Coupled Elastodynamics of Piston Compression Ring Subject to Sweep Excitation

The piston compression ring's primary function is to seal the combustion chamber, thus mitigating gas leakage to the crankcase and avoiding loss of pressure loading. As a result, the ring is meant to conform closely to the cylinder surface which promotes increased friction. The compression ring is subjected to combustion pressure loading, ring tension, varying inertial force and friction. It is a slender ring of low mass, thus undergoes complex elastodynamic behaviour, when subjected to a multitude of forces. These motions occur in the ring's radial in-plane and axial out-of-plane dynamics, which comprise flutter, ring axial jump, compression-extension, ring twist and rotational drag. An implication of these motions can be loss of sealing, gas blow-by, loss of power and lubricant degradation/oil loss, to name but a few. Consequently, understanding and accurately predicting ring dynamic behaviour under transient conditions is an important step in any subsequent modelling for evaluation of cylinder system efficiency. There have been a plethora of investigations for ring dynamics, often decoupling the ring behaviour in its in-plane and out-of-plane motions. This approach disregards any transfer of dynamic energy from one degree of freedom to another which is only applicable to rectangular ring cross-sections. Alternatively, there are computationally intensive approaches such as finite element analysis which are not conducive for inclusion in any subsequent system level engine modelling where ring response alters in an instantaneous manner. This would require embedded finite element analysis within a transient analysis. This paper presents a finite difference numerical analysis for coupled in-plane and out-of-plane motions of compression rings with practical cross-sectional geometries, which are mostly not rectangular. The formulated method can be integrated into a system level transient cyclic analysis of ring-bore contact. The presented approach takes into account the energy transfer between different degrees of freedom. The predictions are validated against precise non-contact measurements of ring elastodynamic behaviour under amplitude-frequency sweeps. This approach has not hitherto been reported in literature and constitutes the main contribution of the paper

Effect of cylinder de-activation on the tribological performance of compression ring conjunction

The paper presents transient thermal-mixed-hydrodynamics of piston compression ring-cylinder liner conjunction for a 4-cylinder 4-stroke gasoline engine during a part of the New European Drive Cycle (NEDC). Analyses are carried out with and without cylinder de-activation (CDA) technology in order to investigate its effect upon the generated tribological conditions. In particular, the effect of CDA upon frictional power loss is studied. The predictions show that overall power losses in the piston-ring cylinder system worsen by as much as 10% because of the increased combustion pressures and liner temperatures in the active cylinders of an engine operating under CDA. This finding shows the down-side of this progressively employed technology, which otherwise is effective in terms of combustion efficiency with additional benefits for operation of catalytic converters. The expounded approach has not hitherto been reported in literature

Combined experimental and flexible multibody dynamic investigation of high energy impact-induced driveline vibration

Lightly damped non-linear dynamic driveline components are subjected to excitation with rapid application of clutch and/or throttle. Modern thin-walled driveshaft tubes respond with a plethora of structural-acoustic modes under such impulsive conditions, which are onomatopoeically referred to as clonk in the vehicle industry. The underlying mechanisms for the occurrence of this phenomenon are investigated, using combined experimentation and flexible multibody dynamics under impulsive impact conditions. The coincidence of high frequency structural modes, coupled with acoustic response is highlighted for the broad-band spectral response of the hollow driveshaft tubes. The cyclic relationship of clonk with the shuffle response of the driveline system is also established for transient decay of the clonk phenomenon. In particular, the multibody model is used to ascertain the effect of vehicle laden state on the propensity of driveline clonk, an approach no hitherto reported in literature

Processing and characterization of nanostructured Grade 2 Ti processed by combination of warm isothermal ECAP and extrusion

In this study, combined multi pass equal channel angular pressing (ECAP), and subsequent warm extrusion at different temperatures are performed on commercial purity titanium. Mechanical and microstructural evolutions are then investigated. Since it was observed that the four passes ECAP processed sample showed the best strength and reasonable elongation, this sample was selected for studying the extrusion temperature effects on the structure and mechanical properties of Grade 2 titanium. Therefore, the 4th passes ECAP processed sample was extruded at different temperatures of 300 °C, 350 °C, 400 °C, 450 °C and 500 °C. The result revealed that the best mechanical properties were achieved from the specimen processed by four passes ECAP followed by warm extrusion at 300 °C. The strength, and hardness of this sample were considerably improved in comparison with that of the unprocessed sample. Also, its ultra-fine grained and nanograined microstructure were homogeneous, with a grain size ranged from 40 to 200 nm with an average grain size of about 123 nm. It was seen that the mechanical properties of some samples after applying this combined process (ECAP + warm extrusion) are comparable with those of Grade 5 titanium which is commonly used in medical applications but contains alloying elements that are toxic to human health

Combined Experimental and Flexible Multibody Dynamic Investigation of High Energy Impact Induced Driveline Vibration

Lightly damped non-linear dynamic driveline components are subjected to excitation with rapid application of clutch and/or throttle. Modern thin-walled driveshaft tubes respond with a plethora of structural-acoustic modes under such impulsive conditions, which are onomatopoeically referred to as clonk in the vehicle industry. The underlying mechanisms for the occurrence of this phenomenon are investigated, using combined experimentation and flexible multi-body dynamics under impulsive impact conditions. The coincidence of high-frequency structural modes, coupled with acoustic response is highlighted for the broad-band spectral response of the hollow driveshaft tubes. The cyclic relationship of clonk with the shuffle response of the driveline system is also established for transient decay of the clonk phenomenon. In particular, the multi-body model is used to ascertain the effect of vehicle laden state on the propensity of driveline clonk, an approach not hitherto reported in literature

The effect of cylinder de-activation on thermo-friction characteristics of the connecting rod bearing in the New European Drive Cycle (NEDC)

The over-riding objective in modern engine development is fuel efficiency. This has led to a host of pursued measures, including down-sizing (a lower number of cylinders), high output power-to-weight ratio, variable valve activation or cylinder de-activation (CDA) as well as a gradual trend towards mild or micro-hybrid technology. Furthermore, The main aim is to combine a suitable combination of the aforementioned methods with various driving conditions in order to reduce thermal and frictional losses as well as meeting the ever stringent emission directives as outlined in the NEDC. Another imperative is to ensure good NVH refinement which can be adversely affected by application of the above trends, such as light weight constructions and exacerbated power torque variations with CDA. The highlighted issues affect all the load bearing conjunctions in an engine. In particular, increased load fluctuations with CDA can also affect the whirl stability of big-end bearings. Therefore, the current paper concentrates on the issues that affect the big-end bearing thermo-frictional characteristics and dynamic stability in NEDC cycle. The predictive approach, which is critical in a multi-variate problem of this kind, includes determination of regime of lubrication under fluctuating loads and rictional characteristics contributed by both elastohydrodynamics of the bearing overlay as well as boundary friction as the result of asperity interactions. Predictive results include applied dynamics, contact kinematics, frictional power loss, maximum lubricant temperature and minimum film thickness variations during the NEDC. The difference between the CDA mode and the normal mode (all active cylinders). These show that the general benefits accrued through fuel efficiency do not necessarily conform to improved big end bearing frictional efficiency

Calculation of the kinematics of hypoid gears towards developing a method for an equivalent crossed helical gear pair selection for use in tribological experimental evaluations

To experimentally verify power loss and friction for hypoid gears, measurements in a closed power-loop test rig are necessary. However, these are costly and mechanically complex, since they require additional spur gear reducers in the loop. ISO directives document the use of crossed helical gear pairs as virtual gears for hypoids to calculate the sliding velocity since, the flank geometry at the mean point can be precisely represented. The use of such pairs can be a cost effective and simpler alternative for testing purposes. However, the validity of this analogy regarding contact mechanics and tribology for the full mesh cycle has not been investigated hitherto. In the current study a new method for calculating the sliding and rolling speed along the full path of contact of a hypoid gear pair is presented. Cutter kinematics are considered, for the accurate definition of the contact bodies. Using TCA, the load distribution on the tooth under quasi-static conditions and the sliding velocity are calculated for comparison purposes. By applying a selection algorithm, a single experimental crossed helical gear pair is chosen aiming to simulate the contact conditions of hypoid gears. Two test scenarios are studied using EHL film thickness equations and friction models for evaluating the power loss. The contact is an elongated ellipse with varying directions of the sliding and sum velocities, which are considered in the model. The kinematic equivalence shows good agreement while the tribological equivalence is achievable using a reduced input torque

Priprava mikrokuglica s antigenom leptospira od biološki razgradivih alginatnih polimera.

Leptospirosis is a worldwide zoonosis caused by pathogenic Leptospira spp. Although the currently available whole cell leptospiral vaccines can induce protection against Leptospirosis, further study for a new generation of vaccine that can stimulate long-term immunity is needed. Biodegradable microspheres as antigen delivery systems have been extensively investigated for decades, especially those based on hydrophilic polymers, such as alginate and chitosan, which have excellent biocompatibility, non-toxicity and biodegradability. The aim of this study was to prepare and characterize alginate microspheres as an antigen delivery system for immunization against leptospirosis. Alginate microspheres containing Leptospiral antigen (LA) were prepared by an emulsification method and characterized for shape, size distribution, loading efficiency (LE), loading capacity (LC) and release profie. The effects of some parameters (such as concentration of alginate and emulsifiers and stirring rate) on microspheres characteristics were investigated. The optimal condition parameters for the preparation of LA loaded alginate microspheres were estimated. The optimum concentrations were obtained for alginate and emulsifiers, 3.5 % (w/v), span 80 (0.2 % w/v) and tween 80 (3.75 % w/v), respectively. Moreover, appropriate homogenizing rate was obtained at 500 rparticle size of the microspheres as 200 μm, loading efficiency 97 % and loading capacity 8 %. A suitable release profile was observed for in vitro release test of LA from alginate microspheres over an extended period of time (192 hours). These results make the alginate microspheres particularly interesting for an LA delivery system.pm. Our results showed the mean particle size of the microspheres as 200 μm, loading effiiency 97 % and loading capacity 8 %. A suitable release profile was observed for in vitro release test of LA from alginate microspheres over an extended period of time (192 hours). These results make the alginate microspheres particularly interesting for an LA delivery system.Leptospiroza je zoonoza prouzročena patogenim vrstama roda Leptospira, a proširena je diljem svijeta. Iako današnja cjepiva protiv leptospiroze, proizvedena od cijelih bakterijskih stanica, mogu pružiti zaštitu od leptospiroze, potrebna su daljnja istraživanja nove generacije cjepiva koja će moći potaknuti tvorbu dugotrajne imunosti. Biološki razgradive mikrokuglice istražuju se desecima godina kao mogućnost sporog otpuštanja antigena, a posebice su zanimljive one od hidrofilnih polimera kao što je alginat i kitosan, koji imaju izvrsnu biološku kompatibilnost, nisu toksični, a biološki su razgradivi. Svrha ovog rada bila je pripraviti alginatne mikrokuglice i odrediti njihova svojstva pogodna za otpuštanje antigena u postupku imunizacije protiv leptospiroze. Alginatne mikrokuglice s antigenom leptospira bile su pripravljene postupkom emulgacije te im je bio određen oblik, opseg distribucije, učinkovitost ugradnje antigena u mikrokuglice, kapacitet ugradnje i profil otpuštanja antigena. Istraženi su učinci nekih pokazatelja (kao što je koncentracija alginata i emulgatora te omjer miješanja) na obilježja mikrokuglica. Procijenjeni su optimalni uvjeti za pripravu alginatnih mikrokuglica na koje je vezan antigen leptospira. Optimalna koncentracija za alginat bila je 3,5 % (w/v), a emulgator span 80 (0,2 % w/v) i tween 80 (3,75 % w/v). Odgovarajuća homogenizacija postignuta je na 500 okretaja. Rezultati su pokazali da je srednja veličina mikrokuglica bila 200 μm, učinkovitost ugradnje antigena 97 %, a kapacitet 8 %. In vitro je ustanovljeno da se antigen leptospira oslobađao s alginatnih mikrokuglica tijekom 192 sata. Ti rezultati pokazuju da alginatne kuglice mogu biti od posebnog interesa za oslobađanje antigena leptospira u organizmu

Heavy metals in recycled pastry packages and pastries

The safe use of recycled paper and board material for food packaging applications is a major area of investigations. Therefore, the aim of current study was to evaluate the amount of heavy metals in recycled paper pastry packages and measurement of migration over the time into pastries. In this study, the presence of heavy metals in common confectionery packaging and effects of storage time and kind of pastry on the migration are investigated. The results of the study indicate that harmful metals such as Pb are detected at high concentrations in most of the recycled boxes that are used for pastry packaging, and heavy metals could migrate from the recycled packages into food during usage. It seems that the procedure of preparing recycled paperboard for food packaging should be reconsidered

Elastodynamics of piston compression rings

The piston ring pack accounts for a disproportionate amount of the total engine frictional losses. The frictional behaviour of piston rings is significantly affected and governed by its flexible dynamics. The dynamically changing shape of the ring determines its contact geometry with the cylinder liner and hence affects the frictional losses. The compression ring undergoes a multitude of complex motions during the engine cycle prescribed by the gas pressure, contact reaction, ring tension, friction between the ring and its groove and inertial forces that excite a plethora of the ring’s modal responses. This adversely compromises the functionality of the ring through a number of undesired phenomena such as ring flutter, twist, rotation and jump. Therefore, a prerequisite for improving the prediction of tribological conditions is an accurate determination of the ring’s elastodynamic response. This paper presents a methodology to directly solve the governing differential equations of motion for different forms of beam cross-section, where the shear and mass centres are not coincident, typical of the complex cross-sections of a variety of different piston compression rings. Combined numerical and experimental investigations are undertaken to determine the dynamic behaviour of the compression ring