Design, Modelling and Experiments of a Multi-Lobe, Swirl Bend Mixing Nozzle for a Turbo-Fan Engine

Abstract

The design, numerical simulation, and experimental testing of a mixing nozzle is presented in this project. The motivation behind this research is reducing the IR signature of a turbofan engine and measuring backpressure data. IR signature reduction was be done by (1) blocking the line of sight to the turbine; and, (2) reducing the plume temperature of the exhaust jets. The nozzle design methodology describes nozzle construction parameters and how optical blockage was integrated into the design; this was done using available CAD software. Later, the designed nozzle was numerically tested on the turbofan engine using ANSYS products, and experimentally in the Gas Turbine Lab at Queen’s University where cold flow experiments were conducted. Various nozzle geometries were tested under cruising altitude engine parameters. The nozzle models were tested under various inlet swirl conditions (0°, 20°, -20°) to mimic real engine environment. RANS CFD simulations using the k-epsilon turbulence model predicted lower backpressure for the engine with the designed nozzle compared to the rounded nozzle case. Also, the increased mixing between the bypass and core engine exhaust resulted in a reduced temperature of the core jet. Pressure losses, backpressure, blockage, and flow features were the parameters of interest. Later, the designed nozzle was 3D printed, mounted on a ducted fan, and tested in the low-speed wind tunnel. The ducted fan produced a high-speed swirling jet. A Seven-hole probe was used to take velocity and pressure data. Two load cells were used to measure thrust produced by the fan. With the swirling nozzle attached to the fan, the measured thrust produced by the fan was higher than the thrust measured with a rounded nozzle.