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Quickstop [UK]
Combating adversyty.
The Garrett's convoluted spiral blade design is known as a backward-curved compressor impeller. In this design, the blade elements are not arranged in a strictly radial pattern, but are curved backward from the direction of rotation. This blade style is designed so that the air entering the impeller is at the same angle as the pitch of the blades. This reduces the shock losses at the inlet and allow the impeller to operate very efficiently at high rotational speeds. Despite their efficiency, however, these type of impellers do not exhibit as high a pressure ratio as radial-patterned impellers. Furthermore, centrifugal force at high speed tends to bend the spiral blades at their roots. So in essence, a turbocharger equipped with a backward-curved impeller helps an engine produce power in the upper-end of its rpm band (where its high efficiency in best appreciated), but is subject to severe stress which may affect its lifespan.
A turbocharger equipped with a backward-curved impeller reduces the shock losses at the inlet and allows the impeller to operate very efficiently at high rotational speeds that in-turn helps an engine produce power in the upper-end of its rpm band (where its high efficiency is best appreciated.
The straight, or radial impeller as used in the Mitsubishi, provides a higher pressure ratio at low rpm than the Garrett. As turbine speed increases, however, the straight blades give rise to inlet shock since the slower intake air strikes the intake's high-speed turbine blades at a sharp angle. This reduces compressor efficiency at high rpm. A Radial impeller used in housing of the same area ratio as a backward-curved impeller tends to result in improved low-end engine torque, but with less overall potential for power.
A turbocharger equipped with a backward-curved impeller reduces the shock losses at the inlet and allows the impeller to operate very efficiently at high rotational speeds that in-turn helps an engine produce power in the upper-end of its rpm band (where its high efficiency is best appreciated.
The straight, or radial impeller as used in the Mitsubishi, provides a higher pressure ratio at low rpm than the Garrett. As turbine speed increases, however, the straight blades give rise to inlet shock since the slower intake air strikes the intake's high-speed turbine blades at a sharp angle. This reduces compressor efficiency at high rpm. A Radial impeller used in housing of the same area ratio as a backward-curved impeller tends to result in improved low-end engine torque, but with less overall potential for power.