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Abstract:The trochoidal-gear technology has been growing in groundbreaking fields. Forthcoming applications are demanding to this technology a step forward in the conceiving stage of positive displacement machines. The compendium of the qualities and the inherent characteristics of trochoidal-gear technology, especially towards the gerotor pump, together with scale/size factor and magnetic-driven transmission has led to the idea of a magnet-sleeve-sealed variable flow mini trochoidal-gear pump. From its original concept, to the last phase of the design development, the proof of concept, this new product will intend to overcome problems such as noise, vibration, maintenance, materials, and dimensions. The paper aims to show the technological path followed from the concept, design, and model, to the manufacture of the first prototype, where the theoretical and numerical approaches are not always directly reflected in the prototype performance results. Early in the design process, from a standard-commercial sintered metal mini trochoidal-gear unit, fundamental characteristics and dimensional limitations have been evaluated becoming the strategic parameters that led to its configuration. The main technical challenge to confront is being sealed with non-exterior driveshaft, ensuring that the whole interior is filled and wetted with working fluid and helping the hydrodynamic film formation, the pumping effect, and the heat dissipation. Subsequently, the mini pump architecture, embodiment, methodology, materials, and manufacture are presented. The trend of applications of polymer composite materials and their benefits wanted to be examined with this new mini pump prototype, and a pure polyoxymethylene mini trochoidal-gear set has been designed and manufactured. Finally, both the sintered and the polymer trochoidal-gear units have been experimentally tested in an in-house full-instrumented mini test bench. Although the main goal of the presented work is the development of a new mini trochoidal-gear pump prototype rather than a numerical study, the results have been compared with numerical simulation. Subsequently, the prototype of the mini trochoidal-gear pump is a feasible proof of concept supported by functional indexes and the experimental results.

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This paper presents the modifications that have been made to the sickle insert of the gear pump with internal gearing. This procedure allowed the obtainment of radial compensation. The test stand to plot the characteristics of the pump before, as well as after the first and second modification is discussed. The results of the measurements from the tests conducted are presented. The results obtained confirmed the achievement of radial compensation by cutting the appropriate channel in the sickle insert. As a result, it will be possible to obtain a higher discharge pressure for this type of pump and to increase its efficiency.

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Using elements made of plastics in hydraulic drives and controls encounters problems, for example related to strength. However, the advantage of solutions with plastics manifests itself, among others in possibility of shaping hydraulic elements in accordance with the assumed requirements. The use of additive manufacturing techniques allows us to make plastic parts with shapes that are unattainable for steel parts. The authors have attempted to determine the influence of the shape of the closing element on the phenomena of flow through the throttling gap in the hydraulic throttle valve. They chose three poppets of different shapes and carried out flow simulations using CFD. They compared simulation results in the form of flow velocity field in the valve chamber with observations obtained with the Particle Image Velocimetry (PIV) technique. In visualization tests, a throttle valve made of transparent materials and markers in a form of air bubbles were used. The tests confirmed the possibility of using air bubbles as markers of the PIV method at low pressure. The presented conclusions indicate the need for further modification of the shape of the closing element as well as of the design of the valve body.

Chambers in the Gerotor pump units are separated by metal-to-metal geometrically form-closed higher pair active contacts in the lobes of star and ring components. With rotation when the chamber volumes expand and contract, the active contacts move on lobe profiles and are subjected to deformations due to contact stress caused by fluid pressure and transmitted torque. Evidently at two transition active contacts, which separate the high-pressure chambers from the low-pressure chambers, gaps are generated due to contact deformations. However, it is for a short period of time during operation and mostly not at the same time in the two transition contacts. From our experimental visual investigation by photoimaging technique on flow processes, we have visualized that at some angular positions of the star–ring, cavitation occurs inside the chamber. In an earlier work, in the estimation of gaps in transition contacts, we have first evaluated the stresses, deformations at all ideally form-closed active contacts in our chosen Gerotor pump using static structural analysis in the Ansys® environment. In the present work, to investigate the flow characteristics, including the formation of cavitations in the Gerotor pump, numerical analysis using the computational fluid dynamics tool in the Ansys® environment has been carried out. We analyze the flow process for the different angular positions of a star. Results obtained by the numerical analysis have good agreement with the flow patterns visualized experimentally.