Spray Technology and Aircraft Gas Turbine Engines

The highest levels of spray science and technology are required in the design, testing and analysis of gas turbine aircraft engines. Here are some of the challenges that the industry is currently facing:

• Fighter aircraft require engines that are half the size of current engines, with twice the thrust.
• All aircraft engine companies are looking for high thrust, lightweight engines, and advanced commercial supersonic aircraft manufacturers are also addressing the issue of low NOx.
• NOx emissions must be one-tenth of current commercial aircraft in order to minimize chemical reaction of NOx with ozone in the stratosphere.
• Engines for supersonic commercial aircraft must provide for doubling the size of the aircraft--as well as distance traveled without landing. Both metrics – size and distance -- will be greater than the now-mothballed Concorde supersonic aircraft.
• The cost of a passenger ticket should not exceed that of current transoceanic subsonic commercial aircraft.

In order to meet these overall engine design goals, stratified charge combustion with rich, quick quench, followed by lean burning zones, are required in series. This avoids stoichiometric burning, which is the most efficient way of using fuel but also generates the highest temperatures and consequently, the highest NOx emmissions.

These very stringent combustion conditions require a high degree of control of fuel injection, atomization, droplet trajectories and airflow fields in each component of the stratified charge engine.

We have a number of processes available to us that produce sub-optimal results: Stoichiometric mixing results in high temperatures with associated high NOx formation. Rich burning generates unburned hydrocarbons and soot particulates. Lean burning results in lower temperatures and inflammability. In order to meet the many requirements of the aircraft gas turbine engine industry, combustor designers must control atomization and drop trajectories as they interact with strong turbulent airflow fields with swirl and rotation.