Milling of Micro Grooves on Glass Cylinder Surfaces

Micro milling is presented to machine micro grooves on a glass cylinder surface in a depth of cut of more than 10 µm. The milling tool is inclined in the cutter feed direction to finish fine surfaces in the operation. The effect of tool inclination on the cutting process during a rotation of the cutter is discussed in an analytical model. A 4-axis machine tool is developed to machine the micro grooves using the rotational and the linear motions. The cutting position on the cylinder surface is controlled to incline the milling tool in the cutting direction. Machining processes with a linear control in the longitudinal direction, with a rotational control of the workpiece, and with a simultaneous control of those motions are verified on the machine developed. Adjustment of workpiece alignment and pre-finishing are required for a high machining accuracy in the cutting operation. A feed rate of less than 0.24 mm/min is required to finish crack-free surfaces in cutting of fused silica.

Design and Flow Analysis of a Novel Optically Accessible Heavy Duty Diesel Research Engine

A new single-cylinder optically accessible heavy duty diesel engine has been conceived and constructed at the Institut fu¨r Kolbenmaschinen. Rather than being made from a quartz glass cylinder, the cylinder liner of this engine is modified with three round, flat optical access ports to facilitate laser-optical measurements within the combustion chamber. The flat optical surfaces prove less problematic than a quartz glass cylinder in terms of internal reflections, cleaning procedures, cost, and robustness. A specially adapted piston facilitates the passage of the laser sheet into the piston bowl and provides a view into the bowl at top dead center. Computational fluid dynamics (CFD) simulations were performed in order to estimate the effects of the optically necessary piston and cylinder liner modifications on in-cylinder flow and to compare the flow characteristics with those simulated for a non-modified engine. Emphasis is placed on turbulence behavior before top dead center. The trade-offs and limitations inherent in the modified piston design are discussed in this context. Further optical investigations with this engine will provide insight into the mixture formation and combustion processes. In particular, the soot formation and oxidation processes will be studied under realistic engine operating conditions.