Multi-parameter determination in practical combustion systems by broadband high-speed absorption spectroscopy

• Applicant: Professor Dr.-Ing. Stefan Will
• Subject Area: Energy Process Engineering ; Technical Thermodynamics
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280430351

This project aims at the development and application of a novel sensitive high-speed absorption based measurement system for a comprehensive characterization of combustion processes. For the first time, the planned system allows for the simultaneous high-speed detection of temperature (via H2O-absorption lines) and important combustion intermediates (H2O2, C2H2) as well as main combustion products (H2O, CO2, CO) in a wide temperature and pressure range. Main parts are a supercontinuum light source and a high-speed near-infrared line-camera. The novel light source overcomes the limited spectral bandwidth of previous absorption based concepts. The line-detector is used as sensor in a highly resolving, modular spectrograph and allows for acquisition rates of up to 10 kHz. Because of the high spectral power density of the supercontinuum light source, the setup further facilitates the implementation of an optical cavity to extend the beam path within the measurement volume without a reduction of the detection rates.In the first phase of the project the measurement system will be built up and fundamentally characterized. Here, special focus is laid on the control of the linearity of the line detector as well as on the determination of the resolution, i.e. the instrumental function of the spectrograph. Further, the influence of additional partially reflective surfaces within the cavity with respect to the effective beam path will be quantified. Subsequently, an evaluation algorithm will be developed, based on calibration measurements, and the measurement system will be applied to a 1D-flat flame burner. Finally multi-parameter determination will be accomplished in a rapid compression machine (RCM) under IC engine conditions. In the RCM two-stage combustion characteristics of different surrogate fuels will be investigated under varied exhaust gas content and compression ratio. The temperature trace prior to and within the ignition process as well as the duration of the first phase combustion and the maximum temperature peak are important parameters for the further development of modern combustion concepts such as low temperature combustion (LTC).The newly developed measurement system will be applied to an optically accessible research engine in the second phase of the project. Additional focus will then be laid on the construction of a tomographic sensor applicable to measure cycle-resolved 2D-temperature fields in engines.

• DFG Programme: Research Grants