Maha Fluid Power Research Center hosts cutting-edge research in hydraulics and fluid power. From computer modeling of pumps and motors, to experimental verification on real-world equipment, every aspect of fluid mechanics is explored at Maha.
Various projects have been performed in the area of external gear units. Purposes of these projects are: the development of accurate simulation models; the proposal of new solutions characterized by better efficiency and lower noise emissions; the development of innovative testing techniques. Here's a detailed PDF about Maha research on gear pumps and motors.
The main result of the research activities in external gear machines is given by the simulation tool HYGESim. HYGESim (HYdraulic GEar machines Simulator) is a numerical model for the simulation of external spur gear pumps and motors. Conceived at University of Parma (Italy) with the support of the company CASAPPA, HYGESim is currently developed at MAHA Fluid Power Research Center.
The simulation tool consists of different modules: a lumped parameter fluid dynamic model, a mechanical model for evaluation of the gears motion (considering also the micro motion of the gear axes of rotation) and a geometrical model. The first two models are implemented within the LMS Imagine.Lab AMESim® simulation environment, with proper submodels written in C language, while the geometrical model is implemented developing proper macros capable to read directly the CAD3D drawings of the unit (pump/motor).
The simulation tool is characterized by an accurate description of the geometry of the different components (i.e. teeth’s profile, design of sliding elements) and it is able to calculate the movements of the gears’ axes of rotation resulting from the forces exerted on both gears. Potentials of the model are represented by the prediction of the main features of flow through the machine (such as the inter-teeth meshing pressure, the evaluation of possible cavitation onsets, pulsation of flow at the external ports, etc.) and the detection of the wear of the casing due to the possible contact between the gears and the casing. The tool is currently used for the analysis of the main phenomena related to the operation of the machine, for the optimization of its design and for the research of innovative solutions.
Noise generation in the pumps and motors is commonly classified into three categories in many studies of noise in hydraulic applications: fluid-borne noise (FBN), structure-borne noise (SBN), and air-borne noise (ABN). To have better understanding of noise generation in external gear machines, a complete FBN-SBN-ABN model has been developed using proper methodologies for each domain. HYGESim provides all the FBN sources inside the units. For the prediction of the SBN and the ABN, a combined FEM/BEM approach is used in conjunction with mapping the predicted FBN sources as loads to the pump structure. The model is suitable for quieter pump design through virtual prototyping methods based on numerical optimization without negatively affecting the energy efficiency. The model is also suitable to separate and quantify the different FBN and SBN sources to the ABN noise. In this way, general design guidelines will be provided to the technical fluid power community involved in pump design efforts.
Given the importance of efficiency in any mechanical system, in recent years, displacement control of pumps has gained a lot of attention in the field of fluid power. Gear pumps have a lot of advantages in that they are of simple design, fewer moving parts, easy to maintain and very compact. However, gear pumps available in the market today are fixed displacement. By allowing variable displacement, the advantages of gear pumps can be utilized in wider applications.
The project aims to demonstrate the commercial viability of a Variable Displacement Gear pump using a novel principle. The idea of changing the displacement is based on varying the timing of the connections of the Tooth Space Volumes (TSV's) with the inlet and outlet grooves. We achieve this by introducing a movable element, called "slider." In traditional pumps the grooves are machined onto the lateral bushings. The slider element allows us to change the position of the inlet and outlet grooves with respect to the TSV's.
For this project, a parametric optimization to increase the displacement reduction of the gear profiles was performed in modeFRONTIER. The performance of the optimized pump was simulated in HYGESim. The project aims to build prototypes for different pressure applications. One for high pressure (~200 bar) and another for lower pressure (~15 bar). The high pressure prototype has been built with a pressure compensated design. It was tested and the prototype was able to implement the pressure compensation principle. Currently the design of the low pressure prototype is being finalized. This prototype will be capable of electronic displacement control. This is achieved by controlling the slider position using an electro-mechanical actuator like a solenoid or stepper motor.
The research on fluid properties modeling is aimed to find formulations suitable to describe peculiar flow features within hydraulic components, such as the cavitation, the effect of temperature and pressure, and the presence of dissolved or non-dissolved air. The main aim is to develop formulations suitable for fast simulation models, such as lumped parameters models.
The modeling approach consists of a few basic modules which are interacting in different domains. It comprises models for the parametric geometry generation (gear teeth profiles and porting geometry), a lumped parameter fluid dynamic model for the evaluation of the main flow features, a geometric model for the numerical calculation of relevant geometry data (variable chamber area, intersection zones between displacement chambers and inlet/delivery ports), a CFD model for the analysis of the lateral leakage flow. Furthermore, a 3D CAD model integrated to a FEM model is implemented to allow automatic generation of detailed drawings and to permit material deformation/stress analysis. Finally, a model of the hydrodynamic lubricated outer rotor bearing is integrated within the fluid dynamic model.
With the support of MAGNA Powertrain the developed models have been successfully validated with experimental results for different pump designs for both, steady state and transient pump operation. The developed model permits the analysis of main design parameters on machine performance, in particular as concerns unit's efficiency, pressure/flow pulsations, leakage flows and torque losses. Different design concepts can be validated with consideration of the respective application (e.g. when working in a complete hydraulic circuit for a specific actuation system).
Various activities have been performed concerning the modeling and testing of hydraulic systems and components (with particular reference to hydraulic valves). These projects show the capability of simulating not only the main phenomena related to the internal flow, but also the interaction between the internal parts (the mechanical elements and the electro-magnetical actuation system, if present) and between the other components present in the considered system. Moreover, the aspect related to the possible control strategies are accounted as well.
In few cases, advanced optimization criteria have been used to improve current designs or to formulate new solutions. All developed models were validated on the basis of experimental measurements. For systems, the considered cases are pertinent to hydrostatic transmissions and to other hydraulic systems for mobile applications. In these cases, lumped parameters models were developed with the aim of analyzing the margin of improvements of current solutions and to design innovative systems.
In order to perform an estimation of the energy consumption and possible improvements, a study was conducted on a reference crane by changing the settings. Two typical operating cycles were considered for the study, in order to investigate the overall operation of the machine (lifting/lowering, with/without load). A detailed AMESim model, created to model the behavior of the valve, supported this activity. After extensive testing, it was found that the energy consumption on the crane was indeed significantly reduced by the inclusion of the new control structure.
Along with the testing of the control structure for vibration reduction on the hydraulic crane, applications in mobile hydraulic machinery have also been considered. The specific machine which was considered for this implementation is a wheel loader. Much like with the crane, computer simulations were conducted using a model of the wheel loader to determine the viability of using actuator motion to damp system vibrations. After the simulations showed positive results, experimental tests were conducted on a wheel loader. These tests have indicated that the control strategy is also capable of damping vibrations in mobile hydraulic applications.
Research in this area aims to develop and promote hydraulic power trains of all kinds while focusing on novel applications of hybrid technologies and advanced power train and power management control strategies for both off- and on-road vehicles. Each topic studied within this area is encompassed in the primary goal of improving efficiency to reduce fuel consumption and emissions for different kinds of vehicles. The Maha lab features two hardware-in-the-loop (HIL) transmission test rigs and a prototype hydraulic hybrid SUV to support the development and demonstration of new transmission concepts. The lab is also strong in modeling of transmission concepts for all vehicle classes and types. General research activities in this area can be summarized into:
Generic methods for online and on-board condition monitoring of hydraulic systems of off-road machinery are under development. The methods will indicate impending failures of complex hydraulic systems, even those that are properly maintined. The research also includes new concepts for active vibration control of off-road vehicles through the use of energy saving displacement controlled actuators, providing:
Displacement controlled linear and rotary actuators are being proposed and invesitgated as possible solutions for substantial energy reductions in fluid power systems. The research focueses on new circuits, advanced control concepts, and power management strategies for multi-actuator, displacement controlled, systems. By replacing current resistance, or valve, controlled actuators, throttling losses can be nearly eliminated allowing for major fuel savings, while also allowing for the possibility of energy recovery during aiding loads. Feedback control, path coordination, and path optimization additionally increase machine productivity, effectively saving even more fuel to accomplish the same task. Details include:
The goal for this area of research is to understand the sources of noise within hydraulic systems. The use of complex hydraulic systems has led to the demand for a more comprehensive understanding of audible noise. The utilization of axial-piston based hydraulic systems by numerous industries with a wide range of operating conditions has motivated our research to center on the design of a pump/motor or system. The Airborne Noise (ABN) emitted from the hydraulic system can be attributed to two main sources, namely, Fluid Borne Noise (FBN) and Structure Borne Noise (SBN). It is important that all projects consider both sources of noise. Our custom software tools aid in reducing both of these primary noise sources. The full scope of research in this area includes: