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EXPLAIN VARIABLE GEOMETRY TURBOCHARGER SYSTEM?

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  • EXPLAIN VARIABLE GEOMETRY TURBOCHARGER SYSTEM?

    EXPLAIN VARIABLE GEOMETRY TURBOCHARGER SYSTEM?

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    • A Variable Turbine Geometry turbocharger is also known as a variable geometry turbocharger (VGT), or a Variable Nozzle Turbine (VNT). A turbocharger equipped with Variable Turbine Geometry has movable vanes which can direct exhaust flow onto the turbine blades. The vane angles are adjusted via an actuator. The angle of the vanes varies throughout the engine RPM range to optimize turbine behaviour.
    • Variable geometry turbochargers (VGTs) are a family of turbochargers, usually designed to allow the efficient aspect ratio (A/R) of the turbo to be altered as conditions change.
    • This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds;ifthe aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output.
    • At low rpm: The vanes are partially closed, reducing the area hence accelerating the exhaust gas towards the turbine. Moreover, the exhaust flow hits the turbine blades at the right angle. Both make the turbine spin faster.
    • At high rpm: At high rpm, the exhaust flow is strong enough. The vanes are fully opened to take advantage of the high exhaust flow. This also releases the exhaust pressure in the turbocharger, saving the need of wastegate.


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