The dynamic performance of a hydraulic system is dependent on the fluid bulk modulus, which can be affected by several factors including air release and pipe compliance. A technique is described for the in situ measurement of the speed of sound from which the bulk modulus may be evaluated. It entails analysis of pressure ripple recorded at three locations in the hydraulic line. Measured values of the bulk modulus in high-pressure pipes were found to be close to the isentropic tangent bulk modulus predicted from the fluid manufacturer's data.
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References
1.
HaywardA. T. J.How to estimate the bulk modulus of hydraulic fluids. Hydraulic Pneumatic Power, 1970, 16 (181), 28–40.
2.
AkersA.LinS. J.A comparison of the performance of single spool and two-spool two-stage flow control valves. Ninth International Symposium on Fluid power, Cambridge, April 1990 (Scientific and Technical Information).
3.
WrightJ.BurtonR.SchoenauG.Lumped parameter model of a variable displacement pump. J. Fluid Control, 1988, 19(2), 37–57.
4.
HoriN.PannalaA. S.UkrainetzP. R.NikiforukP. N.Design of an electrohydraulic positioning system using a novel model reference control scheme. Trans. ASME, J. Dyn. Syst., Measmt Control, 1989, 111, 292–298.
5.
SuzukiK.A hydraulic pressure intensifer using oil hammer and its application to a hydraulic cylinder. J. Fluid Control, 1988, 19(1), 59–73.
6.
EtsuoM.KatoS.HashimotoM.Unstable vibration occurring in a hydraulic servomechanism controlled by a throttle valve. Part II: Measurement of dynamic axial force and theoretical consideration. J. Fluid Control, 1989, 19(4), 47–67.
7.
MutoT.YamadeH.Digital simulation of PWM-hydraulic actuator system. Proceedings 2nd International Conference on Fluid power transmission and control, Hangzhou, China, 1989 (International Academic Publishing, Beijing).
8.
EdgeK. A.TilleyD. G.The use of plane wave theory in the modelling of pressure ripple in hydraulic systems. Trans. Inst. Measnt Control, 1983, 5(4), 171–178.
9.
KlausE. E.O'BrienJ. A.Precise measurement and prediction of bulk modulus values for fluids and lubricants. Trans. ASME, J. Basic Engng, September, 1964, 469–474.
10.
HaywardA. T. J.Measuring the compressibility of liquids. Acta Imeko, 1964, 249–272.
11.
McMillanD. R.LangemannR. I.A precision ultrasonic interferometer for liquids and some velocities in heavy water. J. Acoust. Soc. Am, 1947, 19, 956–960.
12.
SteckiJ. S.DavisD. C.Hydraulic system analysis—prediction and measurement of effective bulk modulus, Basic Fluid Power Res. J. (Oklahoma State University)1981, 14(4), 333–335.
13.
BolleterU.Using transfer function measurements to determine energy propagation in fluid lines, with application to centrifugal pump systems. International Congress on Recent developments in acoustic intensity measurement, France, 1981. (Centre Technique des Industries Mechaniques, Sentis, France).
14.
MargolisD. L.BrownF. T.Measurement of the propagation of long-wavelength disturbances through turbulent flow in pipes. Trans ASME, J. Fluids Engng, March, 1976, 70–78.
15.
EdgeK. A.JohnstonD. N.The ‘secondary source’ method for the measurement of pump pressure ripple characteristics. Part 1: Description of method. Proc. Instn Mech. Engrs, Part A, 1990, 204(A1), 33–40.
16.
BS6335, 1990. Methods for determining pressure ripple levels generated in hydraulic fluid power systems and components. Part 1: secondary source method for pumps, 1990 (British Standards Institution, London).
17.
JohnstonD. N.EdgeK. A.The impedence characteristics of fluid power components—restrictor and flow control valves. Proc. Instn Mech. Engrs, Part I, 1991, 205(I1), 3–10.
18.
EdgeK. A.JohnstonD. N.The impedance characteristics of fluid power components—relief values and accumulators. Proc. Instn Mech. Engrs, Part I, 1991, 205(I1), 11–22.
19.
DraperN.SmithH.Applied regression analysis, 1966 (Wiley, New York).
20.
EdgeK. A.JohnstonD. N.The ‘secondary source’ method for the measurement of pump pressure ripple characteristics Part 2: Experimental results. Proc. Instn Mech. Engrs, Part A, 1990, 204(A1), 41–46.
21.
PearsallI. S.The velocity of water hammer waves. Proc. Instn Mech. Engrs, 1965–66, 180, Part 3E, 12–20.
22.
FosterK.ParkerG. A.Transmission of power by sinusoidal wave motion through hydraulic oil in a uniform pipe. Proc. Instn Mech. Engrs, 1964–65, 179, Part 1, (19), 599–614.
23.
LallementJ.Etude du comportement dynamique des lignes hydrauliques. Les Mémoires Techniques du CETIM, September, 1976, 27, 65.
24.
ZielkeW.Frequency dependent friction in transient pipe flow. Trans ASME, J. Basic Engng, 1970, 92, 865–873.
25.
LongmoreD. K.TucB.Reduction of fluid borne noise in hydraulic circuits by means of flexible hoses. Seminar on Quieter oil hydraulics, October 1980 (Institution of Mechanical Engineers, London).
