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Design principles for noise reduction in hydraulic piston pumps: simulation, optimisation and experimental verification
Linköping University, Department of Mechanical Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Noise reduction in hydmulic systems has been an important research topic for several decades. In recent years, industry's interest in the area has grown dramatically. The reason is new national and international requirements and legislation governing working conditions. As a consequence of this, considerable reduction of noise from machinery in general has been achieved. The reduction of noise in hydraulic systems, however, has not gained from the same considerable progress, which implies that hydraulic noise has become perceptible through the surrounding machinery noise. Not only has noise reduction of hydraulic systems become increasingly important, it has also become more difficult because of the ever-increasing working pressure level, which is highly correlated to noise and vibration.

Noise in hydraulic systems is created mainly by the hydrostatic pump and motor, working with large pressure differences in the suction and delivery ports. Being exclusively of displacement type, the hydrostatic machine creates substantial flow pulsations in both the discharge and suction ports. The flow pulsations give rise to system pressure pulsations, which in turn transform into vibration and audible noise. Excessive pulsating piston forces and bending moments due to the large pressure difference between the machine's discharge and suction ports also contribute to noise and vibration.

To obtain satisfactory noise reduction, there is a need for effective and reliable design tools and design methods. This thesis concerns simulation, optimisation and experimental verification of axial piston pump design for noise reduction. Much of the work relates to the different origins of noise and how to formulate objective functions that simultaneously reflects different aspects of noise reduction. New and conventional design features are examined both theoretically and experimentally. One novel and promising design feature thoroughly investigated in this thesis is the so-called crossangle that aims to provide low noise in variable displacement machines. Different measurement approaches are employed for experimental verification. It is shown that conventional methods are often inadequate for measuring source flow in variable displacement units due to the complex outlet channel. A new method, referred to as the Source admittance method, is proposed.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2005. , 164 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 965
Keyword [en]
hydraulic piston pumps
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-31420Local ID: 17198ISBN: 91-85457-15-9 (print)OAI: oai:DiVA.org:liu-31420DiVA: diva2:252243
Public defence
2005-10-14, Nobel, Hus B, Campus Valla, Linköpings Universitet, Linköping, 10:15 (English)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-12-05Bibliographically approved
List of papers
1. Dynamic analysis of shuttle technique performance applied on hydraulic transformer
Open this publication in new window or tab >>Dynamic analysis of shuttle technique performance applied on hydraulic transformer
2002 (English)In: Proc. of the 3rd International Fluid Power Conference (IFK'3): Volume 2, Fluid Power Focused on Applications, 2002, 249-261 p.Conference paper, Published paper (Refereed)
Abstract [en]

As an alternative to traditional valve coutrol, hydraulic transformation has proved to be an attactive approach from an efficiency point of view. According to the Innas1 concept, hydraulic transformation is achicved using a modified displacement machine design. In order to realise the transformation using only one displacement machine, it is necessary to use a valve plate containing three kidney slots for the three supply lines: supply, load and tank. By displacing the valve plate, pressure/flow ratio can be transformed, ideally with preserved efficiency. When using three kidney slots together with a traditional displacement machine with two dead centres, the commutation between two subsequent kidneys will occur while the piston is moving. This will result in pre-compression or decompression of the cylinder fiuid, with severe pressure peaks as a consequence. Besides noise and vibration, these pressure peaks will decrease the total efficiency considerably. Also driving shaft torque variations will appear, which will affect the rotational movement by speed fluctuations. In order to minimise the pressure peaks during valving land passages. small pistons between pairs of cylinders in the barrel are introduced. This is referred to as shuttle technique. Using these shuttles, excess of cylinder fluid during commutation can be transferred to adjacent cylinders, and thus prevent cylinder pressure peaks from appearing.

It is very difficult to measure the internal states of the shuttle in an operating transformer. By using computer simulation techniques, detailed analyses of the internal workings of the shuttle can be performed. In this work, a detailed description of the dynamic behaviour of the shuttle is given. Advantages and disadvantages of the technique are discussed.

1 Innas BV, Netherlands

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-85958 (URN)978-3-82-659900-2 (ISBN)
Conference
3rd International Fluid Power Conference (IFK '3), March 5th and 6th 2002, Aachen, Germany
Available from: 2012-12-05 Created: 2012-12-05 Last updated: 2012-12-05
2. The importance of suction port timing in axial piston pumps
Open this publication in new window or tab >>The importance of suction port timing in axial piston pumps
2005 (English)In: Proc. of the 9th Scandinavian International Conference on Fluid Power, (SICFP '05) / [ed] Palmberg, Jan-Ove, Linköping: Linköping Universitet, Institute of Technology , 2005, 32- p.Conference paper, Published paper (Refereed)
Abstract [en]

Hydraulic pumps give rise to flow ripples in both discharge and suction lines. The flow pulsations transform into pressure ripples which in turn create vibration and audible noise. With a careful design of the valve plate timing, flow ripple can be minimised. Much research is dedicated to the design of discharge port commutation, i.e. the pre-compression dynamics. This work, however, focuses on the suction port timing.

Besides controlling flow ripple in the tank line, suction port timing influences fluid air-release which in turn has substantial impact on the effective system bulk modulus. lncreased air-release implies reduced cylinder filling performance, reduced volumetric efficiency and increased flow pulsations. In addition, the cylinder decompression at suction port commutation directly affects the resulting piston force profile and internal bending moments which largely contributes to pump housing vibration and noise emissions. Thus. the design of the suction port timing is crucial for flow ripples, air-release, pump housing vibrations and direct noise emissions from the pump. Also. the risk for cavitation is controlled.

This paper also investigates the efficiency of an Air Drain Groove, ADC, as an alternative to conventional pressure relief grooves at suction port commutation. Correctly designed, the ADG reduces the cylinder pressure at piston top dead centre by bleeding off a very small amount of cylinder fluid to the housing drain. The air-release hereby obtained is directed into the pump casing instead of into the suction port and should thereby give rise to a higher system bulk modulus. Experiments reveal, however, that the efficiency of the ADC is not preferable to a conventional pressure relief groove, neither regarding air-release, nor noise emissions.

Place, publisher, year, edition, pages
Linköping: Linköping Universitet, Institute of Technology, 2005
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-31417 (URN)17195 (Local ID)9185457965 (ISBN)9789185457960 (ISBN)17195 (Archive number)17195 (OAI)
Conference
The 9th International Conference on Fluid Powers, SICFP'05, July 1-3, Linköping, Sweden
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-12-05
3. Optimal design of the cross-angle for pulsation reduction in variable displacement pumps
Open this publication in new window or tab >>Optimal design of the cross-angle for pulsation reduction in variable displacement pumps
2002 (English)In: Power Transmission and Motion Control: PTMC 2002 / [ed] Burrows, C. R. and Edge, K. A, Wiley-Blackwell, 2002, 319-333 p.Conference paper, Published paper (Refereed)
Abstract [en]

The cross-angle, illustrated in this paper, is a fixed displacement angle around the axis perpendicular to the normal trunnion axis. With the cross-angle, the traditional piston dead centres will change as the normal displacement angle is varied. The result is a behaviour similar to thal of the revolving valve plate technique. but without any movable parts. When the cross-angle is used in a constant pressure system with a variable pump, the desired dead centre for optimal pro-compression coincides with the obtained dead centre for a wide range of displacement angles. This implies that when the cross-angle is used, the flow ripple becomes less sensitive to changes in displacement angles. The cross-angle does not constitute an alternative to the different design features developed, but rather as complement for preserved effective flow ripple reduction over a wide range of displacement angles.

ln this study. simulation-based optimisations, employing non-gradient optimisation techniques such as genetic algorithms and the Complex method, are used in order to find the optimal cross-angle for a variable displacement pump. Furthermore. with the help of optimisation, the trade-offs between attributes such as low flow ripples, avoidance of large cylinder pressure-peaks, and cavitation have been studied. Increased insight is thereby gained into what possibilities the cross-angle offers regarding reduction of pump ripple for a variable displacement pump.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2002
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-36697 (URN)32178 (Local ID)1860583792 (ISBN)978-1860583797 (ISBN)32178 (Archive number)32178 (OAI)
Conference
Bath Workshop on Power Transmission and Motion Control (PTMC 2002), September 2002, Bath, UK
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2012-12-05
4. Influence from the cross-angle on piston forces and bending moments in variable hydraulic piston pumps
Open this publication in new window or tab >>Influence from the cross-angle on piston forces and bending moments in variable hydraulic piston pumps
2003 (English)Report (Other academic)
Abstract [en]

By implementing an additional incline (cross-angle) of the swash plate of an axial piston pump, in the direction perpendicular to the traditional displacement direction, the piston dead-centre points will move as the displacement angle varies. The cross-angle is fixed and normally very small (1-4°). If designed correctly, the movement of the dead-centre points achieved by using a cross-angle coincides with the dead centres desired for optimal cylinder pre-compression and decompression for all displacement angles. It has in earlier works been described how the cross-angle enables minimisation of discharge and inlet peak-to-peak flow ripple for all displacement angles simultaneously. In this paper, it is also investigated how the piston forces and the bending moments are influenced.

The cross-angle is designed using simulation-based multi-objective optimisation. It is investigated how objective functions can be made up from peak-to-peak values as well as from frequency spectrum of signals. The trade-offs between the conflicting objectives considered are elucidated by using the concept of Pareto optimality. The result from such a Pareto optimisation is not one optimal solution, but a set of optimal solutions. With the technique presented, it is thus possible to investigate an optimal value for the cross-angle that the most beneficial impact on all factors that influence the noise level of the pump.

Series
LITH-IKP-R, ISSN 0281-5001 ; 1391
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-85981 (URN)
Available from: 2012-12-05 Created: 2012-12-05 Last updated: 2012-12-05
5. Experimental verification of cross-angle for noise reduction in hydraulic piston pumps
Open this publication in new window or tab >>Experimental verification of cross-angle for noise reduction in hydraulic piston pumps
2007 (English)In: Proceedings of the Institution of mechanical engineers. Part I, journal of systems and control engineering, ISSN 0959-6518, E-ISSN 2041-3041, Vol. 221, no 3, 321-330 p.Article in journal (Refereed) Published
Abstract [en]

One of the most important drawbacks with hydraulic systems is noise and vibration, which mainly originate from the hydrostatic pump. A great number of noise-reducing design features have been developed, but they are all, to a greater or lesser extent, sensitive to variations in operational conditions. The present paper is concerned with optimal design and experimental verification of the cross-angle in an axial piston pump. The cross-angle is a small fixed incline of the swash plate in the direction that is perpendicular to the traditional displacement direction. It enables effective noise reduction throughout the whole range of displacement angles.

Simulation-based optimization is used to design a pump with optimal cross-angle and a matching valve plate. The design is manufactured and experimentally evaluated. Source flow measurements using the two-microphone method show good agreement between simulation and experiments, which verifies the applicability of the simulation model used. The benefits from using the cross-angle are then verified by comparing it with a pump with a traditional swash plate design, i.e. without the cross-angle. Both source flow measurements and sound level measurements in an anechoic chamber show good improvements from using the cross-angle.

Keyword
Cross-angle, Noise, Optimization, Simulation, Source flow
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-49333 (URN)10.1243/09596518JSCE208 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12

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