TPL..-B Tailor made Two-Stroke Turbocharger
Christoph ROFKA* and Dr. Volkmar HAUEISEN**
The ABB turbocharger generation TPL was designed to meet the requirements of current and future low, medium and high-speed engines. After the successful introduction of the TPL..-A version, ABB Turbo Systems Ltd. has launched a tailored version for two-stroke diesel engines. The so-called TPL..-B reflects the demand for highest efficiencies in combination with large specific volume flows. It is available in the four biggest TPL sizes covering an engine output from 5'000 up to about 25,000 kW per turbocharger. Beside thermodynamic improvements the TPL..-B is also equipped with additional features focusing on two stroke applications while joining already proven design features of the TPL..-A.
This paper gives a detailed description on how the TPL..-B was derived from the TPL..-A type turbocharger. Additionally service experiences with regard to thermodynamic behaviour and mechanical reliability are presented.
Key Words: Turbocharger, 2-Stroke
The TPL turbocharger was launched in 1996 as a platform designed for adaptation to different applications. In the meantime, the TPL..-A series has become well established in the four-stroke diesel engine market and is available today in seven frame sizes. With its TPL..-B series, another adaptation of the TPL concept, ABB has introduced a turbocharger especially for the two-stroke engine market.
Two-stroke diesel engines make special demands on the turbocharging system. The demand for increased mean effective and scavenging pressures is in line with the requirement for higher turbocharger efficiency. Until now the two design targets set for turbocharger development higher compression ratios and increased efficiency could be achieved by means of derivation. A third target is a more compact design, which in thermodynamic terms means higher specific volume flow. It is therefore evident that the development of turbocharger thermodynamics has to concentrate on three main targets simultaneously.
The goals of higher compression ratios and specific volume flow are self-explaining. Increasing efficiency is more complex. To raise efficiency for a wide range of turbomachines optimisation is required mainly at one operational point, e.g. a fixed turning speed for generator-driving devices. For turbocharger applications, optimising efficiency means increasing it over a wide operating range, as part-load performance is as important as excellent efficiency at full load.
Besides the thermodynamics, there are specific design features of turbochargers on two-stroke engines that require attention. Consideration has to be given to the lube oil supply, the engine fuel type, the exhaust gas temperatures and how the turbocharger is mounted on the engine. All of these influence the design concept of the turbocharger. Or, put another way, they have to exert some influence if a turbocharger is to be legitimately called "tailor-made" for two-stroke applications.
These are the main boundary conditions for successful development of a turbocharger for two-stroke engines. Even when these requirements are met, it still has to be proved that the product's design is robust and reliable. This has to be verified by a comprehensive test series covering all the aspects of the engine's subsequent application.
2. DESIGN CONCEPT
The main design goal for the TPL turbocharger family was a simple, robust and reliable construction. A modular design concept was chosen that also provides easy accessibility for servicing.
All TPL turbochargers consist of a central cartridge unit with rotor assembly. All TPL casings are un-cooled. Complete dismantling of the TPL turbocharger including the nozzle ring is possible from the "cold side", leaving the exhaust pipes in place and untouched.
* Turbo Systems United Co., Ltd.
Arca-Central Bldg. 18 F
2-1,Kinshi 1-Chome, Sumida-Ku
Tokyo 130-0013 / Japan
FAX: +81 3 5611 5974,
** ABB Turbo Systems Ltd
FAX: +49 56 205 34 66