Validation of a coupled multibody and TEHL simulation by a piston/cylinder component test rig

A tribological highly stressed contact in the actuating system of axial piston machines is located between the control piston and the control chamber. This paper presents a new type of component test rig for measuring the frictional force and the gap heights between piston and cylinder. For this purpose, the original system is reduced to the actuator system, whereby the real kinematics and the loading forces are maintained. The axial movement of the control piston and the pressure in the control chamber can be configured individually. The measurement results of different parameter variations are compared with the results of the simulation. The simulation based on a coupled multibody and TEHL simulation with a transient, three-dimensional, thermal elastohydrodynamic contact calculation.

Experimental Study on Operation Performance of Two-Body Wave Energy Generator

The two-body oscillating type wave energy converter (WEC) is a hot research topic at present. A two-body device with damping disc was taken as the test model in this paper. The two bodies were connected by a hydraulic piston cylinder to realize the relative motion energy conversion. Physical experiments were carried out in a wave-making flume to study the operation performance. The effects of wave elements and load on the hydrodynamic characteristics and capture width ratio (CWR) of the model were analysed respectively. The results showed that wave frequency and external load were the main factors affecting the motion response and energy conversion of the device. With the increase of wave frequency and external load, the response amplitude operator (RAO) and the capture width ratio both increase first and then decrease. Wave height has little effect on system characteristics. There exists a best-matching wave period condition, and the optimal motion response and energy conversion are obtained.

Effect of stir casting parameters and mono/hybrid reinforcements on aluminium metal matrix composite–A review

Aluminum metal matrix composites are a new class of materials that have gathered more attention from many materialists. Especially, the automotive components like a piston, cylinder block, brake drum, etc., fabricated by different reinforcement, which has exposed better performance over conventional engineering materials. Aluminum composites are generally fabricated by stir casting technique due to simplicity in operation and adaptive to mass or job order production. The paper provides a background for the readers interested in the production of metal matrix composites through stir casting. Based on the literature assessment, the special attentions taken by the researchers to enhance the uniform distribution of particle to avoid agglomeration are discussed. The composite performances mainly depend on the aluminum matrix, particle size, the quantity of reinforcement, preheating temperature of reinforcement, and processing parameters such as stirring speed, stirring time, and wetting agents. The selection of two reinforcements and their suitable parameters for wetting are attaining interest by many researchers and maybe opted as future scope.

A Novel Positive Displacement Axial Piston Machine With Bent Cylinder Sleeves

In this paper, an investigation of a novel positive displacement axial piston machine using a bent cylinder sleeve configuration is presented. The proposed design eliminates the side moments on the piston/cylinder interface, therefore, reduces the frictional loss and improves the total energy efficiency. A multi-physics elastohydrodynamic lubrication model was used to aid the design of the piston/cylinder and the cylinder block/port block interface. Then, a lumped parameter model was used to optimize the port block geometry. Groove geometry was chosen primarily to reduce flow ripple, tilting moment, and cavitation risk. To improve the housing stiffness, the lumped parameter model was combined with a finite element analysis. This ensured safety for the testing. In the end, steady-state experiments were performed on the prototype based on the ISO4409 normative. The unit’s speed was set to 500 rpm, then increased by 500 rpm until it reached 3000 rpm. The supply pressure was set to 20 bar. The outlet pressure was set to 70 bar at first, then increased by 50 bar until it reached 220 bar. The results show a remarkable volumetric efficiency with a peak of 99.5%. It is however noted that due to some of the issues with the initial iteration of the current design, there is a reduction in mechanical efficiency. The causes and possible future solutions to these issues are discussed in the manuscript.

Performance study on the C.I engine using LHR and LTC in combination with biodiesel blends

Currently, the research of a single-cylinder 4-stroke direct injection diesel engine, which was naturally aspired, was used, and two modification methods were used. The first is the low-heat rejection method (LHR), and the second is the low-temperature combustion method (LTC). LHR was introduced into the engine by ceramic coating with alumina, which is applied to engine components such as the piston, cylinder lining, and valves and has a thickness of 300 microns without affecting the dimensions of the engine parts. In the next method, low - temperature combustion (LTC) method is done with EGR technique. And the exhaust gas recirculation setting (EGR) is included in the same setup as that of first method. Since, 15% of an exhaust gas is used in the EGR process. The diesel is blended with 20% of mahua biodiesel and 5% of ethanol as a fuel. After that, the engine performance is tested with conventional fuel when compared with biodiesel as a combined LHR and LTC methods. Finally, the engine output is increased by up to 3.48% as a result of the combination of LHR and LTC. As a result, emission levels could be dramatically decreased, and other results obtained could include a decrease in infrared radiation, resulting in a decrease in specific fuel consumption (SFC), and a substantial improvement in engine efficiency characteristics.

A New Approach for Modeling Mixed Lubricated Piston-Cylinder Pairs of Variable Lengths in Swash-Plate Axial Piston Pumps

The swash-plate axial piston pump is one of the most widely used pumps due to its simplicity and compactness in structure. In such a pump, the piston-cylinder system plays a crucial role, with its lubrication characteristics greatly affecting the overall pumping performance. A new numerical approach is proposed in this study for modeling mixed lubricated piston-cylinder interfaces of variable lengths in swash-plate axial piston pumps in the framework of multibody dynamics. The approach couples the hydrodynamic mixed lubrication model of the piston-cylinder interface with the multibody dynamics model of the piston pump. The lubrication model is established with a transient average Reynolds equation considering asperity contacts and is solved with the finite element method to derive the hydrodynamic forces of the lubricated pair, while the multibody dynamics model is established with Lagrangian formalism by considering hydrodynamic forces as external forces. Results for piston-cylinder interfaces of variable lengths in swash-plate axial piston pumps are presented, and the impacts of cylinder length and the tilt angle of the swash plate on the tribological performances of the interface are discussed. The results indicate that increasing the cylinder length can improve the stability and wear resistance of the piston, but it can exacerbate the frictional power loss. Moreover, although enlarging the tilt angle of the swash plate can effectively increase pump displacement, it can easily lead to serious friction, wear, and leakage problems. Consequently, the tilt angle of the swash plate should be carefully selected in practical applications.

A Novel Approach of Studying the Fluid–Structure–Thermal Interaction of the Piston–Cylinder Interface of Axial Piston Pumps

The friction in the swash plate type axial piston pumps is mainly influenced by the fluid film in the friction interface. The piston–cylinder interface is one of the key friction interfaces in the pumps. The film geometry is determined by the gap between the piston and the cylinder. The dimensions of the parts determine the gap geometry, and the deformation of the structure also influences the gap geometry. The fluid viscosity is strongly influenced by temperature. Thus, a novel approach of studying the fluid film, the structure, and temperature interaction is provided in this paper. A full and quick fluid–structure–thermal interaction simulation is realized. Then, a dynamic model of the piston–cylinder interface, which integrated the fluid–structure–thermal interacting effects, has been developed. Finally, an approach for calculating the extra friction force between the piston and the cylinder is provided. Compared with the measurement data, the simulation results of the axial friction force achieve a good fit. The present work allows a fast prediction and detailed support for designing the piston–cylinder interfaces.

The model for cylinder charge parameters during engine starting

The process of cylinder charge – air sucked into the cylinder – transformation during engine start-up phase is characterized. Heat exchange and air flow through piston-cylinder group leakage processes are described as factors influencing the gas thermodynamic parameters. The Woschni formula based on similarity theory was finally used as equation describing heat transfer in combustion engines cylinder. The computational model for cylinder charge parameters in the whole engine cycle during its starting at low temperature is presented. Some taken assumptions and characteristics of partial processes resulting from the computations are shown. There are indicated the possibilities of using the model at internal combustion engine diagnostic process.