07.05.2018Dr. Baum, Managing Director, presented at the 11th IFK in Aachen.
Dr. Baum, Managing Director, presents measures to improve an disordered flow to the reservoir. FLUIDON presents solution models for fluid power applications at the 11th IFK in Aachen. To reduce cycle times, hydraulic drives become consciously more dynamic, what consequently leads to higher fluid exchange rates. On the part of the pressure supply no effort is too big for the design engineers. The return pipe to the tank is, however, often still calculated with rough formulas. This can lead to damages to the plant by cavitation, water hammers and diesel effects and is no longer up-to-date. On investigating water hammer events in tank-pipes it becomes obvious that an examination with simple rough calculations is not leading to the desired results. Too many factors must be considered at the calculation of water hammer. Fortunately, nowadays the numeric simulation can calculate the pressure gradient and the pressure am-plitude of a water hammer in very good approximation. Thus, by means of simulation a basic understanding of the problem in the tank pipe can be achieved. In this contribution the boundary conditions which lead to the emergence of a water hammer after cavitation are introduced. Calculation examples explain the differences of water hammers in drives with HLP fluid and with HFC fluid. By the combination of the simulation results to nomograms, a practice-fit tool is introduced, which can be used to assess the water hammer vulnerability of a drive already during the project planning. The presentation of possible constructive remedial measures completes this contribution. IFK is the world's largest scientific fluid power conference and offers users, manufacturers and scientists an international forum for the exchange of experience in the field of hydraulic and pneumatic drive and control systems. Further information can be found at www.ifk2018.com
01.05.2018E. Pasquini presented his current findings on pressure loss in unsteady annular channel flow at the 11th IFK in Aachen.
E. Pasquini presented a methodology for calculating the pressure loss in unsteady flows through concentric annular channels. The momentum equation in axial direction is solved in the Laplace domain to obtain the unsteady radial velocity distribution. Based on the velocity profile, the relation between the Laplace transforms of pressure loss and area-averaged flow velocity is derived. A time domain representation of this equation is provided for oscillating flows. For arbitrary temporal distributions of the flow, the inverse Laplace transform of the relation between pressure loss and flow velocity has to be derived. Since finding the inverse Laplace transform of the exact weighting function for each possible radius ratio is cumbersome, the annular channel flow is approximated by a plane channel. An error analysis shows that this approximation introduces errors less than 1 % for channel geometries down to radius ratios of 0.45. The approximated weighting function is transformed into the time domain by using the residue theorem from complex analysis. The resulting convolution integral can be used in one-dimensional hydraulic system simulation software. IFK is the world's largest scientific fluid power conference and offers users, manufacturers and scientists an international forum for the exchange of experience in the field of hydraulic and pneumatic drive and control systems.