Preliminary design study of an enhanced mixing eductor system for the LHA (R) gas turbine exhaust

Abstract

A preliminary design study was conducted to determine the geometry for an enhanced mixing eductor system for the Landing, Helicopter Assault Ship Replacement (LHA R) program gas turbine exhaust. A one-dimensional analytical model, with a correction factor applied to the secondary mass flow, was developed to predict the secondary air mass flow rate and the exhaust temperature at the mixing tube exit plane. The resultant design consisted of a high aspect ratio lobed nozzle and a mixing tube. The model was also used to predict the backpressure developed by the ducting configuration. The proposed design resulted in a 50% reduction in exhaust temperature with only a 6 inch H2O increase in back pressure. A detailed design of the oval-to-rectangular transition duct is provided, based on empirical data from a similar duct design. The study also included a prediction of plume radiation intensity in the 3-5 æm band for various aspect ratio slots.