Sun Youhong

Application and prospect of bionic non-smooth theory in drilling engineering

Abstract Bionics is a subject which can interact with many disciplines including the drilling engineering. On the basis of analyzing the properties of bionic non-smooth surface, the non-smooth theory is applied in the bit design to develop the bionic diamond bit. The dung beetle is selected as bionic prototype in this paper to design the working layer of an impregnated diamond bit, which makes the bottom surface always keep the same non-smooth shape and makes the bionic bit maintain a high penetration rate and long-life to underline their high efficiency, wear and resistance reduction properties. Tests show that the bionic bit improves the drilling speed and lifetime by 44% and 74%, respectively, compared with a common bit. In addition, the bionic non-smooth surface structure has an extensive application prospect in drilling engineering, due to its properties of wear, anti-sticking and resistance reduction. It can be applied to improve the wear performance of bit, pipe joint, cylinder liner and piston of mud pump, and to solve the bit balling and reduce the resistance of spiral drills and impact spearhead.

Rheological Behaviour and Compressive Strength of Cement Bentonite Grout Slurry

Grouting is a special technique generally applied in civil and geotechnical engineering works all over the world. Sustainable development of the grouting sector can be achieved by careful mixing and application of correct quantities of cement and bentonite compounds. In order to improve the efficiency of grout slurries, laboratory experiments were carried out to study the rheological behaviour and compressive strengths of cement–bentonite admixtures due to different volumes of water used in preparing the slurries. Moreover, the choice of grout slurries depends on the geotechnical characteristics of the geomaterial like voids, open cavities, fractures, particle sizes and fissures. This has led to the development of grouts with low water content, as well as the need to avoid problems of durability encountered due to high content of water or cement which would be necessary to reach the best economic solution. Therefore, water–cement–bentonite admixtures with correct ratios of grout materials are preferred over others due to its low production cost and efficiency.

Heat Transfer Model of Vertical Geothermal Heat Exchanger and Calculation Process

As a high efficiency, low consumption and clean energy, ground source heat pump technology has been paid more and more attention. To calculate heat transfer performance between geothermal heat exchanger and rock and soil, heat transfer model is introduced. Non-steady-state heat transfer model of Vertical geothermal heat exchanger pipe are analyzed and discussed. By using virtual heat source and the Green function method, analytical solution of non-steady-state temperature field is given. Through comparative analysis, simplified formula is given for engineering applications. Based on the above analysis, further discussion is made, that imbalance of hot and cold load throughout the year do long-term performance effect to the heat exchanger.