Authors: Li Chunyan , Li Suhui , Cheng Xu , Zhu Min
Published: August 2017

Pilot flame have been widely used for flame stabilization in low-emission gas turbine combustors. However, effects of pilot flame on dynamic instabilities are not well understood. In this work, the dynamic interactions between main and pilot flames were studied by measurements and modeling in the flame response, with both flames subjected to perturbation, i.e., with a dual-input forcing. The paper analyzed the experimental results of both the total flame response and the interaction process. A burner was designed with central pilot flame to stabilize a premixed axi-symmetric V-shaped methane flame. Servo valve and sirens were used to generate forcing in the pilot and main flames, respectively. A diagnostic system was applied to measure the flame structure and heat release rate. The effects of forcing frequency, forcing amplitude, phase difference between the two forcing signals to the main and pilot flames as well as the Reynolds number were studied. Both the flame transfer function (FTF) and the flame dynamic structure were measured and discussed. It was found that the total flame response was modified by the perturbation in the pilot flame. The mechanism may be lying in the effect of pilot flame on the flow field of the burnt side. To further testify the hypothesis, an analytical model was developed based on the linearized G-equation with low amplitude assumptions. Although the assumptions made in the model to address the effect of pilot flame on the burnt flame flow field were simplified, good agreements were found between the prediction and the experiment results. Based on the analysis conducted in this paper, some further considerations may be needed when developing combustion systems with a central injection, since perturbations in the pilot flame may affect the performance of the main flame. Further experiments and analysis may be needed to dig deeper into the physical basics such as measurements or more realistic modeling of the flow fields and non-linear effects.
Analytical Dynamic Model of Statically Indeterminate Rotor System and Misalignment
Authors: Zhao Guang , Li Shengxiang , Zhang Yunqiu , Xiong Zhiliang , Han Qingkai
Published: August 2017

For the statically indeterminate rotor structure of low-pressure rotor system in aero-engine, mechanics features of bearing deformation and rotor structure were analyzed, combined with the principle of virtual work, and the global stiffness matrix of the rotor system was deduced. According to the Lagrange method, the analytical dynamic model of statically indeterminate rotor system with three flexible supports based on the flexibility analysis was built. An analytical dynamic model of intermediate supporting misalignment was established on the basis of the model. The natural characteristic and unbalance response of aligned and misaligned statically indeterminate rotor system were obtained through the analytical solution, and the experimental verification was conducted. These findings indicate that intermediate bearing misalignment of statically indeterminate rotor system can not only produce the 2X component, but also make the 1X component change. The experimental results are essentially in agreement with the calculated ones. The study laid the foundations for model basis and experimental reference of the statically indeterminate rotor system design, dynamic modeling and vibration control.
Performance Evaluation of a Molten Carbonate Fuel Cell/Micro Gas Turbine Hybrid System With Oxy-Combustion Carbon Capture
Authors: Ahn Ji Ho , Kim Tong Seop
Published: August 2017

Owing to the increasing consumption of fossil fuels and emission of greenhouse gases, interests in highly efficient and low carbon emitting power systems are growing fast. Several research groups have been suggesting advanced systems based on fuel cells and have also been applying carbon capture and storage technology to satisfy the demand for clean energy. In this study, the performance of a hybrid system, which is a combination of a molten carbonate fuel cell (MCFC) with oxy-combustion carbon capture and an indirectly fired micro gas turbine (MGT) was predicted. A 2.5MW MCFC system that is used in commercial applications was used as the reference system so that the results of the study could be applicable to practical situations. The ambient pressure type hybrid system was modeled by referring to the design parameters of an MGT that is currently being developed. A semi-closed type design characterized by flow recirculation was adopted for this hybrid system. A part of the recirculating gas is converted into liquefied carbon dioxide and captured for storage at the carbon separation unit. Almost 100% carbon dioxide capture is possible with this system. In these systems, the output power of the fuel cell is larger than in the normal hybrid system without carbon capture because the partial pressure of carbon dioxide increases. The increased cell power partially compensates for the power loss due to the carbon capture and MGT power reduction. The dependence of net system efficiency of the oxy-hybrid on compressor pressure ratio is marginal, especially beyond an optimal value.
Finite Element Analysis of Thermal-Mechanical Behavior in the Thermal Barrier Coatings With Cooling Hole Structure
Authors: Jiang Jishen , Cai Zhenwei , Wang Weizhe , Liu Yingzheng
Published: August 2017

The present work aims to investigate the thermal-mechanical behavior in thermal barrier coatings (TBCs) with a round film cooling hole under gas turbine operating conditions. The adiabatic wall temperatures and surface heat transfer coefficients are firstly calculated for thermal boundary conditions. Subsequently, stress analyses during both thermal exposure and cooling down period are presented. The results show that: although the cooling hole has lower temperature, large stress concentration still appears because of the geometry of cooling holes and thermal mismatch between TBCs and substrate. The huge thermal stress may lead to pre-mature failure of TBCs, which should be carefully considered in the design of film cooling-TBC system.
Effects of Equivalence Ratio on the Off-Design Combustion Performance of Adjustable Fuel Feeding Combustor for a Micro-Gas Turbine
Authors: Xing Chang , Qiu Penghua , Liu Li , Shen Wenkai , Lyu Yajin , Zhang Zhuo , Sun Jingyi , Wu Shaohua , Qin Yukun
Published: August 2017

To improve off-design operation performance of micro-gas turbine, we proposed an adjustable fuel feeding combustor (AFFC), and it employed the lean premixed swirling combustion technology and the adjustable fuel feeding method (AFFM). The AFFM was achieved by switching the various working groups of main fuel tube, and represented by its unique characteristic number (U). To verify the availability of adopted models, the AFFC combustion performance was investigated numerically at different equivalence ratios (ϕ) in ANSYS CFX. The results indicate that NO emission has various trends with the rising U under different ϕ due to the coupling influence of fuel flow and jet velocity in each working main fuel tube. Although the AFFM has almost no effect on the distribution of outlet temperature and the length of primary recirculation zone, the maximum and non-uniform coefficient of outlet temperature increase with the rising U.
Investigations on Rotordynamic Characteristics of a Floating Ring Seal Considering Structural Elasticity
Authors: Xia Peng , Zhang Guanghui , Zhao Jingming , Liu Zhansheng
Published: August 2017

Under high pressure, the elastic deformation of floating ring seals has a significant influence on the seal leakage flowrate and rotordynamic coefficients. The present study establishes a coupled model of the clearance flow and elastic structure of floating rings with bulk flow model and finite element method. The results show that the structural deformation reduces the clearance thickness and decreases the leakage flowrate. On the other hand, the elastic deformation reduces the direct stiffness, and increases the cross-coupled damping and inertia coefficients. In addition, the deformation induces the cross-coupled stiffness and direct damping to increase rapidly with increasing eccentricity ratio. Generally, the structural deformation deteriorates the rotordynamic characteristics of floating ring seals. In order to alleviate the adverse influences, a deformation compensation method is presented and proved to be effective.
Measurement of Film Cooling Effectiveness for the First-Stage Vane and Endwall of a Gas Turbine With Fan-Shaped Holes
Authors: Jeong Jin Young , Kwak Jae Su , Park Jung Shin , Lee Kidon
Published: August 2017

The adiabatic film cooling effectiveness for the first-stage vane and endwall of a gas turbine were investigated in a low speed cascade using the pressure sensitive paint (PSP) technique. The cascade consisted of four linear vanes. The tested Reynolds number based on the vane chord and vane exit velocity was 7.15 × 105. The overall blowing ratio of the coolant was controlled between 1 to 2, and two density ratios, 1.5 and 2.0, were tested. In order to test the different density ratios, two different coolants were used, one carbon dioxide and the other a mixture of nitrogen and sulfur hexafluoride. All cases showed clear traces of coolant on the vane surfaces and the endwall. The film cooling effectiveness near the film cooling holes was very high and gradually decreased downstream. The coolant trace showed an almost two-dimensional distribution on the pressure side. However, the coolant on the suction side shifted mid-span due to the passage vortex. Generally, the film cooling effectiveness on the vane and the endwall increased as the blowing ratio increased. The film cooling effectiveness on the vane was strongly affected by the shower head injection. Depending on the blowing ratio, the effect of density ratio on the vane surface film cooling effectiveness was varied. On the endwall, the film cooling effectiveness was higher for higher density ratio cases.
Design Parameters Prediction of New Type Gas Turbine Based on a Hybrid GRA-SVM Prediction Model
Authors: Wei Tingting , Zhou Dengji , Chen Jinwei , Cui Yaoxin , Zhang Huisheng
Published: August 2017

Since the late 1930s, gas turbine has begun to develop rapidly. To improve the economic and safety of gas turbine, new types were generated frequently by Original Equipment Manufacture (OEM). In this paper, a hybrid GRA-SVM prediction model is established to predict the main design parameters of new type gas turbines, based on the combination of Grey Relational Analysis (GRA) and Support Vector Machine (SVM). The parameters are classified into two types, system performance parameters reflecting market demands and technology development, and component performance parameters reflecting technology development and coupling connections. The regularity based on GRA determines the prediction order, then new type gas turbine parameters can be predicted with known system parameters. The model is verified by the application to SGT600. In this way, the evolution rule can be obtained with the development of gas turbine technology, and the improvement potential of several components can be predicted which will provide supports for overall performance design.
A New Heat Transfer Correlation for Supercritical RP-3 Flowing in Vertical Tubes
Authors: Wang Longyun , Tao Zhi , Zhu Jianqin , Li Haiwang , Cheng Zeyuan
Published: August 2017

A new empirical correlation for upward flowing supercritical aviation kerosene RP-3 in the vertical tubes is proposed. In order to obtain the database, numerical simulation with a four-component surrogate model on RP-3 and LS low Reynolds turbulence model in vertical circular tube has been performed. Tubes of diameter 2mm to 10mm are studied and operating conditions cover pressure from 3MPa to 6MPa. Heat flux is 500KW/m2, mass flow rate is 700kg/(m2·s). The numerical results on wall temperature distribution under various conditions are compared with experimental data and a good agreement is achieved. The existing correlations are summarized and classified into three categories. Three representative correlations of each category are selected out to evaluate the applicability in heat transfer of supercritical RP-3. The result shows that correlations concluded from water and carbon-dioxide do not perform well in predicting heat transfer of hydrocarbon fuel. The mean absolute deviation of them is up to 20% and predict about 80% of the entire database within 30% error bands. So a new correlation which is applicable to different working conditions for supercritical RP-3 is put forward. Gnielinski type has been adapted as the basis of the new correlation for its higher accuracy. In consideration of major influence factors of supercritical heat transfer, correction terms of density and buoyancy effect are added in. The new correlation has a MAD of 9.26%, predicting 90.6% of the entire database within ±15% error bands. The comparisons validate the applicability of the new correlation.
Influence of Adjustable Inlet Guide Vanes on the Performance Characteristics of a Shrouded Centrifugal Compressor
Authors: Tian Yubao , Tang Yonghong , Wang Zhiheng , Xi Guang
Published: August 2017

A shrouded centrifugal compressor model stage used for 120,000 m3/h oxygen production air separation unit was designed and tested at several IGV stagger angles from −15° to +60° and machine Mach number from 0.97 to 0.5. Present research works aimed to assess the influence of the adjustable IGVs and the IGV modeling on the shrouded centrifugal compressor performance characteristics and inlet flow field and to explore the effect factors of the CFD prediction accuracy and compressor stability at different IGV stagger angles. The measured results show that the model stage with 0° IGV stagger angle yields almost the same stagnation pressure ratio performance as the stage-only model but at a lower peak isentropic efficiency. With an appropriate IGV stagger angle setting ranging from −15° to +30°, the compressor stability could be efficiently enhanced. Numerical studies indicate that a large IGV hub gap may lead to a significant lag effect on the flow angle generated by the inlet guide vanes when increasing the IGV stagger angle.
Global Three-Dimensional Surrogate Modeling of Gas Turbine Aerodynamic Performance
Authors: Leylek Zafer , Neely A. J.
Published: August 2017

Turbine blade aerodynamic performance can be accurately predicted using one-dimensional mean-line and two-dimensional through-flow solvers. These predictions have been achieved by coupling one and two-dimensional ideal flow equations with blade aerodynamic loss and flow deviation angle models. These loss and deviation models are largely generated using classical cascade testing which have limitations and constraints. These limitations are associated with testing in general and include scope, time, resources, geometric and operating parameter space, data scatter and uncertainty. The models largely ignore interaction effects and can be subjective. The loss and deviation models also do not incorporate blade features associated with modern turbine blades. The objective of this paper is to study the feasibility of conducting these experiments numerically using three-dimensional turbine blade and constructing global blade performance and loss models.

The study looks at a number of competing surrogate modeling techniques and evaluates their performance for optimum blade loss and deviation prediction. The effect of Reynolds number, performance parameter definition, operating condition specification along with the use of extended parameters are investigated to further enhance the surrogate models. The performance map generated using the optimized surrogate models is then validated using a 1.5 stage axial turbine. The results show that numerically generated surrogate models can be used to accurately predict the CFD based axial turbine performance.
Investigation of Hydrogen Enriched Methane Flame in a Dry Low Emission Industrial Prototype Burner at Atmospheric Pressure Conditions
Authors: Subash Arman Ahamed , Collin Robert , Aldén Marcus , Kundu Atanu , Klingmann Jens
Published: August 2017

Experiments were performed on a prototype 4th generation DLE (dry low emission) burner under atmospheric pressure conditions to investigate the effects of hydrogen (H2) enrichment on methane (CH4) flames. The burner assembly was designed to have three concentrically arranged premixed sections: an outer Main section, an intermediate section (Pilot) and a central pilot body termed the RPL (Rich-Pilot-Lean) section. The Planar laser-induced fluorescence (PLIF) of OH radicals together with flame chemiluminescence imaging were employed for studying the local flame characteristics so as to be able to investigate the turbulence-flame interactions and the location of the reaction zone at the burner exit. Flames were investigated for three different fuel mixtures having hydrogen (H2)/methane (CH4) in vol. % concentration of 0/100, 25/75 and 50/50. The results show that the characteristics of the flames are clearly affected by the addition of hydrogen and the effects are expected due to the faster reaction rate, higher diffusivity and higher laminar burning velocity of H2. Enriching the flame with H2 at a constant global phi (ϕ) is found to shorten the total extension of the flame due to the higher laminar flame speed. The OH signal distribution becomes thicker and more pronounced due to the higher production of OH radicals, and the flame stabilization zone that is produced after the burner throat, moves further downstream. At a constant global ϕ in altering the RPL and the Pilot ϕ, similar changes for both 0/100 and 25/75 (in vol. %) of the H2/CH4 fuel mixtures can be observed. At a rich RPL ϕ, the secondary RPL flame contributes to the main flame and to determining the flame stabilization position. The flame stabilization zone located after the burner throat moves further downstream with an increase in the RPL ϕ. When the PFR (Pilot fuel ratio) increases, the extension of the flame shortens and the flame stabilization zone moves upstream. Combustion emissions were also determined so as to observe the effects of the H2 enrichment on the NOX level.
Analysis on Solid Particle Erosion in the Governing Stage of a High-Parameter Steam Turbine
Authors: Hu Peng-fei , Li Yong , Cao Li-hua , Zhang Tao
Published: August 2017

The solid particle erosion (SPE) of flow passage is a universal problem in modern high-parameter steam turbines. With the continuous improvement of the working parameters of the steam turbine, the problem of SPE is becoming more serious. This problem is caused by the ferric oxide exfoliations carried by steam from the inner wall of the boiler tube into the steam turbine flow passage, causing the stator blades, the rotor blades, and the shroud to be eroded under impingement and scuffing failure. The SPE cannot only destroy the blade profile, increase the roughness of the blade surface, and affect the aerodynamic performance of the blade, but it can also shorten the maintenance cycle, prolong the maintenance downtime, and even increase the cost for steam turbine maintenance thereby reducing the unit efficiency and safety.

In order to simulate SPE in the governing stage of a high-parameter steam turbine, this study adopts the Lagrange method and the Finnie erosion model. The motion characteristics of five different kinds of solid particle, including the solid particle trajectory, are thoroughly analyzed. The regulation of the erosion distribution in the radial and axial directions to the stator and rotor blades is studied to present the mechanism of SPE.

Simulated results show that before their collision with the blades, the particles of the small diameters flow with the main stream, and their trajectories are close to the steam streamlines. By contrast, the particles of the large diameters are hardly influenced by the external factors, and their trajectories are close to the straight line. The SPE distribution of the stator and rotor blades varies with the particle diameter. The eroded area in the stator blade is mainly located at the leading edge and the pressure surface, particularly the mid-rear part of the pressure surface, whereas no eroded area can be observed in the suction surface. The small particles greatly affect the erosion distribution of the stator blade. The eroded area in the rotor blade is primarily at the mid-rear part of the pressure surface and the suction surface, which is close to the leading edge. The eroded area takes on a typical slop shape, and the erosion position has an obvious upward trend.

The proposed research reveals both the motion characteristics of the solid particles and the distribution regulation of the SPE in the steam turbine flow passage. The analysis results provide references for the governing stage of a high-parameter steam turbine to prevent SPE.
Impact of Vortex Produced by a Novel Curve-Micro Vortex Generator on Secondary Flow in Compressor Cascade
Authors: Ma Shan , Chu Wuli , Zhang Haoguang , Li Lanpan , Lang Jinhua
Published: August 2017

The performance of compressor cascade is considerably influenced by secondary flow. An extensive experimental study of vortex generator (VG) applied on axial compressor was conducted by many scholars, in order to control these effects. Particularly, MVG is one of the hot researches in present to restrain secondary flow. On the foundation of research experience finished by the former scholars, a new Curve-micro vortex generator (C-MVG) was proposed in this paper. In order to investigate the effect of C-MVG on secondary flow in low-Mach number cascade, the present was carried out on a high-loaded axial compressor cascade with incoming flow of Ma<0.3. The experiment of baseline was conducted at a low speed (incompressible) cascade wind tunnel. The C-MVGs were placed on the end-wall at a distance of 7% chord length ahead of passage and a pitch distance of 26 mm from the leading edge of suction side. 8 cases with different spacing and θVGs were calculated. The height of all the C-MVGs were 5 mm and each case was comprised of 3 vanes.

At design and stall incidence angle (−1 deg and 8 deg), the total pressure loss coefficient averaged by mass-flow (Loss) in the outlet was analyzed with numerical method of k-omega turbulence model. Different combinations of C-MVGs were compared. Results show that the Loss in 140% axial chord length (Ca) after leading edge was increased on design condition. At 8 deg incidence angle, all cases could delay the inception of separation and decrease loss. The case VGθ3 showed the highest loss reduction benefit of 7.3%, which indicated that C-MVGs could control the large separation area effectively.
Research on Cooling Uniformity Based on Image Analysis Method
Authors: Wu Hong , Yang Deng Wen
Published: August 2017

Cooling uniformity is of crucial importance for the cooling structure design of turbine vane and rotor blade. However, there exist no veritable quantification of the uniformity. This paper, for the first time, reveals the correlation between temperature distribution uniformities of the temperature image and its textural features, and five texture measures are employed to characterize these features and quantify the temperature distribution uniformity from different angles. Finally, their linear weighted combinations are proposed to obtain a comprehensive evaluation, and thus a systematic and quantitative methodology for cooling uniformity evaluation is established. Moreover, this method is exemplified through a flat-plate jet array impingement cooling model, where cooling uniformities over the impingement target surface under five cases are compared. Results show that both the cooling uniformity sequence and the relative changes of the uniformity composite index between the ranking agree well with those of the corresponding thermal stress analyses. This method shows a promising application in the design and optimization of cooling structures for gas turbine hot components, such as film cooling and impingement cooling.
Development and Validation of a Novel Synthetic Blade Model for Axial Flow Fans in Unsteady CFD
Authors: Bonanni Tommaso , Corsini Alessandro , Delibra Giovanni , Volponi David
Published: August 2017

Here we present a Synthetic Blade Model (SBM) for axial flow fans, derived from Actuator Disk and Actuator Line theories. This new approach is able to model the momentum exchange between the fan and the fluid by adding source terms into momentum equation, like an actuator disk. However, the model accounts for the position of the blades, their rotation and the non-uniform distribution of deflection capability in the blade-to-blade passage, like in an actuator line model.

This approach is derived, described and validated against available data on a reversible tunnel and metro fan.
Cavitation Model Verification and Validation for Water and Liquid Nitrogen in an Inducer
Authors: Zhang Yuqiao , Li Xuesong , Li Yuhong
Published: August 2017

Cavitation is the formation of vapor bubbles within a liquid where flow dynamics cause the local static pressure to drop below the saturation pressure. Compared to the water, cavitation in cryogens is more complex due to the thermodynamic effects of cryogens. Existing Computational fluid dynamics (CFD) methods for water may not simulate the cryogens accurately. This paper presents the steady CFD results of cavitation in water and liquid nitrogen flow through a rotating inducer with four different cavitation models, and the experimental results are displayed to compare with the CFD results to verify the cavitation models’ applicability in water and the liquid nitrogen. The four cavitation models could simulate the cavitation flow in water, and the simulation result presents a consistent trend, which is stable in the high σ regime and drop down suddenly due to the blockage in blade passages caused by vapor as the cavitation number decreases. The “Zwart-Gerber-Belamri model” and the “Schnerr & Sauer model” have better performance on simulating the cavitation flow in water compared with the other two models, and the simulation results are close to the experimental one. The full cavitation model is applicable for cavitation prediction in liquid nitrogen, and the results of other three models are not satisfactory in liquid nitrogen.
Reduction of Pressure Losses in a Linear Cascade Using Herringbone Riblets
Authors: Liu Qiang , Zhong Shan , Li Lin
Published: August 2017

This paper presents the results from the first experimental assessment of herringbone riblets in reducing total pressure losses in a linear cascade of diffuser blades. The experiments were undertaken at Re = 1 × 105, M = 0.13 and a free stream turbulent intensity of 2%. Three cascade configurations were examined at a blade incidence angle of 0.8°; Case A: the baseline case without surface modification; Case B: blades with smooth strips; Case C: blades with ribleted strips. In Case A, flow separation starts at 24.1%c from the blade leading edge followed by a complete stall, resulting in significant total pressure losses as measured by a five-hole probe on a cross-flow plane downstream. Seven smooth or ribleted strips were adhered on the blade suction surfaces along their span in Case B and Case C. In comparison to Case A, the average total pressure loss coefficient is decreased by 6.4% and 16.8% in Case B and Case C, respectively. The velocity vectors leaving the cross-flow measurement plane also appear to be more uniformly distributed with the average flow turning angle being increased by 4° and 10° in Case B and Case C respectively, indicating that the extent of flow separation in the cascade has been reduced substantially. Furthermore, a pseudo sound power analysis of hot-wire data in the blade wake reveals a reduction in the noise level of 1.1dB and 1.6 dB, respectively. These results hence provide strong evidence that a profound aerodynamic improvement can be achieved in a cascade with the use of herringbone riblets.
Numerical Tests on the Effect Factors of the Last Stage Blade for Low Pressure Exhaust Hood Simulation
Authors: Meng Liu , Yang Chen , Zhuhai Zhong , Xiaodan Zhang , Guoliang Deng , Yin Mingyan , Li Jun , Sun Qi
Published: August 2017

Kinetic energy recovery is a key objective for low pressure exhaust hood design and optimization. Numerical simulation of the exhaust hood helps the engineers to explore and confirm the causes of the loss in the hood. Many studies have suggested that it is necessary for the simulation to include the last stage blade to get a realistic assessment. For the sole exhaust hood study, the inlet boundary condition is hard to set precisely like the downstream flow of the last stage blade. And the studies have also shown that the performances generated from the simulations may vary evidently between the sole exhaust hood and exhaust hood with last stage blade. It is obvious that the blade influences the exhaust hood, but the exact effect factors of the blade and the way they work are not thoroughly discussed. This paper has conducted many numerical tests to audit the influence of the common effect factors of the last stage blade. The internal flow field of the exhaust hood was numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions based on the ANSYS-CFX. In the first part of the paper, the tests are conducted by changing each effect factor of the inlet boundary condition for sole exhaust hood studies. These factors include the mass flow flux, the angle of the exit flow of the last stage, both the circumferential and the radial ones, and the speed and position of the jet-flow downstream of the seal over the shroud of the bucket. The tests show that each factor has its own distinctive style and extent for influence. Some of them may maximize the performance at some certain point, and some may deteriorate the performance rapidly beyond a threshold. And some factors may change the performance insignificantly within a wide range. However, these influences are not good enough to be consistent with the difference between the sole exhaust hood and the hood with blade simulations. In the second part of this paper, the focus locates on the direction of the jet-flow of the bucket seal. The tests prove that this direction is the prominent factor to influence the exhaust hood performance. Some extra tests for the seal have also been conducted to analyze this factor. The static pressure recovery for the simulation with labyrinth seal is about only half of the sole exhaust hood simulation. The discussion of these tests show that the seal jet is the main cause for this performance dive, and explain how the seal jet direction changes the flow field of the exhaust hood. It also suggests that the procedure to optimize the seal design is not mature yet, for some nature of the jet-flow remains unclear. It may need more detailed study in the future.
Numerical Study of Pyrolysis Effects on Supercritical-Pressure Flow and Conjugate Heat Transfer of N-Decane in the Square Channel
Authors: Hu Xizhuo , Tao Zhi , Zhu Jianqin , Li Haiwang
Published: August 2017

Regenerative cooling has become the most effective and practical method of thermal protection to the high temperature structures of scramjet engines. Pyrolytic reactions of endothermic hydrocarbon fuel have significant influence on the regenerative cooling process at high temperature due to a large amount of heat absorption and fluid components change. In this paper, a three-dimensional (3D) model is developed for numerically investigating the flow and heat transfer of pyrolytic reacted n-decane in the square engine cooling channel under supercritical pressure with asymmetrical heating imposed on the bottom channel surface. The one-step global pyrolytic reaction mechanism consisting of 18 species is adopted to simulate the pyrolysis process of n-decane. The governing equations for species continuum, momentum, energy and the k-ω turbulence equation are properly solved, with accurate computations of the thermophysical and transport properties of fluid mixture, which undergo drastic variations and exert strong impact on fluid flow and heat transfer process in the channel. The numerical method is validated based on the good agreement between the current predictions and the experimental data. Numerical studies of the pyrolysis effects on the characteristics of flow resistance and conjugate heat transfer under various operating conditions have been conducted. Results reveal that pyrolysis intensively takes place in high temperature regions. The pressure drop along the channel steeply rise due to the further fluid acceleration caused by pyrolysis. It is found that the variations of heat flux at the bottom, top and side fluid-solid-interface walls are totally different. Pyrolysis could lead to greater heat transfer enhancement at the bottom interface, consequently, more heat is transferred into the fluid region through the bottom interface. The dual effects of heat absorption and enhanced heat transfer caused by pyrolysis produce strong influence on the wall temperature. The mechanism of these physicochemical phenomena are also analyzed in detail, which is conducive to fundamentally understand the complicated physicochemical process of regenerative cooling. The present work has profound significance for the development of regenerative cooling technology.
Identifying Opportunities for Reducing Nacelle Drag
Authors: Zawislak M. S. , Cerantola D. J. , Birk A. M.
Published: August 2017

The accurate prediction of drag caused by bluff bodies present in aerospace applications, particularly at high angles of attack, was a challenge. An experimental and numerical investigation of a nacelle intended for fuselage-mounted aircraft engines was completed at several angles of attack between 0 and 45 deg with a Reynolds number of 6 × 105. Steady-flow simulations were conducted on hybrid grids using ANSYS Fluent 15.0 with preference given to the realizable k-ε turbulence model. Both total drag and the pressure-to-viscous drag ratio increased with angle of attack as a consequence of greater flow separation on the suction surface. Near-field and far-field drag predictions had grid uncertainties below 2.5% and were within 10% of experiment, which were less than the uncertainties of the respective force balance and outlet traverse data at all angles of attack. Regions were defined on suction-side x-pressure force plots using the validated CFD data-set that showed where and how much drag could be reduced. At 20 deg angle of attack, there was potential to reduce up to 20% drag contained within the separated flow region.
A Comparative Study of the Control Strategies for Pure Concentrated Solar Power Micro Gas Turbines
Authors: Ghavami M. , Alzaili J. , Sayma A. I.
Published: August 2017

The concept of combining small micro gas turbines with solar dish concentrator is being developed by the EU funded project OMSoP [1] to benefit from the advantages of higher efficiency, power density and reliability. This paper focuses on small units which are only powered by the solar irradiation and aims to identify suitable means of control that would minimize power output variations and achieve maximum annual generated electricity. Three different strategies have been proposed and studied in this work: power regulation control which is based on variation of the load to achieve maximum permissible power for any particular value of insolation, recuperation control which is a novel idea to partially by-pass the recuperator and use it as an additional degree of freedom in the control scheme and a hybrid control strategy which combines the first two methods. The evaluation criteria of these strategies are based on the annual generated electricity, rated generated power, solar-to-electrical efficiency and practical considerations. The performance of a 5kWe system has been calculated and compared when each of the above control strategies are applied. Quantitative and qualitative comparisons show that the recuperation control and combined methods can provide constant power output for a wide range of solar irradiation, but at the expense of reduced overall performance and additional cost and complexity. The power regulation strategy provides maximum generated electricity, but it is not suitable when the generated power by the system requires to follow the variations of the load from the consumer side.
Metamodel-Assisted Optimization of a High-Lift Low Pressure Turbine Blade
Authors: Bigoni Fabio , Maffulli Roberto , Arts Tony , Verstraete Tom
Published: August 2017

The scope of this work is to perform a single-objective optimization of the high-lift and aft-loaded T2 low pressure turbine blade profile previously designed at the von Karman Institute for Fluid Dynamics (VKI). At correct engine Mach and Reynolds numbers and for a uniform inflow at low turbulence level, a laminar separation bubble occurs in the decelerating part of the suction side.

The main goal of the optimization is to obtain a high-lift and aft-loaded blade characterized by lower aerodynamic losses with respect to the original profile.

The optimization uses a metamodel-assisted Differential Evolution algorithm, with an Ordinary Kriging metamodel performing the low-fidelity evaluations and Numeca FINE/Turbo for the high-fidelity ones.

The numerical results relative to the optimized profile are compared with those obtained for the baseline profile, in order to highlight the improvements on the blade aerodynamic performance coming from the optimization process.
Nodal Diameter-Dependent Modal Damping Method for Nonlinear Blade Dynamics Prediction Considering Variable Rotational Speed
Authors: Heinze Torsten , Panning-von Scheidt Lars , Wallaschek Jörg , Hartung Andreas
Published: August 2017

Since industrial large-scale models of friction-damped bladed disks for vibration analysis usually comprise numerous degrees of freedom, reduction techniques are required to facilitate the application of frequency and time domain solution methods. Common approaches utilize modal representations of the vibrational behavior considering either fixed, free, or hybrid interface conditions as well as elastic response to either unitary displacements or unitary forces acting on interface degrees of freedom to ensure static completeness. These modes serve as a basis for reduced description of the equation of motion. Often global damping concepts such as Rayleigh damping or hysteretic damping are applied afterwards. If mode-wise damping ratios are known, these can be introduced using modal damping formulation. Provided that variable rotational speed-dependence of the structure is of interest, an expanded speed-independent multi-model reduction basis is needed.

The aim of this paper is to provide a nodal diameter-dependent modal damping approach to account for such damping information in case of variable rotational speed. Therefore, basis transformations between surrogate and multi-model basis are required. Attention will be paid to dealing with linearly dependent bases. Periodic solutions induced by multi-harmonic excitation are sought using a harmonic balance approach. The influence of multi-harmonic excitation onto the vibrational behavior is analyzed, serving as a starting point for nodal diameter-dependent modal damping investigations. Accuracy and scope of the method are finally discussed.