Ramp-up Process Research Articles

Enhancing the load ramp-up capability of the subcritical CFB power unit by considering the evolution of internal stored energy

The substantial inertia of the boiler restricts the flexibility of circulating fluidized bed (CFB) power units. To enhance the load ramp-up capability of the CFB power unit, we proposed a novel control strategy considering the spatial-temporal evolution of its internal stored energy. A dynamic model of the subcritical CFB power unit with a capacity of 300 MW was developed, incorporating the mechanism and control modules. By analyzing the spatial-temporal evolution of the stored energy in bed material, flue gases, refractory materials, economizer, evaporation subsystem, superheater subsystem, reheater subsystem, and turbine subsystem, we identified that the over-utilization of chemical and thermal stored energy in the bed materials is the primary factor restricting load ramp-up, while the thermal stored energy of the economizer is suitable for further utilization. Under the optimized control strategy that utilizes deviations of stored energy per mass of bed materials as a feedforward mechanism, the deviations of the key operating parameters during the load ramp-up process are significantly reduced, and the load ramp-up rate of the subcritical CFB power unit can be improved from 2.0 % Pe/min to 3.0 % Pe/min.

Effective growth strategy of colloidal quantum dots with low defects and high brightness

Quantum dots (QDs) with an alloy shell (CdSe@ZnS/ZnS) are one of the most promising emitters for optoelectronic devices for their superior properties such as narrow full width at half maximum (FWHM), high color purity and tunable wavelength. However, the presence of lattice stresses during the internal growth of quantum dots can cause severe exciton bursts. Optimizing the ramp-up process during the core growth of quantum dots and rising the temperature when cladding with ZnS shells is an effective strategy for obtaining high-quality quantum dots. Besides, the stability of quantum dots is further modified by using 1-Octanethiol (OT) as ligands. Detailed analyses of the morphology, colloidal stability, and luminescence performance of QDs were represented. Finally, green CdSe@ZnS/ZnS QLEDs with prolonged carrier lifetimes and less defect state densities achieved peak luminescence at 361850 cd/m2 with a current efficiency (CE) of 33 cd/A. This work provides a better understanding of the relationship between defect state density and the performance of quantum dots for designing and fabricating high-performance light-emitting diodes.

Capacity Policy for an OEM under Production Ramp-Up and Demand Diffusion

This paper presents a study on capacity policy for an OEM, launching a new short life cycle consumer durable product, and undergoes a demand diffusion process and a production ramp-up process with learning. The demand/supply dynamic system is described by the Bass diffusion demand rate and time constant production rate. The mismatch of demand peak and production plateau creates challenges for balancing the interactive trajectories. Indivisible lumpy capacity increments in the production network exacerbate the difficulty. In conjunction with mathematical and graphical analysis and computation power, we model a discrete optimization model (running on CPLEX) to investigate “how the OEM should determine an optimal capacity size” and “when to market the new product and expand capacity” under various Bass parameters, which describe the behavior intensity of the innovation and imitation of new product consumers.

Improve Ramp-Up Performance on the Sewing Process in a Sports Shoe Factory Using 8-Disciplines and Lean Manufacturing

Purpose: The research aims to design a performance improvement framework for a new model of sports shoes to increase the ramp-up process time. Methodology/Approach: The approach used the problem-solving system of 8 disciplines, Single Minute Exchange Dies, Visual Management, and the Just In Time principle. Findings: By using the methods described above, the research findings will have a positive impact on the company. Model changeover time was reduced from 600 minutes to 102 minutes, and ramp-up time was reduced from 20 days to 2 days. Research Limitation/Implication: The limitation of this study was that only the CK2946 model was still done as a case study. The cost and other inhibiting factors were also not included in the discussion of this rump-up process. Originality/Value of paper: By integrating SMED, Just In Time, visual management, and using 8-Dicipline, the researcher developed a framework for improved performance for ramping up a new model of sports shoes.

A Well Flux Surveillance and Production Ramp-Up Method for Openhole Standalone Screen Completion

SummaryWell surveillance requires practical models to balance the reward of maximizing production with the risk of ramping up production too much, which damages the completion. In this paper we present a method to monitor and ramp up production for openhole standalone screen (OH-SAS) completion. The objective is to optimize production using pressure transient analyses to assess the completion impairment and failure risks during the production ramp-up process. The flux model incorporates filter-cake pinholes, which are formed from nonuniform deposition and cleanup of filter cake during drilling and completion operations. Pinholes cause concentrated fluxes and increase completion failure risks. The method comprises three components, which are (1) determine pinhole properties from laboratory tests, (2) relate completion pressure drop of production through pinholes to pressure transient analyses, and (3) distribute fluxes in the standalone screen wellbore. Examples are presented and show that the completion pressure drop as a function of flow rate is nonlinear and higher with pinholes than without pinholes. By not incorporating pinholes, operations can potentially limit ramp-up. Flux distribution examples show that the largest impingement or radial velocity is at the top section of screen. The axial annular flow velocity or scouring velocity is two orders of magnitude larger than the screen impingement velocity. An integrated flux surveillance method for OH-SAS completion is presented for field applications.

Well-Flux Surveillance and Ramp-Up Method for Openhole Standalone Screen Completion

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 201662, “A Well-Flux Surveillance and Ramp-Up Method for Openhole Standalone Screen Completion,” by Mehmet Karaaslan and George K. Wong, University of Houston, and Kevin L. Soter, SPE, Shell, et al., prepared for the 2020 SPE Annual Technical Conference and Exhibition, originally scheduled to be held in Denver, Colorado, 5-7 October. The paper has not been peer reviewed. Production and surveillance engineers need practical models to help maximize production while avoiding ramping up the well to an extent that the completion is damaged, causing well impairment or failure. The complete paper presents a well-flux surveillance method to monitor and ramp up production for openhole standalone screen (OH-SAS) completions that optimizes production by considering risks of production impairment and screen-erosion failure. Challenges of Increased Production vs. Well Failure The problem of increased production vs. the risk of well impairment or failure is a pressing problem for sand-control wells in deepwater, where projects tend to have a small number of high-rate wells. In such environments, any well impairments or failures greatly affect the project economics. Following unloading, well surveillance faces the critical step of ramping up to-ward the well’s designed peak rate for the first time when the actual well performance is uncertain. To reduce risk of well impairment or failure, surveillance information and models are needed to help make adjustments during the ramp-up process. Different models are available, from simple to complex and from small to large amounts of input data and computational efforts. Simple nonsurveillance models use field-derived operating limits of completion pressure drop and flow velocity or flux. They are non-surveillance models in the sense that no direct linkage of surveillance results to update flux calculations exists. Simple surveillance models use pressure transient analysis (PTA) results and completion information to evaluate changing well performance and adjust the ramp-up and long-term surveillance operations. The complex surveillance model evaluates well performance and adjusts well operations using probabilistic completion failure risks and coupled reservoir and completion simulations. These models mainly focus on cased-hole gravel pack and frac-pack applications. For openhole completions with sand control, the literature offers limited ramp-up surveillance references. The objective of the well-flux model described in the complete paper is to ramp up the well safely and optimize production using PTA results as surveillance inputs to calculate completion fluxes for well impairment or failure assessment. The method follows an approach presented in the literature.

Temperature dependent water transport mechanism in gas diffusion layers revealed by subsecond operando X-ray tomographic microscopy

The product water of polymer electrolyte fuel cells (PEFCs) has to pervade the gas diffusion layer (GDL) and can lead to shortages of educt gas diffusion pathways to the catalyst layer hence to significant performance losses. Here we report on efforts made to enable subsecond and submicron operando X-ray tomographic microscopy (XTM) over a wide range of cell operating temperatures. The short XTM scan times allow to quantify the contributions of capillary-fingering and phase-change-induced flow on the overall water transport inside the cathode GDL at two different cell operating temperatures of 40 °C and 80 °C during a current ramp-up process. The results suggest that phase-change-induced water transport dominates the initial increase of saturation levels at typical automotive PEFC operating temperatures of about 80 °C, whereas capillary-fingering driven transport dominates the development of saturation from the beginning to stagnating stage at 40 °C.

Production planning for a ramp-up process in a multi-stage production system with worker learning and growth in demand

In a response to changes in customer requirements and environmental dynamics, product lifecycles have become shorter and shorter over the last decades. As a result, production ramp-ups have become more frequent in many industries, and they now often account for a significant share of the entire product lifecycle. Due to the prominent role production ramp-ups play in the lifecycle of a product, efficient production ramp-ups are now an important determinant of business success. This work proposes a mathematical model for managing production ramp-ups in a serial multi-stage production system. In the scenario considered here, both the productivity of workers and demand increase over time until a steady-state phase is reached at the end of the ramp-up. The model proposed in this paper supports the assignment of workers to the different stages of the production system and the balancing of production and demand to ensure a smooth transition from the production ramp-up to steady-state production. The model is analysed in numerical experiments to illustrate its potential for managing the production ramp-up. Our experiments show that high learning rates can have drawbacks in terms of large inventories if learning is not aligned with demand growth and across production stages.

Agility and resource dependency in ramp-up process of humanitarian organizations

PurposeThe ramp-up in humanitarian logistics operations is a stage when the demand surges, often at the start of an emergency. In response, agility is a key strategy used by the humanitarian organizations (HOs). However, the HOs are constrained by their existing resources and have to respond in the ramp-up process under their resource dependency. The purpose of this paper is to develop a framework on agility-building strategies used by HOs for the ramp-up.Design/methodology/approachThis study applies both the dynamic capabilities perspective and resource dependence theory to humanitarian relief operations, and develops four testable propositions to explore the agility-building strategies of the HOs for the ramp-up process. A multiple-case study is conducted on six international HOs operating in Indonesia to verify them, in addition to an extensive literature search.FindingsThe case study shows that the human resource management, pre-positioning, standardization and supplier management of the HOs are all related to their resources and environment in the ramp-up process. The authors highlight the practical differences between the few super large, resource rich and centralized HOs with the second-tier HOs.Research limitations/implicationsGiven the small sample size and single country as the site of study, some findings may not be applicable to the other HOs or in other regions.Practical implicationsThe propositions could be applicable to other HOs operating under similar environments, and potentially to the commercial enterprises operating in a highly volatile environment with severe resource scarcity.Originality/valueThis study provides new insights into ramp-up operations and into how HOs build their agility and reduce their resource dependencies. Theoretically, the paper applies two established theories in the strategic management literature to a new field.

Managing resource dependencies in electric vehicle supply chains: a multi-tier case study

Purpose The purpose of this paper is to investigate dependencies that arise between companies during the ramp-up of production volume in the electric vehicle (EV) supply chain. Design/methodology/approach An inter-company case study method has been used. Data were collected via tours of manufacturing plants, workshops and interviews from multiple tiers in a supply chain, namely, a niche EV manufacturer, as well as two of its tier-one suppliers and five of its tier-two suppliers. Findings As production volumes increased, a more relational approach was found to be necessary in inter-company relationships. The authors’ research showed that key suppliers, in addition to providing the parts, pursued a supply chain orchestrator’s role by offering direct support and guidance to the niche EV manufacturer in designing and executing its development plans. Research limitations/implications The resource dependence theory (RDT) is used to analyse and explain the changing dependencies throughout the planning and execution of production ramp-up. Practical implications This study will help supply chain managers to better manage resource dependencies during production ramp-up. Originality/value This study explores dependencies during the early stages of the production ramp-up process in the EV sector, which is in itself in the early stages of evolution. RDT is used for the first time in this context. This study has moved beyond a simple dyadic context, by providing empirical insights into the actions taken by an EV manufacturer and its suppliers, towards a multi-tier supply chain context, to better manage resource dependencies.

Comparison of 2D simulation models to estimate the critical current of a coated superconducting coil

Superconductors have been being applied to a variety of large-scale power applications, including magnets, electric machines, and fault current limiters, because they can enable a compact, lightweight and high efficiency design. In applications such as those mentioned above, superconducting coils are always a key component. For example, in a superconducting electric machine, the superconducting coils are used to generate the main flux density in the air gap, which is significantly important for the energy conversion. It is the performance of the superconducting coils that plays an essential role in determining the performance of the device. However, the performance of a superconducting coil is limited by its critical current, which is determined by temperature and the magnitude and orientation of the magnetic field inside the superconductors. Hence, in-depth investigations to estimate the critical current of the superconducting coils are necessary before manufacturing. Available transient simulation models to estimate the critical current are through the H- and T-A formulations of Maxwell’s equations. Both methods consider the same current ramp-up process occurring in experiments. Besides these transient models, static simulations can also be used: a modified load-line method and the so-called P-model, which is based on the asymptotic limit of Faraday’s equation when time approaches infinity. To find the best way to calculate the critical current, the four methods are used to estimate the critical current of a double pancake superconducting coils and results are compared with experiments. As a conclusion, T-A formulation, P-model, and the modified load-line methods are recommended for estimating the critical current of the superconducting coils.

The role of temperature ramp-up time before barrier layer growth in optical and structural properties of InGaN/GaN multi-quantum wells

In InGaN/GaN multi-quantum wells (MQWs), a low temperature cap (LT-cap) layer is grown between the InGaN well layer and low temperature GaN barrier layer. During the growth, a temperature ramp-up and ramp-down process is added between LT-cap and barrier layer growth. The effect of temperature ramp-up time duration on structural and optical properties of quantum wells is studied. It is found that as the ramp-up time increases, the Indium floating layer on the top of the well layer can be diminished effectively, leading to a better interface quality between well and barrier layers, and the carrier localization effect is enhanced, thereby the internal quantum efficiency (IQE) of QWs increases surprisingly. However, if the ramp-up time is too long, the carrier localization effect is weaker, which may increase the probabilities of carriers to meet with nonradiative recombination centers. Meanwhile, more nonradiative recombination centers will be introduced into well layers due to the indium evaporation. Both of them will lead to a reduction of internal quantum efficiency (IQE) of MQWs.

Ramp-up Process Improvement Practices for Time-to-Market Reduction

The importance of the “Ramp-up bridge” covering the gap between product development and serial production, as well as the speed at which this bridge can be crossed, has increased, providing companies with a significant competitive advantage.However, a significant percentage of project aiming to introduce new products do not achieve their goals. [(60 percent of the automotive supplier ramp-up projects fail on either the technical, or the economic side (Bischoff, 2007)].The author explores the possible reasons, then makes suggestions regarding the support of successful ramp-up projects, through practical examples taken from the industry. Through the continuous improvement of ramp-ups, a new core competency can be achieved, with a decrease in time-to-market. This core competency is difficult to duplicate, and can provide an additional competitive advantage for companies manufacturing products with high technical complexity.

Principal component analysis and singular value decomposition used for a numerical sensitivity analysis of a complex drawn part

The numerical forecasting of car body construction processes is already being used in industry to provide support in the ramp-up process. However, long calculation times are stretching the finite element method (FEM) to the limit, in particular when analyzing the effect of the variation of an input variable on one or more dependent variables. Moreover, there is still a need for experienced users to separate relevant from irrelevant parameters and to determine their variation. This paper presents a method that makes it possible, based on stochastic experimental design (DOE) in combination with both principle component analysis (PCA) and singular value decomposition (SVD), to create mathematical models that separate relevant from irrelevant input variables and that represent the effect of individual variables on all part or assembly areas by means of a variance-based sensitivity analysis. The method is verified in a case study based on realistic front hood geometry. The study examines the deep-drawing process steps as well as the geometrical accuracy in a measuring device. It is shown that it is possible to represent the effects of the most important variables from these processes on the strain and geometry parameters of the car body part and to vary these, based on a model function, interactively.

Investigation of Multilevel Injector for Ramp-up Process in Vertical Well Using Steam Assisted Gravity Drainage Method

Steam assisted gravity drainage (SAGD) method for heavy oil exploitation using horizontal wells has been done and successful in the field. In the similar concept with SAGD using horizontal wells, vertical well SAGD has been developed as alternative method. This well consists of two strings where one is as a producer on the bottom and the other one is as an injector on the top. This investigation makes different distance between injector and producer perforations gradually. The aim of this research is to make optimization strategy on the vertical well SAGD. The sensitivities tested consist of injection rate and distance between producer and injector perforations. Analysis result reveals that the impact of multilevel injector will decrease cSOR and improve the production rate on the same injection rate. If the process is combined with multilevel injection rate, the result would offer the most favourable option. Furthermore, the longer distance between producer and injector perforations will cause longer restrained heat in reservoir so that the volume steam chamber will be bigger and drainage radius will be wider.

Speed of Internationalization of New Business Units: The Impact of Direct and Indirect Learning

To date, surprisingly little research has been devoted to speed, which is arguably one of the most important time-based dimensions of a firm’s internationalization process. We address this gap, focusing on the learning processes during internationalization of established MNEs’ new business units, in particular their accumulation of business knowledge and internationalization knowledge and the temporal order of their knowledge acquisition. We argue that new business units benefit from the corporate environment of the parent MNE into which they are born as this may enable them to acquire business knowledge and internationalization knowledge not only by means of direct learning but also by means of indirect learning. Thus, we hypothesize that (1) internationalization speed increases with new business units’ relatedness to their parent MNEs’ portfolio of businesses, (2) new business units will increasingly rely on indirect learning to obtain business knowledge as relatedness increases, and (3) that the positive effect of direct learning of internationalization knowledge decreases the more new business units have been relying on indirect learning to obtain business and internationalization knowledge during the ramp-up process. We examine the internationalization of 788 new business units of 90 established German MNEs and find support for our arguments.

A Game-Based Approach to Raise Quality Awareness in Ramp-Up Processes

Today's production systems are complex sociotechnical systems. Both technical challenges, as well as the integration of human employees with their diverse abilities, wants, and needs, must be considered. Due to a growing number of product variants, shorter lead times, and global supply chains, planning production systems is becoming increasingly difficult, both on the technical and human levels. The highly volatile and uncertain character of production systems is intensified by the growing complexity and need for results in shorter decision times for ramp-up management. To handle the increasing complexity, human decision makers must be adequately trained for the ramp-up period. Therefore, the influential factors and their magnitude from both the technical and the human perspective must be identified and understood. This knowledge can help to manage the complexity of ramp-up processes, reduce the disturbances within the processes, and strengthen their overall resilience against failures.To adequately understand the human and technical factors that relate to ramp-up processes, it's necessary to have an experimental framework. This framework should support the identification and quantification of sociotechnical factors, enabling practitioners and researchers to model suitable interventions. In this article, the authors propose, develop, and evaluate a business simulation game that serves as such an empirical framework. The game is furthermore suitable to train managers before the ramp-up process. The achieved performance in the business simulation game may be used to evaluate a person's suitability for the task and to identify individual training potential.

Lean Application to Manufacturing Ramp-Up: A Conceptual Approach

This article provides a theoretical overview of the concepts of lean and manufacturing ramp-up in an attempt to conceptualize the strategic areas in which lean philosophy and principles can be applied for continuous improvements. The application of lean principles during the final stage of a new product development process, that is, the ramp-up process, is a critical, early enabler of lean manufacturing.The manufacturing strategy literature conceptualizes a state of “leanness in operations,” which can consolidate both the concepts of lean and manufacturing ramp-up, providing a dual perspective. ing from the extant literature, the authors considered the competitiveness of manufacturing companies from two principal perspectives: the leanness of the ramp-up process and the new-value creation of quality managers. While much of the literature fails to acknowledge that the roots of lean actually lie in quality evolution and TQM, there is relatively sparse evidence on the subject of applying the lean philosophy to manufacturing ramp-up, so this study is an attempt to address this gap. This is achieved by providing a comprehensive outline of the two concepts and illustrating the areas in which mutual benefits can be drawn, as well as providing a conceptual framework for future studies in lean application to the manufacturing ramp-up process.

Shear history effect of magnetorheological fluids

The rheological properties of magnetorheological (MR) fluids are usually determined by particle structures and polarized particle interactions. However, the particle structures may undergo various evolutions at different shear states and history; this evolution leads to shear stress hysteresis. Therefore, the shear history effect of MR fluids was experimentally investigated in this study. In a shear rate ramp test, the shear stress at low shear rate was higher in the shear rate ramp-down process than in the shear rate ramp-up process. If the next shear test started after a rest time, the start shear stress decayed slowly and approached the original value of the first test when the interval was long enough. The MR fluids also displayed obvious hysteresis loops during the current ramp test. A high shear rate and magnetic field could reduce the shear history effect by accelerating particle structure evolutions, and then hysteresis decreased. This effect was ascribed to the evolution of particle structures during different test modes and durations, and the evolution is governed by interparticle interactions, viscous forces, and the Brownian motions of particles. These results indicated that the accuracy of the force control of MR fluids could be enhanced under high magnetic fields and high shear rates. Thus, these factors should be considered in MR actuator designs.

Improving the Ramp-Up Process of a Body-Construction Line by Numerical Supported Design of Clamping Devices and FEM Based Tolerance Prognosis

The use of FEM (finite element method) to assistant in ramp-up processes of car body construction lines is increasing, thanks to developments in recent years [1-3]. Car body manufacturing begins with sheet metal forming, while in subsequent steps the inner structures of the vehicle are assembled and connected to the outer skin by hemming. With reference to the current state of the art, there is no methodology which can reliably predict the dimensional accuracy of body parts through metal forming [4].Additionally, several methods to predict the distortion of joining and the dimensional effect of clamping during the assembly process were presented and validated [4-11]. Dimensional effects of the clamping process are basically the result of a deliberate alignment, other than the given values of construction to compensate dimensional inaccuracy of single parts from the body shop. These deliberate alignments are generally effected through a translation of clamps and pins in the clamping device. Until now, most of the methods of clamping and joining simulation presented have been verified using academic samples.In this report, the quality of forecasting in real problems during a ramp-up process will be verified and expanded. As part of a national project, co-funded by Sächsische Aufbaubank (SAB), the potential of FEM to assist in the ramp-up process were reviewed in a cooperative effort between Porsche Leipzig GmbH and Fraunhofer Institute for Machine Tools and Forming Technology (IWU). Furthermore, it will be shown that developed methods are able to represent the influence of deliberate positioning of clamps in complex samples. For the first time the quality of forecasting through the translation of locating pins is numerically and experimentally qualified.