Auxiliary Flow Research Articles

Optimization of blocked flow field performance of proton exchange membrane fuel cell with auxiliary channels

The flow field optimization design is one of the important methods to improve the performance of proton exchange membrane fuel cell (PEMFC). In this study, a new structure with staggered blocks on the parallel flow channels of PEMFC and auxiliary flow channels under the ribs is proposed. Through numerical calculation method, the effect of blocks auxiliary flow field (BAFF) on pressure drop, reactant distribution and liquid water removal in the fuel cells are investigated. The results show that when the operating voltage is 0.5 V, the current density of BAFF is 21.74% higher than that of the straight parallel flow field (SPFF), and the power density reaches 0.65 W cm−2. BAFF improves performance by equalizing the pressure drop across sub-channels, promoting the uniform distribution of reactant, and enhancing transport across the ribs. In addition, through parameter analysis, it is found that BAFF can discharge liquid water in time at the conditions of high humidification, high current density and low temperature, which ensures the output performance of the fuel cell and improves the durability of the fuel cell. This paper provides new ideas for the improvement of PEMFC flow field design, which is beneficial to the development of PEMFC with high current density.

Study on the tensile-shear mechanical behavior of sandstone using a simple auxiliary apparatus

Mixed failure of rock by tension and shear occurs frequently in underground openings, rock slopes, and transtension faults. In this study, a simple auxiliary device (which consists of an indenter and a hollowed base) is proposed to implement tension-shear tests of rock samples combined with a servo-controlled uniaxial compression machine. Experimental and numerical tension-shear tests are carried out on red sandstones using the proposed auxiliary device and particle flow code. The effects of sample height H and base hollow diameter D on the mechanical behaviors are analyzed in detail, including the peak load, fracture characteristics, and AE characteristics. The results show that peak load increases with the sample height while decreases with hollow diameter due to the change of inclination angle of the failure surface. The initial crack and dominant cracks changed from shear cracks to tensile cracks as D increase from 2 cm to 4 cm, which suggests the transition from shear failure to hybrid tension-shear failure.

Characteristics of internal flow of nozzle integrated with aircraft under transonic flow

Abstract To reveal how aircraft affects the internal flow of the ejector nozzle, we have constructed three model types in this article. These include the model of SR-71 aircraft, the model that only contains ejector nozzle with third auxiliary valve, and the model that integrates the previous two. The results showed that in the transonic regime (M a = 1.2), the third auxiliary flow mainly stems from the boundary layer of the aircraft body. Indeed, a large-scale flow separation phenomenon near the third auxiliary door may require a more nuanced description. The mainstream flow is always in an overexpansion state and results in a Mach plate structure at the exit of the nozzle. However, after integration, the rates of the third auxiliary and the secondary flow are reduced by 18.15% and 5.26%, respectively. Meanwhile, the mainstream flow demonstrates higher overexpansion levels, the position of the Mach plate further downstream changes, and the thrust coefficient decreases by 1.75%. It is worthwhile noting that a strong pressure gradient occurs in the circumferential direction near the connecting structure, which induces lateral flow. This lateral flow breaks away from the wall under the reverse pressure gradient of the nozzle, thus forming three vortex pairs.

International economic relations

Methods. Generalization and system analysis made it possible to determine that one of the urgent problems of our time is the provision of stable development of societies with energy resources. Currently, this development is taking place under conditions of uncertainty and under the influence of geo-economics and geopolitics. The processes that form such uncertainty include high growth rates and changes in regional proportions of energy consumption, increased competition for scarce resources, which implies increased contradictions between the main representatives of the sector in the fuel and energy markets, lack of stability and independence of the energy product. To do this, it is necessary to use tools for generating new ideas for the formation of an economic ideology of energy security as a vector for the development of the state in conditions of constructive destabilization. Results. The author of the article determined that the growing importance of the convergent communication basis for the formation of the economic ideology of the energy security of the state, uniting common or regional infrastructures, can act as tools of economic, technological, military, diplomatic, informational or other influence, which can develop into open conflicts. , the growth of political risk forces The development of state systems in the field of energy security management of Ukraine in conditions of constructive destabilization, including also innovative enterprises, scientific organizations, financial institutions in order to increase the competitiveness of the economy. The gradual transformation of society leads to a reduction in auxiliary labor flows, as well as an increase in decarbonization processes in the strategies of leading oil and gas and energy companies, which are influenced by the main factors that change the activity of the fuel and energy complex. Novelty. It has been determined that there is a trend towards finding solutions to existing problems and resolving crises both at the global and regional levels. At the same time, the failure of the existing global and regional architecture, as well as the imperfection of legal instruments and mechanisms, increasingly threaten the energy security of the country. It is revealed that in this regard it is necessary to develop a unified approach to energy security as a component of the national security system. National energy security consists of components that are interconnected and interact with each other, in other words, national energy security is a functional system that reflects the processes of interaction of interests and threats. The economic ideology of the energy security of the state in the conditions of constructive destabilization is proposed. Practical value. It has been established that maintaining a stable pace of economic development in unstable conditions, the implementation of the planned modernization and innovative development of the country largely depends on the quality of the changes that support these processes. The fuel and energy complex of the country, the potential of which is represented mainly by large corporations - natural monopolies, which, together with other similar complexes, are the basis for the revival and further development of the domestic industry and ensuring the economic security of the state.

Performance analysis of auxiliary entrainment ejector used in multi-evaporator refrigeration system

• Effect of diffuser angle on auxuiliary ejector performance is identified. • Effect of diffuser angle on auxiliary inlet position, angle and, ER is investigated. • An optimal parameters (θ = 4°, LR = 1.9, and γ = 45°) of the new-type ejector exists. • An optimal operating scheme exists under different evaporating temperatures. In this paper, a numerical method is used to maximize the performance of an auxiliary entrainment ejector used in multi-evaporator refrigeration system developed for refrigerated trucks in tropical and humid climates. The Computational Fluid Dynamics model based on the previous study is developed to discuss the effects of key design parameters of an auxiliary entrainment ejector. The simulation model is validated against experimental data of an R134a test rig. The numerical models agree fairly well with the experiments. In order to maximize the efficiency of the auxiliary inlet, the diffuser angle is considered critically. The influence of diffuser angle on the optimal position and angle of the auxiliary inlet is then discussed. As well, the effect of secondary flow and auxiliary flow at varying temperatures on the efficiency of auxiliary entrainment ejector is analyzed. The main results are given as follows: (1) optimal auxiliary inlet position as well as angle and entrainment ratio depend on diffuser angle, and optimum parameters combination (length ratio of 1.9, inlet angle of 45°, and diffuser angle of 4°) of the new-type ejector exists; (2) with the secondary flow working temperature of −10 °C, the entrainment ratio reaches its maximum value of 0.658, and the corresponding entrainment ratio at secondary inlet is 2.60; (3) the auxiliary entrainment ejector can only function if the auxiliary flow working temperature is between −30 °C to −22 °C; (4) it is best to connect the secondary inlet to the medium temperature evaporator, with the auxiliary inlet to the low temperature evaporator, when using the secondary and auxiliary inlet connections to separate evaporators with varied operating temperatures.

Automatic computation of Feynman integrals containing linear propagators via auxiliary mass flow

We proposed a recipe to systematically calculate Feynman integrals containing linear propagators using the auxiliary mass flow method. The key of the recipe is to introduce a quadratic term for each linear propagator and then using differential equations to get rid of their effects. As an application, we calculated all master integrals of vacuum integrals containing a gauge link up to four loops, and we checked the results by nontrivial dimensional recurrence relations.

Multiloop corrections for collider processes using auxiliary mass flow

With a key improvement, the auxiliary mass flow method is now able to compute Feynman integrals encountered in cutting-edge collider processes. We have successfully applied it to compute some integrals involved in two-loop electroweak corrections to $e^+e^-\to HZ$, two-loop QCD corrections to $3j$, $W/Z/H+2j$, $t\bar{t}H$ and $4j$ production at hadron colliders, and three-loop QCD corrections to $t\bar{t}$ production at hadron colliders, all of which are crucial for precision frontier in collider physics in the following decade. Our results are important building blocks and benchmarks for future studies of these processes.

Determination of trace genotoxic impurities in nifedipine by ultra high performance liquid chromatography-electrostatic field orbitrap high resolution mass spectrometry

建立了测定硝苯地平中基因毒性杂质2、6和12的超高效液相色谱-静电场轨道阱高分辨质谱法(UHPLC-Orbitrap HRMS)。样品以甲醇为溶剂,提取后直接进样分析。采用ACE EXCELTM 3 C18-AR色谱柱(150 mm×4.6 mm, 3 μm)分离,流动相为甲醇-0.1%甲酸水(65:35, v/v),等度洗脱。质谱部分采用电喷雾电离(ESI)源。采用正离子平行反应监测(PRM)扫描模式,质谱分辨率为35000 FWHM,杂质2、6、12的[M+H]+母离子准确质量数分别为m/z 347.1230、361.1026、347.1230,提取[M+H]+碎片离子准确质量数分别为m/z 315.0968、298.1069、315.0968,归一化碰撞能量(NCE)分别为10%、42%、10%,外标法定量。对方法进行了详细的方法学验证,结果表明,该法专属性良好,溶剂对杂质测定无干扰;杂质2、6、12质量浓度与其峰面积在0.2~100 ng/mL范围内呈现良好的线性关系,相关系数(r)均≥0.9998;杂质2、6、12在低、中、高3个水平下的回收率为96.9%~105.0%, RSD为1.21%~5.12%,检出限均为0.05 ng/mL,定量限均为0.2 ng/mL。应用该方法对3批硝苯地平样品中的杂质2、6、12进行测定,3批样品均未检出杂质6,但均检出杂质2和杂质12,其检出量未超过限度。该方法灵敏、快速、准确,操作简便,可为药企对硝苯地平的质量控制提供参考,并为药监部门的监管提供有力的技术支持。

Numerical study on dual‐region mass transport at wave flow field of proton exchange membrane fuel cell

AbstractThe performance and stability of proton exchange membrane fuel cells are mainly dependent on mass transports in the gas diffusion layer (GDL). The mass transports in dual‐region including the regions of under‐channel and under‐rib are one of the factors that cause mass uneven distribution. Therefore, the wave structure and the auxiliary flow channel are introduced to enhance these mass transports. Auxiliary conventional parallel flow field (ACPFF), wave flow field (WFF), and auxiliary WFF (AWFF) are transferred into ANSYS MESHING for meshing, then imported into Fuel Cell and Electrolysis module on FLUENT for the solution. This comprehensive AWFF has important influences on mass even distribution and performance. The results reveal that dual‐region forced convections can be made by the periodic waved structure and the auxiliary flow channel. More reactants are forced to appear in GDL of under‐channel and under‐rib. Based on the simulation results, the distributions of oxygen, water, temperature are more even in AWFF. Specifically, the cell performance at high current density is improved obviously. Compared to CPFF, the max power density is increased by more than 4% in this novel flow field (AWFF), which will provide a new trial for the design of a comprehensive flow field.

Flow-equation approach to quantum systems driven by an amplitude-modulated time-periodic force

We apply the method of flow equations to describe quantum systems subject to a time-periodic drive with a time-dependent envelope. The driven Hamiltonian is expressed in terms of its constituent Fourier harmonics with amplitudes that may vary as a function of time. The time evolution of the system is described in terms of the phase-independent effective Hamiltonian and the complementary micromotion operator that are generated by deriving and solving the flow equations. These equations implement the evolution with respect to an auxiliary flow variable and facilitate a gradual transformation of the quasienergy matrix (the Kamiltonian) into a block diagonal form in the extended space. We construct a flow generator that prevents the appearance of additional Fourier harmonics during the flow, thus enabling implementation of the flow in a computer algebra system. Automated generation of otherwise cumbersome high-frequency expansions (for both the effective Hamiltonian and the micromotion) to an arbitrary order thus becomes straightforward for driven Hamiltonians expressible in terms of a finite algebra of Hermitian operators. We give several specific examples and discuss the possibility to extend the treatment to cover rapid modulation of the envelope.

Importance of Three-Dimensional Vehicle Heat Exchanger Modeling

Abstract This article demonstrates, via a comprehensive study, the necessity of using a 3D computational fluid dynamics (CFD) approach for heat exchanger (HTX) modeling within underhood vehicle simulation. The results are presented as the difference between 1D and 3D CFD approaches with a focus on auxiliary fluid (e.g., coolant) temperature prediction as a function of primary fluid (e.g., air) inlet conditions. It has been shown that the 1D approach could significantly underpredict auxiliary fluid inlet temperature due to neglecting the spatial distribution of primary fluid velocity magnitude. The resultant difference in the auxiliary fluid flow HTX inlet temperature is presented and discussed as a function of the uniformity index (UI) of the primary fluid flow velocity magnitude. In addition, the 3D HTX model’s importance is demonstrated in an industrial example of full 3D underhood simulation.

On non-factorisable contributions to t-channel single-top production

We compute the non-factorisable contribution to the two-loop helicity amplitude for t-channel single-top production, the last missing piece of the two-loop virtual corrections to this process. Our calculation employs analytic reduction to master integrals and the auxiliary mass flow method for their fast numerical evaluation. We study the impact of these corrections on basic observables that are measured experimentally in the single-top production process.

Reduction of the planar double-box diagram for single-top production via auxiliary mass flow

The single-top production is an important process at the LHC to test the Standard Model (SM) and search for the new physics beyond the SM. Although the complete next-to-next-to-leading order (NNLO) QCD correction to the single-top production is crucial, this calculation is still challenging at present. In order to efficiently reduce the NNLO single-top amplitude, we improve the auxiliary mass flow (AMF) method by introducing the $\epsilon$ truncation. For demonstration we choose one typical planar double-box diagram for the $tW$ production. It is shown that one coefficient of the form factors on its amplitude can be systematically reduced into the linear combination of 198 scalar integrals.

Effect of auxiliary gas process on double-wire deposition morphology

Double-wire arc additive manufacturing could manufacture large-sized components at low cost and high efficiency; however, serious heat input and heat accumulation result in poor forming quality and limit further efficiency and application. An auxiliary gas process platform for double-wire additive manufacturing is introduced in this paper to explore the influence mechanism of the auxiliary gas on deposition during the manufacturing process. Monolayer and multilayer test results showed that the auxiliary gas had a stirring effect on a liquid molten pool and a cooling effect on deposition layers, and different auxiliary gas parameters could also influence the welding arc stability, which all acted on the deposition morphology. The angle between the auxiliary gas nozzle and welding torch had the greatest impact on the formation of components, followed by the auxiliary gas flow, and the auxiliary nozzle height had minimal influence. When the angle increased from 0° to 30°, the forming morphology gradually flowed. Furthermore, increasing the auxiliary gas flow rate led to the decreased sample height and a serious flowing defect. However, decreasing the nozzle height increased the gas pressure, which would also reduce the height.

Experimental study on active disturbance rejection temperature control of a mechanically pumped two-phase loop

High-heat-flux heat removal is critical for the long-term safety of the high-power electronic device. However, the precise and uniform temperature control of the device is challenging due to various nonlinearities, couplings and disturbances. To this end, active disturbance rejection controller (ADRC), hybrid with an auxiliary feed-forward flow rate controller and an auxiliary subcooling degree controller, is introduced in this paper for the wall temperature control of a microchannel mechanically pumped two-phase cooling loop. First, the optimal flow rate in terms of the heating power is identified to minimize the temperature level and variance. The relative curves between the flow rate and heating power are like character ‘v’ which are used as a feed-forward law for the flow rate regulation. Second, the reference of the sub-cooling degree is determined based on the closed-loop control of the preheater to get a uniform temperature field with least variance. Finally, ADRC is used in the primary loop to control the average wall temperature. The experimental results indicate the efficiency of thermal control for two-phase cooling loop via combination of primary and auxiliary loop. In addition, ADRC performs better in both temperature tracking and disturbance rejection when compared with the conventional PI controller, with superiority in terms of faster tracking and stronger robustness to disturbances and couplings.

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

Optimize the flow field during counter-rotating electrochemical machining of grid structures through an auxiliary internal fluid flow pattern

Flow field distribution plays a vital role in electrochemical machining (ECM) because it can directly affect the machining stability and accuracy of ECM. In counter-rotating electrochemical machining (CRECM), the uniformity of the flow field is difficult to control due to the complicated and changeable flow channel shape. Through the simulation of the conventional lateral fluid flow pattern, it is found that the complexity of the flow channel with grid structures makes the flow field of machining area strongly disordered, which leads to the low velocity zones and dead zones. Based on the simulation results, a new electrolyte flow pattern with an auxiliary internal fluid is proposed, which can remarkably improve the uniformity of flow field by apply supplementary electrolyte to the machining area. Experimental results show that the new flow pattern effectively improves the machining stability of CRECM, and enhances the machining precision of grid structures, the sidewall taper angle is reduced from 29.3° to 7.7°.

Solar Field Output Temperature Optimization Using a MILP Algorithm and a 0D Model in the Case of a Hybrid Concentrated Solar Thermal Power Plant for SHIP Applications

Using solar power for industrial process heat is an increasing trend to fight against climate change thanks to renewable heat. Process heat demand and solar flux can both present intermittency issues in industrial systems, therefore solar systems with storage introduce a degree of freedom on which optimization, on a mathematical basis, can be performed. As the efficiency of solar thermal receivers varies as a function of temperature and solar flux, it seems natural to consider an optimization on the operating temperature of the solar field. In this paper, a Mixed Integer Linear Programming (MILP) algorithm is developed to optimize the operating temperature in a system consisting of a concentrated solar thermal field with storage, hybridized with a boiler. The MILP algorithm optimizes the control trajectory on a time horizon of 48 h in order to minimize boiler use. Objective function corresponds to the boiler use, for completion of the heat from the solar field, whereas the linear constraints are a simplified representation of the system. The solar field mass flow rate is the optimization variable which is directly linked to the outlet temperature of the solar field. The control trajectory consists of the solar field mass flow rate and outlet temperature, along with the auxiliary mass flow rate going directly to the boiler. The control trajectory is then injected in a 0D model of the plant which performs more detailed calculations. For the purpose of the study, a Linear Fresnel system is investigated, with generic heat demand curves and constant temperature demand. The value of the developed algorithm is compared with two other control approaches: one operating at the nominal solar field output temperature, and the other one operating at the actual demand mass flow rate. Finally, a case study and a sensitivity analysis are presented. The MILP’s control shows to be more performant, up to a relative increase of the annual solar fraction of 4% at 350 °C process temperature. Novelty of this work resides in the MILP optimization of temperature levels presenting high non-linearities, applied to a solar thermal system with storage for process heat applications.

Top quark contribution to two-loop helicity amplitudes for Z boson pair production in gluon fusion

We compute the top quark contribution to the two-loop amplitude for on-shell Z boson pair production in gluon fusion, gg → ZZ. Exact dependence on the top quark mass is retained. For each phase space point the integral reduction is performed numerically and the master integrals are evaluated using the auxiliary mass flow method, allowing fast computation of the amplitude with very high precision.

Direct Numerical Simulation of Turbulent Heat Transfer at Low Prandtl Numbers in Planar Impinging Jets

DNS simulations of planar impinging jets are performed to provide reference data to validate RANS models for low-Prandtl turbulent heat transfer. In that configuration, a hot plane jet is blown from a slot at the top wall of a channel and impinges on the cooler bottom wall. The present DNS simulations are carried out at Re=4000 and 5700, based on the jet width and velocity, and for Pr down to 0.01. Two cases are investigated: the case of a laminar uniform jet profile and the case of a fully turbulent inlet profile coming from an auxiliary channel flow simulation running in parallel. The DNS results show how the heat transfer in this configuration evolves from the turbulence-dominated case at Pr=1 to the molecular diffusion-dominate case at Pr=0.01. The temperature field at Pr=0.01 is much smoother than at higher Prandtl number because the much larger heat diffusivity quickly diffuses the temperature fluctuations. The comparison between the laminar and the fully-developed turbulent inflows also show different heat transfer characteristics in the vicinity of the stagnation point, depending on the presence of velocity fluctuations in the bottom-wall boundary layers.