7 research outputs found

    Thermo-mixed hydrodynamics of piston compression ring conjunction

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    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

    Glass capillary microfluidics for production of monodispersed poly (dl-lactic acid) and polycaprolactone microparticles: experiments and numerical simulations

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    Hypothesis: Droplet size in microfluidic devices is affected by wettability of the microfluidic channels. Three-dimensional countercurrent flow focusing using assemblies of chemically inert glass capillaries is expected to minimize wetting of the channel walls by the organic solvent. Experiments: Monodispersed polycaprolactone and poly(lactic acid) particles with a diameter of 18-150 μm were produced by evaporation of solvent (dichloromethane or 1:2 mixture of chloroform and toluene) from oil-in-water or water-in-oil-in-water emulsions produced in three-dimensional flow focusing glass capillary devices. The drop generation behaviour was simulated numerically using the volume of fluid method. Findings: The numerical results showed good agreement with high-speed video recordings. Monodispersed droplets were produced in the dripping regime when the ratio of the continuous phase flow rate to dispersed phase flow rate was 5-20 and the Weber number of the dispersed phase was less than 0.01. The porosity of polycaprolactone particles increased from 8 to 62% when 30 wt% of the water phase was incorporated in the organic phase prior to emulsification. The inner water phase was loaded with 0.156 wt% lidocaine hydrochloride to achieve a sustained drug release. 26 % of lidocaine was released after 1 h and more than 93 % of the drug was released after 130 h

    Glass capillary microfluidics for production of monodispersed poly (dl-lactic acid) and polycaprolactone microparticles: experiments and numerical simulations

    Get PDF
    Hypothesis: Droplet size in microfluidic devices is affected by wettability of the microfluidic channels. Three-dimensional countercurrent flow focusing using assemblies of chemically inert glass capillaries is expected to minimize wetting of the channel walls by the organic solvent. Experiments: Monodispersed polycaprolactone and poly(lactic acid) particles with a diameter of 18-150 μm were produced by evaporation of solvent (dichloromethane or 1:2 mixture of chloroform and toluene) from oil-in-water or water-in-oil-in-water emulsions produced in three-dimensional flow focusing glass capillary devices. The drop generation behaviour was simulated numerically using the volume of fluid method. Findings: The numerical results showed good agreement with high-speed video recordings. Monodispersed droplets were produced in the dripping regime when the ratio of the continuous phase flow rate to dispersed phase flow rate was 5-20 and the Weber number of the dispersed phase was less than 0.01. The porosity of polycaprolactone particles increased from 8 to 62% when 30 wt% of the water phase was incorporated in the organic phase prior to emulsification. The inner water phase was loaded with 0.156 wt% lidocaine hydrochloride to achieve a sustained drug release. 26 % of lidocaine was released after 1 h and more than 93 % of the drug was released after 130 h

    Cavitating flow in engine piston ring-cylinder liner conjunction

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    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

    Tribology of dust-stop seals of mixing machines

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    Dust stop seals are widely used in powder and rubber mixing industries. Design of the sealing system requires a continuous supply of pressurised lubricant, which is not recycled because of the risk of contamination. There is also the potential of large volume leakage of oil due to poor sealing, increasing operational costs and necessitating remedial measures to avoid environmental protection. Furthermore, the seal faces are prone to failure in relatively short periods of time due to reduced gap and lubricant leakage. The paper presents an analytical method and numerical predictions based on Reynolds equation under combined hydrodynamic and hydrostatic conditions with the entrant lubricant through hydraulically loaded feedholes. The validity of these methods is ascertained through comparison with a more complex but time-consuming solution of Navier-Stokes equations. The numerical predictions allow for determining the prevailing tribological contact conditions and assessing its suitability for evaluating the sealing performance of mixing machinery.</p
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