The cylinder block/valve plate interface is a critical design element of axial piston machines. In the past, extensive work has been done at Maha Fluid Power Research center to model this interface were a novel fluid structure thermal interaction model was developed which accounts for thermal and elasto-hydrodynamic effects and has been proven to give an accurate prediction of the fluid film thickness. This paper presents an in-depth investigation of the impact of the elastic deformation due to pressure and thermal loadings of the end case/housing on the performance of the cylinder block/valve plate interface. This research seeks to understand in a systematic manner the sensitivity of the cylinder block/valve plate interface to the structural design and material properties. A comparison between simulations results is done by utilizing different end case designs and material compositions, both in the valveplate and end case solids.

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.

Cylinder seal impressions occur in many contexts in the ancient Near East. This disssertation focuses specifically on the function of sealing in the manipulation of state resources (land, labor, and goods) in second millennium B.C. Syria. The sources of information utilized in this study include textual references to sealing practices, sealed documents, bullae, and the seals themselves. The archives of Mari, Alalah, and Ugarit are particularly important as they provide textual and archaeological information on seals and sealing within the physical and institutional context of the palace, the center of state administration. Chapter 1 surveys the previous research on seals and sealing and briefly outlines Syrian geography and political history in the second millennium B.C. Chapter 2 examines the physical qualities of the seals--materials, methods of production, distribution and style. Chapter 3 addresses the problem of the physical and institutional context of seal use. A functional division between legal and administrative texts is reflected in the use of seals on them. On both types of documents, however, the use of a seal acknowledges the obligation of the sealer. The nature of that obligation varies with the contents of the text itself. Chapter 4 evaluates the use of seals on legal texts in palace archives. Most of these sealed documents record land grants. The historical trend in second millennium Syria is to an increasing involvement of heads-of-state in granting state land. Other sealed legal documents were kept in palace archives because the participants were in some way associated with the palace. Chapter 5 details the administrative use of seals at Mari. Receipts and expenditures are the most common sealed documents. The use of seals on these texts signals the acceptance by the sealer of responsibility for the goods or actions described therein. The conclusions (Chapter 6) summarize the differences in sealing practices in Mari, Alalah and Ugarit in light of the different historical circumstances and political needs of each state.

Controlled Auto-Ignition (CAI) also known as Homogeneous Charge Compression Ignition (HCCI) is increasingly seen as a very effective way of lowering both fuel consumption and emissions. Hence, it is regarded as one of the best ways to meet stringent future emissions legislation. It has however, still many problems to overcome, such as limited operating range. This combustion concept was achieved in a production type, 4-cylinder gasoline engine, in two separated tests: naturally aspirated and turbocharged. Very few modifications to the original engine were needed. These consisted basically of a new set of camshafts for the naturally aspirated test and new camshafts plus turbocharger for the boosted test. The first part of investigation shows that naturally aspirated CAI could be readily achieved from 1000 to 3500rpm. The load range, however, decreased noticeably with engine speed due to flow restrictions imposed by the low lift camshafts. Ultra-low levels of NOx emissions and reduced fuel consumption were observed. After baseline experiments with naturally aspirated operation, the capability of turbocharging for extended CAI operation was investigated. The results show that the CAI range could achieve higher load and speed with the addition of the turbocharger. The engine showed increased fuel consumption due to excessive pumping losses. Emissions, however, have been reduced substantially in comparison to the original engine. NOx levels could be reduced by up to 98% when compared to a standard SI production engine.

Approved for public release; distribution is unlimited / A FORTRAN 77 computer code employing an adaptation of the finite differencing algorithm proposed by Brian was developed for the solution of transient heat conduction problems in cylindrical geometries. Validation of code was accomplished by comparison with an ana­lytic solution derived for a model with symmetric, linear boundary conditions. Accuracy of results for asymmetric and non-linear boundary conditions was determined by comparison with a similarly vali­dated code employing the explicit method. Code effectiveness was then demonstrated by conducting a transient temperature analysis for a simulated earth-orbiting satellite. Brian's method demonstrated unconditional stability with associated significant reductions in execu­tion time compared to the explicit method. The effects of discretization error on the accuracy of results require further investigation. / http://archive.org/details/applicationofbri00hein / Lieutenant Commander, United States Navy

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Steve Eckels / A new human thermal model was developed to predict the thermal responses of human body in various environments. The new model was based on Smith's model, which employed finite element method to discretize the human body. The body parts in our new model were not limited to the cylindrical shape as in Smith's model, but subjected to arbitrary shapes. Therefore, the new model is capable of dealing with more complicated shapes of the human body. Steady-state and transient temperatures of fifteen body parts were calculated for three environments: cold, neutral, and warm. Our results were compared with the data from Zhang's experimental research on the human subjects. For all three conditions, our results showed better agreement with experimental data than Smith's results did. The maximal deviation is 1ºC for neutral and warm condition; for cold condition, a maximal deviation of 3.5ºC is reported at hand. The comparison indicated that our new model could provide a more accurate prediction on the body temperatures. Follow-up experiments were conducted to investigate the local and overall heat transfer from a moving cylinder in air flow. This study was expected to provide the local convective heat transfer coefficients of the human body to our new human thermal model to simulate moving humans. An experiment of a stationary cylinder in cross flow was performed to verify the accuracy and consistency of our system. Then, the experiment of a transverse oscillating cylinder in cross flow was conducted, with a oscillation frequency of 0.15 and Strouhal number of 0.3 to 1.5, depending on wind velocity. The overall Nusselt number (Nu) of the oscillating cylinder remained unaffected, compared to the stationary cylinder. This observation showed agreement with previous studies. The pivot experiment was performed to investigate swinging movement of human arms. The cylinder was positioned axially in cross flow, and reciprocated on a fixed point between horizontal and vertical positions under three wind speeds and two oscillating frequencies. The results showed that the overall Nu was between the Nu at horizontal and vertical positions in stationary state. A correlation was presented to predict the Nu of pivotal moving cylinder by using stationary Nu at horizontal and vertical positions. The correlation was proved to be valid ( error less than 5%) within the range of conditions in our experiment.

The four chapters of this diploma thesis introduce a survey of the basic intersection types of solids, the focus being placed on the intersection of two pyramid and prisma solids, acting as a counterweight to most textbooks' interest in intersection of curved surfaces. The first chapter provides a detailed, wide-ranging insight into the issue of the solid and line intersection. The conclusion part of the thesis provides the reader with a brief commentary on the used literature. The work is supplemented with figures and example solutions. In the appendix part are found pre-drawn assignments. The enclosed CD contains complementary materials such as step by step solutions and 3D models created in the GeoGebra software along with drawn problems found especially in upper secondary school geometry textbooks and curriculum.

Student Number : 9707408V - MSc(Eng) research report - School of Mechanical, Industrial and Aeronautical Engineering - Faculty of Engineering and the Built Environment / This research is an investigation into the performance and combustion characteristics of a two-cylinder, four-stroke compression ignition engine fuelled on diesel and then on dimethyl ether (DME). Baseline tests were performed using diesel. The tests were then repeated for dimethyl ether fuelling. All DME tests were performed at an injection opening pressure of 210 bar, as recommended for diesel fuelling. The tests were all carried out at constant torque with incremental increases in speed and an improved method of measuring the DME flow rate was devised. It was found that the engine’s performance characteristics were very similar, regardless of whether the engine was fuelled on diesel or DME. Brake power, indicated power and cylinder pressure, during the highest loading condition of 55 Nm, were virtually identical for diesel and DME fuelling, with the most significant finding being that the engine was more efficient when fuelled on DME than when fuelled with diesel. Another interesting finding was that the energy release of diesel decreases with increasing load, whilst the energy release of DME increases with increasing load. At the highest loading condition of 55 Nm, the energy release of DME was approximately 210 joules higher than that of diesel. This investigation concluded that DME may definitely be a suitable substitute fuel for diesel.