" Investigation of Ignition under Sub-atmospheric Conditions"

This work is part of the "SOPRANO" EU project. http://www.soprano-h2020.eu/

 

Motivation

The ability to relight the jet engine after a flame out event is critical for flight safety. From an engineering perspective, ensuring the re-ignition and the subsequent proper spool up of the jet engine, beyond the inherent safety implications is a challenging process. One reason that makes the relight process of the engine difficult is the low temperature and low pressure, which slows the evaporation of the atomized fuel and limits the concentration of the oxygen and therefore the reaction rates.

The development of modern combustors for jet engines has been challenging for engineers, due to the conflict of interest among emission standards, flame stability and engine's relight. The better understanding of the re-ignition process has a fundamental importance since it aids the development in the early stages and therefore reduces significantly the design iterations. Furthermore, future concepts with lean burning, which counter the (NO_x) emissions could be realized.

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ISCAR rig and Combustion chamber

The experiments are conducted at the ISCAR("Ignition under Sub atmospheric Conditions-Altitude Relight) rig. It is one of the few experimental facilities worldwide, which simulates the high altitude conditions (low pressure and temperature) for flowing kerosene-air mixtures.

In this research activity a single injection RQL (Rich-Quench-Lean) combustion chamber is used. It has been developed by Engler-Bunte-Institute within the scope of SOPRANO EU Project. The configuration is quite realistic and consists of dilution and effusion cooling holes, which have been sized to reproduce the conditions of a real engine. The chamber provides optical access via quartz windows, which facilitates high speed imaging recording of the unsteady flame kernel generation and propagation.

                                                                    Simplified overview of the ISCAR rig

Combustion chamber in operation

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Experimental results

 

           

 

        Ignition probability without effusion cooling                                      Ignition probability with effusion cooling

 

 

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                                                               Minimum FAR comparison of the two configurations

 

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      High speed imaging recording

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  Tracking of flame's luminosity center

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  Spray measurements under high altitude conditions