bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Blade Tip Timing With Strain Gauge Data for Evaluation of Dynamic Characterization of Last Stage Blade With Interlocked Shroud for Steam Turbine
Authors: Zhang Jiamin , Shan Peng , Cheng Kai , Ye Dechao 
Published: August 2018

The tip-timing technology has been widely developed and has become an industry standard in aircraft engine and gas turbine over past decade. The main application of the tip-timing method is to verify safe operation of blades and monitor the health of blades. But tip-timing technology gets rarely used to the last stage blade of steam turbine. Particularly the blade is designed with an integral shroud, snubber and fir-tree root. The article mainly describes the process of identifying the dynamic characterization of last stage blade with an integral shroud and snubber by contactless measurements provided by tip-timing technology. Attention is focused on the comparison of tip-timing results with the results from strain gauge data.
Firstly, the frequency response of the bladed blisk is calculated by using Computer-Aided-Engineering (CAE) technologies. Secondly, according to the results of finite element modal calculation, the location of strain gauge is confirmed. The dynamic strain of blade is measured by utilizing telemetry technology. Finally, according to the design features of integral shroud, the tip-timing probe locations must be accurately confirmed in order to acquire the valid data. All probes are positioned along the radial direction of blades.
The rotating vibration test of the bladed blisk has been carried out in the high-speed test rig. In order to validate the tip-timing measurement, all the results from the tip-timing, especially the resonant frequencies and damping ratios, are compared with results from the strain gauges with which only a few blades were equipped.
Stall Warning Using the Rotor Tip Pressure in a Transonic Axial Compressor With Circumferential Grooves
Authors: Lim Byeung Jun , Park Tae Choon , Kang Young Seok 
Published: August 2018

In this study, characteristics of stall inception in a single-stage transonic axial compressor with circumferential grooves casing treatment were investigated experimentally. Additionally, the characteristic of increasing irregularity in the pressure inside circumferential grooves as the compressor approaches the stall limit was applied to the stall warning method.
Spike-type rotating stall was observed in the single-stage transonic axial compressor with smooth casing. When circumferential grooves were applied, the stall inception was suppressed and the operating point of the compressor moved to lower flow rate than the stall limit. A spike-like disturbance was developed into a rotating stall cell and then the Helmholtz perturbation was overlapped on it at N = 80%. At N = 70 %, the Helmholtz perturbation was observed first and the amplitude of the wave gradually increased as mass flow rate decreased. At N = 60%, spike type stall inceptions were observed intermittently and then developed into continuous rotating stall at lower mass flow rate.
Pressure measured at the bottom of circumferential grooves showed that the level of irregularity of pressure increased as flow rate decreased. Based on the characteristic of increasing irregularity of the pressure signals inside the circumferential grooves as stall approaches, an autocorrelation technique was applied to the stall warning. This technique could be used to provide warning against stall and estimate real-time stall margins in compressors with casing treatments.
Aerodynamic Measurements and Analysis in a First Stage Nozzle Guide Vane Passage With Combustor Liner Cooling, Slot Film Cooling and Endwall Contouring
Authors: Alqefl Mahmood H. , Kim Yong W. , Moon Hee-Koo , Zhang Luzeng , Simon Terrence W. 
Published: August 2018

Endwalls impose a challenge to cool because of the complex system of secondary flows and separation lines disrupting surface film coolant coverage. The interaction of film cooling flows with secondary flow structures is coupled. The momentum exchange of the film coolant with the mainstream affect the formation the secondary flows, which in turn affect the coolant coverage. Therefore, to develop better endwall cooling schemes, a good understanding of passage aerodynamics as affected by interactions with coolant flows is required.
This study presents experimental and computational results for cascade representing the first stage nozzle guide vane of a high-pressure gas turbine. The cascade is subsonic, linear, and stationary with an axisymmetrically-contoured endwall. Two cooling flows are simulated; upstream combustor liner coolant-in the form of an aero-thermal profile simulated in the approach flow and endwall slot film cooling, which is injected immediately upstream of the passage inlet. The experiment is run with engine representative combustor exit flow turbulence intensity and integral length scales, with high turbine passage exit Reynolds number of 1.61 × 106. Measurements are performed with various slot film cooling mass flow rate to mainstream flow rate ratios (MFR). Aerodynamic effects are documented with five-hole probe measurements at the exit plane. Varying the slot film cooling MFR results in minimal effects on total pressure loss for the range tested. Vorticity distributions show a very thin, yet intense, cross-pitch flow on the contoured endwall side. Coolant distribution fields that were previously presented for the same cascade are discussed in context of the aerodynamic measurements. A coolant vorticity parameter presenting the advective mixing of the coolant due to secondary flow vorticity is introduced. This parameter gives developers a new prospective on aerodynamic-thermal performance associated with cooled turbine endwall.
The numerical study is conducted for the same test section geometry and is run under the same conditions. The applicability of using RANS turbulence closure models for simulating this type of flow is discussed. The effects of including the combustor coolant in the approach flow is also briefly discussed in context of the numerical results.
Thermal System Optimization and Energy Grade Analysis of 700°C HUSC Steam Turbine Using a EC System
Authors: He Haiyu , Chen Tao , Fan Shiwang , Xia Xiaohua , Zhang Fang , Yu Jie , Yang Rui , Yang Jiandao 
Published: August 2018

700°C High Ultra Supercritical (HUSC) technology is taken into account as a more efficient clean coal-fired power generation technology which can achieve higher efficiency and less CO2 emission. With the increase of the main steam and reheat steam temperature, the temperature of regenerative extraction increased accordingly. This not only means higher investment cost and higher unreliability of power plant, but also leads to a great reduction of energy grade efficiency. To solve the above-mentioned problem, we introduce a novel system, called echelon cycle system (EC system). In EC system, a BEST (Backpressure Extraction Steam Turbine) is added, which provides power for feed-water pump and steam for feed-water heaters. The steam source of high temperature regenerative extractions is switched from main turbine to BEST, and the steam source of BEST is cold-reheat. Hence the highest regenerative extraction steam temperature decreased accordingly. EC system has been demonstrated to be a more efficient system by exergy theory[1] and energy grade theory.
Three types of EC system are proposed in this paper. Thermal performance calculation of these three types of EC system under rated-load condition and part-load condition is carried out to evaluate and compare the economy of system. In order to obtain a more appropriate thermodynamic system solution, safety and restriction should also be given sufficient consideration. Meanwhile, the matrix solution method for energy grade efficiency of EC system is derived in this paper. Finally, energy grade theory is used to analyze how different schemes cause different hate rate profits.
Development of a New High-Strength Steel for Low Pressure Steam Turbine End-Stage Blades
Authors: Teuber Hannes , Barnikel Jochen , Dankert Michael , David Walter , Ghicov Andrei , Voss Simon 
Published: August 2018

Influenced by the growing share of Renewable Energies, higher flexibility and increased efficiency of fossil power plants as well as improved cost efficiency in production of turbine components are evident market trends.
Daily cycling in turbine operations leads to advanced requirements for robust design especially of rotating parts. Low pressure (LP) steam turbine end-stage blades with larger exhaust areas are one lever to increase the efficiency of the turbine by reduction of exhaust losses and also to realize cost-efficient single flow exhaust applications. Consequently, blade steels with improved mechanical properties are required.
The results of the development of a new high-strength precipitation-hardening steel for LP end-stage blade application with significantly enhanced material properties are reported. The paper covers the testing strategy applied and information on crucial material parameters like improved low cycle and high cycle fatigue behavior while keeping good stress corrosion cracking resistance and corrosion fatigue properties. Furthermore, first manufacturing experiences and validation results from a full-scale component test rig are presented.
One-Dimensional Prediction and Three-Dimensional CFD Simulation of the Fluid Dynamics of Regenerative Pumps
Authors: Insinna Massimiliano , Salvadori Simone , Martelli Francesco , Peroni Giorgio , Simon Gilles , Dipace Antonio , Squarcini Raffaele 
Published: August 2018

Regenerative pumps, also referred to as “peripheral” or “side channel” pumps, are characterized by a specific speed that contextualize them between rotary positive displacement and purely radial centrifugal pumps. Although regenerative pumps are not widely distributed, they are interesting for many industrial applications. In fact, for a given flow rate they operate at lower rotational speed with respect to purely radial pumps. Furthermore, they are less affected by mechanical problems with respect to positive displacement pumps.
The energy transfer mechanism is the same of centrifugal pumps, but the presence of the side channel imposes to the fluid to pass several times through the impeller, thus obtaining higher pressure rise (as for multi-stage machines) with respect to classical purely radial pumps. Unfortunately, the complexity of the flow field, the large amount of wetted surface and a disadvantageous inflow/outflow configuration contribute to limit the maximum value of hydraulic efficiency, which is also very sensitive to the design choices.
Moreover, the intrinsic complexity of the helical flow path makes the theoretical performance estimation a challenging task. It is worth underlining that an accurate performance prediction using one-dimensional models would allow to accelerate greatly the design process, with a non-negligible reduction of demanding three-dimensional Computational Fluid Dynamics (CFD) campaigns.
The aim of the present work is to deeply investigate the fluid dynamics of regenerative pumps and to understand how accurately the fundamental physical phenomena can be reproduced by one-dimensional theory. To comply with these aims, a systematic post-processing of the results of several steady and unsteady three-dimensional CFD simulations is exploited for the validation of the in-house one-dimensional tool DART (Design and Analysis tool for Regenerative Turbomachinery), developed at the University of Florence. The theory underlying DART is detailed, and the assumptions of the model are verified by means of comparison with the numerical results underlining the key aspects to be considered for a reliable prediction of the pump performance.
Effect of Impeller Outlet Flow Affected by Casing Treatment on Rotating Stall in Vane-Less Diffuser in Centrifugal Turbomachinery
Authors: Tsukamoto Kazuhiro , Suto Shohei , Hiradate Kiyotaka , Shinkawa Yasushi 
Published: August 2018

The effect of impeller outlet flow affected by a recirculating casing treatment on rotating stall in a vane-less diffuser in centrifugal turbomachinery was investigated experimentally.
Centrifugal compressors require higher efficiency and wider operating range. At lower flow rates, rotating stall sometimes occurs in a vane-less diffuser and generates significant subsynchronous vibrations, which often mark the limit of the operating curve of actual compressors. For this reason, the vibration and load on thrust and radial bearings should be reduced when rotating stall occurs. Many studies have investigated rotating stalls in vane-less diffusers in centrifugal turbomachinery. On the other hand, few studies have investigated how stall characteristics change when a casing treatment which is an effective means of expanding the operating range of the centrifugal compressor, is implemented. From this aspect, this research experimentally investigated the effect of the impeller outlet flow on rotating stall in a vane-less diffuser and evaluated the possibility of decreasing shaft vibration.
Two different centrifugal impellers with the same recirculating casing treatment were investigated to examine the effect of the impeller outlet flow field. Impeller-A had a smaller exit blade angle with a higher deceleration ratio of impeller relative velocity from inlet to outlet. Impeller-B had a larger exit flow angle with a lower deceleration ratio. Both impellers had the same meridional geometry.
Experimental results showed that both impellers obtained map width expansions for lower flow rate regions of more than 10% from the casing treatment. In the case of Impeller-A, the static pressure rise increased as a result of the casing treatment. However, the pressure fluctuations at the diffuser due to the rotating stall increased. On the other hand, in the case of Impeller-B, the static pressure rise increased at the vane-less diffuser instead of the impeller. In Impeller-B, the casing treatment decreased the pressure fluctuation at the diffuser due to the rotating stall and kept the static pressure rise with a negative slope. The results indicate that improving the outlet flow in cases such as Impeller-B may decrease the shaft oscillations due to rotating stall.
Flow Structure and Unsteady Behavior of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor
Authors: Saito Seishiro , Yamada Kazutoyo , Furukawa Masato , Watanabe Keisuke , Matsuoka Akinori , Niwa Naoyuki 
Published: August 2018

This paper describes unsteady flow phenomena of a two-stage transonic axial compressor, especially the flow field in the first stator. The stator blade with highly loaded is likely to cause a flow separation on the hub, so-called hub-corner separation. The flow mechanism of the hub-corner separation in the first stator is investigated in detail using a large-scale detached eddy simulation (DES) conducted for its full-annulus and full-stage with approximately 4.5 hundred million computational cells. The detailed analysis of complicated flow fields in the compressor is supported by data mining techniques. The data mining techniques applied in the present study include vortex identification based on the critical point theory and topological analysis of the limiting streamline pattern.
The simulation results show that the flow field in the hub-corner separation is dominated by a tornado-type separation vortex. In the time averaged flow field, the hub-corner separation vortex rolls up from the hub wall, which is generated by the interaction between the mainstream flow, the leakage flow from the front partial clearance and the secondary flow across the blade passage toward the stator blade suction side. The hub-corner separation vortex suffers a vortex breakdown near the mid chord, where the high loss region due to the hub-corner separation expands drastically. In the rear part of the stator passage, a high loss region is migrated radially outward by the induced velocity of the hub-corner separation vortex.
The flow field in the stator is influenced by the upstream and downstream rotors, which makes it difficult to understand the unsteady effects. The unsteady flow fields are analyzed by applying the phase-locked ensemble averaging technique. It is found from the phase-locked flow fields that the wake interaction from the upstream rotor has more influence on the stator flow field than the shock wave interaction from the downstream rotor. In the unsteady flow field, a focal-type separation also emerges on the blade suction surface, but it is periodically swept away by the wake passing of the upstream rotor. The separation vortex on the hub wall connects with the one on the blade suction surface, forming an arch-like vortex.
Agile SBO Framework Exploiting Multisimulation Data: Optimising Efficiency and Stall Margin of a Transonic Compressor
Authors: Baert Lieven , Dumeunier Christophe , Leborgne Michaël , Sainvitu Caroline , Lepot Ingrid 
Published: August 2018

Turbomachinery design has become a simulation-driven process, permanently confronted to the dual need to reduce the cycle time and to further integrate complexity and multiple physics. This duality pushes towards high-dimensional design spaces and favours a multisimulation environment that assesses different operating points, different disciplines, or even different fidelity levels. To manage CPU cost, surrogate-based optimisation (SBO) has become an established approach. One of the key enablers for efficient SBO is being able to avoid the regions in the design space where simulation failures occur, and this is of a particular interest in a multisimulation environment since the failure of a single computation does not necessarily imply the systematic failing of the other computations.
The current work presents innovative auto-adaptive surrogates, exploiting a blend of interpolation/regression and classification, that have been implemented in the integrated optimisation platform Minamo. A multisimulation demonstrator, based on NASA Rotor 37, has been set up to perform an aero-mechanical multi-point optimisation. With one of the objectives of the optimisation to improve the stall margin, the aerodynamic simulations are forced to flirt with the numerical stability limits. It is shown that the introduction of different success models has a beneficial impact on the course of the multisimulation optimisation. The improved model quality, obtained by using partial information, has allowed for a more efficient search process, and at the same time a better global success rate has been obtained.
Micro Gas Turbine Cycle Humidification for Increased Flexibility: Numerical and Experimental Validation of Different Steam Injection Models
Authors: De Paepe Ward , Renzi Massimiliano , Montero Carrerro Marina , Caligiuri Carlo , Contino Francesco 
Published: August 2018

With the current shift from centralized to more decentralized power production, new opportunities arise for small-scale Combined Heat and Power (CHP) production units like micro Gas Turbines (mGTs). However, to fully embrace these opportunities, the current mGT technology has to become more flexible in terms of operation — decoupling the heat and power production in CHP mode — and in terms of fuel utilization — showing flexibility in the operation with different Lower Heating Value (LHV) fuels. Cycle humidification e.g. by performing steam injection, is a possible route to handle these problems. Current existing simulation models are able to correctly assess the impact of humidification on the cycle performance, but they fail to provide detailed information on the combustion process. To fully quantify the potential of cycle humidification, more advanced numerical models — preferably validated — are necessary. These models are not only capable of correctly predicting the cycle performance, but they can also handle the complex chemical kinetics in the combustion chamber.
In this paper, we compared and validated such a model with a typical steady-state model of the steam injected mGT cycle based on the Turbec T100. The advanced one is an in-house MATLAB® model, based on the NIST database for the characterization of the properties of the gaseous compounds with the combustion mechanisms embedded according to the Gri-MEch 3.0 library. The validation one was constructed using commercial software (Aspen® Plus), using the more advance RKS-BM property method and assuming complete combustion by using a Gibbs reactor. Both models were compared considering steam injection in the compressor outlet or in the combustion chamber, focussing only on the global cycle performance. Simulation results of the steam injection cycle fuelled with natural gas and syngas showed some differences between the two presented models (e.g. 5.9% on average for the efficiency increase over the simulated steam injection rates at nominal power output for injection in the compressor outlet); however, the general trends that could be observed are consistent. Additionally, the numerical results of the injection in the compressor outlet were also validated with steam-injection experiments in a Turbec T100, indicating that the advanced MATLAB® model overestimates the efficiency improvement by 25 % to 45 %. The results show the potential of simulating the humidified cycle using more advanced models; however, in future work, special attention should be paid to the experimental tuning of the model parameters in general and the recuperator performance in particular to allow correct assessment of the cycle performance.
Film Cooling Characteristics of a High Lift Blade Including Tip and Platform Flow Interactions
Authors: Naik S. , Lerch A. 
Published: August 2018

This paper investigates the aerodynamic and film cooling characteristics of a first stage turbine high lift blade. The blade operating conditions are representative of those normally found in a heavy-duty gas turbine. The airfoil incorporates several rows of film cooling holes located at various axial positions along the airfoil chord and the blade tip. Additionally the impact of the platform leading edge rim purge flow has been investigated and its interaction with the airfoil aerodynamic and film cooling characteristics. The film cooling holes are geometrically three-dimensional in shape, and depending on the location on the airfoil, they consist of various fan shapes, which are either compounded or in-line with the external main flow direction.
Numerical studies and experimental investigations in a linear cascade have been conducted for a range of exit Mach and Reynolds numbers. The influence and sensitivity of the coolant ejected from the airfoil, tip and the platform rim purges on the overall airfoil film cooling has been investigated for a range of operating conditions.
The measured film cooling effectiveness on the airfoil, blade tip and platform surfaces compared well with the predictions. The suction side film cooling effectiveness, which consisted of two pre-throat film rows, proved to be very effective up to the suction side trailing edge. The impact of variations in the airfoil cooling flows showed that the film cooling was relatively in-sensitive on the suction side. However, on the blade tip, it was found that the film cooling characteristics are strongly dependent on the clearances and the tip coolant ejection rate. On the platform surface, the impact of variations in the rim purge flows was evident, but proved not to alter the global film cooling characteristics on neither the airfoil nor the platform surfaces significantly.