Fast Flux Research Articles

Hydrophilic and underwater superoleophobic porous graphitic carbon nitride (g-C3N4) membranes with photo-Fenton self-cleaning ability for efficient oil/water separation

Due to the great fouling resistance property, (super)hydrophilic/underwater superoleophobic membranes are prevalent candidates for oil-polluted wastewater treatment. Even so, membrane fouling inevitably occurs during long-term operation. Therefore, it is of great significance to construct anti-fouling membranes with robust flux recovery. Herein, a polyvinyl pyrrolidone (PVP) coated porous potassium-doped g-C3N4 (PKCN) membrane was fabricated for the first time by vacuum filtration. The as-prepared membrane displays enhanced hydrophilicity and underwater superoleophobicity. The permeability of the membrane increased significantly after sonication treatment, which is attributed to the increased pore volume and small nanosheets size that shorten the transport pathway of water molecules. Importantly, owing to the high photo-Fenton activity, the PKCN membrane exhibits fast (within 15 min) and excellent flux recovery (96.5%) after the photo-Fenton cleaning process. Furthermore, after 10 repeated usages, the PKCN membrane still keeps stable permeability and excellent purification efficiency. This work opens a door for developing self-cleaning membranes with the superior anti-fouling ability for effective oil/water separation.

Investigation on the Tritium Self-Sufficiency and Neutron Shielding Based on a Water-Cooled Blanket for CFETR at 1.5 GW

China Fusion Engineering Test Reactor (CFETR) is a new test tokamak device in China, which is to bridge the scientific and technical gaps between ITER and DEMO. One of the main missions of CFETR is to achieve tritium self-sufficiency with a tritium breeding ratio (TBR) of no less than 1.05. In addition, the neutron shielding evaluation is also a significant issue, which could provide a significant reference for the water-cooled ceramic breeder (WCCB) blanket modification and improvements. In this work, a 3-D simplified neutronics model containing the WCCB blanket is developed and the neutronics performance is calculated based on the 1.5 GW fusion power. The nuclear analyses are carried out by the Monte Carlo N-particle (MCNP) transport code, including the TBR, neutron wall loading (NWL), fast neutron flux on inboard side, and nuclear heating deposition on main in-vessel components. It is found that the net TBR reaches 1.23, which meets the condition of tritium self-sufficiency. Moreover, it is found that the peak NWL of inboard and outboard occurs in the equatorial plane. The inboard peak NWL is 1.89 MW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the outboard peak NWL is 1.97 MW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In addition, the fast neutron flux and nuclear heating deposition at the inboard midplane in toroidal field coil (TFC) are obtained. According to the radiation limits of the CFETR TFC referring to ITER, the results show the nuclear responses of the TFC meet the limit criteria.

Neutron spectrum determination of accelerator-driven d(10)+Be neutron source using the multi-foil activation technique

New neutron field of the compact accelerator-driven fast neutron source based on the cyclotron and beryllium target station was studied and developed at the NPI CAS. Neutrons were generated using the deuteron bombardment on 8 mm thick beryllium layer by the 10.3 MeV deuteron beam. Broad neutron energy spectra of the d(10)+Be source reaction at two source-to-sample distances (14 mm and 154 mm) were determined for the first time at the NPI. Sets of eight activation materials comprising Au, Co, Ti, In, Al, Fe, Ni, and Nb were irradiated in the d(10)+Be neutron field, and activated dosimetry foils were analysed using the nuclear gamma-spectroscopy technique (HPGe detector) and reaction rates were measured. Neutron energy spectra of the d + Be source reaction for 10.3 MeV deuterons were reconstructed employing the modified version of the SAND-II unfolding code. For 9.7 μA deuteron beam, the fast neutron flux of developed d(10)+Be neutron field reached the value of 1.4 × 1010 cm−2s−1 at a distance of 14 mm from the source target and 4.1 × 108 cm−2s−1 at a distance of 154 mm. The novel d(10)+Be neutron field with energy range up to 15 MeV is convenient for neutron cross-section data validation, experimental simulation of the fast neutron spectrum of experimental nuclear reactors, applications of neutron activation analysis, and radiation hardness tests of materials important for nuclear energetics.

Thermal-hydraulic transient analysis of the FFTF LOFWOS Test #13

In the framework of a Coordinate Research Project (CRP) endorsed by the International Atomic Energy Agency (IAEA), the Department of Astronautical, Electrical and Energy Engineering (DIAEE) of Sapienza University of Rome has developed a thermal–hydraulic model of the Fast Flux Test Facility (FFTF). FFTF was a Sodium-cooled Fast Reactor (SFR) developed by the Westinghouse Electric Corporation for the U.S. Department of Energy, which operated from 1980 to 1992. The main mission of the reactor was to prove feasibility and operation of SFR nuclear power plants. For this purpose, FFTF was designed as a flexible system and extensively instrumented, making it attractive for code validation purposes. The proposed benchmark exercise involves a Loss Of Flow Without Scram (LOFWOS) test, performed in 1986. DIAEE has developed and is validating a multiphysics modelling based on a Neutron-Kinetic/Thermal-Hydraulic (NK/TH) coupling approach with RELAP5-3D© and PHISICS codes. The present paper deals with the assessment of the standalone TH modelling, establishing the basis for the next NK/TH phase. Steady-state results have been compared with benchmark specifications, proving the adequacy of the model calibration. After that, the comparison between transient simulation and experimental data has highlighted an overall good agreement, demonstrating the capability of the developed TH nodalization to reproduce the FFTF LOFWOS Test #13. Outside of the parameters selected for the comparison in the benchmark exercise, outlet plenum thermal stratification and sodium free surface motion within Gas Expansion Modules (GEM) have been analysed, providing useful outcomes for the understanding of the transient event and for future perspectives.

Transient analysis of the main heat-transfer system of the pool-type sodium-cooled fast reactor

<p indent="0mm">Sodium-cooled fast reactors are the first choice of the fourth generation of advanced nuclear energy systems. They have attracted significant attention in the development of advanced nuclear energy technology owing to their advantages of proliferative nuclear fuel, transmutation of radioactive waste, and high thermal efficiency power generation. The design and construction of the secondary sodium-cooled fast reactor are ongoing in China. The physical characteristics of fast neutrons and the special thermal, physical, and chemical properties of liquid sodium metal cause special and complex scientific problems in the design of sodium-cooled fast reactors. In this study, taking the energy transfer process of sodium-cooled fast reactors as the object, we establish mathematical and physical models for analyzing large-scale transients in various energy transfer and conversion processes. The model is verified and validated by the natural circulation test of the Phoenix reactor and the international benchmark of the fast flux test facility loss in flow tests. The trend of the calculated values is consistent with that of the test data, and the results are in good agreement. For a typical pool-type sodium-cooled fast reactor, four types of transient events in the power plant are determined by engineering evaluation and deductive analysis. Among them, there are nine normal operation transients, 23 expected transients, 10 abnormal transients, and 7 emergency transients. Based on the established mathematical and physical models, the analysis results of each type of typical transient are given, which provide an important basis for the design of the system and equipment/components and lay a scientific and technological foundation for completing the design of the transient condition and operation mode of the sodium-cooled fast reactor as well as safety evaluation.

Accelerated sediment phosphorus release in Lake Erie's central basin during seasonal anoxia

AbstractEutrophication remains a serious threat to Lake Erie and has accelerated over past decades due to human activity in the watershed. Internal phosphorus (P) loading from lake sediment contributes to eutrophication, but our understanding of this process in Lake Erie is more uncertain than for its riverine P inputs. Past study has focused on incubating sediment cores in oxic or anoxic conditions, meaning we know little about sediment flux during state transitions. We used 56 controlled sediment core incubation experiments to quantify rates and onset of P release in Lake Erie's central basin as a function of depositional environment, season (spring, summer, and fall), temperature, and dissolved oxygen (DO) concentration. P flux under oxic or hypoxic (&gt; 0 to ≤ 2 mg L−1 DO) conditions was slow (0.31–0.50 mg m−2 d−1) compared to anoxic P flux (5.19–30.7 mg m−2 d−1). The transition between slow and fast flux occurred within 24 h of anoxia (0 mg L−1 DO). Oxic or anoxic P flux was generally similar across seasons and incubation temperatures (8°C and 14°C). In 14°C incubated cores anoxic P flux onset was earliest in fall, when sediments had already been exposed to anoxic conditions in the lake. Re‐oxygenation of experimental cores that temporarily developed anoxia reversed the direction of P flux, but P release resumed at similar rates once the water returned to anoxia. Understanding the effects of hypolimnion oxygen conditions on internal P loading allows us to better constrain nutrients sources and implications for P budget management.

PASSVM: A highly accurate fast flux detection system

Fast Flux service networks (FFSNs) are used by adversaries to provide high availability to malicious servers while keeping them hidden from direct access. In these networks, a large number of botnet machines work as proxies to relay the traffic between end users and a malicious mothership server which is controlled by an adversary. Various mechanisms have been proposed for detecting FFSNs. However, most of these mechanisms depend on collecting a large amount of DNS traffic traces and require a considerable amount of time to identify fast flux domains. In this paper, we propose an efficient AI-based online fast flux detection system that performs highly accurate and extremely fast detection of fast flux domains. The proposed system, called PASSVM, is based on features that are associated with DNS response messages of a given domain name. The approach relies on features that are stored in local databases, in addition to features that are extracted from the response DNS messages. The information in the databases are obtained from Censys search engine and an IP Geolocation service. PASSVM is evaluated using three types of supervised machine learning algorithms which are: Multilayer Perceptron (MLP), Radial Basis Function Network (RBF), and Support Vector Machines (SVM). Results show that SVM with RBF kernel outperformed the other two methods with an accuracy of 99.557% and a detection time of less than 18 ms.

Initial demonstration of automated fuel performance modeling with 1977 EBR-II metallic fuel pins using BISON code with FIPD and IMIS databases

Using the BISON fuel performance code, simulations were conducted using an automated process to read initial and operating conditions from the Fuels Irradiation and Physics Database (FIPD) and Integral Fast Reactor materials information system (IMIS) database, which contains metallic fuel data from the Experimental Breeder Reactor-II (EBR-II). This work demonstrates use of an integrated framework to access the vast majority of EBR-II experimental fuel pin data to support rapid development of fuel performance models for next-generation metallic fuel systems. With this capability, validation for fuel qualification can be performed rapidly. Between IMIS and FIPD, there is enough information to conduct 1977 unique EBR-II metallic fuel pin histories from 24 different experiments, at varying levels of detail between the two databases. Each of these histories includes a high-resolution power history, flux history, coolant channel flow rates, and coolant channel temperatures. Fission gas release (FGR), cumulative damage fraction (CDF), fuel axial swelling, cladding profilometry, and burnup were all simulated in BISON. The results were compared to post-irradiation examination (PIE) results for the initial demonstration of automated BISON modeling. BISON simulations conducted with IMIS and FIPD were in rough agreement with PIE measurements and calculations. Cladding profilometry, FGR, and fuel axial swelling were found to be in rough agreement with PIE measurements, depending on the physics used within the BISON input files. The mechanical contact solver chosen was found to significantly impact axial fuel swelling and cladding strain predictions. CDF values were assessed to see whether pin failure may have been predicted (CDF ≥ 1). This work suggests that continued development of an automated tool for BISON should focus on inclusion of the Fast Flux Test Facility (FFTF) experimental data for a larger database for metallic fuel, improved physical models to better capture fuel performance, such as fuel-cladding interactions, and a more detailed comparison with available PIE data to further the BISON model development.

Validation of TRACE capability to simulate unprotected transients in Sodium Fast Reactor using FFTF LOFWST Test #13

The US NRC system code TRACE has been modified at PSI for application to liquid- metal-cooled reactor. An unprotected loss-of-flow-without-scram test performed at the Fast Flux Test Facility (FFTF) provides an opportunity to enhance the validation base of TRACE to transient analysis for sodium-cooled fast reactor (SFR). The FFTF primary system model was created with TRACE and initial core flow distribution and pressure drop in each segment of primary loop were reproduced using available data. In addition, a full-core model was built with the Serpent-2 Monte Carlo code to compute reactivity feedback parameters and delayed neutron information for point kinetics model in TRACE. Transient movement of sodium free level in Gas Expansion Modules (GEM) which was designed as a passive safety device of FFTF was simulated with TRACE using a level tracking model. A good agreement between measured and calculated total reactivity indicated a reasonable validity of modeling of feedback effects and of predicted sodium level in GEM. Multi-dimensional thermal-hydraulics effects in the FFTF vessel especially thermal stratification phenomenon which was directly related to natural circulation flow rate in primary loop were simulated with three three-dimensional VESSEL components in TRACE. Transient evolution of sodium temperatures at the Post-Irradiation Open Test Assembly (PIOTA) outlet was predicted in a good agreement with the measurements. The need of a more accurate thermal–hydraulic simulation of the inter-assembly gaps corresponding to the fuel region was discovered to obviously improve the estimation of inter-assembly heat transfer. This study represented an important step towards the validation of the TRACE code to SFR and some suggestions for further development work are proposed.

Fast Flux and Torque Control of a Double Inverter-Fed Wound Machine Considering All Coupling Interferences

For efficient operation of the squirrel cage induction motor, the flux must be properly adjusted according to the torque. However, in such variable flux operation, the performance of torque control is limited by the flux control because it is not possible to measure and control the rotor current that affects the flux. On the contrary, in a double inverter-fed wound machine (DIFWM), the inverter is connected to the rotor side, as well as the stator side, and the rotor current can be controlled. This controllability of the rotor currents improves the operation performance of a DIFWM. This article presents the decoupling current control method of a DIFWM for fast flux and torque control. Since the rotor flux is directly calculated by the stator and rotor currents, the bandwidth of the flux control can be improved to the bandwidth of the current controller, which means that the torque control also has the same bandwidth. In this article, a detailed current controller design method with a DIFWM feed-forwarding decoupling method to eliminate all coupling interferences is proposed. The simulation and experimental results regarding the DIFWM are presented to verify the torque and flux control performance of the proposed control method.

The dependency of fast neutron flux and spectra on the collimation-field size and geometry for fast neutron therapy purposes

The aim of this work is to optimize and investigate the relationship between the collimation-filed size and their geometries and the fast-neutron intensity and their energy-spectrum. Advantageously for these purposes, a prototype of collimator was designed and constructed to simulate different geometrical and materials compositions. Beams of fast neutrons generated by the reaction 9Be(d, n) with 13.6 MeV deuteron energy were investigated. The average energy of the emitted neutrons is about 6–7 MeV. The maximum intensity was at neutron energy of 4–5 MeV. In the process of the study, experimental works were carried out with Al, Fe, Cu and Cd foils which positioned on the collimator aperture as neutron detectors. The neutron activation method and Gamma-spectrometer were deployed to determine the neutron intensities within the energy-range from thermal energies to 14 MeV. Experiments were conducted for ten different combinations of materials and geometries which can be adjusted by the removable-polyethylene collimator parts and the metal parts. It was concluded that the thermal and fast neutron flux were depended on the collimation-field size and materials, where the fast neutron flux output was about 100% more for bigger collimator 9 × 9 cm2 comparing with the smaller ones 5 × 5 cm2 . And more than 60% in case of adding Lead layers into the collimator. These results could have influential implications on the fast neutron intensities and improvement of collimation systems for fast neutron therapy. Also, it could enhance the irradiation fluxes in the irradiation channels in nuclear reactors for medical isotopes productions and material testing and other applications.

Durable and super-hydrophilic/underwater super-oleophobic two-dimensional MXene composite lamellar membrane with photocatalytic self-cleaning property for efficient oil/water separation in harsh environments

Super-wetting membranes with outstanding permeation and anti-fouling performance are promising candidates for highly-efficient oily wastewater treatment. Herein, we designed a facile strategy to fabricate the super-hydrophilic/underwater super-oleophobic two-dimensional MXene-based composite membrane via vacuum-assisted self-assembly of two-dimensional MXene nanosheets on porous polyvinylidene fluoride (PVDF) substrate and in situ mineralization of photocatalyst β-FeOOH on the membrane surface. Benefiting from the inherent super-wettability and regulated lamellar structure (Short transport pathway and abundant nanochannels), the resultant MXene-based composite membrane displayed fast permeation flux (500.38–1022.7 L m−2 h−1) and favorable separation efficiency (99.32–99.72%) for a series of micro-scaled oil-in-water emulsions. Importantly, the excellent photo-induced self-cleaning capability and low oil-adhesion contributed to the high anti-fouling resistance, outstanding reusability, and durability of 2D MXene composite membrane. Moreover, the 2D MXene composite membrane exhibited superior chemical stability, which enabled it to maintain highly efficient oil/water separation performance in high-temperature, high salty, and strongly corrosive conditions. This work provides a feasible route to fabricate durable super-wetting 2D membranes with photo-Fenton self-cleaning capability for the oily wastewater treatment in harsh environments.

Fullerite Nano-materials as a Moderator in Neutron Irradiators with Radium Sources: Feasibility and Advantages

Abstract: In this study, the feasibility of using fullerite nano-materials as a moderator in 226Ra-Be neutron irradiators has been theoretically investigated, for the first time. Thermal, intermediate and rapid neutron flux in irradiation channels was calculated using the MCNP5 code when a fullerite nano-material was used as a moderator. The simulation results were then compared with other simulation results performed when paraffin was used as a moderator. The comparison showed that using fullerite instead of paraffin as a moderator results in an increase in the total number of irradiation neutrons by more than twice in average (240 %) for each direction inside the irradiator. This increase is distributed as follows: 27.84 %, 87.84 % and 124.32 % thermal, intermediate and rapid neutrons, respectively. The previous distribution indicates a significant increase in the intermediate and fast neutron flux. This is considered as an additional advantage of using the 226Ra-Be neutron irradiator with a fullerite moderator. The irradiator can then be used not only to irradiate the materials whose irradiation requires thermal neutrons, but also those that require medium- to high-energy neutrons. Keywords: Neutronic irradiator, Ra-Be radiation source, Cadmium, Neutron flux, MCNP5-beta code. PACS: Neutrons diffusion and moderation, 28.20.Gd, Moderators (nuclear reactors), 28.41.Pa.

Photocatalytic GO/M88A “interceptor plate” assembled nanofibrous membrane with photo-Fenton self-cleaning performance for oil/water emulsion separation

Developing the high-efficient and robust antifouling membranes for oily emulsions to achieve the purpose of prolonging the service life of the membrane shows great demand because of the restriction of hydration anti-fouling mechanism strategy to against pollution. Herein, a hydrophilic photo-Fenton-like catalyst – GO/Fe-MOF assembled stabilized polyacrylonitrile (SPAN) nanofibrous membrane with underwater superoleophobicity, robust mechanical strength and photo-Fenton self-cleaning performance was firstly designed and fabricated via ultrasonic assistance, mussel-inspired fixation and low temperature hydrothermal synthesis methods. In this work, benefiting by the regulable amounts of GO nanosheets on the SPAN@GO/M88A membrane surface, the obtained membrane possessed sub-micrometer skin layer, which guarantees the balance of fast permeation flux (920–7083 ± 47 L m−2 h−1) and separation efficiency (>99.2%) for diesel/water emulsion with small emulsified oils. Moreover, introduced hydrophilic Metal-organic frame nanoparticles (MIL-88A (Fe)) into modified membrane endowed underwater anti-oil-fouling and photo-Fenton catalytic degradation performance for organic contaminants. Meanwhile, the charged GO/M88A heterostructure can assist to achieve demulsification for separation of surfactant-stabilized emulsions by strong electrostatic force. More importantly, attached and irremovable contaminants on the membrane can be quickly removed by photo-Fenton self-cleaning method, and achieved over 96% of recovery flux recovery ratio, which effectively prolonged the service life of the membrane. We believe the newly designed SPAN@GO/M88A membrane with hydration antifouling and photo-Fenton self-cleaning properties can stimulate more studies on revivable separation membranes for multifunctional applications.

Machine learning application to single channel design of molten salt reactor

This study proposes a robust approach to quickly design a nuclear reactor core and explores the best performing machine learning (ML) technique for predicting feature parameters of the core. We implemented the approach into a hypothetical channel of molten salt reactors to demonstrate the applicability of the method. We prepared a Python tool, named Plankton, which couples to a reactor physics code and an optimization tool, and imports ML methods. The tool performs three consecutive phases: reactor database generation, machine learning application, and design optimization. We identified the extra trees method as the best performing estimator. With the estimator, we found nine optimum designs in total, one for each fuel-salt pair, and estimated all the performance metrics of the designs with a <5% prediction error compared to their actual values. U-Pu-NaCl fuel-salt gave promising results with the highest conversion ratio, the most negative feedback coefficient, and the lowest fast flux.

Rational Identification of Doping Strategy to Achieve a Highly Conductive and Reliable Protonic Electrolyte for Electrochemical Cells

While protonic ceramics are being utilized as electrolyte materials in electrochemical cells for hydrogen or electricity production, the higher proton conductivity and chemical stability under realistic operating conditions are required to deliver fast proton flux. For widely used Y or/and Yb doped Ba(Ce,Zr)O3 electrolytes, there are still some concerns with indistinct doping mechanism and uncertain element precipitation problem during sintering, which raise practical problem on electrolyte selection. In this work, the strategy of single element doping and co-element doping has been investigated to understand how they behave differently in proton conductivity and chemical instability. Three compositions, BaCe0.4Zr0.4Y0.2O3-δ, BaCe0.4Zr0.4Yb0.2O3-δ and BaCe0.4Zr0.4Y0.1Yb0.1O3-δ, are chosen to study the overall conductivity as function of B-site environment and gas conditions to provide experimental evidences for composition optimization. More importantly, the Y or/and Yb precipitation in each composition under various sintering conditions is extensively studied to explore the safe window for sintering the electrolyte with minimal element diffusion. In addition, the diffusion of nickel element into the electrolyte grain is also studied to understand the detrimental effects on grain boundary conductivity and consequently the electrochemical performance in the cells. This study will provide some insights into protonic electrolyte selection based on technical considerations on both excellence and stability.

Perovskite oxide and polyazulene–based heterostructure for high–performance supercapacitors

AbstractSeveral types of electrode materials have been developed for high–performance supercapacitors. Most of the relevant studies have focused on the discovery of new atomic structures and paid limited attention to the effect of heterostructures in supercapacitor electrodes, which has long hindered the fundamental understanding of the use of hybrid materials in supercapacitors. In this study, a novel heterostructure based on perovskite oxide (LaNiO3) nanosheets and polyazulene was synthesized. The as–prepared heterostructure–based supercapacitor exhibited a specific capacitance of up to 464 F g−1 at a high current density of 2 A g−1 in 1–ethyl–3–methylimidazolium tetrafluoroborate. In a symmetric supercapacitor, this heterostructure delivered an energy density of up to 56.4 Wh kg−1 at a power density of 1100 W kg−1. Both LaNiO3 and polyazulene contributed pseudocapacitance and dominated the performance. Unexpectedly, electric double–layer capacitance was found to contribute in this system. Density functional theory calculations indicated that the advantage of the high electrical conductivity of the heterostructure benefited the supercapacitor operation. Electrochemical quartz crystal microbalance analysis revealed that the fast ion flux and adsorption boosted performance. The high intrinsic electrical conductivity and improved stability make this heterostructure a promising electrode material candidate for supercapacitors.

Neutron guide optimization for the Moroccan PGAA system

The Moroccan TRIGA Mark II research reactor is to be equipped with a PGAA (Prompt Gamma Activation Analysis) facility to assist the country's progression in socioeconomic areas such as the environment and geochemistry, agriculture, health, industry, cultural heritage, and human sciences. The requirements of the PGAA facility include a very high thermal to fast neutron flux ratio and a focused, thin beam. Supermirror neutron guides are generally used to meet such requirements due to their ability to reflect neutrons with a specific energy and scattering angle. This study was undertaken to determine a suitable neutron guide for achieving optimal performance for the PGAA facility, where such a determination needs to be made according to both the available space and the minimum performance needed for PGAA analysis. To better parameterize the neutron guide, a set of simulations were performed with the aim of establishing the best guide specifications. Three types of neutron guides were studied, namely straight, curved, and bender. McStas code was used in this study, and the simulations showed that the guides must be 6 m long and that the coating value m must be equal to 5 for the bender and straight guides and 6 for the curved guide. Among the three guide types, the thermal/epithermal (Фth/Фep) and thermal/fast (Фth/Фfast) ratios were found to be much better when using the curved guide.

PHANTOM COOLING EFFECTS ON ROTOR BLADE SURFACE HEAT FLUX IN A TRANSONIC FULL SCALE 1+1/2 STAGE ROTATING TURBINE

Abstract An experimental and numerical investigation of phantom cooling effects on cooled and uncooled rotating high pressure turbine blades in a full scale 1+1/2 stage turbine test is carried out. Objectives set to capture, separate, and quantify the effects of upstream vane film-cooling and leakage flows on the downstream rotor blade surface heat flux. Multiple series of tests were carried out in the Air Force Research Laboratory, Turbine Research Facility, at Wright-Patterson Air Force Base, Ohio. A non-proprietary research turbine test article is uniquely instrumented with high frequency double-sided thin film heat flux gauges custom made at AFRL. High bandwidth, time resolved surface heat flux is measured on multiple film-cooled and non-film-cooled HPT rotor blades downstream of both film-cooled and non-film-cooled vane sectors. Upstream wake passing and heat flux is characterized on both rotor pressure and suction side surfaces, along with quantifying rotor phantom cooling effects from non-uniform 1st stage vane film cooling and leakage flows. Fast response heat flux measurements quantify how rotor phantom cooling impacts the blade pressure side greatest; increasing along the pressure side towards the trailing edge. It is discovered upstream vane film-cooling alone can account for 50% of the rotor blade cooling effect, and even outweigh the rotor blade film cooling effect far from the blade showerhead holes. Added unsteady numerical simulation demonstrates how variations in inlet total temperature and incidence angle can also contribute to circumferentially non-uniform rotor heat flux.

Development of a Laser Gas Analyzer for Fast CO2 and H2O Flux Measurements Utilizing Derivative Absorption Spectroscopy at a 100 Hz Data Rate.

We report the development of a laser gas analyzer that measures gas concentrations at a data rate of 100 Hz. This fast data rate helps eddy covariance calculations for gas fluxes in turbulent high wind speed environments. The laser gas analyzer is based on derivative laser absorption spectroscopy and set for measurements of water vapor (H2O, at wavelength ~1392 nm) and carbon dioxide (CO2, at ~2004 nm). This instrument, in combination with an ultrasonic anemometer, has been tested experimentally in both marine and terrestrial environments. First, we compared the accuracy of results between the laser gas analyzer and a high-quality commercial instrument with a max data rate of 20 Hz. We then analyzed and compared the correlation of H2O flux results at data rates of 100 Hz and 20 Hz in both high and low wind speeds to verify the contribution of high frequency components. The measurement results show that the contribution of 100 Hz data rate to flux calculations is about 11% compared to that measured with 20 Hz data rate, in an environment with wind speed of ~10 m/s. Therefore, it shows that the laser gas analyzer with high detection frequency is more suitable for measurements in high wind speed environments.