In a world with high energy cost, the efficiency of motors becomes increasingly important. Thereby, the understanding of loss mechanics is of great significance and having accurate simulation models for the efficiency of motors is crucial.    Bosch Rexroth Mellansel has developed a new radial piston hydraulic motor with high power, capable of operating at high torque and speed. In this master thesis the newly developed motor will be examined and undergo a lab test to determine its efficiency. The results from this will then be used to improve the current simulation model and aim for a physical model that align with the efficiency results. Furthermore, the loss mechanics of the motor is important and will be studied during this thesis. The loss mechanics in a motor can be split into two parts, hydro-mechanical and volumetric losses. Hydro-mechanical losses refer to the losses due to both friction and hydraulic flow. The losses in the fluid flow are in turn divided into two parts, the major losses and the minor losses which are the friction losses in the fluid and the losses due to geometric changes in the channels respectively. The volumetric losses are on the other hand the losses from internal and external leakage of the hydraulic fluid, and compression flow which is the extra flow that occurs when the fluid changes density.  In order to determine efficiency values from a radial piston hydraulic motor, a test specification was written containing the information needed to perform the test, including two different methods, the pressure and torque method, and the sensors needed to measure the different parameters. For the hydro-mechanical efficiency the uncertainty is 0.1% for the pressure method and 0.15% for the torque method. The test was performed for several different rotational speeds and different pressure points. An improved model was developed from the test results by testing and optimization, and it was found that having the losses due to geometric changes in the channels, depend on Reynolds number agreed better with the test result. However, the improved simulation model does not align as well with the test result for all measured points. Hence a further investigation on the friction model and the dependence on pressure might improve the model further. However, it was found that for a specific sub test, the new model had a mean difference from the pressure method test result of 10^-3. While the mean difference for the unaltered simulation model was 10^-2, hence the new simulation model is an improvement. Therefore, the outcome of this master thesis is an improved simulation model for the newly developed radial piston hydraulic motor QMp 560-560 but also for future motors to come.

<p>Energy conservation is a growing topic of research within various fields.  Digital Hydraulics is a division of fluid power that focuses on using on/off technology to improve the performance and efficiency of fluid power systems. One significant benefit of Digital Hydraulics is that it has enabled additional control over fluid power systems, which helps achieve component and system level improvements. Conventional radial and inline piston pumps use positive sealing valves, which mitigate leakage losses, compared to port plates commonly seen in variable displacement pumps. By using digitally controlled positive sealing valves on radial and inline piston pumps, leakage losses can be mitigated to develop a more efficient variable displacement pump. This work focuses on the design, modeling, and simulation of a mechanically actuated valving system developed for a commercially available radial piston pump. The design uses a ball screw actuation method to phase the cam during operation, changing the displacement. Using a modeling and simulation software, GT-SUITE, a simulation model was created for the digital pump that shows close correlation to the manufacturer’s data at high pressure. The parameters simulated, 50 – 200 bar, showed that the system could achieve a peak efficiency drop of approximately 11.0% from 87.0% to 76.0% from 100 – 25% displacement simulated at 200 bar and 500rpm. Compared to a typical variable displacement axial piston pump unit, the digital pump showed increased efficiencies across the bandwidth of 35-83% displacement, with a lower overall drop in efficiency across most of its operating conditions. In the comparison used, the pump is outside of its operating range and has not been optimized; thus, the simulation model created in this thesis will be used in the future to optimize the system and evaluate the system's potential performance and feasibility for future prototyping and testing as a proof of concept.  </p>

This report covers the work and results of the thesis project in Mechanical Engineering from Luleå university of technology performed by Niklas Ydebäck. The objective of the thesis project is to research if it is possible, with general principles of fluid flow between components and the corresponding geometric constraints between them and just a few channels of data, to model the leakage of a radial piston hydraulic motor. The model is of the grey box kind which makes use of both numerical and statistical methods together with known physical properties of a system in order to model the system. The unknown parameters of this system that are estimated using the least squares method are the three different gap heights of the system as well as the two different eccentricities in the system. The model contains the physical properties of the system, stated in equations for the leakage in the relevant lubrication interfaces, but no relational properties for the dynamics and affects between the individual lubricating interfaces. The model developed is due to the model generality together with the data quality accessible not able to model the system with reliable quality. The model is however able to capture the general trend of the leakage in the system over the applied time series datasets. / Den här rapporten presenterar arbetsgången och resultatet av examensarbetet för en civilingenjörsexamen i Maskinteknik från Luleå tekniska universitet utförd av Niklas Ydebäck. Målet med examensarbetet är att utvärdera och undersöka om det är möjligt, med generella och vedertagna principer av fluidflöde mellan smorda komponenter tillsammans med de geometriska begränsningarna som hör dem till och några få kanaler av data, att modellera läckaget för en radialkolvsmotor. Modellen är en grålådemodell som med hjälp av numeriska och statistiska metoder och kända fysikaliska principer av ett system bildar en modell av systemet. De okända parametrarna av systemet som estimeras med hjälp av minsta kvadrat metoden är de tre olika typerna av spalthöjderna och de två olika eccentricitetstyperna som finns i systemets smorda kontakter. Modellen består av de fysikaliska egenskaperna i systemet, formerade i ekvationer för läckaget i de relevanta smorda kontakterna, men inga relationella egenskaper för dynamiken och effekterna mellan de olika smorda kontakterna. Den utvecklade modellen är på grund av den generella karaktären av modellen tillsammans med kvaliteten på den data som finns tillgänglig inte möjlig att modellera läckaget i systemet med tillräcklig noggrannhet. Modellen är trots detta kapabel att fånga de generella trender som återfinns i den uppmätta datan på läckaget för de applicerade dataseten.