Dirt ingress in hydraulic cylinders is one of the sources that leads to pollution of hydraulic systems. There are already several test rigs to investigate external contamination mechanisms. However, until now only the behavior of the whole sealing system was analyzed. A new testing method to understand the dirt particle transport between a reciprocating motioned rod and a wiper is presented. The new approach aims to avoid known issues such as limited reproducibility and long duration. The paper describes the test rig design and operating principle. First measurement results are shown.

Axial piston machines of the swashplate type are commonly used in various hydraulic systems and with recent developments in displacement control, it is essential to maximize their efficiency further reducing operation costs as well as improving performance and reliability. This paper reports findings of a research study conducted for the piston-cylinder interface utilizing a novel fluid structure thermal interaction model considering solid body deformation due to thermal and pressure effects in order to accurately predict the transient fluid film within the gap. A large reduction in energy dissipation is possible due to reduced clearances allowable due to the surface shaping of the piston resulting in a reduction in leakage. From this study, it is shown that surface shaping of the piston in combination with a reduced clearance is not only beneficial by improving the efficiency of a machine, but also increases the reliability and the performance of the machine as the load support is enhanced.

Rotational hydraulic actuators, e.g. motors, provide infinite stroke as there is no conceptual limit to how far they can turn. By contrast linear hydraulic actuators like cylinders provide only limited stroke by concept. In the world of electrical drives, linear motors provide infinite stroke also for linear motion. In hydraulics, the presented Hydraulic Infinite Linear Actuator is a novelty. This paper presents the novel Hydraulic Infinite Linear Actuator (HILA). The contribution is an assessment of properties relevant for control like high hydraulic stiffness and is based on analysis, simulation and measurements.

Reliability of a piston rod position measurement system is key when applied to large hydraulic cylinders. This and other requirements lead to the development of the CIMS (Cylinder Integrated Measurement System), a contactless and highly accurate system that uses the Hall effect to detect an encoded piston rod. To eliminate deviations caused by mechanical tolerances, temperature and air gap variations etc., the raw signals are filtered and compensated. Its functionality has been extended by making statistical data available, based on the values measured. These include the number of strokes, cumulative stroke length, stroke length distribution, maximum velocity and acceleration, temperature classification and extreme temperatures. Assessment of these data enables the user to optimize his application. Comparison to historic data can give input to the preventive maintenance plan to reduce (unforeseeable) system downtime and to increase the system reliability. This development resulted into the CIMSmart. It is a significant step towards cylinder intelligence.

<div><p>Water is inflammable, non-toxic, environmentally friendly--- desirable traits, for a hydraulic fluid. However, its extremely low viscosity diminishes the load-bearing and sealing capacity of lubricating interfaces. Case in point: axial piston machines of swash plate design are compact, highly efficient positive displacement machines at the heart of hydraulic systems in forestry, construction, aerospace, and agricultural equipment, as well as industrial applications (presses, etc.); however, the three main lubricating interfaces decisive to the performance of such units in terms of both component life and efficiency are challenged by the use of water as working fluid. Especially during high-pressure operation, this low-viscosity lubricant can cause the these interfaces to fail in carrying the imposed load, resulting in severe wear, or even pump failure. The piston-cylinder interface is particularly challenging to design for water because it stands under obligation to carry the heavy side load that acts on the pistons of these machines, which increases with operating pressure. Furthermore, the architecture of axial piston machines of swash plate design does not allow this interface to be hydrostatically balanced.</p> <p> </p> <p>Through the development of a methodology that separates the fluid pressure fields of the three main lubricating interfaces of axial piston machines into their hydrostatic and hydrodynamic components, the present work enables a direct comparison of these interfaces in terms of how they support load. A case study of a 75 cc unit running on hydraulic oil conducted via this methodology at three different operating conditions (low pressure/low speed, low pressure/high speed, and high pressure/low speed) demonstrates that in the piston-cylinder interface, the force from hydrostatic pressure reaches such high magnitudes over the high-pressure stroke that less than half of it is needed to counter the load. The excess force from hydrostatic pressure then becomes the load. Consequentially, hydrodynamic pressure must counter a force from hydrostatic pressure that exceeds the original load. In the other two interfaces, by contrast, over half the load is being carried by hydrostatic pressure, thus significantly diminishing the amount of hydrodynamic pressure the interfaces are required to generate in order to achieve full load support. Moreover, nearly all of the moment on the piston is countered by hydrodynamic pressure, while less than half of the moment on the block is countered by hydrodynamic pressure, and the moment on the slipper is negligible by comparison.</p> <p> </p> <p>While this case study only investigates one pump, it shows how critical hydrodynamic pressure can be to load support in the piston-cylinder interface. The use of a low-viscosity fluid, e.g. water, reduces the hydrodynamic pressure that is generated in this interface, which, at challenging operating conditions, can lead to metal-to-metal contact. However, the performance of the interface can be improved via micro surface shaping, i.e. by giving the surface of the piston, or the bore that it moves through, a shape on the order of microns in height. The aim of present work is to pursue design trends leading to surface shapes that will enable this interface to function at higher pressures than currently achievable. </p> <p> </p> <p>This pursuit takes the form of systematic virtual design studies, an optimization procedure, and an algorithm developed specifically for tailoring the bore surfaces through which the pistons travel to piston tilt and deformation. From this emerges not only a set of design trends corresponding to the dimensions of two particularly powerful types of micro surface shaping, but also a profound insight into the behavior of the water-lubricated piston-cylinder interface fluid film, and how that behavior can be manipulated by changing the component surfaces that constitute its borders. Furthermore, in collaboration with Danfoss High Pressure Pumps, a physical prototype of a 444 cc axial piston pump with surface shaping generated via the aforementioned algorithm has been constructed and tested, achieving a total pump efficiency roughly 3% higher than that achievable by the commercial unit that the geometry of the prototype is based on.</p><br></div>

Title: Understanding Area and Volume Formulae of Geometric Figures in the History of Mathematics and by Pupils Author: Bc. Adela Tavačová Supervisor: prof. RNDr. Ladislav Kvasz, DSc. The aim of this thesis is to describe the nature and possible causes of problematic areas in pupils' understanding of area and volume of geometric shapes and solids and treat this issue from the point of view of its ontogeny and phylogeny. Modern theories of gradual formation of the concepts of area and volume in pupils' minds will be characterized, together with the historical development of these concepts (from ancient Egypt and Greece to modern day). Complex analysis of the current Mathematics course books for primary and lower-secondary level is offered in the second part of the thesis. The analysis is based on the criteria following from the study of academic literature and on the historic research in this area. The aim of the analysis is to describe the way in which the course books treat geometric formulae and to what extent they respect their gradual development. In the final discussion, general aspects leading from the analysis will be summarized and offered as possible inspiration for pupils, teachers and future teachers of Mathematics. Key Words: formula, area, volume, algebraic language, hypothetical...

The desire to use more energy efficient heavy equipment in the earth-moving industry has rapidly increased due to higher environmental awareness. Studies within electrification and new types of hydraulic circuit architecture has shown great potential regarding energy savings. The advantages of implementing a closed, pump-controlled, hydraulic system for controlling the boom cylinder on the back-hoe of an articulated backhoe loader is evaluated in this thesis. The possibilities of electric energy regeneration is investigated and to what extent energy savings can be expected for the complete hydraulic system during normal operation. In order for pump-controlled systems to even be conceivable alternatives to conventional valve-controlled system, they must be able to achieve the same characteristics and driveability as the original valve-controlled systems. The possibilities of imitating the characteristics of a valve-controlled hydraulic system with hydro-mechanical pressure feedback is also investigated in this thesis. The original characteristic is able to be imitated with the implemented pump-controlled system with simple means by defining the current characteristic as the relationship between the operator input, cylinder load and cylinder flow. The evaluated sectioned hydraulic system demonstrates energy savings of 30% during both a light and a heavy duty cycle. With components more suitable for this type of system and an improved control strategy, energy savings of over 50% compared to the original system is believed to be possible.

A new invention has been developed by CorPower Ocean; a mechanical rack and pinion solution called a cascade gearbox. The primary function of the gearbox is transforming a linear motion into a rotational motion. The novelty is its unique properties; it is capable of combining heavy loads and high velocities, and at a high efficiency. CorPower Ocean is aiming at finding applications where the gearbox’s unique properties can be of use. If the gearbox is combined with a motor it forms an electromechanical actuator. Therefore, an investigation of applications using actuators has been targeted. More specifically, the master thesis assignment was to examine in which applications the transition of a cascade electromechanical actuator was technically viable. Research questions that derived was to answer if an implementation of an cascade electromechanical cylinder is technically feasible and if it implicates improved results regarding environmental related goals. The methodology executed to finalize the project included several stages. The first stage was the background study which consisted of reviewing trends and gathering technical data for case studies of targeted applications. The targeted applications were heavy lifting equipment and injection molding machines. With the help of CorPower software, gearbox dimensioning examples were drafted and could be evaluated from a size and weight perspective. To further evaluate potential applications, interviews were conducted with targeted equipment manufacturers. The selection of applications was completed by evaluating the interview responses and the drafted gearbox examples. Chosen applications were ultimately a nine tonnes forklift and an empty container handler, mainly due to good customer response, integration ability and potential of performance enhancement. An optimisation was performed to achieve a concept solution that satisfied customer needs such as low cost and a slim design. In order review the business cases in each application, energy savings and performance cases were conducted, benchmarking against the hydraulic solution. In the ECH case, the energy saved was 54% and the productivity increased with 9.6%. In the forklift case, the energy saved was 52% and the productivity increased with 1%. Both of applications have great potential of a transition from hydraulic cylinders to electromechanical cylinders in terms of implementation and technical feasibility. The final concept solutions exceeded the hydraulics in performance, retaining a slim and acceptable size and design. Furthermore, this sector of heavy lifting equipment had high potential for electrification which can contribute to reduced emissions and fuel savings. Keywords: electromechanical cylinders, concept development, cascade gearbox / En ny innovation har utvecklats av CorPower Ocean; en mekanisk rack och pinjonglösning kallad kaskadväxel. Dess primära funktion är att transformera en linjär rörelse till en roterande rörelse och vice versa. Nyhetsvärdet är växellådans unika prestanda; den kan hantera kombinationen av höga laster och höga hastigheter till en hög verkningsgrad. Nu önskar CorPower Ocean att hitta applikationer där kaskadväxelns unika prestanda kommer till användning. Om kaskadväxeln kombineras med en motor bildas en elektromekanisk aktuator, och därför har en utredning av applikationer som använder aktuatorer utsetts som en marknad att undersöka närmare. Mer specifikt var examensuppdraget att undersöka i vilka applikationer en sådan övergång skulle vara genomförbar ur ett tekniskt perspektiv. Forskningsfrågor som önskades besvaras var huruvida en sådan övergång är genomförbar ur ett tekniskt perspektiv och om en sådan implementation innebär förbättringar vad gäller miljörelaterade mål. Metodologin som användes för att slutföra projektet utgjordes av flera steg. Första steget var att genomföra en bakgrundsstudie om elektrifiering och produkttrender samt samla teknisk data på utsedda applikationer. De utsedda övergångsområdena var maskiner för tunga lyft samt plastformssprutningsmaskiner. Med CorPowers mjukvara kunde dimensioneringsexempel göras för kaskadväxellådor och utvärderas utifrån sin storlek och vikt. För en fortsatt utvärdering av applikationer genomfördes intervjuer med tillverkare av de utsedda applikationerna. Val av applikationer slutfördes genom att utvärdera svar från målkunder samt dimensioneringsexempel av växellådorna. De valda applikationerna blev slutligen en nio tons gaffeltruck och en tomcontainertruck. Valet baserades huvudsakligen på bra respons från kunder, bra integrationsmöjligheter samt potentiella prestandaförbättringar. Fokus låg på att byta ut lyftcylindrarna och bortse från övriga mindre cylindrar. Lösningarna optimerades för att matcha kundkrav så som kostnad och passform. Ett energibesparingscase utfördes för att jämföra kaskadlösningen med nuvarande hydrauliska lösning. I tomcontainertruckens fall sänktes energiförbrukningen med 54 % och produktiviteten ökade med 9.6%. I gaffeltruckens fall sjönk energiförbrukningen med 52 % och produktiviteten ökade med 1 %. Båda applikationerna uppvisade stor potential för ett byte från hydraulcylindrar till elektromekaniska cylindrar. De slutgiltiga koncepten överträffade hydraulikens prestanda medan de bibehöll en acceptabel storlek. Vidare fanns det en stor potential inom lyftindustrin att genom elektrifiering kunna minska utsläpp och bränsleförbrukning. Nyckelord: elektromekanisk cylinder, konceptutveckling, kaskadväxel

Interaction of fluctuating vortex shedding with blade vibration can lead to a new class of aeromechanical instability referred as Non-synchronous vibrations. Investigating a well-known case that shows similar NSV features such as a circular cylinder can develop the understanding of physics behind NSV. A common approach to further investigating the vortex induced vibration is to control the motion of the cylinder and allowing the response of the wake to the motion to be studied in isolation. It has been found very important to carefully match the experimental conditions between free and controlled vibration. Many of research in the field of vortex induced vibration apply a rigid cylinder mounted horizontally and moving transversely to the flow stream as a paradigm for understanding the physics behind this phenomenon. Regarding the difficulties of implementation of vertically moving cylinder in experimental study, vortex dynamic and lock-in behavior of eccentrically rotating cylinder is studied in this M.Sc. Thesis. The main focus of this research is to understand to what extend a general feature of free vortex-induced vibration can be observed in the case of eccentrically rotating cylinder. If the present case captures the essential characteristics of freely oscillating cylinder the results of the forced motion via eccentrically rotating cylinder can be applied to predict the motion of an elastically mounted body. To do so a CFD model is established to predict the response, vorticity structure in near wake, timing of vortex shedding and the range of lock-in region over specific parameter space of the introduced alternative case. A commercial CFD code, Ansys/CFX, was implemented to perform this numerical study. Existences of synchronization region, striking similarity in lift force coefficient and wake mode have been observed in the current study.

Preliminary designs for the cylinder heads of Scania’s next generation Diesel Engine have been investigated by the means of PIV measurements on a steady test rig. General structures present in the flow have been investigated, with a specific focus on Swirl motion due to its well documented impact on combustion efficiency and pollution generation. The first set of measurements was acquired in the tumble plane. A method to perform efficiently PIV measurements was introduced, which consists in rotating the experimental setup rather than the PIV measurement instruments. As a consequence, a considerable amount of work is saved and a great number of measurement planes can be acquired. This method has allowed to reconstruct a 3D3C picture of the flow in the cylinder. Such 3D3C direct measurement of flow in a test rig cylinder had not been reported previously in the literature, as far as the author is aware of it. The second set of measurements was acquired in the swirl plane. General patterns in the swirl velocity fields have been identified. The author introduces the hypothesis that shifting down the measurement position may, to some extend, be equivalent to observing the flow evolve in time in the real engine situation. Measurement performed far enough under the valves exhibit clear and stable swirling vortex structure with the cylinder heads investigated. This may explain for the validity of the combustion models used in the industry that, despite apparent over simplification of the flow situation, have proved in good agreement with engine tests.