The Evolution of Garrett® VNT™ Turbocharger

rozwoj vnt 1The Evolution of Garrett® VNT™ Turbocharger

The development of Garrett® VNT™ turbocharger started in 1990 when the TD2502 was first launched based on the old TB25 model.

Controlled by a pressure actuator connected by hose directly to the compressor outlet, this was VNT™ technology in its simplest; the vanes were at the minimum flow position at engine start up and during low speed/low load running while at higher engine speeds and loads, the vanes opened up. This ensured that the acceleration of the turbine wheel and compressor wheel was maximized under low energy conditions to give rapid torque rise at low engine rpm and yet still allow high gas flow and reduced back pressure for maximum engine power.

The VNT™ principle was then applied to our GT range of turbos and the development has taken it from the original version (dubbed the generation 0) all the way to the current 3rd generation enhanced by the latest optimization. The different VNT™ generations can be identified by their model numbers; starting with GT (1st generation), GTA (2nd generation), GTB (3rd generation) and GTC (optimized 3rd generation). Each one of these generations represents a significant improvement in the design, performance and durability of the VNT™ mechanism.

The advanced design of the latest 3rd generation turbo allows us to optimize the material choice for each individual component to meet our OEM customers performance requirements. For the nozzle assembly, we are using 8 different materials, each one chosen specifically for the job that it has to perform. Some parts are also Gas Nitrided, which delivers improved surface hardness, wear resistance, fatigue life and corrosion resistance.


rozwoj vnt 2What is a VNT™ DutyDrive Turbo?

Favored among medium and heavy-duty truck and bus applications, Honeywell’s Garrett® VNT™ DutyDrive, previously called Double Axle VNT™ (DAVNT), uses 12 –19 turbine nozzle vanes supported by twin axles.

The function of these two axles is to locate the vanes between the unison and nozzle rings.

VNT™ DutyDrive provides quicker transient response, promotes greatly enhanced engine braking, and is a key component in driving exhaust gas recirculation.

The center housing is qualified to withstand 700ºC max turbine inlet temperatures.

The durable nozzle assembly is capable of handling turbine inlet pressure exceeding 5 bar under engine-braking conditions. The nozzle vanes are positioned via a Rotary Electronic Actuator (REA) – specifically designed for VNT™ DutyDrive systems – or a high-pressure pneumatic actuator. In case of REA, an integrated position sensor controls both vane movement and position.

Boreless titanium compressor wheels and speed sensors allow for high pressure ratio operation and sophisticated control, while durability is underpinned by a Honeywell patented pressure balance system that channels exhaust gas to both sides of the turbine vanes, equalizing pressure and minimizing actuation forces, hysterisis and wear.

This technology is ideally suited to engine displacements ranging from 4L to 14L.

Examples of VNT™ DutyDrive turbos available for our Aftermarket network are 768755-5005S and 727701-5013S respectively for Toyota and Hino applications. More detailed information is available in the online Product Search section of our new Aftermarket website.


 

rozwoj vnt 3Honeywell VNT™ DualBoost™ Technology

Staying at the forefront of the rapidly moving turbocharger business requires constant investment and development.  With strong market influences on vehicle design, such as downsizing, reduced exhaust emissions and improved fuel economy and reliability, new ideas and designs are constantly being explored by Honeywell.

Of course, everyone also expects their new vehicle to have more power and torque than their old one…but at the same time they want to enjoy the benefits of better fuel efficiency. Thanks to turbo technologies developed by Honeywell, it’s possible to have it all!

Here is one of the latest ideas recently launched by Honeywell that is helping the auto industry to meet and surpass customers’ expectations:

VNT™ DualBoost™ – which recently won the prestigious PACE auto award – has been launched in the US on the 2011 model year Ford Powerstroke 6.7L V8 diesel engine used in the F-Series Super Duty.

Although this is a design bristling with innovations, what makes this turbo really stand-out is its compressor technology, which is helping to deliver near two-stage performance in a single unit.

The benefits of having two compressor wheels feeding an engine are well known and two stage turbo installations are becoming more and more commonplace. However, packaging (the space available to fit them) is often restricted, so what Honeywell engineers have succeeded in doing with DualBoost is to combine the airflow from two compressor wheels within a single turbo!

In fact, the “two” compressor wheels are actually a single piece, with mirror image blades, running within a complex looking compressor housing (made up from three separate components) with two separate compressor inlets and a single, common outlet. Both inlet sections of the compressor housings also incorporate ported shrouds which broaden the operating flow range of the compressor.

From a VNT™ perspective, DualBoost combines the vane cartridge concept used on our latest 3rd Generation VNT™ turbos, which separates the turbine housing from the vane assembly for improved reliability and performance, with the variable vane assembly of the AVNT™ (Advanced VNT), which has proved such a reliable performer with our US customers. In addition, the turbine housing incorporates a single wastegate valve to enable the use of an even smaller turbine for improved response at low engine speed while further widening flow capability.

The control for the variable vanes is also different to that used on passenger car turbos, as it is electro-hydraulic. The actuator is a powerful hydraulic unit, integrated into the center housing casting, which uses engine oil acting on a power piston to move the vanes through an internal rack and pinion gear. The flow of oil to the actuator is controlled by a variable solenoid valve, which receives its demand signals directly from the vehicle ECU via a single electrical connector.

The high powered actuator is needed on this application because the engine runs with very high levels of EGR (Exhaust Gas Recirculation) in order to comply with the latest US emissions regulations. The variable vanes can be moved towards the closed position on demand, which increases the back pressure in the exhaust manifold and literally “drives” the inert exhaust gas back towards the lower pressure in the air inlet manifold to help reduce regulated emissions. This is only possible using a VNT™ with a high powered actuator.

The torque from the turbine wheel is transmitted to the compressor with minimal power losses, due to the use of an advanced angular contact ball bearing system. This uses light weight, low inertia and highly durable ceramic balls at both ends of the cartridge, performing the combined functions of a journal bearing and thrust bearing system in a single compact assembly. The ball bearing systems have derived from many years of experience gained in our highly successful race/rally/performance turbo range; proven repeatedly in numerous World Rally and Le Mans series wins!

Unusually, the turbo in this application sits on its own integral pedestal in the middle of the Vee, on top of the engine. The pedestal and turbo also include quick connectors for oil and coolant, ensuring that installation and servicing can be completed easily and quickly.

Finally, to ensure that the oil, air and exhaust gas stay where they should be,  piston rings are used at both the turbine and compressor ends, with the latter being pressurized by air. This is fed directly from the compressor’s diffuser section, to ensure efficient sealing under all running conditions.

So to summarize, the new VNT™ DualBoost™ turbo combines some of Honeywell Turbo Technologies’ finest ideas in a single package….the world’s most advanced turbo.