A rapid compression machine coupled with time-resolved molecular beam mass spectrometry for gas-phase kinetics studies.

Abstract

Rapid compression machines (RCMs) are used to simulate a single stroke of an internal combustion engine. After a high-speed compression process, a high-pressure and low-to-intermediate temperature condition can be obtained, under which ignition processes are usually studied. With the help of different diagnostic methods, the detailed speciation information of the ignition process can be quantified. In this study, the molecular beam mass spectrometry (MBMS) diagnostic method was applied on an RCM to realize time-resolved concentration profile measurements. To realize the combination between RCM and MBMS, particle dampers were adopted to suppress the vibrations of the RCM, and a novel flexible interface was designed to maintain a high vacuum, which ensured the safe and effective operation of a high-repetition-rate time-of-flight mass spectrometer (HRR-TOF-MS). The detailed configuration of this diagnostic method is presented, and the data acquisition system and data analysis method are described. The arrangement was validated through the investigation of the well-studied decomposition of 1,3,5-trioxane at temperatures between 697 and 777K at 10 bars. The measured concentration profiles of 1,3,5-trioxane and formaldehyde were in good agreement with previous experimental and theoretical calculation results. The experimental results showed that the newly developed RCM coupled with the HRR-TOF-MS has advantages in time-resolved speciation measurements at low-to-intermediate temperatures and high pressures, and it can be applied in low-temperature combustion chemical kinetics studies.