Cascade Arrangement Research Articles

Effects of Perforated Plates on Shock Structure Alteration for NACA0012 Cascade Configurations

To alleviate the shock boundary layer interaction adverse effects, various active or passive flow control strategies have been investigated in the literature. This research sheds light on the behavior of perforated plates as passive flow control techniques applied to NACA0012 airfoils in cascade configurations. Two identical perforated plates with shallow cavities underneath are accommodated on the upper and lower surfaces of each airfoil in the cascade arrangement. Six different cascade arrangements, including a baseline configuration with no control applied, are additively manufactured, with different perforated plate orifice sizes in the range of 0.5–1.2 mm. A high-speed wind tunnel with Schlieren optical diagnosis and wall static pressure taps is used to investigate the changes in the shock waves pattern triggered by the perforated plates. Steady 3D density-based numerical simulations in Ansys FLUENT are conducted for further analysis and validation. In the cascade configuration, the perforated plates alter the shock structure, and the strong normal shock wave is replaced by a weaker X-type shock structure. Eventually, a 1% penalty in overall total pressure loss is induced by the perforated plates because of the negative loss balance between the reduced shock losses and the enhanced viscous losses. Further studies on perforated plate geometrical features are needed to improve this outcome in a cascade arrangement.

Water and Thermal Management in PEM Fuel Cells Using Feasible Humidity Plots and Model Predictive Controllers

Water and thermal management are critical for the performance, efficiency and longevity of PEM fuel cells (PEMFCs). Effective water and thermal management require the design of control systems that can maintain the water balance and temperature at stable and optimal levels. In this paper, we consider a stack of PEM fuel cells integrated with a water recovery and cooling system. A mechanistic dynamic model is developed to be able to predict the water content and temperature in response to the fuel cell inputs. Water management uses a cascade arrangement of a supervisory Model Predictive Controller (MPC) and local anode and cathode PID humidity controllers to balance the membrane water content. Thermal management consists of a separate MPC controller to regulate the fuel stack temperature. One novelty of this work lies in identifying and utilizing the feasible region for the relative humidities of the anode and cathode when controlling the membrane water content. We introduce the feasible humidity plots (FHP) which define the feasible values for the anode and cathode relative humidities for a given fuel cell design and its operating conditions. This useful information helps to assign the set-point values to the local PID humidity controllers of the water management system. It is shown by simulations that the water and thermal management MPC controllers work in tandem and successfully track the desired set-point changes in humidity and temperature while rejecting external disturbances such as load changes. In addition, the control system is robust against modeling errors and possible model-plant mismatch introduced by fuel cell aging.

Design of an Intelligent Cascade Control Scheme Using a Hybrid Adaptive Neuro-Fuzzy PID Controller for the Suppression of Drill String Torsional Vibration

Eliminating the excessive stick–slip torsional vibrations of drill strings by utilizing an effective controller can significantly increase penetration rates and reduce drilling operation costs. The present study aims to develop a fast and intelligent cascade control structure for a multi-degree-of-freedom drill string system under torsional vibrations. The proposed control configuration consists of two control loops in a cascade arrangement. The first controller estimates the top drive velocity reference from the actual drill bit velocity and its reference. The role of the second controller is to regulate the top drive velocity to its reference by generating the necessary torque for the drilling operation process to progress. Each control loop is designed based on a hybrid adaptive neuro-fuzzy PID and feedforward term. The latter assures fast regulation when there are sudden changes in operation. To evaluate the performance of the suggested cascade feedforward neuro-fuzzy PID (CFF-NFPID) control structure, extensive simulations were conducted using Matlab/Simulink. The simulation results clearly showed that the proposed CFF-NFPID controller provided high-performance control with variations in the weight on the bit and the desired drill bit rotary speed in comparison with that of cascade feedforward fuzzy PID, sliding-mode, cascade feedforward PID, cascade PID, and conventional PID controllers. Furthermore, the control robustness is very suitable despite the change in the system parameters.

A Novel Multilevel Inverter for Renewable Energy Applications with Optimized Controller and Reduced Switches

Multilevel converters have the capability of handling high power as well as deliver output with reduced harmonics. So they can be implemented with renewable energy sources to produce multilayer output with symmetric cascade arrangement with reduced switches. Here the control technique is developed in such a way to reduce the harmonics in the grid integrated PV system. The paper proposes optimized Fractional Order Proportional Integral Derivative (FOPID) controller for a seven level reduced switch multilevel inverter. The War Strategy Optimization Algorithm (WSOA) which utilizes optimizing the strategic movements of armed forces (assault and defend) towards the final optimal value is used to optimize the FOPID controller. This WSOA algorithm is used to adjust the gain parameters of the FOPID controller there by improving the system performance. The characteristics of grid connected PV system are regulated by implementing this suggested technique. The projected approach is incorporated using MATLAB / Simulink and the performances are evaluated and compared with the conventional techniques like GA – PID and WSOA – PID controllers.

Field installation of ion exchange technology for purification of retention reservoirs from nitrogen-based nutrient contamination

N- and P-nutrient contamination is recognised as one of the key factors that reduces the quality of water. In this context, a new water purification installation was set up in the Turawa reservoir (district Opole, Poland). The process involves ion exchange columns operated in twin configuration: once one column filtrates water, the second one regenerates. The installation design is modular, and the devices are placed in a container station. This enables efficient water purification in various locations and further offers scalability. The research focused on the design and optimization of the installation, as well as environmental assessment of how the installation influenced the quality of water. This technology afforded a decrease in the concentrations of NO3− ions, suggesting an apparent selectivity. The removal of NO3− reached 97 % and was maintained for over 100 m3 of purified water. In turn, the removal of PO43− was not effective; however, the collected data allowed the installation design to be adjusted such that the cascade arrangement of ion exchange columns can be considered. The technology was assessed over all four seasons in the two-year test period (2020−2021). This revealed that environmental factors, such as season, air temperature, wind, and relative humidity, influence the operation of the installation. The installation functions optimally in spring with an average air temperature of 11–20 °C, high relative humidity of 90–100 %, and an average wind speed of 2 m/ s. The implementation of the technique could easily broaden the perspectives of Earth's water preservation and sustainability.

Cascaded Thinning in Upscale and Downscale Representation for EEG Signal Processing.

Smoothing filters are widely used in EEG signal processing for noise removal while preserving signals' features. Inspired by our recent work on Upscale and Downscale Representation (UDR), this paper proposes a cascade arrangement of some effective image-processing techniques for signal filtering in the image domain. The UDR concept is to visualize EEG signals at an appropriate line width and convert it to a binary image. The smoothing process is then conducted by skeletonizing the signal object to a unit width and projecting it back to the time domain. Two successive UDRs could result in a better-smoothing performance, but their binary image conversion should be restricted. The process is computationally ineffective, especially at higher line width values. Cascaded Thinning UDR (CTUDR) is proposed, exploiting morphological operations to perform a two-stage upscale and downscale within one binary image representation. CTUDR is verified on a signal smoothing and classification task and compared with conventional techniques, such as the Moving Average, the Binomial, the Median, and the Savitzky Golay filters. Simulated EEG data with added white Gaussian noise is employed in the former, while cognitive conflict data obtained from a 3D object selection task is utilized in the latter. CTUDR outperforms its counterparts, scoring the best fitting error and correlation coefficient in signal smoothing while achieving the highest gain in Accuracy (0.7640%) and F-measure (0.7607%) when used as a smoothing filter for training data of EEGNet.

An integrated cooling mechanism for photovoltaic systems

Photovoltaic (PV) panels, despite their potential as a renewable energy source, suffer from performance degradation due to temperature rise. This research proposes an integrated passive cooling system that combines finned convective and radiative cooling with graphite-infused phase change material (PCM) in a cascade configuration. The cascade arrangement creates temperature stratification, delaying and restricting temperature increases. Graphite-infused PCM enhances thermal conductivity, facilitating efficient heat dissipation. Additionally, a finned heat sink augments convective heat transfer between PCM and the ambient environment, increasing the heat transfer area. A thin silica layer with pyramid lattices is incorporated to improve radiative heat transfer, particularly beneficial in hot climates with a significant temperature difference between the PV cell and the sky. A mathematical model is developed and validated against experimental data to assess the system’s performance. The model simulates PV cell temperature variations for six different scenarios to identify the most effective cooling mechanism. The study demonstrates a remarkable 27 °C reduction in peak PV cell temperature, translating to a substantial up to 100% increase in overall PV cell efficiency. This research contributes to the evolving landscape of PV cooling technologies and provides valuable insights for optimizing PV panel performance.

Structural and Catalytic Insight into the Unique Pentacyclic Triterpene Synthase TwOSC.

The oxidosqualene cyclase (OSC) catalyzed cyclization of the linear substrate (3S)-2,3-oxidosqualene to form diverse pentacyclic triterpenoid (PT) skeletons is one of the most complex reactions in nature. Friedelin has a unique PT skeleton involving a fascinating nine-step cation shuttle run (CSR) cascade rearrangement reaction, in which the carbocation formed at C2 moves to the other side of the skeleton, runs back to C3 to yield a friedelin cation, which is finally deprotonated. However, as crystal structure data of plant OSCs are lacking, it remains unknown why the CSR cascade reactions occur in friedelin biosynthesis, as does the exact catalytic mechanism of the CSR. In this study, we determined the first cryogenic electron microscopy structure of a plant OSC, friedelin synthase, from Tripterygium wilfordii Hook. f (TwOSC). We also performed quantum mechanics/molecular mechanics simulations to reveal the energy profile for the CSR cascade reaction and identify key residues crucial for PT skeleton formation. Furthermore, we semirationally designed two TwOSC mutants, which significantly improved the yields of friedelin and β-amyrin, respectively.

Conceptual design of a sorption-based cryochain for the ETpathfinder

Next-generation gravitational wave detectors, including the Einstein Telescope [1][2], aim to achieve amplitude-spectral-density strain sensitivities on the order 10−24m/Hz[3]. In the low-frequency band such sensitivities can only be obtained when thermal noise, mainly stemming from the mirror coating, is reduced by employing cryogenic cooling techniques for the mirrors. The optical surface of the mirror should not vibrate with strain noise amplitude spectral densities above 10−20m/Hz for the cryogenic mirrors in the Einstein Telescope [3]. The ETpathfinder research facility [4][5], aims to facilitate the development and testing of critical new technologies required for the design and operation of future gravitational wave detectors. A key enabling technology for the design and operation of such advanced interferometers is the cryogenic system that cools the main optics to a temperature of approximately 10 K. Given the stringent requirements on vibrational noise for these optics, the cryogenic cooling under continuous operation should be essentially vibration free. Joule-Thomson cryocoolers using sorption compressors are known to generate an absolute minimum of vibrational noise during operation. We propose a modular cryochain design comprised of a system of sorption compressors and Joule-Thomson cold stages fitting the ETpathfinder project requirements. In this paper, we present the conceptual design of the cooler chain that is based on a parallel cascade arrangement of a 40 K neon stage, a 15 K hydrogen stage and a 8 K helium stage. The operating parameters of the sorption-based cooler chain are selected via a hybrid modeling workflow, aiming to optimize performance and other design considerations within an envelope of acceptable design parameters.

CMOS Linear Laser Driver for Intermediate Frequency over Fiber (IFoF) Links

The main objective of the proposed linear laser driver (LLD) is to reduce signal distortion in an analog direct modulation laser configuration used for intermediate frequency over fiber links. This work draws on an open-loop configuration featuring two differential pair blocks in a cascade arrangement to achieve a bandwidth measurement of 415 MHz at the half-power point, a total harmonic distortion of 4.57% for a fundamental frequency of 100 MHz, and an amplitude of 100 mVpp. The LLD provides a gain of 12.3 dB for a differential output and an output impedance of 46 Ω. The design, layout, and integration correspond to the process design kit for TSMC 65-nm CMOS technology. Experimental results show the advantage over other previously reported laser drivers.

Triple Cascade Arrangement for Purifying Regenerated Uranium Hexafluoride from 232,234,236U

Triple Cascade Arrangement for Purifying Regenerated Uranium Hexafluoride from 232,234,236U

Insight into heat transfer process of graphene aerogel composite phase change material

With electronic device miniaturization and integration, its thermal management is encountering challenges of high heat flux and eliminating thermal stress. Phase change thermal control is paid more attention to due to its high energy density and temperature uniformity. Therefore, a visual experimental platform was established to investigate the heat transfer and phase change characteristics of graphene aerogel composite phase change materials in this study. The results indicate that the heat dissipation enhancement of those composite materials can reach 220.8%, while graphene aerogel has the opposite effects of heat conduction enhancement and convection suppression. Furthermore, two new cascade arrangements are proposed and the effects of cascade arrangements on heat transfer performance are discussed. The improvement effect is best when the thermal conductivity increases longitude from top to bottom, whose heat dissipation efficiency is 207.5%, which is 11% higher than that of the group without cascade configurations. The horizontal cascade arrangement proposed in this study achieves an effective combination of heat conduction enhancement and convection heat transfer. Its heat dissipation is 12% more effective than the cavity filled with pure CPMCs using the same amount of porous materials, and the phase change speed is increased by 149 s.

Single-Phase H-Bridge Rectifier Fed High-Speed SRM System Based on Integrated Power Control

Traditionally, an uncontrollable diode bridge rectifier (DBR) is employed to supply the constant DC voltage for the asymmetric half-bridge (ASHB) converter fed switched reluctance motors (SRMs), which brings about inferior AC side power quality. In this article, a high-speed SRM drive system based on integrated power control scheme is proposed, which not only realizes the regulation of SRM but improves the AC side power quality. For the topology, a single-phase H-bridge rectifier and ASHB converter are connected in a cascade arrangement to form an AC-DC-DC converter to drive the SRM. For the control, the proposed integrated power control scheme governs the rectifier and SRM as one control unit in which stable motor speed and high AC side power factor are realized via regulating the input real and reactive power, respectively. Moreover, the proposed system has bi-directional power flow capability, which means the power can flow out of and into the AC side. Experiments are carried out to investigate the steady-state and dynamic performances of the proposed driving system. The experimental data and performance comparison confirm its effectiveness.

Performance assessment of control strategies with application to NGL separation units

In this contribution, the problem of NGL separation control is addressed by dealing with the most common process schemes. The main goal is to achieve a specified ethane recovery as well as maintaining certain levels of methane impurity in the demethanizer column. An indirect control of composition through the temperature control in the column is proposed. A cascade arrangement between the column temperature control and the controller that maintains a constant ratio of boil-up to column bottom product is proposed for the improvement of methane impurity levels. Additionally, an “inferential” control approach based on Antoine's law is formulated and tested to enhance the ethane recovery control. The performance indexes calculated for ethane recovery and methane impurity show the superiority of the proposed control structure in each NGL separation process scheme. When the feed flowrate is reduced by 10%, the proposed control strategy allows a lower deviation from the target and a smaller offset with a reduction of 73.7% for ethane recovery and 72.7% for the methane concentration in the conventional process, 86.6% for ethane recovery and 96.4% for methane concentration in the GSP, and 97.1% for ethane recovery and 91.1% for methane concentration in the CRR process. In case of sinusoidal variations of inlet flowrate, the integral square error is reduced by 99.33% for methane bottom concentration in the GSP process scheme, while ethane recovery shows a reduction of 82.69% in the CRR scheme.

Experimental investigation on load mitigation of a 5 MW wind turbine in digital fluid power pitch system test rig based on predictive load mitigation controller

ABSTRACT The pitch control system plays a vital role in generating rated power and mitigates mechanical loads during strong wind gusts. Generally, the hydraulic pitch system deployed in a large-scale wind turbine uses a proportional/servo valve to adjust the pitch angle. However, these valves suffer from low operating efficiency which leads to poor pitching performance. Thus, a high-speed digital hydraulic valve-based Digital Fluid Power Pitch System (DFPPS) test rig was proposed in this paper. Moreover, the conventional controller was not able to produce adequate pitching performance during high wind flux. Therefore, a machine learning-based pitch controller was implemented in the developed test rig. The developed DFPPS test rig comprises simulation loop (Wind Generator System (WGS) model, pitch gear model, Predictive Load Mitigation Controller (PLMC), and pitch load model), and DFPPS-hardware interfaced through an I/O interface. Here, PLMC was developed to improve the load mitigation performance without compromising the generator performance at high wind speeds. The proposed PLMC is a cascade arrangement of Recurrent Elman Neural Network (RENN) tuned Fractional-Order Proportional Integral Derivative (FOPID). Further, for collecting the optimal datasets to train the RENNs in PLMC, a Customized Particle Swarm Optimization (CPSO) algorithm was utilized. Two experiments are performed considering the developed WGS model and benchmark Fatigue Aero-elastic Structure Turbulence (FAST) simulator deployed in the DFPPS test rig. The experimental results of PLMC (experiment) were compared to simulation results PLMC (simulation). Further, the experimental output of the PLMC was compared to established controllers in the literature (Radial Basis Function tuned Fractional-Order Proportional Integral Derivative (RBF-FOPID) and baseline Proportional Integral (PI)). In the experiment using FAST, relative to RBF-FOPID, the PLMC (experiment) decreased the Standard Deviation (STD) of blade and tower moment by 81.5% and 81.4%, respectively. Consequently, compared to baseline PI, the PLMC (experiment) reduced the STD of blade and tower moment by 85.6%, and 84.4%, respectively. The proposed controller effectively mitigated the load and also the generator performance was close to the rated value than its counterparts.

Modified optimal series cascade control for non-minimum phase system

Abstract This article contributes to handling the Non-Minimum Phase (NMP) system with time delay in the existence of uncertainty and disturbances. The series cascade control scheme is used to overcome such problems. The secondary loop architecture in a series cascade scheme is formulated in the Internal Model Control (IMC) framework. The tuning of fractional-filter via a delayed version of Bodes’ ideal transfer function approach of primary loop controller in a series cascade arrangement shows the novelty of this work. The primary loop controller is designed in the IMC framework after accountability of inverse response and dead-time compensator. Furthermore, Particle Swarm Optimization (PSO) is adapted to accomplish the optimal value of controller settings. The Riemann sheet principle is used to determine stability. The sensitivity investigation is performed to know the robustness of the offered controller. For the effectiveness of the suggested scheme, two case studies are revealed in this paper.

Selection of the best 3-section squared-off cascade to enrichment of the 126Xe and 131Xe using particle swarm optimization algorithm

In this study, the effect of arrangements of flexible 3-section squared-off gas centrifuge cascades on middle isotopes of xenon enrichment,126Xe, and 131Xe, to a specific enrichment level (85%) has been investigated. 3-section squared-off cascades can be arranged in three different arrangement types depending on the feed flow that enters in the first, second, or third section. To simulate the 3-section squared-off cascades, the number of equations and unknown parameters must be equalized by considering four unknown parameters as input data in addition to other input parameters. These parameters are returned flow fractions between two sections, cascade cut, and first-stage cut. Two codes named SQ3-PSO and SQ3-SS were developed using Particle Swarm Optimization (PSO) and Salp Swarm algorithms (SSA) to optimize the cascade parameters and were compared together. Maximizing cascade capacity production, recovery factor, and D function were selected as the objective function main items. The comparison of the results showed that the PSO algorithm is somewhat more satisfactory than the SSA. All three cascade arrangement types with 22 stages and 140 centrifuges were optimized for 126Xe and 131X enrichment and their performance was compared. In the end, it was found that the optimal cascade arrangement varies with changing the target isotope. The descending configuration had better 126Xe separation efficiency, 73.64%, than the others, while the ascending counterpart had the highest 131Xe separation efficiency, 77.57%.

Helium recovery and purification by dual reflux pressure swing adsorption

Global demand for helium has risen over the past few decades driven by a vast range of applications based on its unique properties. Helium is often produced industrially from the vent streams of nitrogen rejection units (NRU) in liquefied natural gas (LNG) plants, where it accumulates because of its low boiling point. Further deep cryogenic processing stages are then required to upgrade its concentration to saleable levels. We report here an experimental and simulation-based investigation of an alternative, non-cryogenic process based on dual reflux pressure swing adsorption (DR PSA) cycles to recover and purify helium from model binaries including a 1 mol% He + 99 mol% N2 mixture representative of NRU vent streams. Binderfree zeolite 13X was used as the adsorbent in an experimental campaign employing a laboratory-scale DR PSA apparatus. The experimental runs validated a non-isothermal numerical model with an average deviation of 1 mol% between the simulated and experimental product compositions. The single-stage DR PSA experiments produced helium product streams with purities ranging from (30 to 99) mol% from feeds with concentrations ranging from (1 to 50) mol% He. Two DR PSA stages were required to upgrade mixtures containing 1 mol% He to a target product purity of > 99 mol%. A cascade arrangement of two DR PSA systems with a waste recycle enabled a 99.999 mol% He purity product at 95 % recovery, which is competitive with conventional cryogenic systems. This cascade DR PSA process used either two or three compressors depending on the feed gas pressure, with associated duty costs of 1.5 MJ∙(mol He produced)–1. This is lower than several membrane processes described in the literature and could be more cost-effective for smaller-scale applications than cryogenic processes with similar levels of separation performance.

Effect of Film Cooling on Entropy Noise Generation in a Stator Blade Row

In this study the effect of film cooling on entropy wave attenuation and indirect entropy noise generation was investigated in a subsonic stator blade row with a leading-edge, pressure-side, and suction-side cooling geometry. The investigation was conducted on a small blade midspan section (in a linear cascade arrangement), using a three-dimensional unsteady Reynolds-averaged Navier–Stokes simulation approach. A planar entropy wave was injected at the inlet for a range of frequencies from 200 to 1000 Hz. Additionally, the compact model by Cumpsty and Marble was extended to account for a cooling flow. Results show that for an increase in coolant mass flow rate of 3.4%, the entropy noise increases by about 12% for the transmitted pressure wave, whereas the reflected pressure wave increases by about 9%. This is attributed to the change in convective acceleration in the blade passage. The film cooling was found to have a minor effect in promoting the entropy wave attenuation. The extended compact model was capable of capturing both the entropy wave attenuation and increase in the acoustic transfer function due to film cooling.

Optimization of energy consumption and temperature fluctuations for a household freezer using non‐toxic and non‐flammable eutectic phase change materials with a cascade arrangement

Optimization of energy consumption and temperature fluctuations for a household freezer using non‐toxic and non‐flammable eutectic phase change materials with a cascade arrangement