CLEAN-Gas Fellowships
Applications are now closed.
All positions have been appointed.
Introduction
CLEAN-Gas is a "European Joint Doctorate" programme for highly motivated young scientists, where state-of-the-art research is combined with a comprehensive training programme. The network is funded by the European Community through the Horizon 2020 Actions. The European Commission wants to make research careers more attractive to young people and therefore offers early-stage researchers the opportunity to improve their research skills, join established research teams, and enhance their career prospects via the so-called Marie Sklodowska-Curie Innovative Training Networks.
The scientific goal of CLEAN-Gas is to develop new experimental and numerical tools for improving natural gas combustion in innovative burners.
CLEAN-Gas Project, coordinated by Politecnico di Milano, has started on January 1st, 2015 and will be carried out over a period of four years. The network consists of 4 academic partner institutions and 4 industrial partners from four different countries in Europe.
CLEAN-Gas training programme is based on a strong collaboration between the public and the private sector and will combine local expert training at each academic and industrial partner, a network-wide secondment scheme, and an intense series of seminars, workshops and schools. The aim is to provide each ESR employed in the network with a unique set of cross-cutting expertise & skills, as requested by employers in combustion science, both in academia and industry.
Four university partners (Politecnico di Milano-Italy, Centrale Supélec-France, Université Libre de Bruxelles-Belgium, Technische Universitaet Darmstadt-Germany) are now looking for highly motivated candidates for 15 PhD positions (ESR). Starting date of each fellowship is contained in the related attachment.
The deadline for applications is 19 April 2015 at 18.00 C.E.T.
The deadline for applications was postponed until 30 April 2015 at 18.00 C.E.T.
The applications are now closed.
Please read carefully the employment conditions.
Employment conditions
- The contract will last 36 months.
- The gross salary for all ESR (PhD) positions is around 38000 €/year plus a mobility allowance of about 600 €/month and a family allowance of about 500 €/month, where applicable.
- Each ESR will have to complete at least one secondment (temporary transfer to another CLEAN-Gas academic partner) for a total period of about 10 months during the term of his/her employment.
- Each ESR must actively participate in the events organized by Universities and partners, such as training/network events as well as in regular yearly Outreach Activities targeting different audiences.
- Recruitment, selection and appointment of the ESR follow the European Charter & Code of Conduct. All CLEAN-Gas partners commit themselves to provide equal opportunities for male, female and disabled ESR.
- ESR's activity will be regularly monitored. Every year, the candidate and his/her work will be challenged and questioned. Failure in providing evidence of a regular and continuous commitment may result in his/her exclusion from the programme.
Requirements
- Eligible ESR candidates may be of any nationality but must not, at the time of recruitment have resided or carried out their main activity (work, studies, etc.) in the country of their host organization for more than 12 months in the last 3 years immediately prior to the reference date.
- ESR Candidates must be, at the time of recruitment by the host organization, in the first four years (full-time equivalent) of their research careers and have not yet been awarded a doctoral degree. This is measured from the date when they obtained the Master degree that would formally entitle them to embark on a doctorate.
- Proficiency in the English language (including both written and oral fluency) is essential.
- The Candidates must hold a M.Sc. Degree by the starting date of the fellowship, in one of the following areas: Engineering, Chemistry, Physics, Applied Mathematics.
- Further specific requirements and restrictions set by hosting countries and institutions are listed in each fellowship description.
How to apply?
Candidates may apply for more than one fellowship (maximum 15), but only a single application has to be produced, in which the Candidate has to provide the list of fellowships for which he is applying. The list has to be completed in order of preference.
List of Documents to be provided:
- Application Form (see attachment)
- Letter of motivation (approx. 1 page)
- Copies of degree and academic transcripts (with grades and rankings)
- Summary of Master's thesis (approx. 1 page)
- Short CV including a publication list (if any)
- Two reference letters from academics1. Candidates must indicate the academics details when applying.
- Proof of English language skills (see attachment)
- Passport copy
All the above-mentioned documents must be collected in a single pdf file (max. 10MB). The pdf file has to be sent to the CLEAN-Gas Coordination Office at the following email address: clean-gas@polimi.it. This being a compulsory procedure, any other means/format for submitting the application will not be accepted.
The Coordination Office will check the validity of the application, i.e. if all the requested documents and certificates have been correctly provided. If the answer is positive, the Coordination Office will send a confirmation email to the Applicant. If the answer is negative, the application will be discarded, but the Coordination Office will invite her/him to resubmit the application providing all the missing documents.
1 The letters must be filled in only using the given template. The academics will send the letters directly to the Coordination Office from their official e-mail address, no later than 7 May 2015.
Recruitment strategy
A common scoring system and recorded interviews will be used, respecting privacy and protection of Applicant's data. Applications from disabled persons are encouraged and will be favoured when equally qualified. The CLEAN-Gas project is committed to increasing the percentage of female scientists in the combustion community, and thus we strongly encourage female applicants.
The selection process is based on two steps:
- Evaluation of the documents provided by the Applicant
- Interview of each candidate having the eligibility requisites (evaluated through the first step).
As interviewing is extremely time-consuming and the applicants being widespread and numerous (even the shortlisted ones), the interviews will be organized remotely by at least the 2 promoters of the co-tutelle, via Skype.
List of fellowships
Fellowship ESR1
Title: Detailed kinetic mechanisms for combustion and oxidation of natural gas
Host institution: Politecnico di Milano (Italy)
Supervisor: Tiziano Faravelli
Start date: strictly before end of November 2015
Duration: 36 months
Gross salary: 39820 € per year
Objectives
The kinetic characterization of natural gas combustion represents an important and crucial point to analyze and describe, in order to correctly predict the flame characteristics and stability.
Thus, the main objective of this project is the improvement and tuning of a detailed kinetic mechanism with predictive capabilities in a wide range of operating conditions, describing the oxidation and combustion of natural gas. New recent data have appeared in the literature with new and well validated estimation of rate constants for many elemental reactions of the natural gas oxidation. The thermodynamic properties of species and radicals are now evaluated with a very high accuracy. All this information will be introduced in an existing mechanism to improve the performances. The quality of the resulting detailed kinetic scheme will be constantly measured through the comparison with experimental data available in the scientific literature and/or data available from the CLEAN-Gas project. At this purpose a database will be developed and automatic comparisons with statistical analyses will be proposed.
Expected Results
Detailed kinetic mechanisms for natural gas combustion and oxidation validated very wide ranges of operative conditions.
Planned secondment
BE-ULB (8-10 months): Chemical kinetic mechanism uncertainty quantification in combustion problems, including reactors and laminar flames. The primary objectives is to determine which reactions contribute most to the uncertainty in the predictions and whose rates may require further refinement.
Additional restrictions
The candidates must comply with the Italian laws and Politecnico rules for signing the contract. In particular, they have to provide the original academic diploma or a true copy of the same made by an Italian authority.
Non-EU candidates must legally stay in Italy at the starting date of the activities.
Please see the attached document for further restrictions and information.
Fellowship ESR2
Title: Chemical and physical pathways of pollutant formation in laminar flames burning natural gas
Host institution: Politecnico di Milano (Italy)
Supervisor: Alessio Frassoldati
Start date: strictly before end of November 2015
Duration: 36 months
Gross salary: 39820 € per year
Objectives
The understanding of combustion in practical combustors is essential to the goals of reducing pollution and increasing energy efficiency. However, three-dimensional models of these systems with detailed chemistry and complex transport phenomena are beyond our current computational capabilities. Instead, one can study flames with complex chemistry in simpler laminar configurations to provide insight into the chemical and physical processes occurring in many engineered systems.
Laminar flames (both premixed and diffusive) are commonly used to investigate chemical kinetic processes which are important in combustion because they can be described through relatively simple mathematical models. When analyzed in close conjunction with experimental data, these models can provide detailed information on flame structure and elementary reaction paths.
Thus, the objective of this work is to study the physical and kinetic mechanisms leading to the formation of pollutant species such as NOx, polycyclic aromatic hydrocarbons (PAH) and carbonaceous particles (soot) in laminar flames fed with natural gas in operating conditions close to those of interest. This knowledge can then be used for improving the design of equipment for combustion of natural gas, characterized by low emissions of pollutants.
The study will be focused on simplified geometries, like counter flow flames, premixed flat flames, and axisymmetric coflow flames.
Expected Results
Deeper understanding of the main chemical and physical pathways explaining the formation of pollutant species from the combustion of natural gas.
Planned secondment
BE-ULB (8-10 months). Chemical kinetic mechanism uncertainty quantification in combustion problems, including reactors and laminar flames. The primary objectives is to determine which reactions contribute most to the uncertainty in the predictions and whose rates may require further refinement.
Additional restrictions
The candidates must comply with the Italian laws and Politecnico rules for signing the contract. In particular, they have to provide the original academic diploma or a true copy of the same made by an Italian authority.
Non-EU candidates must legally stay in Italy at the starting date of the activities.
Please see the attached document for further restrictions and information.
Fellowship ESR3
Title: Reduction of detailed kinetic mechanism and development of soot models based on Method of Moments (MOM)
Host institution: Politecnico di Milano (Italy)
Supervisor: Alberto Cuoci
Start date: strictly before end of November 2015
Duration: 36 months
Gross salary: 39820 € per year
Objectives
The main objective is the proper reduction of the detailed kinetic scheme developed combustion and oxidation of natural gas, in order to apply it in unsteady, multi-dimensional simulations of multidimensional systems and/or real industrial devices. The reduction will be performed using different techniques available in the literature (DRG and its variants, path analysis, PCA, etc.), always ensuring an adequate performance in comparison with the detailed model. In additional, attention will be devoted to the derivation of non-stiff reduced mechanisms for numerical simulations requiring explicit integration solvers. The stiffness reduction will be achieved through the identification of quasi-steady- state (QSS) species and partial-equilibrium (PE) reactions. On-the-fly techniques for stiffness removal will be also taken into account and tested.
A specific methodology will be developed and applied with the aim to derive simplified soot kinetic models based on the Method of Moments (MOM), whose key parameters are derived from the detailed kinetic mechanism.
Expected Results
Development of a numerical procedure to automatically reduce detailed kinetic mechanisms for specific operating conditions.
Reduced (skeletal) kinetic mechanisms describing oxidation and combustion of natural gas with different level of complexity.
Development of numerical techniques for stiffness removal from detailed kinetic mechanisms.
Derivation of one or more simplified models, based on the Method of Moments, to describe soot formation to be applied in computationally intensive simulations.
Planned secondment
FR-CS (8-10 months). Application of Method of Moments for modeling formation of soot in multidimensional simulations of real industrial devices.
Additional restrictions
The candidates must comply with the Italian laws and Politecnico rules for signing the contract. In particular, they have to provide the original academic diploma or a true copy of the same made by an Italian authority.
Non-EU candidates must legally stay in Italy at the starting date of the activities.
Please see the attached document for further restrictions and information.
Secondment period at FR-CS: The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR4
Title: Large Eddy Simulations of premixed and non-premixed flameless combustion with relatively detailed kinetic mechanisms.
Host institution: Politecnico di Milano (Italy)
Supervisor: Alberto Cuoci
Start date: strictly before end of November 2015
Duration: 36 months
Gross salary: 39820 € per year
Objectives
Although flameless combustion is a promising solution to strongly reduce the formation of pollutant species, the non-linear interaction between chemical reactions and turbulence is not sufficiently understood to design flameless combustors, especially for gas turbine application. To numerically investigate mild combustion properties, Large Eddy Simulation (LES) is a good candidate. Indeed, high-fidelity simulations of non-premixed turbulent combustion regimes requires an accurate description of the fuel and oxidizer mixing that cannot be achieved under steady assumptions (RANS).
Thus, the aim of this study is to investigate the combustion process of natural gas in the distributed reaction regime (hence in flameless-like mode) using Large Eddy Simulations (LES) and complex chemistry. Lab-scale flames, with relatively simple geometries, will be considered, for which accurate experimental data are available. Effects of numerical discretization, chemical mechanism, operation type (premixed vs. non-premixed), and heat-losses at the walls will be studied and compared. The comparison with experimental data from the literature will give confidence in the quality of the predictions. Deeper knowledge of coupling between reactions and flow dynamics will be achieved through analysis of numerical results (modal analysis, etc.), bringing new insights into the flameless combustion process and providing recommendations for further experimental investigations.
Also in this case, particular attention will be devoted to the mechanisms leading to the formation of pollutant species.
Expected Results
Better understanding of interactions between reactions and fluid dynamics in premixed and non-premixed flameless combustion.
Planned secondment
DE-TUD (8-10 months). Application of numerical techniques based on the tabulation of chemistry to LES of combustion devices with complex geometries.
Additional restrictions
The candidates must comply with the Italian laws and Politecnico rules for signing the contract. In particular, they have to provide the original academic diploma or a true copy of the same made by an Italian authority.
Non-EU candidates must legally stay in Italy at the starting date of the activities.
Please see the attached document for further restrictions and information.
Fellowship ESR5
Title: Characterization of the unsteady behavior of laminar or low Reynolds flames submitted to controlled pulsations
Host institution: Centrale Supélec (France)
Supervisor: Thierry Schuller
Start date: June 2015
Duration: 36 months
Gross salary: 41425 € per year
Objectives
Stabilization of flames by imparting swirl to the flow allows operating the combustor in a lean premixed combustion mode, which is an efficient way to reduce pollutant emissions in gas turbines and industrial boilers. In this combustion mode, flames are however very sensitive to dynamic phenomena leading to sudden flashback of the flame in the injector, blow-off of the combustion or thermo-acoustic instabilities with undesirable large self-sustained oscillations. Determining the flame response to controlled flow pulsations allows analyzing the main physical mechanisms responsible of these dynamic phenomena. The objective of the work is to define a limited number of reference flames where these phenomena will be investigated by synchronized diagnostics with the acoustic pulsation. These data should allow a detailed description of the flame, flow and acoustic interactions taking place in the different configurations investigated and provide the necessary data for detailed numerical simulations.
Expected Results
In this project the dynamic response of a series of reference flames will be investigated. Laser Doppler velocimetry and Laser Induced Phosphorescence will be used to characterize the flow and thermal boundary conditions. Particle Imaging Velocimetry and OH Planar Laser Induced Fluorescence will be used to characterize the response of the flow and flame to acoustic forcing. Post-processing of these data will reveal the main parameters controlling the flame response and will be used to validate simulations in close collaboration. The data are explored in cooperation with the project partners for validation and simulations.
Planned secondment
DE-TUD (8-10 months). Data post processing and involvement to validation of numerical simulations.
Additional restrictions
The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR6
Title: Development of dynamic LES models including complex chemistry features
Host institution: Centrale Supélec (France)
Supervisor: Denis Veynante
Start date: October 2015
Duration: 36 months
Gross salary: 41425 € per year
Objectives
Large eddy simulation (LES), where largest turbulent motions are explicitly computed while only the effects of the smallest ones are modeled, is a powerful tool to describe turbulent combustion. First, this technique gives access to the flow dynamics, needed to predict combustion instabilities in furnaces or gas turbines. It also provides a better flow description as fresh and burnt gas zones, behaving differently in terms of turbulence, pollutant formation or radiative heat transfer, are identified at the resolved scale level. Dynamic formalisms, where sub-grid scale model parameters are automatically adjusted from the knowledge of the resolved flow field are very attractive, as they do not need parameter setting case-by-case anymore. These parameters may also evolve both in time and space according to the flow conditions.
This formalism was primarily developed to describe flame wrinkling factors in perfectly premixed combustion and fast, single step or tabulated chemistries, under flamelet assumptions. They were found very successful, with a moderate extra computational cost. The objective of this work is to extend dynamic models to non-premixed and partially premixed combustion regimes and to investigate the inclusion of complex chemistry features, required, for example, to predict pollutant emissions. Note that, because of the large range of chemical time scales from fuel oxidation to nitric oxide formation, reaction rate model parameters might depend on the chemical species considered.
Expected Results
The PhD student will investigate the extension of existing LES dynamic models to non-premixed and partially premixed combustion as well as the incorporation of complex chemistry features, comparing various strategies (chemistry tabulation, reduced chemical schemes, skeletal schemes...). The expected results are to assess the feasibility and the requirement of dynamic combustion models for non perfectly premixed turbulent flames and when a large range of chemical time scales is involved in view to predict pollutant emissions such as CO or NOx without setting ad hoc model parameters.
Planned secondment
DE-TUD (8-10 months). Large eddy simulations of turbulent combustion with dynamic models. Validations could be based on experiments investigated at TUD.
Additional restrictions
The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR7
Title: Large eddy simulations of large scale swirling turbulent flames
Host institution: Centrale Supélec (France)
Supervisor: Olivier Gicquel
Start date: October 2015
Duration: 36 months
Gross salary: 41425 € per year
Objectives
The objective of this thesis is to validate the classical turbulent combustion models as well as those developed in the other ESR in an LES framework. The originality of the subject lies in multiphysics approach to be implemented. The candidate will use the simulation framework developed at EM2C laboratory that allows taking into account the effect of radiation and heat transfer in the walls on the flame. For each of these phenomena a specific code is chosen, allowing the use of dedicated models. These three codes are coupled with special software available in the laboratory EM2C.
As these simulations include more physical phenomena, they should be more accurate. The results will be compared with experimental results obtained in other ESR.
Expected Results
The candidate will initially perform simulation of the target burner using an adiabatic combustion model. The combustion model will be improved by the addition of the inclusion of heat losses in the model. The validation simulations will be carried out by imposing thermal boundary conditions on the burner wall. These boundary conditions will be provided the experimental PhD students of the program. In a second step the candidate will couple his LES calculation with a MonteCarlo radiation code and a code calculating heat transfer in the walls of the burner. These fully coupled simulations will be validated by comparison with experimental results obtained in the framework of this program.
Planned secondment
BE-ULB (8-10 months). Post-processing of the LES results and comparison with experimental data.
Additional restrictions
The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR8
Title: Tabulated chemistry for large eddy simulations of turbulent combustion
Host institution: Centrale Supélec (France)
Supervisor: Benoît Fiorina
Start date: June 2015
Duration: 36 months
Gross salary: 41425 € per year
Objectives
Flame stabilization and pollutant predictions are strongly influenced by the interaction of complex combustion chemistry with the turbulence. Different strategies have been developed to model detailed chemistry phenomena at a reduced computational cost. Methods consist either in reducing the size of the chemical scheme or in tabulating the chemistry as a function of a reduced set of variables. In addition, various turbulent combustion models have been proposed to include these chemical descriptions in an LES formalism. Among existing methods, the Thickened Flame Model for LES (TFLES) is compatible with both reduced and tabulated chemistry. More recently, the Filtered Tabulated Chemistry for LES (F-TACLES), has been introduced as an alternative. The ability of these strategies to reproduce the mean chemical structure of turbulent steady flames has been extensively studied. However, their performances to describe the dynamic and the pollutant formation in unsteady flows remains to be assessed.
Expected Results
The PhD student will test the ability of several turbulent combustion modeling strategies to capture turbulent flame dynamics and pollutant formation. For that purpose, different chemical descriptions (such as reduced scheme and tabulated chemistry) combined with several turbulent combustion models (such as TFLES and F-TACLES) will be tested. The target flame retained for challenging the modeling strategies is a pulsed swirled flame stabilized in a non-adiabatic confined combustor experimented at the EM2C laboratory. Comparison between experimental measurements and numerical prediction of flame transfer functions will be performed. The influence of the turbulent combustion model and chemical description on the pollutant formation in an unsteady environment will be determined.
Planned secondment
IT-POLIMI (8-10 months). Coupling between tabulation of chemistry and reduction of detailed kinetic mechanisms.
Additional restrictions
The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR9
Title: Development and Validation of Combustion unsteady simulation techniques using advanced Filtered Tabulated Chemistry Strategy
Host institution: Technische Universität Darmstadt (Germany)
Supervisor: Amsini Sadiki
Start date: June 2015
Duration: 36 months
Gross salary: 36872 € per year
Objectives
The development of numerical models in context of LES (Large Eddy Simulation) for reacting flows has recorded significant progress in recent last years. Nevertheless, due to the complexity of the interaction between turbulence and chemistry in different combustion regimes (premixed, partially premixed and diffusion controlled), many scientific questions remain still open. Even within a single regime, various turbulence-chemistry interaction mechanisms lead to different flame behavior.
Validated LES models for partially-premixed operating conditions are very rare. Besides the diffusion-based flamelet approach with progress-variable (FPV), the premixed-based F-TACLES (Filtered TAbulated Chemistry for LES) combustion model has been recently extended to partially premixed regimes and to conditions with heat loss effects.
The objective of this PhD project is to further develop and validate appropriate sub-models to be integrated into a complete LES model using an advanced F-TACLES Strategy. This consists especially in introducing a dynamical formulation of the wrinkling model in order to avoid the undesirable tuning of the essential model parameter for each configuration, and thus to improve the predictability of the model under various operating conditions. The experimental data obtained in the framework of this consortium will be used for model validation. For engineering tasks the LES achievements will be assessed by comparison with those obtained from adaptive scale based RANS simulations.
Expected Results
First, a combustion-LES tool relying on the F-TACLES approach for partially premixed combustion under adiabatic tabulating conditions shall be made available using the OpenFOAM code. This will allow for including detailed chemistry and for preserving low CPU cost while limiting the number of balance equations to be solved. Second, the dynamical formulation of the wrinkling model will be considered. Finally non-adiabatic features of the combustion systems will be addressed.
Planned secondment
BE-ULB (8-10 months). Chemistry reduction procedures.
Fellowship ESR10
Title: Development and Application of an Eulerian Filtered Density Function Methodology coupled to a Tabulated Chemistry Strategy according to FPI/FGM
Host institution: Technische Universität Darmstadt (Germany)
Supervisor: Amsini Sadiki
Start date: October 2015
Duration: 36 months
Gross salary: 36872 € per year
Objectives
In many combustion systems, a single burning regime usually occurs. This can be described accurately using a classical flamelet formulation which is restricted to processes within the so-called flamelet regime. By including the curvature and unsteadiness effects, the applicability of the flamelet assumption could be extended. In order to consider the effect of turbulence on the chemistry, further information about the fluctuations is needed. In the context of pre-tabulated chemistry, this effect is represented by distributions of the scalars on the sub-grid level. Generally, a presumed shape (mostly a Beta-shape for the mixture fraction) of the probability density function (pdf) on the sub-grid level is assumed. With respect to other scalars this form may not be valid.
An alternative is given by the solution of the transport equation of one-point joint filtered fine grained pdf of the thermochemical variables. However, this equation involves a large number of independent variables, so that a solution is only possible using stochastic solution methods. In contrast to conventional Lagrangian stochastic particle methods, the Eulerian approaches have become attractive. From the literature, it turns out that such methods allow for describing both non-premixed, premixed regimes and partially premixed combustion.
In this project the LES-fdf methodology will be treated following an Eulerian moment method that will be coupled to a flamelet generated manifolds (FGM) tabulated chemistry to describe multi-regime combustion. Emphasize will be first put on the heat transfer and its effect on the flame evolution and pollutant formation under subcritical flow conditions. Supercritical conditions will be then especially considered. The LES-fdf tool will be validated using available experimental data.
Expected Results
The Eulerian approaches are attractive as they enable a well account of the turbulence-chemistry interaction using economical computational costs while including tabulated detailed chemistry. Within the OpenFOAM the candidate shall provide a validated LES-fdf tool that relies on the Eulerian method and accounts for heat loss effects. Starting with subcritical flows, the candidate will consider supercritical conditions and their impact on the LES-fdf modeling.
Planned secondment
IT-POLIMI (8-10 months). Chemistry tabulation.
Fellowship ESR11
Title:Experimental investigations using complex geometry of injectors and different fuels by means of advanced measurement techniques
Host institution: Technische Universität Darmstadt (Germany)
Supervisor: Andreas Dreizler
Start date: June 2015
Duration: 36 months
Gross salary: 36872 € per year
Objectives
Piloted flames are regularly used for stabilization of overall lean combustion. Piloted flames are typically fuel-rich such that an overall lean flame is anchored by a flame burning in a fuel stratified or non-premixed mode. The underlying turbulence-chemistry interactions with their impact on flame stabilization or pollutant formation is not well understood. Present combustion models need to be benchmarked against well-suited experiments. At TUDA an enclosed combustion system has been developed that mimics most important properties of gas turbine combustion. The fuel nozzle provides a swirled annular flow of premixed fuel and air. As a special feature the geometrical swirl number can be changed during operation. This allows operation at different stabilization points. In case of lean combustion an additional pilot flame is needed. The pilot flame is formed by a central jet issuing from a central bluff body that is surrounded by the annular swirled flow. The mass flow ratio between pilot and main flow can be changed from 0 to 1 providing a second measure for flame stabilization. The combustor is throttled to ensure no backflow from the exhaust pipe system. Optical access allows for the application of common laser diagnostics. Due to the optical access operational pressures are limited to below 10 bar.
Expected Results
In this project a series of practically relevant piloted lean flames at elevated pressures is selected. Flow fields and flame brushs are measured by means of particle image velocimetry and laser-induced fluorescence of OH radicals that are formed in the reaction zones. Based on this data the location of flame stabilization is investigated. The data are explored in cooperation with the project partners for validation of combustion models in this close-to-reality combustor.
Planned secondment
FR-CS (8-10 months). Data post processing and involvement to validation of numerical simulations.
Additional restrictions
Secondment period at FR-CS: The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR12
Title: Experimental investigations under differ¬ent thermal efficiencies and practical engineering conditions using advanced Laser Diagnostics
Host institution: Technische Universität Darmstadt (Germany)
Supervisor: Andreas Dreizler
Start date: June 2015
Duration: 36 months
Gross salary: 36872 € per year
Objectives
Practical combustion systems typically are operating in a fuel stratified mode. One unsolved issue in combustion modeling is the treatment of fuel stratified flames that might switch from premixed to non-premixed mode. For developing new modeling strategies and validation of such innovative models benchmark flames are urgently needed. For this purpose at TUDA a series of turbulent fuel stratified target flames has been investigated. For providing well-defined boundary conditions the nozzle is made from annular slots. A central pilot flame is used to anchor the flame such that operation at high Reynolds-numbers is possible. For selected flames the thermo-kinetic states have been investigated by means of Raman/Rayleigh scattering, including information on temperature and main chemical species concentrations. In a next step pollutants such as NO concentrations must be quantified that cannot be easily tabulated on reaction progress variables. Due to low concentrations more sensitive diagnostics such as laser-induced fluorescence (LIF) must be used.
Expected Results
In this project simultaneous temperature and NO concentration measurement are planned. Temperatures are measured either by Rayleigh scattering or by coherent anti-Stokes Raman scattering (CARS). Temperature is needed as measure of reaction progress and for density/quenching corrections for NO-LIF measurements. NO is excited in its A-X-transition around 226 nm and detected red-shifted. The new data are combined with previous measurements of velocities and main species concentration to provide a unique benchmark for combustion modeling including pollutant formation.
Planned secondment
FR-CS (8-10 months). Data post processing and involvement to validation of numerical simulations.
Additional restrictions
Secondment period at FR-CS: The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR13
Title: Development of PCA–based reduced models for natural gas combustion
Host institution: Université Libre de Bruxelles (Belgium)
Supervisor: Alessandro Parente
Start date: July 2015
Duration: 36 months
Gross salary: 37320 € per year
Objectives
In recent years, there has been an increasing interest for the use of Principal Component Analysis for the development of reduced-order combustion models. The PCA modelling framework has been demonstrated a priori and a posteriori for a wide range of configurations, including simple batch and perfectly stirred reactors, one-dimensional laminar flames and complex cases such as flame-vortex interaction as well as plasma flows. Results indicated that PCA-based models are able to provide very accurate results when compared to full size simulations. Current investigations have shown that PCA models are relatively invariant to parameters such as the Reynolds number of the flow. This implies that PCA models can be trained on relatively simple systems and used to simulated systems showing more complex turbulence/chemistry interactions. However, it appears still necessary to determine and quantify the validity range of PCA models, to determine: i) the required degree of complexity of the chemical reactor used to generate the model; and ii) the conditions at which the reduced models will not be valid anymore.
Expected Results
The objective of the present ESR are twofold: to extend the PCA modeling approach to relatively large kinetic mechanisms as the ones applicable to conventional and unconventional natural gas based fuels, and to validate the PCA approach in the framework of Large Eddy Simulation. For the former objective, PCA will be first in the framework of high-fidelity simulation tools such as DNS and ODT (One Dimensional Turbulence). This will the necessary to identify the required strategies to deal with relatively large kinetic mechanism (non-linear regression, kernel PCA, ...). The validation of PCA in the framework on LES will require the development of appropriate sub-grid strategies. At this stage, potential candidates include the Rate-Controlled Constrained Equilibrium (RCCE) and the Eddy Dissipation Concept (EDC) (from ESR 14).
Planned secondment
FR-CS (8-10 months). Extension of PCA to LES.
Additional restrictions
Secondment period at FR-CS: The candidate must receive a favorable opinion of the security officer in charge of CentraleSupélec and the EM2C laboratory. This procedure may induce a period of 2 months in the recruitment process.
Fellowship ESR14
Title: Optimization of kinetic mechanisms for non-conventional combustion regimes
Host institution: Université Libre de Bruxelles (Belgium)
Supervisor: Alessandro Parente
Start date: July 2015
Duration: 36 months
Gross salary: 37320 € per year
Objectives
The purpose of this ESR is to improve confidence in kinetic models and optimize their coupling with CFD simulations of novel combustion technologies such as MILD and oxy-MILD combustion. Methods like sensitivity analysis will be employed, to determine relative parameter importance and focus on the parameters showing the biggest influence on predictions. Once important parameters are identified, global sensitivity methods will be used to quantify the model behavior over the whole range of parameter uncertainties, which can be kinetic parameters such as Arrhenius parameters, activation energy, thermodynamic properties, and third body efficiencies. The kinetic schemes will be primarily validated using experimental data available in the literature. Validation/ optimization of the kinetic mechanisms will rely on the simulation of simple idealized reactors (e.g. PSR, batch, PFR) for species, temperatures and ignition delay times. Laminar premixed and counter diffusion flames will be then employed to validate the mechanisms for the prediction of minor species and pollutants.
Expected Results
The PhD will develop appropriate methodologies for the validation and uncertainty quantification of kinetic mechanisms in the framework of new combustion processes such as MILD combustion. The student will focus on the use/optimization of appropriate screening/sampling techniques, response surface methods (to reduce the function evaluation time for computationally intensive simulations). The final objective will be that of assessing the uncertainty associated to the use of a kinetic mechanism (e.g. the one developed in ESR1 for methane combustion) and its consistency with the available experimental data. The PhD will also focus on the effect of mechanism reduction and solution tabulation on the prediction, in the perspective of optimizing chemistry reduction approaches for the coupling of realistic chemistry in relatively large-scale simulations.
Planned secondment
IT-POLIMI (8-10 months). Optimization/Uncertainty Quantification of kinetic mechanisms.
Fellowship ESR15
Title: Sub-grid models for LES simulation of non-conventional combustion regimes
Host institution: Université Libre de Bruxelles (Belgium)
Supervisor: Alessandro Parente
Start date: October 2015
Duration: 36 months
Gross salary: 37320 € per year
Objectives
Combustion models for LES usually rely on the flamelet assumption and related modifications, which constrain the thermochemical space accessible in the numerical simulation. Whilst the use of transported PDF methods in LES appears still computationally prohibitive, especially for practical combustion systems, there are a number of sub-grid models showing promise for the inclusion of detailed kinetic mechanisms. The objective of the present study will be that of assessing the role of sub-grid models for the LES simulation of non-conventional combustion regimes. In particular, implicit LES (ILES) will be compared to other existing closures for finite-rate chemistry models, including Eddy Dissipation Concept (EDC) and the Partially Stirred Reactor approach (PASR).
Expected Results
The doctorate is expected to provide insight in the role of filtering and sub-closure models for relatively low-Da number systems as the ones investigated in the present project. A combustion-LES tool implementing the implicit LES, EDC and PaSR paradigms shall be made available using the OpenFOAM code. This will allow including detailed chemistry in LES simulations. Moreover, the impact of detailed and reduced chemistry will be also assessed, allowing optimising computational resources in the framework of large-scale combustion simulations. The numerical simulations will be validated using data from the literature and collected in a newly designed MILD combustion furnace installed at ULB.
Planned secondment
DE-TUD (8-10 months). Validation of the EDC and PaSR approaches.