Bo Qin Gu

Development of a New Kind of Sealing Composite Material Reinforced with Aramid and Pre-Oxidized Fibers

A new kind of sealing composite material reinforced mainly with aramid and pre-oxidized fibers were developed by molding preparation method. The effect of different surface treatment methods of the fibers on the heat resistance of the composite material was studied. The optimum prescription of the sealing composite material was obtained by regression design method. The relationship between the transverse tensile strength of the material after ageing at elevated temperatures and its main ingredients was investigated. The performances of the developed sealing composite material were tested, and the results indicate that the main performances of the material coincide with the requirements prescribed in Chinese national standard and some performances are even better than that of the products of some famous corporations.

Injection Molding Process Parameter Optimization for Warpage Minimization Based on Uniform Design of Experiment

To optimize injection molding warpage, this paper applies the uniform design of experiment method to search for the optimal injection molding processing parameters. The warpage. simulation analysis is accomplished by emplying Moldflow software. The melt temperature, mold temperature, injection time and packing pressure are regarded as processing parameters, and processing parameters are optimized through establishing a regression equation, and the optimization result and influence factors are analyzed. The results show that uniform design of experiment can reduce number of experiments used effectively and the quality of the product is greatly improved by the optimization method.

Research on Process Parameter Optimization of the High-Neck Flange Closed Rolling Based on the Orthogonal Experimental Design

This paper simulates the process of the high-neck flange closed rolling on DEFORM-3D and optimizes the rolling process parameter by analyzing the results based on the orthogonal experimental design. For the high-neck flange, the results show that the effects on ellipticity are in the order of the mandrel feed speed, the main roll rotational speed and initial blank temperature. The former two factors show the significance while the initial blank temperature does not show that.

Optimum Design of Flat End Face Mechanical Seal Based on Coupling Analysis

The flat end face mechanical seals are widely used in shaft sealing at moderate rotational speed. The thermal deformation of the rotating and stationary rings initiated by friction heat of fluid film should be primarily considered in the design of mechanical seal. In consideration of the coupling effect among the thermal deformation of sealing rings, the fluid flow in the gap composed by end faces of sealing rings and the heat transfer from fluid film to sealing rings, the optimum design method for flat end face mechanical seal is established. The end faces are fabricated to form a divergent gap at the inner side of the sealing rings, and a convergent gap will occur at the outer side and a parallel gap will be obtained at where the original divergent gap is due to the thermal deformation. After optimization, the leakage rate can be reduced while the bearing force of fluid film is still large enough to keep the fluid lubrication of the end faces.

Study on Time-Correlated Leakage Predication Model of Nonmetallic Gaskets

The time-correlated leakage characteristic of nonmetallic gaskets was analyzed. Considering the effect of the gasket material deterioration on the sealing performance, a time-correlated leakage predication model of nonmetallic gasket sealing connections based on the porous medium theory was proposed. Some tests were performed on compressed non-asbestos fiber gaskets, the leakage behavior was investigated and the coefficients in the leakage model were obtained by regression analysis of experimental data. The predicted leakage rates according to the model were compared with the data reported in some literatures, and the prediction accuracy was also validated. The presented time-correlated leakage model provides an effective way to predict the leakage rate and evaluating the life of gasket sealing connections.

Fractal Characterization of Sealing Surface Topography and Leakage Model of Metallic Gaskets

In this paper, the fractal characterization of the sealing surface topography of metallic gaskets was studied. The influence of the compressive stress on the fractal parameters was also investigated. It’s found that the sealing surface of metallic gaskets is fractal, and its topography can be characterized by the fractal dimension and the scale coefficient. The leakage model of metallic gaskets was established. The research results indicate that the larger the fractal dimension is, and the less the scale coefficient and the non-contact area are, the better the sealing performance of metallic gaskets is.

Numerical Simulation of Lubricant Liquid Film of the Laser Surface Textured Micro-Pore Face Mechanical Seal

The flow field characteristics of lubricant liquid film of the laser surface textured micro-pore face mechanical seal were studied by Fluent software, and the effects of geometric parameters of micro pores and operating parameters on the sealing performance were analyzed. The results show that the hydrodynamic effect of the laser surface textured micro-pore face mechanical seal is very obvious, and micro-pores make the friction state between rotating ring and stationary ring change to fluid friction. It can also be found that the rotating speed, the medium pressure, the area density and the liquid film thickness have effect on the sealing performance, among these influence factors, the area density has the greatest effect on the sealing performance, and it should be 0.2-0.3.

Internal Unsteady Flow Induced Vibration in Centrifugal Pump

Centrifugal pump is an important installation for fluid delivery. The research on the unsteady flow in centrifugal pump is very meaningful to reducing vibration. The methods of numerical simulation were discussed. The unsteady pressure field was simulated by using Sliding Mesh (SM) model provided by Fluent. The time domain data for pressure were obtained at the monitoring points, and they were translated to frequency domain data by using FFT. The results show that the static pressure at the impeller outlet increases along the direction of impeller rotation from the position near the volute tongue. The pressure disturbance is relatively large near the volute tongue. The pressure disturbance at the impeller inlet is smaller than that at the impeller outlet. The volute tongue plays a key role in the flow induced vibration. The position, where the blade is in closest proximity to the head of volute tongue, is the turning point in the pressure fluctuation cycle. The maximum peak value of pressure fluctuation appears at 145Hz, which is the blade frequency. Other pressure peaks are evident at multiples of the blade frequency. Also the pressure amplitude decreases with increasing frequency.

Fuzzy Comprehensive Evaluation Method for Mechanical Seal Risk Assessment of Centrifugal Pumps

A failure analysis of mechanical seals of centrifugal pumps was presented with fuzzy comprehensive evaluation method. Both failure probability and failure consequence were analyzed to evaluate the risk grade of the mechanical seals. The potential risk level of a mechanical seal was estimated by the application of risk matrix. The proposed fuzzy comprehensive evaluation method can be used to judge the reliability of mechanical seals and provide an important reference for the safe and stable operation of centrifugal pumps.

Optimization of Process Parameters for Warpage Minimization on Injection Molding Thin-Walled Parts

In this paper, Taguchi experimental design method is applied, and injection molding CAE simulation analysis is conducted. Influence factors of warpage of products are analyzed. According to the results of ranking, influence factors of warpag are the packing pressure, packing time, melt temperature and mold temperature. The packing pressure is the most important influence factor. To get the best level combination of various factors, mixed level orthogonal experimental design is applied to the optimization. Optimal levels of combination process parameters are obtained and the quality of injection products is greatly improved.