A Path Towards the Aerodynamic Robust Design of Low Pressure Turbines

2012 ◽  
Author(s):  
Francesco Bertini ◽  
Martina Credi ◽  
Michele Marconcini ◽  
Matteo Giovannini
Keyword(s):  
A Priori ◽  
Low Pressure ◽  
Major Effect ◽  
Quality Level ◽  
Operating Cycle ◽  
Manufacturing Defects ◽  
Reported Study ◽  
Definition Of ◽  
Configuration Module ◽  
Module Performance

Airline companies are continuously demanding lower-fuel-consuming engines and this leads to investigating innovative configurations and to further improving single module performance. In this framework the Low Pressure Turbine (LPT) is known to be a key component since it has a major effect on specific fuel consumption (SFC). Modern aerodynamic design of LPTs for civil aircraft engines has reached high levels of quality, but new engine data, after first engine tests, often cannot achieve the expected performance. Further work on the modules is usually required, with additional costs and time spent to reach the quality level needed to enter in service. The reported study is aimed at understanding some of the causes for this deficit and how to solve some of the highlighted problems. In a real engine, the LPT module works under conditions which differ from those described in the analyzed numerical model: the definition of the geometry cannot be so accurate, a priori unknown values for boundary conditions data are often assumed, complex physical phenomena are seldom taken into account, operating cycle may differ from the design intent due to a non-optimal coupling with other engine components. Moreover, variations are present among different engines of the same family, manufacturing defects increase the uncertainty and, finally, deterioration of the components occurs during service. Research projects and several studies carried out by the authors lead to the conclusion that being able to design a module whose performance is less sensitive to variations (Robust LPT) brings advantages not only when the engine performs under strong off-design conditions but also, due to the abovementioned unknowns, near the design point as well. Concept and Preliminary Design phases are herein considered, highlighting the results arising from sensibility studies and their impact on the final designed robust configuration. Module performance is afterward estimated using a statistical approach.

A Path Toward the Aerodynamic Robust Design of Low Pressure Turbines

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Francesco Bertini ◽  
Martina Credi ◽  
Michele Marconcini ◽  
Matteo Giovannini
Keyword(s):  
A Priori ◽  
Low Pressure ◽  
Major Effect ◽  
Service Research ◽  
Quality Level ◽  
Operating Cycle ◽  
Manufacturing Defects ◽  
Reported Study ◽  
Configuration Module ◽  
Module Performance

Airline companies are continuously demanding lower-fuel-consuming engines and this leads to investigating innovative configurations and to further improving single module performance. In this framework the low pressure turbine (LPT) is known to be a key component since it has a major effect on specific fuel consumption (SFC). Modern aerodynamic design of LPTs for civil aircraft engines has reached high levels of quality, but new engine data, after first engine tests, often cannot achieve the expected performance. Further work on the modules is usually required, with additional costs and time spent to reach the quality level needed to enter into service. The reported study is aimed at understanding some of the causes for this deficit and how to solve some of the highlighted problems. In a real engine, the LPT module works under conditions which differ from those described in the analyzed numerical model: the definition of the geometry cannot be so accurate, a priori unknown values for boundary conditions data are often assumed, complex physical phenomena are seldom taken into account, and operating cycle may differ from the design intent due to a nonoptimal coupling with other engine components. Moreover, variations are present among different engines of the same family, manufacturing defects increase the uncertainty and, finally, deterioration of the components occurs during service. Research projects and several studies carried out by the authors lead to the conclusion that being able to design a module whose performance is less sensitive to variations (robust LPT) brings advantages not only when the engine performs under strong off-design conditions but also, due to the abovementioned unknowns, near the design point as well. Concept and preliminary design phases are herein considered, highlighting the results arising from sensibility studies and their impact on the final designed robust configuration. Module performance is afterward estimated using a statistical approach.

scholarly journals Aerosol-based antimicrobial photoinactivation in the lungs: an action spectrum study

2021 ◽  
Author(s):  
Chiara Treghini ◽  
Alfonso Dell’Accio ◽  
Franco Fusi ◽  
Giovanni Romano
Keyword(s):  
Light Source ◽  
A Priori ◽  
Action Spectrum ◽  
Multidrug Resistant ◽  
Theoretical Modelling ◽  
Resistant Bacteria ◽  
Lung Infections ◽  
Killing Action ◽  
Definition Of

AbstractChronic lung infections are among the most diffused human infections, being often associated with multidrug-resistant bacteria. In this framework, the European project “Light4Lungs” aims at synthesizing and testing an inhalable light source to control lung infections by antimicrobial photoinactivation (aPDI), addressing endogenous photosensitizers only (porphyrins) in the representative case of S. aureus and P. aeruginosa. In the search for the best emission characteristics for the aerosolized light source, this work defines and calculates the photo-killing action spectrum for lung aPDI in the exemplary case of cystic fibrosis. This was obtained by applying a semi-theoretical modelling with Monte Carlo simulations, according to previously published methodology related to stomach infections and applied to the infected trachea, bronchi, bronchioles and alveoli. In each of these regions, the two low and high oxygen concentration cases were considered to account for the variability of in vivo conditions, together with the presence of endogenous porphyrins and other relevant absorbers/diffusers inside the illuminated biofilm/mucous layer. Furthermore, an a priori method to obtain the “best illumination wavelengths” was defined, starting from maximizing porphyrin and light absorption at any depth. The obtained action spectrum is peaked at 394 nm and mostly follows porphyrin extinction coefficient behavior. This is confirmed by the results from the best illumination wavelengths, which reinforces the robustness of our approach. These results can offer important indications for the synthesis of the aerosolized light source and definition of its most effective emission spectrum, suggesting a flexible platform to be considered in further applications.

Toward a Functional Definition of the A Priori

1944 ◽  
Vol 41 (6) ◽  
pp. 155
Author(s):  
Arthur Child
Keyword(s):  
A Priori ◽  
Definition Of

Subject of Economic Science

2015 ◽  
pp. 115-120
Author(s):  
D. Egorov
Keyword(s):  
Human Behavior ◽  
Classical Theory ◽  
Adam Smith ◽  
A Priori ◽  
Economic Science ◽  
The Public ◽  
Public Consciousness ◽  
Wealth Of Nations ◽  
Definition Of ◽  
The Relationship

Adam Smith defined economics as “the science of the nature and causes of the wealth of nations” (implicitly appealing – in reference to the “wealth” – to the “value”). Neo-classical theory views it as a science “which studies human behavior in terms of the relationship between the objectives and the limited funds that may have a different use of”. The main reason that turns the neo-classical theory (that serves as the now prevailing economic mainstream) into a tool for manipulation of the public consciousness is the lack of measure (elimination of the “value”). Even though the neo-classical definition of the subject of economics does not contain an explicit rejection of objective measures the reference to “human behavior” inevitably implies methodological subjectivism. This makes it necessary to adopt a principle of equilibrium: if you can not objectively (using a solid measurement) compare different states of the system, we can only postulate the existence of an equilibrium point to which the system tends. Neo-classical postulate of equilibrium can not explain the situation non-equilibrium. As a result, the neo-classical theory fails in matching microeconomics to macroeconomics. Moreover, a denial of the category “value” serves as a theoretical basis and an ideological prerequisite of now flourishing manipulative financial technologies. The author believes in the following two principal definitions: (1) economics is a science that studies the economic system, i.e. a system that creates and recombines value; (2) value is a measure of cost of the object. In our opinion, the value is the information cost measure. It should be added that a disclosure of the nature of this category is not an obligatory prerequisite of its introduction: methodologically, it is quite correct to postulate it a priori. The author concludes that the proposed definitions open the way not only to solve the problem of the measurement in economics, but also to address the issue of harmonizing macro- and microeconomics.

scholarly journals Development and Use of Machine-Learnt Algebraic Reynolds Stress Models for Enhanced Prediction of Wake Mixing in Low-Pressure Turbines

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
H. D. Akolekar ◽  
J. Weatheritt ◽  
N. Hutchins ◽  
R. D. Sandberg ◽  
G. Laskowski ◽  
...  
Keyword(s):  
Reynolds Stress ◽  
Gene Expression Programming ◽  
A Priori ◽  
Low Pressure ◽  
Navier Stokes ◽  
Flow Features ◽  
Turbulence Closures ◽  
Rans Models ◽  
Development Analysis ◽  
Stress Models

Nonlinear turbulence closures were developed that improve the prediction accuracy of wake mixing in low-pressure turbine (LPT) flows. First, Reynolds-averaged Navier–Stokes (RANS) calculations using five linear turbulence closures were performed for the T106A LPT profile at isentropic exit Reynolds numbers 60,000 and 100,000. None of these RANS models were able to accurately reproduce wake loss profiles, a crucial parameter in LPT design, from direct numerical simulation (DNS) reference data. However, the recently proposed kv2¯ω transition model was found to produce the best agreement with DNS data in terms of blade loading and boundary layer behavior and thus was selected as baseline model for turbulence closure development. Analysis of the DNS data revealed that the linear stress–strain coupling constitutes one of the main model form errors. Hence, a gene-expression programming (GEP) based machine-learning technique was applied to the high-fidelity DNS data to train nonlinear explicit algebraic Reynolds stress models (EARSM), using different training regions. The trained models were first assessed in an a priori sense (without running any RANS calculations) and showed much improved alignment of the trained models in the region of training. Additional RANS calculations were then performed using the trained models. Importantly, to assess their robustness, the trained models were tested both on the cases they were trained for and on testing, i.e., previously not seen, cases with different flow features. The developed models improved prediction of the Reynolds stress, turbulent kinetic energy (TKE) production, wake-loss profiles, and wake maturity, across all cases.

scholarly journals Governança corporativa e sensibilidade investimento-fluxo de caixa no Brasil

2019 ◽  
Vol 17 (2) ◽  
pp. 72
Author(s):  
Breno Augusto de Oliveira Silva ◽  
Daniel Ferreira Caixe ◽  
Elizabeth Krauter
Keyword(s):  
Corporate Governance ◽  
Cash Flow ◽  
A Priori ◽  
Investment Model ◽  
Quality Level ◽  
Financial Constraint ◽  
Publicly Traded Companies ◽  
Flow Sensitivity ◽  
Governance Practices ◽  
Cash Flow Sensitivity

This study aimed to investigate the investment-cash flow sensitivity for Brazilian companies with different degrees of financial constraint according to the quality level of their corporate governance practices. An investment model was estimated through GMM for a panel data of 248 Brazilian publicly traded companies, which were a priori classified in two groups of financial constraint degrees (high and low) according to the Corporate Governance Practices Index (IPGC). The results showed that the quality of corporate governance influences the investment-cash flow sensitivity, and this sensitivity is negative and significant only for firms with poor governance, classified with high financial constraint. Furthermore, it can be concluded that IPGC proved to be an interesting variable for a priori classification of companies and an important determinant of the investment-cash flow sensitivity to identify potentially financially constrained firms.

scholarly journals PROFESSIONAL COMPETENCE OF FUTURE SPECIALISTS IN INFORMATION AND COMMUNICATION TECHNOLOGIES: QR CODING IN STUDENT LEARNING

2019 ◽  
Vol 5 (57) ◽  
pp. 33-35
Author(s):  
A. Hafiiak ◽  
O. Shefer ◽  
E. Borodina ◽  
S. Alyoshin
Keyword(s):  
Information And Communication Technologies ◽  
Professional Competence ◽  
Communication Technologies ◽  
Point Of View ◽  
Quality Level ◽  
It Education ◽  
Information And Communication ◽  
Student Training ◽  
Definition Of

The article explores modern information and telecommunication technologies, which are the basis of information processes in education. The fundamentals of improving the quality of student training from the point of view of the development of a vocational education system are investigated. The authors explore the definition of an innovative educational environment. It is proved that professional IT education is the basis for improving its quality level and has certain advantages over other types of knowledge, providing flexibility due to modern technological features, including the use of QR coding information.

Functionalism and Stratification, Socio-Cultural Evolution and Revolution

2016 ◽  
pp. 107-130
Keyword(s):  
Middle Ages ◽  
Cultural Evolution ◽  
A Priori ◽  
Human Beings ◽  
Ibn Khaldun ◽  
Ex Nihilo ◽  
Definition Of ◽  
And Function ◽  
Political Economic

In the previous chapter we argued that the conception of creatio ex nihilo is the determinant of hierarchy and stratification in Judaism and Christianity; Islam teaches that God created divisions as a way for human beings to recognize each other. The metaphysical origin of sociality and the reality of tribal and clan structure are reflected in the Islamic conception of community, gamaat; on a larger scale it is called ummah. Members in Islamic ummah are set apart from non-Muslims. This is dissimilar to the ancient Judaic racial and ethnic symbiosis which came to be known as the “chosen people,” an early manifestation of stratification in monotheistic religions. Among the Muslim scholars of the Middle Ages, Ibn Khaldun approached the objective foundations of sociality, attending to an implicit conception of stratification by appropriating detached observational methods to explain the rise and fall of dynasties. Principally, his work demonstrates the possibility of synthetically a posteriori, based on his personal experience and analytical a priori by which he asserted that the rise and fall are part of the definition of all dynasties. However, since Ibn Khaldun's day, our notion of the objects of structure and function of societies requires that we distinguish many variables in order to understand Islamic societies – particularly the way that their stratification systems are affected by globalization, or their transition toward, or their opposition to modernity. Using geometry metaphorically, it is true that we have departed from Euclidian theorems with the advent of various geometries. Yet Euclidian geometry still has many functions, a point that amplifies the intersections of both Euclidian and non-Euclidian geometries. Notwithstanding the various intersections among political, economic, religious, cultural and social matrices that provide multiple logics to understand the operations of societies, the Khaldunic notion of rise and fall has survived to this day.

scholarly journals Water Levels Affect Nest Success of the Snail Kite in Florida: AIC and the Omission of Relevant Candidate Models

The Condor ◽  
2002 ◽  
Vol 104 (1) ◽  
pp. 208-215 ◽  
Author(s):  
Steven R. Beissinger ◽  
Noel F. R. Snyder
Keyword(s):  
Nest Success ◽  
A Priori ◽  
Information Criterion ◽  
Water Levels ◽  
Spatial Effects ◽  
Factors Affecting ◽  
Snail Kite ◽  
Water Conditions ◽  
Rostrhamus Sociabilis ◽  
Definition Of

Abstract Dreitz et al. (2001) analyzed the factors affecting nest success of the Snail Kite (Rostrhamus sociabilis) in Florida. They concluded that success was unrelated to water levels because Akaike's Information Criterion rated models with water-level terms as poor compared to other models. Their suite of candidate models, however, did not include models with area-specific differences in the way that water levels affect nest success. We believe that such differences should have been included among the a priori models examined, and that their best model is neither ecologically informative nor useful for management. Using the same statistical methods, we reanalyze Dreitz et al.'s data on nesting success from the five areas with sufficient years and nests for analysis (comprising 89% of their 1542 nests) and show that, when spatial effects of water levels are included, water levels have an important influence on nest success over the entire range of water levels, not just during low water conditions. Furthermore, Dreitz et al.'s definition of nesting attempts excluded nests found during the 10–21 day pre-laying period, when many nests fail. Thus, they overestimated nest success and underestimated the amount of nesting activity under low water conditions. Low water conditions occur relatively frequently throughout much of the kite's range, and under these conditions few kites nest and even fewer fledge young. The effects of low water extend well beyond nest success, causing many kites to forgo nesting altogether, shortening the breeding season, and decreasing the opportunity for multiple brooding. Los Niveles de Agua Afectan el Éxito de Nidos de Rostrhamus sociabilis en Florida: Criterio de Información de Akaike y la Omisión de Modelos Potenciales Relevantes Resumen. Dreitz et al. (2001) analizaron los factores que afectan el éxito de anidación de Rostrhamus sociabilis en Florida. Ellos concluyeron que el éxito no está relacionado con los niveles de agua porque según el Criterio de Información de Akaike, los modelos que incluían términos relacionados con el nivel de agua eran de poco valor en comparación con otros modelos. Sin embargo, entre los modelos evaluados no incluyeron aquellos con diferencias específicas de área en la manera en que los niveles de agua afectan el éxito de los nidos. Nosotros creemos que dichas diferencias han debido ser incluidas en los modelos evaluados a priori y que su mejor modelo no es ecológicamente informativo ni útil en términos de manejo. Utilizando los mismos métodos estadísticos, reanalizamos los datos de éxito de anidación de Dreitz et al. de las cinco áreas que tenían suficientes años y nidos para analizar (comprendiendo el 89% de sus 1542 nidos). Demostramos que cuando se incluyen los efectos espaciales de los niveles de agua, éstos tienen una influencia importante en el éxito de los nidos en todo el rango de niveles de agua (no sólo en condiciones de aguas bajas). Más aún, la definición de intentos de anidación empleada por Dreitz et al. excluyó a aquellos nidos encontrados durante el período de 10 a 21 días pre-postura, cuando muchos nidos fracasan. Por lo tanto, ellos sobreestimaron el éxito de los nidos y subestimaron la cantidad de actividad de anidación en condiciones de aguas bajas. Las condiciones de aguas bajas se presentan con relativa frecuencia en gran parte del rango de distribución de R. sociabilis. Bajo esas condiciones, pocos individuos anidan y aún menos crían polluelos exitosamente. Los efectos de aguas bajas se extienden más allá del éxito de los nidos, causando que muchos individuos totalmente renuncien a anidar, acortando la época reproductiva y reduciendo las oportunidades de tener múltiples nidadas.

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