Gas Discharge Resistance and Medium Damage Degree as Hydrate Dissociation at Different Ambient Conditions

For the investigation on some hydrate dissociation behaviors at different ambient conditions, methane hydrates formed inside porous media with different saturations were dissociated by depressurizations. Plots of the instantaneous flow rate of gas as dissociation versus production pressure as well as deformation of experimental sample versus accumulative amount of released gas were drawn. These two lines slopes are, respectively, characterized as gas discharge resistance and reciprocal of the latter one as damage degree of experimental samples. The results show that these formed hydrates at higher ambient conditions, that is, temperature and pressure, and possess a higher saturation, which is beneficial to discharge gas and to keep experimental samples undamaged. And the nonuniformity of dissociation processes at different layer positions induced by depressurization is inhibited significantly, especially while combining extra heating. Hydrate saturation dominates the total volume loss of these samples under loadings. These conclusions can provide reference for the prediction in gas discharge capability and media damage degree as hydrate dissociation at different experimental and natural ambient conditions.

Simulation Research on Trapped Oil Pressure of Involute Internal Gear Pump

The main structure of an internal gear pump consisted of an internal gear pair, including an internal gear and an external gear. The internal gear pump had oil trapping phenomenon like other hydraulic gear pumps. In order to solve the oil trapping phenomenon of involute gear pump with internal meshing tooth profile, in this paper, the mathematical equation of gear outer contour is established according to the principle of generation method, and the variation law of the trapped oil area in meshing process is deduced by theoretical instantaneous flow rate obtained by scanning method. Then, the minimum trapped oil volume and unloading area are solved by the graphic method. Finally, based on fluid mechanics and dynamics, the trapped oil pressure model is obtained. The change of the trapped oil area and trapped oil pressure in a meshing cycle is simulated by MATLAB. The results show that the trapped oil area changes in a parabola, and the trapped pressure fluctuates in mountains and valleys. When the trapped area is the smallest, the trapped oil pressure reaches the peak at the corresponding corner. The research results can provide guidance for the development of high-performance internal gear pumps.

Principle and structure of a printed circuit board process–based piezoelectric microfluidic pump integrated into printed circuit board

Considering mature printed circuit board processes, researches on microfluidic pumps that can be integrated into printed circuit board will provide a solution for further miniaturization and integration of microfluidic systems with low costs. The principle and structure of a printed circuit board process–based piezoelectric microfluidic pump integrated into printed circuit board are proposed and realized in this article. The printed circuit board process–based design and manufacturing technology of a piezoelectric microfluidic pump integrated into printed circuit board is researched utilizing printed circuit board as a platform. The flow characteristics of the fabricated microfluidic pump are experimentally tested. The research results show that the proposed principle and structure of the piezoelectric microfluidic pump can be fabricated utilizing mature printed circuit board process with advantages of simple structure and convenient processing. The fabricated printed circuit board process–based microfluidic pump can linearly pump in and pump out fluid with self-injection. Moreover, the flow rate and back pressure can be controlled by changing the peak-to-peak value, frequency, and phase difference of the driving voltages. The instantaneous flow rate has the pulsation property consistent with the drive voltage frequency. The proposed principle and structure are beneficial to integrate the fabricated printed circuit board process–based microfluidic pump with other microfluidic components to realize complicated microfluidic systems on printed circuit board.

Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications

This paper describes a unique design concept that is capable of electronically controlling the flow delivered by an external gear pump (EGP). The principle used for varying the flow relies on the variable timing concept which has been previously demonstrated by the author's research team for EGP's operating at high pressures (HPs) (p > 100 bar). This principle permits to vary the flow within a certain range, without introducing additional sources of power loss. In this paper, the above concept has been applied to formulate a design for a variable delivery EGP for low pressure (LP) applications (p < 30 bar), suitable for direct electric actuation. Specific design principles for the gear and the flow variation mechanisms are introduced to limit the force required by the electric actuation, and for maximizing the flow variation range. Also, the low target pressure allows the variable timing principle to be realized with an asymmetric solution, with only one variable timing element present at one side of the gears. A detailed analysis concerning the relationship between the electrically commanded position of the flow varying element and the theoretical flow delivered by the pump is also presented. This analysis is used to formulate analytical expressions for the instantaneous flow rate and the flow nonuniformity of the pump. The paper details the design principle of the proposed variable flow pump and describes the multi-objective optimization approach used for sizing the gears and flow variation mechanism. The paper also discusses the experimental activity performed on a prototype of the proposed unit, able to achieve a flow variation of 31%.

Modelling and experimental studies on a proportional valve using an innovative dynamic flow-rate measurement in fluid power systems

A numerical model of a servoactuator and of a four-port proportional direction control valve has been developed. Mechanical and hydraulic elements have been simulated in the LMS Amesim® environment. The complete model has been validated on the basis of the experimental time histories of the actuator velocity and of the flow-rate controlled by the proportional valve. The validation data have been acquired on a fluid power system used to test electro-hydraulic servovalves according to ISO 10770-1 standard. The measurement of the instantaneous flow-rate through the valve has been performed with an innovative high-dynamics flowmeter, recently developed for high-pressure liquid flows. Furthermore, the model predicted static characteristic of the proportional valve has been compared with a corresponding experimentally derived curve and an analysis of the cause-and-effect relationships has been carried out for the valve static performance. Measured data on valve leakages have also been presented in order to complete the steady-state characterization of the tested valve. The developed model of the hydraulic system has been then applied to realize the Bode diagram of the proportional valve, which is expressed in terms of instantaneous flow-rate as a function of the sinusoidal driving command, as well as the Bode diagram of the subsystem made up of the proportional valve and of the linear actuator. The latter Bode graph is plotted in terms of piston velocity as a function of the sinusoidal driving command provided to the valve. The comparison between the two Bode diagrams has confirmed the accuracy of the ISO procedure, which is based on the assumption of negligible delay introduced by the dynamic response of the servo-actuator and by the oil compressibility. A reliable and cost-saving methodology, which uses the innovative flowmeter instead of the low inertia servo-actuator, is proposed as an alternative to the ISO standard for testing the dynamic response of proportional valves.

Design and experimental studies of a novel double-row radial piston pump

This paper proposed a novel double-row radial piston pump. In this pump, the transformation from the rotation of the shaft to the reciprocation of the piston is realized by a pentagon mechanism, and the oil is distributed by check valves, which are integrally designed on the pump body. Theoretical calculation demonstrated that this improved design can substantially reduce the force on the main shaft of pump. The formulas of instantaneous flow rate and fluctuation coefficient of the pump are deduced. For studying the working characteristics of the pump further, a prototype was manufactured and tested. Results show that when the rotation speed is over 125 r/min, the performances of pump prototype are qualified, the fluctuation rate is limited to 20% and the volumetric efficiency can reach 90%. Moreover, the pump was disassembled after 100 h of service and the wear condition was checked. Except for the pentagon which has indentation on the surface, the components of the pump are all kept intact.

Optimization of an Algorithm for the Measurement of Unsteady Flow-Rates in High-Pressure Pipelines and Application of a Newly Designed Flowmeter to Volumetric Pump Analysis

An innovative, efficient, and robust algorithm is presented for the evaluation of the instantaneous flow-rate in high-pressure liquid flow pipelines. This algorithm is based on the pressure time histories measured at two locations. A simple ordinary differential equation has been derived from the mass and momentum conservation laws and has been solved analytically. This equation allows the flow-rate time fluctuations to be evaluated accurately around their mean value, without any need for initial datum on the liquid flow velocity. A measuring device has been designed and realized to evaluate the flow-rate. The proposed flowmeter layout consists of a piece of pipeline endowed with two piezoresistive pressure sensors equipped with miniaturized thermocouples, the pressure sensor conditioners and a central processing unit (CPU), in which the algorithm for the evaluation of the flow-rate has been implemented. A more sophisticated version of the flowmeter algorithm, which includes unsteady friction in the flow-rate evaluation, has also been developed. Different algorithm versions have been assessed and successfully validated through a comparison with numerical flow-rate data predicted using a reliable one-dimensional model of a common rail (CR) fuel injection system. The prototypal flowmeter has been installed at the delivery section of a CR volumetric pump in order to investigate the flow-rate ripple. The flowmeter traces have been compared with the predictions of a previously developed theoretical model for the pump delivered instantaneous flow-rate, in order to further assess the reliability of both the model and the flowmeter as well as to have a better understanding of the cause and effect relationships between the flow-rate time history and the dynamic working of the pump. The effects that the actuation of the fuel metering valve (FMV), which is placed at the CR pump inlet, has on the instantaneous delivered flow-rate have also been analyzed.