YUNUS EMRE AYDOĞDU 9th week

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EGR

Exhaust gas recirculation (EGR) used in petrol, gasolin and diesel engine for reduce the Nitrogen Oxide emission.

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. In a gasoline engine, this inert exhaust displaces the amount of the combustible matter in the cylinder. In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. Because Nitrogen Oxide forms primarily when a mixture of nitrogen and oxyden is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduced the amount of NO forms of the combustion generates.

(Chrysler and Imperial Exhaust Emissions Referance Book, Page 8)

BMEP

The most common mean effective pressure is the Brake Mean Effective Pressure or bmep, The adjective brake refers to measurement of the flywheel. Originally power output was measured by applying an ordinary brake to the flywheel, the brake being attached to a long arm, and the moment produced was measured. The power produced by the engine is proportional to the product of the moment produced and the angular rotational speed. This break was a primative dynamometer, and was developed by F. M. Riche, Baron de Prony. And it was known as a Prony brake.

(John Leask Lumley, Engines an Introduction,first edition, page 16)

Surface waviness

Most surfaces when wiewed from sufficiently far away will appear to have a uniform texture. On close and detailed examination using modern techniques, however all surfaces will reveal same patterning, even if only at the atomic level.

Surface waviness is the periodic component of the surface texture. It arises most frequently from induced vibrations of a single point surface generator, and when the surface profiles are Fourier analyzed it usually occupies a spatial frequency band between those of surface form and roughness. Optical surfaces, such as metal mirrors or infrared optics, generated by single point diamond turning, are often influenced to same degree of waviness. The periodic nature of such a surface results in diffraction of a reflected or transmitted beam, giving rise and multiple images rather than a single image when the beam is brought into a focus. A surface generated by the more common process involving area contact between the lap and the work surface is unlikely to suffer in thids way. Polishing by the use of a flexible lap at speed can give rise to an orange-peel effect that can exhibit dominant spatial frequencies when Fourier analyzed. Similar patterns are sometimes seen on painted surfaces.

( Lionel R. Baker, Metrics for high quality specular surfaces, 2004,page 41)

Solid laser

The first lasers were all solid state lasers. They used a ruby rod to produce the laser. Today the most popular solid laser is the neodymium-doped,yttrium aluminum garnet (YAG). This is a synthetic crystal that when exposed to the intense light from the flash tubes can produce high quantities of laser energy. The high powered laser lasers have a problem because the internal temperatures of the laser rod increase with operation time. These lasers are most often used with low-power continuous or high powered pulse. The solid state laser is capable of generating the highest powered laser pulses.

(Larry F. Jeffus, Welding: Principles and applications, Fourth edition, page 189 )