The Modelon Hydraulics Library introduces improved handling of thermodynamic effects by including a new concept of flexible thermohydraulic ports.
During the design of a hydraulic system, many questions must be answered, such as: Are the product performance goals met? Can the thermal constraints be satisfied? Are the system dynamics under control and do we avoid oscillations? Product configurations must be analyzed with respect to various aspects.
The product configuration under analysis remains the same, and the engineer typically wants to make minimal changes to its physical model. For instance, models with or without thermal effects should be modeled and parameterized consistently. Thermal or thermodynamic effects, used in various hydraulics applications such as hydraulic vehicle brake and fuel injection systems, enable users to analyze how big of an impact temperature has on the hydraulic system, since oil properties are temperature-dependent. Technically, the specific enthalpy is included in the hydraulic ports and a dynamic energy balance in the hydraulic volumes. Still, in one context it is favorable to include such effects, and in another one would rather benefit from higher computational performance. Such fluid power system modeling can often present challenges, as users are often forced to maintain separate models with and without thermodynamic effects. Until recently, this was the only viable solution for handling thermodynamic effects in their modeling.
Considering this need and benefit to the end user, the Modelon Hydraulic Library includes a menu item that allows users to enable and disable thermal effects. This feature enables users to have non-thermal and thermal hydraulics in the same framework. (Figure 1)
This added benefit allows users to integrate thermodynamic effects and analyze how big of an impact temperature has on the hydraulic system, since oil properties are temperature-dependent.
With its latest release, all of this has been made even more user friendly. The Modelon Hydraulics Library is now introducing a new concept called the “flexible thermohydraulic port” to handle the dynamic energy balance in an even easier way. Here are the key benefits of this:
Creating models with highest possible simulation performance has never been more convenient as all of this happens automatically in the background when you make a connection between components.
The following graphs shows result from a thermohydraulic system with and without thermal effect.
Figure 3: The blue graph shows the system pressure variation with "useThermal" flag enabled. The red graph shows the system pressure variation with "useThermal" flag disabled.
Figure 4: The blue graph shows the actual temperature variation in the system with "useThermal" flag enabled. The red graph shows the temperature variation in the system with "useThermal" flag disabled.
Here it is clear that including thermal effects has improved prediction of other important system variables such as pressure. Also using the latest Hydraulics Library 4.7, one can easily study the thermodynamic effect on the system by simply enabling/disabling a flag along with considerable gain in simulation speed.
Creating flexible models with highest possible simulation performance has never been more convenient
For more details on therodynamic effects in Modelon’s Hydraulic library, please refer to Hydraulics Library 4.1 adds new thermodynamic effects blog.
Jim Claesson has an MSc in Mechanical Engineering from Lund University. Jim is a modeling and simulation consultant at Modelon, engaged with both thermofluid and mechanical systems. He is also the project manager for the development and support of two Modelica Libraries: Hydraulics and Pneumatics. In his free time Jim competes in road racing with motorcycles among the top riders in Sweden.
Nithish Selvan has been working in model based engineering since 2016. With Modelon, he works on modeling and simulation consulting and product development with a focus on aerospace (Jet Propulsion) and fluid systems (Hydraulics).