Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling

Arttu Heininen; Jussi Aaltonen; Kari Koskinen; Juha Huitula

doi:10.3384/ecp19162007

Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling

Arttu Heininen, Jussi Aaltonen, Kari Koskinen, Juha Huitula

Automation Technology and Mechanical Engineering

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › Scientific › peer-review

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Abstract

Most of all modern commercial and military aircraft have oleo-pneumatic shock absorbers in their landing gear. An oleo-pneumatic shock absorber consists of a gas charge and an oil fill. During the stroke oil is forced through orifices which provides damping, while the gas charge is compressed and acts as a spring by increasing the stiffness of the shock absorber. Typically, when the gas behaviour is modelled, the ideal gas law is used as the equation of state as this provides in most cases adequate fidelity with relatively light computational load. However, in a fighter aircraft, especially in naval service, the gas pressure inside a shock absorber raises too high during landing for the ideal gas assumption to be valid. Therefore, other well-established equations of state have been considered. These are Van der Waals, Redlich-Kwong-Soave, and Peng-Robinson equation of state. This paper presents a multi-physics simulation model of a two-chamber oleo-pneumatic shock absorber based on fundamental analytical equations. Using this model, the behaviour of the aforementioned equations of state are studied in two cases: quasi-static and dynamical compression. The simulation results are compared to laboratory measurements. This comparison verifies that the ideal gas law should not be used when modelling naval fighter aircraft shock absorbers.

Original language	English
Title of host publication	FT2019. Proceedings of the 10th Aerospace Technology Congress, October 8-9, 2019, Stockholm, Sweden
Editors	Ingo Staack, Petter Krus
Publisher	Linköping University Electronic Press
Pages	64-79
Number of pages	7
Volume	162
ISBN (Electronic)	ISSN: 1650-3740
ISBN (Print)	978-91-7519-006-8, ISSN: 1650-3686
DOIs	https://doi.org/10.3384/ecp19162007
Publication status	Published - 2 Oct 2019
Publication type	A4 Article in conference proceedings
Event	Aerospace Technology Congress - Duration: 8 Oct 2019 → …

Conference

Conference	Aerospace Technology Congress
Period	8/10/19 → …

Keywords

fighter aircraft
shock absorber
modelling
simulation

Publication forum classification

Publication forum level 0

Access to Document

10.3384/ecp19162007

ecp19162007Final published version, 2.12 MB

https://urn.fi/URN:NBN:fi:tuni-202203112482

Cite this

Heininen, A., Aaltonen, J., Koskinen, K., & Huitula, J. (2019). Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling. In I. Staack, & P. Krus (Eds.), FT2019. Proceedings of the 10th Aerospace Technology Congress, October 8-9, 2019, Stockholm, Sweden (Vol. 162, pp. 64-79). Linköping University Electronic Press. https://doi.org/10.3384/ecp19162007

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title = "Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling",

abstract = "Most of all modern commercial and military aircraft have oleo-pneumatic shock absorbers in their landing gear. An oleo-pneumatic shock absorber consists of a gas charge and an oil fill. During the stroke oil is forced through orifices which provides damping, while the gas charge is compressed and acts as a spring by increasing the stiffness of the shock absorber. Typically, when the gas behaviour is modelled, the ideal gas law is used as the equation of state as this provides in most cases adequate fidelity with relatively light computational load. However, in a fighter aircraft, especially in naval service, the gas pressure inside a shock absorber raises too high during landing for the ideal gas assumption to be valid. Therefore, other well-established equations of state have been considered. These are Van der Waals, Redlich-Kwong-Soave, and Peng-Robinson equation of state. This paper presents a multi-physics simulation model of a two-chamber oleo-pneumatic shock absorber based on fundamental analytical equations. Using this model, the behaviour of the aforementioned equations of state are studied in two cases: quasi-static and dynamical compression. The simulation results are compared to laboratory measurements. This comparison verifies that the ideal gas law should not be used when modelling naval fighter aircraft shock absorbers.",

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Heininen, A, Aaltonen, J , Koskinen, K & Huitula, J 2019, Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling. in I Staack & P Krus (eds), FT2019. Proceedings of the 10th Aerospace Technology Congress, October 8-9, 2019, Stockholm, Sweden. vol. 162, Linköping University Electronic Press, pp. 64-79, Aerospace Technology Congress, 8/10/19. https://doi.org/10.3384/ecp19162007

Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling. / Heininen, Arttu; Aaltonen, Jussi ; Koskinen, Kari et al.
FT2019. Proceedings of the 10th Aerospace Technology Congress, October 8-9, 2019, Stockholm, Sweden. ed. / Ingo Staack; Petter Krus. Vol. 162 Linköping University Electronic Press, 2019. p. 64-79.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › Scientific › peer-review

TY - GEN

T1 - Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling

AU - Heininen, Arttu

AU - Aaltonen, Jussi

AU - Koskinen, Kari

AU - Huitula, Juha

PY - 2019/10/2

Y1 - 2019/10/2

N2 - Most of all modern commercial and military aircraft have oleo-pneumatic shock absorbers in their landing gear. An oleo-pneumatic shock absorber consists of a gas charge and an oil fill. During the stroke oil is forced through orifices which provides damping, while the gas charge is compressed and acts as a spring by increasing the stiffness of the shock absorber. Typically, when the gas behaviour is modelled, the ideal gas law is used as the equation of state as this provides in most cases adequate fidelity with relatively light computational load. However, in a fighter aircraft, especially in naval service, the gas pressure inside a shock absorber raises too high during landing for the ideal gas assumption to be valid. Therefore, other well-established equations of state have been considered. These are Van der Waals, Redlich-Kwong-Soave, and Peng-Robinson equation of state. This paper presents a multi-physics simulation model of a two-chamber oleo-pneumatic shock absorber based on fundamental analytical equations. Using this model, the behaviour of the aforementioned equations of state are studied in two cases: quasi-static and dynamical compression. The simulation results are compared to laboratory measurements. This comparison verifies that the ideal gas law should not be used when modelling naval fighter aircraft shock absorbers.

AB - Most of all modern commercial and military aircraft have oleo-pneumatic shock absorbers in their landing gear. An oleo-pneumatic shock absorber consists of a gas charge and an oil fill. During the stroke oil is forced through orifices which provides damping, while the gas charge is compressed and acts as a spring by increasing the stiffness of the shock absorber. Typically, when the gas behaviour is modelled, the ideal gas law is used as the equation of state as this provides in most cases adequate fidelity with relatively light computational load. However, in a fighter aircraft, especially in naval service, the gas pressure inside a shock absorber raises too high during landing for the ideal gas assumption to be valid. Therefore, other well-established equations of state have been considered. These are Van der Waals, Redlich-Kwong-Soave, and Peng-Robinson equation of state. This paper presents a multi-physics simulation model of a two-chamber oleo-pneumatic shock absorber based on fundamental analytical equations. Using this model, the behaviour of the aforementioned equations of state are studied in two cases: quasi-static and dynamical compression. The simulation results are compared to laboratory measurements. This comparison verifies that the ideal gas law should not be used when modelling naval fighter aircraft shock absorbers.

KW - fighter aircraft

KW - shock absorber

KW - modelling

KW - simulation

U2 - 10.3384/ecp19162007

DO - 10.3384/ecp19162007

M3 - Conference contribution

SN - 978-91-7519-006-8

SN - ISSN: 1650-3686

VL - 162

SP - 64

EP - 79

BT - FT2019. Proceedings of the 10th Aerospace Technology Congress, October 8-9, 2019, Stockholm, Sweden

A2 - Staack, Ingo

A2 - Krus, Petter

PB - Linköping University Electronic Press

T2 - Aerospace Technology Congress

Y2 - 8 October 2019

ER -

Equations of State in Fighter Aircraft Oleo-pneumatic Shock Absorber Modelling

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