EVALUATION OF NONDESTRUCTIVE TESTING RESULTS

The issues of assessing the volume and efficiency of non–destructive testing in order to improve the quality and completeness of information for determining the degradation processes that cause the destruction of technical devices, for automating data processing, for determining time, labor and cost, taking into account the volume, efficiency and labor intensity.

Influences of eccentricity ratio on the internal flow and cavitation characteristics of progressing cavity pump

A Progressing Cavity Pump (PCP) works by forming a progressive seal cavity through the eccentric rotation of rotor. PCP parameters, such as eccentricity ratio [Formula: see text], can influence its performance and cavitation characteristics. The internal correlation among clearance fluid, cavitation characteristics, and pump performance should be explored to reveal the variation laws of internal flow and cavitation characteristics in PCP under different [Formula: see text]. In this study, a contrast analysis on external characteristics (e.g. volume efficiency) of pump with different eccentricity ratios was carried out by combining an RNG [Formula: see text] turbulence model based on Singhal full-cavitation model and the model pump test method. Moreover, gas volume distribution of PCP was analyzed and the optimal value range of eccentricity ratio was proposed. Results demonstrate that the axial force and axial power of PCP basically remain the same, volume efficiency increases, and cavitation performance decreases with the increase of [Formula: see text], and the optimal value for [Formula: see text] ranges from 0.17 to 0.24. In addition, a revised NPSHQ is proposed to quantify the cavitation characteristics of PCP.

Improving Output Performance of a Resonant Piezoelectric Pump by Adding Proof Masses to a U-Shaped Piezoelectric Resonator

This study proposes the improvement of the output performance of a resonant piezoelectric pump by adding proof masses to the free ends of the prongs of a U-shaped piezoelectric resonator. Simulation analyses show that the out-of-phase resonant frequency of the developed resonator can be tuned more efficiently within a more compact structure to the optimal operating frequency of the check valves by adjusting the thickness of the proof masses, which ensures that both the resonator and the check valves can operate at the best condition in a piezoelectric pump. A separable prototype piezoelectric pump composed of the proposed resonator and two diaphragm pumps was designed and fabricated with outline dimensions of 30 mm × 37 mm × 54 mm. Experimental results demonstrate remarkable improvements in the output performance and working efficiency of the piezoelectric pump. With the working fluid of liquid water and under a sinusoidal driving voltage of 298.5 Vpp, the miniature pump can achieve the maximum flow rate of 2258.9 mL/min with the highest volume efficiency of 77.1% and power consumption of 2.12 W under zero backpressure at 311/312 Hz, and the highest backpressure of 157.3 kPa under zero flow rate at 383 Hz.

Research of transverse dynamic oscillation for the piston in labyrinth compressor

In labyrinth compressor, non-contact labyrinth sealing clearance was designed between piston and cylinder wall to process oil-free gas containing fine particles. To prevent the collision between piston and cylinder wall, this labyrinth clearance was usually set bigger than 2‰ of the piston diameter. Such a big clearance seriously increased the leakage rate and reduced the volume efficiency of the compressor. Thus, it was necessary to investigate the piston transverse oscillation, and find a way to minimize the oscillation amplitude to reduce the labyrinth clearance set. In this paper, a dynamic model was established to predict the piston transverse oscillation based on inertia mass vibration analysis and finite difference method. Experiments investigation of the piston transverse oscillation track showed high prediction accuracy of the proposed model. Then, structure parameters optimization of the compressor was carried out to reduce piston oscillation amplitude. It was found that ratio of the crank shaft radius to connecting rod length and the position of the guide bearing were two key parameters determining the oscillation amplitude. Finally, a case study showed that the oscillation amplitude could be reduced by 53% by adopting optimized parameters.

Numeric simulation of the pulsation bottle for a reciprocating compressor in dynamic regime

The pulsation bottles are mounted at the inlet and outlet of / from the reciprocating compressor cylinders to even out the gas parameters (pressure and temperature). They ensure stable working conditions in the compressor cylinders and eliminate / reduce vibrations. The sizing of the pulsation bottle is done based on the geometric parameters of the compressor, the volume efficiency and working pressure. The use of a dynamic model made in the LMS Amesim program allows the study of a compressor with a set of pulsation bottles at the modification of: the pressure and temperature at the inlet / outlet of the compressor, the speed of the compressor the volume of the dead space and blocking or removing of the valves. The model includes the compressor cylinder with the corresponding dead spaces, the compressor valves, the suction and discharge pipelines and crank connecting rod mechanism. The simulation takes into account of the: gas composition, temperature and pressure in the system. The variation of the pressure in the bottles can be checked under these conditions. The values of the disturbing forces for a range of working and adjustment parameters can be obtained, values that can be used in a dynamic analysis according to API 618.

Experimental and Numerical Study on the Formation Mechanism of Flow Field in a Side-Ported Rotary Engine Considering Apex Seal Leakage

The aim of this research is to investigate the influences of apex seal leakage on the formation mechanism of flow field in a side-ported rotary engine by particle image velocimetry (PIV) and computational fluid dynamics (CFD). In this study, a PIV was used to acquire the two-dimensional (2D) flow field on the rotor housing central plane at an engine speed of 700 rpm. A three-dimensional (3D) dynamic simulation model considering leakage through apex seals was established and verified by the 2D-PIV experiment results. Thereafter, CFD analysis was used to further understand the 3D flow field in combustion chamber under the action of apex seal leakage. The simulation results showed that for the three engine speeds (2000, 3500, and 5000 rpm), in the intake stroke, the vortex generated in the front end of combustion chamber under the condition with no leakage, was strengthened and destroyed by the effects of the small (0.02 mm) and the large (0.08 mm) apex seal leakage gaps, respectively. As the apex seal leakage gap increased, the volume efficiency and the peak pressure decreased continuously. The volume efficiency and the peak pressure caused by any fixed apex seal leakage gap decreased with the increase of the engine speed. Compared with the volumetric efficiency of the condition with no leakage at 2000 and 5000 rpm, the volumetric efficiency of apex seal leakage gap of 0.08 mm decreased only by 24.6% at 5000 rpm, but by 41.2% at 2000 rpm.

Leakage and Volumetric Efficiency Analysis and Seal Improvement of Internal Gear Pump with Multi Output

Based on the analysis of the structural characteristics of the internal meshing gear pump with multi-output, the main leakage ways in the gear pump are summarized. By establishing the mathematical formula of leakage, the general formula of the total leakage of the gear pump under three working modes is obtained, and the volume efficiency of the pump is calculated. It is concluded that the volume efficiency of the internal meshing gear pump with multi output is the highest when the internal pump is used alone, and the volume efficiency of the external pump alone is the lowest. The structure of internal gear pump with multi output is improved to reduce the leakage and is verified via experiments. The experimental results show that the volumetric efficiency of the pump is consistent with the analysis results, that is, the volume efficiency decreases with the increasing of load pressure of pump.

Investigation of the Pastes for Multilayer Ceramic Capacitors Termination

Multilayer ceramic capacitors (MLCC) have wide application in electronic due to its electrical characteristics: low equivalent series resistance (ESR) and high volume efficiency. One of the MLCC manufacturing problems is the choice of composition for the end pastes. The experimental results of the termination pastes composition influence on the quality high-voltage MLCC investigation are presented. The causes of the defects appearance in the termination are determined, the composition of the termination paste, which ensures the quality contact of the internal electrode with the external, is proposed.

Temporal-dependent effects of rainfall characteristics on inter-/intra-event stemflow variability in two xerophytic shrubs

Stemflow is important for recharging root-zone soil moisture in arid regions. Previous studies have generally focused on stemflow volume, efficiency and influential factors but have failed to depict temporal stemflow processes and quantify their relationships with rainfall characteristics within events, particularly for xerophytic shrubs. Here, we measured the stemflow volume, intensity, duration and time lags to rain events of two xerophytic shrub species (Caragana korshinskii and Salix psammophila) and rainfall characteristics for 54 events in the Liudaogou catchment of the Loess Plateau, China, during the 2014-2015 rainy seasons. The results indicated that stemflow dynamics were well synchronized to rainfall processes. The stemflows of C. korshinskii and S. psammophila had larger average intensities (4.7 ± 1.5 and 4.8 ± 1.6 mm h−1, respectively) than that of rain at the event scale (4.5 ± 1.0 mm h−1), and the stemflows were even more intense (20.3 ± 10.4 and 16.9 ± 8.8 mm h−1, respectively) than that of rain at 10-min intervals (10.9 ± 2.1 mm h−1). The average stemflow durations of C. korshinskii and S. psammophila (3.8 ± 0.8 and 3.4 ± 0.9 h, respectively) were shorter than the rainfall duration (4.7 ± 0.8 h). Tested by a multiple correspondence analysis and stepwise regression, rainfall amount and duration controlled stemflow volume and duration, respectively, at the event scale by linear relationships (p

Study on the Intake Valve Close Timing Misalignment Between the Maximum Volume Efficiency and the None Backflow on a Single Cylinder Diesel Engine

Since the intake valve close timing (IVC) directly determines the amount of displacement backflow and the amount of fresh charge trapped in the cylinder, optimizing the IVC is important to improve the performance of the diesel engine. In this paper, the relationship between the IVC and the displacement backflow of the cylinder at the high-speed condition was studied by establishing a one-dimensional (1D) gas dynamic model of a single-cylinder diesel engine. The results show that the forward airflow mass of intake and the backflow increase as the IVC retards, and the airflow mass trapped in cylinder increases at first and then decreases. It is interesting to find that the backflow does not equal zero when the air mass trapped in cylinder is the largest, which is different from the traditional optimizing strategy on the IVC. That is to say, there exists a misalignment between the maximum-volume-efficiency IVC and the none-backflow IVC. To further verify this interesting misalignment, the airflow characteristics at the optimized IVC condition are studied by establishing a three-dimensional (3D) simulation. It is found that the appearance of backflow is a gradual process, and there exists an overall backflow when the engine volume efficiency reaches its maximum value. In addition, the misalignment is reduced as the mean valve-closing velocity increases. The misalignment equals to 0 only if the mean valve-closing velocity approaches infinity.