Pressure Losses in Hydraulic Manifolds

Hydraulic manifolds are used to realize compact circuit layouts, but may introduce a high pressure drop in the system. In fact, their design is optimized more for achieving minimum size and weight than for reducing pressure losses.

This work studies the pressure losses in hydraulic manifolds using different methods: Computational Fluid Dynamic (CFD) analysis, semi-empirical formulation derived from the scientific literature, when available, and experimental characterization.

The purpose is to obtain the pressure losses when the channels’ connections within the manifold are not ascribable to the few classic cases studied in the literature, in particular for 90° bends (elbows) with expansion/contraction and offset intersection of channels.

The comparison of the results obtained allows for drawing some guidelines for the design of the manifold channels and to discuss the reliability of CFD analysis as a tool to improve the design of a hydraulic manifold. We focus first on simple geometries, considering the intersection between the channels of the manifold with one or two 90° elbows. This way, we can compare our results with the ones already published in the literature, validate the analysis, and then apply the same analysis method to test cases not previously discussed.

Results from CFD simulations show that the virtual analysis can depict the correct trend of pressure drop in all the different geometries analysed following, at a “certain distance”, the experimental results. The difference between experimental and CFD results normally increases with the flow rate and the pressure drop. The gap is, however, quite high and always with an overestimation of CFD simulations compared with the experimental results.

Going into the detail of manifold design rules, some considerations can be highlighted regarding the possibility to introduce an elbow with a moderate expansion in the manifold (no great changes with reverse flow, i.e. through a contraction), the use of offset intersections and the ‘shape’ to prefer (and the one to avoid) when two consecutive elbows are necessary in the manifold passage, always related to the relative distance between the elbows.

The next step of this research is to analyse what happens with more complex but realistic connections on a manifold block, still comparing the CFD analysis and the experimental results, and deepening the study of aeration/cavitation occurrence.

Our Interview with the magazine Oleodinamica-Pneumatica

You can read the magazine and the full interview online.

The goal is to offer the world of Fluid Power a simple and cost effective tool that simplifies the design process, allowing companies to verify and evaluate the functionality and performance of their systems before the experimental testing phase.

The approach is the lumped parameter one, useful for analysing the dynamic behaviour of systems of any type. The proposed solution is a simulation software that can be easily integrated into the design flow: a digital twin of the component or system is created, always integrated with a customized interface that simplifies its use in order to make it accessible to all company levels.

All of this, thanks to a team that involves professionals who have been working in the fluid power sector for over thirty years, such as Massimo Borghi, professor in the scientific sector of Fluid Machines at the Enzo Ferrari Engineering Department in Modena since 2001, as well as professor of Machines and Energy Systems and Hydraulics in the Mechanical Engineering degrees course at the University of Modena and Reggio Emilia. On these premises, SmartFluidPower Srl was born in April 2018, as a spin-off of the University of Modena and Reggio Emilia.

Among the watchwords: innovation, adaptability and energy saving. We talked about it with Giovanni Cillo, president and legal representative of SmartFluidPower srl.

Modeling of Hydrostatic Bearings for Servo-Cylinders

Hydraulic servo cylinders are widely used in versatile industrial applications such as machine tools, test rigs for any kind of components, industrial robots, autonomous manufacturing systems and special applications in laboratories. In general, they are typically used whenever a smooth movement with low friction, fast dynamic response and possible radial forces are required.

Hydrostatic journal bearings with pockets are used on servo cylinders’ rod ends in order to guarantee the bearing of high loads, reduce friction, remove wear and allow smooth and controllable displacement of the actuator.

The design and manufacturing of these elements is challenging since the good operation relies on the very small tolerances required to bear the load on the cylinder and to reduce leakages.

Lubricated interfaces in fluid power components are one of the most critical issues to be carefully designed for assessing a smooth behaviour and good efficiencies in a system. Moreover, they are fundamental to analyse the complex phenomena determining the positive displacement pumps and motors efficiency and also fault behaviour.

In this work, a 2D fluid dynamic model of hydrostatic journal bearing is presented. The model is composed by a system of equations, created by SmartFluidPower, written in Modelica language and entirely solved in OpenModelica environment. This work concerns the first part of a research activity in which a virtual model and test tool for hydrostatic journal bearing with pockets are created.

The model proposed has the aim to explore the extreme and critical operating conditions of the servo-cylinder and to help and/or improve the design phase: the results show a significant influence of eccentricity and manufacturing tolerances and, therefore, an accurate choice of the design parameters must be followed to look for the best configuration.

With the help of an industrial partner the numerical model is tested and validated: at the end, a virtual design tool is created for industrial designers to help and guide their work.

Besides the specific results obtained regarding the design of the bearings, the work also demonstrates a different use of OpenModelica environment: a pure equations solver of which results are used to create an industrial virtual tool that helps the designer to simulate different configurations and look for the optimal solution.

GoBeyond 2021

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SmartFluidPower was a candidate for the prize GoBeyond 2021, a call for ideas for organizations who focus on a more sustainable future or the digital transformation of the country.

GoBeyond is a competition organized by the Sisal Group, with the aim of encouraging the development of new Italian business ideas, facilitating the transformation of a vision (an idea with a high innovative potential) into a value project (a company) through an approach  of innovative execution based on the experience  of a successful network of organizations.

The contest involves the selection of two categories:

  • “For a more sustainable future”: projects that solve problems of society, territory and people, generating a positive impact for the benefit of the community.
  • “For a technological and digital country”: projects that focus on technological innovation, in order to simplify the lives of people and society 

We participated with the goal of competing with other innovative companies on a national level , and comparing our solutions within the fluid power industry with a set of diverse solutions belonging to other sectors. Among the more than 240 startups that have applied in this 2021 edition, we are part of the short list of the best 20 entrepreneurial projects.

Through our application we have presented a marketing plan to best describe our simulation and consulting activities in the context of the fluid power sector. In addition to the description of the software products and dedicated services offered by SmartFluidPower, we have analysed the market we target and its recent trends towards dynamism and evolution, thanks to the strong appeal of energy saving: then we detailed how we intend to be part of this transformation, with marketing strategies and communication channels.

In the marketing plan we have also presented a S.W.O.T (Strengths Weaknesses Opportunities Threats) analysis to show strengths and weaknesses, the threats to the diffusion of our products on the market and the social impact of our approach: regarding the latter, the reconstruction of models virtualization of internal components and systems promotes the development and maintenance of companies know-how, with the direct consequence of an effective transfer of knowledge by expert technicians to new designers.

The document also exhibited a monitoring of the results of these first 4 years of activity which highlighted the correct forecast of the demand made at the time of establishment in 2018 (except for the year 2020) and a forecast of the target revenues, costs expectations and operating margin for the next 3 years.

The application ended with the planning of our future products, which concerns both the implementation of new features for the existing software tools and the creation of new tools, as well as additional services to be included in the current offer. Finally, the expected future investments on all fronts were presented, from the online marketing platform, to expanding the team to increase the volume and differentiation of the projects developed.

OpenModelica Workshop 2021

OpenModelica Workshop is an annual one-day conference at the University of Linköping, Sweden. On this occasion, OpenModelica users and developers present the latest research projects and industrial applications, using the software in the most advanced and performing way The conference is supported not only by the host university, but also by the OSMC consortium (Open Source Modelica Consortium): a non-profit, non-governmental organization with the aim of developing and promoting the development and usage of the open source OpenModelica Environment, in the following referred to as OpenModelica.

This workshop precedes another 2-day annual workshop also held at the University of Linköping, since 2006, which concerns the Modelica language more broadly and is promoted by MODPROD (Center for Model-Based Cyber-Physical Product Development): an interdisciplinary research center at this University that involves a number of companies as well as researchers from the Department of Computer and Information Science (IDA) and the Department of Management and Engineering (IEI).

The mission of this center is perfectly aligned with SmartFluidPower’s mission: conduct front-line applied research in model-based product development addressing problems such as higher demands on flexibility and quality, and shorter time-to-market from product design to production. This requires increased usage of software/hardware system modeling, management of technology for virtual prototyping, and simulation based strategic planning.

Together with companies and research centers, mostly European, but with some intervention from other continents, we participated with SmartFluidPower both as members of the OSMC consortium, but most importantly as advanced users of the OpenModelica software applied to the industrial sector. In particular, we presented a project entitled ‘Modeling and simulation of volumetric machines with OpenModelica’.

The first objective of the presentation was to introduce the various users and experts of OpenModelica to our library focused on the world of fluid power and connected to the other physical domains, thanks to the other available libraries (mechanics, signals, etc.).

The second goal was to contextualize the library by showing a specific hydraulic application that concerns a low pressure vane pump. With this example, we explained the results of the OpenModelica study on this component, and the critical issues that emerged in the analysis of its results.

In this work, the modeling of the component was simplified through the direct use of equations for the calculation of some variables: we highlighted how the lumped parameter approach, combined with the great flexibility of OpenModelica, makes a very effective interface between a structured library and equations written directly in Modelica language.

During the conference, all the papers were focused on the development of advanced software features and, as in our case, on its use in practical industrial applications in the most varied sectors. There were many enquiries regarding our application while, on our part, the meeting was fundamental to knowing how the potential of OpenModelica is exploited to the maximum in the most varied fields and by experts worldwide.

SmartFluidPower @Cambiamenti 2021

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‘A company is founded on the courage and ability of people, and must be rewarded’

This is the slogan of ‘Cambiamenti 2021 – Award for innovative thinking of new Italian companies’, in which we participated with SmartFluidPower. The competition aims to discover, reward and support the best Italian companies born in the last 4 years (after 1 January 2017) that have been able to rediscover traditions, promote their territory and the community, innovate products and processes and build the future. Changes 2021 aims to recognize merit and offer opportunities for comparison and visibility to those companies that with their activities represent the best of Italy every day and make the country competitive.

We have applied for SmartFluidPower with the aim of expanding our network of contacts and knowing the other innovative companies born in recent years in the area. Among the 1026 nominations of start-ups at a national level and about 150 in the province of Modena, we arrived in the top 10 of the provincial selection and we had the opportunity to exhibit our project in front of a jury and other participants.

Through our elevator pitch we focused on the widespread problems in the design of fluid power systems and components within SMEs and on the solution we propose, based on virtual prototyping to be combined with the classic daily design. With the integration of this methodology, it is possible not only to radically increase the efficiency of the prototyping and re-design processes, but also to increase awareness of all the details of the phenomena that occur in the designed systems (and which are often not accessible for experimental measurement). 

The event showed the innovative projects of companies belonging to the most varied fields, with the most diffused topic of energy efficiency and biomedical applications. Our project provides an efficient and innovative solution aimed mainly at SMEs working in the world of fluid power: given the large number of this type of companies in our region, the project is well integrated into the panorama of companies present, the characteristics of the jury and the event in general. 

The award was promoted by CNA (National Confederation of Crafts and Small and Medium Companies) which guarantees services, advice and information to small businesses in all Italian provinces. At the end of the event, exponents from CNA Modena contacted and involved us within the ‘Hub 4.0’ project which is part of a regional plan where all the Confederations of Emilia-Romagna are present. The project aims to relaunch innovation in participating companies through the dissemination of technologies that lead to more flexible and faster processes with an increase in productivity and quality: our goal in particular will be to exploit the multiple opportunities offered by the incentives provided in this direction and use the network of contacts created to encourage the growth of SmartFluidPower on the regional and national market.

SmartFluidPower @Simulation Summit 2021

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Simulation Summit 2021 is the first Italian conference on CAE simulation in the industrial field, born with the aim of promoting engineering simulation and its conscious and effective use: the goal is to share experiences of practical use in a transparent and independent way through contents and presentations of a pragmatic-applicative nature. 

We participated with the presentation ‘Lumped-parameter modelling and simulation in fluid power applications’which highlighted the typical problems of systems and components design and the solution proposed by us, through some examples on practical cases.

The main purpose was to illustrate how this type of modelling, which is applied to study the dynamic behaviour of engineering systems of any nature, is particularly suitable for the analysis of fluid power components and systems.

The event was part of one of the approximately 50 conferences organized during the MECSPE 2021 exhibition in Bologna, an important occasion in Italy dedicated to innovations for the manufacturing industry, which includes more than 2,000 exhibiting companies and 48,000 visitors in each edition.

We noticed the strong prevalence of interventions regarding examples and evolutions of distributed parameter simulation methods (FEM, CFD, etc.): this allowed us to introduce our modelling technique in a more marked way and to highlight differences and benefit according to the specific problem faced.

The meeting proved to be an important opportunity to know the avant-garde in the field of simulation applied to engineering and to present our solutions to an audience made up of different actors involved in the product development and innovation process (users of simulation tools , designers, analysts, entrepreneurs, students, etc.).

Our final goal was to underline the important role of lumped-parameter simulation, enhanced by the products we have developed for the fluid power world, within a panorama of engineering simulations that is now indispensable to overcome daily challenges effectively and in less time.

During the conference we both created contacts with spectators interested in our simulation solution and found interesting ideas from the works proposed by the other speakers: in the future we will actively participate in this type of events with the fundamental purpose of spreading the use of our modelling methodology in everyday practical activities and, at the same time, to promote its integration with other types of simulation applied to specific cases.

Model of vane pumps developed in OpenModelica

research paper

In this paper, a 0D fluid dynamic model of a vane pump used to refill tanks with fuel is presented. The model is entirely developed in OpenModelica environment, where SmartFluidPower have created specific libraries of elements suitable for the physical modelling of fluid power components and systems.

Among the different approaches, the zero-dimension (0D) fluid-dynamic modelling of positive displacement machines is suitable to study many aspects as the fluid borne noise related to the flow rate and pressure irregularity and the dynamic behaviour of the variable displacement control. Well before the realization of a physical prototype, the model is useful to give indications on the impact of the design on the pressure transients inside the volume chambers and pressure and flow ripples.

The model of the vane pump is described together with the main design features that can be analysed in terms of their influence on the pump behaviour. The model has been created in a “parametric fashion”: this means that it can easily be adapted to analyse different design modifications, for example the number of vanes, the suction and delivery flow areas, the stator internal profile.

Overall, this approach in modelling allows to link the geometrical features of the machine with its dynamic behaviour and for this reason is particularly useful in guiding the design.

Besides the specific results obtained regarding the design of the pump, the paper also demonstrates the use of OpenModelica language and environment, and its efficacy, into the applications of fluid power modelling and simulation.