A. Kobiera

Influence of Density Variation on One-Dimensional Modeling of Exhaust Assisted Catalytic Fuel Reforming

Exhaust gas recirculation has become commonplace within the automobile industry to reduce nitrogen oxide emissions because of its ability to lower the combustion temperature. However, it leads to an increase of particulate matter and degradation in fuel economy. One possible avenue for recovering this efficiency is to use exhaust assisted fuel reforming (EAFR) to generate hydrogen by catalytic means using injected fuel and exhaust and add it to the inlet mixture. Adding hydrogen in this manner has shown an increase in combustion stability and efficiency of the engine while reducing particulate matter production. Many classical works use incompressible fluid flow models in order to simulate the reactive flow in monolithic catalyst. However, such models are not appropriate in the case of EAFR, where exothermic reactions cause a large increase in the temperature and consequently in density. To simulate a catalyst undergoing EAFR reactions, a compressible flow solver was used in order to take into account the changes in density. The presented results show the importance of using proper gas dynamics and heat transfer for modeling a flow with catalytic reactions of high exothermicity.

Numerical tools for three dimensional simulations of the rotating detonation engine in complex geometries

This paper describes the development of a computational code REFLOPS USG (REactive FLOw solver for Propulsion Systems on UnStructured Grids) based on the Favre averaged Navier-Stokes equations with chemical reactions for semi-ideal multicomponent gas to predict the structure and dynamics of three-dimensional unsteady detonation as it occurs in the Rotating Detonation Engine (RDE). This work provides an overview of second order accurate in time and space finite volume method applied to conservation equations and its implementation on unstructured self-adaptive tetrahedral or hexahedral three-dimensional cell-centred meshes. The inviscid fluxes are given by the Riemann solver and stabilization is ensured by the proper limiters inherited from the TVD theory or gradient based limiters. The stiff equations of chemical kinetics are solved by use of implicit DVODE (Double precision Variablecoefficient Ordinary Differential Equation solver, with fixed-leading-coefficient implementation) routine or by explicit Chemeq2 routine. Additional improvements are incorporated into the code such as parallelization in OpenMP and implementation of NVIDIA CUDA technology. REFLOPS USG has become a fundamental numerical tool in the research of RDE at the Institute of Aviation in Warsaw, in frame of Innovative Economy project UDA-POIG.01.03.01-14-071 ‘Turbine engine with detonation combustion chamber’ supported by EU and Ministry of Regional Development, Poland. The simulations presented in this paper are based on inviscid or viscous multicomponent semi-ideal gas flow with chemical reactions. Due to high computational costs only simple chemical reaction mechanisms are used here.

THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF THE COMBUSTION CHAMBER OF THE ROTATING DETONATION ENGINE

From 2010 Warsaw University of Technology (WUT) and Institute of Aviation (IoA) jointly implement the project under the Innovative Economy Operational Programme entitled ‘Turbine engine with detonation combustion chamber’. The goal of the project is to replace the combustion chamber of turboshaft engine GTD-350 with an annular detonation chamber. During the project, the numerical group that aims to develop computer code allowing researchers to simulate investigated processes has been established. Simulations provide wide range of parameters that are hardly available from experimental results and enable better understanding of investigated processes. Simulations may be also considered as a cheap alternative for experiments, especially when testing geometrical optimizations. In this paper the analysis of simulation results of the combustion chamber of the Rotating Detonation Engine (RDE) investigated at the IoA in Warsaw is presented. Primarily, REFLOPS USG which has become a fundamental numerical tool in the research of the RDE at the IoA is briefly described and governing equations and numerical methods used are shortly presented. Some aspects of numerical simulations of the RDE, related to selection of combustion mechanism, and an initiation of rotating detonation are provided. Secondly, results of simulations of inviscid gas with numerical injectors of hydrogen are compared with available experimental results. Three different wave patterns are identified in numerical solution and briefly described. Results of simulations are compared to experimental results in combustion chamber. Results presented in this paper are part of the project UDA-POIG.01.03.01-14-071 ‘Turbine engine with detonation combustion chamber’ supported by EU and Ministry of Regional Development, Poland.

Report on the implementation of the POIG project „turbine engine with a detonation combustion chamber”

This article contains a description of the work carried out under the UDA-POIG 01.03.01-14-071/09-10 project titled “A turbine engine with a detonation chamber”. The work carried out during the project involved 14 construction, research and calculation tasks. Various research stands designed to analyse the process of mixture formation, initiation of detonation and research of rotating detonation in combustion chambers were constructed. Test stand for examining a turboshaft engine with detonation combustion chamber was built. Those test stands allowed powering the combustion chambers and the engine with both liquid and gaseous fuels, simultaneously or separately. At the same time, REFLOPS software, which could calculate the propagation of a detonation wave was created, and used in the design of further versions of combustion chambers. Data from the experiments was used to verify the calculations and models created in the mentioned software. GTD-350 engine was used as the base; the structure of which (combustion chamber situated outside the turbine-compressor unit) facilitated modifying the shape of the detonation combustion chamber. During the research, great emphasis was placed on the safety of researchers. Working with hydrogen in high temperatures and JET-A1 fuel, which was additionally heated, and the usage of the oxy-acetylene detonators forced extreme caution, and full compliance with developed procedures. The project was divided into 14 tasks that were often conducted simultaneously in a 20-person team implementing the project. The work was completed by performing comparative studies between conventional engine with deflagration combustion chamber, and modified engine with a detonation combustion chamber. During the completion of the project, it was the first working demonstrator engine with detonation combustion chamber in the world.

Innovative Resistojet Propulsion System—Use in Robotic Space Platforms

This paper addresses the problem of precise satellite manoeuvres and possibility of using resistojet as an effective element of a positioning system. The high demands of precision and reliability make the simplicity of any such system one of its most important features. In many missions, electrothermal propulsion is considered to be a good solution, but high power levels are required to improve the working gas parameters. Resistojet, designed and built in Warsaw University of Technology, with power supplied by supercapacitors can fulfil those requirements. The Simulation Tool for Space Robotics developed at the Space Research Centre of the Polish Academy of Sciences demonstrates the possibility of predicting satellite movement after a thruster pulse. It will enable precise adjustments to be made to resistojet performance to meet the demands of particular mission and tasks. Cooperation between the Space Research Centre of the Polish Academy of Sciences and Warsaw University of Technology in research on use of the resistojet in space robotics, and common experimentation using an air-bearing table is planned for the near future.

Assessment of various models of scalar dissipation rate by use of DNS of a counterflow flame

The basic idea of the flamelet model is to represent turbulent flames as an ensemble of laminar flamelets, which are described by one‐dimensional transport equation. The key parameter appearing in the flamelet equation is the conditional scalar dissipation rate, which is usually modeled as a function of the mixture fraction variable in various forms. In this study, the accuracy and validity of the existing models are assessed by using direct numerical simulation data for turbulent counterflow flames. Post‐processing and filtering of the data allowed a comparison of four models for the scalar dissipation rate. It was found that neither model gives satisfactory accuracy in predicting the mean scalar dissipation rate. Once the analysis was limited to points close to stoichiometric compositions, the correlation remained qualitatively the same with significant scatter. We can assume therefore, that the errors are not coupled with the flame. On the other hand, the turbulence parameters used in the models seem t...