On the efficiency of the axial piston motor considering piston form deviations
TL;DR: In this article, the effect of machining imperfections like out-of-roundness and taper in the piston on the mechanical and volumetric efficiency of the motor, in the speed range where the viscous friction is dominant, is studied.
Abstract: Axial piston motors rely on a close fit of piston to bore to minimise leakage past the piston due to axial pressure drop. Machining imperfections in the cylinder bore and the piston change the clearance between them, affecting the performance of the motor. The effect of machining imperfections like out-of-roundness and taper in the piston on the mechanical and volumetric efficiency of the motor, in the speed range where the viscous friction is dominant, are studied. Experiments to measure torque and leakage flow are conducted on a fixed displacement swash plate type axial piston hydraulic motor and results are presented.
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Patent•
30 Oct 2001
TL;DR: A homogenous charge compression ignition barrel engine as mentioned in this paper includes an engine housing with a first and second end, where an elongated power shaft is longitudinally disposed between the first end of the housing and the open ends of the cylinders such that a portion of the track is disposed generally in alignment with the central axis of each cylinder.
Abstract: A homogenous charge compression ignition barrel engine includes an engine housing with a first and second end. An elongated power shaft is longitudinally disposed in the engine housing and defines a longitudinal axis of the engine. A plurality of cylinders surround the longitudinal axis with each cylinder having a closed end and an open end. Each cylinder has a central axis. The open ends of the cylinders are each generally directed toward the first end of the housing. An intake system is operable to introduce a combustible mixture of air and fuel into each of the cylinders. A track is disposed between the first end of the housing and the open ends of the cylinders such that a portion of the track is disposed generally in alignment with the central axis of each of the cylinders. The track has a cam surface that longitudinally undulates with respect to the open ends of the cylinders. A portion of the cam surface is disposed generally in alignment with the central axis of each of the cylinders. The track and the cylinders are rotatable with respect to each other such that the undulating cam surface moves with respect to the open ends of the cylinders. A piston is moveably disposed in each of the cylinders such that a combustion chamber is defined between the piston and the closed end of the cylinder. Each piston is in mechanical communication with the cam surface of the track such that as the cylinders and the track move with respect to each other, the pistons reciprocate within the cylinders. Each cylinder is operable to compress a combustible mixture until the mixture auto ignites, without the introduction of a spark.
82 citations
01 Jan 2002
TL;DR: In this article, the authors introduced a new method for complex gap flow simulation of connected and self-adjusting gaps of axial piston machines, where the model for the piston/cylinder pair was extended to consider elastohydrodynamic effects.
Abstract: The design of individual lubricating gaps with their bearing and sealing function mainly determines the loss behaviour, life time, reliability and achievable technical parameters of displacement machines. The gap flow conditions are influenced by the operating parameters, the gap macro geometry, the surface quality and by the chosen surface material. Therefore the determination of the time dependent gap height requires very complex simulation models considering the motion of moveable parts, the interaction between machine parts, the dependency on design and operating parameters and the energy dissipation within the gaps as well as changes of the gap height caused by the flexibility of the applied surface material. This paper introduces a new method for complex gap flow simulation of connected and self-adjusting gaps of axial piston machines, where the model for the piston/cylinder pair was extended to consider elastohydrodynamic effects. The simulation model has been verified with the help of friction force measurements on the piston/cylinder assembly.
29 citations
Patent•
30 Apr 2003
TL;DR: An internal combustion barrel engine includes an engine housing with a first and second end as mentioned in this paper, and an elongated power shaft is longitudinally disposed in the engine housing and defines a longitudinal axis.
Abstract: An internal combustion barrel engine includes an engine housing with a first and second end An elongated power shaft is longitudinally disposed in the engine housing and defines a longitudinal axis A combustion cylinder and a guide cylinder are spaced apart and disposed on a common cylinder axis that is generally parallel to the central axis The cylinders each have an inner end and an outer end, with the inner ends being closer to each other The outer end of the combustion cylinder is closed An intake system is operable to introduce a mixture of air and/or fuel into the combustion cylinder A track is supported between the inner ends of the cylinders and has an undulating cam surface The track is moveable such that the portion of the cam surface most directly between the cylinders undulates toward and away from the inner end of the combustion cylinder A double-ended piston includes a combustion end disposed in the combustion cylinder so as to define a combustion chamber between the combustion end and the closed end of the combustion cylinder A guide end is disposed in the guide cylinder A midportion extends between the combustion end and the guide end and is in mechanical communication with the guide surface of the track A variable compression ratio device is operable to move the track axially towards and away from the inner end of the combustion cylinder so as to adjust the compression ratio Combustion occurs only in the combustion cylinder and does not occur in the guide cylinder
27 citations
TL;DR: In this paper, an integrated torque model for a swash-plate-type seawater hydraulic axial piston motor with symmetrical precompression angles has been developed, which consists of a torque submodel and a dynamic pressure sub-model.
Abstract: Seawater hydraulic axial piston motor is an important and elemental component in underwater tool system. The torque characteristics for a swash-plate-type seawater hydraulic axial piston motor is investigated, and an integrated torque model for the motor with symmetrical pre-compression angles has been developed, which consists of a torque sub-model and a dynamic pressure sub-model. Numerical simulations have been carried out to examine the effects of (a) pre-compression angle, (b) relief-groove obliquity, (c) motor speed, (d) piston chamber dead volume, (e) friction on the dynamic pressure and the output torque characteristics. The results indicate that the pre-compression angle, the friction coefficient, and the clearance between cylinder bore/piston have significant impact on the torque characteristics. The test verification has been undertaken with a five piston water hydraulic motor. This research contributes to the mechanism of output-torque fluctuation in a swash-plate-type seawater hydraulic axial piston motor, as well as the investigation of the torque transition phenomenon owing to the pre-compression angle. The research has laid the foundation for the development and improvement of the seawater hydraulic axial piston motor in underwater tool system.
23 citations
TL;DR: In this article, the deformation of the piston guide and rear/front sliding bearings in the deep-sea environment was analyzed by ANSYS Workbench, in which the change of fit clearances have a great effect on the working performance of the SHAPM.
Abstract: Seawater hydraulic axial piston motor (SHAPM) is an elemental component in underwater tool system. The pressure flow model and torque model of the SHAPM was derived and the deformation of the piston guide and rear/front sliding bearings in the deep-sea environment was analyzed by ANSYS Workbench, in which the change of fit clearances have a great effect on the working performance of the SHAPM. Therefore, the simulations on the deformation of the piston guide and rear/front sliding bearings in different seawater depths were achieved and different fit clearances with varying depths were obtained. The results indicated that the clearances on the piston/cylinder bore pair and rear/front sliding bearings decreased with the increase of sea depth and the effective sea depth suiting for normal work was got. Meanwhile, the torque efficiency of the SHAPM in deep sea environment is lower. The results revealed that with the increase of the sea depth, the clearances of the piston/cylinder bore pair and rear/front sliding bearings decreased correspondingly. Meanwhile, the torque efficiency of the SHAPM decreased to a certain extent. Last, the suitable sea depth range for the normal working of the SHAPM was obtained.
21 citations
References
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TL;DR: In this article, an attempt is made to analyse systematically the three types of profiles commonly considered for high speed actuators, using Reynolds' differential equation, and analyses are made using an analytical method for one-dimensional flow and using the finite element method for twodimensional flow.
Abstract: In a high speed hydraulic actuator the usage of seals on the piston surface causes excessive wear on the seals and positional inaccuracies owing to coulomb friction. Hence sealless pistons with sloping surfaces have been tried by some manufacturers of such actuators. Here an attempt is made to analyse systematically the three types of profiles commonly considered for high speed actuators, using Reynolds' differential equation. Analyses are made using an analytical method for one-dimensional flow and using the finite element method for two-dimensional flow. The analyses reveal that single tapered pistons have certain limitations and that double tapered pistons can function successfully under different conditions in hydraulic actuators. It is also shown that friction in these types of pistons is much less than in conventional pistons with seals.
17 citations
TL;DR: In this paper, a new test-rig has been developed to test the actuators, and the test results confirm the main findings of the theoretical study on three types of tapered pistons.
Abstract: Use of seals on the piston surface of servo hydraulic actuators causes, apart from excessive wear, positional inaccuracies arising out of large mechanical friction due to physical contact In order to improve their performance, modern servo hydraulic actuators use pistons with tapered surfaces When such pistons move within the cylinder there is a chance of generating sufficient oil pressure to lift the piston owing to hydrodynamic action Theoretical study on three types of such pistons was reported earlier In this paper, experimental work carried out on those tapered pistons is presented A new test-rig has been developed to test the actuators, and the test results confirm the main findings of the theoretical study
15 citations
15 Dec 1990-JSME international journal. Series 3, Vibration, control engineering, engineering for industry
TL;DR: In this article, the equations of motion of a conventional piston in axial piston pumps and motors with metallic contacts are derived for swash plate types, the fluid film shape between the piston and the cylinder wall, contact forces and loss of power are numerically obtained in relation to both the operating conditions and piston dimensions.
Abstract: The equations of motion of a conventional piston in axial piston pumps and motors with metallic contacts are derived. For swash plate types, the fluid film shape between the piston and the cylinder wall, contact forces and loss of power are numerically obtained in relation to both the operating conditions and piston dimensions. The length of the sealing part composed of the piston and cylinder wall is, in particular, shown to considerably affect the loss of power. Finally, the validity of the analysis is discussed by comparison with the results of a performance test of a pump for high water content fluids.
11 citations
TL;DR: In this article, the authors analyzed the process of grinding above and below the centres and showed that the roundness error increases only by a few microns when ground below the centers and the change in the surface finish is insignificant.
Abstract: Centreless grinding is carried out with workpiece centre above the line joining the centres ofgrinding and control wheels. When a workpiece has a slight bend or a projection on the surface, it is safer to grind below the centres. This paper analyses the process of grinding above and below the centres. The results show that the roundness error increases only by a few microns when ground below the centres and the change in the surface finish is insignificant.
9 citations
01 Jan 1981
3 citations