Ignition

Research into reliable engine ignition and operability which is essential for safe, efficient, and sustainable flight.

During ignition a high energy spark (i.e. from the ignition source) ignites a portion of the fuel air mixture emanating from the fuel injector.  This flame then propagates across the combustor and stabilises to achieve sustained combustion.

This transient event can be challenging and is highly dependent on numerous factors.  It is desirable to achieve a flame with good stability and operability, that can support ignition over a wide range of engine operating conditions, whilst maintaining emission performance (see emissions and intermediate pressure test facilities). NCCAT currently supports several test facilities focused on assessing and understanding the ignition processes including:

  1. Atmospheric Ignition/Reacting Rig - Ground ignition, as the aviation vehicle prepares for take-off at ground/atmospheric conditions.
  2. Sub-Atmospheric Relight (SAR) - Flame-out during flight, where the flame is extinguished and requires to be relit at altitude.  At high altitudes, where the pressure is low, the air is thin and cold (sub-zero). At these onerous conditions ignition is particularly challenging.

These test facilities, combined with imaging and optical techniques, provide valuable insight into the complex ignition processes.  This is leading to future combustion systems with design features conducive to enhanced ignition performance.

Atmospheric ignition/reacting 

The atmospheric ignition/reacting rig focuses on ground level, ambient condition reacting experiments. The system inlet air can be modestly heated by a 200kW electric heater and supports typical aviation fuels (JET A), SAFs and gaseous fuels (Hydrogen). This is primarily an intermittent test facility focusing on transient effects and flammability limits such as flame ignition, weak extinction and blow-out.

The sizeable test section makes the facility suitable for a range of combustion geometry and hardware (i.e. fuel spray nozzles, annular combustor sectors, micro-gas turbines).  Typically, the atmospheric ignition rig is employed as a low-cost, low TRL experiment as an initial assessment of combustor/fuel spray nozzle operability; or assessment of designs in earlier stages research development.

Sub-atmospheric relight 

The sub-atmospheric relight rig is one of the few facilities in Europe capable of recreating the conditions of an engine at altitude.  The SAR facility possesses precise control of the flow rate, pressure and temperature of the fuel and air.  Controlling vacuum pressures typically from 10 psi to 5 psi (0.69 - 0.345 Bar absolute) corresponding to ~9800 feet and ~27000 feet above sea level respectively; and temperatures from ambient (+20°C) to -30°C on both fuel and air. Activities include both conventional liquid aviation fuels (Jet A) and sustainable aviation fuels (SAFs).  

The SAR facility primarily focuses on assessing transient performance parameters such as, flame ignition, weak extinction, blow-out and pull-away.  It accommodates semi-representative combustor sector geometries (typically 2-3 sectors of an annular combustor), with past and present programs including various engine types.  These test programs form a prerequisite and down-select, prior to larger scale fully annular test facilities, whilst allowing greater optical assess, more comprehensive measurement techniques, and greater fundamental understanding than its fully annular counterparts.