Big end bearing losses with thermal cavitation flow under cylinder deactivation

The paper presents a mixed thermo-hydrodynamic analysis of elliptic bore bearings using combined solution of Navier–Stokes, continuity and energy equations for multi-phase flow conditions. A vapour transport equation is also included to ensure continuity of flow in the cavitation region for the multiple phases as well as Rayleigh–Plesset to take into account the growth and collapse of cavitation bubbles. This approach removes the need to impose artificial outlet boundary conditions in the form of various cavitation algorithms which are often employed to deal with lubricant film rupture and reformation. The predictions show closer conformance to experimental measurements than have hitherto been reported in the literature. The validated model is then used for the prediction of frictional power losses in big end bearings of modern engines under realistic urban driving conditions. In particular, the effect of cylinder deactivation (CDA) upon engine bearing efficiency is studied. It is shown that big-end bearings losses contribute to an increase in the brake specific fuel consumption with application of CDA contrary to the gains made in fuel pumping losses to the cylinders. The study concludes that implications arising from application of new technologies such as CDA should also include their effect on tribological performance

A CFD Study Comparing Surface Texture Features on Stationary and Entraining Surfaces

Surface texturing has been used to enhance the tribological properties of a variety of machine elements. Piston rings, face seals and journal bearings have all shown improved tribological performance due to introduction of surface textured features. A multitude of texture geometries, shape, locations and manufacturing techniques have been investigated in an attempt to optimize the texture features imparted on to the surface.A parameter which is commonly neglected during the investigation and application of textured features is on which surface (stationary or entraining) the textured feature shouldreside. The choice of which surface to texture is often influenced by the constraints of the available manufacturing process, material and expected wear of the contiguous surfaces.In some application the decision is less constrained and the speed of surface that the texture is applied to should be considered. A computational fluid dynamic analysis is conducted to investigate the influence of textures on the stationary and moving surface. The Navier-Stokes and continuity equations for multi-phase flow conditions are solved using a finite volume method. A vapour transport equation is also included to ensure continuity of flow in the cavitation region for the multiple phases as well as Rayleigh-Plesset to take into account the growth and collapse of cavitation bubbles. The results indicate that the position of surface texture features on either the stationary or entraining surface is a parameter worthy of consideration. It is recognized by the authors however that that this is not always possible due to manufacturing constraints, material choices and wear rates of surface

Thermal Analysis of an Oil Jet-Dry Sump Transmission Gear under Mixed-Elastohydrodynamic Conditions

mproved fuel efficiency and reduced emissions are key drivers for modern drivetrain systems. Therefore, in recent years, dry sumps with air–oil mist lubrication have been used for efficient transmission design in order to reduce the churning losses. With dry sumps, appropriate cooling measures should be implemented to dissipate the generated contact heat in an efficient manner. This paper integrates a tribological model with three-dimensional (3D) thermofluid analysis in order to predict the heat generated in the lubricated meshing gear contacts and its dissipation rate by an impinging oil jet in air–oil mist environment. Such an approach has not hitherto been reported in literature. The results show that the generated heat under realistic conditions cannot be entirely dissipated by the impinging oil jet in the air–oil mist transmission casing. Numerical results are used to derive extrapolated regressed equations for heat transfer purposes for time-efficient analysis. These conform well with the detailed numerical results

On the boundary conditions in multi-phase flow through the piston ring-cylinder liner conjunction

Prediction of load capacity and friction depends on the assumed boundary conditions. The inlet comprises swirl and counter flows, admitting only a portion of the inward flow into the conjunctional gap. At the contact exit, the lubricant film ruptures with multi-phase flow through a cavitation region. Therefore, the boundary conditions affect the load carrying capacity and friction. A Navier–Stokes solution of multi-phase flow, including vapour transport is presented, with determined realistic boundary conditions. The evaluated boundaries agree with potential flow analysis satisfying compatibility conditions, not hitherto reported in literature. The investigation is extended to the determination of optimum compression ring contacting geometry

Enhanced performance of optimised partially textured load bearing surfaces

Textured surfaces have been shown to provide enhanced tribological performance in a variety of contacts. Numerical analysis and optimisation methods are combined for application-oriented texture optimisation. However, an analytical approach is advantageous in providing more generic in-depth understanding of the nature of the relationships between texture parameters and objective functions, such as enhanced load carrying capacity and reduced friction. The paper outlines such an approach to obtain a set of global optimum design parameters for partially textured surfaces. The optimised results are expressed in dimensionless form, which enables their use for a variety of applications. The performance of optimised partially textured sliding surfaces is compared with the other conventional bearing geometries in their optimum state

Study on optimum exploitation of silver carp (Hypophthalmichthys molitrix)

The increasing demands of the growing populations can be met by developing aquaculture. However in order to provide suitable grounds for consumption which is acceptable to different conditions and tastes, apart from producing a variety of products we also need to improve the methods of marketing and consumption. The silver carp (Hypophthalmichthys molitrix) comprises about 50 to 85% of the composition of fish species in the polyculture of warm water species in Iran. However the difficulty in pretreatment of this species and the presence of pin bones are among the main reasons to restrict the demand of this species in the domestic markets, particularly in non-coastal provinces. In this project different aspects of silver carp processing studied as follow: 1. Use of fish fillet residuals in preparation of snack, cheese and ice cream 2. Use of fish meat in sausage and fish ball produce 3. Use of machinery to produce of without or low bones fillet and trimmed fillets. Fish sausages were studied in four experimental groups; Based on the results obtained it was evident that sausages in the experimental Group 1 (65% minced fish & 12 % soy bean oil) showed better taste and flavor as compared to those in the other groups. Fish ball were prepared using starch from four different sources (wheat, corn, potato and tapioca). Thirty different trials were tested by adding each starch source either individually or by mixing equal proportions of two sources of starch at a rate of 5, 10 and 15% to 80% ground meat of silver carp. Among trials containing two sources of starch, mixed trials with potato and wheat (5% potato + 5% wheat) were rated higher in organoleptic tests as compared to the other trials. Fifteen formulas were worked for preparing of fish cheese. The quality assessment of product showed that fish cheese in zero and 30 days after storage in 4֯ C were good and medium, respectively. Quantity enrichment of corn snack with FPC until 33% in fish snack preparation, have a best results among with other experiments. Fish ice cream made from fish protein concentrate type a that produced from silver carp in three steps by the extraction with isopropyl alcohol solvent and heat. The result showed that FPC replaced with 30%milk in ice cream formula has a best quality score. On the basis of recent findings, the deep part and a upper part on the back of the fish, like a relatively narrow band, are considered as boneless parts in silver carp. The aims of trimming project introduce best type of fillet trimming and machine for Silver Carp fillet. The results show percentage of waste in trimming by machinery line processing was less than handing, and fillet trimming speed by hand was most than machinery .Also final results of this study show machinery method or complex of handing and machinery for Silver carp fillet trimming are the best .speed rate in pine bone removing from silver carp fillet in handy method with using of transparent table and machinery method were 30-40 min per fish and 15 second per fish, respectively. Removing efficiency of bones from fillets in handy and machinery method were 50-60 and 90 %, respectively

Surface specific asperity model for prediction of friction in boundary and mixed regimes of lubrication

Machine downsizing, increased loading and better sealing performance have progressively led to thinner lubricant films and an increased chance of direct surface interaction. Consequently, mixed and boundary regimes of lubrication are prevalent with ubiquitous asperity interactions, leading to increased parasitic losses and poor energy inefficiency. Surface topography has become an important consideration as it influences the prevailing regime of lubrication. As a result a plethora of machining processes and surface finishing techniques have emerged. The stochastic nature of the resulting topography determines the separation at which asperity interactions are initiated and ultimately affect the conjunctional load carrying capacity and operational efficiency. The paper presents a procedure for modelling of asperity interactions of real rough surfaces, from measured data, which do not conform to the usually assumed Gaussian distributions. The model is validated experimentally using a bench top reciprocating sliding test rig. The method demonstrates accurate determination of the onset of mixed regime of lubrication. In this manner, realistic predictions are made for load carrying and frictional performance in real applications where commonly used Gaussian distributions can lead to anomalous predictions

Effect of cylinder deactivation on tribological performance of piston compression ring and connecting rod bearing

Thermo-mixed-hydrodynamics of compression rings and big-end bearings are presented. Frictional losses under normal engine operating conditions for a gasoline engine and those with cylinder deactivation (CDA) are predicted. With CDA, the combustion chamber pressure increases in the active cylinders, whilst some residual pressure remains in the deactivated ones. For the former, the increased in-cylinder temperatures reduce viscous friction, whilst reducing the load carrying capacity, promoting increased boundary interactions. In deactivated cylinders, lower contact temperatures yield increased viscous friction. Overall, a 5% improvement in expended fuel is expected with the application of CDA. However, 10% of these gains are expended due to increased friction. The study demonstrates the need to consider total system effects when introducing new technologies such as CDA

Thermo-Mixed Hydrodynamics of Piston Compression Ring Conjunction

The final publication is available at http://link.springer.com.A new method, comprising Navier-Stokes equations, Rayleigh-Plesset volume fraction equation, an analytical control-volume thermal mixed approach and asperity interactions is reported. The method is employed for prediction of lubricant flow and assessment of friction in the compression ring-cylinder liner conjunction. The results are compared with Reynolds-based laminar flow with Elrod cavitation algorithm. Good conformance is observed for medium load intensity part of the engine cycle. At lighter loads and higher sliding velocity, the new method shows more complex fluid flow, possessing layered flow characteristics on account of pressure and temperature gradient into the depth of the lubricant film, which leads to a cavitation region with vapour content at varied volume fractions. Predictions also conform well to experimental measurements reported by other authors