Prediction of Spark Ignition Performance in an Industrial Gas Turbine Combustor

Abstract Spark ignition performance of an annular combustor has been analyzed using computational modeling approach. Main steps of this approach include: (1) LES of the combustor non-reacting flow field, (2) using time-averaged LES results in a stochastic code in order to identify probable propagation behavior of the flame front using Lagrangian particle tracking, and (3) repeating the computations by an engineering approach and prediction of the combustor lean light-off (LLO) limit. By using this approach, effects of the ignition system location and specifications, fuel type and composition, and operating conditions on the gas turbine ignition performance can be evaluated effectively. Corresponding author: [email protected] Proceedings of the European Combustion Meeting 2015 Introduction Ignition is the process of transferring a flammable mixture from the non-reacting state to the selfsustaining combustion. Ignition is a transient phenomenon in which a complex interaction of chemical and physical processes occurs. Ignition in a flammable environment can be achieved by two general methods: forced ignition and self-ignition. During the forced ignition, a small volume of the mixture is ignited by an external force and the flame spreads across the whole system if the flame propagation conditions exist. In self-ignition or auto-ignition process, there is no local ignition source and the whole mixture ignites simultaneously Currently, practical gas turbine engine ignition systems include spark ignition (electrical spark and laser-induced spark or LIS) and torch systems (including both flame and plasma torches) Different studies have shown that the spark ignition in an annular gas turbine combustor is conducted at three phases. At the first phase, with starting discharge process and through breakdown, arc discharge, and glow discharge stages a flame kernel with sufficient size and temperature forms. At the second phase, this flame core spreads and the continuous spread of the flame from this kernel fills the primary combustion zone o

“At ‘Amen Meals’ It’s Me and God” Religion and Gender: A New Jewish Women’s Ritual

New ritual practices performed by Jewish women can serve as test cases for an examination of the phenomenon of the creation of religious rituals by women. These food-related rituals, which have been termed ‘‘amen meals’’ were developed in Israel beginning in the year 2000 and subsequently spread to Jewish women in Europe and the United States. This study employs a qualitative-ethnographic methodology grounded in participant-observation and in-depth interviews to describe these nonobligatory, extra-halakhic rituals. What makes these rituals stand out is the women’s sense that through these rituals they experience a direct con- nection to God and, thus, can change reality, i.e., bring about jobs, marriages, children, health, and salvation for friends and loved ones. The ‘‘amen’’ rituals also create an open, inclusive woman’s space imbued with strong spiritual–emotional energies that counter the women’s religious marginality. Finally, the purposes and functions of these rituals, including identity building and displays of cultural capital, are considered within a theoretical framework that views ‘‘doing gender’’ and ‘‘doing religion’’ as an integrated experience

Mechanical recycling of polylactide, upgrading trends and combination of valorization techniques

The upcoming introduction of polylactides in the fractions of polymer waste encourages technologists to ascertain its valorization at the best quality conditions. Mechanical recycling of PLA represents one of the most cost-effective methodologies, but the recycled materials are usually directed to downgraded applications, due to the inherent thermomechanical degradation affecting its mechanical, thermal and rheological performance. In this review, the current state of mechanical recycling of PLA is reported, with special emphasis on a multi-scale comparison among different studies. Additionally, the applications of physical and chemical upgrading strategies, as well as the chances to blend and/ or composite recycled PLA are considered. Moreover, the different valorization techniques that can be combined to optimize the value of PLA goods along its life cycle are discussed. Finally, a list of different opportunities to nurture the background of the mechanical recycling of PLA is proposed, in order to contribute to the correct waste management of PLA wastes

Large-scale unit commitment under uncertainty: an updated literature survey

The Unit Commitment problem in energy management aims at finding the optimal production schedule of a set of generation units, while meeting various system-wide constraints. It has always been a large-scale, non-convex, difficult problem, especially in view of the fact that, due to operational requirements, it has to be solved in an unreasonably small time for its size. Recently, growing renewable energy shares have strongly increased the level of uncertainty in the system, making the (ideal) Unit Commitment model a large-scale, non-convex and uncertain (stochastic, robust, chance-constrained) program. We provide a survey of the literature on methods for the Uncertain Unit Commitment problem, in all its variants. We start with a review of the main contributions on solution methods for the deterministic versions of the problem, focussing on those based on mathematical programming techniques that are more relevant for the uncertain versions of the problem. We then present and categorize the approaches to the latter, while providing entry points to the relevant literature on optimization under uncertainty. This is an updated version of the paper "Large-scale Unit Commitment under uncertainty: a literature survey" that appeared in 4OR 13(2), 115--171 (2015); this version has over 170 more citations, most of which appeared in the last three years, proving how fast the literature on uncertain Unit Commitment evolves, and therefore the interest in this subject

Assessing the Scalability and Privacy of Energy Communities by Using a Large-Scale Distributed and Parallel Real-Time Optimization

In the context of the energy transition, energy communities are gaining increasing attention all over the world, in recent years. By participating in an energy community, prosumers may take a leading role in the energy transition and improve the self-consumption of renewable energy produced inside the community. Prosumers can carry out energy exchanges inside the energy community and provide ancillary services to the system operators, thus contributing to improve the efficiency and stability of the grid. A novel scalable, privacy-preserving, and real-time distributed parallel optimization is proposed to manage a large-scale energy community, considering energy exchanges inside the community according to the model of virtual self-consumption and the provision of ancillary services. The proposed method preserves the privacy of prosumers and allows the assessment of the impact of energy exchanges on the ancillary services provided by an energy community. Simulation results confirmed that the proposed method is superior in terms of privacy if compared with the equivalent centralized optimization and that it has a convergence rate higher than that of the splitting conic solver (SCS)

Coping with Chronic Illness

The program outlined in this workbook can help those who suffer from chronic medical conditions take better care of themselves while simultaneously relieving depression. Designed to be used in conjunction with visits to a qualified mental health professional, this workbook teaches strategies for maintaining a medical regimen, including how to set up a reminder system for taking medication, plan for getting to medical appointments on time, and how to communicate effectively with medical providers. It also provides guidance for following the advice of treatment providers, such as adhering to certain lifestyle and dietary recommendations. In addition to these self-care skills, it also provides direction on maximizing quality of life (QOL), including how to re-engage in pleasurable activities and use relaxation techniques and breathing exercises to help cope with stress and discomfort, as well as problem-solving to successfully deal with interpersonal or situational difficulties and change negative thought through adaptive thinking

Coping with Chronic Illness

The treatment outlined in this therapist guide is intended for people suffering from depression and living with chronic illnesses. As a result of their poor health, many individuals who are chronically ill become depressed and fail to maintain steady self-care routines. Using this guide, therapists can help clients with chronic illnesses to develop core skills and techniques that will enable them to take better care of themselves. The program incorporates a unique Life-Steps module that teaches strategies for keeping up with their medical regimens, including tips for remembering to take medications, getting to medical appointments on time, and communicating effectively with medical providers. Based on the principles of CBT, this guide provides therapists with overviews of adherence behaviours for select illnesses including cancer, HIV, diabetes, and hypertension, among others. It covers adherence skills, integrated with cognitive and behavioural strategies for managing depression such as managing pleasurable activities, adaptive thinking, problem-solving, and relaxation training. The guide concludes with suggestions on how clients can manage their illnesses and avoid relapse into behaviours that worsen their medical condition