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Research Papers

On the Transient of Pressure Waves in Ducts for Systems Operating in Industrial Automation

[+] Author and Article Information
Arcangelo Messina1

Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Monteroni, 73100 Lecce, Italyarcangelo.messina@unisalento.it

Giosué Rollo

Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Monteroni, 73100 Lecce, Italy

1

Corresponding author.

J. Dyn. Sys., Meas., Control 132(2), 021006 (Feb 03, 2010) (12 pages) doi:10.1115/1.4000652 History: Received January 30, 2008; Revised September 30, 2009; Published February 03, 2010; Online February 03, 2010

Within the frame of industrial automation, the mechanical power related to pneumatic actuator systems involves air flows along with mechanical component, such as valves, connecting tubes, cylinder chambers and possible linkages in order to finally actuate a specific objective. Gas dynamic of the air flowing into connecting ducts plays a fundamental role in the description of the global dynamic phenomena of these systems. Several studies deal with the dynamics of such pneumatic systems but through streamlined analysis where the influence of pressure-waves propagating in ducts is neglected or poorly described. The related models are even more complex when finite volumes are placed at the ends of connecting lines. In this paper, two different mathematical models describing transient pressure-waves propagating through lines closed by finite volumes are presented. The investigation regards pressure and velocity ranges normally operating in industrial pneumatic systems. Besides the value of new system modeling of different complexity, these models are compared from an analytical and numerical point of view; advantages, disadvantages, weakness, abilities, and inabilities are highlighted and, finally, the relevant analysis is corroborated through experimental validations of wave propagating pressure at fixed positions of ducts. This study results both in the presentation of models of practical interest, as well as in an attempt to provide an elucidation on the need to resort to an accurate model rather than a streamlined one with respect to the geometric and/or operative characteristics of industrial pneumatic systems.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Scheme and nomenclature of the system and related measuring system

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Figure 2

Photograph of the system and related measuring system

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Figure 3

Numerical integration based on characteristics: grid pattern for (a) inner points and (b) at the boundaries in absence of pre-existing flow at initial time t=0

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Figure 4

Numerical integration based on characteristics; grid pattern for (a) subsonic flow from a volume (Q1 or Q2) into the duct and (b) vice versa

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Figure 5

Numerical integration based on characteristics: grid pattern for (a) sonic flow from a volume (Q1 or Q2) into the duct and (b) vice versa

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Figure 6

Numerical integration based on characteristics: grid pattern for supersonic flow from the duct to a volume (Q1 or Q2)

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Figure 7

Simulated pressure and velocity at the receiving volume (x=L) through SBE (---) and NLC (—) model in case of D=6 mm, L=2.53 m, Q1=5 dm3, Q2=1.5 cm3, and po=1.0 bar: (a) pm/po=1.01, (b) pm/po=1.1, (c) pm/po=2.0, (d) pm/po=6.0 and (e) pm/po=6.0, u(L,t) (NLC model)

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Figure 8

Simulated pressure and velocity at the receiving volume (x=L) through SBE (---) and NLC (—) model: reference is Fig. 7 with Q2=26.5 cm3

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Figure 9

Pressure and velocity distributions at different instant of times along the normalized length of the duct (x/L) with pm/po=6.0 and Q2=1.5 cm3

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Figure 10

Simulated pressure at the receiving volume (x=L) through SBE (---) and NLC (—) model: reference is Fig. 7 with D=3 mm and pm/po=1.1; (a) Q2=1.5 cm3 and (b) Q2=26.5 cm3

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Figure 11

Experimental measurement (––) and simulated pressure at the receiving volume (x=L) through SBE (---) and NLC (—) model: reference is Fig. 7 with pm/po=6.0; (a) and (b) Q2=1.5 cm3 and (c) Q2=26.5 cm3

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Figure 12

Experimental measurement (––) and simulated pressure at the receiving volume (x=L) through SBE (---) and NLC (—) model (a) and simulated velocity with NLC (—) model (b) D=6 mm, L=2.53 m, Q1=5 dm3, Q2=16.5 cm3 and pm/po=6.0.

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