Sampling Probe Influences on Temperature and Species Concentrations in Molecular Beam Mass Spectroscopic Investigations of Flat Premixed Low-pressure Flames

TLDR

The combustion chemistry of non‑conventional fuels under premixed conditions requires detailed species and temperature measurements, for which molecular‑beam mass spectrometry (MBMS) and optical diagnostics are routinely used, and recent advances such as synchrotron‑based MBMS have improved species identification, though the influence of sampling probes on these measurements remains debated. The study seeks to evaluate how different sampling configurations affect optical and MBMS measurements in flat premixed low‑pressure flames. The authors performed optical diagnostics and MBMS measurements on flat premixed low‑pressure flames using multiple sampling probe arrangements to assess their impact on species concentrations and temperature profiles.

Abstract

Abstract New operating regimes for engines and combustors and the advocated use of non-conventional transportation fuels demand investigation of the combustion chemistry of different classes of chemicals, especially under premixed conditions. Detailed species compositions during combustion are needed to estimate hazardous emissions, and models for their prediction must be validated for the intended combustion conditions.Molecular-beam mass spectrometry (MBMS) is a common technique to measure quantitative species concentrations in flames. It is widely employed to characterize the flame chemistry of laminar premixed combustion, and it has been complemented with optical measurements for the detection of a number of molecular species and radicals. Significant progress has been made in recent studies through the introduction of synchrotron-based MBMS instruments. They have improved the identification process by using tunable vacuum-ultraviolet radiation for photoionization of the species to be detected, and isomer-specific measurements are now almost routinely possible. Along with quantitative species measurements, the temperature profile is needed as input parameter for chemical kinetic modeling. It is usually determined either using thermocouples or laser spectroscopic techniques.It is an ongoing discussion how sampling probes affect these measurements, and how MBMS results can be compared to combustion modeling. The present article is intended to contribute to this discussion by providing optical and MBMS results obtained with several sampling configurations.