Meghna Dhanji

Meghna Dhanji

Aerospace Engineering BEng

Experimental Study of Air- Blast Atomisation on Planar Liquid Sheet in Liquid Rocket Engines

Analysis of Air-Blast Atomisation

The Space Shuttle Main Engine develops thrust by using high energy cryogenic propellants- liquid hydrogen and liquid oxygen, which are atomised prior to entering the combustion chamber. The project’s aim was to analyse fluids’ interaction upon injection and resulting spray geometry to determine suitable injection conditions resulting in formation of fine, atomised droplets. Atomised fuel droplets help enhance flame structure and optimise combustion performance.

A planar injector was designed in CAD, which was used to conduct High Speed Flow Visualisation. The experimental results were then analysed using MATLAB image processing to measure spray characteristics (i.e. droplet diameters and liquid intact length). Qualitative analysis was performed on wave growth and oscillations.

Water and air (test fluids) were injected at different flow rates, and their interaction was analysed using high speed flow visualisation. The main flow conditions to be achieved were:

• Laminar water flow

• High air flow rate to generate instabilities.

The designed 3-phase injector consisted of rectangular exits of high aspect ratio in order to capture fluids’ interaction in two directions.

• It was deduced that with increasing air- liquid momentum ratio (function of air- liquid density), the liquid intact length decreases.

• The shorter the liquid intact length is, the finer the resulting droplets are produced in the flow field- suitable for combustion performance.

• Other phenomena such as Kelvin-Helmholtz and Rayleigh Taylor instabilities, flapping instabilities, sinusoidal and dilatational wave growth were also studied in detail.