A computational study of the effects of multiphase dynamics in catalytic upgrading of biomass pyrolysis vapor

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145281/1/aic16184.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145281/2/aic16184_am.pd

A feasibility study on the use of low-dimensional simulations for database generation in adaptive chemistry approaches

LES/PDF approaches can be used for simulating challenging turbulent combustion configurations with strong turbulence chemistry interactions. Transported PDF methods are computationally expensive compared to flamelet-like turbulent combustion models. The pre-partitioned adaptive chemistry (PPAC) methodology was developed to address this cost differential. PPAC entails an offline preprocessing stage, where a set of reduced models are generated starting from an initial database of representative compositions. At runtime, this set of reduced models are dynamically utilized during the reaction fractional step leading to computational savings. We have recently combined PPAC with in-situ adaptive tabulation (ISAT) to further reduce the computational cost. We have shown that the combined method reduced the average wall-clock time per time step of large-scale LES/particle PDF simulations of turbulent combustion by 39\%. A key assumption in PPAC is that the initial database used in the offline stage is representative of the compositions encountered at runtime. In our previous study this assumption was trivially satisfied as the initial database consisted of compositions extracted from the turbulent combustion simulation itself. Consequently, a key open question remains as to whether such databases can be generated without having access to the turbulent combustion simulation. Towards answering this question, in the current work, we explore whether the compositions for forming such a database can be extracted from computationally-efficient low-dimensional simulations such as 1D counterflow flames and partially stirred reactors. We show that a database generated using compositions extracted from a partially stirred reactor configuration leads to performance comparable to the optimal case, wherein the database is comprised of compositions extracted directly from the LES/PDF simulation itself

Identifying space for mainstreaming multilingual pedagogies in European initial teacher education policies

This study sought to explore the ideological and implementational spaces for mainstreaming multilingual pedagogies (MPs) in initial teacher education (ITE) policies and curricula across the European Union. The concept of linguistically sensitive teaching (LST) was used as a lens to examine inclusive, equity-centred MPs in ITE. A multi-sited comparative case study was conducted to collect data in nine locations. As a result, a general trend of ideological spaces was observed for MPs in language-in-education policies at the European and (sub)national levels. However, this ideological space was not always implemented in ITE. As a second result, explicit mentions of MPs and LST were identified in the ITE curricula of seven sites, and in each of the nine cases, a potential space for implementation was observed. As a third result we found that the greatest potential for opening implementational spaces for MPs lies in courses that aim to develop general pedagogical and sociolinguistic knowledge as well as professional beliefs in future teachers. In conclusion, we contend that the linguistic ecology and the organisational structure of education systems (decentralisation) are factors that help explain the successful mainstreaming of MPs in ITE institutions

Whose action research is it? Promoting linguistically sensitive teacher education in Europe

This article examines the possibilities and challenges in turning a top-down action research project led by high-level public authorities into a shared and collaborative, multi-site and multi-professional bottom-up action research project. For this purpose, the article explores the initial stages of a European level action research project called ‘Linguistically Sensitive Teaching in All Classrooms’ that aimed to help teacher education systems better acknowledge linguistically diverse student populations in seven European countries. The analysis of the data sought to identify how to promote linguistically sensitive initial teacher education by incorporating reflection tasks into existing courses, and how to transform a top-down research project into a shared and collaborative bottom-up action project. The primary data consisted of 19 video-recorded online research meetings. Qualitative analysis was used to identify ‘critical moments’ in the data; these included a moment of major insight where transformation of project related ideas took place. The findings showed that linguistically sensitive teaching as a phenomenon is complex and the related terminology challenging to translate between languages and contexts. Furthermore, a European level action research requires negotiating a joint understanding of the roles of the participants and the individual perceptions of project ownership in each context. This suggests that a deeper understanding of the processes of participation and the partnerships involved in the action research may be as valuable as the actual reflection tools developed in the project in securing a systematic change towards linguistically sensitive teacher education

Linguistically sensitive teacher education : Toolkit for reflection tasks and action research

When all pupils are assured equal conditions, they can achieve educational success, regardless of their first language, culture, social background, origin, and age. The Erasmus+ project Linguistically sensitive teaching in all classrooms (Listiac) believes in supporting all teachers in becoming more linguistically sensitive to enable opportunities for equally successful schooling for all pupils in Europe. An important part of the process is to influence European initial teacher education curricula. The Listiac project believes that reflection about and awareness of linguistically sensitive teaching should be better integrated during all stages of initial teacher education. The reflection should be done by teacher educators when planning individual courses, practice periods and vision and profile, by student teachers when doing their practice periods and obligatory courses, as well as by in-service teachers when supervising the student teachers

A conceptual model of the flame stabilization mechanisms for a lifted Diesel-type flame based on direct numerical simulation and experiments

This work presents an analysis of the stabilization of diffusion flames created by the injection of fuel into hot air, as found in Diesel engines. It is based on experimental observations and uses a dedicated Direct Numerical Simulation (DNS) approach to construct a numerical setup, which reproduces the ignition features obtained experimentally. The resulting DNS data are then used to classify and analyze the events that allow the flame to stabilize at a certain Lift-Off Length (LOL) from the fuel injector. Both DNS and experiments reveal that this stabilization is intermittent: flame elements first auto-ignite before being convected downstream until another sudden auto-ignition event occurs closer to the fuel injector. The flame topologies associated to such events are discussed in detail using the DNS results, and a conceptual model summarizing the observation made is proposed. Results show that the main flame stabilization mechanism is auto-ignition. However, multiple reaction zone topologies, such as triple flames, are also observed at the periphery of the fuel jet helping the flame to stabilize by filling high-temperature burnt gases reservoirs localized at the periphery, which trigger auto-ignitions

Asymptotology of Chemical Reaction Networks

The concept of the limiting step is extended to the asymptotology of multiscale reaction networks. Complete theory for linear networks with well separated reaction rate constants is developed. We present algorithms for explicit approximations of eigenvalues and eigenvectors of kinetic matrix. Accuracy of estimates is proven. Performance of the algorithms is demonstrated on simple examples. Application of algorithms to nonlinear systems is discussed.Comment: 23 pages, 8 figures, 84 refs, Corrected Journal Versio

Influence of fuel properties on fundamental spray characteristics and soot emissions using different tailor-made fuels from biomass

This work evaluates the potential of some new biomass-derived fuels as candidates for compression ignition operation. Thus, fundamental spray characteristics related to fuel vaporization and fuel/air mixing process for 2-Methyltetrahydrofuran, Di-n-butyl ether and 1-octanol has been studied and compared with conventional EN590 Diesel fuel. For this purpose, OH⁄ chemiluminescence and shadowgraphy measurements in a high pressure chamber as well as 1D simulations with a spray model have been carried out at different operating conditions representative of the NEDC driving cycle. Finally, measured soot emissions in the single-cylinder engine were presented and discussed. Results from the high pressure chamber presented very good agreement in terms of liquid length and vapor penetration with simulation results. Thus, some analytical expressions related to macroscopic spray characteristics have been proposed and validated experimentally for all four fuels. Finally, the single-cylinder engine results confirmed the relevant role of soot formation on final emissions for 1-octanol and 2-MTHF. In addition, DNBE showed greater soot oxidation potential than diesel and other TMFB candidates.This work was performed as part of the Cluster of Excellence "Tailor-Made Fuels from Biomass", which is funded by the Excellence Initiative by the German federal and state governments. Simulation works have been partially funded by Spanish government under the grant "Jose Castillejo" (CAS12/000097).García Martínez, A.; Monsalve Serrano, J.; Heuser, B.; Jakob, M.; Kremer, F.; Pischinger, S. (2016). Influence of fuel properties on fundamental spray characteristics and soot emissions using different tailor-made fuels from biomass. Energy Conversion and Management. 108:243-254. https://doi.org/10.1016/j.enconman.2015.11.010S24325410