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A Quick-and-Dirty Method for assessing the Risk of Negative Aeration Effects of Shock Absorbers equipped with Shim Sliding Base Valves

Czop Piotr, Gniłka Jacek

Computer Assisted Methods in Engineering and Science

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2022

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Vol. 29, no. 3

229--260

EN

This paper presents a quick-and-dirty method to assess the risk of negative aeration effects occurring in twin-tube hydraulic shock absorbers used in passenger cars at the early design stage. The method is intended to be implemented as an engineering calculation tool based on the computational fluid dynamics (CFD) two-dimensional (2D)/three-dimensional (3D) steady-state single-phase model. The CFD model was previously validated with the use of the particle image velocimetry (PIV) experiment. The negative aeration effect is a wellknown issue for automotive and railway shock absorbers manufacturers. It results in uncontrolled on-vehicle vibrations and the deteriorated shock absorber damping characteristic. The major aeration contributor in twin-tube hydraulic shock absorbers is the sliding shim intake valve, which requires design optimization to avoid a negative aeration effect. The method validation was conducted with the customized test rig equipped with a transparent cylinder where the specific sliding intake valve was assembled. The proposed method also requires a lumped-parameter model of a twin-tube shock absorber, which allows to simulate boundary conditions in assessing particular reservoirs of a shock absorber, i.e., pressures and flow balance. The method is implemented as a calculation routine that converts CFD pressure regions into a gas concentration indicator (GCI) using the pressure-density characteristic of an oil-gas emulsion of a shock absorber. GCI is calculated based on the sum of particular 2D/3D grid elements. The method application is to minimize the risk of occurrence of negative aeration effects by avoiding expensive and time-consuming experimental tests. This method can also be used for in-production shock absorbers projects as a part of a continuous improvement cycle or in the case of inefficient shock absorbers claimed by a vehicle manufacturer. The application scope of the method can be extended for arbitrary twin-tube designs of shock absorbers in the automotive and railway industries.

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A performance study on partial replacement of polymer industries waste (PIW) as fine aggregate in concrete

Srinivasan K., Premalatha J., Srigeethaa S.

Archives of Civil Engineering

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2018

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Vol. 64, nr 3

45--56

EN

Recycling of plastic wastes helps in reducing waste disposal problems and helps for the sustainable development of the country. Concrete with various % (0 to 55%) of waste plastic aggregates were tested for their mechanical strength properties. In the present work, plastic aggregates obtained as end product of a polymer recycle industry in the form of grains called as plastic aggregates are used as fine aggregate replacements in concrete. The addition of plastic aggregate as fine aggregate replacements results in increase in compressive strength, split tensile strength and flexural strength and thus helps in production of sustainable concrete. It is observed that, the optimum % of replacement of sand with waste plastic waste is 40% and it is also found that upto55% of sand replacements with plastic wastes, mechanical strength values are comparable with that of the normal concrete.

3

Analysis of air flow velocity distribution in the intake system of an SI engine

Kołodziej S., Ligus G., Mamala J., Augustynowicz A.

Combustion Engines

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2017

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R. 56, nr 2

152--157

EN

The conditions of air flow in the intake determine power generated by the engine to a large extent. The biggest resistances in flow of the air sucked or pumped into the engine are generated by the throttle, which is at the same time the main component which allows for regulation of engine power. For the purpose of research conducted in this work, time density of engine work points in analyzed velocity profiles was determined with the use of Engine Road Load Simulator. Thanks to the knowledge of time velocity, it was possible to determine throttle positions at which the engine operates most frequently. With the use of image analysis methods, obtained parameters were experimentally researched, considering flow disturbances which are the effect of air flow through the throttle and uneven air distribution in the intake manifold of a four-cylinder engine.