Leading edge shielding concept in gas turbines with can combustors

The remarkable developments in gas turbine materials and cooling technologies allowed the steady increase in combustor outlet temperature and hence in gas turbine efficiency over the last half century. However, the efficiency benefits of higher gas temperature, even at the current levels, are significantly offset by the increased losses associated with the required cooling. Additionally, the advancements in gas turbine cooling technology have introduced considerable complexities into turbine design and manufacture. Therefore, a reduction in cooling requirements for the current gas temperature levels is a possible way for gas turbine designers to achieve even higher efficiency levels. The leading edges of the first turbine vane are exposed to high heat loads. The high coolant requirements and geometry constrains limit the possible arrangement of the multiple rows of film cooling holes in the co called showerhead region. Many different showerhead configurations have been tested, varying the number of rows of holes, holes inclination angle and shape, etc. However it is hard to believe that the present leading edge cooling strategy using showerheads can allow further increase in turbine temperature without excessive use of coolant air. Therefore new cooling strategies for the first vane have to be investigated. In gas turbines with multiple combustor chambers around the annulus the transition duct walls can be used to shield, i.e. protect the first vane leading edges from the high heat loads. In this way the stagnation region at the leading edge and the showerhead of film cooling holes can be completely removed and the total amount of cooling air can be significantly reduced. By eliminating the showerhead the shielding concept significantly simplifies the design and lowers the manufacturing costs. This paper numerically analyses potentials of the leading edge shielding concept for cooling air reduction. Different shielding arrangements and vane shapes were numerically studied. It was concluded that significant reduction of the cooling air can be achieved. It was also found that the internal cooling architecture of the first vane can be simplified and that the new cooling arrangement does not adversely affect the vane aerodynamics

Observation of free-surface shear flow and its relation to bow wave-breaking on full forms Joint report

SIGLETIB Hannover: RA 489 (420) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman