Highly Loaded Axial Flow Compressors: History and Current Developments

1990 ◽  
Vol 112 (4) ◽  
pp. 567-578 ◽  
Author(s):  
A. J. Wennerstrom
Keyword(s):  
Mach Number ◽  
Axial Flow ◽  
Turbine Engines ◽  
Development Programs ◽  
Future Developments ◽  
1960S And 1970S ◽  
The 1960S ◽  
Very High ◽  
Made In ◽  
Axial Flow Compressors

This paper discusses approaches taken over many years to achieve very high loading levels in axial-flow compressors. These efforts have been associated predominantly with aircraft turbine engines. The objective has been to reduce the size and weight of the powerplant, to increase its simplicity and ruggedness, and, whenever possible, to reduce cost. In the introduction, some fundamentals are reviewed that indicate that increased work per stage can only be obtained at a cost of increased Mach number, increased diffusion, or both. The earliest examples cited are some ambitious development programs of the 1950s and 1960s. Some innovative schemes to increase diffusion limits are described that took place in the 1960s and 1970s. Major advancements in dealing with higher Mach number were made in the 1980s. Finally, a few thoughts directed toward potential future developments are presented.

Improved criteria for stall-free preliminary design of axial compressor of aero gas turbine engines

2018 ◽  
Vol 233 (9) ◽  
pp. 3286-3297 ◽  
Author(s):  
MR Aligoodarz ◽  
A Mehrpanahi ◽  
M Moshtaghzadeh ◽  
A Hashiehbaf
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Axial Compressor ◽  
Axial Flow ◽  
Design Criterion ◽  
Flow Coefficient ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Parameter Ranges ◽  
Axial Flow Compressors

A worldwide effort has been devoted to developing highly efficient and reliable gas turbine engines. There exist many prominent factors in the development of these engines. One of the most important features of the optimal design of axial flow compressors is satisfying the allowable range for various parameters such as flow coefficient, stage loading, the degree of reaction, De-Haller number, etc. But, there are some applicable cases that the mentioned criteria are exceeded. One of the most famous parameters is De-Haller number, which according to literature data should not be kept less than 0.72 in any stage of the axial compressor. A deep insight into the current small- or large-scale axial flow compressors shows that a discrepancy will occur among design criterion for De-Haller number and experimental measurements in which the De-Haller number is less than the design limit but no stall or surge is observed. In this paper, an improved formulation is derived based on one-dimensional modeling for predicting the stall-free design parameter ranges especially stage loading, flow coefficient, etc. for various combinations. It was found that the current criterion is much more accurate than the De-Haller criterion for design purposes.

scholarly journals Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part II—Analysis

2000 ◽  
Vol 123 (3) ◽  
pp. 446-452 ◽  
Author(s):  
F. F. Ehrich ◽  
Z. S. Spakovszky ◽  
M. Martinez-Sanchez ◽  
S. J. Song ◽  
D. C. Wisler ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Axial Flow ◽  
Turbine Engines ◽  
Jet Engines ◽  
Static Structure ◽  
Static Pressure Distribution ◽  
Eccentric Rotor ◽  
Unsteady Effects ◽  
Analytic Models ◽  
Axial Flow Compressors

An experimental and theoretical investigation was conducted to evaluate the effects seen in axial-flow compressors when the centerline of the rotor becomes displaced from the centerline of the static structure of the engine, thus creating circumferentially nonuniform rotor-tip clearances. This displacement produces unsteady flow and creates a system of destabilizing forces, which contribute significantly to rotor whirl instability in turbomachinery. These forces were first identified by Thomas (1958. Bull. AIM, 71, No. 11/12, pp. 1039–1063.) for turbines and by Alford (1965. J. Eng. Power, Oct., pp. 333–334) for jet engines. In Part I, the results from an experimental investigation of these phenomena were presented. In this Part II, three analytic models were used to predict both the magnitude and direction of the Thomas/Alford force in its normalized form, known as the β coefficient, and the unsteady effects for the compressors tested in Part I. In addition, the effects of a whirling shaft were simulated to evaluate differences between a rotor with static offset and an actual whirling eccentric rotor. The models were also used to assess the influence of the nonaxisymmetric static pressure distribution on the rotor spool, which was not measured in the experiment. The models evaluated were (1) the two-sector parallel compressor (2SPC) model, (2) the infinite-segment-parallel-compressor (ISPC) model, and (3) the two-coupled actuator disk (2CAD) model. The results of these analyses were found to be in agreement with the experimental data in both sign and trend. Thus, the validated models provide a general means to predict the aerodynamic destabilizing forces for axial flow compressors in turbine engines. These tools have the potential to improve the design of rotordynamically stable turbomachinery.

The nuts of'em

1996 ◽  
Vol 8 (3) ◽  
pp. 219-227
Author(s):  
Robin Kinross
Keyword(s):  
1960S And 1970S ◽  
The 1960S ◽  
Made In

The typographer Anthony Froshaug worked intermittently as a teacher in Britain and Germany, from the late 1940s through to the 1980s. He was unusual in bringing the experience of typesetting and printing to design teaching, and in his wide set of intellectual interests. Froshaug's contribution was a notable if somewhat subterranean element in the development of education in typography in Britain, especially in the steps towards its modernization that were made in the 1960s and 1970s.

Middlemen in Third-World Corruption: Implications of an Indian Case

1987 ◽  
Vol 39 (4) ◽  
pp. 508-535 ◽  
Author(s):  
Philip Oldenburg
Keyword(s):  
Third World ◽  
Political Change ◽  
Systematic Analysis ◽  
The Third ◽  
1960S And 1970S ◽  
The 1960S ◽  
The Third World ◽  
Made In

Corruption—like the weather—is a phenomenon people in the third world talk about a great deal, and, it would seem, do little about. Scholars of political change in the third world share this interest, but—although they are usually not expected to deal with corruption itself —they should move beyond the recounting of vivid anecdotes to a more systematic analysis of the problem. Steps in this direction were made in the 1960s and 1970s, but surprisingly little more work has been done since.

scholarly journals Boks w kadrze. Wybrane strategie inscenizacyjne w polskich filmach o boksie z lat sześćdziesiątych i siedemdziesiątych XX wieku

2020 ◽  
Vol 27 (36) ◽  
Author(s):  
Dominik Wierski
Keyword(s):  
Great Time ◽  
The World ◽  
1960S And 1970S ◽  
The 1960S ◽  
Insight Into ◽  
Made In

In his article, Dominik Wierski analyses and interprets selected staging strategies in Polish films about boxing. The films cited in the text were made in the 1960s and 1970s. It was a dynamic period in Polish cinematography, but also a great time for Polish boxing. The author wonders how filmmakers showed space related to boxing - training rooms, changing rooms, stands and the boxing ring. Selected films, belonging to the most important examples of Polish filmmakers’ insight into the world of boxing, are analyzed in the terms of their use of colors, sound, camera travel, rhythm and pace etc. The purpose of the text is to answer the question of whether Polish films of the ‘60s and ‘70s developed an integral way of discussing boxing and showing its most characteristic spaces.

Low Aspect Ratio Axial Flow Compressors: Why and What It Means

1989 ◽  
Vol 111 (4) ◽  
pp. 357-365 ◽  
Author(s):  
A. J. Wennerstrom
Keyword(s):  
Aspect Ratio ◽  
Mechanical Design ◽  
Axial Flow ◽  
Early Years ◽  
Turbine Engine ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Design Systems ◽  
The 1960S ◽  
Axial Flow Compressors

One of the more visible changes that has occurred in fans and compressors for aircraft turbine engines that have entered development since about 1970 has been a significant reduction in the aspect ratio of the blading. This has brought with it a greatly reduced engine parts count and improved ruggedness and aeroelastic stability. This paper traces the evolution of thinking concerning appropriate aspect ratios for axial flow compressors since the early years of the aircraft turbine engine. In the 1950’s, moderate aspect ratios were favored for reasons of mechanical design. As mechanical design capability became more sophisticated, several attempts were made, primarily in the 1960s, to employ very high aspect ratios to reduce engine size and weight. Four of these programs are described that were largely unsuccessful for both mechanical and aerodynamic reasons. After 1970, the pendulum swung strongly in the other direction and designs of very low aspect ratio began to emerge. This has had a significant impact on compressor design systems, and a number of the ways in which design systems have been affected are discussed. Some concluding remarks are made concerning the author’s opinion of trends in the near future in aerodynamic design technology.

CONSTRAINTS, OPPORTUNITIES, AND THE DECISION TO PURSUE BUSINESS OWNERSHIP

2013 ◽  
Vol 11 (2) ◽  
pp. 233-252 ◽  
Author(s):  
Timothy Bates ◽  
Stephen Tuck
Keyword(s):  
Black Business ◽  
Business Community ◽  
Business Ownership ◽  
Opportunity Structures ◽  
Self Employment ◽  
Personal Services ◽  
Black Entrepreneurs ◽  
1960S And 1970S ◽  
The 1960S ◽  
Made In

AbstractThe choice between working as an employee and owning a business is shaped by constraints and opportunities. Among African Americans, understanding why the entrepreneurial path is chosen requires evaluating not only the relative importance of constraints pushing workers toward self-employment versus opportunities pulling entrants into firm ownership, but, more fundamentally, the changing opportunity structures shaping occupational choices. This study focuses on the 1960s and 1970s period when specific constraints historically limiting entrepreneurial alternatives began to change dramatically. Findings indicate that expanding opportunities sharply altered the industry composition of the Black business community.Because economists view the decision to enter into business ownership as an exercise in freedom of choice made on the basis of one’s preferences, they tend not to appreciate that these decisions are made in specific socio-economic contexts and that changes in context matter. Facing altered opportunity structures, prospective Black entrepreneurs have often chosen to abandon fields offering low remuneration—particularly personal services—entering instead into higher yielding fields where creation of viable firms requires investment of capital by owners possessing appropriate expertise. This transformation has remolded the stagnant business community of the mid-1960s into a profoundly different, more dynamic one.

scholarly journals Cronología histórica de la quiropterología en Nicaragua

2019 ◽  
Vol 9 (2) ◽  
pp. 1 ◽  
Author(s):  
Arnulfo Medina-Fitoria ◽  
José G. Martínez-Fonseca
Keyword(s):  
21St Century ◽  
Late Nineteenth Century ◽  
Historical Account ◽  
Late Nineteenth ◽  
Siglo Xix ◽  
1960S And 1970S ◽  
The 1960S ◽  
Siglo Xx ◽  
Second Period ◽  
Made In

ResumenEn este artículo describimos cronológicamente 182 años de investigación chiropterológica que atribuyen 110 especies en Nicaragua; desde la primeracolecta registrada en 1837 hasta la última publicación hecha en 2019. Estos trabajos fueron hechos en su totalidad por extranjeros hasta finalesdel siglo pasado, con una importante participación de investigadores nacionales a partir del siglo XXI. Determinamos tres épocas principales de exploración y cuyo auge ha dependido de las situaciones sociopolíticas del país. La primera seextendió de finales del siglo XIX hasta principios del siglo XX, con un segundo periodo durante las décadas de 1960 y 1970 y un tercer período que transcurre a lo largo del siglo XXI. En total recopilamos y analizamos 93 publicaciones científicas, las cuales datamos y ordenamos según su fecha de publicación. El recuento histórico reconoce a naturalistas y científicos nacionales y extranjeros que han contribuido al conocimiento de los murciélagos del país, donde se resaltan algunas de las obras más significativas para el desarrollo de la mastozoología en Nicaragua.Palabras clave: Especies, localidades, murciélagos, publicaciones. AbstractWe chronologically describe 182 years of chiropterological research, attributing 110 species in Nicaragua; from the first collection recorded in 1837 untilthe last publication made  in 2019; these works were made entirely by foreigners until the end of the last century, with an important participation of nationalresearchers from the 21st century. We determined three main periods of exploration and whose duration has depended on the socio-political situationsof the country. The first extended from the late nineteenth century to the early twentieth century, with a second period during the 1960s and 1970s; and athird period that runs throughout the 21st century. In total we collect and analyze 93 reports, which we date and order according to their publication date.The historical account recognizes national and foreign naturalists and scientists who have contributed to the knowledge of the country’s bats, highlighting some of the most significant works.Key words: Bats, localities, publications, species.

scholarly journals The Individual and Contemporary in Yuliy Raizman's Late Work

2011 ◽  
Vol 3 (3) ◽  
pp. 144-153
Author(s):  
Artyom Olegovich Sopin
Keyword(s):  
Late Work ◽  
1960S And 1970S ◽  
The 1960S ◽  
The Individual ◽  
Made In

The article examines the films made in the 1960s and 1970s by the filmmakers who became popular in the 1920s and 1930s. Some particular aspects of their adaptation to the new means of artistic expressiveness and adherence to certain themes are analyzed as exemplified by the work of Yuliy Raizman who collaborated with screenwriter Ye. I. Gabrilovich, namely, by their mutual films Your Contemporary (1967), A Strange Woman (1977) and Raizman's Courtesy Call (1972).

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