1    Context

In the framework of its thoughts on climat impact aircraft activities, the French Network on Aeronautical and Environmental Thematic (Réseau Thematique Aeronautique et Environnement RTAE) of CORC recommande futhermore research on condensation trails and induce cirrus due to aircraft activities at upper troposphere and lower stratosphere.

The condensation trails formed within aircraft path into sufficient cold and wet atmosphere may persist and can evolve into induced cirrus or cloud layer. They can also be formed from the engine aerosol emission (mainly soot) that are ice condensation nuclei. These cloud layer modifications may constitute a significant pertubation of the Eartch global radiatif budget.

Formation processes of this cloud phenomenon remain not well-know, as well as the magnitude of their impact on climat. Therefore the RTAE group build a six complementary projects package in order to improve knowledge on these phenomenons and start research on mitigation or prevention options:

  • Project 1, Characterisation of aircraft engine particulate matter emission (Caractérisation des émissions de particules des moteurs aéronautiques)--> MERMOSE
  • Project 2, Formation processes and evolution of the condensation trails (Processus de formation et d'évolution des traînées de condensation); []
  • Project 3,  Impact on climat modelisation of the condensation trails and induced cirrus (Modélisation de l'impact climatique des traînées de condensation et des cirrus induits)
  • Project 4, Study and development of aircraft board humidity sensor (Etude et développement de capteurs d'humidité embarqués)
  • Project 5, Prediction device of favourable aera for persistent trails formation (Système de prévision des zones propices à la formation de traînées persistantes)
  • Project 6, Processus of  decision (Processus de decision)

ONERA, some CNRS laboratories, IRSN and SNECMA (SAFRAN group) build a team to work on the bullet 1 and create the MERMOSE project.

2    Objectives

The first goal is to characterise aircraft engine particulate matter emission, particularly in flight cruse condition, to provide needed input data for studying the formation of cirrus induced from condensation trails. Soot particles concentration and their water pick-up capacity of water vapour are primary parameters to analyse induced cirrus formation mecanisms. The project 1 will contribute to improve existing data bases for project 2 investigations, especially with the addition of  soot physico-chelmical characterisation that drive their reactivity to their concentration and size distribution.

Beyond the 6 projects proposed by the RTAE group on cirrus and condensation trails study, the data collected in the framework of the Project 1 will be useful as well for airport air quality. Moreover, they will be an essential support to the french contribution on SAE E-31 work on aircraft engine emitted particulate matter measurements to provide a new ICAO engine certification standard.

In order to answer to the main goals, this project is divided into 2 workpackages:

  • Workpackage 1 : Engine particulate matter characterisation
  • Workpackage 2 : Study on the impact of soot physico-chemical properties on ice formation mecanisms

Figure 1: structure du projet
Figure 1: Projet workpackages

Workpackage 1 aims to collect the most representative data on engine particulate matter emission in real use conditions. To match this goal, we performe cartography at the exit of a real SNECMA aircraft engine during ground test. These measurements are quickly heavy to handle and expensive. They allow us to investigate LTO (Landing & Take-Off) cycle but the cruise condition is still unreachable. To deal with difficulty, as a complementary add-ons we will do combustion chamber tests at ONERA test bench named M1. These tests will use a similary injection device as the one used on the real aircraft engine within a tubular chamber. They will allow us to make the comparison between engine and combustion chamber emissions. Since nowadays, it exits only few data on the evolution of soot between combustion chamber exit and engine exit. Moreover, these tests will be used to reproduce the engine normal cruise exploitation and to investigate the impact of the setting on emissions.

The SaM 146 engine, developped within a SNECMA and Saturn (Russia) cooperation, and recently certify, has been choose because is will be a good representative of the modern aircraft engine technology. Emissions from aircraft engine to other aircraft engine could vary but it will stay to a same level. Compilation of existing data on other type of engines and our measurements could be done within this project.

Workpackage 2 goal is to perform experimental studies on soot, including ones from workpackage 1 (from SAM 146 engine and combustion chamber). The production of laboratory soot has the advantages to be cheaper from engine test and to control their physico-chemical properties. The overall experiments aims in one hand to characterize the physical (morphology, structure, texture, …) and chemical (elementary chemical composition, surfacic chemical groups, …) properties of the engien collected soot. In other hand, the investigations deal with soot reactivity within water, espesially the mecanisms, condition of formation and growth of ice. This work will give important input data to model induced cirrus formation from soot measured properties at the exit of engine. In parallel, some work is also perform on the conception for a new chemical reactor made specifically for studying ice crystal formation dynamic on soot. This device will allow analyses on "free" soot particules,ie not deposited on a substract. A such tool will allow to have more representative conditions without alteration othe the soot during their deposition on a substract.