Session: 04-52 Ignition II

Paper Number: 103897

103897 - Ignition of a Safran Helicopter Engine With a Compact Nanosecond Laser System 

We report on the ignition of a SAFRAN helicopter engine using a compact laser system. The laser system delivers nanosecond infrared pulses at a high repetition rate  which energy can be up to 40 mJ. The first tests were run on a SAFRAN HE experimental bench operating at room temperature and ambiant pressure with jet A-1 liquid fuel,. We studied in detail  the impact of the laser pulse energy and the spark position on the engine ignition. To do so we developped  an optical focusing system, fixed on the engine carter, that enables to focus the laser pulse at different positions in the combustion chamber. The focused laser beam generates a plasma which ignites the engine. Our experimental data  shows the focusing position of the laser pulse has an impact on the ignition performances. At the optimal plasma position, we were able to ignite the engine with a pulse energy of only 3 mJ. Additionnally, the laser ignition system enables to ignite  the engine faster than with the conventional spark plug. To understand this behavior, similar experiments were run on the MERCATO experimental  bench at ONERA (the French aerospace lab).  Using a MIE scattering imaging technique, we studied the ignition of the spray generated by the start injector. Our data indicates, that depending on the focusing of the laser pulses in the combustion chamber, the kerosene droplets scatter more or less the laser light. This impacts the pulse energy and spot size at the focal point then influencing laser ignition efficiency. However, iginition succes requires a miminum density of kerosene droplets. Hence, the optimal laser ignition position is a compromise between the droplet density at the focal point and the laser beam scattering by droplets before reaching that position. This optimal position was found to well agree with our experimental data.

Presenting Author: Martin Maillard ONERA

Presenting Author Biography: Martin Maillard is a ONERA PhD student of the Bordeaux University. He got an engineer degree from IOGS Paris. In the frame of a collabaoration between University of Bordeaux and ONERA, he is currently working on the development of a compact laser ignition system for aeronautic engines.

Authors:

Martin Maillard ONERA
Gabriel Amiard Hudebine University of Bordeaux
Mikaël Orain ONERA
Pierre Doublet ONERA
Patrick Beaure D'augères Fibercryst
Claude Berat Safran Helicopter Engines
Christophe Viguier Safran Helicopter Engines
Stéphane Douillard Safran Helicopter Engines
Eric Freysz Université de Bordeaux