Turbocharger Fuel Saving VTA Technology by MAN Takes Off

By George Backwell at July 21, 2012 09:10
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Variable Turbine Area (VTA) geometry for the largest exhaust-gas turbochargers, introduced by MAN Diesel & Turbo about four years ago, recently topped the hundred sales mark according to the manufacturers, as the technology gradually proved itself effective in reducing fuel-oil consumption in medium and low-speed marine diesel engines.

The VTA is designed for fitting on supercharged large-bore diesel engines with varying load profiles. Due to its adjustability, the VTA efficiently adapts to a wide range of engine operations, making it particularly useful for the present-day trend to slow-steam bulkers, tankers and container ships.

MAN say that the first VTA unit delivered has so far accumulated over 20,000 operating hours running on engines using heavy fuel oil (HFO) to give fuel consumption savings of up to 5 g/kWh.

VTA Turbocharging

VTA technology enables the quantity of charge air to be more precisely matched to the quantity of fuel injected, encouraging reduced specific fuel consumption, and emissions, along with improved dynamic behaviour of the engine turbocharger system.

Basically, a nozzle ring equipped with adjustable vanes replaces the fixed vane ring used in standard turbochargers, making it possible to increase or decrease the pressure level in the engine by changing the pitch of the guide vanes. The illustration below shows the main components.

Turbocharger VTA Geometry: Image courtesy of MAN Diesel & Turbo

 Changing the pitch of the vanes regulates the pressure of the exhaust gases coming to bear on the turbine. When the blow-through area is reduced in size by the variable vane geometry, the speed of the inlet flow to the turbine is increased, which in turn increases the turbocharger speed, leading to an increase of the compressor-side charge pressure.

Control of the vane position is fully electronic, with feedback or open-loop control features mapped vane adjustment. Each vane has a lever directly connected to a control ring, which is actuated by an electric positional motor with integrated reduction gear.

A comprehensive range of control signals can be used, including charge air pressure after the compressor, and exhaust gas temperature before and after the turbocharger. Control packages are tailored by the manufacturer to match working on mechanically controlled engines or those with electronic management.

To date, MAN Diesel & Turbo say that the VTA reference list covers the TCR20, TCA55, TCA66, TCA77, and TCA88 turbocharger frame sizes; while retrofits are also possible.

 

Inage courtesy of MAN Diesel & Turbo

Source: MAN Diesel & Turbo VTA Project Guide: Variable turbine area for TCA turbocharger


Comments (1) -

Very Nice article -Thanks for uploading.Ranjith Gurugamage

Ranjith Gurugamage |     7/25/2012 9:36:33 PM #

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