THE DYNAMICS OF VARIABLE EXHAUST NOZZLE LINKAGE MECHANISM OF MILITARY AERO-GAS TURBINE

Document Type : Original Article

Authors

1 Scientist, Gas Turbine Research Establishment, C. V. Raman Nagar, Bangalore - 560 093 , India.

2 Department of Mechanical Engg., Indian Institute of Science, Bangalore - 560 012, India.

Abstract

The military aero gas turbines of modern day fighter aircraft are fitted with fully variable convergent-divergent (C-D) exhaust nozzle in order to meet the optimum performance requirements of the engine at various operating conditions. The variation in nozzle area is achieved through a flap actuation linkage mechanism that is operated by a set of hydraulic actuators powered by an engine driven integrated hydraulic power pack. This paper presents the methodology developed for dynamic force analysis of an axisymmetric single actuation C-D nozzle mechanism which meets the prescribed schedule of nozzle throat area to exit area ratio as a function of actuator stroke. A computer program has been developed for the dynamic force analysis. One-dimensional isentropic relationships (with throat correction) for flow with area changes are used to compute the pressure distribution across the axi-symmetric C-D nozzle. The results of force analysis are the required actuating hydraulic force and the reaction forces of various joints which are used for the stress analysis and mechanical design of individual links as well as for configuring the hydraulic actuation system required for operating the variable exhaust nozzle. An illustrative example has been provided to demonstrate the procedure.

Keywords