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Zhaoming Huang,Zijun Zheng,Tao Wang,Li Wang,Hongcheng Gan,Weiguo Chen 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.4
On a single-cylinder gasoline engine test bench, the experimental study of the effects of polishing the combustion chamber wall and piston top surface on the indicated thermal efficiency and combustion characteristics were carried out, and the mutual influence of combustion phase, combustion duration and indicated thermal efficiency before and after polishing the wall of combustion system was systematically analyzed. The results show that when the single-cylinder gasoline engine operates at stoichiometric air-fuel ratio, low load and low compression ratio, the heat transfer loss of the polished combustion chamber is reduced and the fuel economy is improved, and the indicated thermal efficiency is increased from 40.8 to 42.2 %. With the increasing of load and compression ratio, the knock effect caused by the reduction of heat transfer loss after polishing is enhanced, and the combustion phase is delayed and the combustion duration is prolonged, which eventually leads to the decrease of the indicated thermal efficiency. After combustion chamber polishing, HC and NOx decrease by up to 70 %. With the increase of compression ratio, HC emission gradually increases, while NOx emission gradually decreases. There is no obvious change trend of CO emission before and after polishing. When the gasoline engine operates in lean combustion mode, the indicated thermal efficiency increases effectively, and the highest thermal efficiency exceeds 45 %; When the gasoline engine operates at indicated mean effective pressure of 1.05 MPa, the reduction of heat transfer loss in the combustion chamber after polishing enhances the knocking tendency, resulting in the overall decrease of the gross indicated thermal efficiency compared with that before polishing.
Xu, Sheng,Yan, Zheng,Jang, Kyung-In,Huang, Wen,Fu, Haoran,Kim, Jeonghyun,Wei, Zijun,Flavin, Matthew,McCracken, Joselle,Wang, Renhan,Badea, Adina,Liu, Yuhao,Xiao, Dongqing,Zhou, Guoyan,Lee, Jungwoo,Chu American Association for the Advancement of Scienc 2015 Science Vol.347 No.6218
<P><B>Popping materials and devices from 2D into 3D</B></P><P>Curved, thin, flexible complex three-dimensional (3D) structures can be very hard to manufacture at small length scales. Xu <I>et al.</I> develop an ingenious design strategy for the microfabrication of complex geometric 3D mesostructures that derive from the out-of-plane buckling of an originally planar structural layout (see the Perspective by Ye and Tsukruk). Finite element analysis of the mechanics makes it possible to design the two 2D patterns, which is then attached to a previously strained substrate at a number of points. Relaxing of the substrate causes the patterned material to bend and buckle, leading to its 3D shape.</P><P><I>Science</I>, this issue p. 154; see also p. 130</P><P>Complex three-dimensional (3D) structures in biology (e.g., cytoskeletal webs, neural circuits, and vasculature networks) form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, but design options are constrained by existing capabilities in materials growth and assembly. We report routes to previously inaccessible classes of 3D constructs in advanced materials, including device-grade silicon. The schemes involve geometric transformation of 2D micro/nanostructures into extended 3D layouts by compressive buckling. Demonstrations include experimental and theoretical studies of more than 40 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences, and frameworks, each with single- and/or multiple-level configurations.</P>