New turbochargers for genset engines

Bosch Mahle Turbo Systems (BMTS) has developed a new turbocharger specifically to be used in engines for electric power generation, i.e., genset engines. The exhaust gas turbocharger is coupled with a “Series 1600,” 14-liter V8 engine from MTU, and is suitable for both 50 Hz and 60 Hz applications.

Depending on the configuration, the 8V 1600 genset engine from MTU has a power output of 358 to 448 kW and complies with Tier 3 emissions limits, which apply to large stationary engines in the USA and Europe. Two turbochargers are installed in each engine – one for each cylinder bank.

This development from BMTS replaces two types of turbochargers that were previously required to satisfy the broad requirements for 50 and 60 Hz operation. The BMTS turbocharger greatly reduces the number of variants and provides flexibility in terms of 50 or 60 Hz operation; this setting can even be changed during live operation, if required. This has been made possible thanks to special compressor developments characterized by a wide operating map.

In addition, the compressor housing for the exhaust gas turbocharger was modified to increase the pumping limit. Particular attention was given to the pressure pulsations arising from the intermittent opening of the intake valves. Typically, these are especially pronounced in eight-cylinder engines. A recirculation channel was integrated, which shifts the turbocharger’s pumping limit. Hence, the turbocharger is less likely to pump. This is achieved by targeted back flow to the compressor inlet.

Moreover, BMTS is using a special turbine wheel for the first time, whose flow rate has been adapted for both operating modes of 50 and 60 Hz. The design of the twinscroll turbine housing allows for combined exhaust flows from the cylinders so that exhaust pressure pulsations are better suited for the pulse turbocharging effect. Consequently, the exhaust gas turbocharger is more responsive, with a lower exhaust back pressure leading to increased efficiency and reduced consumption per kilowatt hour.

BMTS matches the high service life requirements of up to 12,000 operating hours, depending on load spectrum and oil change intervals of 500 hours, with conventional materials. However, this was only possible by means of extensive numerical calculations during the turbocharger’s development phase. Special mention should be made to the fact that BMTS carried out virtual containment tests as part of the housing development for the turbine and the compressor, which led to a significant reduction in the development time. During these tests, the turbine wheels are accelerated beyond their respective speed limits and destroyed in the process. Any detached parts can damage the housing due to the high energy being generated. However, no damage may arise that could cause a following part to escape the housing. Critical areas and potential failure points could be detected on the computer during virtual analysis. Thus, the design was already optimized before the hardware was finalized and the prototypes were constructed. In addition, appropriate parameters were defined for the real tests using the virtual containment results.

About BMTS

Founded in 2008, Bosch Mahle Turbo Systems is a joint venture of Bosch and MAHLE—two well-known parent companies with rich traditions, both representing high standards and top quality. Bosch Mahle Turbo Systems develops and produces tailor-made exhaust gas turbochargers for passenger cars and commercial vehicles. The company currently employs around 375 people at locations in Stuttgart and Blaichach in Germany, and St. Michael in Austria.