Which type of turbine blade is used in high thrust engines?

• A. Impulse-reaction type
• B. Impulse type
• C. Reaction type
• D. Mixed type

Answer: (A)

High-thrust engines need turbine blades that can efficiently extract a lot of energy while keeping blade loads and weight manageable at very high speeds. An impulse-reaction blade design does just that by combining two working principles: the impulse portion mainly changes the gas velocity with a portion of the blade’s geometry, while the reaction portion uses pressure distribution along the blade to pull energy from the gas as it flows over the blade surfaces. This mix provides good efficiency across many stages and can handle the high work requirements without becoming excessively heavy or overstressed.

Pure impulse blades are strong and good at directing flow, but they don’t extract as much energy per blade in high-speed, high-thrust conditions. Pure reaction blades distribute a larger pressure drop along the blade but require thicker, heavier blades and can be less efficient at very high speeds. The impulse-reaction combination offers the best balance for high-thrust engines, hence its use.