Modeling of Cavitation-Induced Air Release Phenomena in Micro-Orifice Flows

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Hans-Arndt Freudigmann ◽  
Aaron Dörr ◽  
Uwe Iben ◽  
Peter F. Pelz
Keyword(s):  
Mass Transfer ◽  
Hydraulic System ◽  
System Simulation ◽  
Air Bubbles ◽  
Hydraulic Systems ◽  
Modeling Approach ◽  
Diffusive Mass Transfer ◽  
Orifice Flow ◽  
Flow Through ◽  
Dissolved Air

Impurities like air bubbles in hydraulic liquids can significantly affect the performance and reliability of hydraulic systems. The aim of this study was to develop a model suited for hydraulic system simulation to determine the rate of degassing of dissolved air in a micro-orifice flow at cavitating conditions. An existing model for the flow through a micro-orifice was extended to account for the generation of vapor which is suggested to play the key-role for the degassing mechanism. In comparison with measurements, the results of the modeling approach imply that diffusive mass transfer of dissolved air into generated vapor cavities is the dominating mechanism for the observed air release phenomena.

Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

2009 ◽  
Author(s):  
Michael B. Rannow ◽  
Perry Y. Li
Keyword(s):  
Hydraulic System ◽  
Check Valve ◽  
Fluid Flows ◽  
Soft Switching ◽  
Total System ◽  
System Efficiency ◽  
Hydraulic Systems ◽  
Controlled Systems ◽  
Flow Through ◽  
Hydraulic Valve

A method for significantly reducing the losses associated with an on/off controlled hydraulic system is proposed. There has been a growing interest in the use of on/off valves to control hydraulic systems as a means of improving system efficiency. While on/off valves are efficient when they are fully open or fully closed, a significant amount of energy can be lost in throttling as the valve transitions between the two states. A soft switching approach is proposed as a method of eliminating the majority of these transition losses. The operating principle of soft switching is that fluid can temporarily flow through a check valve or into a small chamber while valve orifices are partially closed. The fluid can then flow out of the chamber once the valve has fully transitioned. Thus, fluid flows through the valve only when it is in its most efficient fully open state. A model of the system is derived and simulated, with results indicating that the soft switching approach can reduce transition and compressibility losses by 79%, and total system losses by 66%. Design equations are also derived. The soft switching approach has the potential to improve the efficiency of on/off controlled systems and is particularly important as switching frequencies are increased. The soft switching approach will also facilitate the use of slower on/off valves for effective on/off control; in simulation, a valve with soft switching matched the efficiency an on/off valve that was 5 times faster.

Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Michael B. Rannow ◽  
Perry Y. Li
Keyword(s):  
Hydraulic System ◽  
Check Valve ◽  
Fluid Flows ◽  
Soft Switching ◽  
Total System ◽  
System Efficiency ◽  
Hydraulic Systems ◽  
Controlled Systems ◽  
Flow Through ◽  
Hydraulic Valve

A method for significantly reducing the losses associated with an on/off controlled hydraulic system is proposed. There has been a growing interest in the use of on/off valves to control hydraulic systems as a means of improving system efficiency. While on/off valves are efficient when they are fully open or fully closed, a significant amount of energy can be lost in throttling as the valve transitions between the two states when the switching times are not negligible. A soft switching approach is proposed as a method of eliminating the majority of these transition losses. The operating principle of soft switching is that fluid can temporarily flow through a check valve or into a small chamber while valve orifices are partially closed. The fluid can then flow out of the chamber once the valve has fully transitioned. Thus, fluid flows through the valve only when it is in its most efficient fully open state. A model of the system is derived and simulated, with results indicating that the soft switching approach can reduce transition and compressibility losses by 81% and total system losses by 64%. The soft switching approach has the potential to improve the efficiency of on/off controlled systems and is particularly beneficial as switching frequencies are increased. The soft switching approach will also facilitate the use of slower on/off valves for effective on/off control; in simulation, a valve with soft switching matched the efficiency of an on/off valve that was 4.4 times faster.

Paper 10: Unsteady Incompressible Flow through Hydraulic Systems

1966 ◽  
Vol 181 (1) ◽  
pp. 134-143
Author(s):  
B. W. Roberts
Keyword(s):  
Incompressible Fluid ◽  
Hydraulic System ◽  
Wave Speed ◽  
Characteristic Length ◽  
Dynamic Pressure ◽  
Bernoulli Equation ◽  
Hydraulic Systems ◽  
Worked Example ◽  
Hydraulic Machines ◽  
Flow Through

The unsteady Bernoulli equation applied to an incompressible fluid may be used to calculate the unsteady pressures and velocities in a hydraulic system involving pipework and hydraulic machines. The effects of changes in the dynamic pressure, fluid friction, and the quasi-steady pump or turbine characteristics can be included. The results are applicable to situations in which the time describing the system disturbances is very much slower than the characteristic length of the system divided by the wave speed. In other words, the approach is similar to a rigid water-column theory used in water-hammer analysis. A worked example is also included.

Bubble Elimination from Working Oil for Environmentally Friendly Hydraulic System Design

2012 ◽  
Vol 6 (4) ◽  
pp. 488-493 ◽  
Author(s):  
Yutaka Tanaka ◽  
◽  
Sayako Sakama ◽  
Ryushi Suzuki ◽  
Keyword(s):  
Cost Reduction ◽  
Hydraulic System ◽  
High Performance ◽  
Swirl Flow ◽  
Hydraulic Fluid ◽  
Air Bubbles ◽  
Hydraulic Systems ◽  
Hydraulic Fluids ◽  
Technical Issues ◽  
Hydraulic System Design

With a view to environmental compatibility, energy saving, cost reduction, and high performance and efficiency, one trend in hydraulic systems, particularly in mobile markets, is to design them to be more compact, require less hydraulic fluid in the reservoir, and use their working hydraulic fluid longer. Air bubbles entrained in working hydraulic fluids have greatly detrimental effects on the function and lifetime of hydraulic fluids, components, and systems. A bubble eliminator using a swirl flow that can eliminate air bubbles from working hydraulic fluid has been proposed and developed by our smart and clean hydraulic project. This paper focuses on technical issues related to air bubbles, the aging process of hydraulic oil, and a field test of the performance of the bubble eliminator.

Diffusive mass transfer in island films

1978 ◽  
Vol 125 (7) ◽  
pp. 489-525 ◽  
Author(s):  
Ya.E. Geguzin ◽  
Yu.S. Kaganovskii
Keyword(s):  
Mass Transfer ◽  
Diffusive Mass Transfer ◽  
Island Films

Mass transfer flame resistant working fluids for hydraulic systems

2007 ◽  
Vol 80 (11) ◽  
pp. 2008-2013
Author(s):  
V. I. Kel’bas ◽  
A. F. Kazankina ◽  
Yu. I. Kartashev ◽  
V. V. Fomenko
Keyword(s):  
Mass Transfer ◽  
Hydraulic Systems ◽  
Working Fluids

Dynamic balance analysis of contamination control for hydraulic systems based on dynamic filtration ratio

2016 ◽  
Vol 68 (1) ◽  
pp. 45-51
Author(s):  
Guangying Ma ◽  
Shurong Ning ◽  
Yunlong Hu ◽  
jun Gao
Keyword(s):  
Hydraulic System ◽  
Dynamic Balance ◽  
Contamination Level ◽  
Hydraulic Systems ◽  
Level Control ◽  
Content Type ◽  
Contamination Control ◽  
Precise Control ◽  
Dynamic Filtration ◽  
The Relationship

Purpose – The aim of this study is to establish a dynamic model of the filtration ratio. For the problem that the measured value of the filtration ratio is far less than the theoretical value in the actual hydraulic filtering system, the paper aims to find the relationship between the filtration ratio and the parameters of the hydraulic systems, such as the contamination level and the dirt-holding quantity of the filter. Design/methodology/approach – The paper opted for the method of experimental analysis and simulation to determine the relationship between the filtration ratio and the parameters of the hydraulic system, and established a dynamic filtration ratio model. Findings – The paper provides a preliminary model of dynamic filtration ratio, and the model shows that the filtration ratio is exponentially related to the contamination level and the dirt-holding quantity. Different filters have different influence coefficients. The filtering capacity for a certain particle size and the contamination level control of the filter for different hydraulic systems can be judged according to the dynamic balance equation of hydraulic systems. Originality/value – The paper is useful in the selection of filters and in the precise control of the contamination level of the hydraulic system.

Sign in / Sign up

Export Citation Format

Share Document