Piston Skirt Profile Research Articles

Stress and fatigue analysis of engine pistons using thermo-mechanical model

This paper presents a thermo-mechanical finite element analysis model for the stress and fatigue analyses of engine pistons. The model consists of the piston, piston pin, piston ring, bushing, cylinder liner and connecting rod. The oil film and contact pressure are considered in the contact surfaces between the piston and piston pin, the piston pin and bush, and the piston skirt and cylinder liner. A self-compiled code, which considers the factors of the piston skirt profile and ellipticity, is applied to calculate the initial clearance at the oil film surfaces between the piston and piston pin, the piston pin and bush, and the piston skirt and cylinder liner. The dynamic loads of the piston and connecting rod under the peak torque and peak power cases are calculated using powertrain commercial software, which are then used to carry out the stress and fatigue analyses. Compared with those published in literature, the present model is able to simulate the actual working conditions of the piston more accurately. The model can be used to evaluate and assess the piston skirt pressure, the stress and fatigue life of the concerned areas of the piston.

Piston dynamics analysis considering skirt-liner dynamic clearance

Piston slap force is one of the main sources of mechanical engine noise. To obtain a more accurate determination of the piston slap force and minimize piston slap noise, a new simulation model that considers dynamic clearance of the piston skirt and liner has been established in this study. The skirt-liner dynamic clearance is caused mainly by the elastic deformation and thermal deformation of the piston. Comparing three different models, it was found that the impact of dynamic clearance on the piston slap force is reflected mainly in the medium-high frequency, which is the sensitive frequency of the slap noise. Therefore, it is necessary to consider dynamic clearance in the simulation model. In addition, the mechanisms behind the dynamic clearance effect on fluid lubrication, piston dynamics, and piston slap noise were observed. In particular, three typical structural parameters in piston dynamics (the piston pin offset, piston-liner clearance, and piston skirt profile) were studied. The analyses provide guidance for the design of low-noise engines.

Study on the effect of piston skirt profile on the vibration behavior of non-road high pressure common rail diesel engine

The piston secondary motion is the most predominant excitation source for the mechanical vibration of diesel engine, which is directly affected by the piston profile. The effects of piston skirt profile on the dynamic behavior of piston and the vibration characteristics of engine block is studied synthetically by the method of a combination of experimental test and numerical simulation. The temperature distribution of the piston top surface under rated working condition is tested by a hardness plug, which is used as the boundary condition to carry out the thermodynamic simulation of diesel engine working process, to obtain the hot profile of the piston. Then, the dynamics model of piston assemblies are formally established, and the skirt profiles of different bump positions of the piston skirt are optimally designed. Based on the above analysis, a comprehensive study on the influence of bump position on the piston dynamic behavior is carried out. Then, applying the modal testing method for the engine block and crankshaft to establish the elastic multi-body dynamics model of diesel engine and load the piston slapping force at different bump positions, the vibration response of the surface structure under the action of different piston slapping forces is also studied. The results show that the mechanical vibration of engine block will become more severe with the hiking up of bump position at the piston skirt. Also, the vibration behavior of the engine block in the middle and high frequency section is very sensitive to the bump position of the piston skirt, especially in the frequency range of 1600 Hz–3150 Hz. In addition, vibration noise performance can be significantly improved by adjusting the bump position of piston skirt downwards. Particularly, the vibration noise performance can be best achieved when the bump position of piston skirt is 5 mm.

The Analysis of Secondary Motion and Lubrication Performance of Piston considering the Piston Skirt Profile

The work performance of piston‐cylinder liner system is affected by the lubrication condition and the secondary motion of the piston. Therefore, more and more attention has been paid to the secondary motion and lubrication of the piston. In this paper, the Jakobson‐Floberg‐Olsson (JFO) boundary condition is employed to describe the rupture and reformation of oil film. The average Reynolds equation of skirt lubrication is solved by the finite difference method (FDM). The secondary motion of piston‐connecting rod system is modeled; the trajectory of the piston is calculated by the Runge‐Kutta method. By considering the inertia of the connecting rod, the influence of the longitudinal and horizontal profiles of piston skirt, the offset of the piston pin, and the thermal deformation on the secondary motion and lubrication performance is investigated. The parabolic longitudinal profile, the smaller top radial reduction and ellipticities of the middle‐convex piston, and the bigger bottom radial reduction and ellipticities can effectively reduce the secondary displacement and velocity, the skirt thrust, friction, and the friction power loss. The results show that the connecting rod inertia, piston skirt profile, and thermal deformation have important influence on secondary motion and lubrication performance of the piston.

Effect of Piston Skirt Profile Parameter on Secondary Motion and Lubrication Performance of Piston

Effect of Piston Skirt Profile Parameter on Secondary Motion and Lubrication Performance of Piston

Results of modeling the secondary kinematics of the piston in the cylinder of a high-speed diesel engine

The relevance of the investigation of the processes of secondary kinematics of the piston in the internal combustion engine’s cylinder is due to their strong influence on such indicators as mechanical losses, wear, noise, vibration, oil consumption, and their insufficient knowledge concerning high-speed piston engines. The purpose of the research was an assessment of the influence on the character of the secondary kinematics of the piston of the high-speed internal combustion engine design factors, operating conditions and lubricant and on this basis finding the ways to improve the lubrication and friction conditions in coupling of the «cylinder-piston skirt». The tasks to be performed to achieve the research goal were in an identification the most significant parameters of the construction on the piston's secondary kinematics, mode of operation and properties of the lubricant; obtaining diagrams of the piston's secondary kinematics depending on the change in the values of the influencing factors, as well as the analysis of the obtained results and the development of recommendations aimed at reducing friction and wear in the piston-cylinder-unit. For the subject of the research the piston of the high-speed diesel engine 1CH 8,5/8,0, having a barrel-shaped profile of the piston skirt in the serial production and a negative dezaksial of piston pin, was chosen. The research method is mathematical modeling using the calculation program PISTON-DHT. Discussion of the obtained results made it possible to reveal the two most influential parameters on the character of the secondary kinematics of the piston: the dezaksial of piston pin and piston skirt profile. The variation of the sign and the values of these indicators were established an expedience to switch from a negative one to the positive dezaxial and an application of rational profile of the piston skirt. For the two most dynamically loaded strokes of the working cycle «Compression» and «Expansion», the dominance of the piston movement in the position of the scraper relative to the adjacent side of the cylinder wall was highlighted. The generalized recommendations aimed at eliminating the dominance of this undesirable situation can be taken into account and used in the design and completion of high-speed internal combustion engines pistons in order to minimize mechanical losses and wear.

Dynamics and lubrication analyses of a planar multibody system with multiple lubricated joints

In order to ensure the mechanical systems a better performance, most of their joints are designed to operate with lubricant. The differently located lubricated joints interact with each other, influencing the total performances of the system. This study proposes a numerical approach for the multibody system modeling with the consideration of the interactions among the multiple lubricated joints to investigate the dynamics and tribological performances of the mechanism. This approach couples the lubrication model of both translational and revolute joints with the dynamics model of the multibody system, and is performed on a four-stroke gasoline engine with the lubricated piston skirt-liner subsystem and lubricated big-end bearing of the connecting rod. The multibody dynamics model is built with Lagrange’s method. The lubrication models are built based on the average Reynolds equation, and solved with finite element method to derive the hydrodynamic forces according to the motion of the system. The piston skirt profile, pin offset and the effects of surface roughness on the lubrication performances are taken into account. The simulation results reveal that there are obvious interactions between the differently located lubricated joints, and the larger clearance can pronounce the interactions.

Forced Diesel Piston Tribological Parameters Improvement

The paper solved the problem of optimizing the piston skirt profile in the hot state according to the criteria of minimal frictional losses. The authors defined and improved the geometrical parameters of the piston design considering the optimum profile of the skirt; developed recommendations for improving the design of the piston. For six-cylinder V-shaped forced diesel engine, with a cylinder diameter of 150mm and a piston stroke of 160mm (further diesel) a piston design with improved tribological parameters was developed.

The Effects of Piston Skirt Profiles on Secondary Motion and Friction

Piston skirt form deviating from a perfect cylinder is investigated numerically for an improved frictional performance. Three features defining the barrel and oval form of the skirt are compared in the search for lower friction power loss. Radius of curvature around the bulge of the barrel is changed to obtain a flatter or more-rounded lubricated area with respect to a hot-piston profile as well as the axial location of this bulge. On the other hand, the circumferential variation in the separation between the skirt and cylinder wall is represented by an elliptical piston and the aspect ratio is varied for comparison. These different skirt profiles are used in a developed piston secondary dynamics model solving for the lateral movement of the piston by calculating the hydrodynamic and boundary normal forces acting on the piston together with friction. Finally, an improved skirt profile is suggested to obtain better frictional efficiency.

Research of Internal Combustion Engine Piston Skirt Profile Line Effect Based on Dynamics and Tribological Coupling Model

This paper mainly based on the coupling relationship between tribological and dynamic behaviors of cylinder liner-piston system to establish dynamics and tribology coupling model of cylinder linerpiston-piston ring, and to analyze the effect of piston skirt profile based on it, providing theoretical basis for determining the effect of piston skirt profiles to piston dynamics and lubrication performance.

A study of the secondary piston motion arising from changes in the piston skirt profile using a simplified piston skirt model

An existing model of the interface between a parallel-sided piston skirt and the cylinder wall in an internal combustion engine is extended to allow the modelling of barrelling of the piston skirt. The effects of the skirt profile on the secondary motion of the piston and on the distribution of pressure in the lubricant film are examined. It is shown that piston secondary motion, and in particular rotation of the piston about the gudgeon pin, which might contribute to wear of the cylinder, can be reduced by appropriate positioning of the maximum diameter of the piston skirt in relation to the gudgeon pin and the centre of mass of the piston.

Middle-Convex Curve and Ellipse Surface of Piston Skirt Design Based on MATLAB and Pro/E

In this paper, the characteristics and design rules of piston skirt middle-convex ellipse surface are studied, and the piston skirt profile mathematical model was established. Piston skirt middle-convex curve is interpolated based on MATLAB, and the piston middle-convex surface was generated according to the theory of surface modeling; the piston skirt transversal section was controlled based on Pro/E curvilinear equation, and then the piston skirt surface was created. The example indicates that commonality and fitting precision of these two design methods are excellent, so it has the better application value of project.

Design of Mechanical and Combustion System for Small Non-Road Diesel Engine to Meet the EPA IV Emission Regulations

Based on 1.9L small non-road diesel engine, mechanical and combustion system were redesigned and optimized to improve the emission performance. The engine block structure such as ribs, bolt hole depth and water jacket were optimized to improve the strength and stiffness and reduce the block’s distortion. The type of piston ring, piston skirt profile and their fit clearances were also optimized, and plat-honing cylinder liner was used to reduce the oil consumption. In combustion system, fuel injection pump, injection nozzle, fuel spray distribution and fuel supply advance angle were modified, combustion chamber was changed to small platform dumbbell-shaped chamber, and the closed-loop exhaust gas recirculation (EGR) system controlled by negative pressure was applied to trade-off the emissions of NOX and PM. The test results show that the emission performance of optimum diesel engine could meet EPA IV emission regulations.

Development of analysis model for optimising piston skirt profile

In this paper an optimum profile of piston skirt is chosen. First, an oval?hyperboloid is employed to describe the piston skirt surface in running conditions. Second, the Reynolds Equation, which describes the lubrication of piston skirt, is solved with finite element modelling. To find an optimum profile for the piston skirt, the curvature and the peak coordinate of the oval?hyperboloid are changed. Once the optimum profile is found, the profile at room temperature is decided by considering the deformations and the size tolerances of piston and cylinder, and the clearance between piston and liner.

On the optimization of piston skirt profiles using a pseudo-adaptive response surface method

A method for the optimization of piston skirt profiles used in internal combustion engine piston design is proposed. The method is based on a response surface approximation of standard performance measures used in piston design, namely, the RMS values of the piston’s transverse and angular accelerations, used as indicators of piston slap and noise, and the friction work on the skirt. The method is intended to be used in conjunction with computationally-intensive piston simulation tools. As such, it can be used also as a paradigm for strategies to solve optimization problems that rely on computationally expensive simulation models. An example illustrates the capabilities of the method and the significant enhancements in performance that result from an optimized piston skirt profile.

Effects of Piston Design Parameters on Piston Secondary Motion and Skirt - Liner Friction

In this article, a previously developed and experimentally validated piston secondary motion model has been improved further numerically and applied to understand the detailed interactions between the piston skirt and the cylinder liner for various piston design parameters. The model considers the roughness of the surfaces and the topography of the skirt in both the axial (barrel profile) and circumferential (ovality) directions. Three modes of lubrication: hydro-dynamic, mixed, and boundary lubrication regimes have been considered and the skirt is partially flooded in most cases. Elastic deformation of the skirt is an essential part of the model. In this model, the piston dynamic behaviour and frictional and impact forces are predicted as functions of crank angle and are examined in detail. Parameters investigated include piston skirt profile, piston-to-liner clearance, surface roughness, and oil availability. The results show that some of these parameters have profound effects on the frictional and impact forces at the piston skirt/liner interface, and therefore, they have the potential to optimize the piston frictional power loss. Correlations and non-dimensional scaling laws are developed to illustrate the basic governing phenomena. These results aim to provide a set of quantitative design guidelines.

Isothermal transient analysis of piston skirt-to-cylinder wall contacts under combined axial, lateral and tilting motion

The paper describes the combined axial, lateral and tilting motions of piston within the confine of cylinder bore, with sliding and normally approaching and separating contacts between the piston skirt and the cylinder wall on both the major and minor thrust sides. The methodology developed undertakes combined solution for inertial dynamics of the piston, together with transient elastohydrodynamic analysis of both contacts. It also includes important practical features of the contacting surfaces, such as the axial form relieving of the piston skirt profile. The space–time solver uses Newmark β-type time marching integrator, as well as the effective influence Newton–Raphson method for space-domain solution of the elastohydrodynamic conjunctions in each step of time. This approach, not hitherto reported for this type of conforming contacts yields accurate predictions of lubricant film thickness and pressure distribution within computationally acceptable times, given the inclusion of level of detail in the model.

Study of the simulation of piston skirt contact

In order to reduce the number of engine tests, it is very important to simulate the piston-cylinder bore contact. In this paper, the method of piston skirt-cylinder bore contact pressures have been studied by using the data of piston skirt profiles, its stiffness, and its thermal expansions. Therefore, piston skirt-cylinder bore contact pressures finely correlate with the skirt conditions after running tests.

Numerical simulation of oil film distribution over a piston skirt. Effect of piston skirt profile.

Numerical simulation of oil film distribution over a piston skirt. Effect of piston skirt profile.

A numerical study on piston slap in diesel engines. (2nd report. Effect of piston skirt profile).

Piston slap phenomena in diesel engines were numerically studied by a method which can deal with pistons and cylinders with arbitrary profiles. The effects of piston skirt profile and piston clearance were discussed. The results showed that a piston with a curved profile such as a barrel type piston is more advantageous than a piston with a constant radius for the reduction of piston slap impact.