| In the moderm society,combustion of fossil fuel is still the major energy source.Increasing the combustion efficiency and decreasing the pollution of combustion become the basic task and academic obj ect of combustion science in new period.Since the 21St centery,airplanes become the more and more important vehicles which use the combustion of aviation fuel as the mahjor power source.Thus,it is very important to study the combustion characters of aviation fuels.Aviation fuels are the most widely used fossil fuels in the recent years,and surrogate fuel is the simplified(on the physical and chemical level)aviation fuels based on the research requirement.Recently,Reasearchers mostly use surrogate fuels on the combustion character studies for aviation fuels.In the studies of the past decades,many components,such as toluene,n-propylbenzene,and n-dodecane are used as the maj or components of surrogate fuel and deeply studied.In China,RP-3 jet fuel is the most widely used aviation fuel,which consists of 55%vol.paraffins,5%vol.aromatics,and 40%vol.naphthenes.This paper aims to study the combustion characters of RP-3 jet fuel based on studying the RP-3 surrogate fuel.Firstly,this paper introduces the pollutants and hazards of the fossil fuel combustion processes,and illuminates the necessity of the combustion characters study of aviation fuels and the combustion efficiency and pollution controlling.Reveals the maj or types of aviation fuels used in the world,and gives out a review of the reported studies on these jet fuels.According to these studies,this paper proposes a surrogate fuel,consists of 66.2%vol.n-dodecane,18.0%vol.1,3,5-trimethylcyclohexane,and 15.8%vol.n-propylbenzene,for the combustion characters study of RP-3 jet fuel.Based on the components of this surrogate fuel,this paper reviews the reported combustion kinetic studies of 1,3,5-trimethylcyclohexane,and n-propylbenzene,and aims to study RP-3 jet and surrogate fuels based on the combustion chemical kinetic study of single component of surrogate fuel.Secondly,this paper introduces the experimental systems,kinetic modeling methods,and quantum chemistry computing methods used in the research processes.Experimental systems include four parts:low temperature oxidation system,flame propagation velocity measurement system,shock tube ignition delay measurement system,and ordinary/low pressure pyrolysis system.These four systems are described in detail individually,especially for low temperature oxidation system.The history of development of Chemkin software is presented firstly to introduce the main software used in the recent work.The chemical kinetics mechanism,thermodynamic data,and transport data profiles,which are the necessary files for Chemkin,are described briefly.Then the definitions and significances of sensitivity analyses and rate-of-production(ROP)analyses are presented.The last section of this part gives out a brief introduction of quantum chemistry computing methods and the applications.Thirdly,this paper investigates the combustion chemistry kinetic of n-propylbenzene,the low temperature oxidation experiment,flame propagation velocity measurements,and shock tube ignition delay time measurements are performed.There are 25 species detected in the low temperature oxidation experiment by using GCand GC-MS,including six newly detected species:1-propenylbenzene,2-propenylbenzene,methylstyrene,indene,naphthalene,and benzofuran.A chemical kinetic mechanism consists of 292 species and 1919 reactions is established based on the reported acetylene core mechanism and updated rate constants which come from the quantum chemistry computing.Then the mechanism is validated against the measurements of flame propagation velocity and shock tube ignition delay time.The mechanism could reasonablely predict the experimental results of the three kinds of experiments of n-propylbenzene.Based on this mechanism,this paper performs ROP and sensitivity analyses for n-propylbenzene under wide range of pressure,equivalence ratio,and temperature.The results shows that n-propylbenzene mostly consumes through H-ion reactions on propyl during combustion,and yields to the major intermediates like toluene and styrene.At last,this paper establishes a universal mechanism based on n-propylbenzene mechanism and other presented mechanisms,which could predict the combustion processes of four C9H12 aromatic fuels.After that,this paper investigates the combustion chemistry kinetic of 1,2,4-trimethylcyclohexane.The low temperature oxidation experiment and pyrolysis experiment is performed.Large amounts of light hydrocarbon and a small amount of aromatic intermediates are detected in the oxidation experiment,and the light hydrocarbon intermediates are also detedted in the pyrolysis experiment.A chemical kinetic mechanism consists of 533 species and 3184 reactions is established based on estimations and quantum chemistry computing.The mechanism could successfully predict the measurements of oxidation and pyrolysis experiments.The ROP and sensitivity analyses are performed,which reveal that trimethylcyclhexane consums through H-abstraction reactions on nine different positions,and these reactions have similar significance for trimethylcyclhexane consumption.This study is the first study of trimethylcyclhexane around the word,and could lay the foundation for the study of surrogate fuel which has a component as trimethylcyclhexane.Then,this paper investigates the combustion chemistry kinetic of the three components surrogate fuel(66.2%vol.n-dodecane,18.0%vol.1,3,5-trimethylcyclohexane,and 15.8%vol.n-propylbenzene).The low temperature oxidation experiment,flame propagation velocity measurements,and shock tube ignition delay time measurements are performed.A chemical kinetic mechanism consists of 430 species and 2859 reactions is established based on the two mechanisms presented in the above two parts,and a reported n-dodecane mechanism.This mechanism could reasonablely predict the mole fractions,flame speeds and ignition delay times measured in the experaiments.The ROP and sensitivity analyses reveal that n-dodecane leads the consumption of the surrogate fuel,especially in the negative temperature coefficient(NTC)region.Oxidaiton of n-dodecane in NTC region could generates large amounts of radicals and lead slight oxidation of n-propylbenzene at low temperature(around 575 K).At last,this paper studies the oxidation of RP-3 jet fuel.The low temperature oxidation experiment is performed under p= 1 atm,?=2.0,T=575-1100 K.Online GC and GC-MS are used for measuring.The results show that the components of RP-3 jet fuel are similar to the surrogate fuel,which confirms the applicability of surrogate fuel.The oxidation processes of these two fuels are similar,and the surrogate mechanism could successfully predict the oxidaiotn process of RP-3 jet fuel.In conclution,this paper studies the combustion characters of n-propylbenzene,1,2,4-trimethylcyclohexane,RP-3 surrogate fuel,and RP-3 jet fuel.Experiments of low temperature oxidation,flame propagation velocity measurement,shock tube ignition delay measurement,and ordinary/low pressure pyrolysis are performed.Based on the quantum chemistry computing,mechanisms of n-propylbenzene,C9H12 aromatics,1,2,4-trimethylcyclohexane,and surrogate fuel are established in a logical order.These mechanisms could successfully predict the combustion processes of the corresponding fuels,including oxidation,pyrolysis,flame speed,and ignition delay time measurements.The experimental and modeling results reveal that the surrogate mechanism has good universality and accuracy on the RP-3 jet fuel prediction.These results give significant promoting effect on the RP-3 combustion studies,especially for reduction of pollutants emission,increasement of combustion efficiency,and development of low temperature auto-ignition devices. |
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