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Zhao B.,Basic Technology Research Center | Li S.-B.,Beihang University | Zhou S.,Beihang University | Zou X.-Q.,China Aviation Powerplant Research Institute | Huang S.-Q.,China Aviation Powerplant Research Institute
Tuijin Jishu/Journal of Propulsion Technology | Year: 2013

In order to study the impact of bleeding on compressor performance, this paper sets up a simplified mathematical and physical model, and uses numerical simulation to explore parameters of bleeding rate, bleeding area, the angle and length of bleeding structure in 49 cases. Studies show that due to the effects of the bleeding, the mainstream flow accelerates in the upstream of the bleeding groove, and decelerates in the downstream. There is a certain pattern in the impact of bleeding parameters on mainstream thermal performance. Bleeding rate mainly determines how much the thermodynamic parameters change, and bleeding area mainly affects where the thermodynamic parameters change, while the angle and length of the bleeding structure influence how the internal bleed air flows.

Sun P.,Basic Technology Research Center | Li S.,CAS Institute of Mechanics | Yu G.,CAS Institute of Mechanics | He X.,CAS Institute of Mechanics | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2014

For laser surface hardening (LSH) of large-sized workpieces, a wide and uniform hardened layer of a single track is pursued. In this study, two kinds of shaped laser beams were used in LSH of 42CrMo cast steel to obtain the required hardened layer. One is a stripy spot with uniform-intensity array spots and the other a stripy spot with intensity blowup in the edge of the whole array spots. As a comparison, a Gaussian laser beam was also adopted. A three-dimensional finite element model was used to simulate the thermal history of specific points by the latter shaped beam and the Gaussian laser beam. The surface morphology, microstructure, microhardness, and uniformity of hardened layers were studied. The results showed that a wider and more uniform hardened layer could be obtained using the latter shaped beam at relative higher scanning velocities and laser power. The thermal history of a material has an important effect on the microstructure and microhardness finally formed. Due to the high peak temperature and heating rate caused by the latter shaped beam, a higher value of microhardness in the transformation hardened zone was found. © 2013 Springer-Verlag London.

Maruyama T.,Basic Technology Research Center | Saitoh T.,Basic Technology Research Center
Tribology International | Year: 2010

The oil film thickness was measured under conditions of minute vibrations using an elastohydrodynamic lubrication (EHL) ball-on-disk test rig. Poly-alpha-olefin (PAO) oil was used as the lubricant under conditions of pure sliding where only the ball specimen was minutely vibrated. It was found that an oil film formed when the amplitude ratio was greater than 1.6. Moreover, when conditions were changed to the maximum vibrating speed, oil viscosity, and maximum contact pressure, the critical amplitude ratio at which the oil film began to form remained at 1.6. Consequently, calculated results showed that the oil film was formed when the amplitude ratio was π/2 (nearly equal to 1.6), which closely agreed with our test results. © 2009 Elsevier Ltd. All rights reserved.

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