NOPR Community:

Experimental and analytical studies on the pullout strength of round thread casing connections

Sun, 01 Dec 2013 00:00:00 GMT

Title: Experimental and analytical studies on the pullout strength of round thread casing connections Authors: Gao, Lianxin; Shi, Jiaoqi Abstract: Pullout failure is one of the primary failure modes of API round thread casing connections. Make-up torque and thread tolerances are the two most important factors that can affect the pullout strength. In this paper, the pull-out failure process and mechanism are studied using the finite element analysis (FEA) method. In addition, the effects of make-up torque and thread tolerances on the pullout strength of API round thread connections are analyzed. The FEA results are validated through tension tests on a total of 34 pins and 17 couplings. The results show that pull-out failure initially occurs at the first and second teeth near the coupling end. At the same time, thread tolerances especially unmatched taper have notable effect on pullout strength. The tests show that higher make-up torque levels are beneficial to the pullout strength. Make-up torque 15~20% higher than the maximum API limit is recommended when round thread casing connections are used in oilfield. Page(s): 497-503

Synthesis and characterisation of freestanding diamond coatings

Sun, 01 Dec 2013 00:00:00 GMT

Title: Synthesis and characterisation of freestanding diamond coatings Authors: Mallik, Awadesh K; Bysakh, Sandip; Pal, Kalyan S; Dandapat, Nandadulal; Guha, Bichitra K; Datta, Someswar; Basu, Debabrata Abstract: Freestanding polycrystalline diamond (PCD) coatings are of immense technological importance. PCD has been grown over silicon substrates by microwave plasma assisted chemical vapor deposition (MWPACVD) process. The coatings are grown by suitable optimisation of the growth parameters of a 915 MHz microwave reactor. Thereafter, 1:1:1 solution of hydrofluoric acid (HF), nitric acid (HNO₃) and acetic acid (CH₃COOH) is used to etch out the silicon wafer from the backside of the coating. Hereby, freshly generated nucleation surface, could be characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and stylus profilometer and could be compared with the growth side. It is found that both the nucleation side and growth side are of very high quality (full width at half maxima, i.e., FWHM < 8 cm^-1). The growth side is (111) textured, whereas, the nucleation side is very smooth with embedded detonation-nano-diamond (DND) agglomerates. These freestanding coatings are successfully laser cut into different geometrical shapes. They are found to be optically translucent having high refractive index. Cross-sectional microscopy of the laser cut edge reveals novel melting features of the CVD grown diamond columns. Page(s): 522-532

Combustion of methyl esters of various origins in the agricultural engine

Sun, 01 Dec 2013 00:00:00 GMT

Title: Combustion of methyl esters of various origins in the agricultural engine Authors: Kruczyński, Stanisław W; Orliński, Piotr Abstract: The paper discusses the issues concerning the methyl ester mixtures of various origins in terms of using these mixtures as self-contained biofuels or components of a fuel intended for use in compression-ignition engines used in the means of transport. The selected physical and chemical parameters of the chosen mixtures have been compared to the requirements of the EN 14214 standard specified for the rape oil acid methyl ester (RME).
The tests have been carried out at an engine test bed with 1104C-44 PERKINS engine and allowed for determining the influence of methyl esters on the most important parameters characterising the combustion processes as well as the emission of the toxic components of the exhaust gas. The combustion process was assessed on the basis of the experimentally measured pressure in the combustion chamber. Increase in pressure and heat release characteristics are determined. Also share of the kinetic (premixed) and diffusion phases in the entire combustion process for all tested fuels are determined. The results for various mixtures are obtained under the same engine operating conditions and are referenced to the results for the standard hydrocarbon diesel fuel. The emission of toxic gases are determined in accordance with ISO 8178, based on the concentration of the exhaust gas components measured with AVL CEB II and smokemeter AVL DIGAS. Page(s): 483-491

Reverse thrust characteristics of water jet with different geometry nozzles

Sun, 01 Dec 2013 00:00:00 GMT

Title: Reverse thrust characteristics of water jet with different geometry nozzles Authors: Shi, Zhaocun; Cao, Shuping; Luo, Xiaohui; Tang, Xiaoqun Abstract: This paper is to investigate the effects of nozzle geometry on the reverse thrust characteristics under various nozzle dimensions, inlet and outlet conditions. The reverse thrust formula is deduced based on the elementary momentum theory through the theoretical analysis. CFD simulations are conducted to acquire the pressure and velocity distributions on the outlet cross-section of nozzles. The pressure and velocity distributions are substituted into the reverse thrust formula and therefore the computational results of the reverse thrust are calculated. The experiments are also carried out in comparison with the computational results. The results indicate that the water jets issuing from the streamline nozzle produce considerably larger reverse thrust compared to the other two geometries. The reverse thrust reaches the maximum when the aspect ratio (length to diameter ratio) l/d=1. Under the same flow-rate and aspect ratio, at the bigger diameter the reverse thrust is smaller. The reverse thrust shows linear and quadratic growth with increasing inlet pressure and flow-rate, respectively. The outlet pressure exerts little effect on the reverse thrust. The computational results are found in good agreement with the experimental results. Page(s): 476-482