TPL series

A completely new generation turbocharger from ABB Turbo Systems— the TPL series—was launched in 1996 to meet the demands of the highest output low and medium speed engines, the designer having set the following development goals:

• High compressor pressure ratio for increased engine power output.

• High turbocharger efficiency levels for reduced engine fuel consumption and lower exhaust gas temperatures.

• High specific flow capacity, resulting in a compact design and low weight.

• High reliability, long lifetime and extended periods between overhauls.

• Easy maintenance, even for machines operated under adverse conditions (such as those serving engines burning low quality heavy fuel oils).

The uncooled design features an overall number of components reduced by a factor of six compared with the VTR series, contributing to extended times between overhauls (see Figure 7.16 a, b, c).

A modular configuration provides the TPL series with the flexibility to meet the turbocharging requirements of two-stroke and four-stroke engines. Two-stroke engines with outputs from 5000 kW to 25 000 kW

Figure 7.16 (c) Modular design concept of ABB TPL turbocharger: 1. Filter-silencer; 2. Air volute; 3. Rotor block; 4. Gas inlet casing; 5. Nozzle ring; 6. Gas outlet casing

per turbocharger are served by the TPL-B variant, introduced in 1999, while the original TPL-A model addresses demands from four-stroke engines delivering 1250 kW to 18 000 kW per turbocharger.

Despite differences in their thermodynamics and design, the TPL-A and TPL-B series share established features: for example, the basic modular TPL concept and the central bearing housing with the complete bearing assembly. All TPL turbochargers consist of a central cartridge unit with the rotor assembly. The casings on the compressor side and on the turbine side are connected by flanges; and all casings are uncooled. Complete dismantling of the turbocharger, including the nozzle ring, is possible from the 'cold side', leaving the exhaust pipes in place and untouched.

All TPL turbochargers feature the same bearing technology, with plain bearings selected to secure a long lifetime. The non-rotating, radial bearing bushes are suspended in a squeeze film damper, which increases the stability of the rotor while reducing the dynamic forces and hence the load on the radial bearings. The main thrust bearing comprises a free-floating disk between the rotating shaft and the stationary casing. This bearing concept halves the speed gradient in the axial gap so that the losses and the risk of wear are significantly reduced; thanks to this technology, the thrust bearing is also very tolerant to inclinations of the rotor.

Since two-stroke engines usually have a lubrication system driven by electric pumps rather than by the engine itself, an emergency oil supply has to be provided to ensure that the turbocharger runs out safely in the event of a black-out. The TPL-B turbocharger can be optionally equipped with an integrated emergency oil tank mounted on top of the bearing casing. Since this system is based on gravity it does not require any auxiliary support.

Thermodynamic improvements from the TPL-B series derive from a new axial turbine family (the TV10) which was especially developed for turbocharging systems for two-stroke engines. Five turbine wheels and over 20 nozzle rings can be specified for each TPL-B model, these options allowing the turbocharger characteristic to be adapted to the requirements of the application within a wide range.

Two new radial compressor stages were developed for the TPL family. The TPL-B compressor features a single-piece aluminium alloy wheel with splitter-bladed impeller design and backswept blades for high efficiency and a wide compressor map. Peak efficiencies exceeding 87 per cent are reportedly obtainable. Enlarged compressor diameters further increased the volume flow, thereby fostering optimized matching of the turbochargers to the engine application.

The TPL 91B model, which supplemented the TPL 73, 77, 80 and 85B models, was introduced as the world's largest turbocharger, yielding a volume flow rate above 50 m3/s and a compressor pressure ratio up to 4.5. Co-developed by ABB and its Japanese licensee IHI, this model is primed to boost even more powerful two-stroke engines than those currently on the market.

ABB planned to extend variable turbine geometry to more of its turbocharger designs, the system having been successfully engine-tested with a TPL65 model before entering service.

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