Efficient turbines The low-pressure turbine contributes signifi- cantly to engine cost. Depending on engine size and concept, its cost share amounts to 15 to 20 percent. In component development, MTU is exploring novel constructions to reduce complexity and concurrently looking at more cost-effective materials for use at elevated temperatures. Under its “High Lift Blading” project, for instance, the company is develop- ing an innovative blading concept to reduce the blade count in the low-pressure turbine without appreciably reducing its efficiency. A welcome by-product in that endeavor is the potential reduction of module weight. Novel light-weight materials hold promise of saving up to ten percent of the overall turbine weight. While they are just as strong, rotor blades in titanium aluminum weigh only half as much as blades in conventional nickel alloys. This provides a tremendous weight-saving potential for low-pressure turbine blades for use at operating temperatures of up to 800 degrees centigrade. Before one material can be exchanged for the other, however, numer- ous questions need to be answered. It is im- portant to know, for instance, how the material holds up under operating conditions or what manufacturing process would be best to use. Intentions over the next five years are to en- hance the turbine efficiencies by reducing flow losses by as much as 15 percent, no mean feat when considering the high degree of effi- ciency already attained. This is hoped to re- duce an aircraft’s fuel consumption by 1.1 percent. For an A380 flying the route from Frankfurt to New York about 600 times a year this would translate into a reduction of fuel consumption of approximately 757,000 liters. The availability of more computing power and new design programs will in the years ahead permit the three-dimensional design of the blade ducts, including side walls and fillet radii. In the process, numerical aerodynamic 13 Complex simulation methods—seen here are parts of a high-speed low-pressure turbine—markedly reduce development times. The high-speed low-pressure turbine of the PW1000G geared turbofan—shown here is one of the three stages—is unrivaled worldwide. design optimization methods are used. For operation at the high altitudes commonly as- sociated with long-haul airliners and business jets, improved airfoil designs and measures to selectively influence the boundary layer will be explored. In air traffic, flight noise is a limiting factor. Individual flight movements have indeed be- come less noisy over the past several years, but in all, their growing incidence is eating away at the improvement. The primary sources of flight noise are engines, undercarriage and the air enveloping the aircraft. In accordance with ACARE targets, next-generation engines should provide a ten ENPdB improvement over current engines. That is a notable figure, considering that a ten dB or so difference halves the perceived noise. To keep the noise low that the low-pressure turbine contributes to engine noise under cer- tain operating conditions, such as approach, a number of noise abatement measures, such as the 3D contouring of turbine blades, are being explored using an experimental turbine specifically set up for the purpose.