Multi-stage Configuration Research Articles

Assessment of single passage simulations for the aeroelastic stability of a multistage centrifugal compressor

In this paper, the aeroelastic flutter stability of an impeller is investigated numerically with single passage and full annulus URANS simulations carried out on one side on a single stage configuration including a strut and the impeller and on the other side on a multistage configuration in which two additional diffusers are considered downstream. The robustness of single passage simulations relying on the use of multiple frequency phase-lagged boundary conditions is put to the test especially in the case of the multistage configuration for which both blade passage and aeroelastic effects have to be taken into account. Comparisons between single passage simulations on the single and multistage configurations indicate that the impeller-diffuser interaction acts locally on the impeller fluid-structure interface and has only little effect on the generalized aerodynamic forces. Full annulus simulations have also been carried out to assess the accuracy and efficiency of single passage simulations which introduce additional hypotheses of periodicity in the flow. Full annulus simulations are competitive in terms of wall clock since the convergence to the periodic state is faster than with single passage simulations involving the Fourier approximation of the flow field.

Combined pyrolysis and sulphided NiMo/Al2O3 catalysed hydroprocessing in a multistage strategy for the production of biofuels from milk processing waste

Pyrolytic bio-oils derived from renewable organic wastes are credible second-generation biofuels. In crude form, bio-oils are inherently complex mixtures that largely limit their direct application as fuels and integration into existing petroleum infrastructure, without additional upgrading. Herein, we report on low-oxygenated biofuel production from milk processing sludge using a multistage process configuration. In the first stage, bio-oil yields were maximised (57.7%) under slow pyrolysis conditions at 450 °C. Bio-oils were enriched in aliphatic hydrocarbons (19–22% alkanes), (11–14% alkenes) and alkyl nitriles (57–63%), while aromatics remained low at <2%. A relatively low bio-oil O/C molar ratio (0.08 to 0.1) and a correspondingly high HHV (40.8–41.8 MJ/kg) display possible fuel applications. Increasing pyrolysis temperatures (>450 °C) was not beneficial to bio-oil yields, reduced hydrocarbon contents and increased heteroatoms (O, S, N). In the second stage, sulphided Ni-Mo/Al2O3 catalysed hydroprocessing and distillation upgrading of bio-oils generated 100% C8-C22 saturated alkane distillates. With regard to fuel properties, oxygenation (0.26–0.89%), viscosities (4–6 mm2/s) and densities (ca.0.82 g/cm3) were comparable to standard diesel fuels. Resultant HHV (46.24 MJ/kg) and cetane index (69) of distillates produced from 450 °C bio-oils far exceeded those of diesel fuel standards, demonstrating direct fuel application and petroleum fuel compatibility.

Cost optimization of multi-stage gap membrane distillation

Estimating the costs and performance of emerging separation technologies is technically challenging because of the complex design space and the interdependence between system and module-level design decisions. This work develops a process-based cost-optimization model that minimizes the levelized cost of water (LCOW) produced using multi-stage gap MD. The model fully captures solution properties, heat transport, and mass transport relationships within each membrane module, specifies the optimal multi-stage configuration of modules in series, and determines cost-optimal operation of each stage and the system as a whole as a function of gap type, the number of stages, feed conditions, and desired water recovery. We estimate that the LCOW for recovering 50% of a 100 g/L feed using conductive gap multi-stage MD is approximately 6.5 $ per m3 of product water. Cost-optimal designs of multi-stage systems balance operational costs (primarily energy) and capital costs (primarily membrane). This balance results in stages having a different design and operation across the system (e.g. initial stages operating with chilling and heating and end stages using only heating). Sensitivity analysis on the model results suggests that improving membrane parameters and module designs may provide modest cost reductions of <15%.

The costs and benefits of multistage configuration: A framework and case study

Product configuration systems (PCSs) have been successful applications of artificial intelligence principles in engineer-to-order (ETO) companies in recent decades. Such applications mainly focus on quotation or production processes rather than multiple business processes. However, in some cases, there could be a benefit of applying multistage PCSs, that is, PCSs that can support several business processes. To investigate the conditions required for the beneficial application of multistage PCSs, this study examines the costs and the benefits associated with this approach. This is done by outlining a framework that defines multistage configuration, hereunder the identification of costs and benefits, as well as the strategies for implementing the approach. The framework is tested through a case study of an ETO company, which provides empirical evidence of the feasibility and the potential benefits of multistage configuration projects. Specifically, the case study shows that investments are modest when moving from a single-stage configurator strategy to a multistage strategy, while demonstrating significant benefits. This paper thereby provides two novel contributions: (1) a definition of multistage configuration, hereunder two strategies for its implementation and (2) empirical evidence that identifies costs and benefits of multistage product configuration, thereby, supporting its feasibility.

Optimal Multi-stage Configuration Allocation with Applications to Video Advertising

In modern applications of real-time resource allocation, for example allocating ad opportunities created by users to relevant advertisers during video streaming, a prevalent scenario is when an arriving user can be served under different configurations''. For example, in video advertising, a configuration can be an arrangement of video-ads of various lengths and formats for a subset of advertisers, showing up at different time-stamps of the video. Each selected configuration assigns a certain number of impressions to each advertiser. Depending on their long-term contracts, each advertiser is willing to pay for a certain number of impressions during the decision making horizon at a per-impression price depending on the assigned configuration. While this application is real-time, there is an inherent allowance for latency in showing ads to users, as several of these ads show up in the middle (or at the end) of the video. This provides an opportunity for ad allocator to batch the users and to make more profitable allocation decisions. While designing algorithms for the fully online variant of this setting has been studied in the literature [Devanur et al., 2016], the multi-stage variant where the allocation decisions are made batch-by-batch is not studied. Motivated by the above application, we study designing optimal competitive multi-stage configuration allocation algorithms (with preemption) in an adversarial setting, where users arrive in batches in a stage-wise fashion. The allocator then decides on an irrevocable configuration for each of the users in an arriving batch at each stage so as to maximize the total revenue. We propose a novel convex-programming based multi-stage configuration allocation algorithm that is 1-(1-1/K)^K competitive, where K is the number of stages. We further show an intimate connection between the convex programs used in each stage and a recursive functional equation (with a sequence of polynomials of decreasing degrees as its solution). Using this connection, we develop a recursive primal-dual analysis for our algorithm and extend the previous analysis framework of multi-stage fractional matching [Feng and Niazadeh, 2021] to this more general setting. Interestingly, we show there is an intimate connection between convex Lagrangian dual of each stage of our algorithm and how the primal-dual analysis needs to be set up, which might be of independent interest.

Systematic Analysis Reveals Thermal Separations Are Not Necessarily Most Energy Intensive

Summary At the industrial level, separation of a variety of mixtures is predominantly carried out by thermally driven processes such as distillation. Nevertheless, the current literature seems to suggest that much is to be gained by replacing these processes with alternative non-thermal methods, which will potentially require a fraction of the energy used by distillation. This is primarily due to the widespread perception that thermal separation processes, particularly those that involve vaporization, are highly energy intensive. However, this belief is not well founded, because it is based on extrapolation from comparisons in the literature, many of which make ad-hoc assumptions and result in incorrect conclusions. Our analysis shows that this confusion arises because the processes utilize different types of energy: heat and electricity. Here, we present a consistent framework that enables a fair comparison between different processes that consume different forms of energies. Using this framework, we refute the general perception that thermal separation processes are inherently the most energy intensive and conclusively show through the examples of two challenging mixtures constituting components with low relative volatilities, that distillation processes, when run properly, can consume remarkably lower fuel than non-thermal membrane alternatives, which have often been touted as more energy efficient.

Optimization Problems of Launch Vehicle Design

In spite of great progress in the rocket technology and practical experience in the development and production of a number of rocket space systems (i.e., launch vehicles – LV), the task of optimizing the LV structure is still essential. Even in the fundamental work of well-known American scientists [1] in 1965, where the task of optimization of propellant distribution between the stages of a multi-stage launcher configuration was raised, an approximate solution was proposed. It was shown that in case of equal specific impulses of rocket engines of LV stages working successively, the equal distribution of characteristic velocities for each stage is the optimal one. Later, the same conclusion was made in the teaching aids published in Russia [2]. The treatise [3], published in the US in 2004, says there is no other solution found yet. This paper suggested a new approach in solving this and some other related problems.

Performance analysis of a single and multi-staged direct contact membrane distillation module integrated with heat recovery units

In the present work, a single and multi-staged Direct Contact Membrane Distillation (DCMD) module is designed with optimal flow configuration to get the best DCMD system performance. An energy-efficient system was developed by integrating the DCMD module with heat exchangers (HXs). The heat exchangers were used to recover energy carried by the outgoing streams. The water productivity and energy requirement for the integrated DCMD-HX system was evaluated for both single and multistage DCMD configuration having the same membrane surface area. It was observed that the multistage DCMD configuration yielded a maximum water productivity of 16.34 LMH. An optimization problem was also developed with an objective to maximize the gain output ratio (GOR) of the integrated process. The multistage DCMD configuration could achieve the maximum GOR of 0.942. The minimum specific thermal energy consumption achieved for the integrated DCMD-HX system is 1100 kWh/m3 and 800 kWh/m3 for single and multistage DCMD, which is in accordance with the literature [1,2]. With optimization, the STEC value reduces to 711 kWh/m3 and 670 kWh/m3, respectively for single and multistage DCMD. The proposed flat sheet DCMD-HX configuration is found to be more energy-efficient than earlier literature reported DCMD-HX configuration without optimization. Further, optimization result concludes that a Mixed Integer Non Linear Programming (MINLP) problem can be formulated to achieve maximum GOR and product water by manipulating the number of DCMD stage and module for fixed membrane area.

Experimental Study of Steam Injection into a Water Stream for Milk Sterilization

Steam injection into milk stream is a frugal method for milk sterilization. In this paper, the steam injection into a steady liquid water stream (instead of milk stream) is experimentally investigated. A transparent mixing chamber is fabricated using which the variations in steam condensation process are photographed by a high-speed camera. The length of the steam plume in water is determined using image processing of the still images of the phenomenon. The factors affecting the quality of steam condensation are studied. Increasing the chamber pressure reduces the steam plume length which in turn improves the quality of direct contact condensation. Decreasing the liquid water flow rate has an adverse effect on the phenomenon where the steam plume length is increased. It is also found that injecting the steam in a multi-stage configuration results in a reduction of the steam plume length, thereby, improving the condensation process.

Large magnitude, sign controllable, ultrafast group-velocity control via resonant cascaded nonlinearity in tandem.

Resonant cascaded nonlinearity (RCN) induced by optical parametric amplification (OPA) in a chirped quasi-phase-matching chip can be applied to control the group velocity of ultrafast lasers. However, the group delay produced in a single-stage OPA is limited to the pulse duration, and its sign cannot be altered. In this study, we propose a tandem RCN configuration with multiple OPA stages that can produce large-magnitude and sign-controllable group delays. The group delay produced in the multi-stage configuration is shown to be a linear superposition of each single-stage group delay. By virtue of the byproduct idler in the OPA process, the signal-group delay can be altered from positive to negative (and vice versa) with the same chip structure and pump condition. In the numerical simulation with two OPA stages, both a positive and negative group delay of six-fold pulse duration were achieved for 100-fs pulses at 1550 nm. A much larger group delay can be achieved by increasing the number of OPA stages.

Navigation of Three Cooperative Object-Transportation Robots Using a Multistage Evolutionary Fuzzy Control Approach.

This article proposes a new multistage evolutionary fuzzy control configuration and navigation of three-wheeled robots cooperatively carrying an overhead object in unknown environments. Based on the divide-and-conquer technique, this article proposes a stage-by-stage evolutionary obstacle boundary following (OBF) fuzzy control of each of the three robots through multiobjective continuous ant colony optimization. In the first stage, a set of evolutionary nondominated fuzzy controllers (FCs) for a single robot (a leader robot) in the execution of the OBF behavior is learned. In the second stage, a follower robot is controlled by two evolutionary FCs in combination with a switched compensation FC so that the leader and follower robots can cooperatively transport an object while executing the OBF behavior along obstacles containing corners with right angles. In the third stage, the third robot functions as an accompanying robot and is learned to enter into a predicted triangular formation with the leader-follower robots to transport a larger object while executing the OBF behavior. In the navigation of the three object-transportation robots, a new cooperative behavior supervisor is proposed to coordinate the learned OBF behavior and a target seeking behavior. Successful navigations in simulations and experiments verify the effectiveness of the multistage evolutionary fuzzy control approach and navigation scheme.

From catalyst to process: bridging the scales in modeling the OCM reaction

Process simulations for catalyzed reactions generally do not incorporate model equations based on the fundamentals of catalyst and reactor configuration. Yet, doing so could significantly enhance the reliability of predictions and designs. An easy-to-use solution to integrate catalyst-dependent kinetics into industrially-relevant reactor models within the environment of a process simulator is proposed and illustrated step-by-step for the Oxidative Coupling of Methane (OCM). A multi-stage adiabatic configuration with intermediate cooling and distributed oxygen feed is selected as case study. Results for three different OCM catalysts (Sn-Li/MgO, NaMnW/SiO2, Sr/La2O3) revealed that a multi-stage configuration can be beneficial in terms of methane conversion and C2+ yield compared to a single stage. Remarkably, the addition of multiple stages led to more significant increases in yield for the more active but less selective Sr/La2O3 catalyst. For this catalyst, the impact of oxygen feed in the successive stages on the C2+ selectivity was found negligible. This was rationalized via a microkinetic contribution analysis of the prevailing oxidation routes, i.e. of methane (primary) and ethylene (consecutive). This case study highlights the importance of catalyst-tailored process evaluations of different scenarios for the industrial implementation of a complex chemical reaction such as OCM.

직렬 다단 전극 구성에 따른 전계 분포와 이온풍 특성

Ionic wind propulsion system has less noise and is easier to miniaturize and has higher power ratio than the existing propulsion system. However, the amount of ionic wind that can be generated is small to apply as a single propulsion device. So, that is used as auxiliary propulsion device. In this paper, to improve maximum ionic wind speed which is limited by the breakdown voltage, the corona electrodes and induction electrodes were configured in series and the spacing between the primary and secondary corona electrodes was adjusted. Superposition of electric fields in series multi-stage configuration is increase rear electric fields strength. However, when the gap was smaller than a specific value, the electric field from the secondary corona electrode to the primary induction electrode was strengthened, thereby electric field strength of the front portion was greatly weakened. When the gap became more than a certain value, the decrease in electric field strength was saturated. So, ionic wind speed was measured most strongly at the first saturation interval.

UNJUK KERJA COOL BOX BERBASIS THERMOELEKTRIK COOLER DENGAN SINGLE DAN MULTI-STAGE TERMOELEKTRIK

Thermoelectric technology works by converting thermal energy into electricity directly or preferably. Thermoelectric technology works by converting thermal energy into electricity directly or preferably. Theuse of thermoelectric as a cooler in cool box systems has been extensively studied. The thermoelectric cool ability can be achieved depending on the design of a good system. Therefore, this study aims to determine the performance of thermoelectric cooler cool box based on single and multi stage. Tests carried out using cool boxes of dimensions of 31 cm x 19 cm x 24 cm witha thickness of 3 cm and with the TEC1 12706 module. The voltage used in each configuration is 12 Volts. Temperature data readings on laptops using DAQNavi_SDK data logger connected to type K thermocouples. The result showed the multi stage configuration reached a room temperature of around 19.3 oC and 21.8 oC for single stage. Meanwhile, the multi stage configuration COP value is 1.36 and with a single stage configuration is0.88. It can be concluded that the thermoelectric configuration has an influence on the performance of the cool box system.&#x0D; Keywords: Cool box, Thermoelectric module, Multi stage, single stage, COP

Analysis, Design and Implementation of a Fully Integrated Analog Front-End for Microwave RFIDs at 5.8 GHz to Be Used With Compact MIMO Readers

In this paper we present the system and circuit level analysis and feasibility study of applying microwave Radio Frequency Identification (RFID) systems with multipleinput multiple-output (MIMO) reader technology for tracking machining tools in multipath fading conditions of production environments. In the proposed system the MIMO reader interrogates single-antenna tags, and a high RFID frequency of 5.8 GHz is chosen to reduce the size of the reader's antenna array. According to the requirements dictated by the performed system analysis at 5.8 GHz, a low power fully integrated analog frontend (AFE) is designed and fabricated in a standard 65-nm CMOS technology for low power passive transponders. Performance of the Differential Drive Rectifier (DDR) topology as the core of the energy harvesting unit is investigated in detail. A multi-stage DDR power scavenging unit is dimensioned to provide a 1.2 V rectified voltage for 20-30 kQ load range, with a high power conversion efficiency (PCE) for high frequency and low input power level signals. The rectified voltage is then converted to a 1 V regulated voltage for the AFE and the baseband processor with 30 to 50 μW of estimated power consumption. Transistors with standard threshold voltage (VT) have been used for implementation. Measurements of the fabricated multi-stage configuration of the circuit show a maximum PCE of 68.8% at -12.46 dBm, and an input quality factor (Q-factor) of approximately 10. Amplitude-shift keying (ASK) demodulator and backscattering modulator with 80% modulation index, operating according to EPC-C1G2 protocol are applied for data transfer. The AFE consumes less than 1 μW in the reading mode. The AFE tag chip is 0.55 × 0.58 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Highly sensitive multi-stage terahertz parametric detector.

In this Letter, we developed a high-sensitivity multi-stage terahertz (THz)-wave parametric detection system that operates at room temperature. This detection system has high sensitivity over a wide wavelength range through upconversion of a THz wave to near-infrared light. The broadband noise associated with parametric generation limited the detection sensitivity in the previous setup; however, in the multi-stage configuration using multiple LiNbO3 crystals, the THz parametric detection sensitivity was improved by spatially eliminating the broadband noise using an iris between the former and latter stages. With this improvement, the minimum detectable sensitivity at 1.05 THz approached 130 zJ (zJ=10-21J), which is equivalent to 90 photons or less. Furthermore, by combining this detector with an injection-seeded THz-wave parametric generator, which is a high-power, tunable THz-wave source, the THz-wave measurement system achieved a maximum dynamic range of 125 dB.

Forward osmosis and pressure retarded osmosis process modeling for integration with seawater reverse osmosis desalination

Osmotically driven membrane processes such as forward osmosis and pressure retarded osmosis may hold key advantages when integrated with seawater reverse osmosis to form hybrid FO-RO and RO-PRO systems. In this work, module-scale modeling of these two processes was improved by accurately representing the features of a spiral-wound membrane. The model captures important characteristics such as the cross-flow stream orientation, membrane baffling, and channel dimensions unique to spiral-wound membranes. The new module-scale model was then scaled to the system-level to compare various system designs for FO-RO and RO-PRO systems, most notably, a multi-stage recharge design was defined. Results indicate that the multi-stage recharge design leads to an increase in wastewater utilization, as high as 90%, when compared to the single-stage designs. Additionally, the multi-stage recharge configuration can increase the specific energy recovery of pressure retarded osmosis by over 75%. The multi-stage recharge design is found to be not only advantageous but may be also necessary to the integration of osmotically driven membrane processes with seawater reverse osmosis.

A framework for automated multi-stage and multi-step product configuration of cyber-physical systems

Product line engineering (PLE) has been employed to large-scale cyber-physical systems (CPSs) to provide customization based on users’ needs. A PLE methodology can be characterized by its support for capturing and managing the abstractions as commonalities and variabilities and the automation of the configuration process for effective selection and customization of reusable artifacts. The automation of a configuration process heavily relies on the captured abstractions and formally specified constraints using a well-defined modeling methodology. Based on the results of our previous work and a thorough literature review, in this paper, we propose a conceptual framework to support multi-stage and multi-step automated product configuration of CPSs, including a comprehensive classification of constraints and a list of automated functionalities of a CPS configuration solution. Such a framework can serve as a guide for researchers and practitioners to evaluate an existing CPS PLE solution or devise a novel CPS PLE solution. To validate the framework, we conducted three real-world case studies. Results show that the framework fulfills all the requirements of the case studies in terms of capturing and managing variabilities and constraints. Results of the literature review indicate that the framework covers all the functionalities concerned by the literature, suggesting that the framework is complete for enabling the maximum automation of configuration in CPS PLE.

Hybrid membrane process for post-combustion CO2 capture from coal-fired power plant

Post-combustion CO2 capture is a promising way to reduce CO2 emissions at the coal-fired power plants. Even though several studies have been conducted regarding a wide variety of CO2 capture techniques, gas separation membrane process has shown potential as an energy-efficient, low-cost CO2 capture option. However, most of the previous researches focused only on CO2-selective membrane, and there's limited literature about the application of N2-selective membrane.In this study, both CO2-selective and N2-selective membranes are considered and relevant issues regarding the CO2-selective membrane, such as pressure ratio, attainability, and multistage configuration, are studied and extended to the N2-selective membrane. Polaris® membrane is served as a typical CO2-selective membrane; on the other hand, membrane properties of N2-selective membrane with selectivity up to 200 are considered. Hybrid membrane process applying both CO2- and N2-selective membranes for capturing at least 90% CO2 from a typical 550 MW subcritical coal-fired power plant is designed, simulated and analyzed using Aspen Plus® simulation software. The optimization and economic analysis are also applied with the cost factor defined in this work, which is a comprehensive index to evaluate the applicability of the membrane, including permeance, membrane lifetime and membrane price. The results reveal the relationship between the optimal design variables and membrane properties. Moreover, the selectivity-limited region is identified, which leads to two different dominant strategies for the cost reduction in a different region, either by the increase in selectivity or the reduction of the cost factor.

Current utilization in electrodialysis: Electrode segmentation as alternative for multistaging

Electrodialysis (ED) is a membrane-based desalination technology that uses an electric field to force the migration of ions through ion-selective anion and cation exchange membranes. Salt water is highly conductive but during this desalination process, the produced water becomes more dilute and therefore less conductive. This effect causes a non-homogeneous current distribution, making the desalination performance less efficient in the direction of the flow. To mitigate this, we experimentally compare two configurations for different current distribution regimes, voltages and feed flow velocities: a fully separated system of multiple laboratory-scale ED stacks, i.e. a multistage ED, and a segmented electrode system that consists of one stack with multiple separated electrodes.The segmented electrode showed low voltage and higher desalination degree compared to multistage for operation at uniform current. For non-uniform current, no difference in efficiency was observed. For low voltage operation the segmented electrode showed, due to current redistribution, a higher desalination degree compared to the multistage ED configuration. To reach drinking water quality, a multistage operated at a potential difference of at least 4 V was necessary. The work demonstrates that electrode segmentation in ED can be effective for bulk desalination.