Gas Turbines for Marine Applications

Gas turbines have been established as the main power plant for all medium to large aircraft propulsions due to their superior power-to-weight ratio. They also have a significant and growing share in the power-generation sector as a result of the relatively low initial cost, short installation time, high efficiency when operated in combined cycle configurations, and low emissions compared to other fossil fuel power plants. However, their share in the marine propulsion sector is very small because of the more economically viable well-established diesel engine systems. Gas turbines have lower efficiency and poor part load performance. They are however favored when space and weight are at a premium or when high speed is required. It is conceivable that their use may increase, as emission restrictions get tougher. This article aims at giving an overview of gas turbine technology aimed at ship propulsion. Future prospects of carbon neutral zero emissions gas turbine systems are also explored

Return to Play: Impact of Urbanicity and Socioeconomic Status on Parents’ Attitudes Regarding Their Children\u27s Play and Sport During the COVID-19 Pandemic

The COVID-19 pandemic has had a profound impact on the daily routines of parents and children. The primary aim of this study was to explore the influence of socioeconomic status (SES) and urbanicity on parents’ attitudes toward their children’s active play opportunities 6 months and 1.5 years into COVID-19. The secondary objective was to explore how parents’ attitudes at 6 months related to the structured and unstructured play opportunities that children returned to 1 year later, while moderating the effects of SES and urbanicity. A sample of 239 Ontario parents of children (\u3c 12) completed two online surveys (August – December 2020; 2021). In general, parents in communities with urban features (e.g., densely populated areas), single-parents, full-time employed parents, and parents of lower-income were more hesitant to return their children to active play during the pandemic. Findings from this work highlight SES and urbanicity disparities that continue to exist during COVID-19

Effect of Capacity Building Interventions on Classroom Teacher and Early Childhood Educator Physical Activity and Fundamental Movement Skills Related Self-efficacy, Knowledge, and Attitudes: A Systematic Review and Meta-Analysis

Generalist teachers and early childhood educators (ECEs) play an important role in promoting physical activity and fundamental movement skills in children. However, teachers face several barriers to promoting physical activity and fundamental movement skills including inadequate training and professional development. Therefore, this study aimed to determine the efficacy of capacity building interventions on teachers’ and ECEs’ physical activity and fundamental movement skills related knowledge, self-efficacy and attitudes. The search revealed 22 studies which reported on 25 unique samples. The most common capacity building intervention component implemented was training/professional development. The results of this study revealed that capacity building interventions are efficacious at improving teachers’ and ECEs’ physical activity related self-efficacy, knowledge, and attitudes. Pre-service teachers and ECEs should be provided training in physical activity and FMS as part of their degrees, and continual professional development and capacity building should be offered to in-service teachers and ECEs to promote physical activity and FMS in children

Generalised analysis of compensating balancing sleeves with experimental results from a scaled industrial turbine coupling shaft

The paper furthers the analysis of a recently proposed balancing methodology for high-speed, flexible shafts. This mechanism imparts corrective balancing moments, having the effect of\ud simulating the fixing moments of equivalent double or single encastre mounted shafts. This is shown to theoretically eliminate/nullify the 1st lateral critical speed (LCS), and thereby facilitate safe operation with reduced LCS margins. The paper extends previously reported research to encompass a more generalised case of multiple, concentrated, residual imbalances, thereby facilitating analysis of any imbalance distribution along the shaft. Solutions provide greater insight of the behaviour of the balancing sleeve concept, and the beneficial implications for engineering design. Specifically: 1) a series of concentrated imbalances can be regarded as an equivalent level of uniform eccentricity, and balance sleeve compensation is equally applicable to a generalised unbalanced distribution, 2) compensation depends on the sum of the applied balancing sleeve moments and can therefore be achieved using a single balancing sleeve (thereby simulating a single encastre shaft), 3) compensation of the 2nd critical speed, and to a lesser extent higher orders, is possible by use of two balancing sleeves, positioned at shaft ends, 4) the concept facilitates on-site commissioning of trim balance which requires a means of adjustment at only one end of the shaft, 5) the Reaction Ratio, RR, (simply supported/ encastre), is independent of residual eccentricity, so that the implied benefits resulting from the ratio (possible reductions in the equivalent level of eccentricity) are additional to any balancing procedures undertaken prior to encastre simulation. Analysis shows that equivalent reductions in the order of 1/25th, are possible. Experimental measurements from a scaled model of a typical drive coupling employed on an industrial gas turbine package, loaded asymmetrically with a concentrated point of imbalance, are used to support the analysis and conclusions

Off-design performance comparison between single and two-shaft engines: part 1 — fixed geometry

This paper describes an investigation into the off-design performance comparison of single and two-shaft gas turbine engines. A question that has been asked for a long time which gas turbine delivers a better thermal efficiency at part load. The authors, notwithstanding their intensive searches, were unable to find a comprehensive answer to this question. A detailed investigation was carried out using a state of the art performance evaluation method and the answer was found to be: It depends! In this work, the performance of two engine configurations is assessed. In the first one, the single-shaft gas turbine operates at constant shaft rotational speed. Thus, the shape of the compressor map rotational speed line will have an important influence on the performance of the engine. To explore the implications of the shape of the speed line, two single-shaft cases are examined. The first case is when the speed line is curved and as the compressor pressure ratio falls, the non-dimensional mass flow increases. The second case is when the speed line is vertical and as the compressor pressure ratio falls, the non-dimensional mass flow remains constant. In the second configuration, the two-shaft engine, the two-shafts can be controlled to operate at different rotational speeds and also varying relationships between the rotational speeds. The part-load operation is characterized by a reduction in the gas generator rotational speed. The tool, which was used in this study, is a 0-D whole engine simulation tool, named Turbomatch. It was developed at Cranfield and it is based on mass and energy balance, carried out through an iterative method, which is based on component maps. These generic, experimentally derived maps are scaled to match the design point of a particular engine before an off-design calculation is performed. The code has been validated against experimental data elsewhere, it has been used extensively for academic purposes and the research activities that have taken place at Cranfield University. For an ideal cycle, the single-shaft engine was found to be a clear winner in terms of part-load thermal efficiency. However, this picture changed when realistic component maps were utilized. The basic cycle and the shape of component maps had a profound influence on the outcome. The authors explored the influence of speed line shapes, levels of component efficiencies and the variation of these component efficiencies within the operating range. This paper describes how each one of these factors, individually, influences the outcome

Simulation of an Advanced Twin-Spool Industrial Gas Turbine

A full range mathematical model of the LM-1600 gas turbine has been developed, for future use in EHM studies. No data was available from the manufacturer other than sales brochures giving some design and off-design performance. The model was developed using generalized component characteristics and shows excellent agreement with field data from a pipeline operator."/jats:p" "jats:p"A new method has been developed for doing the matching calculations, starting from the turbine (hot) end rather than from the compressor operating point. This method permits solution on a PC, and can be used for studying the full range of operating conditions and the development of fault matrices

A proposed method for assessing the susceptibility of axial compressors to fouling

Although the overall effect of compressor fouling on engine performance has been recognized for many years, remarkably little has been published on the quantifiable effects. Mathematical modelling of compressors using stage stacking methods has recently been used for a systematic study of compressor fouling and earlier investigations led to an interest in the effects of engine size and compressor stage loading. This paper presents a proposed index showing the susceptibility of compressors to fouling, which could be useful in helping operators to determine cleanup intervals. Three engines of widely differing performance were used in developing this index and additional operator experience would be useful in confirming its validity