The application of a transformational zone method to the calculation of radiation heat transfer inside a piston-cylinder system

A radiation heat transfer analysis has been formulated for the space inside an internal combustion engine cylinder using the principles of the Hottel zone and transformational zone methods. The space analyzed has a variable length resulting from the piston movement. The analysis presented here is for radiation in piston-cylinder systems of known temperatures of radiation gas, and internal surfaces of cylinder, head, and piston. Radiative emissions of the radiation gas in the shape of rings were determined on the basis of Stasiek's principle of surface transformation. The results obtained demonstrate the present approach satisfactorily, both qualitatively and quantitatively. Moreover, the division of the analyzed volume into infinitely small elements along the axial direction has significantly simplified the calculations in comparison with the conventionally employed classical Hottel zone method.     

A low-temperature high-pressure apparatus with a temperature control system

Abstract

A low-temperature high-pressure apparatus was designed using commercial cryogenic equipment. Pressures up to 1 GPa and temperatures down to 40 K can be obtained in a volume of up to 30 cm³. The apparatus is of the piston-cylinder type with a piston diameter of 45 mm, and the pressure can be varied at all temperatures, An adaptive temperature control system keeps the temperature inside the pressure cylinder constant to within ±0.1 K.     

高温下活塞-圆筒容器内叶腊石介质的对称与不对称摩擦损耗

 本文用测定铅的熔化曲线的方法来研究高温下活塞-圆筒容器中叶蜡石介质的摩擦损耗。发现叶蜡石在高温高压条件下，其不对称摩擦明显增高，因此不能应用常温下的压力定点方法标定压力。这些不对称摩擦很可能来源于叶蜡石在高温和常温状态下具有的较为悬殊的力学性能差别，从而导致了样品组装内部高温区与外层低温区之间负的差载效应。研究认为，叶蜡石具有价廉和易加工等优点，其摩擦在高温下也可大幅度下降。如果对由于压室温度不均匀而带来的不对称摩擦作适当修正，它仍然可以作为该类容器中高温高压物性测量的较为理想的传压介质。     

Elastic distortions in simple piston-cylinder units at pressures up to 100 MPa

Abstract

The study of elastic distortions in piston-cylinder units of primary standards piston gauges is of importance for the improvement of pressure measurement accuracy. Preliminary work (GF. Molinar et al., 1989) on distortion calculations was carried out on a tungsten carbide (t.c.) piston-cylinder of 0.2 cm² nominal effective area in the 100 MPa pressure range. The same calculations are now applied in the study of a similar piston-cylinder unit of hard steel (h.s.). The distortions on the outer surface of the cylinder are measured with strain gages and with a capacitance sensor. The calculated distortions, which can be also derived with other methods (G. Klingenberg 1989, R. Wisniewski et al. 1989), are compared with the experimental results obtained on the outer surface of the cylinder. The present two piston-cylinder units of h.s. and of t.c. were cross-floated up to 100 MPa and the ratio R = f(P) = Ae_h.s./Ae_t.c. obtained experimentally is compared with the calculated.     

Zr-based bulk metallic glass as a cylinder material for high pressure apparatuses

Zirconium-based bulk metallic glass (Zr-based BMG) has outstanding properties as a cylinder material for piston-cylinder high pressure apparatuses and is especially useful for neutron scattering. The piston-cylinder consisting of a Zr-based BMG cylinder with outer/inner diameters of 8.8/2.5?mm sustains pressures up to 1.81?GPa and ruptured at 2.0?GPa, with pressure values determined by the superconducting temperature of lead. The neutron attenuation of Zr-based BMG is similar to that of TiZr null-scattering alloy and more transparent than that of CuBe alloy. No contamination of sharp Bragg reflections is observed in the neutron diffraction pattern for Zr-based BMG. The magnetic susceptibility of Zr-based BMG is similar to that of CuBe alloy; this leads to a potential application for measurements of magnetic properties under pressure.     

双向活塞圆筒装置19 mm外径样品组装的压强和温度标定

在高温高压实验中,样品所处位置的压强、温度及样品腔温度分布情况对实验结果分析十分重要,因此使用高温高压实验装置前需对所用组装进行压强和温度标定。针对双向活塞圆筒装置19 mm外径样品组装,进行了压强与温度标定。利用氯化钠(NaCl)在高压下的熔化曲线对压强进行标定,当下油缸油压出现大幅度下降时,样品腔内的NaCl发生熔化,将此时热电偶测量的温度与文献报道的NaCl在高压下的熔化曲线进行比较,确定样品腔内的实际压强。压强标定结果显示,实际压强与目标压强满足线性关系。采用双热电偶法对19 mm外径样品组装样品腔的中部和上部进行测温,发现样品腔中心温度高于样品腔上部温度,温度梯度随温度升高而增大,随压强升高而减小。在二次加压升温时,样品腔内的温度梯度高于第一次加压升温实验测量结果。所得压强和温度标定结果对今后使用19 mm外径样品组装开展高温高压实验研究具有参考价值和指导意义。     

Small plastic piston-cylinder cell for pulsed magnetic field studies at cryogenic temperatures

A plastic piston-cylinder cell based on a thick wall test-tube has been designed for pulsed magnetic field studies. The small 12.7 mm diameter and overall height of 19.3 mm allow the cell to freely rotate in a cryostat with a diameter of 21.5 mm. Electrical leads, coax cable or microstrip transmission lines can be introduced into the pressure chamber for a variety of measurements such as electrical transport, de Haas–van Alphen, Shubnikov–de Haas and Hall effect. A fiber optic has been introduced for the purpose of calibrating the pressure via a ruby manometer. The fiber optic opens up additional experimental techniques such as photoluminescence, photoconductivity and, with use of a special fiber with a Bragg grating, magnetostriction and thermal expansion. Maximum pressures of 0.35 GPa at room temperature have been obtained.     

Crystallization of mesoporous silica SBA-15 in a high pressure hydrothermal environment

Mesoporous silica SBA-15 (with ～6?nm pore size and ～6?nm wall thickness) was exposed to a hydrothermal environment at 2 and 5?GPa. The p,T quenched products were investigated by powder X-ray diffraction and transmission electron microscopy. Infrared spectroscopy and thermogravimetric analysis of a sample subjected to 5?GPa at room temperature suggests functionalization of both inner and outer pore surface by silanol. Partial transformation to nano-sized (20–50?nm) coesite crystals with nonfaceted morphology was observed during short equilibration times of 2?h at 125°C, which is significantly below the melting point of water (～250°C). Untransformed SBA-15 maintained intact pore structure. At 175°C and during 8?h, SBA-15 transformed completely into faceted coesite crystals with dimensions 100–300?nm, suggesting Ostwald ripening and thus significant mass transport in the solid water environment. At 2?GPa the melting point of water is near 70°C. Partial transformation to nano-sized α-quartz was observed at 65°C and during 2?h. Untransformed SBA-15 partially pore collapsed. The reduced pore stability of SBA-15 at 2?GPa is attributed to the presence of liquid water in the pores due to melting point depression of confined water.