The research areas at RSM cover a multitude of problems. The test stands available in our laboratories are correspondingly diverse. Here, fluid-mechanical and thermochemical processes and phenomena are investigated by means of advanced laser-based measurement technology. In the following, all test benches operated at RSM are presented.

In a fully automated test rig, a synthetic exhaust gas is generated and passed through an DOC. Using different measuring techniques (e.g. FTIR, FID), the exhaust gas downstream of the catalyst is analyzed enabling to evaluate the catalyst performance under different exhaust gas conditions (composition and temperature). The test rig can be used for stationary measurements but also allows dynamic experiments to simulate real time driving cycles . The experimental investigations are assisted by numerical models, providing a deeper understanding of the underlying physical and chemical processes controlling the complex behavior of a DOC.

Picture: Michael Haas, RSM

The pressurized combustion chamber of RSM offers the possibility to examine combustion processes at elevated pressures. The core of the test stand is a pressure vessel which provides an enclosed environment at pressures of up to 10 bar. Quartz glass windows on three sides of the pressure vessel allow for optical access and enable the application of advanced optical measurement techniques. Due to its modular design, various experiments can be implemented to study different combustion systems and phenomena. The focus of previous experiments was on the investigation of the influence of effusion cooling air on a swirl-stabilized flame. Currently and in the future the test bench is used for flame-wall interaction (FWI) experiments which serve to investigate flame extinction under more practical conditions.

Basic fluid-mechanical and thermochemical phenomena during flame extinguishing are investigated at the flame-wall interaction burner. These include the formation of emissions. The test stand offers good optical accessibility so that the relevant phenomena can be recorded using advanced laser measurement techniques. This allows process parameters such as wall boundary layer flows, temperature distributions or the local concentrations of chemical species to be accurately and precisely measured, in some cases simultaneously. These experimental data form the basis for a deeper understanding of the process.

To observe and measure the thermochemical effects taking place within an SCR (selective catalytic reduction) system, a generic exhaust gas test bench was set up that aims for closing the gap between laboratory-scale spray chambers and real exhaust aftertreatment systems. In this test bench, temperatures between 20 °C and 450 °C and speeds between 2 m/s and 10 m/s can be set reproducibly. The flow guidance ensures a fully developed, turbulent flow in the measuring section. The measuring chamber allows optical access from four sides through integrated quartz glass panels.

In the test facility for Raman and Rayleigh spectroscopy, phenomena regarding the interaction of turbulence and chemistry are studied in a one-dimensional probe volume. The measurement technique uniquely enables the simultaneous quantitative determination of temperature and main species concentrations with a high temporal and spatial resolution. Subject of experiments are open and mostly turbulent flames under well defined boundary conditions. Besides an increased understanding of such flames, the gathered data can also be used to validate numerical models. So far, it has been applied widely on hydrogen and methane flames. Research targets are flames characterised by high Karlovitz numbers. Furthermore, molecularly more complex fuels, such as Ethanol, the synthetic fuel OME, as well as ammonia, come into focus. Therefore, the test rig has been expanded by a higher resolved Raman fuel channel. A large challenge is the adaptation of the technique, which is well-established for open flames, to phenomena of flame wall interaction.

Within the laminar flat flame burner of RSM, the combustion of particles such as biomass, conventional solid fuels or plastics is investigated with highly resolved high-speed laser diagnostics. For this purpose, the defined combustion atmosphere of a premixed methane flame is used to realize the ignition of particles in a laminar coflow with high heating rates.

The auto-ignition of different fuels under highly turbulent conditions is investigated experimentally at the microwave plasma heater (MWPH). To achieve a sufficiently high temperature in the oxygen-enriched coflow, a plasma is used which is stabilized with the aid of a microwave. Currently, ignition processes of biogas and biomass particles are investigated at the MWPH using ultra high-speed techniques.

The optically accessible research engine at RSM is used to study the fundamental physical processes of gasoline engines. The single-cylinder engine provides optical access via a piston window and glass cylinder. Laser optical diagnostics, e.g., laser-induced fluorescence, particle image velocimetry, and thermographic phosphors, are used to measure scalar and vector fields within the engine. This enables the investigation of phenomena such as spray flow interactions, flame-wall interactions, or early mixture formation up to ignition and flame propagation, and provides validation data for numerical simulations

The portable multi-species emission measurement system is based on tunable diode laser absorption spectroscopy (TDLAS) and is able to detect the species CO2, H2O, NH3, CH4, and H2CO in addition to the currently regulated emissions CO, NO, NO2. The measurement is performed in-situ, i.e. without sampling or gas conditioning directly at the end of the exhaust system. The system can be operated stationary at the test bench, but is also capable of mobile measurements such as RDE driving.

At this test stand, isocyanic acid is synthesized and absorption spectra are recorded as a basis for a spectral database. Measurements can be performed with a high-resolution FTIR as well as with TDLAS. This spectral database is the basis for quantitative in situ measurements of isocyanic acid in the context of SCR catalysis.

In order to reduce CO2 emissions from power plants in the future, new technologies are needed to provide clean electricity. With the solid fuel combustion chamber operated at RSM, an alternative combustion process of pulverized solid fuel, called “oxy-fuel”, is being investigated. In the oxy-fuel process, solid fuel (biomass) is burned in an atmosphere of recirculated exhaust gas and oxygen. This enables efficient CO2 separation (CCS/CCU) before the exhaust gases are released into the environment. Using advanced laser diagnostics (PIV/PTV, LIF, CARS, phosphor thermography, LII) the modified combustion process is investigated and numerical models are developed and validated to allow accurate combustion simulations in the future.

Droplet evaporation and species mixing under high pressures are quantitatively investigated at a pressure chamber in order to simulate processes in food chemistry, but also multiphase processes in rocket combustion chambers or injection processes in diesel engines. In particular, temperatures of the liquid and vapor phases as well as local mass fractions of binary mixtures are to be quantified. Laser-induced fluorescence, phosphorescence and Raman scattering are used for measurements.