High Temperature Process Diagnostics

Future regulations for exhaust emissions will require further reduction of pollutants emitted by modern internal combustion engines. New, innovative engines as well as exhaust after-treatment techniques have to be developed and optimized to meet these requirements. Promising methods include Selective Catalytic Reduction (SCR) via injection of an ammonia-H2O solution and Exhaust Gas Recirculation (EGR).

Basic understanding of the general injection and vaporization processes, the process chemistry, and the near-wall reactive flows of these exhaust conditions (SCR, EGR) are needed to optimize pollutant minimization. Advanced and new diagnostics for determination of absolute species concentrations, reaction rates, film thickness parameters as well as spatial and temporal fluid development within the exhaust tract are required.

Research Focus and Future Developments

Exhaust sensor for various applications

The measurement of absorbing species such as ammonia (NH3) and water (H2O) greatly benefits from the use of direct, non-intrusive, probe-less, real-time absorption measurement techniques; the use of extractive techniques cannot provide the time-critical resolution required for proper analysis to understand the combustion and reaction dynamics of the exhaust after-treatment. Our research addresses development and application of innovative laser-based in-situ absorption measurement methods.

We will pursue narrow-linewidth diode lasers (DFB, DM, VCSEL, ICL, QCL) to extend laser absorption spectroscopy to the technologically interesting mid-infrared region. We will also investigate the use of broadband laser sources (Fourier Transform Infrared Spectrometer – FTIR, Super Continuum Light Source – SCLS) for absorption-based exhaust diagnostics. In cooperation with industrial partners, we will investigate the practicality of new laser technologies for the measurement of gas species concentrations, process temperatures, film thickness (as well as urea deposition on the walls), during different after-treatment procedures.

Recent improvements in laser technology will be used to significantly enhance the contactless diagnostic methods for current as well as future exhaust after-treatment systems.

The activities of HTPD group have a high potential for developing critically-needed multi-species measurement sensors to follow the spatial and temporal development of next-generation exhaust treatment systems.


Research fields

  • Laser-based trace gas diagnostics in combustion processes;
  • Spectroscopic evaluation models and algorithms;
  • Fluid diagnostics in engine exhaust systems;
  • Diagnostics in reactive flows;
  • Current applications:
    Internal combustion engines, exhaust after treatment, gas turbine, biomass combustion, nuclear safety, food processing …

Measurement techniques and methods

  • Tunable Diode Laser Absorption Spectroscopy (TDLAS);
  • Continuous Wave Cavity Ring-Down Spectroscopy (cw-CRDS);
  • SuperContinuum Laser Absorption Spectroscopy (SCLAS);
  • Fourier Transform Infrared Spectroscopy (FTIR);
  • Limited Data Tomography (LDT) and Linear Hyperspectral Absorption Tomography (LHAT)


  • Lecture: “Principles of measurement technique and data acquisition With LabVIEW”
  • Advanced Design Projects for Engineers – Measurement Sciences and Applications
  • Seminar: “Measurement methods in mechanical engineering research”
  • Bachelor and Master Theses

The HTPD research group is supported by

  • The Institute “Reactive Flows and Diagnostics”, Prof. Dr. Andreas Dreizler – link
  • UNICO program of the TU Darmstadt
  • Segula Deutschland GmbH
  • “Fritz und Margot Faudi foundation” (91, 100) – external link
  • Deutschen Forschungsgemeinschaft (TRR150, TRR129, WA2951/1-1) – external link
  • EURAMET/EMPIR (14IND11 HIT, 19ENV09 MetroPEMS) – external link