3232881 - 1064A turbo charger assembly
GARRET VNT 25 TURBOCHARGER
It has variable geometry and is connected to the exhaust manifold; its purpose is to increase the volumetric output of the engine.This variable geometry turbocharger consists of:
- a centrifugal compressor (1)
- a turbine (2)
- a series of moving vanes (3)
- a pneumatic actuator (4) for operating the moving vanes.
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This variable geometry turbocharger makes it possible to:
- increase the speed of the exhaust gases in the turbine at low engine speeds
- slow down the speed of the exhaust gases in the turbine at high speeds.
Controlling the speed (kinetic energy) of the exhaust gases makes it possible to produce:
- greater engine torque at low speeds
- greater maximum power at high speeds.
Operation at low rotation speeds
When the engine rotation speed is low, the exhaust gases possess little kinetic energy: under these circumstances, a conventional turbine would rotate slowly, supplying a limited supercharging pressure.In a variable geometry turbine (1), on the other hand, the moving vanes (2) are in the maximum closure position and the small sections between the vanes increase the speed (C) of the intake gases.Increased intake speeds result in greater peripheral speeds (U) for the turbine and consequently the compressor.The speed of the gases inside the impeller is shown by the vector (W).
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