Kun Wang

Tianjin University | tju · State Key Laboratory of Engines

Soot particles with sulfur functional groups (SFGs) are one of the main concerns from shipping emissions, especially when they are produced from fuel combustion with high fuel sulfur content (FSC). The present study investigates the physicochemical characteristics of soot particles generated from different FSC fuels on a marine auxiliary diesel eng...

This paper studies the generation process and emission characteristics of soot from Marine diesel engine. On the basis of Particulate size mimic (PSM) detailed soot model, the parameters related to soot generation obtained from the reaction mechanism calculation of 3 surrogate of different carbon chain length: n-heptane, n-tetradecane and n-tetrade...

The synthetic base oil (SyBO) is the main component of lubricant oil, determining its basic physical and chemical properties, as well as impacting the pre-ignition, in-cylinder combustion and emission characteristics during the engine applications. Yet the involvement of SyBO in the engine combustion process is rarely investigated, primarily due to...

The objective of the present study was to investigate and optimize the multi-injection parameters that were able to match the diesel particulate filter (DPF) after-treatment system for reduction of particulate matter (PM) generated from diesel engines. Three representative multi-injection strategies, including main plus post-injection (designated a...

The primary objective of the present study was to investigate the impact of wall film on the combustion characteristics of premixed flames in internal combustion engines through the joint experimental and numerical techniques. The interaction between the premixed methane-air flame and n -dodecane film attached to the wall of a constant volume combu...

In the present study, a simplified modeling approach based on a two-step reaction scheme (TSRS) was developed to describe the high-temperature combustion chemistry of large hydrocarbon fuels. The characteristic reaction time scale analysis indicated a distinct two-step reaction property for the conversion of large hydrocarbon molecules. Along with...

The primary objective of the present study is to investigate the variations of soot particles’ oxidation reactivity along the components of the exhaust after-treatment system in a diesel engine and analyze its quantitative correlation with surface functional groups (SFGs) and graphitization degree. Soot particles generated from a 16-cylinder turboc...

With applying the direct injection strategy, it is inevitable to develop a liquid fuel wall film, which would significantly affect the combustion process afterward. In this work, the interactions between the premixed flame propagation and wall film in a confined vessel were investigated thoroughly. The methane-air premixed mixture was used to gener...

Propene and three butene isomers are mediate-sized foundational fuels during the conversion of large hydrocarbons, which play important roles in determining reactivities, combustion properties and emission behaviors of practical fuels. The objective of the present study was to develop a detailed foundational fuel chemistry mechanism to describe the...

The early injection is widely employed in advanced combustion technologies, which could substantially impact the engine particulate matter (PM) emissions. The primary objective of the present study was to investigate the effect of early injection on the diesel soot particle characteristics, so as to obtain comprehensive information when using a die...

Multi-injection is an effective strategy to control the NOx emission while maintaining the performance of combustion engines, however, it is difficult to balance emission and performance in practical operations. In this study, the Response Surface Methodology (RSM) was proposed to optimize them simultaneously. The combustion and performance of engi...

Low-speed two-stroke marine diesel engines dominate the modern global long-distance transportation market; with the increasingly stringent regulations, the combustion and emissions of these engines is gaining intense interest. The primary objective of the present study was to understand the effects of air-fuel mixing by pilot injection strategy on...

Flow reactors are commonly employed in investigations of the pyrolysis and oxidation chemistry of fuels. Typical flow reactors use either electrical heaters or vitiation heaters to provide the energy to preheat the reactants to the desired experimental conditions. The present study seeks to determine the impact of vitiation on flow reactor studies...

The objective of the present study was to understand how the lubricant-derived ash-loaded diesel particulate filter (DPF) impacted the soot oxidation reactivity during the regeneration process. Four major commercial lubricant additives (i.e. Ca, Zn-P, Ca-Zn-P, and Mo-P) were heated up in a muffle furnace to generate ash particles, which were mixed...

In this study, the surface functional groups types and concentrations, graphitization degree, and oxidation reactivity of exhaust soot samples generated by a heavy-duty engine when employing neat diesel and four base oil dosed mixtures as the fuel was compared. Fourier transform infrared (FTIR), Raman spectroscopy and Thermal gravimetric analyzer (...

The Hybrid Chemistry (HyChem) approach has been proposed previously for combustion chemistry modeling of real, liquid fuels of a distillate origin. In this work, the applicability of the HyChem approach is tested for single-component fuels using JP10 as the model fuel. The method remains the same: an experimentally constrained, lumped single-fuel m...

A Hybrid Chemistry (HyChem) approach has been recently developed for the modeling of real fuels; it incorporates a basic understanding about the combustion chemistry of multicomponent liquid fuels that overcomes some of the limitations of the conventional surrogate fuel approach. The present work extends this approach to modeling the combustion beh...

The molecular structures of hydrocarbon fuels are known to have a substantial impact on their combustion properties. However, the relationship between the fuel structure and thermal decomposition intermediate products, which determine the global combustion behaviors, is not as well known. In this study, four octane isomers, n-octane, 2,5-dimethylhe...

We propose and test an alternative approach to modeling high-temperature combustion chemistry of multicomponent real fuels. The hybrid chemistry (HyChem) approach decouples fuel pyrolysis from the oxidation of fuel pyrolysis products. The pyrolysis (or oxidative pyrolysis) process is modeled by seven lumped reaction steps in which the stoichiometri...

Real distillate fuels usually contain thousands of hydrocarbon components. Over a wide range of combustion conditions, large hydrocarbon molecules undergo thermal decomposition to form a small set of low molecular weight fragments. In the case of conventional petroleum-derived fuels, the composition variation of the decomposition products is washed...

Twenty reaction models published in five consecutive issues of Combustion and Flame in 2015 and 2016 were screened for the occurrence of collision limit violations. It was found that among the 20 models tested, 15 of them contain either considerable numbers of rate coefficients that exceed their respective collision limits or reactions exceeding th...

The objective of this study is to explore the impact of the molecular structure on the rate and product distribution during olefin pyrolysis. Particular focus is on characterizing the reaction pathways, leading to the formation of molecular weight growth species. Propene, the smallest olefin that can form allylic radicals, and the three butene isom...

In this work we introduce an unconventional approach to modeling the high-temperature combustion chemistry of multicomponent real fuels. The hybrid chemistry (HyChem) approach decouples fuel pyrolysis from the oxidation of fuel decomposition intermediates. The thermal decomposition and oxidative thermal decomposition processes are modeled by seven...

With increasing use of alternative fuels, approaches that can efficiently model their combustion chemistry are essential to facilitate their utilization. The hybrid chemistry (HyChem) method incorporates a basic understanding about the combustion chemistry of multicomponent liquid fuels that overcomes some of the limitations of the surrogate fuel a...

The hybrid chemistry modeling approach, termed HyChem, was used to explore the combustion chemistry of blended petroleum and bio-derived jet fuels. The pyrolysis products of conventional petroleum derived-fuels, such as Jet A, are dominated by ethylene and propene, whereas in many bio-derived fuels, such as alcohol to jet (ATJ) fuels, the fuel comp...

The pyrolysis of isobutene was investigated using a tubular flow reactor at an absolute pressure of ∼0.82 atm over a temperature range of 610–860 °C with residence times ranging from ∼0.5 to ∼2.4 s. The initial concentration of the fuel ranged from 5 to 50 mol%. These data were compared to the predictions of a fundamentally based detailed kinetic m...

Understanding the pyrolysis of ethane over an extended pressure range can help improve the understanding of the pressure dependence of pyrolysis of higher alkanes. For this work a variable pressure flow reactor was operated at 1073 K at pressures of 0.1 and 2.0 MPa in order to gain insight into the effect of pressure on the rate of ethane decomposi...

1-and 2-Butene pyrolysis experiments were performed using a tubular flow reactor at an absolute pressure of ∼0.82 atm over a temperature range of 535–810 °C with residence times ranging from ∼0.5– ∼2.4 s. The initial concentration of the fuel ranged from 5 to 50 mol%. These data were compared to the predictions of a fundamentally based detailed kin...

To evaluate the contribution of lubricating oil composition to engine emissions, two kinds of base oils were chosen to act as lubricating oil in a diesel engine. AVL gas analyzer was used to measure the gas emissions, and cooper grids were used to sample the particles. Post-processing software was used to analyze the size distribution, fractal dime...

The intramolecular ring closure reactions of unsaturated hydrocarbon radicals potentially play an important role for the formation of molecular weight growth species, especially during the pyrolysis and oxidation of alkenes under low to intermediate temperatures. In this work we investigated a series of intramolecular cycloaddition reactions of bot...

A series of intramolecular H-atom shift reactions of both alkenyl and allylic radicals were investigated by using CBS-QB3 electronic structure calculations. In the first set of reactions, an alkyl radical site was converted into an allylic radical site. In the second set, an allylic radical was converted into another allylic radical. The results ar...

The primary objective of this work is to develop an improved fundamentally-based mechanism that describes the molecular weight growth kinetics observed during propene pyrolysis. Earlier attempts to describe the kinetics in terms of theoretically plausible reactions generally underpredict the low temperature reactivity. To address this issue, propen...

The primary objective of this study is to develop an improved first-principle-based mechanism that describes the molecular weight growth (MWG) kinetics observed during ethane pyrolysis. A proper characterization of the kinetics of ethane pyrolysis is a prerequisite for any analysis of hydrocarbon pyrolysis and oxidation. An earlier model 1 accurate...

Hydrocarbons, whether derived from petroleum, natural gas, or alternative sources, will be the main energy source for the foreseeable future. In many conversion processes, such as solid oxide fuel cell operation or hot gas mixing upstream of steam reformers, hydrocarbon fuels might be exposed for sufficiently long times to temperatures between 500o...

The reactions of allylic radicals have the potential to play a critical role in molecular weight growth (MWG) kinetics during hydrocarbon oxidation and/or pyrolysis. Due to their stability (when compared to alkyl radicals), they can accumulate to relatively high concentrations. Thus, even though the rate coefficients for their various reactions are...

Intramolecular H-atom shift reactions of alkyl radicals and cycloaddition reactions of alkenyl radicals are two important reaction classes in hydrocarbon combustion and pyrolysis. In this work, we derive high-pressure rate estimation rules that are based on the results of electronic structure calculations at the CBS-QB3 level of theory combined wit...

Butene is the smallest alkene with isomeric structures (1-butene, 2-butene, and isobutene). The study of 1-C4H8 and 2-C4H8 pyrolysis kinetics allows analysis of the impact of the double bond location, while isobutene serves as a model compound for larger branched alkenes. Recent investigations on the combustion of butanol isomers , and larger alkan...

Resonantly-stabilized free radicals (RSFR) have the potential to play a critical role in molecular weight growth kinetics during hydrocarbon pyrolysis or oxidation. Due to their stability, RSFR can accumulate to relatively high concentrations and certain recombination reactions have been recognized as important pathways to growth. In this work, we...

Hydrocarbons, whether derived from petroleum, natural gas, or alternative sources, will be the main energy source for the foreseeable future. One of the critical issues involving reactions of hydrocarbon fuels is the production of molecular weight growth (MWG) species (e.g., deposits in pyrolysis or soot in combustion). Deposit or soot formation ca...

Resonantly-stabilized free radicals (RSFR) play an important role in the kinetics of molecular weight growth during hydrocarbon pyrolysis or oxidation. In pyrolysis, these radicals are readily formed by abstraction from olefins by hydrogen atoms or alkyl radicals. In general, hydrogen abstractions by RSFR from alkanes are quite slow since this reac...

Sci-Mix Poster

An unanswered question in propene pyrolysis is proper prediction of the low temperature kinetics. Earlier attempts to describe the kinetics in terms of theoretically plausible reactions generally underpredict the low temperature reactivity. To address this issue, propene pyrolysis experiments were performed at 575-875 °C with residence times of ~5,...

1-butene was selected as a model olefin to validate a kinetic model we developed to describe the molecular weight growth (MWG) reactions that occur during olefin pyrolysis.; Flow reactor experiments were performed on mixtures of 4%, 10% and 50% 1-butene diluted in nitrogen at 0.83 atm over a temperatures range of 550-750℃, with residence times appr...

As part of a larger study on the pyrolysis of light olefins, 1-butene pyrolysis was studied. Flow reactor experiments were performed on mixtures of 5%, 10% and 50% 1-C4H8 diluted in nitrogen at 0.83 atm from 550 to750℃. The residence times were ~1.0, 2.5 and 5 sec; fuel conversion ranged from virtually no reaction to ~97%. A significant amount of m...

It is essential to accurately predict the reactivity of hydrocarbons, as they will for the foreseeable future society’s main energy source. One major concern during hydrocarbon conversion is the production of molecular weight growth species (MWG). Pyrolysis of alkenes generally produces more MWG species than alkanes and therefore offers the opportu...

The effects of the geometry, arrangement and number of embedded rectangular barriers on the mixing performance for three types of wavy micro-channels were investigated by computational fluid dynamics (CFD) method. The mass transportation model based on the flow field was applied to simulate the mixing process, in terms of mixing snapshots and fluid...

Abstract：Basic concepts and principles of volume of fluid（VOF）in computational fluid dynamics （CFD）are briefly introduced. Current progress in modeling of velocity fields，generation and development of bubbles or microdroplets，impacts of film thickness near the wall，mass and heat transfer performance of Taylor flow in microchannels are summarized. F...

Abstract: Both specific design of structure and setting barriers inside the micro-channel are very convenient and rather efficient methods as to improve the mixing performance in a micro-mixer. In this study, computational fluid dynamics (CFD) was carried out on the investigation of three types of T-shaped wavy micro-channels with rectangular barri...