Sulzer RT-flex. Fuel consumption flexibility\r\n
Sulzer RTA engines have always been highly competitive in fuel consumption right across the load range owing to the use of variable injection timing (VIT). Variable exhaust valve closing (VEC) was also added in RTA84 T engines in 1991 to reduce further the part-load BSFC. These benefits already been carried over to the electronically-controlled common-rail systems of the RT-flex engines.\r\n
At the first stage of development of RT-flex engines, however, the main objective as are achieved in the mechanical-camshaft engines, particularly with respect to power, speed, fuel consumption, exhaust emissions, cylinder pressures, etc. Thus the curves of brake specific fuel consumption (BSFC) of the first RT-flex engines have been the same as with corresponding RTA engines, or perhaps slightly lower in the part-load region. As the fuel injection pressure at part-load is kept higher with the common-rail injection system, combustion is sufficiently better to have a beneficial effect on fuel consumption in part-load operation.
Recently an alternative fuel consumption curve was introduced with Delta Tuning to provide even lower BSFC at loads less than 90 percent full load. For both the original (Standard) and Delta Tuning curves, the RT-flex engines comply with IMO NOx regulation.
The question, of course, arises as to why the BSFC could not be lowered at all engine loads and speeds. It is technically possible to do so. With RT-flex engines all the relevant parameters can be continuously varied so that the engine can follow any specified BSFC curve as engine load and speed are varied. Yet there is a limitation because of the need to comply with the IMO NOx regulation and the inevitable trade-off between lower fuel consumption and greater NOx emissions. This explains the shape of the new BSFC curve given by Delta Tuning. The BSFC is lowered in the mid- and low-load range, thereby increasing the NOx emission levels at those load points, but then has to be increased at high engine loads (90-100 percent load) for a compensating reduction in NOx levels.
Delta Tuning was first applied in the first Sulzer 8RT-flex96C engine which completed its official shop test on 9 April 2004.