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Flow Pulsations in Fluid Power Machines - a Measurement and Simulation Study
Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
2008 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Stricter requirements for better working environment involve noise and vibration control of hydraulic machines. The operational conditions for hydraulic machines, such as pressure and rotational speed, are also increasing and this makes it even more difficult to develop a quiet, vibration-free machine due to the interdependence between noise and escalating operational conditions. The thesis investigates machines working in different driving modes and under different operational conditions.

A so-called cross-angle is proposed for motor as well as pump/motor applications with variable displacement angles. The cross-angle is intended to reduce the overall noise level in the machine's working area. Other noise reduction features are also considered for machines working in different modes.

To facilitate the system integrator's ability to design quiet systems, methods to determine the source flow and source impedance of the machine are essential. The source flow is assumed to be created at the valve plate and the internal impedance related to the high pressure port are completely independent of the rest of the system. Knowledge of these properties makes it possible to foresee the noise properties of a system already on the design phase. A novel source flow measurement method, the source admittance method, is investigated here. The method is considered to be robust and easy to use to suit industry requirements.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2008. , 74 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1355
Keyword [en]
noise, pump, motor, measurement, optimisation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-42325Local ID: 62599ISBN: 978-91-7393-938-6 (print)OAI: oai:DiVA.org:liu-42325DiVA: diva2:263181
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-08
List of papers
1. The source admittance method A new measurement method for hydrostatic pump flow pulsation
Open this publication in new window or tab >>The source admittance method A new measurement method for hydrostatic pump flow pulsation
2006 (English)In: Proc. of the 4th FPNI - PhD Symposium Sarasota, Vol 1, Sarasota: Coastal Printing , 2006, 297-309 p.Conference paper, Oral presentation only (Refereed)
Abstract [en]

Two main drawbacks with hydraulic systems are noise and vibrations, mainly created from flow pulsations in positive displacement pumps. The flow ripple can be divided in two parts; kinematic and compressible. Kinematic flow ripple is created due to the limited number of pumping elements. Compressible flow ripple is created due to cornpressibility effects in the pumping chambers and is the dominating effect at high pressures. There are well proven methods to decrease noise in specific operation conditions, but there is an urgent need for new techniques in machines working under varying operation conditions. There is also a need for improved measurement methods to be used in product development and to judge new inventions to decrease noise.

Simulation techniques are useful in the early stages of the development process. There are useful and accurate simulation models capable of predicting source flow ripple in hydrostatic pumps and thereby useful for optimisation purposes. Simulation results are, however, of less practical use before they are experimentally verified . The experimental methods must be simple and straightforward if they are to be accepted in industry.

This paper describes a new method to measure source flow. It is called the source admittance method. Compared to earlier methods such as the two-microphone method, the main benefit is that there is no need for a model of the outlet channel - the source flow is measured through an additional pressure transducer inside the pump. The method works very well with a tested fixed bent-axis pump with a rather simple outlet channel. Experiments have also been performed with a variable in-line pump with added complexity to the out let channel. Although the overall impression is positive, these experiments show that the method needs to be further to be used for such machines. In both cases, the new method is compared with earlier verified simulation models and with measurements based on the two-microphone method. Apart from the mentioned discrepancies in a narrow frequency range, agreement is very good.

Place, publisher, year, edition, pages
Sarasota: Coastal Printing, 2006
Keyword
Flow pulsations, measurement, hydrostatic pump, two-microphone method
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-36611 (URN)31745 (Local ID)1-4243-0499-7 (ISBN)31745 (Archive number)31745 (OAI)
Conference
4th FPNI - PhD Symposium Sarasota. Sarasota, Fl, US, June 2006.
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-08
2. The source admittance method for pumps with complex outlet channels
Open this publication in new window or tab >>The source admittance method for pumps with complex outlet channels
2007 (English)In: Proc. of the 10th Scandinavian International Conference on Fluid Power (SICFP'07), vol 1, Tampere: Tampere University of Technologi , 2007, 279-293 p.Conference paper, Published paper (Refereed)
Abstract [en]

The source admittance method offers a new way to measure flow ripple. Compared to earlier methods such as the two-microphone method, the main benefit is that there is no need for a model of the outlet channel - the source flow is measured through an additional pressure transducer inside the pump. This makes the source admittance method easier to use and less modelling skill is needed. Furthermore, the method is more reliable because the somce flow is measured, i.e. pressure at the creation spot, directly. In earlier studies, the method proved to work very well for pumps with simple discharge channels but less well for pumps with complex discharge channels.

The experimental test object is a pump with a simple outlet channel. Its internal impedance can easily be changed in a controlled manner; complexity can thus be added step by step. The paper contributes to the understanding of how complexity of the pump's discharge channel influences the usefulness of the source admittance method.

Place, publisher, year, edition, pages
Tampere: Tampere University of Technologi, 2007
Keyword
Fluid power
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-40967 (URN)54782 (Local ID)978-952-15-1761-7 (ISBN)54782 (Archive number)54782 (OAI)
Conference
10th Scandinavian International Conference on Fluid Power (SICFP'07). Tampere, Finland, May 2007.
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-08
3. Flow pulsation reduction for variable displacement motors using cross-angle
Open this publication in new window or tab >>Flow pulsation reduction for variable displacement motors using cross-angle
2007 (English)In: Power Transmission and Motion Control (PTMC 2007) / [ed] D. N. Johnston, and A. Plummer, Essex: Hadleys Ltd , 2007, 103-116 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper considers using the cross-angle in variable displacement hydraulic machines. The cross-angle is a fixed displacement angle around the axis perpendicular to the normal displacement direction. The cross-angle changes the angles to the pistons top and bottom dead centres as a function of the fraction of displacement in such a way that the valve plate timing is varied and different pre-compression and decompression angles are obtained. A non-gradient optimisation technique, the Complex method, is used together with a comprehensive simulation model in order to find the optimal cross-angle for a variable displacement hydraulic motor. The paper shows that the cross-angle can be used to reduce noise in variable displacement motors. One issue that makes the motor application more difficult is the increased dependence between outlet and inlet flow ripple which is not found in pump applications. Furthermore, the paper discusses how to use the cross-angle for machines which can work both as a motor and a pump.

Place, publisher, year, edition, pages
Essex: Hadleys Ltd, 2007
Keyword
Cross-angle flow pulsations noise hydraulic pump hydraulic motor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-40965 (URN)54778 (Local ID)978-0-86197-140-4 (ISBN)54778 (Archive number)54778 (OAI)
Conference
Power Transmission and Motion Control (PTMC 2007), 12-14 September, Bath, UK
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-08

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