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The Trend of Turbocharger and Supercharger and Their Effect
Published May 21, 1997 by Society of Automotive Engineers of Japan in Japan
Event: JSAE Spring Conference
As a result of environmental pressure resulting in stricter emission regulations in Europe and America, turbochargers and superchargers are playing an increasing role in efforts to improve engine performance. One development in the field of turbochargers has been the mixed flow turbine, which allows the housing to be made smaller and lighter than conventional radial types, yet reduces inertia moment by over 40% while increasing acceleration by 26% compared with a radial unit of the same capacity. The use of TiAl, a new metal alloy, rather than ceramic turbines is also attracting attention as the weight is just 48% that of conventional heat-resistant alloys and it performs better in harsh environments.
Another development intended to improve turbo efficiency has been the variable gate system, with variable vanes in the turbine nozzle, and there are examples of these that can increase torque by nearly 20% over the revolution spectrum. To improve mechanical efficiency, angular ball bearings are being used, resulting in maximum dn values of 1.5 million, improving low-speed torque output and improving acceleration. Other advances include utilizing emission discharge pulsation energy.
The main types of supercharger in use are the Roots, scroll and Lysholm types. With the latter type, improvements have been made in reducing noise by optimizing the shape of the discharge port and using new silencers.