Being able to quickly detect anomalies and reason about their root causes in critical manufacturing systems can significantly reduce the analysis time to bring operations back online, thus reducing expensive unplanned downtime. Machine learning-based anomaly detection approaches often need significant amounts of labeled data for training and are challenging to scale for manufacturing deployments. A robust blended system dynamics and discrete event simulation physics-based modeling methodology is proposed for the task of automated anomaly detection. The blended model consists of discrete event simulation (DES) components for the discrete manufacturing process modeling, and system dynamics (SD) components for continuous variables. The methodology strikes a balance between the computational overhead for online monitoring and the level of details required to perform anomaly detection tasks. The implementation of models takes an object-oriented approach, allowing multiple components of a smart factory to be robustly described in a modular, extendable and reconfigurable manner. The proposed methodology is applied to and validated by data collected from a real commercial manufacturing plant. A production line is modeled with DES components and heat transfer is modeled with SD. The blended model is then utilized for anomaly detection. It is demonstrated that the model-based approach is effective not only for detecting but also explaining particular types of anomalies in a commercial discrete manufacturing system.

To guarantee the safe and highly efficient operation of the high temperature plants, evaluation of the material creep properties and deterioration are necessary. As for small-structure components, especially in service, the material is not sufficient to provide a standard specimen for creep tests. So, as one of the promising techniques, small specimen creep tests have been developed. Three-point bending specimen with fixed constraint (TPBSF) has been attracting scholars’ increasing interests due to its simple stress state and easily achievement of rupture data. However, the TPBSF is limited in many applications for its different constitutive equations and larger errors. In this study, on the basis of beam bending theory, the creep deformation formula of TPBSF was modified. Its feasibility and accuracy was verified by comparing with the creep test data of A7N01 aluminum alloy at 380 °C in literature. Further, based on this modified constitutive equation, finite element method was used to investigate the creep behavior of 0Cr18Ni9 at 600°C. The results show that the modified creep deformation constitutive equation correlates better with uniaxial creep. The corresponding creep parameters B and n of 0Cr18Ni9 at 600°C by TPBSF test are much closer to the experimental results by uniaxial specimen. Von Mises stress and normal stress distribute almost symmetrically along center line at the beginning. But they redistribute with increasing time and reach to a steady state with constant values.

The increase in compressor tip clearance over the lifespan of an aero-engine leads to a long-term degradation in its fuel consumption and operating envelope. A highly promising recent numerical study on a theoretical high-speed axial compressor rotor proposed a novel casing treatment to decrease performance and stall margin sensitivity to tip clearance increase. This paper aims to apply and analyze, through CFD simulations, this casing treatment concept to a representative production axial compressor rotor with inherently lower sensitivity to tip clearance increase and complement the explanation on the mechanism behind the reduction in sensitivity. Simulations of the baseline rotor showed that the lower span region contribute as much to the pressure ratio sensitivity as the tip region which is dominated by tip leakage flow. In contrast, the efficiency sensitivity is mainly driven by losses occurring in the tip region. The novel casing treatment was successfully applied to the baseline rotor through a design refinement. Although the casing treatment causes some penalty in nominal performance, it completely reversed the pressure ratio sensitivity (i.e. pressure ratio increases with tip clearance) and reduced the efficiency sensitivity. The reversed pressure ratio sensitivity is explained by a rotation in the core flow in the lower span region indirectly induced by the flow injection from the casing treatment. The lower efficiency sensitivity comes from a reduction in the amount of fluid that crosses the tip clearance of two adjacent blades, known as double leakage. The casing treatment’s beneficial effect on stall margin sensitivity is less obvious because of the stall inception type of the baseline rotor and its change in the presence of the casing treatment.

Epilepsy is a prevalent neurological disorder affecting 65 million people globally [1]. Anti-epileptic medications fail to provide effective seizure control for 30% of patients, placing them at a 7–17% risk of Sudden Unexplained Death in Epilepsy and recurrent seizures. Surgical resection of the seizure focus is a potentially curative treatment for patients with seizures that electrophysiologically correlate to a focal lesion. For these patients, focal surgical resection can result in 60–70% seizure-freedom rates [2]. However, open resection carries the risk of cognitive impairment or focal neurologic deficit [3]. Recent innovations in MRI enable high resolution soft tissue visualization, and real-time temperature monitoring, making MR-guided ablation therapy a promising minimally invasive technique to restrict the tissue destruction to just the seizure focus. Commercial products (e.g., Visualase, Medtronic Inc.; ClearPoint, MRI Interventions Inc.; NeuroBlate, Monteris Inc.) have recently been introduced for MR-guided laser-based thermal ablation. These products require the physician drill a hole into the skull for ablation probe placement, and may not always be able to ablate the entire seizure focus when the structure has a curved shape (such as the hippocampus) [4]. Incomplete ablation of the seizure focus would lead to seizure recurrence. We have recently proposed concentric-tube steerable needles as a means to address these challenges [4–7]. They enable nonlinear trajectories and offer the potential to enter the brain through the patient’s cheek via a natural opening in the skull base (i.e. the foramen ovale). We have designed and fabricated an MR-compatible robotic system to provide high resolution actuation for helical needle deployment [5]. We have shown in simulation that the curved medial axis of hippocampus can be accessed via a helical needle that delivers the ablation probe into the brain [4]. These preliminary results suggest that MR-guided robotic transforamenal thermal therapy could potentially provide a less invasive approach for potentially curative epilepsy treatment. In this paper we present our first results delivering heat along curved paths in brain phantoms and imaging the resulting treatment zones using MRI.

The interface phase of the Polymer-Metal Hybrid (PMH) structures is formed due to the diffusion of nearby molecular, whose mechanical properties are different from pure metal or polymer, and is possibly the weakest layer. However, it is difficult to measure the interface parameters, such as the thickness and elastic modulus. When the property of PMH structure is predicted by finite element method, it would result in potential simulation errors if the interface is ignored. This study presents a new method to predict the effective interface properties of PMH Structures by Molecular Dynamics (MD) method. The interface formation process in over-molded injection of Polypropylene (PP) on the stamped steel surface was simulated by MD. The effective interface thickness between Iron (Fe) and PP is defined and calculated to be 0.63nm or so and the elastic modulus vertical to the interface is about 6.55GPa. The proposed approach is especially suitable for performance prediction of PMH structure before the physical specimen is manufactured. The predicted results could be utilized in finite element simulation at micro-scale.

A methodology is proposed and developed for the simulation of post-surge condition in a multi-stage compressor that is part of a gas generator system that also includes the combustor and turbine and ducts. Given the essentially one-dimensional nature of surge, the approach basically consists of coupling single blade passage multi-stage RANS CFD simulations of the compressor for with 1D equations modelling the behaviour of the other components applied as dynamic boundary conditions. This method allows for the simulation of the flow behaviour inside a multi-stage compressor during surge and, by extension, for the prediction at the design phase of the time variation of aerodynamic forces on the blades and of the pressure and temperature at bleed locations inside the compressor used for turbine cooling. The main advantages of this method over existing methods are its relatively modest computational time and resource requirements and the fact that it does not require any empirical data input beyond what is used in standard CFD simulations. The method is implemented in a commercial CFD code (ANSYS CFX) and applied to three compressor geometries with distinct features. Simulations on a low-speed (incompressible) three stage axial compressor allows for a validation with experimental data, which shows that the proposed methodology captures the surge behaviour of the system very well both qualitatively and quantitatively. This comparison also highlights the strong dependence of the surge cycle frequency on the volume of the downstream plenum (combustion chamber). Subsequently, the addition of a low-speed centrifugal compressor to the previous compressor is used to demonstrate the adaptability of the approach to a multi-stage axial-centrifugal configuration, yielding qualitatively realistic surge results. Finally, application of the method to an industrial transonic compressor geometry demonstrates the tool on a mixed flow-centrifugal compressor configuration operating in a highly compressible flow regime. A comparison of predicted versus measured shaft loading amplitude during surge is highly promising.

A systematic numerical study has been carried out to investigate the effects of casing treatment slots geometry and location on the stall margin and peak efficiency of an isolated mixed-flow rotor at high subsonic flow conditions. Based on the literature review for axial rotor, a semi-circular axial skewed slot casing treatment placed in the leading edge region was chosen as the starting configuration as it has the best potential of producing stall margin improvement with low peak efficiency loss. A computational parametric study was performed from this baseline casing treatment geometry to identify the most important geometrical design parameters and to arrive at a design with noticeable stall margin improvement and no loss in peak efficiency. The results show that the design parameters with the largest impact on stall margin improvement and peak efficiency are: open area ratio, slot skew angle, slot axial length and slot axial position. The slots depth and slot shape seem to have only limited influence on performance. While not yet optimized, a slot casing treatment design with significant stall margin improvement and no loss in peak efficiency was obtained. To the authors’ knowledge, this work is the most extensive slot casing treatments parametric study so far in term of number of design parameters considered.

The performance of an axial compressor rotor is known to be affected by the variations in tip clearance during its operation. This effect is pronounced for the rear stages of a multistage compressor. This paper describes a novel design that is shown to aerodynamically desensitize the rotor tip to the tip clearance variations. The effect of tip clearance variations on the performance of a baseline low speed, high hub-to-tip ratio axial compressor rotor is studied using CFD. Based on the understanding developed from this flow analysis, the baseline rotor is redesigned by tailoring the tip and redistributing the blade loading over the span. The tip tailoring results in a blade with split dihedral, i.e. of applied dihedral variable from the leading edge to the trailing edge. CFD analysis of the tip tailored configuration shows lower pressure drop with increasing tip clearance as compared to the baseline design. The simulation results are validated through testing in a low speed axial compressor rig, thereby giving experimental support to the desensitization of the rotor to the studied tip clearance variations by tip tailoring.

This paper presents a computational and analytical study to identify and elucidate fundamental flow features associated with the desensitization of performance and aerodynamic stability of an axial compressor rotor to tip clearance change. Parametric studies of various design change on a baseline double circular arc axial rotor led to the identification of two flow features associated with reducing sensitivity to tip clearance, namely high incoming meridional momentum in the tip region and reduction/elimination of double tip leakage. Numerical experiments were subsequently performed on the baseline rotor geometry to validate these two flow features and explain the associated flow physics by variations in incoming meridional momentum and pitch size. Finally, two designs were proposed, namely full forward chordwise sweep and partially low stagger angle, to exploit these flow features. The results indicated that both designs produce the intended flow effects and exhibit lower performance and aerodynamic stability sensitivity to tip clearance.

In a gas turbine engine combustor, performance is likely tied to the spatial distribution of the fuel injected into the dome. The GE/SNECMA CFM56 combustor swirl cup is one example of a design established to provide a uniform presentation of droplets to the dome. The present study is part of a series to detail the dispersion of droplets in practical hardware, and to assess the effect of isolated parameters on the continuous- and dispersed-phase distributions. In this study, the influence of the swirling air outlet geometry is evaluated relative to the effect on the flow field structures and the patterns of droplet dispersion. This is accomplished by comparing the continuous-phase (air in the presence of a spray) and dispersed-phase (droplets) behavior downstream of the swirl cup assembly outfitted with two different conical expansions (“flares”). One features a narrow expansion angle, the other possesses a wide expansion angle. Two-component phase Doppler interferometry was employed to provide the information of droplet size and velocity components as well as continuous-phase velocity components. Photographs of light scattered by droplets from a laser sheet were used for the study of flow field structures. This study reveals that (1) the air stream issued from the narrow flare remains close to the centerline and expands gradually downstream while the air stream issued from the wide flare expands immediately downstream of the swirl cup, and (2) the narrow flare provides weaker droplet dispersion, slower decay of droplet velocities, and finer droplet sizes compared to the wide flare. The results demonstrate that a relatively modest change in flare geometry can create a significant change in the structure of both the continuous and dispersed phases.

Measuring of Sodium Void Reactivity Effect (SVRE), one of the most important tests in China Experimental Fast Reactor (CEFR) physical start-up, is described in the paper, including test method, test results and evaluation of test results. The results met to the test requirement and the sign base of CEFR TIB Accident Special Inspect System. The calculation analysis of CEFR SVRE test has been completed, which provides data support before the test and verifies the reliability of the calculation systems after the test. The technology for analysis and measuring of SVRE in sodium-cooled fast reactor has been accumulated through the research of this test.

Inherent safety properties of reactor have always played an important role in severe accidents preventing and consequences mitigation. With proper design, reactivity feedback mechanisms can bring benign reactivity feedbacks to the reactor core during unprotected transients, thus contributing to the severe accidents mitigation. In overpower transients, the increasing power causes the fuel temperature to increase, which directly brings fuel Doppler feedback and core axial expansion feedback. In unprotected loss-of-flow accidents, as the flow rate decreases, the mismatch of power and flow causes the increase of coolant temperature, thus directly resulting in the coolant reactivity, core radial expansion as well as the control rod driveline expansion feedbacks. Through the simulation of China Experimental Fast Reactor (CEFR) unprotected transients, the influences of different reactivity feedback mechanisms have been investigated and analyzed. The coolant reactivity exhibits significant negative feedback and makes the dominant contribution in controlling the reactivity in both UTOP and ULOF transients.

As an important part of advanced fuel cycle R&D, conceptual study of accelerator driven system (ADS) in China started since 1995. In 2000, China Institute of Atomic Energy (CIAE), Institute of High Energy Physics (IHEP) and other institutes started a ten-year project aiming at ADS fundamental R&D on physics and related technologies, which is one item of “Key Project of Chinese National Program for Fundamental Research and Development (973 Program)” in energy domain. In order to get a better understanding of ADS neutronics characteristic, China Fast Reactor Research Center initiates a preliminary R&D program focused on neutronics design of a small lead-bismuth eutectic cooled ADS with fast spectrum. In this program, the reactor core of a 10MW thermal power ADS called CIADS (China Initiative ADS) with MOX fuel has been studied and designed. For generally concerning, CIADS can operate in either subcritical or critical mode. Different parameters, such as target size and position, position that transmutation assemblies are placed have been studied during the design work. Results show that a half size target and one zone loading can meet the needs for a small size ADS. Moreover, some important physical parameters of CIADS, such as k eff , k s , power peak factor and neutron maximum flux density are evaluated. According to the R&D work, it’s appropriate to set the k s of CIADS at 0.96∼0.98.

Design options of large scale sodium cooled fast reactors are being studied intensively in China, and China Fast Reactor 1000 (CFR-1000) is one of the options. An unprotected transient overpower (UTOP) scenario analysis is carried out during the concept design phase of CFR-1000, aiming at estimating the safety performances of the core during the transient and providing feedbacks for the design. Reactivity insertion scenarios are simulated with different reactivity insertion rates. Safety aspects of core design are evaluated based on the simulation and analyses, including the design of reactivity feedbacks, the design of control rod as well as safety margin of fuel and cladding. The UTOP scenario analysis provides insights of CFR-1000 core design in safety aspect, and valuable information on safety design is given for future China fast reactor design.

The blanket assemblies of China Experimental Fast Reactor (CEFR) were specially designed for the purpose of fuel breeding. There are two parts of the blanket assembly that have significant influence on its thermal-hydraulic feature: the labyrinth throttle set and the wire-wrapped fuel bundle. In this paper, the flow and temperature distribution of sodium coolant in fuel bundle, as well as the pressure drop in the labyrinth throttle set were investigated by solving the three-dimensional conservation equations of mass, momentum and energy, for a wide range of Reynolds number. Different turbulent models: k-ε , SST and Reynolds stress model (RSM) were used and compared with experimental correlations in the study of fuel bundle. The cross flow strength in three typical sub-channels and the influence of steer rods were also investigated. It has been found that the SST model fits best with the experimental correlation and although dampened the cross flow in edge channel, the steel rods installed in the hexagonal duct could enhance the heat transfer by “pushing” the sodium coolant to inner channel of the fuel bundle. Moreover, the relationship between the slot width of the labyrinth throttle set and the pressure drop under different coolant mass flow rate was analyzed, and found out the slot width that satisfied the design requirement of the blanket assembly.

As the first fast reactor in China, the first criticality of CEFR (China Experimental Fast Reactor) was successfully achieved on 21 st July 2010. The first criticality test of CEFR consists of two processes: the fuel loading for net core and the criticality process. In this paper, some detailed information about this test is introduced, including methods, procedures, results, etc. The test results are compared with the theoretical analysis. Comparison shows that the test results match the theoretical analysis very well, which demonstrates that the codes utilized for theoretical analysis are capable of the basic calculation of CEFR.