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Meccanica

, Volume 24, Issue 4, pp 235–248 | Cite as

Some considerations on the constant stress disc profile

  • Giancarlo Genta
Article

Summary

The main characteristics and applications of constant stress discs in turbine and flywheel technologies are summarized. The problem of the disc-shaft connection and that of achieving a levelled stress distribution in pierced discs in thoroughly discussed.

Many solutions to the latter problem are presented, noting that their practical interest is limited by the plane stress state assumption on which they are based.

A new approach to the optimization of the disc is then proposed. It allows to obtain disc profiles which, although not leading to a completely levelled stress distribution, show very good characteristics both for the construction of turbine discs and flywheels.

Some considerations on thermal stressing and on prestressing due to overspeeding are also included.

Keywords

Stress State Mechanical Engineer Civil Engineer Thermal Stress Stress Distribution 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

a

constant defining the profile

a, b, c, d

parameters defined in the text

e

energy

h

axial thickness

m

mass

n

number of blades, number of terms of a series

r

radius

B

constant defining the profile of constant stress discs

E

Young's modulus

K

shape factor

T

temperature

α

thermal expansion coefficient, thickness ratio

β

ratio between inner and outer radius (β=r i /r o )

v

Poisson's ratio

ξ

velocity factor

ρ

density

σ

stress

χ

non-dimensional radius (χ=r/r o )

ω

angular velocity

Subscripts

b

blades, ballast, bursting speed

c

circumferential, center

e

equivalent

h

hub

i

inner radius

m

maximum operating speed

o

outer radius

p

speed at which plasticization starts

r

radial, rim

y

yield

Sommario

Dopo aver descritto in sintesi le principali caratteristiche ed applicazioni dei dischi di uniforme resistenza per la realizzazione di dischi di turbina e di volani, vengono discussi in dettaglio i problemi relativi al collegamento tra dischi ed albero ed all'ottenimento di stati di tensione costanti in dischi forati.

Vengono presentate alcune soluzioni a quest'ultimo problema, sottolineando però il low scarso interesse pratico a causa della scarsa applicabilità dell'ipotesi di stato di tensione piano su cui esse sono basate.

Per superare tale difficoltà viene proposto un nuovo approccio al problema, che permette di offenere profili che pur non dando luogo ad uno stato di tensione rigorosamente costante, hanno caratteristiche adatte alla realizzazione sia di dischi di turbina che di volani.

A conclusione del lavoro vengono riportate alcune considerazioni su profili adatti a dischi soggetti a gradienti termici e sull'ottenimento di opportuni stati dl coazione mediante rotazione in sovravelocità.

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References

  1. [1]
    Benvenuto E.,La scienza delle costruzioni e il suo sviluppo storico, Sansoni, Firenze, 1981.Google Scholar
  2. [2]
    Stodola A.,Dampf- und gas-turbinen, Springer, Berlin, 1924.Google Scholar
  3. [3]
    Belluzzo G.,Le turbine a vapore ed a gas, Hoepli, Milano, 1905.Google Scholar
  4. [4]
    Belluzzo G.,Le turbine a vapore, Hoepli, Milano, 1923.Google Scholar
  5. [5]
    De Silva B.M.E.,The Application of Nonlinear Programming to the Automated Minimum Weight Design of Rotating Discs, in ≪Optimization≫, edited by R. Fletcher, Academic Press, New York, 1969, pp. 115–150.Google Scholar
  6. [6]
    Seireg A., Surana K.S.,Optimum Design of Rotating Disks, Journ. of Eng. for Industry, Vol. 92, n. 1, 1970, pp. 1–10.Google Scholar
  7. [7]
    Sandgren E., Ragsdell K.M.,Optimal flywheel design with a general thickness form representation, Journ. of Mechanisms, Transm. and Aut. in Des., Vol. 105, 1983, pp. 425–433.Google Scholar
  8. [8]
    Lazzeri D.,Manuale di utilizzo del programma SIMPAT, AIC, Torino, 1988.Google Scholar
  9. [9]
    Giovannozzi R.,Costruzione di macchine, Vol. 2, Patron, Bologna, 1965.Google Scholar
  10. [10]
    Genta G.,Calcolo e progetto di macchine, Vol. 2, Levrotto & Bella, Torino, 1989.Google Scholar
  11. [11]
    Genta G.,Kinetic Energy Storage, Butterworths, Londra, 1985.Google Scholar
  12. [12]
    Manson S.S.,Determination of the elastic stresses in gas turbine discs, NACA Report 871, 1947.Google Scholar
  13. [13]
    Genta G.,On the optimum design of a steel flywheel for a hybrid city bus XX, I.E.C.E.C., Miami Beach, august 1985.Google Scholar
  14. [14]
    Johnson A.E.,Turbine discs for jet propulsion units, Aircraft Engineering, june 1956, pp. 187–195.Google Scholar
  15. [15]
    Levi F., Pizzetti G.,Fluage, plasticité, précontrainte, Dunod, Paris, 1951.Google Scholar
  16. [16]
    Johnson W., Mellor P.B.,Plasticity for mechanical engineers, Van Nostrand, London, 1962.Google Scholar
  17. [17]
    Millenson M.B.,Manson S.S.,Determination of stresses in gas turbine disks subjected to plastic flow and creep, NACA Reprot 906, 1950.Google Scholar

Copyright information

© Pitagora Editrice Bologna 1989

Authors and Affiliations

  • Giancarlo Genta
    • 1
  1. 1.Dipartimento di MeccanicaPolitecnico di TorinoItaly

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