bluuebunny/crossref_metadata_2025_split huggingface dataset:
Louver Slot Cooling and Full-Coverage Film Cooling With a Combination Internal Coolant Supply
Authors: Click Austin , Ligrani Phillip M. , Hockensmith Maggie , Knox Joseph , Larson Chandler , Fairbanks Avery , Liberatore Federico , Patel Rajeshriben , Ho Yin-Hsiang 
Published: January 2021

Abstract
Within the present investigation, a louver slot is employed upstream of an array full coverage film cooling holes. Cooling air is supplied using a combination arrangement, with cross-flow and impingement together. The louver consists of a row of film cooling holes, contained within a specially-designed device which concentrates, and directs the coolant from a slot, so that it then advects as a layer downstream along the test surface. This louver-supplied coolant is then supplemented by coolant which emerges from different rows of downstream film cooling holes. The same coolant supply passage is employed for the louver row of holes, as well as for the film cooling holes, such that different louver and film cooling mass flow rates are set by different hole diameters for the two different types of cooling holes. The results are different from data provided by past investigations, because of the use and arrangement of the louver slot, and because of the unique coolant supply configurations. The experimental results are given for mainstream Reynolds numbers from 107000 to 114000. Full-coverage blowing ratios are constant with streamwise location along the test surface, and range from 3.68 to 5.70. Corresponding louver slot blowing ratios then range from 1.72 to 2.65. Provided are heat transfer coefficient and adiabatic effectiveness distributions, which are measured along the mainstream side of the test plate. Both types of data show less variation with streamwise development location, relative to results obtained without a louver employed, when examined at the same approximate effective blowing ratio, mainstream Reynolds number, cross flow Reynolds number, and impingement jet Reynolds number. When compared at the same effective blowing ratio or the same impingement jet Reynolds number, spanwise-averaged heat transfer coefficients are consistently lower, especially for the downstream regions of the test plate, when the louver is utilized. With the same type of comparisons, the presence of the louver slot results in significantly higher values of adiabatic film cooling effectiveness (spanwise-averaged), particularly at and near the upstream portions of the test plate. With such characteristics, dramatic increases in thermal protection are provided by the presence of the louver slot, the magnitudes of which vary with experimental condition and test surface location.
Experimental Investigation on Cooling Performance of Impingement-Effusion Full Coverage Film on Suction Surface of Vane
Authors: Zhang Fan , Liu Cunliang , Zhang Shuaiqi , Ye Lin , Li Bingran 
Published: January 2021

Abstract
To study the film cooling performance of impingement-effusion structures, it is important to study their adiabatic film cooling effectiveness. To improve the adiabatic film cooling effectiveness on a vane, some rows of cylindrical effusion holes are changed into fan-shaped holes. This experiment measured the adiabatic film cooling effectiveness of the double-walled system on the suction surface via the pressure-sensitive paint (PSP) technique. The film cooling effectiveness obtained by the PSP technique is coupled with the transient liquid crystal (TLC) technique to determine the heat transfer coefficient. This combination of techniques reduces the time required for the experiment and improves the efficiency of the experiment. The heat transfer coefficient ratio is used to evaluate the level of heating transfer. The net heat flux reduction (NHFR) is used to quantify the net benefit of film cooling. Two experimental vanes’ (A and B) film holes are both arranged in 6 rows of holes. There are 15 holes in each row. Only the positions of the fan-shaped holes are different. The experimental conditions include the mainstream Reynolds number (Re = 151,000) based on the chord length and inlet velocity, the turbulence intensities (Tu = 0.77%, 16.9%), and the mass flux ratios (ṁc/ṁg = 0.4%, 0.8%, 1.6%).
The findings show that when the mass flux ratio increases to a point, the film cooling effectiveness does not improve. Increasing the turbulence intensity leads to a decrease in the film cooling effectiveness except for the region after Row 6 on Vane B. Using the coupling of PSP and TLC to determine the heat transfer coefficient can yield credible results. The turbulence intensity and the arrangement of the film holes have obvious effects on the distribution of the heat transfer coefficient ratio. The effects of turbulence intensity, mass flux ratio and hole arrangement on NHFR were studied.
Influence of Water Addition Upstream Diffuser Inlet on Lean Blowout and Emissions in the TeLESS-II Combustor
Authors: Yang Siheng , Xu Tao , Xu Quanhong , Lin Yuzhen 
Published: January 2021

Abstract
Water is likely to be ingested into aeroengines under conditions of rainfall or hail, increasing the risk of flame blowout and posing great influence on the combustion characteristics. The chemical and thermal effects of inlet water addition on lean blowout and emissions in the TeLESS-II centrally staged LPP (Lean Premixed Prevaporized) combustor are investigated in this paper. Experiments are carried out at various conditions relevant to gas turbine combustors: the inlet temperature range is 450 K – 533 K, the inlet pressure range is 0.3 Mpa – 0.4 Mpa. The range of water mass fraction investigated is 0% – 5%. Chemical kinetics calculations are conducted to analyze the chemical effect of water addition on combustion characteristics of aviation kerosene. Time-averaged CH chemiluminescence imaging is applied to provide information of flame front and heat release. Combustion emission concentrations (CO, UHC, and NOx) are measured by a gas analyzer Based on Lefebvre’s model, an updated semi-analytical correlation is proposed to predict lean blowout limits of centrally staged combustor considering water addition. Chemical calculation results show that the addition of water leads to lower laminar flame speed and lower adiabatic flame temperature. The lower flame speed and higher flow velocity due to water injection result in higher lean blowout limits. Higher combustor inlet temperature can extend the LBO (lean blowout) limits to lower values at the same water fraction. Flame observations indicate that during the flame blowout process with the decrease of fuel flow rate, the post flame region first extinguished, and then upstream to the flame root. Flame close to the lean blowout presents a V shape and stabilizes in the recirculation zone near the nozzle. The heat release decreases with the increasing water injection. Emission results show that the water injection can reduce NOx emissions due to the thermal effects of flame temperature, while the CO, UHC emission increase on the contrary. The semi-analytical correlation to predict LBO limits shows fair agreement with experiments values at different water fractions. The prediction error compared to experiment data is within −11.3% to +12.8% in the present centrally staged combustor configuration.
The Influence of Aerodynamic/Geometric Parameters on the Performance of the TBCC Ejector Nozzle
Authors: Yang Yuming , Zhou Li , Shi Jingwei 
Published: January 2021

Abstract
TBCC ejector nozzle is the key component of the propulsion system of hypersonic vehicle to increase the thrust characteristic of the whole envelope. Aiming at the exhaust system of TBCC engine with the first stage of Ma 0 ∼ 3, the complex internal and external flow interference characteristics of TBCC ejector nozzle are analyzed and the influence of key aerodynamic and geometric parameters are studied.
1) The secondary throat produces a strong oblique shock wave in the primary flow, that reflects with the oblique shock wave at the exit of the nozzle and forms the complex flow field characteristics of the ejector nozzle.
2) The introduction of the secondary flow will not change the flow field structure of the nozzle, but can significantly reduce the intensity of shock system in the sleeve and improve the thrust performance of the nozzle; the aerodynamic throat of the primary flow appears separation because of the high pressure secondary flow, which resulting in the flow mismatching and choking of the primary nozzle.
3) Under the severe over expansion state, the thrust performance is higher when the expansion angle is reduced; The increase of the secondary throat diameter ratio can improve the over expansion state of the primary flow and increase the thrust performance; the increase of the spacing ratio causes the increase of the secondary mass rate and the decrease of the primary mass rate, but the thrust performance is less affected.
Design and Investigations on Dry Gas Seal of the Shaft End for 450MWe Supercritical Carbon Dioxide Compressor
Authors: Yuan Tao , Li Zhigang , Li Jun , Yuan Qi 
Published: January 2021

Abstract
The dry gas seal is a promising sealing technology to control the leakage flow through the clearance between the stationary and rotational components of Supercritical Carbon Dioxide (SCO2) turbomachinery. The dry gas seal is firstly designed for the SCO2 compressor shaft end of the GE’s 450MWe Brayton cycle power generation system. Then the effects of the spiral angle and gas film thickness on the designed dry gas seal performance are numerically investigated using the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulence model. The accuracy of the numerical method is validated by comparison of the previous research data done by Gabriel et al. with air as the working fluid. The Current study analyzed the sealing performance parameters of the designed dry gas seal for SCO2 compressor shaft end at five gas film thicknesses and four spiral angles. These parameters include: opening force, leakage rate, stiffness, and opening force leakage ratio. Also, the impacts of the spiral angle on flow direction in the fluid film are analyzed. The obtained results show that the designed dry gas seal meets the requirement of the leakage flow rate of the SCO2 compressor shaft end. The dry gas seal with a spiral angle of 15° is the best solution due to its low leakage rate and its’ best comprehensive sealing performance. On some occasions where high stability is required, the dry gas seal with a spiral angle of 30° can be selected due to its’ highest film stiffness. The present work provides the reference of the dry gas seal design for the SCO2 compressor shaft end.
Analysis of the Exit Flow Angle and Characteristics of Flow in Axial Turbine Cascades
Authors: Hushmandi Narmin B. , Askebjer Per , Genrup Magnus 
Published: January 2021

Abstract
Despite a wealth of sophisticated CFD-methods, most designs are still based on one-dimensional and two-dimensional inviscid analytical tools. In such methods, realistic loss and angle assessment are indeed critical in order to arrive at correct loading, flow coefficient and reaction. The selected values are normally retained through the detailed design sequence for each iteration. This means that the throat sizing and hence the gauge angle is largely based on the early design work within the through-flow environment. Even one-degree error in angle estimation will turn into a rather large capacity error. For most designs, the exchange rate between capacity and gauge angle is on the order of 3–5 percent, per degree exit angle.
In a previous publication, a methodology and equations were presented to assess the exit flow in an axial turbine blade row by Mamaev in Russian nomenclature and the tangential coordinate system. The approach, provided a unified and flow-physics based method for assessing exit angles from the geometry features like gauge angle, uncovered turning and flow features like Laval number, etc. Analysis of those formulas showed good agreement with physical flow pattern in real cascades for sub and transonic blade cascades. In this work, the same basic principal procedure is followed by employing the more international agreed nomenclature of blades such as an axial reference plane and Mach number.
In the current work, the one-dimensional analysis results were compared with the three dimensional numerical modelling of a full annulus two-stage turbine. Analysis of the results showed the inherent unsteadiness specially outside the rotor blade cascades, however, comparison of the mass averaged exit angle with the one dimensional analysis showed satisfactory agreement.
Probabilistic Fracture Mechanics for Mature Service Frame Rotors
Authors: Engels Philipp , Amann Christian , Schmitz Sebastian , Kadau Kai 
Published: January 2021

Abstract
Large gas turbine design and service business are challenged with increased demands towards flexible operations, increasing number of start-stop cycles and intermediate cycles. Probabilistic fracture mechanics (PFM) simulation design tools have matured and became robust and reliable. We present a probabilistic re-evaluation of Siemens E-class turbine disks by the combination of probabilistic two-dimensional axisymmetric part analysis of the disk and a novel probabilistic approach for the three-dimensional blade attachment. The first addresses the risk of inherent forging flaws, the latter combines the risk of surface crack initiation, growth and failure. Both models consider the heterogeneous nature of material properties, flaw geometries and detectability. These novel concepts developed at Siemens allow for an optimization of resource usage and safety, as well as the development of new service and inspection concepts for a variety of service frames and classes.
Improvement of a Tip Clearance Loss Prediction Model Based on Geometric Variation
Authors: Zhang Jiancheng , Jin Donghai , Li Zefeng , Gui Xingmin 
Published: January 2021

Abstract
Tip leakage flow is an important factor affecting the efficiency and stability of compressors. It is important to study the tip leakage flow model in the design and performance prediction process of turbomachinery. This work analyzes the existing tip clearance loss prediction model and refines it to predict the tip clearance loss considering more blade geometric parameters.
After analyzing the Yaras tip leakage loss model derivation process, it is found that the discharge coefficient (taken as constants by Yaras) will change with the gap geometry, namely, it is related to the maximum thickness and the gap size of the blade. In this paper the discharge coefficient of tip gap is revised to better predict the effect of gap loss with regard to the maximum thickness of the blade.
In this paper, the research objects are linear cascades with NACA65 profile and numerical experiments were carried out by a CFD package Numeca under the condition of Mach number equal to 0.45, where the variables are the gap sizes (1%, 2%, 3%, 4%, 6% of the axial chord length) and the maximum thickness of blades (3%, 5%, 7%, 9%, 11% of the axial chord length). Combined with the numerical calculation results, according to Yaras loss prediction formula and using the similar characteristics to the discharge coefficient of the variation trend and the Planck blackbody radiation formula, the relationship between the discharge coefficient and the maximum thickness of the blade and the tip clearance is summarized, which is integrated with the Yaras loss prediction formula to obtain the final formula. This prediction formula fits the NACA65 blade calculation fairly. The average error of 24 calculation points is 2.59%. Then the improved model was compared with several existing models. Besides the CDA062, C4 and polynomial thickness distribution blade tip clearance loss is predicted using the refined prediction formula and the biggest prediction error is 5.46%. Therefore, the improved formula still has a good prediction effect when the blade type change. It is considered that within a certain range of maximum thickness of the blade type and tip gap sizes, the improved formula can give good predictions even though the blade type is different.
Turboelectric Distributed Propulsion Modelling Accounting for Fan Boundary Layer Ingestion and Inlet Distortion
Authors: Athanasakos Georgios , Aretakis Nikolaos , Alexiou Alexios , Mathioudakis Konstantinos 
Published: January 2021

Abstract
A modelling approach of Boundary Layer Ingesting (BLI) propulsion systems is presented. Initially, a distorted compressor model is created utilizing the parallel compressor theory to estimate the impact of inlet distortion on fan performance. Next, a BLI propulsor model is developed considering both distortion effects and reduced inlet momentum drag caused from boundary layer ingestion. Finally, a Turbo-electric Distributed Propulsion (TeDP) model is set up, consisting of the BLI propulsor model, the associated turboshaft engine model and a representation of the relevant electrical system. Each model is validated through comparison with numerical and/or experimental data.
A design point calculation is carried out initially to establish propulsor key dimensions for a specified number of propulsors and assuming common inlet conditions. Parametric design point analyses are then carried out to study the influence of propulsors number and location under different inlet conditions, by varying fan design pressure ratio between 1.15 and 1.5. BLI and non BLI configurations are compared at propulsion system level to assess the BLI benefits. The results show that maximum BLI gains of 9.3% in TSFC and 4.7% in propulsive efficiency can be achieved with 16 propulsors and FPR = 1.5, compared to podded propulsors, while further benefits can be achieved by moving the propulsor array backwards in the airframe.
Fan Design Investigation on the Airbus Nautilius Engine Integration Concept
Authors: Godard Benjamin , Negulescu Camil 
Published: January 2021

Abstract
Recent innovative engine integration systems present interesting prospects for considerable aircraft fuel burn reduction. In this context, the Airbus Nautilius is a patented engine integration concept embedding two Ultra High Bypass Ratio (UHBR) turbofans at the rear of the fuselage so as to take the full benefit of the boundary layer ingestion (BLI). This concept presents very promising power savings compared to classical podded configurations when neglecting the penalty on fan performance. However, as the engine is now working in distorted boundary layer flow conditions, these benefits can be partially offset by an additional fan performance penalty. In order to assess these additional losses and therefore to refine the potential of this concept, a numerical fan design activity has been conducted by Onera on behalf of and in collaboration with Airbus. First, blade design modifications have been applied to a pre-existing UHBR fan stage originally designed for “classical” podded configurations in order to maximize the isentropic efficiency in cruise conditions. The results of this first activity shows that more than half of the fan isentropic efficiency penalty due to the distortion at the engine inlet can be recovered by few design iterations. Secondly, an operability assessment at take-off high-lift conditions has been conducted on the optimized geometry and ensures that the fan stall margin remains acceptable. In conclusion, these results confirm the initial potential and mark an additional step towards a broader assessment of the Nautilius engine integration concept, which shall be further completed by acoustic and aeroelastic studies.
On the Efficiency of a Conical Under-Platform Damper for Turbines
Authors: Denimal E. , Wong C. , Salles L. , Pesaresi L. 
Published: January 2021

Abstract
Underplatform Dampers are commonly used in aircraft engines to limit the risk of High-Cycle Fatigue of turbine blades. The latter is located in a groove between two consecutive blades. The dry friction contact interface between the damper and the blades dissipates energy and so reduces the vibration amplitudes. Two common geometries of dampers are used nowadays, namely wedge and cylindrical dampers, but their efficiency is limited when the blades have an in-phase motion (or a motion close to it), since the damper tends to have a pure rolling motion. The objective of the present study is to analyse a new damper geometry, based on a conical shape, which prevents from this pure rolling motion of the damper and ensures a high kinematic slip. The objective of this study is to demonstrate the damping efficiency of this geometry. Hence, in a first part, the kinematic slip is approximated with analytical considerations. Then, a nonlinear dynamic analysis is performed, and the damping efficiency of this new geometry is compared to the wedge and the cylindrical geometries. The results demonstrate that the conical damper has a high damping capacity and is more efficient and more robust than the two others.
Design and Experimental Characterization of a Swirl-Stabilized Combustor for Low Calorific Value Gaseous Fuels
Authors: Dybe S. , Bluemner R. , Zhang K. , Schimek S. , Duwig C. , Stathopoulos P. , Paschereit C. O. , Bartlett M. 
Published: January 2021

Abstract
Low calorific value (LCV) gaseous fuels are generated as by-products in many commercial sectors, e.g. as mine gas or bio-gas. Their efficient exploitation can be a considerable source of primary energy. Typically, product gases from biomass are characterized by low lower heating values (LHV) due to their high concentration of inert gases and steam. At the same time, their composition varies strongly based on the initial feedstock and may contain unwanted components in the form of tars and ammonia. These properties make the design of appropriate combustion systems very challenging and issues such as ignition, flame stability, emission control, and combustion efficiency must be accounted for. By employing a proprietary gas turbine burner at the TU Berlin, the combustion of an artificial LCV gas mixture at stoichiometric conditions has been successfully demonstrated for a broad range of steam content in the fuel. The current work presents the stability maps and emissions measured with the swirl-stabilized burner at premixed conditions. It was shown that the flame location and shape primarily depend on the steam content of the LCV gas. The steam content in the fuel was increased until flame blow-out occurred at LHVs well below the target condition of 2.87 MJ/kg (2.7 MJ/mN3). The exhaust gas is analyzed in terms of the pollutants NOx and CO for different fuel compositions, moisture contents, and thermal powers. Finally, OH* measurements have been carried out in the flame. A simple reactor network simulation was used to confirm the feasibility of the experimental results.