scholarly journals Assessment of friction from compression ring conjunction of a high-performance internal combustion engine: A combined numerical and experimental study

2015 ◽  
Vol 230 (12) ◽  
pp. 2073-2085 ◽  
Author(s):  
M Gore ◽  
R Rahmani ◽  
H Rahnejat ◽  
PD King
Keyword(s):  
High Performance ◽  
Combustion Engine ◽  
Viscous Friction ◽  
Cylinder Liner ◽  
Lubricant Film ◽  
Film Rupture ◽  
Compression Ring ◽  
Piston Cylinder ◽  
Direct Measurements ◽  
Good Agreement

The paper presents direct measurement of in-cylinder friction from a single cylinder motocross race engine under motored conditions and compares the same with a new analytical predictive method. These conditions are encountered in piston–cylinder system with the application of cylinder deactivation (CDA) technology, which is a growing trend. The analytical method takes into account the various regions within instantaneous contact of compression ring–cylinder liner, including lubricant film rupture, cavitation zone and the subsequent lubricant film reformation. The analysis also includes the effect of boundary friction and lubricant rheology. The predictions and direct measurements of cyclic friction show good agreement and indicate dominance of viscous friction under the investigated engine running conditions. In particular, it is shown that the compression ring contribution to in-cycle friction is most pronounced in the region of high cylinder pressures because of combined Poiseuille friction and some boundary solid interactions. The combined experimental-analytical approach has not hitherto been reported in literature.

A Finite Element Numerical Methodology for the Fatigue Analysis of Cylinder Liners of a High Performance Internal Combustion Engine

2019 ◽  
Vol 827 ◽  
pp. 288-293 ◽  
Author(s):  
Saverio Giulio Barbieri ◽  
V. Mangeruga ◽  
Matteo Giacopini ◽  
Carlo Laurino ◽  
Mariano Lorenzini
Keyword(s):  
Finite Element ◽  
High Performance ◽  
Linear Models ◽  
Combustion Engine ◽  
Cylinder Liner ◽  
Fatigue Behaviour ◽  
Load Cycle ◽  
Computational Effort ◽  
Simplified Approach ◽  
Cylinder Liners

In this paper a numerical methodology is proposed, which aims at predicting the fatigue behaviour of engine cylinder liners in an eight-cylinder V-type four-stroke turbocharged engine. A preliminary kinematic and dynamic study of the crank mechanism is fulfilled in order to properly identify the load cycle that involves the cylinder liner. Finite Element analyses, both thermal and thermo-mechanical, are performed to evaluate the stress and the strain of the component. In particular, non-linear models are developed to mimic the piston-liner interaction when subjected to different loading conditions. A simplified approach is proposed in order to reduce the computational effort of the simulations. FEM results are then processed employing the multiaxial Dang Van fatigue criterion.

Application of Supersonic Flame Spraying for Next Generation Cylinder Liner Coatings

2012 ◽  
Vol 533 ◽  
pp. 91-97 ◽  
Author(s):  
Andrei Manzat ◽  
A. Killinger ◽  
R. Gadow
Keyword(s):  
Corrosion Resistance ◽  
Surface Topography ◽  
High Performance ◽  
Combustion Engine ◽  
Cylinder Liner ◽  
Flame Spraying ◽  
Oil Consumption ◽  
Functional Coatings ◽  
Coating Materials ◽  
Cylinder Liners

Rising demands for ecologically friendly automotive engines require a significant decrease in fuel consumption and emissions. Also the recent trend of downsizing engines demands for high performance materials for internal combustion engine applications. Tribologically functional coatings applied by supersonic flame spraying help in boosting the engine efficiency by reducing the internal friction and improving the durability and wear resistance of the cylinder running surface much-needed for engine downsizing tasks together with a high corrosion resistance enabling the use of bio fuels. In addition, the tailored surface topography of the thermal spray coatings help in supporting advantageous friction states and thereby show the benefit of reducing the oil consumption resulting in reduced emissions. The thermally sprayed coatings were applied using HVOF and HVSFS processes together with a specially designed spray gun trajectory in order to achieve a fast and cost efficient coating procedure. Several different coating materials, including novel nanostructured powders, have been investigated and compared to state-of-the-art cylinder liners. The performance of the coated cylinder liners regarding wear and corrosion resistance, friction coefficient and effects of the surface topography have been investigated in various test setups including engine tests.

scholarly journals On the Transient Three-Dimensional Tribodynamics of Internal Combustion Engine Top Compression Ring

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
C. Baker ◽  
S. Theodossiades ◽  
R. Rahmani ◽  
H. Rahnejat ◽  
B. Fitzsimons
Keyword(s):  
Combustion Engine ◽  
Fuel Efficiency ◽  
Three Dimensional ◽  
Cylinder Liner ◽  
Internal Combustion ◽  
Ic Engine ◽  
Gas Leakage ◽  
Compression Ring ◽  
Frictional Losses ◽  
Harmful Emissions

There are increasing pressures upon the automotive industry to reduce harmful emissions as well as meeting the key objective of enhanced fuel efficiency, while improving or retaining the engine output power. The losses in an internal combustion (IC) engine can be divided into thermal and parasitic as well as due to gas leakage because of untoward compression ring motions. Frictional losses are particularly of concern at low engine speeds, assuming a greater share of the overall losses. Piston–cylinder system accounts for nearly half of all the frictional losses. Loss of sealing functionality of the ring pack can also contribute significantly to power losses as well as exacerbating harmful emissions. The dynamics of compression ring is inexorably linked to its tribological performance, a link which has not been made in many reported analyses. A fundamental understanding of the interplay between the top compression ring three-dimensional elastodynamic behavior, its sealing function and contribution to the overall frictional losses is long overdue. This paper provides a comprehensive integrated transient elastotribodynamic analysis of the compression ring to cylinder liner and its retaining piston groove lands' conjunctions, an approach not hitherto reported in the literature. The methodology presented aims to aid the piston ring design evaluation processes. Realistic engine running conditions are used which constitute international drive cycle testing conditions.

scholarly journals On the Effect of Transient In-Plane Dynamics of the Compression Ring Upon Its Tribological Performance

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
C. Baker ◽  
R. Rahmani ◽  
S. Theodossiades ◽  
H. Rahnejat ◽  
B. Fitzsimons
Keyword(s):  
Combustion Engine ◽  
Essential Feature ◽  
Tribological Performance ◽  
Element Analysis ◽  
Compression Ring ◽  
Piston Cylinder ◽  
Transient Nature ◽  
Fea Model ◽  
Elastodynamic Response ◽  
Tribological Analysis

Energy losses in an internal combustion engine are either thermal or parasitic. The latter are the mechanical inefficiencies, chiefly as the result of generated friction. Nearly half of these losses are attributed to the piston–cylinder system. During idle and at low engine speeds, friction is the major contributor to the overall engine losses. In particular, the rather small top compression ring accounts for a disproportionate share. Therefore, detailed understanding of compression ring tribology/dynamics (referred to as tribodynamics) is essential. Moreover, the ring’s primary sealing function may be breached by its elastodynamic behavior. The reported analyses in literature do not account for the transient nature of ring elastodynamics, as an essential feature of ring–bore tribology. The transient in-plane dynamics of incomplete rings are introduced in the analysis and verified using a finite element analysis (FEA) model, in order to address this shortcoming. The methodology is then coupled with the tribological analysis of the top compression ring. Comparison is made with experimental measurements which show the validity of the proposed method. The radial in-plane elastodynamic response of the ring improves the accuracy of the frictional power loss calculations.

scholarly journals Optimisation of the piston compression ring for improved energy efficiency of high performance race engines

2017 ◽  
Vol 231 (13) ◽  
pp. 1806-1817 ◽  
Author(s):  
Nick Morris ◽  
Mahdi Mohammadpour ◽  
Ramin Rahmani ◽  
Homer Rahnejat
Keyword(s):  
Genetic Algorithm ◽  
High Performance ◽  
Close Contact ◽  
Significant Proportion ◽  
Cylinder Liner ◽  
Energy Losses ◽  
Loss Reduction ◽  
Hydrodynamic Analysis ◽  
Compression Ring ◽  
Liner Surface

The primary function of the piston compression ring is to seal the combustion chamber from the bottom end of the engine. As a result, its conformance to the cylinder liner surface is of prime importance. This close-contact contiguity results in increased friction, making this contact conjunction responsible for a significant proportion of energy losses. The frictional losses can be as much as 2–6% of the expended fuel energy, which is quite significant for such a diminutive contact. Under these conditions, the geometrical profile, the surface topography and the inertial properties of the ring assume significant importance. The paper presents an integrated mixed-hydrodynamic analysis of the compression ring–cylinder liner contact with multi-parameter optimisation, based on the use of a genetic algorithm. The multi-objective functionality includes minimisation of the parasitic energy loss, reduction in the incidence of asperity level interactions as well as minimisation of the ring mass. Both cold running engine conditions and hot running engine conditions in line with the New European Drive Cycle were considered. Hitherto, such an approach has not been reported in the literature.

Cavitating Flow in Engine Piston Ring-Cylinder Liner Conjunction

2013 ◽  
Author(s):  
Hamed Shahmohamadi ◽  
Ramin Rahmani ◽  
Homer Rahnejat ◽  
Paul King ◽  
Colin Garner
Keyword(s):  
Cylinder Liner ◽  
Continuous Phase ◽  
Main Function ◽  
Slider Bearing ◽  
Film Rupture ◽  
Two Phase ◽  
Engine Efficiency ◽  
Compression Ring ◽  
Load Carrying ◽  
Type Contact

The main function of piston compression ring is to seal the space between the piston and the liner, acting as slider bearing, subjected to reciprocating motion. The compression ring-cylinder liner conjunction has been extensively studied and it is responsible for a significant part of the total frictional parasitic power losses of an engine. Paradoxically, the required sealing function of the compressions ring can result in increased friction. Therefore, in order to improve engine efficiency, it is important to fundamentally understand and subsequently palliate some of these losses. Another problem in any slider bearing-type contact is lubricant film rupture and cavitation in the conjunctional outlet zone, reducing load carrying capacity and potentially leading to erosion damage. A cavitation model presented in two-phase flow CFD analysis of the ring-bore contact under isothermal conditions. Liquid flow is modelled as a continuous phase and a dispersed phase, representing cavitation bubbles. Many of the fundamental physical processes assumed to take place in cavitating flows are incorporated into the model.

scholarly journals Experimental Methods for Measuring the Viscous Friction Coefficient in Hydraulic Spool Valves

2021 ◽  
Vol 13 (13) ◽  
pp. 7174
Author(s):  
Massimo Rundo ◽  
Paolo Casoli ◽  
Antonio Lettini
Keyword(s):  
Friction Coefficient ◽  
Viscous Friction ◽  
Experimental Tests ◽  
Experimental Methods ◽  
Displacement Transducer ◽  
A Posteriori ◽  
Displacement Control ◽  
Spool Valves ◽  
The University ◽  
Good Agreement

In hydraulic components, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for numerical simulation. With particular reference to hydraulic spool valves, the viscous friction coefficient between the sliding and the fixed body is an unknown parameter that is normally set a posteriori in order to obtain a good agreement with the experimental data. In this paper, two different methodologies to characterize experimentally the viscous friction coefficient in a hydraulic component with spool are presented. The two approaches are significantly different and are both based on experimental tests; they were developed in two distinct laboratories in different periods of time and applied to the same flow compensator of a pump displacement control. One of the procedures was carried out at the Fluid Power Research Laboratory of the Politecnico di Torino, while the other approach was developed at the University of Parma. Both the proposed methods reached similar outcomes; moreover, neither method requires the installation of a spool displacement transducer that can significantly affect the results.

scholarly journals Calculating the optimal hematocrit under the constraint of constant cardiac power

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michal Sitina ◽  
Heiko Stark ◽  
Stefan Schuster
Keyword(s):  
Blood Flow ◽  
High Performance ◽  
Animal Species ◽  
Normal Values ◽  
Mechanical Load ◽  
The Body ◽  
Trade Off ◽  
Cardiac Power ◽  
Optimal Value ◽  
Good Agreement

AbstractIn humans and higher animals, a trade-off between sufficiently high erythrocyte concentrations to bind oxygen and sufficiently low blood viscosity to allow rapid blood flow has been achieved during evolution. Optimal hematocrit theory has been successful in predicting hematocrit (HCT) values of about 0.3–0.5, in very good agreement with the normal values observed for humans and many animal species. However, according to those calculations, the optimal value should be independent of the mechanical load of the body. This is in contradiction to the exertional increase in HCT observed in some animals called natural blood dopers and to the illegal practice of blood boosting in high-performance sports. Here, we present a novel calculation to predict the optimal HCT value under the constraint of constant cardiac power and compare it to the optimal value obtained for constant driving pressure. We show that the optimal HCT under constant power ranges from 0.5 to 0.7, in agreement with observed values in natural blood dopers at exertion. We use this result to explain the tendency to better exertional performance at an increased HCT.

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