bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a High-Pressure Hot-Corrosion Burner Rig for Testing Structural Materials Following Long Exposures to Arabian Extra Light Crude Oil Combustion Products
Authors: Saxena Saumitra , McIntosh John , Dawood Ziad , Maloney Andrew , Carolan Ronan , Mitsudharmadi Hatsari , Chen Aiping , Roberts William L. , Giri Krishna Shesha , Mohammad Bassam , Glaser Paul , Goldmeer Jeffrey 
Published: November 2019

Abstract
The use of crude oil as a backup fuel in gas turbines remains an economical option for power plants in petroleum-rich countries like Saudi Arabia. However, operating gas turbines with crude oil can corrode their Hot-Gas-Path (HGP) components due to the formation of vanadium oxides and alkali metal vanadates, when preventative measures are not employed. While the pre-combustion treatment of crude oil fuel is effective at reducing the content of sodium (Na) and potassium (K) in the fuel and, therefore, their resulting combustion products, any pre-combustion removal of vanadium has remained unviable on a commercial scale. Typically, a best practice limit of 0.5 ppmw vanadium is imposed on liquid fuels when inhibitors are not employed, and the total alkali content is limited to 1.0 ppmw. To evaluate the effects of incremental exceedances of such limits on the structural materials and coatings of gas turbines, a high-pressure hot-corrosion test rig was built at King Abdullah University of Science and Technology (KAUST). Arabian Extra Light (AXL) crude oil with a vanadium content of up to 2 ppm was chosen as the test fuel. This burner rig was designed to accommodate high temperatures (∼1173 K/ 900 °C) and the combustion of unrefined crude oils at an elevated pressure of up to 15 bar. Highly reduced flow velocities (∼1 m/s) were employed to deconvolute erosional effects from corrosion. This experiment exposed the tested materials to combustion products under these conditions for extended periods (up to 500 hours). The development of the rig included several design iterations and changes to the configuration of various sub-systems, owing to some challenges in maintaining stable combustion at low flow rates, management of coke/ash formation from the burning of crude oil, and adequate control over the pressure and temperature during extended experimental campaigns. The present publication summarizes the design and commissioning of this high-pressure hot-corrosion rig facility, and the successful demonstration of several long duration (400+ hour) experimental runs with AXL crude oil, where the environment of the sample section with test coupons was maintained at 5.5 bar and 1173 K. The pressure and temperature inside the sample section of the rig were continuously monitored. The batch of material coupons was removed from the sample section after the runs and sent for corrosion analysis. Deposits resulting from the AXL combustion and fouling were collected from several sections of the rig for analytical analysis. The fuel wash procedure, the design of components in the burner rig, and best practices of operation were also documented.
Experimental Study on the Effects of Slot Jet on Film Cooling Performance in the Cascade Endwall With Purge Flow
Authors: Yunjia Yao , Peiyuan Zhu , Zhi Tao , Liming Song , Jun Li 
Published: November 2019

Abstract
Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE‘s E3 turbine first stage stator blades is selected as the experimental reference blade type in this experiment. In the current experiment, effects of different slot locations, slot ejection angles and slot profiles on the endwall film cooling effectiveness were taken into account. Under the influence of endwall secondary flow, the film cooling is mainly concentrated on the front part of the channel and close to the suction side of the blade, while there is almost no cooling effect close to the pressure side of the blade in the channel. With the increase of the distance between the blade leading edge and the slot, the endwall film cooling performance is reduced. While the distance increasing from 0.15Cx to 0.45Cx, and the peak endwall film cooling effectiveness is reduced by 78%, 68% and 58% respectively when the mass flow ratio (MFR) is 1.0%, 1.5%, and 2.0%. As the slot ejection angle is reduced, the endwall film cooling performance can be effectively improved. When the slot ejection angle increased from 45° to 90°, the peak endwall film cooling effectiveness decreases by 17%, 15%, and 13% respectively at the mass flow ratio (MFR) = 1.0%,1.5% and 2.0%. And the convergent slot can effectively improve the endwall cooling film formed by slot jet compared to the reference slot. When the mass flow ratio are MFR = 1.0%, 1.5%, and 2.0%, the peak endwall film cooling effectiveness at the convergent slot is increased by 50%, 20%, and 15% comparing to the reference slot.
Development of a Hundreds of kWe-Class Supercritical Carbon Dioxide Power Cycle Test Loop in KIER
Authors: Choi Bongsu , Cho Junhyun , Shin Hyungki , Cho Jongjae , Roh Chulwoo , Lee Beomjoon , Lee Gilbong , Ra Ho-Sang , Baik Young-Jin 
Published: November 2019

Abstract
The supercritical carbon dioxide (S-CO2) power cycle has been a topic of interest because it exhibits a high efficiency and compact size and is compatible with any heat source. Since 2013, the Korea Institute of Energy Research (KIER) has developed three S-CO2 power cycle experimental test loops for distributed power source applications. Based on this experience, a hundreds of kWe-class dual Brayton test loop with a maximum temperature of 500 °C has been designed and partially fabricated. This cycle consists of two turbines, one compressor, two recuperators, and a flued-gas heater. First, a relatively low-temperature turbine with an inlet temperature of 392 °C was designed and manufactured as an axial impulsetype turbo-generator because of the cost and development time required for construction of a full-cycle test loop. As a preliminary step, the turbo-generator was successfully tested in 2017. Next, it was continuously operated for 4.2 h in 2018. In addition, the following components were designed and manufactured: a centrifugal compressor with a dry gas seal; oil-lubricated tilting-pad bearings; a flued-gas heater, which consists of a burner and a shell-and-tube heat exchanger; and two printed circuit heat exchanger type recuperators. The full cycle is expected to be operational in November 2019.
Techno-Economic Evaluation of the Effect of Impurities on the Performance of Supercritical CO2 Cycles
Authors: Vesely Ladislav , Dostal Vaclav , Kapat Jayanta , Vasu Subith , Martin Scott 
Published: November 2019

Abstract
The development of new power generation technologies are necessary to meet growing energy demands and emission requirements. The supercritical carbon dioxide (S-CO2) cycle is one such technology; it has relatively high efficiency, potential to enable 100% carbon capture, and compact components. The S-CO2 cycle is adaptable to almost all of the existing power producing methods including fossil, solar, and nuclear technologies. However, it is known that the best combination of the operating conditions, equipment, working fluid and cycle layout determine the maximum achievable efficiency of a cycle. Impurities in the cycle have some effect on the S-CO2 power cycle as presented in our previous work. The effect of impurities is positive or negative and affects all components. The effect of mixture compositions on the techno-economic evaluation is important information for the global understanding of the effect of mixtures on the S-CO2 power cycle. This paper focuses on the techno-economic evaluation of a hypothetical power plant with the S-CO2 power cycle. Two cases are considered for techno-economic evaluation. The difference between these cases is in the heat source and the associated heat exchanger (PCHE and shell and tube heat exchanger). Cost estimation was performed for three indicators (the levelized cost of electricity, the internal rate of return, and the net present value), which are important for economic viability and the rate of return of the project.
Experimental Investigation on the Creep and Low Cycle Fatigue Behaviors of a Serviced Turbine Blade
Authors: Li Zhenlei , Shi Duoqi , Yang Xiaoguang , Li Nina 
Published: November 2019

Abstract
This paper experimentally investigated the creep and fatigue behaviors of a low-pressure turbine (LPT) blade with 600 hours of service using a novel test system. Pure low cycle fatigue (LCF), pure creep and creep-fatigue interaction (CFI) experiments on the full-scale serviced blades were conducted respectively. Test results showed that the increasing of deformation amplitude was divided into three stages under both pure LCF and creep-fatigue loadings. The deformation of each blade increased rapidly until failure when the test cycle exceeded the 80% of their overall life under the pure LCF and CFI condition. The hold period in creep-fatigue tests shortens the first stage of whole life and has no influence on the proportion of crack initiation life to overall life. The fractures in pure LCF, pure creep and creep-fatigue tests emerged transgranular, intergranular and both transgranular and intergranular behaviors respectively. The crack initiated and propagated in a specific zone of the blade under all the experimental loadings, which limited its creep-fatigue resistance. At last, the remaining life of turbine blade was estimated conservatively by introducing the safety limit into a statistical method.
Experimental and Numerical Evaluation of Losses From Turbine Hub Clearance Flow
Authors: Uher Jan , Milcak Petr , Skach Radek , Fenderl David , Zitek Pavel , Klimko Marek 
Published: November 2019

Abstract
Long-term efforts have been made to understand loss generation and its reduction in the field of axial turbomachines. The traditional approach to losses for an isolated blade row considers the profile and the secondary losses as a result of viscous flow. The additional kinds of losses in the stage are connected with the shear stress in the mixing process. These losses result from the mixing of the main stream flow with 1) the stator leakage injected through the root axial gap and 2) the return of the tip leakage over the bucket shroud. This article focuses on the first type of mixing losses. The leakage to the main stream flow ratio and the root reaction are the two key parameters investigated in this study.
The primary data source for this study is the experiment. An experimental single stage air turbine was modified to set and precisely measure the stator leakage flow. Three configurations of the single-stage test rig with different reaction levels were tested.
The second data source for this study is CFD computation. These computations are applied to different geometries and conditions from the experiment; they are derived from real steam turbine stages designed in DSPW. The computations simulate multistage configuration and real steam is considered as the working fluid. CFD computations were performed in the commercial software ANSYS CFX. Each configuration task was computed in three iterative steps. Each step takes the distribution of the flow parameters on the boundary domains from the previous iteration. The final results from this ‘repeating boundary conditions’ approach better correspond with the real expansion in a multistage configuration.
The two data sources are not directly comparable. The experiment is used for validation of the trends. The computations provide the possibility of a multi-parametric study. The multi-parametric study is necessary to obtain a more general loss model which can be used during turbine design.
The evaluation of the experimental and numerical parts focuses on a comparison of the overall stage performance. Stage efficiency and reaction are presented in relation to the ratio between leakage and main stream flow.
Numerical Modeling of Particle Deposition in Turbine Cascade
Authors: Yang Xiaojun , Hu Yingqi , Yu Tianhao , Liu Zhigang 
Published: November 2019

Abstract
Impurities ingested in the fuel and air may deposit on the surface of turbine components during the operation of aero engines. The presence of such deposits will change the roughness of the blade surface and even seriously affect the aerodynamic performance of each turbine component and the overall safety of the engine. In this study, a new deposition prediction model was developed, which utilizes the User Defined Function (UDF) of Fluent and mesh reconstruction technique to simulate the long-term accumulation of deposition on a nozzle guide vane. Based on the critical viscosity model and the critical velocity model, considering the elasticity and viscosity of particles, some improvements to the model were proposed. The shear removal of individual particles and bulk deposits have been considered in the new deposition model. The simulation result of deposition distribution was verified by comparing with the experimental results obtained under the low temperature wax deposition. Its consistency and problems were also discussed. Subsequently, the increase of deposition thickness with time was shown. The effects of the detachment model and free flow temperature on the deposition distribution were studied. The results show that the deposition at the leading edge of turbine vanes increases fastest with time. The deposition distribution may be more accurate if the detachment model is taken into account. The amount of deposition on the vane pressure surface and stagnation line will increase with the increase of free flow temperature.
A Passive Flow Control to Mitigate the Corner Separation in an Axial Compressor by a Slotted Rotor Blade
Authors: Yoon Sungho , Ajay Rao , Chaluvadi Venkata , Michelassi Vittorio , Mallina Ramakrishna 
Published: November 2019

Abstract
The operability of the axial compressor is generally limited by endwall flows; either at the casing mainly due to the tip leakage flows or at the hub mainly due to three-dimensional corner separations. Therefore, it is crucial to improve flows near the endwalls to enhance the operability of the compressor. Based on a last-stage with cantilevered stator vanes, a small endwall slot was introduced to a rotor blade to mitigate the hub corner separation and maximize the aerodynamic operating range of axial compressors by natural aspiration.
The developed flow control technology is numerically analyzed based on the in-house High-Speed Research Compressor (HSRC) which, in turn, represents the rear stage of a modern compressor. This compressor was predicted to stall due to hub corner separation on a rotor blade based on multistage CFD analysis. A small spanwise endwall slot, connecting the pressure side and the suction side of a compressor rotor blade, was introduced near the hub to provide the by-pass flows from the pressure side to the suction side (see Figure 1). This naturally-aspirated jet significantly reduced the three-dimensional corner separation which generally occurs where the suction side meets the hub. The substantial reduction of the three-dimensional corner separation, in turn, improved the aerodynamic stall margin of the compressor. The benefit is accomplished because the low momentum region near the hub was energized due to the naturally-aspirated jet through the endwall slot and the radial migration of the low momentum flow on the suction side was significantly reduced.
A systematic parametric study was conducted to better understand the flow details and optimize the flow control without sacrificing aerodynamic efficiency. It was discovered that a very small slot, smaller than 10% of span, located near the endwall, was sufficient to have a more than 6% improvement of the stall margin with a negligible efficiency penalty (less than 0.1%). The naturally-aspirated flow through the small slot eliminates the source of the corner separation at the hub platform by strengthening the flow near the hub. This, in turn, reduces the overall aerodynamic blockage by decreasing the radial migration of the low momentum flow over a third of the span. Finally, evaluations of the mechanical strength and structural dynamics of slotted rotor blades, as well as the aerodynamic impact in a multi-stage environment were conducted and its results were discussed.
Similarity Study of Lightly Loaded Shrouded Rotors for Distributed Propulsion
Authors: Lagha Massyl , Duplaa Sébastien , Binder Nicolas , Carbonneau Xavier , Rodriguez Benoit 
Published: November 2019

Abstract
Achieving the objectives of the American and European long-term air transport in terms of emission reduction requires to shift to hybrid/electric aircraft by 2050. This implies the development of distributed propulsion systems using multiple low-diameter lightly-loaded shrouded rotors, operating at high rotational speed and moderate flight Mach number. The relevance of characteristic maps of such a propulsive system is discussed in this paper. It is based on an integrative approach, that takes advantage of the two different formalisms generally found when dealing with aeronautical propulsion : either propeller diagrams (external aerodynamics) or turbomachinery maps (internal aero-dynamics). It outlines the main parameters representing the shrouded rotors performance and the parameters that drive them in a self-similar way. This is done by dimensional analysis, taking into account the geometric and operating parameters of both the rotor and the shroud and their combined variables. The self-similarity is observed with potential flow and RANS computations, which credits the proposed formalism as a powerful tool for scaling the shrouded rotors.
Effects of Upstream Bend on Aerodynamic Performance of a Transonic Centrifugal Compressor
Authors: Yamada Kazutoyo , Furukawa Masato , Arai Hiromitsu , Ito Sasuga 
Published: November 2019

Abstract
This paper describes the influence of a bent inlet pipe installed immediately upstream of a transonic centrifugal compressor on the aerodynamic performance and the stability. In order to clarify the influence of the bent inlet pipe, the internal flow fields in the inlet pipe, the impeller, and the diffuser of the compressor have been numerically investigated by a DES (Detached Eddy Simulation). For the purpose of comparison, the simulation was also conducted for the case of uniform axial inflow using a straight pipe. In order to make clear the influence of non-uniform flow with a bent pipe as far as possible, a 90-degree bent pipe was installed immediately upstream of the compressor, that is 0.86 times the inlet inner diameter.
In the case of installing the bent pipe on the upstream of the compressor, the pressure ratio decreased on the high flow rate side in the compressor performance characteristic, whereas it increased at the low flow rate side. At the low flow rate operating point, there is a reversed flow occurring in the compressor impeller on the shroud side near the blade leading-edge. Installation of the bent pipe promotes mixing between the reversed flow and the main flow at the inlet of the compressor thanks to occurrence of a secondary flow. Since the reversed flow comes out from inside of the impeller, it has a high circumferential velocity. Therefore, the mixing of the reversed flow makes the compressor inlet flow a pre-swirl flow, and thereby the incidence decreases. As a result, leading-edge separation on the blade tip side of the impeller is suppressed, and the flow field inside the impeller is improved. In the diffuser section, when the bent pipe is installed, the circumferential velocity of the impeller exit flow increases on the hub side, whereas the radial velocity decreases. As a result, the diffuser performance is deteriorated and the diffuser stall tends to occur.
Combustion Analysis of Syngas Fuels Applied in a Micro Gas Turbine Combustor With a Rotating Casing
Authors: Ajvad Maaz , Shih Hsin-Yi 
Published: November 2019

Abstract
Combustion characteristics of a can combustor with a rotating casing for an innovative micro gas turbine have been modeled. The effects of syngas compositions and the rotating speed on the combustor performance were investigated. The effects of rotation on the combustion performance have been studied previously with methane as the fuel. This work extended the investigation for future application with syngas blended fuels. Two typical compositions of syngas were used namely: H2-rich (H2:CO=80:20, by volume) and equal molar (H2:CO=50:50). The analyses were performed with a computational model, which consists of three-dimension compressible k-ε realizable turbulent flow model and presumed probability density function for combustion process invoking a laminar flamelet assumption generated by detailed chemical kinetics from GRI 3.0. As syngas is substituted for methane at a constant fuel flow rate, the high temperature flame is stabilized along the wall of the combustor liner. With the casing rotating, pattern factor and exit temperature increase, but the lower heating value of syngas causes a power shortage. To make up the power, the fuel flow rate is raised to maintain the thermal load. Consequently, the high temperature flame is pushed downstream due to increased fuel injection velocity. NOx emission decreases as the rotational speed increases in both cases. Pattern factor decreases but exit temperature increases with the increase of roatation speed indicating a higher combustion efficiency. However, there is possible hotspots at exit due to higher pattern factor (PF>0.3) for H2-rich and equal molar syngas at lower speed of rotation, which needs to be resolved by improving the cooling strategy.
Flow Dynamics in a Multi-Swirler Model Combustor Based on LES and POD Analysis
Authors: Liu Weijie , Wang Huiru , Yang Qian , Xue Ranran , Ge Bing , Ji Yongbin 
Published: November 2019

Abstract
Swirling flow is often employed in gas turbine combustion chambers for the sake of improving flame stability. Swirling flow induces not only recirculation zones but also large coherent structures which show close relationship with flow dynamics and combustion instability. The flow dynamics including Precessing Vortex Core (PVC) in simple swirlers are extensively studied, while the flow instability characteristics in a multi-swirler combustor are not fully reported. In the present paper, Large Eddy Simulation (LES) of non-reacting turbulent swirling flow is conducted in a multi-swirler burner which comprises a pilot stage and a main stage. Flow dynamics in the multi-swirler combustor are analyzed based on phase-averaged evolution of instantaneous flowfield. Proper Orthogonal Decomposition (POD) is employed to identify the coherent structures in the multi-swirling flow. Results show that the main stage and pilot stage flow interact with each other generating highly turbulent swirling flow. PVC is successfully captured at the boundary of Main recirculation zone (MRZ) in the pilot stage with a dominant frequency of 1915 Hz. The PVC leads to periodic azimuthal flow instability. POD analyses for the velocity fields show dominant high-frequency modes (mode 1 and mode 2) in the pilot stage. However, the dominant energetic flow is damped rapidly downstream of the pilot stage that it has little effect on the main stage flow.