TRIBOLOGY OF HYDRAULIC SEALS FOR ALTERNATING MOTION

The present paper summarizes the friction properties of hydraulic piston and piston rod seals and the concerned calculation methods, based on test results published (in the literature) and on the own test results of the author. It includes the author's advanced friction force calculation method to estimate the expected friction force (loss) of different elastomeric and composite material seals. The major aim of this paper is to recommend an advanced calculation method, which is based on the diagrams obtained from the 'Friction characteristic tests.' The method is suitable to calculate the expected friction force at any working parameter within the parameter range of the tests

DESIGN DEVELOPMENT AND TRIBOLOGY OF RECIPROCATING HYDRAULIC SEALS

The development of reciprocating hydraulic seals is the simultaneous progress of seal designs and their tribo-mechanical system. The progress is resulted by the improvements in seal material characteristics, technology and design (cross section form, seal edge shape, friction surface quality, etc.), lubrication conditions, accuracy, reliability and life. Anyhow by time the increasing importance of environmental protection gave particular emphasis to leakage control. In these developing processes emphasized aims are to economize by reducing losses - both leakage and friction - and also reducing the required sealing space (housing volume), while adequate and reliable sealing life is obtained. The present paper provides contribution in revealing tribological - mostly friction - characteristics, design and efficiency of some characteristic reciprocating hydraulic seals

Tribology of elastomeric and composite reciprocating hydraulic seals

The present paper provides a short historical review on the attempts done to reveal the tribological behaviour of the reciprocating hydraulic seals. The discussed topics are regarding to the development trends in hydraulic piston and piston rod seals, the concerned tribological models, their utilizations and critical analysis. Furthermore it includes the evaluation of main operating characteristics - leakage and friction losses - and the (concerned) endurance tests and friction characteristics tests as well, based on the author`s research results

Thermal Efficiency Optimization for A Natural-Gas Power Plant

Energy production from fossil fuels has been regarded as the main source of the climate change. The reason for that is the oxidation of carbon in fossil fuels to carbon dioxide during combustion and the highest percentage of greenhouse gases in atmosphere belongs to carbon dioxide. Amongst the fossil fuels natural gas is preferred due to its low emission of greenhouse gases and having no particulate matter after combustion. While the other fossil fuels emit mainly carbon dioxide during the combustion process; natural gas emits mostly water together with carbon dioxide. Around 22 % of the world’s electricity is produced by natural gas and this share is expected to increase in near future. The power plants operating with natural gas as a gas cycle consisting of a compressor, a combustion chamber and gas turbine are combined with a vapor cycle in order to increase the efficiency. A heat recovery steam generator is used to reach this aim in recent years in generating steam by the heat received from the combustion gases leaving the gas turbine. It is very important to design and operate such energy conversion systems fired by natural gas in optimal conditions. If the efficiency can be increased, it can be said that the energetic, economic, and environmental aspects also improve. The modeling and optimization studies for a combined gas-vapor power plant are studied and the most important parameters which influence the efficiency are determined. The results indicate that the most effective parameters from the viewpoint of efficiency are air/fuel ratio, gas/steam ratio and the pressure ratios of the compressor and, thus, the gas turbine. The thermal efficiency increases by 18.25 % and, in the meantime, the exergy destroyed decreases by 9.84 % using optimum design parameters determined by the optimization algorithm proposed

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DEVELOPMENT OF PISTON SEALS FOR DEEP OIL-WELL PROBES FOR HIGH PRESSURE AND TEMPERATURE MEDIUM

In this paper the results of a finalized phase of the present test programme are published. It is considered only a stage (of the research work on dynamic seals for oil well probe application) when reasonable solutions were found. The results obtained are promising and already provide satisfactory solution for industrial problems. Compared to the requirements, the endurance test results proved much longer life at an acceptable friction loss. During the possible next phases of the test programmes more design alternatives, seal materials, friction surface materials and qualities should be subjected to endurance test in order to select the most suitable alternatives of the seals and also to optimize them. (Where optimizing the seals means: to obtain, or develop, the most reliable alternatives which produce the possible longest life, belonging to leak proof operation, and smallest friction loss at the operation parameters.) Friction characteristics tests should be carried out too for the selected design alternatives to obtain the required design aids for proper estimation of the expected friction forces at different working parameters

Heavy Metal Removal Investigation in Conventional Activated Sludge Systems

The combination of industrial and domestic wastewater in municipal WWTPs (waste water treatment plants) may be economically profitable, but it increases the difficulty of treatment, and also has some detrimental effects on the biomass and causes a low-quality final effluent. The present study evaluates the treatment process both in the presence and absence of heavy metals using ASM3 (activated sludge model no.3) so as to improve the model by means of incorporating other novel inhibitory kinetic and settler models. The results reveal that the presence of heavy metal, a case study for copper and cadmium at a concentration of 0.7 mgL−1 in a biological treatment system has a negative effect on heterotrophic bacteria concentration by 25.00 %, and 8.76 % respectively. Meanwhile, there are no important changes in COD (chemical oxygen demand), SS (total suspended solids) and TN (total nitrogen) in the final effluent in the conventional system. However, all these parameters are acceptable and consistent with EU Commission Directives. The results indicate that ASM3 can predict and provide an opportunity of the operation for an activated sludge wastewater treatment plant that receives the effluent from an industrial plant

DEVELOPMENT OF PISTON SEALS FOR DEEP OIL-WELL PROBES FOR HIGH PRESSURE AND TEMPERATURE MEDIUM

In this paper the results of a finalized phase of the present test programme are published. It is considered only a stage (of the research work on dynamic seals for oil well probe application) when reasonable solutions were found. The results obtained are promising and already provide satisfactory solution for industrial problems. Compared to the requirements, the endurance test results proved much longer life at an acceptable friction loss. During the possible next phases of the test programmes more design alternatives, seal materials, friction surface materials and qualities should be subjected to endurance test in order to select the most suitable alternatives of the seals and also to optimize them. (Where optimizing the seals means: to obtain, or develop, the most reliable alternatives which produce the possible longest life, belonging to leak proof operation, and smallest friction loss at the operation parameters.) Friction characteristics tests should be carried out too for the selected design alternatives to obtain the required design aids for proper estimation of the expected friction forces at different working parameters

A dynamic model and performance analysis of a stepped rotary flow control valve

The hydraulic independent metering (IM) is an advanced actuator driving technique that allows the implementation of advanced control algorithms or methods. The main concept of IM is to control hydraulic actuators ports, which are the meterin and meter-out, separately. In this paper, a novel stepped rotary type valve has been developed for embedding in hydraulic independent metering systems, instead of conventional types such as poppet and spool. The insertion leads to developing different and novel control techniques, which require a software in loop and hardware in loop simulation of the proposed system. The paper explores the dynamic representation of this valve and defines its own performance limitations. This includes the development of a linear model comprising its two main sub-parts which are the stepper motor and the rotary orifice. Consequently, the linear timeinvariant methods are used to explore the performance of the valve by considering the effect of different parameters namely the pressure drop, friction coefficient, damping coefficient and bristle coefficient