Piston End Research Articles

Full-time domain analysis on operating characteristics of free piston Stirling generator

Free piston Stirling generator (FPSG) has been focused increasingly as energy conversion device for space nuclear power plants due to its long life and maintenance-free characteristics. For the purpose of predicting the operating characteristics and describing the inherent mechanisms of FPSG, experiments have been conducted based on a 1 kW prototype. Pressure fluctuations, pistons’ displacements, phase angle between displacer and power piston, hot and cold end temperatures, etc. were obtained during the experiments. Moreover, a full-time domain numerical model was proposed based on the physical processes experienced by all components within the generator. The comparisons between numerical results and experimental results showed that the relative errors are within 13.1% for the pistons’ amplitudes, 11.7% for the terminal voltage and 3.6% for the operating frequency. The thermodynamic, kinetic and electrical characteristics of the prototype were further analyzed. Some imperceptible phenomena were revealed, including the transient characteristics of heat absorption and rejection, hysteresis loss on the displacer rod and leakage loss at the balancing orifices. A detailed energy distribution scheme was plotted and it can provide guidance for the design and manufacture of subsequent generators of the same type.

Gas chromatograph calibration of gas mixtures using a versatile precision volumetric apparatus

A compact, volumetric apparatus was developed for accurate automated preparation of standard gas and gas-liquid mixtures for gas chromatograph detector calibration, with accuracies comparable to those from gravimetric or Coriolis flow methods. The method developed by the principal author is not an adaptation or extension of any other apparatus or technology, and measurements involve only stepper motor steps, temperature, and pressure ratios. Mixture preparation is accomplished via the displacement of gas between chambers in a highly uniform cylinder, separated by a movable piston. Piston movement, with piston end rods of exactly equal diameter, ensures that there is no change in interior volume, and the volume of gas displaced from the bottom into the top compartment is exactly proportional to the piston travel measured to within 10μm. The apparatus, operation, and previously unpublished measurements on common refinery gas mixtures over large concentration ranges are described in detail. These confirmed the accuracy and versatility of the apparatus and also the principle of no pressure change during mixture preparation, from sensitive pressure measurements. Conservative expanded uncertainties in prepared mixture mole fraction ranged from 0.001 to 0.002 over extended composition ranges. Absolute average deviations for the detector response factor for the mixtures ranged from 0.001 to 0.002. An exact new mathematical solution procedure permits the use of impure "pure" gases without loss of accuracy and can be applied to other procedures for standard gas mixture preparation. An exact expression is listed for determining "pure" gas purity.

Modeling and Statistical Analysis of Piston End of Connecting Rod, Using Ansys Software

Modeling and Statistical Analysis of Piston End of Connecting Rod, Using Ansys Software

Motion characteristics of a novel elastic rotating micro-electromechanical power system

This article reports a conceptual study of a new micro-electromechanical power system using elastic leaf piston rotating engine rather than conventional engines as the main component. The proposed innovative elastic rotating micro-electromechanical power system adopts two leaf pistons to substitute the traditional rigid piston for establishing elastic combustors and operates with a novel Humphrey thermodynamic cycle, which brings about high power density and energy conversion efficiency. The motion model of leaf piston is carried out by using the Euler–Bernoulli theory, and a novel calculation method of trial and error is presented to iteratively simulate the motion of elastic piston. The effects of the piston length and installation position on the combustor variation are also investigated. Results indicate that the contact point of piston and cylinder is not the piston end and keeps moving, and the combustor is periodically compressed and expanded by the rotor and piston motion to perform the intake, compression, expansion, and exhaust. Besides, the minimum combustor volume lasts an amount of time, which provides a possible realization of full isovolumetric combustion. A larger installation phase angle of pistons means a longer compression and expansion, larger combustor volume and shorter constant-volume duration.

Damping performance analysis of magnetorheological damper with serial-type flow channels

In order to obtain a larger damping force with the limited axial size of the vehicle suspension system, a new magnetorheological damper with serial-type flow channels was developed. The piston head was equipped with two piston end covers, three piston non-magnetic sleeves, and four piston magnetic sleeves, which were sequentially combined into three serial-type flow channels to form three groups of effective damping gaps. The structure and principle of the proposed magnetorheological damper were described in detail, and the model for calculating damping force was deduced too. Simulation and analysis for the proposed magnetorheological damper was implemented using electromagnetic field simulation software. The damping performance was tested and analyzed on the test rig under different applied current, amplitude, and frequency excitation. The experimental results show that the damping force is 6838 N under the load excitation with frequency of 1 Hz, amplitude of 7.5 mm, and current of 1.5 A, which is 1.6 times than the expected damping force. The equivalent damping coefficient is attained to 290 kN/s m−1, which shows that the developed magnetorheological damper has high vibration control ability and good mechanical properties.

Design of Swashplate Axial Piston Machines Having Low Piston Transverse Forces

Axial piston machine of swashplate type is the common design widely used for many hydraulic applications because of its simplicity, compact design and low cost. However, this simplicity has a negative effect for piston transverse forces which limits machine performance. The main target of this study is to investigate a feasible design of a fixed displacement swashplate contour in order to minimize piston transverse forces. The design should compensate the contact surface mechanism between swasplate and piston end. Piston slipper is replaced by a ball that is rotatably mounted within a ball socket formed at the piston end. The ball runs on a circumferential contour groove formed on the swashplate surface. The sliding friction between swashplate and slipper is replaced by a rolling friction between ball and circumferential runway groove. Primary results show a rough estimation of 30% reduction of piston transverse forces due to the cam action radial forces elimination. This reduction promises to enhance overall machine performance.

Computer Aided Design of Axial Piston Machines Having a Roller Piston Bearing

Swashplate axial piston machines are simple, compact and low price. This simplicity is at the expense of piston transverse forces which limits machine characteristics. The aim of this study is to propose more effective developed design using roller piston bearing. Ball bearing was proposed to reduce transverse forces acting on the piston end of the axial piston machines. The proposed roller bearing design will provide line contact bearing between roller and cam contour compared to point contact of ball bearing arrangement. The roller runs on a flat surface contour formed on the swashplate which is simpler in manufacturing process. The sliding friction between swashplate and slipper is replaced by a rolling friction between roller and runway of cam surface contour. Results show the feasibility of the developed design. The proposed design promises to increase the pressure limitation of the ball bearing arrangement. Parameters such as piston displacement, cam action angle are the same for both roller and ball piston bearing. A comparison analysis was also performed between two alternative cam contours, sinusoidal and linear piston displacement. The selection criterion was based on piston transverse torque. Results show that sinusoidal piston displacement is much better choice than the linear one.

Optimal design of Magneto-Rheological damper comparing different configurations by finite element analysis

Magnetorheological (MR) damper is one of the most advanced applications of semi active damper in controlling vibration. Due to its continuous controllability in both on and off state its practice is increasing day by day in the vehicle suspension system. MR damper’s damping force can be controlled by changing the viscosity of its internal magnetorheological fluids (MRF). But still there are some problems with this damper such as MR fluid’s sedimentation, optimal design configuration considering all components of the damper. In this paper both 2-D Axisymmetric and 3-D model of MR Damper is built and finite element analysis is done for design optimization. Different configurations of MR damper piston, MR fluid gap, air gap and Dampers housing are simulated for comparing the Dampers performance variation. From the analytical results it is observed that among different configurations single coil MR damper with linear plastic air gap, top and bottom chamfered piston end and medium MR fluid gap shows better performance than other configurations by maintaining the same input current and piston velocity. Further an experimental analysis is performed by using RD-8041-1 MR Damper. These results are compared with the optimized MR Damper’s simulation results, which are clearly validating the simulated results.

Modeling and Analysis of Two Wheeler Connecting Rod by Using Ansys

Connecting rod is a major link inside of a internal combustion engine. It is the intermediate member between the piston and the crankshaft. Its primary function is to transmit the push and pull from the piston pin to the crank pin thus converting the reciprocating motion of piston in to rotary motion of the crank. In this paper a static analysis is conducted on a connecting rod of a single cylinder 4-stroke petrol engine. The model is developed using Solid modeling software i.e. PRO/E (creo-parametric). Further finite element analysis is done to determine the von-misses stresses shear stress and strains for the given loading conditions. Keywords - ANSYS Workbench, connecting rod, Finite Element analysis, PRO/E (creo-parametric). I. Introduction Connecting rod is among large volume production component in the internal combustion engine. It connects the piston to the crankshaft and is responsible for transferring power from the piston to the crankshaft and sending it in to transmission. They are different types of materials and production methods used in the creation of connecting rods. The major stresses induced in the connecting rod are a combination of axial and bending stresses in operation. The axial stresses are produced due to cylinder gas pressure (compressive only) and the inertia force arising in account of reciprocating action (both tensile as well as compressive), where as bending stresses are caused due to the centrifugal effects. It consists of a long shank, a small end and a big end. The cross-section of the shank may be rectangular, circular, tubular, I-section or H-section. Generally circular section is used for low speed engines while I-section is preferred for high speed engines. The most common type of manufacturing processes is casting, forging, and powdered metallurgy. Connecting rod is subjected to a complex state of loading. It undergoes high cyclic loads of the order of 10^8 to 10^9 cycles, which range from high compressive loads due to combustion, to high tensile loads due to inertia. Therefore, durability of this component is critical importance. Due to these factors, the connecting rod has been the topic of research for different aspects such as production technology, materials, performance, simulation, fatigue etc. Vivek.c.pathade et al(1) performed stress analysis of I.C Engine connecting rod by finite element method. They modeled connecting rod using pro/E Wildfire 4.0 and ANSYS Workbench 11.0 software. They reported from the theoretical and finite element analysis then the stresses induced in the small end of the connecting rod are greater than the stress induced at the big end. K.surdershn Kumar et al (2), reported on modeling and analysis of two wheeler connecting rod. In this connecting rod is replaced by aluminum reinforced with boron carbide for Suzuki GS150R motor bike. A parametric model of connecting rod is modeled using pro/E Wildfire 4.0. Analysis is carried out by using ANSYS software. They presented the results of materials and reported that the working factor of safety is nearer to theoretical factor of safety in aluminum boron carbide. Anil Kumar et al (3), presented the optimization of connecting rod parameters using CAE tools. They reported on optimizing weight and reducing inertia forces on the existing connecting rod, which is obtained by changing design variables in the existing connecting rod design. The model was developed in pro/E Wildfire 5.0 and then imported as a Para solid (xt) from in ANSYS Workbench. The stress was found maximum at the piston end. This can be reduced by increasing the material near the piston end. The weight of the connecting rod was also reduced by 0.004kg which was not significant but reduces the inertia forces. Suraj pal et al (4), reported on design evaluation and optimization of connecting rod parameters using Finite element method. Proper finite element model is developed using pro/E Wildfire 4.0. The weight of the connecting rod is also reduced by 0.477g. The stress is found maximum at the piston end so that material is increased in the stressed portion to reduce stress. Dr. S B Jaju et al (5), performed modeling and analysis of connecting rod of four stoke single cylinder engine for optimization of cost and material. Their study has dealt with two subjects first static load stress analysis of the connecting rod, and then second optimization for weight.

Numerical Simulation of Noise Radiation from Semi-Hermetic Reciprocating Food Refrigeration Compressors

The semi-hermetic reciprocating compressor is the dominant noise source of food refrigeration unit. Excessive noise and vibration have a negative impact on both people's health and work efficiency；moreover, it causes fatigue damage to machinery thus reducing its working life. In this paper, numerical simulation of noise radiation from semi-hermetic reciprocating food refrigeration was carried out by successful combination of Pro/E, Hypermesh, Nastran and Virtual Lab Acoustics software. The simulation results show that the low-frequency noise radiation near the end of the piston-cylinder is directional and stronger than that of the other side, which offers a valuable reference for noise reduction. In addition, the sound pressure dB curve of any field point can be obtained through the numerical simulation, and it clearly shows that sound pressure values away from the piston end are significantly lower than those at the piston side; and noise radiation energy of compressor concentrates at 500Hz and 1000Hz. This paper provides an effective research method for the semi-hermetic reciprocating compressor’s noise reduction

Investigations on Actuator Dynamics through Theoretical and Finite Element Approach

This paper gives a new approach for modeling the fluid-structure interaction of servovalve component-actuator. The analyzed valve is a precision flow control valve-jet pipe electrohydraulic servovalve. The positioning of an actuator depends upon the flow rate from control ports, in turn depends on the spool position. Theoretical investigation is made for No-load condition and Load condition for an actuator. These are used in finite element modeling of an actuator. The fluid-structure-interaction (FSI) is established between the piston and the fluid cavities at the piston end. The fluid cavities were modeled with special purpose hydrostatic fluid elements while the piston is modeled with brick elements. The finite element method is used to simulate the variation of cavity pressure, cavity volume, mass flow rate, and the actuator velocity. The finite element analysis is extended to study the system's linearized response to harmonic excitation using direct solution steady-state dynamics. It was observed from the analysis that the natural frequency of the actuator depends upon the position of the piston in the cylinder. This is a close match with theoretical and simulation results. The effect of bulk modulus is also presented in the paper.

The stability analysis of a slider-crank mechanism due to the existence of two-component parametric resonance

The objective of this paper is an analytical and numerical study of the dynamics and dynamic instability of a slider-crank mechanism with an inextensible elastic coupler. Special attention is given to the phenomena arising due to modal interactions produced by the existence of multi-component, specifically two-component, parametric resonance. Such modal couplings are very common in the bending-bending motions of fixed/ rotating beams. The two-component parametric resonance occurs when one of the natural frequencies of flexible parts of the mechanism is one-half or twice of the excitation frequency and simultaneously the sums or the differences among the internal frequencies are the same, or neighboring, as the frequency of excitation. The effects of two-component parametric resonance post on instability condition are also investigated. Resonance generated by more than two component modes are neglected due to its remote probability of occurrence in nature. The mechanics of the problem is Newtonian. Methods of analysis will consist of the dynamics of small deformations superimposed on the undeformed state. Without loss of generality and based on the Euler–Bernoulli beam theory, the coupled nonlinear equations of motion of a slider-crank mechanism with an inextensible flexible linkage are derived. The Newtons second law is used to obtain the boundary constraints at the piston end. Galerkins procedure was used to remove the dependence of spatial coordinates in the partial differential equations. The method of multiple time scales is applied to consider the steady state solutions and the occurrence of dynamic instability of the resulting multidegree-of-freedom dynamical system with time-periodic coefficients.

Flame-Spreading and Combustion in Packed Beds of Propellant Grains

This paper is concerned with the prediction of the pressure history during the process of flame-spreading and combustion of solid-propellant grains as would occur, for example in a gun cartridge. Solution of the governing conservation equations for the two-phase media requires the use of empirical relations to account for the physical processes of momentum and energy interaction between the solid grains and hot propellant gas. The results indicate the extreme importance of these interaction relations on the predictions of the pressure and velocity field. and at the other is a projectile which will begin to move at a given prescribed pressure. This 'piston then moves through a long length of channel of the same cross section as the cham- ber, in order that the flow processes following piston motion can be followed. A predescribed igniter mass flow provides gaseous products which, in turn, ignite the bed. Since solid propellants have high burning rates, the rate of gas generation within the chamber is high. Therefore, the pressure is rising rapidly during this flame-spreading process. The pressure rises enhances the pressure-dependent burning rate of the propellant, the result of which is a rapidly accelerating combustion process, with generally steep gradients along the length of the chamber. This gradient results in a high-velocity flow of the gases toward the piston end and into the unburned portion of the propellant. Hence, the flame-spreading and pressurization is rapid, and the entire burn is completed in a matter of milliseconds, if the ignition source is strong enough. Looking at flow process taking place, one may determine the effect on the particle bed. The hot igniter gases initially are driven into a quiescent bed of propellant particles. These ignite the particles nearest the igniter source. The mass generation and subsequent pressurization occur, and a flowfield develops within the chamber. The propellant par- ticles exert a drag force on the flowing gases and are ac- celerated. As shot-start pressure is approached, the entire bed usually has been set into motion.J Throughout the burn, the particles continue to decrease in size as they burn. Kuo and Summerfield2 have pioneered the analysis of packed-bed solid-propellant combustion.