Applied Mechanics and Materials Vol. 492

Abstract: Three-dimensional thermoelastic analysis on the fir-tree root and rim of the I-P cylinder’s first stage blade was performed in two cases of load condition: only centrifugal force and both centrifugal force and temperature load, and five different manufacturing variations were taken into account. The results show that: with high temperature, the stress level of root which is well-designed under room temperature increase obviously, and the load of the four root teeth is unevenly distributed. Moreover, manufacturing variation between contact surfaces lead to serious stress concentration and extremely high stress, and load distribution of the four root teeth is completely uneven. In addition, the influence of temperature on the stress distribution of blade root and rim is much different with different manufacturing variations.

Abstract: To study the cause for fatigue cracking failure at pressure-balanced holes of a gas turbine compressor sealing disk, the damage impression, fractography and material composition of the damaged section were studied. Some manufacturing defects at the pressure-balanced hole edge were found, and the cracks at pressure-balanced holes are caused by high cycle fatigue (HCF). Stress analysis on the sealing disks of two types of different materials under assembly conditions and different structure dimensions were performed. The analysis results revealed that the high radial stress of pressure-balanced holes is the weak point of the original sealing disk design, and the manufacturing defects will prompt the cracking failure of holes. The studied work is valuable for performing similar fatigue failure analysis and new sealing disk structure design improvement.

Abstract: In order to solve a kind of electric heating pipe electrode production and power adjustable, designed a kind of adjustable power of electric heating pipe electrode preparation equipment.The equipment is mainly used to test technology, PLC control technology and coating technology.First, selected on the basis of the PLC,the mechanism design, design the hardware control circuit, finally a port of the PLC wiring design.The results show that compared with the traditional production compared to heat pipe machine, the device not only high production efficiency and quality index, but also can produce many kinds of products[1].

Abstract: To systematically study the root cause of the fracture failure on a gas turbine LP(low pressure) second stage blade, the damage impression, fractography, material composition and metallurgical structure of the fractured section were studied. Vibration characteristic calcultaion analysis to the blade was performed under considering the working condition and structure characteristic. The analysis results revealed that the LP second stage Blade fracture is high cycled fracture (HCF), and mainly caused by furrowed manufacturing defects close to the fatigue source. Preventive measures were presented accordingly. The studied work is valuable for being a reference to fracture failure analysis and structure design for gas compressor blades.

Abstract: This paper mainly studies the effect of temperature cycling on stress relaxation behavior of contacts for electrical connectors. Based on the analysis of the test specifications of electrical connectors, this paper provides a kind of test method on stress relaxation behavior of electrical connector contacts under temperature cycling conditions. The detecting circuit is designed; the test is carried out and finally, according to the test data, it can be concluded that 1) for the same temperature change, the absolute change of strain within the temperatures above zero is bigger than that within the subzero temperatures; 2) the deformation of contacts gradually increases as the number of cycles increases. The length of the degradation process for electrical connectors might be related with the high temperature value, temperature variation or temperature variation rate.

Abstract: The complex magnetic flux density waveform of switched reluctance motor (SRM) leads to very difficult calculation of motor losses especially iron loss. In this paper, SRM’s losses are analyzed as the object of study, the working principle and base frequency of SRM are described, SRM’s losses are decomposed, and a detailed analysis of motor copper loss, mechanical loss and stray loss is proceeded. Iron loss especially under nonlinear magnetic flux waveform is studied, and calculation formulas and compensation coefficient of various losses are obtained at last.

Abstract: Wind turbine is complex multivariable nonlinear system with uncertainty and interference characteristics. For the wind turbine system, operation reliability, wind energy utilization efficiency and output power curves should be concerned. In this paper, the main characteristics of variable pitch wind turbine are analyzed in detail to obtain optimum wind energy utilization efficiency and power output.

Abstract: In the scenario of world energy crisis, building energy efficiency has become a mainstream research focus; since buildings take up a large share of the world energy consumption. Lighting plays an integral part in the buildings operationality through providing indoor visual comfort; and the much-needed daylight harnessing in building structures can be achieved through various strategies. This paper aims to evaluate the amount of plastic optical fiber (POF) required for achieving optimum indoor illumination through light transport and study the advantage of two dimensional solar tracking and light concentration on indoor daylight enhancement through POF as a trade-off for the amount of POF required in a static system. Illumination attained inside a representative closed chamber due to light transported by POF via various mechanisms was experimentally compared with outdoor direct illumination and the amount of POF required for achieving comfortable indoor illumination was calculated for a proposed system involving tracking and light concentration. A microcontroller based dual-axis solar tracker was designed for tracking sunlight on the POF collector node every 10 seconds and opaque internally reflective plastic containers acted like sample rooms in a building. Calculations for the representative day normalized for the flooring area in an office building showed a promising payback period of around 5 years through partial replacement of electric lighting. Additionally, reduction in heat conduction through window glazing further reduces the cooling costs.

Abstract: The design of blade of horizontal axis wind turbine (HAWT) has been conducted using model which developed based on blade element momentum theory. The performance of the turbine has been predicted using the same model. Moreover, the improvements of the model have been suggested. To accomplish the design and predict the performance of horizontal axis wind turbine, numerical code has been implemented; the performance of the turbine with and without improvements has been compared with published date. Based on the results presented more improvements have been suggested

Abstract: The paper presents a new Vertical Axis Wind Turbine (VAWT) design by using magnetic levitation (Maglev) and Permanent Magnet Synchronous Generator (PMSG). A lab prototype of VAWT was built which was run at low wind speed of around 3 to 5 meter per second. The bearing was replaced by Neodymium Magnet to avoid the friction which in turns reduces the losses and increase the efficiency. A Prototype version of PMSG was built which could generate voltage from the turbine even in low rotational speed. Suitable turbine blade angle was also determined using trial and error method.