<p dir="ltr">This research developed a lumped volume-based coupled simulation model for gear pumps and motors, which is employed to analyze a reference machine of a compensated crescent- type internal gear pump. The model is composed of simultaneous simulations of the pump fluid domain pressure, lubricating films, and dynamics of the moving components.</p><p dir="ltr">The simulation model developed includes four major novel contributions.</p><p dir="ltr">1. A coupled simulation model was developed for the reference machine which provides (a) a lumped parameter simulation of the fluid pressure within the inter-teeth volumes, (b) CFD simulations of the lubricating interfaces, and (c) a simulation of the micromotion of the pressure compensating components and gear bodies. The simulation tool is developed in C++ and constitutes the simulation core of Multics for internal gear pumps. The model achieved volumetric and mechanical predictions for the reference type of machine, which are validated via experimental investigations.</p><p dir="ltr">2. A flexible pressure solver was established to solve the pressure transience in the fluid domain in gear pumps with general CV geometry exemplified in the reference machine. The approach allows for ample freedom in defining control volumes, including possible volume discontinuities. The new formulation, derived from mass conservation, avoids the numerical evaluation of the volume derivatives so that it allows for simulating a control volume layout with sudden shape changes. The new formulation also considers the sliding motion from volume boundaries when evaluating internal flows, which improves the accuracy of the control volume pressure solutions. The effectiveness of the proposed formulation was examined by applying the method to the simulation of the reference machine. Compared with the state-of-the-art simulations, several improvements in the pressure simulation were observed : (i) the proposed formulation provides free-of-spike fluid pressure simulations, even for discontinuous volumes; (ii) the proposed formulation properly captures the flow component between volumes that is caused by the volume boundary motions, a term previously neglected, which affects the pressure evaluation accuracy, especially in gear meshing zone.</p><p dir="ltr">3. The swift film coupling algorithm proposes a novel artificial inertia damping-based method (AIDM) to simulate this coupling. The proposed method considers modifying the physical body dynamics with artificial inertia and damping values that could achieve significant numerical solver accelerations while maintaining extremely low errors. The artificial inertia and damping are determined based on the instantaneous physical system’s Jacobian so that the first-order dynamics in the solution can be conserved from the original dynamic system. The solver acceleration capability is quantified in time-discretization-based derivations, where additional guidelines for determining the artificial inertia and damping values are found. The proposed approach is used to simulate two model problems for a 1-D slider pad under periodic loading conditions, where one pad is fixed inclined and the other free to move vertically and rotate about its center. Simulation results reported an error lower than 0.01 μm in the gap height geometry prediction by the proposed AIDM approach compared to the state-of-the-art Reynolds film damping-based method (RDM). Meanwhile, the numerical solver speed improved 1000 times for the fixed incline pad problem and one hundred thousand times for the free-to-float pad problem. Derivations showed that additional acceleration potential can be achieved in realistic mechanical systems where a higher degree of freedom is present in the body motions. The error behavior of the proposed AIDM approach is discussed, showing the error is positively related to the absolute magnitude of the modification parameter ϕ used for calculating the artificial inertia and damping, and the error is related to the validity of the linearization assumption on the system dynamics.</p><p dir="ltr">4. Based on a novel experimental set-up to measure the filling characteristics of an internal gear pump under induced gaseous cavitation. An integrated simulation approach was proposed to study the incomplete filling behavior in positive displacement machines. The approach consists of (a) a 1st order predictive model for evaluating the amount of undissolved gas at the pump inlet from the circuit pressure loss, (b) a gas-equilibrium-based cavitation model for predicting the pressure transience in the pump fluid domain, (c) a lumped volume based pump flow evaluation. Experiments performed over a wide range of operating conditions validated the deployment of the first-order gas release prediction (with 8 s time constant for fluid with 6 % total air). The complete simulation approach was validated via a good match with the measured volumetric efficiency for both low-speed and high-speed conditions.</p><p dir="ltr">The reference compensated crescent-type internal gear pump (CCIGP) unit was simulated with the full scope coupled simulation model, with which the methods proposed in this thesis research were validated with experiments. Simulation results matched with volumetric efficiency as well as mechanical efficiency. The model also reports a breakdown of the energy consumption within the reference CCIGP, which promotes the understanding of the operation of the reference machine.</p>

This paper describes a novel concept for a low cost variable delivery external gear pump (VD-EGP). The proposed VD-EGP is based on the realization of a variable timing for the connections of the internal displacement chambers with the inlet and outlet ports. With respect to a standard EGP, an additional element (slider) is used along with asymmetric gears to realize the variable timing principle. Previously performed tests confirmed the validity of the concept, for a design capable of varing the flow in the 65%-100% range. Although the VD-EGP concept is suitable for various flow control system typologies (manual, electro-actuated, hydraulically flow- or pressure- compensated), this paper particularly details the design and the test results for a prototype that includes both a manual flow control system and a pressure compensator. Flow vs pressure and volumetric efficiency curves are discussed along with transient (outlet flow fluctuation) features of the VD-EGP.

In the vehicle industry it is of great interest to reduce the emissions and lower the fuel consumption.Up to now a lot of effort has been put into increasing the efficiency of the engine,but it starts to get expensive to keep improving the engine. In this master thesis the transmissionand especially the oil supply to the transmission is investigated. An example of how the requirements of an oil pump can be decided is described. Knowingthe requirements different pumps may be adapted to meet the demands. The gear pumpused today is compared with a variable displacement pump and an electric pump. The gearpump is not possible to control, but the other two are. A few simple control strategies areintroduced. The strategies are implemented and the three pumps are used in the same drivecycle. It is shown that it is possible to reduce the energy that the pump requires if it isreplaced by a variable vane pump or an electric pump.

<div>Gerotor pumps are positive displacement pumps that are frequently used in low-pressure applications such as lubrication and charge pumps. They are characterized by their unique gearset that is an internal gearset with one tooth difference that has continuous contact throughout the entire rotation. Recent trends especially in the automotive industry suggest an increased demand for greater performance from these pumps, e.g. operating with higher pressure, higher speed, lower viscosity fluid, less noise emission, and greater energy efficiency. The shape of the gears is one of the most important aspects of a gerotor pump, as it determines the pump's size and flow, affects its internal leakages, and influences its amount of wear. Although gerotors have been in operation for nearly 100 years, no design methodology has emerged in scientific literature that fully considers all the main performance aspects simultaneously and identifies the best designs. This problem is made more difficult, as gerotors can have an infinite number of different types of profiles. The main goals of this work are therefore to define a method to design gerotor gear geometry for several performance goals, identify the best designs for a given gear profile type, compare the best designs among the various profile types, and invent a new profile type that can offer improved performance over conventional designs.</div><div><br></div><div>Gerotor profile generation is described in the beginning, first for the conventional epitrochoidal, hypotrochoidal, and standard cycloidal profile types. Then a description of how to generate gerotors from an arbitrary curve is given and applied to elliptical, generalized cycloidal, cosine, and asymmetric elliptical gerotors. The generalized cycloidal profile type is new to this work.</div><div><br></div><div>Multi-objective optimization is used as the method to identify the best gear profiles for a given application considering seven performance metrics and ensuring a feasible gear profile. The seven performance goals to minimize are the radius of a pump for a given geometric displacement and face width, the kinematic flow ripple, the adhesive wear, the contact stress, the tooth tip leakage, the lateral gap leakage, and the mean displacement chamber inlet velocity. The conditions to generate feasible gerotor profiles without cusps or self-intersections are also given as constraints for the optimizations.</div><div> </div><div> Seven gerotor profiles were then optimized using a genetic algorithm to consider all the performance aspects. The design space for each profile type was thoroughly explored, and clear Pareto fronts were identified. The Pareto fronts from each profile type were then combined, and a new Pareto front was identified from the best designs of each profile type. No single profile type proves to be objectively better than the others, but the epitrochoidal, hypotrochoidal, elliptical, and generalized cycloidal profile types tend to produce the best designs. Two methods to select a design from the Pareto front that consider the relative importance of each performance goal were presented.</div><div> </div><div> The optimization strategy was then further validated by demonstrating significant possible performance improvement over state-of-the-art designs in industry and suggesting alternative designs to a specific gearset used in industry that were tested in simulation and experiment. Two generalized cycloidal profiles were selected as alternative designs: the first design matched the fluid dynamic performance of the reference design with significantly reduced contact stress, and the second is a profile that could reduce the outlet flow ripple while fitting within the same pump housing. The contact stress of the reference and alternative designs when including clearance between the gears was compared in finite element analysis. Prototypes of the alternative designs were then manufactured and tested in experiment. The experimental pressure ripples of the alternative designs were compared, and the second design showed a reduction in outlet pressure ripple that validates the proposed design methodology.</div><div> </div><div> This work has thoroughly explored the performance possibilities of the gerotor mechanism and presented a method to select an optimal profile geometry depending on the desired performance characteristics. It has therefore accomplished its goals in making a contribution toward improving the performance gerotor gear geometry.</div>

This diploma thesis describes the design of equipment for static and cyclic loading of coolers by pressure. The aim is to first identify the necessary parameters from the tested coolers. Then, based on the obtained data, design the hydraulic circuit, including the parameters of individual components and motors, followed by the design the control logic, which is required for designing the control system.

This paper describes a novel concept for a low cost variable delivery external gear pump (VD-EGP). The proposed VD-EGP is based on the realization of a variable timing for the connections of the internal displacement chambers with the inlet and outlet ports. With respect to a standard EGP, an additional element (slider) is used along with asymmetric gears to realize the variable timing principle. Previously performed tests confirmed the validity of the concept, for a design capable of varing the flow in the 65%-100% range. Although the VD-EGP concept is suitable for various flow control system typologies (manual, electro-actuated, hydraulically flow- or pressure- compensated), this paper particularly details the design and the test results for a prototype that includes both a manual flow control system and a pressure compensator. Flow vs pressure and volumetric efficiency curves are discussed along with transient (outlet flow fluctuation) features of the VD-EGP.

The aim of the diploma thesis was to analyze qualitative outages in the production of gears for a gear pump and to minimize them. The largest amount of outages was caused by the burning of the surface during face grinding. After analyzing the current state of production there were created some suggestions to avoid this issue. Also there was found some space to speed up the whole process. Suggestions to eliminate burning have been tested with minimal impact on production. The reduction of outages for burned surface was achieved and also the cycle time was shortened. Those suggestions will be implemented in serial production.

This thesis presents a novel, low cost, high precision , and efficient design for an electro-hydrostatic circuit for single rod hydraulic cylinders. The design is the main contribution of candidate to fulfill the regiments of PhD degree. The challenge of existing deigns of electro-hydrostatic circuits for single-rod cylinders is using one pump to control the cylinder under switching (resistive-assistive) loads. The proposed circuit utilizes off-the-shelf industrial elements. It uses two counterbalance valves to manage switching loads and one on/off solenoid valve to redirect the differential flow of the single rod cylinder to tank. A set of simulation studies is conducted using Simhydraulic tools of Matlab in order to study performances of the proposed circuit and compare it with existing designs. Pump-controlled hydraulic circuit for double rod cylinders was developed and is widely used by industry. It is used as the benchmark for simulation studies. As well, the proposed circuit and two major existing pump-controlled circuits for single rod cylinders are compared to the benchmark circuit. Evaluations are conducted by comparing chamber pressure responses as well as pressure vs position of the cylinder end-effector for each individual circuit. Results indicate that the proposed circuit performed as well as the benchmark circuit by controlling pressures to both sides of the cylinder at the same time. Moreover, the load in the proposed circuit is more controllable compared to the benchmark circuit. Experimental results, obtained from the developed test rig, validate accuracy of the simulation model. Maximum steady state position error of 0.06 mm applications is experimentally observed when the test rig is tested under different loading conditions with various amplitudes and frequencies. The circuit consumes up to 20% of the energy that is required by a valve controlled circuit given the same sinusoidal tracking signal. The relative efficiency of the proposed circuit over a valve xii controlled circuit depends on the pattern and frequency of the tracking signal. In all the experiments, a simple proportional controller, which uses readings of a linear position transducer, is employed. The use of the proportional controller makes the proposed circuit easy to implement and shows it is good candidate for industrial applications. The accuracy of the position response of the proposed circuit indicates, it is a good candidate for robotic applications too. / May 2016

The objective of this diploma study is to develop and secure production of gear turbine with very low specific speed in comparison with conventional turbines. The first part of the work deals with already performed research of similar hydrostatic turbines. It is followed by construction design, including complete drawing documentation. The production of the prototype is secured by an external company. Finally, an experimental measurement of the characteristics of the designed turbine is performed in the laboratories of Fluid Engineering.

External gear machines (EGMs) are used in a variety of industries ranging from fluid power machinery to fluid handling systems and fuel injection applications. Energy efficiency requirements and new trends in hydraulic technology necessitate the development of novel EGMs optimized for efficiency and reliability in all of these applications. A crucial piece in the novel EGM development process is a numerical model that can simulate the operation of EGM and predict its volumetric and hydro-mechanical performance.<div><br></div><div>The EGM simulation models developed in the past have focused mostly on the challenges related to the modeling of the theoretical behavior and elementary fluid dynamics, and determining appropriate modeling schemes. Key aspects related to the flow and geometry are either considered in a simplified manner or not considered at all. In particular, the current simulation models assume the fluid to be Newtonian and the leakage flows to be laminar. However, EGMs working in fluid handling applications operate with non-Newtonian fluids. Further, in fuel injection applications, due to low fluid viscosity and high operating speed, the internal leakage flows may not remain laminar.</div><div><br></div><div>With respect to the geometric aspects, the gears in EGMs are prone to manufacturing errors that are not accounted by any simulation model. In addition, there is no method available in the literature for accurately modeling the leakage flows through curve-constricted geometries in EGMs. Further, the goal of current simulation tools is related to the prediction of the volumetric performance of EGMs. However, an equally important characteristic, hydro-mechanical performance, is often ignored. Finally, the energy flow during EGM operation can result in the variation of the fluid temperature. Thus, the isothermal assumption of current simulation tools is another major limitation.</div><div><br></div><div>The work presented in this dissertation is focused on developing numerical methodologies for the modeling of EGMs that addresses all the aforementioned limitations of the current models. In this work, techniques for evaluating non-Newtonian internal flows in EGMs is developed to permit an accurate modelling of EGMs working with non-Newtonian fluids. For fuel injection EGMs, flow regime at the tooth tips of the gears is investigated and it is shown that the flow becomes turbulent for such EGMs. A methodology for modeling this turbulent flow is proposed and its impact on the performance of EGMs is described. To include gear manufacturing errors in the simulation model, numerical techniques are developed for modeling the effects of two common gear manufacturing errors: conicity and concentricity. These two errors are shown to have an opposite impact on the volumetric efficiency of the EGM. For the evaluation of flows through curve-constricted leakage paths in EGMs, a novel flow model is developed in this work that is applicable for a wide range of geometry and flow conditions. Modeling of the hydro-mechanical efficiency of EGMs is accomplished by developing methodologies for the evaluation of torque losses at key interfaces. Finally, to account for the thermal effects in EGMs, a thermal model is developed to predict the temperature distribution in the EGM and its impact on the EGM performance.</div><div><br></div><div><div>To validate the numerical methodologies developed in this work, several experiments are conducted on commercial gear pumps as well as on a custom apparatus designed and manufactured in the course of this research work. The results from the experiments are found to match those obtained from the simulations which indicates the validity of the methodologies developed in this work. </div><div><br></div><div>These numerical methodologies are based on the lumped parameter approach to allow the coupling with mechanical models for gear micromotion and permit fast computations so that the model can be used in optimization algorithms to develop energy efficient and reliable EGMs.</div><div><br></div><div>The methodologies described in the dissertation are useful for accurate analysis of a variety of EGMs working with different types of fluids and at wide range of operating conditions. This capability will be valuable for pump designers in developing novel better performing EGM designs optimized for various applications.</div><div><br></div></div>