bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatio-Temporal Distribution of Soot Temperature for Flames Using Optical Pyrometry Under Unsteady Inlet Airflow Conditions
Authors: Cakmakci Arda , Knadler Michael , Lee Jong Guen
Published: September 2016

Two pyrometric tools for measuring soot temperature response in fuel-rich flames under unsteady inlet airflow conditions are developed. High-speed pyrometry using a high-speed color camera is used in producing soot temperature distributions, with its results compared with those of global soot temperature response measured using a multi-wavelength pyrometer. For the former, the pixel RGB values pertaining to respective bandwidths of red, green and blue filters are used to calculate temperature and for the latter, the emission from whole flame at 660 nm, 730 nm and 800 nm is used to measure temperature. The combustor, running on Jet-A fuel, achieves unsteady inlet airflow using a siren running at frequencies of 150 and 250 Hz and with modulation levels (RMS) 20–50% of mean velocity. Spatiotemporal response of flame temperature measured by the high speed camera is presented by phase-averaged with average subtracted images and by fast Fourier transform at the modulation frequencies of inlet velocity. Simultaneous measurement of combustor inlet air velocity and flame soot temperature using the multi-wavelength pyrometer is used in calculating the flame transfer function of flame temperature response to unsteady inlet airflow. The results of global temperature and temperature fluctuation from the 3-color pyrometer show qualitative agreement with the local temperature response measured by the high speed camera. Over the range of operating conditions employed, the overall flame temperature fluctuation increases linearly with respect to the inlet velocity fluctuation. The two-dimensional map of flame temperature under unsteady combustion determined using a high-speed digital color camera shows that the local temperature fluctuation during unsteady combustion occurs over relatively small region of flame and its level is greater (∼10–20%) than that of overall temperature fluctuation (∼1%).
Vorticity Dynamics Based Flow Diagnosis for a 1.5-Stage High Pressure Compressor With an Optimized Transonic Rotor
Authors: Chen Huanlong , Turner Mark G. , Siddappaji Kiran , Mahmood Syed Moez Hussain
Published: September 2016

This paper presents an optimized rotor as part of a 3-blade row optimization (IGV-rotor-stator) of a high-pressure compressor. It is based on modifying blade angles and advanced control of curvature of the airfoil camber line. The effects of these advanced blade techniques on the performance of the transonic 1.5-stage compressor were calculated using a 3D Navier-Stokes solver combined with a vortex/vorticity dynamics diagnosis method. The optimized rotor produces a 3-blade row efficiency improvement over the baseline of 1.45% while also improving stall margin. The throttling range of the compressor is expanded largely because the shock in the rotor tip area is further downstream than that in the baseline case at the operating point. Additionally, optimizing the 3-blade row block while only adjusting the rotor geometry ensures good matching of flow angles allowing the compressor to have more range. The flow diagnostics of the rotor blade based on vortex/vorticity dynamics indicate that the boundary-layer separation behind the shock are verified by on-wall signatures of vorticity and skin-friction vector lines. In addition, azimuthal vorticity and boundary vorticity flux (BVF) are shown to be two vital flow parameters of compressor aerodynamic performance that directly relate to the improved performance of the optimized transonic compressor blade.
The Development of a Low Specific Speed Centrifugal Compressor Research Facility
Authors: Methel Jeanne , Gooding William J. , Fabian John C. , Key Nicole L. , Whitlock Mark
Published: September 2016

To achieve aggressive specific fuel consumption goals, aircraft engines are tending toward higher overall pressure ratios and higher bypass ratios for turbofans. As sizes decrease to meet these requirements, centrifugal compressors become a viable option as the last stage of the high pressure compressor. The last stages of an axial compressor in a small core engine face reduced efficiency due to the relatively large tip clearances with respect to blade height, and therefore, it may be more appropriate to finish the final compression stage with a low specific speed centrifugal compressor.

A new facility, the Centrifugal STage for Aerodynamics Research (CSTAR) Facility, has been developed at Purdue University in cooperation with Rolls-Royce to gain further understanding of the complex aerodynamics found in such centrifugal compressors. The experimental data acquired in this facility will be utilized to develop and validate design tools for centrifugal compressors used in axial-centrifugal high-pressure compressors. The facility models the last (centrifugal) stage of an axial-centrifugal compressor and operates at engine-representative Mach numbers. In this paper, the facility is described in detail, and the baseline steady-state performance of the compressor is presented.
FlameSheet™ Combustor Engine and Rig Validation for Operational and Fuel Flexibility With Low Emissions
Authors: Stuttaford Peter , Rizkalla Hany , Oumejjoud Khalid , Demougeot Nicolas , Bosnoian Justin , Hernandez Fred , Yaquinto Matthew , Mohammed Afzal Pasha , Terrell Dwain , Weller Ryan
Published: September 2016

Flexibility is key to the future success of natural gas fired power generation. As renewable energy becomes more widely used, the need for reliable, flexible generation will increase. As such, gas turbines capable of operating efficiently and in emissions compliance from extended low load to full load will have a significant advantage. A wider range of gas fuels, including shale gas and refinery/industrial byproduct gas, is becoming increasingly available, with the opportunity to further reduce the cost of electricity. A combustion system capable of operating with wider ranges of heavy hydrocarbons, hydrogen and inerts will have an advantage to accommodate the future fuel gas trends and provide value to gas turbine operators. The FlameSheet™ combustor incorporates a novel dual zone burn system to address operational and fuel flexibility. It provides low emissions, extended turndown and fuel flexibility. FlameSheetTM is simply retrofittable into existing installed E/F-class heavy duty gas turbines and is designed to meet the energy market drivers set forth above. The operating principle of the new combustor is described, and details of a full scale high pressure rig test and engine validation program are discussed, providing insight on rig and engine emissions, as well as combustion dynamics performance. The FlameSheetTM implementation and validation results on a General Electric 7FA heavy duty gas turbine operating in a combined cycle power plant is discussed with emphasis on operational profile optimization to accommodate the heat recovery steam generator (HRSG), while substantially increasing the gas turbine normal operating load range.
Experimental Investigation of Film Cooling Effectiveness of a Highly Loaded Turbine Blade Under Steady and Periodic Unsteady Flow Conditions
Authors: Nikparto Ali , Schobeiri Meinhard T.
Published: September 2016

This paper describes the experimental investigations of film cooling effectiveness on a highly loaded low-pressure turbine blade under steady and periodic unsteady wake induced flow condition. The cascade facility in Turbomachinery Performance and Flow Research Lab (TPFL) at Texas A&M University was used to simulate the periodic unsteady flow condition inside gas turbine engines. Moving wakes that are originated from upstream stator blades are simulated inside the cascade facility by moving rods in front of the blades. The flow coefficient is maintained at 0.8 and the incoming wakes have a reduced frequency of 3.18. There are a total of 617 holes on the blade, which are distributed along 13 different rows. 6 rows cover the suction side, 6 other rows cover the pressure side and one last row feeds the leading edge. Each row has a twin row on the other side of the blade with exact same number of holes and arrangement (except for leading edge). They both are connected to the same cavity. Coolant is injected from either sides of the blade through the 6 cavities to form a uniform distribution along the span of the blade. In order to study the film cooling effectiveness under periodic unsteady flow condition, the blade surfaces were covered with Pressure Sensitive Paint (PSP) and were excited with green light. Experiments were performed for Reynolds number of 150,000 and approximate blowing ratio of coolant was maintained at one, based on equal mass flux distribution, for all rows throughout the experiments. Experimental investigations were performed to determine the effect of flow separation, and pressure gradient on film-cooling effectiveness in the absence of wakes. Moreover, the effect of impinging wakes on the overall film coverage of blade surfaces was studied.
Numerical Studies of Multi-Cycle Detonation Induced by Shock Focusing
Authors: Zhang Zhihong , Li Zhiqiang , Wu Yunke , Bao Xingdong
Published: September 2016

Shock focusing ignition techniques can avoid deflagration-to-detonation transition (DDT), which make pulse detonation engine (PDE) more efficient. Numerical simulations of an idealized pulse detonation engine consisting of axial inlet and circumferential inlet are presented in this paper. Using detailed hydrogen-air mixture chemical kinetic model, investigation on detonation direct initiation by shock focusing is done. Studies indicate that in initial static flow field, the regions of high temperature and pressure created by shock focusing can produce detonation at the condition of circumferential inlet Mach 2.4. The temperature and pressure of the focusing region is nearly 3000K and 6.3MPa. But in dynamic flow field, the high temperature and pressure created by shock wave focusing for an incident Mach number of 2.4 decrease to 1027K and 4.5MPa which cannot produce detonation. When the incident Mach number increases to 3.5, the transient temperature and pressure of the focusing region is nearly 3000K and 30MPa, which capable of initiating a detonation wave.
Experimental and Numerical Simulation of a Contact Induced Rotor/Stator Interaction Inside an Aircraft Engine High-Pressure Compressor
Authors: Batailly Alain , Agrapart Quentin , Millecamps Antoine
Published: September 2016

The development of a predictive numerical strategy for the simulation of rotor/stator interactions is a concern for several aircraft engine manufacturers. As a matter of fact, modern designs of aircraft engines feature reduced operating clearances between rotating and static components which yields more frequent structural contacts. Subsequent interaction phenomena (be it rubbing events, modal interaction or whirl motions) are not yet fully understood. For that reason, experimental data obtained from set-ups dedicated to the simulation of such interactions are scrutinized and are key in: (1) increasing the knowledge of the interaction phenomena and (2) allowing for a calibration of the numerical models with realistic events. In this contribution, the focus is made on an experimental set-up in Snecma facilities. It features a full-scale high-pressure compressor stage and aims at simulating contact induced interactions between one of the blades (slightly longer than the other ones) and the surrounding abradable coating that is deposited along the casing circumference. For this experimental set-up, it is found that the witnessed interaction involves a single blade — thus it should be analyzed as a sequence of rubbing events — and more specifically its first torsional mode, which is its second free-vibration mode. The focus is made both on the presentation of the experimental set-up and on the confrontation with the numerical results. Numerical results are analyzed by means of adaptative signal processing techniques and the consistency between numerical results and experimental observations is underlined both in time and frequency domains. In particular, the numerical strategy developed for Snecma is shown to predict very accurately the nature of the interaction as wear patterns obtained experimentally and numerically are a match. This numerical/experimental confrontation is the first attempt to calibrate a sophisticated numerical strategy with experimental data acquired within the high-pressure compressor of an aircraft engine for the simulation of rotor/stator interactions. Contrary to previous studies carried out within the low-pressure compressor of an aircraft engine, this interaction is found to be non-divergent: high amplitudes of vibration are experimentally observed and numerically predicted over a very short period of time. The ability of the numerical strategy to predict torsion induced interactions opens avenues for further analyses in turbine stages and with more sophisticated models including mistuned bladed disks and multi-stage components.
Mechanical Behavior Study of Steam Turbine Casing Bolts Under In-Service Conditions
Authors: Zhao Nailong , Wang Weizhe , Hong Hui , Adjei Richard Amankwa , Liu Yingzheng
Published: September 2016

In order to avoid the failure of bolted joints used on ultra-super critical steam turbine inner casing, their mechanical behavior should be strictly assessed, especially under the in-service conditions with steam temperature and pressure fluctuations. In this study, a 3D bolted inner casing is modeled using the commercial finite element software ABAQUS. The Norton-Bailey constitutive model and strain-life–based Manson-Coffin equation are applied to study the mechanical behavior of the bolted inner casing under in-service conditions. The results demonstrate that the inner casing could exert significant influence on the bolts by conduction, structure restriction and thermal expansion difference of the materials. The temperature and von Mises stress of the bolts experience continuous fluctuations during the steady state operation phase due to the constant variation in the steam temperature and pressure, and the alternative stresses give rise to fatigue damage of the material. The steam temperature and pressure fluctuations decline the fatigue lifetime of these high-temperature bolts in long-term operation, which should be taken into account in the design.
Experimental Study on the Effect of Diffuser Vane Setting Angle on Centrifugal Compressor Performance
Authors: Tamaki Hideaki
Published: September 2016

The effect of the diffuser vane setting angle on the performance of a centrifugal compressor was experimentally investigated. Seven different vaned diffusers were tested with the same impeller. In order to evaluate the vaned diffusers under the same flow range and diffuser inlet conditions, all the diffusers were designed to have the same throat area, the same diffuser height and the same vane inlet position. The first tests were performed by a compressor with a volute. In this case, the diffuser outlet conditions were varied along the circumferential directions due to the non-axisymmetric geometry of the volute. In the second tests, four of the seven vaned diffusers were tested using a compressor with a collector. In this case, the diffuser outlet conditions were more uniform along the circumferential directions compared to the tests using the compressor with the volute. The effect of the vane setting angle on the stage characteristics and diffuser performance as well as the effect of the circumferential distortion caused by the volute on the stage characteristics are presented. The impact of the incidence loss on the vaned diffuser performance is discussed using 1-D vaned diffuser performance modeling. Comparisons of the 1-D predictions and the tests results show the incidence loss has a strong influence on vaned diffuser performance.
Theoretical and Numerical Analysis on the Temperature Drop and Power Consumption of a Pre-Swirl System
Authors: Liu Gaowen , Wu Heng , Feng Qing , Liu Songling
Published: September 2016

As a component of delivering cooling air to turbine rotor blade at appropriate pressure, temperature and mass flow rate, pre-swirl system is very important to the cooling of turbine blades. It is attractive to the designers and scholars for its potential ability to reduce relative total temperature of cooling air as large as 100K. A pre-swirl system is actually an aero-thermodynamic system with energy transformation between work and heat. Theoretical analysis was carried out on an isentropic pre-swirl system to deduce equations for ideal temperature drop and power consumption. For an actual pre-swirl system, correlation between the actual temperature drop and power consumption was deduced, and a temperature drop effectiveness was defined also. Theoretical analysis shows that the system’s temperature drop increases linearly with the reduction of the power consumption.

Numerical models were derived from a real engine pre-swirl system with small simplification. Standard k-ε turbulence model and Frozen-Rotor approach were applied in the three dimensional steady simulations. Inlet total pressure and total temperature, outlet static pressure, mass flow rate delivered to the blade and rotating speed of rotor were kept to be fixed for all the models. The influences of heat transfer and sealing flow coming from the inner seal were ignored in the simulations. Section averaged parameters like pressure, swirl ratio and total enthalpy were presented at each typical station throughout the flow path. The relationship between the temperature drop and the power consumption of all the models has been verified to be consistent with the deduced formula. For the pre-swirl system with low radial location of nozzle, these measures, such as adding impellers in the cover-plate cavity and inclining the receiver hole, were taken to reduce the power consumption and enlarge the temperature drop obviously. For this specific pre-swirl system, models with high radial location of nozzle are more recommended to decrease the loss caused by the large circumferential velocity difference between the airflow and the rotor.
Experimental and Numerical Investigation of Effect of Center Offset Degree on Compressor Stability With Circumferential Grooved Casing Treatment
Authors: Zhang HaoGuang , Tan Feng , Wu YanHui , Chu WuLi , Wang Wei , An Kang
Published: September 2016

For compressor blade tip stall, one effective way of extending stable operating range is with the application of circumferential grooved casing treatment and its validity was proved by a lot of experimental and numerical investigations. The emphases of most circumferential grooved investigations are focused on the influence of groove depth and groove number on compressor stability, and there is few investigations dealt with the center offset degree of circumferential grooves casing treatment. Hence, an axial compressor rotor with casing treatment (CT) was investigated with experimental and numerical methods to explore the effect of center offset degree on compressor stability and performance.

In the work reported here, The center offset degree is defined as the ratio of the central difference between rotor tip axial chord and CT to the axial chord length of rotor tip. When the center of CT is located within the upstream direction of the center of rotor tip axial chord, the value of center offset degree is positive. The experimental and numerical results show that stall margin improvement gained with CT is reduced as the value of center offset degree varies from 0 to 0.33 or −0.33, and the CT with −0.33 center offset degree achieves the lowest value of stall margin improvement at 53% and 73% design rotational speed. The detailed analysis of the flow-field in compressor tip indicates that there is not positive effect made by grooves on leading edge of rotor blade tip when the value of center offset degree is −0.33. As the mass flow of compressor reduces further, tip clearance leakage flow results in the outlet blockage due to the absence of the positive action of grooves near blade tip tail when the value of center offset degree is 0.33. Blockage does not appear in rotor tip passage owing to utilizing the function of all grooves with CT of 0 center offset degree.
Tip Leakage Vortex Control in a Low Speed Axial Compressor Using Pulsed Plasma Actuation
Authors: Wu Yun , Ma Cai-dong , Tian Si-meng , Zhou You-tian , Li Jun , Li Ying-hong
Published: September 2016

Plasma actuation is a novel method for axial compressor flow control with advantages of short response time and broad frequency range. Numerical simulation of tip leakage vortex control in a low speed axial compressor with pulsed plasma actuation is performed. Millisecond pulsed dielectric barrier discharge plasma actuation with different frequencies are generated on the inner wall of compressor casing at the rotor leading edge. Scale adaptive hybrid Reynolds-averaged Navier-Stokes/large eddy simulation method based on shear stress transport turbulence model is adopted. The plasma actuation is simplified as a body force in the simulation. Results show that the frequency has a strong influence on the control effect of pulsed plasma actuation. Pulsed plasma actuation with frequency of 0.25 blade passing frequency (BPF), 0.5 BPF and 1.0 BPF extend the compressor’s stability range effectively. The mechanism is tip leakage vortex oscillation in the stream wise direction through coupling between unsteady plasma actuation and tip leakage flow. However, pulsed plasma actuation with frequency of 0.125 BPF, 2 BPF and 3 BPF fails to improve the stability range. The mechanism of pulsed plasma actuation at 2 BPF and 3 BPF is similar to that with steady plasma actuation, which is only stream wise boundary layer acceleration. The oscillation of tip leakage vortex in the stream wise direction can’t occur. For the pulsed plasma actuation at 0.125 BPF, its frequency is too low to get enough control effect.
Experimental Observations of Thermal Bow due to Natural Convection on a Gas Turbine Compressor Rotor Shaft Analogue
Authors: Smith E. O. , Neely A. J. , Butcher A. P.
Published: September 2016

This study describes the development of an experimental apparatus designed to provide initial validation of numerical simulations of a gas turbine compressor rotor shaft under thermal bow due to natural convection. The experimental analogue represents a simplified model developed by the authors in previous works, designed to represent the basic elements of a compressor rotor shaft, as part of an ongoing parametric study into the influence of compressor design and integration on the onset time, duration, and severity of thermal bow, and the propensity of an engine to suffer from the Newkirk Effect.

The semi-enclosed steel shaft, mounted on a support frame, was heated to approximately 600K in a convective oven before being removed and allowed to cool under ambient conditions. Observations of the shaft under natural cooling were made using several experimental techniques, including temperature profiling using thermographic imaging and a thermocouple array, and physical distortion measurement using linear variable displacement transducer (LVDT) probes. The behaviour of the buoyant plume was also observed using background oriented schlieren (BOS). Using these techniques, the natural convection-driven thermal gradient and resultant physical deformation were measured and recorded over a period of 60 minutes.

The observed thermal gradients and resultant thermal bow distortions were then compared to a one-way fluid thermal structural interaction (FTSI) 3D conjugate heat transfer (CHT) computational fluid dynamics (CFD) and finite element analysis (FEA) model developed by the authors, in order to validate the numerical model. The behaviour of the thermal plume from the BOS imagery was also used as a qualitative validation method. The temperature measurements and overall cooling rate measured on the experimental model showed good agreement with the numerical predictions (within 1%); however, uncertainties in the initial phase of the experiment led to error in the numerical prediction of the thermal gradient and resultant thermal bow measurements (error of up to 63%). Noting the uncertainties in the experiment, the agreement between numerical and experimental results with respect to the overall cooling rate indicates that the numerical approach being employed as part of the larger parametric study into gas turbine compressor rotor shaft thermal bow is appropriate and valid.
Towards a Flexible Immersed Boundary Method for Fluid/Structure Interactions in Turbomachinery Applications
Authors: Iaccarino Gianluca , Lee Sangjin , Kim Jungchan , Ju Youngho
Published: September 2016

The Immersed Boundary method is implemented in an unstructured-grid, compressible Reynolds averaged Navier-Stokes solver to perform fluid/structure interaction simulations in a turbo machinery configurations. The implementation enables the use of locally refined meshes and general streamlined grids to capture highly curved components and non-Cartesian configurations typical of turbomachinery components. The coupling between fluid solver and a stand-alone structure based solver is based on a fully implicit procedure and is validated by comparisons to existing results on simple rigid and deformable cylinders configurations. Initial applications of the method to aeroelastic computations of the NASA Rotor 67 configuration are also reported.
Heat Transfer of Winglet Tips in a Transonic Turbine Cascade
Authors: Zhong Fangpan , Zhou Chao , Ma H. , Zhang Q.
Published: September 2016

Understanding the heat transfer of winglet tips is crucial for their applications in high pressure turbines. The current paper investigates the heat transfer performance of three different winglet-cavity tips in a transonic turbine cascade at a tip gap of 2.1% chord. A cavity tip was studied as the baseline case. The cascade operates at engine representative conditions of an exit Mach number of 1.2 and an exit Reynolds number of 1.7×106. Transient infrared thermography technique was used to obtain the tip distributions of heat transfer coefficient for different tips in the experiment. The CFD results were validated with the measured tip heat transfer coefficients, and then used to explain the flow physics related to heat transfer. It is found that on the pressure side winglet, the flow reattaches on the top winglet surface and results in high heat transfer coefficient. On the suction side winglet, the heat transfer coefficient is low near the blade leading edge, but is higher from the mid-chord to the trailing edge. The suction side winglet pushes the tip leakage vortex further away from the blade suction surface and reduces the heat transfer coefficient from 85% to 96% span on the blade suction surface. However, the heat transfer coefficient is higher for the winglet tips from 96% span to the tip. This is because the tip leakage vortex attaches on the side surface of the suction side winglet and results in quite high heat transfer coefficient on the front protrusive part of the winglet.

The effects of relative endwall motion between the blade tip and the casing were investigated by CFD methods. The endwall motion has a significant effect on the flow physics within the tip gap and near tip region in the blade passage, thus affects the heat transfer coefficient distributions. With relative endwall motion, a scraping vortex forms inside the tip gap and near the casing, and the cavity vortex gets closer to the pressure side squealer/winglet. The tip leakage vortex in the blade passage becomes closer to the blade suction surface, resulting in an increase of the heat transfer coefficient.
Unsteady Aerodynamics of a Flat Tip and a Winglet Tip in a High-Pressure Turbine
Authors: Zhou Kai , Zhou Chao
Published: September 2016

In an unshrouded high-pressure turbine, tip leakage flow results in a loss of efficiency. In this paper, the aerodynamic performance of the tip leakage flow is investigated in a turbine stage by numerical methods. A flat tip and a closed squealer tip combined with a suction side winglet are used for the rotor tips, and the two turbines are named as ‘Flat Configuration’ and ‘Winglet Configuration’. The ability of the CFD methods in predicting the unsteady flow and the tip leakage flow is validated. The steady calculations using a mixing plane between the stator and the rotor are presented first. Then, the unsteady flows of the turbine stage with a flat rotor tip and a winglet rotor tip are simulated by solving Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations.

Compared with the ‘Flat Configuration’, the ‘Winglet Configuration’ reduces the size of the passage vortex and the tip leakage vortex. A surprising observation is that although the ‘Winglet Configuration’ reduces the size of the tip leakage vortex, its maximum swirl strength of the tip leakage vortex is about 40% higher than that for the ‘Flat Configuration’. The steady calculation shows that the entropy generation for the turbine stage is 12.1% lower with the ‘Winglet Configuration’ than that with the ‘Flat Configuration’.

The mixed-out entropy predicted in the unsteady calculation is higher than that of the steady calculation for both tips. The stator casing passage vortex has a periodic effect on the vortex near the tip gap of the rotor. The unsteady interaction of the vortices seems to be beneficial in terms of the loss. As a result, the ‘Winglet Configuration’ produces 9.4% less entropy than the ‘Flat Configuration’, which is lower than that in the case of the steady calculation.
Numerical Simulation of Ice Shedding From a Spinning Cone by Using Coupled CZM and XFEM
Authors: Fu Liang , Chen Yong , Xu Man , Wu Xianhua , Dong Wei
Published: September 2016

In turbofan engine, ice accretion on spinning cone may lead to a decline in the engine aerodynamic performance and an increase of the vibration amplitude of the engine. An understanding of the mechanisms responsible for ice shedding process is necessary in order to optimize the spinning cone design and de-icing system to avoid hazardous ice shedding. In this paper, the Cohesive Zone Method (CZM) and the eXtended Finite Element Method (XFEM) are introduced to simulate the ice shedding process from a spinning cone. The CZM is applied to simulate the initiation and propagation of ice/spinning cone interface crack. The XFEM is introduced to model crack path inside the ice. This research method could provide a reference for ice shedding analysis of other parts of aero-engine. The research result could also be used to further study on optimization of the electro-thermal and hot-air de-icing system and ice shedding trajectory and impact simulations.
Flow Control Investigations of Steady and Pulsed Jets in Bowed Compressor Cascades
Authors: Li Longting , Song Yanping , Chen Fu , Liu Huaping
Published: September 2016

Based on the previous research about the combined flow control method which was carried out by applying the endwall steady VGJ to the bowed compressor cascades to reduce the secondary flow loss, for the consideration that the pulsed jets may save the mass flow required for control, therefore the unsteady VGJs over the different actuation frequencies and blowing ratios were investigated in detail. Under the conditions of same jet geometry parameters, the improvements to the fluid fields in the bowed compressor cascades caused by the pulsed jets are less than that induced by the steady cases. With the pulsed VGJ, for the positively bowed blade, the enhancement of the time-averaged aerodynamic performance can be achieved when the blowing ratio is greater than 0.6, but all of the unsteady conditions in this research can improve the flow field in the negatively bowed blade. The time-averaged total losses decrease by 1.6% and 7.0% at most for the positively and negatively bowed blades, respectively. The mechanisms by which the endwall pulsed vortex generator jets delay flow separation and reduce loss were explored. The results show that, being different from the single vortex produced in steady VGJ, the pulsed case generates a pair of streamwise vortices with the opposite sense of rotation. One vortex suppresses the development of the secondary flow, but the other one increases the size of the passage vortex. Furthermore, for the endwall pulsed VGJ, the changes of the blowing ratio plays a more important role in improving the flow fields in the bowed cascades than that of the actuation frequency.
Experimental Investigations on Highly Loaded Compressor Airfoils With Active Flow Control Under Non-Steady Flow Conditions in a 3D-Annular Low-Speed Cascade
Authors: Brück Christian , Tiedemann Christine , Peitsch Dieter
Published: September 2016

This investigation discusses the impact of a non-steady outflow condition on the compressor stator flow in an annular cascade which is periodically chocked through a rotating disc in the wake, to simulate the expected conditions for a pulsed detonation engine (PDE). A 2D controlled diffusion airfoil of the highly loaded linear stator cascade by [1] has been transferred to the annular compressor test rig to compare results under non-steady conditions via multi-colored oil flow visualization on the suction side and pressure measurements in the wake of the blades. Three different Strouhal numbers of the choking device are investigated and analyzed by phase averaged pressure measurements downstream of the stator to visualize the unsteady flow characteristics. Triggered by the changed incidence angle due to the choking, separation on the suction side and in the hub region form a periodic event depending on the position of the blockage device. Active flow control (AFC) is implemented by means of side wall actuation at the hub to improve flow conditions. Pressure measurements show that the turning of the blades can be raised and a static pressure rise is gained by the AFC while periodic choking is active.
Heat Transfer and Fluid Flow of a Single Jet Impingement in Cross-Flow Modified by a Vortex Generator Pair
Authors: Wang Chenglong , Luo Lei , Wang Lei , Sundén Bengt
Published: September 2016

Jet impingement cooling is widely used in modern gas turbines. In the present study, both heat transfer and flow field measurements of jet impingement in cross-flow are carried out with and without a vortex generator pair (VGP). The jet and cross-flow Reynolds numbers are fixed at 15,000 and 48,000, respectively. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. Results show that the jet impingement heat transfer on the target wall is remarkably enhanced by the VGP as compared to the baseline case. The stagnation region moves upstream with improved heat transfer when the VGP is present. The flow field is measured by particle image velocimetry (PIV). The cross-flow is shown to deflect the impinging jet but the VGP reduces the streamwise momentum of the cross-flow and drives the crossflow away from the issuing jet. This leads to stronger jet impingement and thus heat transfer enhancement on the target wall.
Investigation on the Seal Structure Design and Rotor Vibration Controller for Back-to-Back Centrifugal Compressor
Authors: Li Qihang , Wang Weimin , Liu Binbin , Shao Xing , Gao Shuai
Published: September 2016

Centrifugal compressors, as the key equipment in process industries such as petroleum refinery and chemical, are faced with the challenges of rotordynamic stability and high efficiency on condition of high pressure ratio and volume flow rate. The back-to-back centrifugal compressor has a reputation of higher efficiency for its smaller balance piston drum and axial thrust bearing than those of through-in-line compressor. However, fluid non-conservation excitation forces at the balance drum seal will prominently affect the stability of rotor; there are risks of rotor-stator rubbing caused by large vibration amplitude at balance drum seal when the rotor loses stability. Aiming at this case, the patented integrated structure of balance drum seal and vibration controller was presented which combines the function of active-magnetic-bearing (AMB) and hole-pattern-seal (HPS). The feasibility of the integrated AMB-HPS was verified by ANSYS, and the effect of the diameter and depth of the hole on the performance of AMB was studied as well. A test rig was built to test the stiffness-parameters of the integrated AMB-HPS. Finally, the rotor vibration controller was investigated focusing on (1) balancing the cross couple force exerted by the seal on the rotor by the control strategy of displacement feedback, and (2) adding additional damping by the control strategy of velocity feedback. Simulation work of an industrial rotor was carried out. The results indicate that: (1) the presented seal structure can provide enough force for controlling the vibration of the rotor; (2) displacement feedback strategy has less energy consumption than the velocity feedback at the same control effect. The work of this paper can provide the foundation for the designing of new centrifugal compressors.
Optimization of Tandem Blade Based on Improved Particle Swarm Algorithm
Authors: Zhaoyun Song , Liu Bo , Xiaochen Mao , Xiaofeng Lu
Published: September 2016

To improve the design quality of high-turning tandem blade, a coupling optimization system for the shape and relative position of tandem blades was developed based on an improved particle swarm optimization algorithm and NURBS parameterization. First of all, to increase convergence speed and avoid local optima of particle swarm optimization (PSO), an improved particle swarm optimization (IPSO) is formulated based on adaptive selection of particle roles, adaptive control of parameters and population diversity control. Then experiments are carried out using test functions to illustrate the performance of IPSO and to compare IPSO with some PSOs. The comparison indicates IPSO can obtain excellent convergence speed and simultaneously keep the best reliability. In addition, the coupling optimization system is validated by optimizing a large-turning tandem blade. Optimization results illustrate IPSO can obviously increase the optimization speed and reduce the time and cost of optimization. After optimization, at design condition, the total pressure loss coefficient of the optimized blade is decreased by 40.4%, and the static pressure ratio of optimized blade is higher and the total pressure loss coefficient is smaller at all incidence angles. In addition, properly reducing the gap area of tandem blade can effectively reduce the friction loss of the blade boundary layer and the mixing loss created by mixing the gap fluid and the mainstream fluid.
Numerical Simulation on the Performance of Air-Air Primary Surface Heat Exchanger
Authors: Liu Yinze , Dong Wei , Lei Guilin , Yu Xiao
Published: September 2016

A design software was written for the air-air primary surface heat exchanger (PSHE) based on the heat balance equation and the theory of micro channel. The two different simplified models, the quarter channel and the full channel PSHE of 0° counter-flow and the model of the full channel cross-flow PSHE with cross angle of 45° under high Reynolds number are simulated. This paper presents the comparison between the results obtained by the numerical simulation at the outlet of the PSHE and the results obtained by the thermal calculation software. The results showed that the numerical simulation is consistent with the thermal calculation of the software. Compared to the PSHE of 0°, the results of PSHE with the cross angle of 45° showed that the heat transfer performance is enhanced while the pressure drop was significantly increased.
Delayed Detached-Eddy Simulations of a High Pressure Turbine Vane
Authors: Lin Dun , Su Xinrong , Yuan Xin
Published: September 2016

The flow in a generic, high-pressure turbine vane was simulated using an in-house DDES code. Two different operating conditions were simulated with one leading to a shock wave while the other does not. One case was used to validate the capability of the DDES method to capture shock waves and other flow structures using an inlet Reynolds number of 271,000 and an exit Mach number of 0.840. The test conditions for the other case were an inlet Reynolds number of 265,000 and an exit Mach number of 0.927, which is representative of a transonic, high pressure turbine vane which was used to further investigate the flow field. The DDES simulations from the first case are compared with published experimental data, RANS simulations and LES simulations. Then, DDES results for two cases with adiabatic and isothermal boundary conditions are compared. The numerical simulations with the isothermal boundary condition are further used to study the flow phenomena with wake vortices, shock waves, pressure waves, wake-shock interactions, and wake-pressure wave interactions. The effects of the pressure waves on the vane heat transfer are also analyzed.
Comparison of 2D and 3D Airfoils in Combination With Non Axisymmetric End Wall Contouring: Part 2 — Numerical Investigations
Authors: Curkovic Oliver , Zimmermann Tobias W. , Wirsum Manfred , Fowler Andrew , Patel Kush
Published: September 2016

Secondary flow phenomena have a considerable part in the efficiency loss in turbomachinery. A potential method to reduce these secondary flow losses is tangential end wall contouring inside the blade passages. The present paper is the second of two papers which investigate the impact of tangential end wall contouring on 2D and 3D airfoils compared to a baseline configuration. The first paper summarizes the experimental investigation on a 2-stage air driven turbine test rig located at the Institute of Power Plant Technology, Steam and Gas Turbines RWTH Aachen University. To enhance the impact of the tangential end wall contours (TEWC) on the near wall flow, the rotor cavities are sealed by means of combined brush- and labyrinth seals. The stator cavities are sealed by labyrinth seals, only.

This paper investigates the flow phenomena using CFD with the commercial software package ANSYS 15.0©. The brush seals are modeled by using the porous body approach and are calibrated using pressure drop measurements across the first rotor cavity. The experimental data will be presented and is used to validate the numerical model. For this, circumferential plots for the measurement planes are shown. In addition a detailed description of the changes in vortex formations as well as blade loading will be given for the various configurations. Finally a discussion of the impact on the turbine’s efficiency is given. It has been found, that for steady CFD simulations the use of stage interfaces suppresses the positive effects of the tangential end wall contour onto the downstream blade row.
Conjugate Heat Transfer Simulation of the Intercooled Compressor Vanes Based on Discontinuous Galerkin Method
Authors: Liu Long-gang , Gu Chun-wei , Ren Xiao-dong
Published: September 2016

Convective cooling channels are applied in a two-dimensional compressor vane to use the intercooling method to improve the efficiency of Brayton cycle and reduce the temperature of the vane. In this paper, we analyze the effect of coolant to the aerodynamic performance and heat transfer performance of the main stream and the vane.

For the case of a two-dimensional compressor vane NACA65-(12A2I8b)10, the vane which has five convective cooling channels has been numerically simulated in different test conditions by discontinuous Galerkin (DG) method. The coolant is supercritical carbon dioxide whose pressure is 10MPa. Conjugate heat transfer method has been used in this paper. The numerical simulation result is similar to the experiment data and has been compared with the result of the vane without cooling channels to prove the effect of cooling channels. Cooling channels have large effect on the distribution of temperature and heat transfer coefficient. In addition, the relationship between Nu and Re on the fluid-solid interface has been analyzed and a suitable empirical equation has been obtained.

This work analyzes the effect of intercooling system in the compressor and give several advice on future engineering applications in aero engines and gas turbines.
Conjugate Heat Transfer Analysis of a Blade Leading Edge Cooling Configuration Using Double Swirl Chambers
Authors: Kusterer Karsten , Bühler Peter , Lin Gang , Sugimoto Takao , Bohn Dieter , Tanaka Ryozo , Kazari Masahide
Published: September 2016

The efforts to improve the process efficiency of modern gas turbines usually lead to competing objectives for the design of the cooling system as turbine inlet temperatures are continuously increased. Typically, the designer of modern cooling systems is confronted with the requirement to achieve a wall temperature below the maximum allowable wall temperature which is fixed by the material and life span requirements. Simultaneously, a homogenous temperature distribution is desired in order to reduce thermal stresses due to temperature gradients. To maximize cycle efficiency, all this should be achieved by minimizing the necessary cooling air consumption. The Double Swirl Chamber (DSC) cooling technology is a promising configuration to satisfy these design requirements combined. The DSC cooling technology is an advanced kind of internal cooling passage which is created by the merging of two standard single swirl chambers. In the DSC cooling configuration, two anti-rotating large scale swirls are generated which enhance the mixing of the cooling air. This leads subsequently to an increased internal heat exchange. Additionally, the recurring reattachment of the swirl flows at the center of the chamber leads to a linear impingement effect due to local velocity elevations which makes the DSC configuration very suitable for an effective and uniform cooling of thermally high loaded blade leading edges as turbine inlet temperatures are further increased. Thus, the DSC cooling technology has great potential to lengthen the life span of gas turbine blading. In the present work, two DSC configurations are compared numerically to the state-of-the-art leading edge impingement cooling technology with a conjugate heat transfer approach of a simplified blade leading edge geometry. The two investigated DSC are similar, but with the second one being slightly modified in its geometry in order to ease the manufacturing process. With the same numerical setup in terms of applied boundary conditions and under consideration of Reynolds similarity, the DSC configurations show a local temperature reduction of 1.0–1.3% of the turbine inlet temperature in comparison to the impingement cooling case. The total pressure drop in the DSC configurations is in the same range as in the impingement cooling configuration and even slightly decreased by 0.15–0.20%. The heat transfer is 12–16.2% higher in the DSC configurations, which shows the potential for improving the internal cooling performance of a system by the application of the DSC cooling technology in real engine conditions.