Preparation Of Functional Hyperbranched Polymers And Their Regulations On Thermo-Chemical Processes Of Hydrocarhon Fuels

Thermal management has become an outstanding aspect for the high flight of supersonic/hypersonic aircrafts.The application of endothermic hydrocarbon fuels(EHFs)that serve as both propellant and coolant is an important issue to solve this problem.In the practical processes,the heat sink enhancement,coke inhibition and combustion promotion of EHFs are always the prominent pursuances.In this work,designing polymeric additives with unique hyperbranched structure and adequate degree of polymerization for EHFs is considered as a novel approach.Several kinds of functional hyperbranched polymers are developed,and their regulation performances on the thermochemical process of EHFs,including thermal cracking,coking and combustion,are investigated in detail.The results are expected to provide valuable proofs for the application of hyperbranched polymers in EHFs.The main contents and results are summarized as follows:The hyperbranched polyglycerol(HPG)is developed as "macroinitiator" to promote the thermal cracking and heat sink of hydrocarbon fuels.HPG is synthesized via anionic ring-opening polymerization.Fuel-soluble products,palmitoyl-hyperbranched polyglycerol(PHPG)and dodecyl-modified hyperbranched polyglycerol(DSHPG),are obtained by the treatement with palmitoyl chloride or"thiol-ene" reaction.A paraffin-based fuel is chosen for the investigation of the cracking promotion on hydrocarbons in the presence of PHPG in a batch reactor.The conversion and gas productivity improvements infer that PHPG has a cracking promotion effect on hydrocarbon fuels.Cracking processes of tridecane and a kerosene-based fuel Kerosene-1 with the existence of PHPG are then performed under supercritical conditions(3.5 MPa,600-720 ?).It is shown that PHPG can promote the cracking of these fuels with significant improvements of the conversion,gas yield and heat sink.Furthermore,the dissolution-aggregation behavior and upper critical solution temperatures of PHPG in hydrocarbon fuels are investigated.n-Alcohols are applied as cosurfactants to improve the solubility of PHPG in hydrocarbon fuels.With the addition of alcohols,not only the solubility of PHPG in hydrocarbon fuels is improved significantly,but also the heat sink of each fuel is further raised to a higher value.The hyperbranched poly(amido-amine)(PAAMAM)is developed as another"macroinitiator" to promote the thermal cracking and heat sink of hydrocarbon fuels.PAMAM is reacted with palmitoyl chloride to build a lipophilic shell on the hydrophilic core,and an amphiphilic product palmitoyl-hyperbranched poly(amido-amine)(PPAMAM)which is well dissolved in hydrocarbon fuels is obtained.Thermal cracking processes of methylcyclohexane(MCH)and Kerosene-1 at 600?720 ? with the addition of PPAMAM are carried out under the pressure of 3.5 MPa.Significant improvements of the conversion,gas yield and the heat sink of MCH and Kerosene-1 with PPAMAM are observed,which confirm the effective cracking enhancement of PPAMAM in endothermic hydrocarbon fuels.Based on the mechanism of coke formation,a sulfur-contained hyperbranched copolymer,SHPGMA,is developed as a coke inhibitor for hydrocarbon fuels.SHPGMA is synthesized via the reversible addition-fragmentation chain transfer(RAFT)polymerization.The effect of SHPGMA on the cracking and coking of tridecane is investigated.It follows that the conversion,gas yield and the amount of coke are declined in the presence of SHPGMA.With the addition of SHPGMA,the amount of filamentous cokes on the tube wall are reduced significantly and the granular cokes become the major.Moreover,PHPG and SHPGMA are added into a Kerosene-2 to study the cooperation effect of these two hyperbranched polymers on hydrocarbon fuels.It is shown that the heat sink and cracking smoothness of PHPG-contained hydrocarbons are improved with the cooperation of SHPGMA.The comparison about the cracking products and heat sinks can further confirm the coking inhibition effect of SHPGMA on hydrocarbon fuels.The premixed laminar combustion performances including Markstein length,flame stretch and laminar flame speed for several hydrocarbon fuels have been measured via using constant volume combustion bomb.The effects of three macroinitiators(PHPG,DSHPG and PPAMAM)on combustion characteristics of the Kerosene-1 and JP-10 are investigated in a bomb calorimeter under oxygen-poor conditions.It is shown that these macroinitiators affect the buring velocity at the beginning of ignition,and the effect strongly depends on the addition quantity of macroinitiators.With the addition quantity of 1.0 wt%PHPG,DSHPG or PPAMAM,the burning velocities of Kerosene-1 and JP-10 are observed to be promoted significantly.