Chung K. Law

Reduction of large combustion mechanisms is usually conducted based on the detection and elimination of redundant species and reactions. Reaction elimination methods are mostly based on sensitivity analysis, which can provide insight into the kinetic system, while species elimination methods are more efficient. In this work, the species‐targeted local sensitivity analysis (STLSA) method is proposed to evaluate the importance of species and eliminate non‐crucial species and their related reactions to simplify kinetic models. This paper comprehensively evaluates the effectiveness of STLSA across various combustion scenarios, including high and low‐temperature ignition and laminar flame speed, using diverse mechanisms like USC Mech II, JetSurf 1.0, POLIMI_TOT_1412, NUIGMech1.1 and so on. Comparisons with graph‐based methods, such as DRG and DRGEP, highlight STLSA's superior efficiency and …

In this work, the explosion limits of three different fuels: hydrogen (H2), propane (C3H8, C3), and diethyl ether (DEE, C2H5OC2H5, C4), are investigated based on detailed chemical kinetics. The results reveal that the explosion limit of H2single bondO2 exhibits the typical Z-shape, while C3H8single bondO2 exhibits a single-NTC response, and DEE-O2 displays a double-NTC response. Sensitivity analysis indicates that the appearance of the NTC response in both the C3 and DEE fuels is intricately linked to low-temperature reaction paths. Moreover, the extents of the NTC responses are comparable for these two fuels with similar low-temperature reaction paths, but operate under different temperature conditions. Specifically, the double-NTC response observed in DEE is attributed to its primary Csingle bondH and Csingle bondO bonds, generating C4 and C2 radicals. The oxygen addition and the subsequent …

To minimize the uncertainty of the parameters in combustion kinetics models, Bayesian methods are commonly used for uncertainty constraints based on experimental data. With the rapid and substantial growth of experimental data, using all the experimental data for optimization is not only redundant and time-consuming, but it could also lead to data consistency problems. In this work, the global sensitivity-based affinity propagation method (GSAP) is proposed to cluster experimental datasets and to select representative experimental conditions. Specifically, the global sensitivity coefficient is first obtained through an analysis to characterize the sources of uncertainty in the kinetic model under different experimental conditions. The similarity coefficient, which is defined based on the global sensitivity, measures the resemblance between two experimental conditions. By exchanging messages calculated from similarity …

This work studies the real gas effects on the autoignition of hydrocarbon fuels under high pressures, using normal dodecane (n-dodecane) as the representative fuel and the Redlich–Kwong equation of state (EoS) as the real gas description. It is demonstrated that the real gas description yields a shorter ignition delay time (IDT) compared with the ideal gas description, especially in low-temperature regimes which could encompass the negative temperature coefficient (NTC) phenomena and has a stronger dependence on the molecular volume than the attractive potential. The study further shows that high pressure facilitates low-temperature reaction pathways, where the compressibility factors of key reactants contribute to real gas effects. Moreover, the results suggest that accounting for real gas behavior leads to an increase in the formation of polycyclic aromatic hydrocarbons (PAHs), which, in turn, promotes soot …

Blue whirls are newly discovered blue rotating flames transitioned from fire whirls generated on liquid fuel surfaces. Compared with the traditional fire whirls, blue whirls have a distinct flame structure and are almost soot-free. Studies of the blue whirl are expected to promote the development of clean combustion theory and technology. In this paper, we numerically and theoretically investigate the lifting process of fire whirls and blue whirls, and then discuss their structure and transition mechanisms. In contrast to the explanations in the literature, it is found that blue whirls can be created without the occurrence of bubble-type vortex breakdown in the rotating flow. The blue whirl can be considered as a special form of lifted fire whirl with a considerable liftoff distance and without being blown out. According to the simulation, both blue whirls and fire whirls have the typical triple-flame structure. The unique structure of blue …

SAU-HAI LAM — Princeton University Skip to main navigation Skip to search Skip to main content Princeton University Home Princeton University Logo Help & FAQ Home Profiles Research units Facilities Projects Research output Search by expertise, name or affiliation SAU-HAI LAM Chung K. Law, Richard B. Miles, Alexander Smits Mechanical & Aerospace Engineering High Meadows Environmental Institute Princeton Materials Institute Research output: Chapter in Book/Report/Conference proceeding › Chapter Overview Fingerprint Original language English (US) Title of host publication Memorial Tributes Subtitle of host publication Volume 25 Publisher National Academies Press Pages 280-285 Number of pages 6 Volume 25 ISBN (Electronic) 9780309696531 State Published - Jan 1 2023 All Science Journal Classification (ASJC) codes Arts and Humanities(all) Other files and links Link to publication in Scopus …

We present a simple optical capability for generating spatially resolved chemical concentration maps of mixing fluids using a chemically sensitive dye, 1-hydroxy-3, 6, 8-pyrenetrisulfonic acid, detected by planar laser induced fluorescence. To demonstrate an application of this capability, we investigate the collision and mixing of a pair of microdroplets in air. The two microdroplets are composed of different fluids, methanol and water, with the dye initially in the methanol droplet. When the droplets collide and mixing process develops, the fluorescence of the dye shifts from blue to green as the solvent environment changes. A series of spectral-temporal images of the collision and subsequent mixing are recorded, from which we extract the distribution of the two intermixing droplet species reflected in the spatially resolved dye spectra. Images reveal material transfer between droplets in both coalescing and non …

Liquid clouds (sprays) are commonly encountered in nature and industrial applications, where droplets are subject to complex interactions. In this paper, an extended unit cell model is proposed to analyze the evaporation and autoignition of monodisperse, single-component, and quiescent droplet clouds. The extended model incorporates the transient development of the evaporating boundary layer attached to the droplet surface. Due to the inclusion of this gas-phase transient effect, the current theory can be applied to both dilute and dense clouds across a wide range of ambient pressures. In the absence of chemical reactions, the effects of multiple parameters, such as droplet spacing and ambient pressure, on the evaporation rate and lifetime of droplets are examined. The critical condition for fuel vapor saturation in the gas phase is re-obtained. Based on this, we further investigate the autoignition of droplet …