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

• Final Report Year: 2021

Final Report Abstract

The main objective of this research project was the development of a sensitive, broadband high-speed absorption spectroscopy measurement system and its use for multi-parameter detection in combustion systems. This goal was fully achieved. A fibre-coupled and transportable high-speed near-infrared spectrometer with a spectral bandwidth of nearly 300 nm and a frame rate of up to 76 kHz was developed, set up and fully characterised. With the measuring system, it is thus possible to investigate combustion processes in a wide pressure and temperature range. In particular, it was possible, among other things, to simultaneously determine the temperature and mass fraction traces of water, methane and carbon dioxide in a Rapid Compression Expansion Machine (RCEM). Preliminary investigations on a stationary high-pressure calibration cell and a high-temperature, high- pressure flow cell provided important insights into the validity of the spectroscopic databases HITEMP and HITRAN used for the evaluation of measurement data. Because these databases have their origins also in atmospheric research significant measurement uncertainties occur here with increasing pressure for individual gas species. Depending on the gas species, this affects the measurement accuracy of the mass fractions in particular, but much less their precision. In the RCEM experiments, the temperature and mass fraction traces of H2O, CH4 and CO2 could be resolved in time at a detection rate of 40 kHz. The temperature measurement precision reached values of less than 5 K and could thus be improved by a factor of almost 10 compared to earlier RCEM combustion experiments. Comparable multi-species measurements based on a single laser light source and a single spectrometer are currently not known. Similar measurement techniques (e.g. frequency comb spectroscopy) have so far achieved similar measurement precision in an RCM using CH4 absorption, but with a temporal resolution that is about 28 times worse. In addition, the single-mode fibre coupling proved to be a unique selling point: in contrast to the generally used multi-mode fibre coupling, no mode noise is induced here, and in addition the fibre connection generally allows an almost independent placement of the measurement technology to the measurement object. A path extension to improve the signal-to-noise ratio and sensitivity could be realised by an external Herriott multipass cell, which proved to be stable against beam deflections due to the occurring strong refractive index gradients in the RCEM combustion experiments. Further investigations with respect to high-pressure database uncertainties for selected gas species represent only one possible future field of application. For example, the investigation of alternative fuels and combustion processes in the RCEM or on experimental burners can build directly on the current measurement system. Further possible applications arise generally in the investigation of reactive flows, where simultaneous high-speed measurement of temperature and species concentrations is required.

Publications

• Influence of Different Spectroscopic Line Lists on the Multiparameter Determination by Supercontinuum Absorption Spectroscopy at IC Engine Relevant Conditions,“ 8th European Combustion Meeting (Dubrovnik, 18. - 21. April 2017)
  Fendt P., Werblinski T., Zigan L., Will S.
  
• „High-speed combustion diagnostics in a rapid compression machine by broadband supercontinuum absorption spectroscopy,“ Applied Optics 56 (2017), S. 4443-4453
  Werblinski T., Fendt P., Zigan L., Will S.
  
• „Multiparameter correlation and uncertainty analysis for a high-speed near-infrared broadband absorption spectrometer,“ Sensors Day 2017 (Cambridge (UK), 20. Oktober 2017)
  Fendt P., Werblinski T., Kämmerle S., Zigan L., Will S.
  
• „Mid-Infrared Supercontinuum based Rotational-Vibrational Broadband Absorption Spectroscopy,“ 37th International Symposium on Combustion (Dublin, 29. Juli - 3. August 2018)
  Fendt P., Werblinski T., Zigan L., Will S.
  
• „Investigation of the chemical stability of the laser-induced fluorescence tracer 1-methylnaphthalene at IC engine relevant conditions by supercontinuum absorption spectroscopy,“ 9th European Combustion Meeting (ECM 2019) (Lissabon, 14. – 17. April 2019)
  Fendt P., Retzer U., Ulrich H., Zigan L., Will S.
  
• „Supercontinuum absorption spectroscopy: Theory, optical design and application for high-speed multiparameter diagnostics,“ International Conference on Advanced Optical Technologies (Erlangen, 13. - 15. März 2019)
  Fendt P., Zigan L., Will S.
  
• „Stability Analysis of the Fluorescent Tracer 1- Methylnaphthalene for IC Engine Applications by Supercontinuum Laser Absorption Spectroscopy,“ Sensors 20 (2020)
  Fendt P., Retzer U., Ulrich H., Will S., Zigan L.
  
• „Herriott cell enhanced SMF-coupled multi-scalar combustion diagnostics in a rapid compression expansion machine supercontinuum laser absorption spectroscopy,“ Optics Express (2021)
  Fendt P., Brandl M., Peter A., Zigan L., Will S.