Two by two looks good

The ability to achieve a key target is helped by the launch of a new product at this year`s SMM exhibition.

Alstom Turbochargers aims to achieve sales of 2,000 units by 2000 as part of its plan to establish the company as the largest independent supplier of turbo-chargers in the world. During the course of the past few years it has transformed itself into an aggressive competitor in a market that has been traditionally dominated by ABB.

Prototypes of the turbo-charger were tested on Wartsila`s 6L46 technology demonstrator. A Wartsila18V38 engine is the first to be fitted with the 458; some 30 to 40 models of this engine are already fitted with 457 turbo-chargers, says Alstom. The delivery of the first 458 is expected by the end of November, with rollout following soon after.

The 458, which will gradually replace the older 457 series, is aimed at power generation and larger ships. The 558 model has been developed, virtually in parallel with the 458, although the first of these will not be delivered until later in the year. The latest model offers a 5.5:1 pressure ratio, and tests have confirmed an efficiency of 70 per cent. For applications with a pressure ratio of up to 5:1, an aluminium impeller is used; above this titanium has to be used. The impellers are solid and connected to the shaft in a patented method.

One feature is the provision of two different compressor impeller designs, the G and the GS.. The G is primarily intended for power generation uses. It gives high efficiency at higher pressure ratios, but thus sacrifices efficiency at lower engine loads. By contrast with the GS impeller design, efficiency peaks at a lower pressure ratio and gives better fuel consumption at lower loads. It is thus better for marine applications.