Piston Rings Friction Comparison in a Free Piston and Conventional Crankshaft Engines

2018 ◽  
Author(s):  
Mehar Bade ◽  
Nigel N. Clark ◽  
Terence Musho ◽  
Parviz Famouri
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engines ◽  
Asperity Contact ◽  
Combustion Engines ◽  
Power Losses ◽  
Piston Rings ◽  
Free Piston ◽  
Oil Film ◽  
Frictional Losses ◽  
Free Piston Engine

The conventional internal combustion engines driven by crankshafts and connecting rod mechanisms are restrained by combustion, thermal and mechanical inefficiencies. The Oscillating Free Piston Linear Engine Alternator (OFPLEA) produces electric power with no need to modify the reciprocating motion to rotary motion. In the most common geometry it consists of a linear alternator driven cyclically by one or two internal combustion engines. With the elimination of crankshaft mechanism linkages, the free piston engine offers potential benefits over crankshaft engines in terms of total mechanical losses. A significant proportion of 5% to 12% of total fuel energy in conventional engines is consumed to overcome the frictional losses. This research investigation addresses an analytical and numerical model to simulate the tribological performance of piston rings in an OFPLEA engine. The results are then compared with results from an equivalent conventional crankshaft driven engine. This axisymmetric, mixed lubrication tribological model is developed on the hydrodynamic process defined by Patir and Cheng’s modified Reynolds equation and an asperity contact process as defined by Greenwood and Tripp’s rough surface dry contact model. The asperity contact pressure distribution, hydrodynamic pressure distribution, lubricant oil film thickness, frictional force and frictional power losses are calculated using an explicit finite difference approach. In the absence of spring-dominated OFPLEA system, dissimilarity in the piston motion profile for compression and power stroke exhibited two different oil film thickness peaks. Whereas a similar oil film thickness peaks are observed for conventional engine due to the controlled and stable operation maintained by crankshaft mechanism. The simulation results state that the frictional losses due to piston ring - cylinder liner contact are found to be lower for a free piston engine than for those of a corresponding crankshaft engine. The simulated piston ring frictional power losses are found to be 342.8 W for the OFPLEA system and 382.6 W for the crankshaft engine. Further, an overall system efficiency improvement of 0.6 % is observed for an OFPLEA engine due to these reduced frictional losses from piston rings.

Modeling the Lubrication, Dynamics, and Effects of Piston Dynamic Tilt of Twin-Land Oil Control Rings in Internal Combustion Engines

1999 ◽  
Vol 122 (1) ◽  
pp. 119-129 ◽  
Author(s):  
T. Tian ◽  
V. W. Wong
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engines ◽  
Three Dimensional ◽  
Internal Combustion ◽  
Asperity Contact ◽  
Combustion Engines ◽  
Ring Groove ◽  
Oil Film ◽  
Oil Transport ◽  
Axial Forces

A theoretical model was developed to study the lubrication, friction, dynamics, and oil transport of twin-land oil control rings (TLOCR) in internal combustion engines. A mixed lubrication model with consideration of shear-thinning effects of multigrade oils was used to describe the lubrication between the running surfaces of the two lands and the liner. Oil squeezing and asperity contact were both considered for the interaction between the flanks of the TLOCR and the ring groove. Then, the moments and axial forces from TLOCR/liner lubrication and TLOCR/groove interaction were coupled into the dynamic equations of the TLOCR. Furthermore, effects of piston dynamic tilt were considered in a quasi three-dimensional manner so that the behaviors of the TLOCR at different circumferential locations could be studied. As a first step, variation of the third land pressure was neglected. The model predictions were illustrated via an SI engine. One important finding is that around thrust and anti-thrust sides, the difference between the minimum oil film thickness of two lands can be as high as several micrometers due to piston dynamic tilt. As a result, at thrust and anti-thrust sides, significant oil can pass under one land of the TLOCR along the bore, although the other land perfectly seals the bore. Then, the capabilities of the model were further explained by studying the effects of ring tension and torsional resistance on the lubrication and oil transport between the lands and the liner. The effects of oil film thickness on the flanks of the ring groove on the dynamics of the TLOCR were also studied. Friction results show that boundary lubrication contributes significantly to the total friction of the TLOCR. [S0742-4795(00)01801-9]

Experimental Investigation of Oil Accumulation in Second Land of Internal Combustion Engines

2005 ◽  
Vol 127 (1) ◽  
pp. 206-212
Author(s):  
T. Icoz ◽  
Z. Dursunkaya
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Engine Oil ◽  
Combustion Engines ◽  
Oil Consumption ◽  
Oil Accumulation ◽  
Oil Film ◽  
Piston Cylinder ◽  
Total Oil

Blowback of engine oil suspended in combustion gases, when the gas flows from the piston second land back into the combustion chamber, is believed to contribute to oil consumption and hydrocarbon emissions in internal combustion engines. Oil accumulation in the region between top and second compression rings is a factor that influences this phenomenon. The effects of individual parameters, such as oil film thickness and viscosity, however, have still not been understood. The present study was aimed at constructing an experimental setup to study the effect of oil film thickness on oil accumulation in the second land of internal combustion engines. Due to the inherent difficulties of experimentation on production engines, a modeled piston-cylinder assembly was constructed. Total oil accumulation in the modeled second land after a single piston stroke was measured and compared to oil consumption in operating engines.

An analytical study of tribological parameters between piston ring and cylinder liner in internal combustion engines

2016 ◽  
Vol 230 (4) ◽  
pp. 329-349 ◽  
Author(s):  
Mohamed Kamal Ahmed Ali ◽  
Hou Xianjun ◽  
Richard Fiifi Turkson ◽  
Muhammad Ezzat
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engines ◽  
Piston Ring ◽  
Cylinder Liner ◽  
Combustion Engines ◽  
Oil Viscosity ◽  
Oil Film ◽  
Ring Assembly ◽  
Ring Dynamics ◽  
Tribological Parameters

This paper presents a model to study the effect of piston ring dynamics on basic tribological parameters that affect the performance of internal combustion engines by using dynamics analysis software (AVL Excite Designer). The paramount tribological parameters include friction force, frictional power losses, and oil film thickness of piston ring assembly. The piston and rings assembly is one of the highest mechanically loaded components in engines. Relevant literature reports that the piston ring assembly accounts for 40% to 50% of the frictional losses, making it imperative for the piston ring dynamics to be understood thoroughly. This analytical study of the piston ring dynamics describes the significant correlation between the tribological parameters of piston and rings assembly and the performance of engines. The model was able to predict the effects of engine speed and oil viscosity on asperity and hydrodynamic friction forces, power losses, oil film thickness and lube oil consumption. This model of mixed film lubrication of piston rings is based on the hydrodynamic action described by Reynolds equation and dry contact action as described by the Greenwood–Tripp rough surface asperity contact model. The results in the current analysis demonstrated that engine speed and oil viscosity had a remarkable effect on oil film thickness and hydrodynamic friction between the rings and cylinder liner. Hence, the mixed lubrication model, which unifies the lubricant flow under different ring–liner gaps, is needed via the balance between the hydrodynamic and boundary lubrication modes to obtain minimum friction between rings and liner and to ultimately help in improving the performance of engines.

scholarly journals Parametric Analysis of the Effect of Engine Speed and Load on the Hydrodynamic Performance of the Lubricant in Diesel Engine

2020 ◽  
Vol 64 (4) ◽  
pp. 299-306
Author(s):  
Brahim Menacer ◽  
Mostefa Bouchetara
Keyword(s):  
Film Thickness ◽  
Fuel Consumption ◽  
Internal Combustion Engines ◽  
Piston Ring ◽  
Engine Speed ◽  
Internal Combustion ◽  
Hydrodynamic Performance ◽  
Power Losses ◽  
Oil Consumption ◽  
Oil Film

The oil consumption in an internal combustion engine is an important source of pollution and particulate emissions, main efforts are done by the manufacturers to reduce to the maximum the impact of the oil consumption on the emissions of the engine, and to satisfy the increasingly rigorous standards of pollution. The losses by friction due to piston ring friction explain 20 % of the total mechanical losses in internal combustion engines. A reduction in piston ring friction would therefore result in higher efficiency, lower fuel consumption and reduced emissions. The goal of this study is to develop a numerical method by using of GT-Suite software to analyze the influence of engine speed and engine load during the working cycle on oil film thickness, frictional force, power losses. Our predicted results were validated with the experimental data of a previous study, and they have shown a good agreement. The results in the current analysis demonstrated that the engine speed and load have a remarkable effect on oil film thickness, friction force and friction power losses between the top ring and cylinder liner. So, it would help in reducing friction as well as making a contribution towards the improvement of engine performance such as torque, efficiency and fuel consumption.

An Analysis of Ring Temperature, Oil Film Temperature and Oil Film Thickness on a Piston Ring of an IC Engine in Consideration of Ring Movement: Effect of Ring Sliding Face Profile

2007 ◽  
Author(s):  
Takashi Ishijima ◽  
Akiko Shimada ◽  
Shinichiro Kodaira ◽  
Hiroshi Sakamoto ◽  
Yasuo Harigaya ◽  
...  
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engines ◽  
Piston Ring ◽  
Characteristic Temperature ◽  
Combustion Engines ◽  
Ring Groove ◽  
Ic Engine ◽  
Lower Face ◽  
Oil Film ◽  
Movement Effect

For the clarification of the lubrication and thermal problems between ring and liner of internal combustion engines, an unsteady thermohydrodynamic lubrication model considering the ring temperature and the ring movement in the piston ring groove was developed. Then using the method of thermohydrodynamic lubrication, the effect of the profile of top ring sliding face on the oil film thickness and friction losses was analyzed. The ring is width of 3mm and thickness of 4.5mm. Profiles in sliding face of the ring used are two types. Ring 1 has a flat in the middle and a roundness in the corner, and Ring 2 has a barrel face. The ring temperature on the sliding surface shows the characteristic temperature distribution, and the temperature difference between ring lower face and middle of ring has about 19 °C. The oil film thickness changed in a cycle increases with increase of barrel height. The friction mean effective pressure FMEP decreases with the increase of barrel height both Ring 1 and Ring 2. FMEP of Ring 2 is more effective than that of Ring 1.

Effects of Liner Surface Texturing on Ring/Liner Friction in Large-Bore IC Engines

2006 ◽  
Author(s):  
Rosalind Takata ◽  
Yong Li ◽  
Victor W. Wong
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engines ◽  
Surface Texturing ◽  
Friction Reduction ◽  
Asperity Contact ◽  
Oil Film ◽  
Surface Features ◽  
Flow Factor ◽  
Liner Surface ◽  
Ring Pack

Well-designed surface texturing may be used to reduce ring/liner friction and increase efficiency in internal combustion engines. This study investigated the effects of textures of either grooves or dimples on ring/liner friction, in the hydrodynamic and mixed regimes. Existing MIT models were used to conduct this research. The ring-pack model is based on averaged flow-factor Reynolds analysis, and is used in conjunction with a deterministic model for flow factor calculation. Although this advanced model is applicable in a wide range of cases, the surface textures studied here are very different than a typical liner surface, and can be represented only approximately by the averaged analysis upon which the ring simulation is based. For this reason, this analysis of surface features has focused on a parametric study, the goal of which is to analyze trends relating ring/liner friction to surface parameters, and to make a general evaluation of the potential of surface texturing to reduce ring-pack losses. In the hydrodynamic and mixed regimes, surface texturing affects the fluid pressure in the lubricant between ring and liner, thus affecting the ability of the oil film to support the ring load. If the effect of the texturing is to impede the flow of lubricant, the result will be an increase in oil film thickness. This causes friction reduction in two ways: if asperity contact was present, it is reduced; and the increase in film thickness causes a decrease in shear rate, thus decreasing oil shear stress. It was found that surfaces with both dimpled and grooved textures could cause friction reduction through this mechanism, with deeper features and more transverse groove patterns causing the greatest reduction. Friction also decreased with increasing area ratio (the percentage of the surface that is occupied by the surface features) for both grooves and dimples, and was only slightly dependent on groove width and dimple diameter. Because the effect of the surface texturing is on hydrodynamic effects in the oil, it is strongly coupled with lubricant properties. If surface texturing and lubricant viscosity are optimized together side effects such as oil consumption and wear can be mitigated, while friction can be reduced even further than it is via surface texturing alone. This possibility was also briefly considered in this study.

scholarly journals Investigations for a Trajectory Variation to Improve the Energy Conversion for a Four-Stroke Free-Piston Engine

2021 ◽  
Vol 11 (13) ◽  
pp. 5981
Author(s):  
Robin Tempelhagen ◽  
Andreas Gerlach ◽  
Sebastian Benecke ◽  
Kevin Klepatz ◽  
Roberto Leidhold ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Alternative Fuels ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Optimal Operation ◽  
Combustion Engines ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine ◽  
Future Work

Internal combustion engines with a crankshaft have been successfully developed for many years. They are lacking in the fact that the piston trajectory, i.e., position as a function of time, is limited by the crankshaft motion law. Position-controlled electric linear machines directly coupled to the piston allow to realize free-piston engines. Unlike the crankshaft-based engines, they allow for a higher degree of freedom in shaping the piston trajectory, including adaptive compression ratios, which enables optimal operation with alternative fuels. The possibility of adapting the stroke course results in new degrees of freedom with which the combustion process can be optimized. In this work, four-stroke trajectories with different amplitudes and piston dynamics have been proposed and analyzed regarding efficiency. A simulation model was created based on experimental measurements for testing the proposed trajectories. It could be proved that the variation of the trajectory resulted in an improvement of the overall efficiency. The trajectories were described analytically so that they can be used for a prototype in a future work.

Sign in / Sign up

Export Citation Format

Share Document