In order to draw the highest effectiveness from marine engines, they must be run at the highest rated RPM. Yet, with several norms, traffic rules, fuel efficiency factor etc., marine engines cannot always be operated at high speed. As the RPM of the engine decreases, the air supply from the turbocharger also decreases, starving the combustion space of air and resulting in improper combustion and increased fuel consumption.
To counter this problem, auxiliary blowers are fitted. These blowers come into action at particular low loads. Variable Geometry Turbocharger or Variable Turbine Angle (VTA) Turbocharger is the solution for supplying sufficient scavenge air to marine engine’s cylinder at all load ranges. Let’s find out what is VTA and how does it works.
What to know about Variable Geometry Turbocharger or VTA?
A VGT or VTA is a turbocharger, wherein movable vanes are replaced for conventional fixed vanes, which can change angles to control the exhaust flow on the turbine blades. This helps the engine control to balance the volume of air with the fuel along the entire engine load range.
Working of VTA
The VGT or VTA consists of nozzle rings furnished with adjustable angle changing vanes.
Each vane is connected to control a ring using a lever, which reduces the thermal hysteresis and increases the positional accuracy.
The vane position or the angle is adjusted by the control ring connected to the electric positional motor via reduction gear.
The control system governs the action of the microprocessor controlled positional motor. The position or angle of vanes is thus altered after comparing the feedback signals of – air pressure after the blower, and exhaust gas temperature before and after the turbocharger.
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Advantages of VTA
- Works on the entire load range of the engine
- Eliminates the need of auxiliary blower
- Reduces the fuel consumption
- Reduces exhaust smoke emission and hence air pollution
- Lower’s CO2 , Nox, and Sox emission
- Reduces soot and carbon deposits on combustion and exhaust space
- Reduces fouling of engine parts
- Improves efficiency of the engine
- Economical in operation