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Feed-water valves are widely used in nuclear power plants to regulate the flow rate of the water supplying to steam generators, and thus holding the water level in steam generators at desired values. The flow rate characteristics of feed-water valves have important effects on the management quality of the water level in steam generators and therefore influence the safety and the efficiency of nuclear power plants. In this paper, the effects of throttling window shapes on the flow rate characteristics through feed-water valves are investigated in two aspects, the overall performances and the fluid dynamics. First of all, a dimensionless parameter defining throttling window shapes is proposed for the quantitative assessment. Then, for the analysis of overall performances, the rated flow coefficient, the loss coefficient, and the inherent valve characteristics are investigated. A revised fitting function is obtained to predict the inherent valve characteristics with different throttling window shapes for engineering applications. Finally, for the observation of the fluid dynamics, the velocity characteristics and the pressure characteristics are both discussed. The wear conditions are predicted at different relative travels and throttling window shapes. This paper provides a reference for researchers dealing with the design work of feed-water valves and is beneficial for the improvement of the whole water level control system. [ABSTRACT FROM AUTHOR]

The final quality of tissue paper depends on the parameters of the continuous transformation process and maintenance of rolls of a tissue paper machine. For a better quality, outer surfaces of the rolls must always be clean, and their roughness should be maintained in the same way. A Doctor Blade provides for such requirements. Our work is focused on the development of a pneumatic oscillator that moves a Doctor Blade in order to scrape the outer surfaces of the rolls. It is based on a low-friction double-effect cylinder with a through-rod. The integration of two limit switch valves, one for each head of the cylinder, and a smart pneumatic circuit to obtain a very low speed of the piston at constant load, represents the novelty of the proposed device. The piston of the cylinder allows for alternatively switching the limit switches that command the 5/2 air-operated pilot valve of the cylinder. The oscillator’s design, pneumatic circuit, and working principle are detailed. Experimental tests on the conceived limit switch and on the first prototype of the pneumatic oscillator validated the effectiveness of the proposed solution, the technical feasibility of the device, and the absence of stick-slip during the oscillatory motion at low speed.

The article presents a promising non-contact face seal of the rotor of a dynamic machine. The principle of pulse balancing of the movable sealing ring is applied in the seal design. The design of the test equipment and seal samples, which were used to conduct comprehensive investigations of the seal in the operating range of speeds and pressures, are considerated. The analysis of the experimentally obtained data of the barrier gas flow rate parameters and pressure changes in the working gap of the seal is carried out. A comparison of the traditional physical model of the working process of leaking pulse seals with the results of the research is performed. Identified and analyzed the fundamental differences of working processes of the traditional leaking and considered non-leaking pulse seals. A model of the physical process is developed and recommendations for the creation of a mathematical model of the gas barrier pulse seal are formulated. [ABSTRACT FROM AUTHOR]

This paper deals with the effect of ecological energy carrier on flow characteristics of a hydraulic pump. A hydraulic oil MOL Farm UTTO Synt was used as an ecological energy carrier. After completing 900 engine hours, the flow efficiency of the hydraulic pump decreased by Δηpr = 1.197 %. Oil samples were taken from the agricultural tractor Zetor Forterra 114 41. These samples were subjected to an IR spectroscopy analysis in an accredited laboratory WearCheck, Hungary. The following oil properties were examined: kinematic viscosity at 40 °C, viscosity index, silicium and ferrum content.

Many industries require contactless transport of delicate or clean products such as silicon wafers, flat foodstuffs and freshly painted objects. In this study, a contactless air film conveyor for flat objects is introduced. The object is supported by a thin film formed between the object and the conveyor surface and transported by viscous traction which is generated by controlled airflow underneath the object. Experimental and theoretical investigations are conducted on the basic characteristics (flow rate characteristics, film pressure distribution and viscous force). A theoretical model based on Reynolds equation coupling with incompressible Navier–Stokes equation is established to help analyze and understand these characteristics. The results show that air film pressure is symmetrically distributed along the direction perpendicular to the airflow in the actuating cells and non-symmetrically distributed along the airflow direction. The viscous force obtained by differentiating the pressure distribution implies that it consists of an actuating force produced by airflow in the pockets and a drag force resulted from airflow across the dam area. In addition, the influences on the viscous force from gap thickness, suction flow rate, inner bulge and depth of the pocket are discussed. [ABSTRACT FROM AUTHOR]

Both the mass flow rate and heat transfer characteristics are significant factors to the flow behavior of the high-pressure air; however, they are not easy to be obtained by analytical model during discharge and charge processes. In this paper, the mass flow rate characteristics of high-pressure pneumatic components (HPPC) are measured by a compounding approach; two components under test with the same geometry and dimension are needed to be connected in series. Both the effective cross-section area and critical pressure ratio of HPPC are determined accurately, and only the pressure variation and the steady-state temperature of air in the chamber are utilized. The compared results between experimental and simulation data show that the accuracy of the measured effective cross-section area and critical pressure ratio of the HPPC is high when the sonic and adiabatic releasing time is less than 2 s. And then, a new combined method of calculating the heat transfer coefficient during discharging and charging processes for the high-pressure air is proposed. The computational fluid dynamics (CFD) method is used to illustrate the intensity of heat exchange between the high-pressure air inside the chamber and outer atmosphere. The dynamic flow behavior is analyzed based on the tested flow rate characteristics of HPPC, mixed heat transfer theory and numerical results. The results show that the heat-transfer coefficient during charge process is much greater than discharge process, and the forced convection heat exchange happened owing to the strong “air agitation” during the charge process. The experimental results also validate that the proposed method of calculating the transient heat transfer coefficient is more reasonable to describe the heat transfer behavior. The findings may also have general implication in the development of the design and analysis of the high-pressure pneumatic system. [ABSTRACT FROM AUTHOR]

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Abstract: The thesis of this study is to investigate that the measurement accuracy of the isothermal discharge method for hydrogen gas with an isothermal tank which is designed for measuring the flow rate characteristics of pneumatic components. Compressed hydrogen in an isothermal tank, which is combined three types of orifice, is discharged from 700 kPa (abs) to atmospheric pressure. The average temperature in the tank during discharge is measured experimentally. In consequence, when the maximum discharge rate is 37 kPa/s during discharge hydrogen, the measurement error is less than 3% in whole discharge time. The temperature response phenomenon in hydrogen is discussed qualitatively in the view point of the internal energy change. The internal energy change immediately after the discharge started was negative because the release enthalpy was larger than the quantity of heat obtained from the stuffing material. After a certain period of time elapsed, the enthalpy change became equal to the heat exchange between the internal hydrogen and the stuffing material. [Copyright &y& Elsevier]

Abstract: To improve the measurement precision of flow rate characteristics of pneumatic components, a new measurement method is proposed, which is based on the dynamic regularity of instantaneous polytropic exponents during discharge. The dynamic regularity of polytropic exponents is obtained by the stop method, and it can be concluded as two change stages based on pressure time constant. According to piecewise polynomial fitting curves of instantaneous polytropic exponents, a new algorithm for the identification of flow rate characteristics is proposed. This method can accurately measure some components with a large sonic conductance and a small critical pressure ratio. Four pneumatic components are measured to compare the identification precision of those different methods. The results of comparison show that the new polytropic exponent method and its new algorithm have the higher precision than other alternative methods for the ISO6358 method. The identification errors of sonic conductance of the new method are less than 3%, and the identification errors of critical pressure ratio of the new algorithm are less than 15%. [Copyright &y& Elsevier]

Abstract: When flowing through porous media, it is generally known that Darcy regime and Forchheimer regime respectively provide a good approximate characterization in different velocity regions. In this study, a charge method employing an isothermal chamber and a pressure differentiator to determine the permeability coefficient and inertia coefficient is proposed, and its validity is verified by using a series of metal sintered porous media to conduct investigations on flow rate characteristics. The charge method has advantages over the conventional steady state method for it takes only seconds to finish the test and consumes less air. Results of the charge process are separated into a strict Darcy region and a quasi-Forchheimer region, with the flow velocity of 0.1 m/s as the boundary. Experimental data are first used to determine the permeability coefficient in Darcy region, and then the inertia coefficient in Forchheimer region. The permeability coefficient is measured within a 3% uncertainty. Also, it is confirmed that the calculated flow rate show good agreement with the experimental data. Finally, a principle, of general application, for selecting a chamber volume to ensure adequate accuracy of the acquired data is provided. [Copyright &y& Elsevier]

In this paper, a new isothermal tank test circuit composed of two tanks and a new data-processing algorithm called Cbm method are proposed to measure the flow-rate characteristics of some pneumatic valves. The double-tank circuit is used to test some solenoid valves such as inner pilot solenoid, which the traditional isothermal discharge method can not apply to. And Cbm method changes the identification procedure of multivariable unconstrained optimal algorithm, which evidently improves the identification precision of critical pressure ratio and subsonic index. [ABSTRACT FROM AUTHOR]

The final quality of tissue paper depends on the parameters of the continuous transformation process and maintenance of rolls of a tissue paper machine. For a better quality, outer surfaces of the rolls must always be clean, and their roughness should be maintained in the same way. A Doctor Blade provides for such requirements. Our work is focused on the development of a pneumatic oscillator that moves a Doctor Blade in order to scrape the outer surfaces of the rolls. It is based on a low-friction double-effect cylinder with a through-rod. The integration of two limit switch valves, one for each head of the cylinder, and a smart pneumatic circuit to obtain a very low speed of the piston at constant load, represents the novelty of the proposed device. The piston of the cylinder allows for alternatively switching the limit switches that command the 5/2 air-operated pilot valve of the cylinder. The oscillator's design, pneumatic circuit, and working principle are detailed. Experimental tests on the conceived limit switch and on the first prototype of the pneumatic oscillator validated the effectiveness of the proposed solution, the technical feasibility of the device, and the absence of stick-slip during the oscillatory motion at low speed. [ABSTRACT FROM AUTHOR]

Isothermal chamber is a new kind of measuring installment used to test pneumatic component flow rate characteristics. Building the mathematic model of isothermal chamber is important to predict the performance of isothermal chamber and manufacture it properly. Two mathematics models were established based on the lumped parameter and the dimension analysis theory separately. The test result proves that the model based on the dimension analysis theory can better predict the characteristics of temperature variety of isothermal chamber during the discharging period than that based on the lumped parameter and is more simply and easy to use in engineering applications. The model will provide theoretical principle for the rationalization design of isothermal chamber. [ABSTRACT FROM AUTHOR]