| In modern aero-engines,aviation kerosene is usually used for cooling aircraft subsystem absorbing the waste heat,which make its temperatures rise up to 373~413K before entering the injector.While the fuel injection into the combustion chamber,the convective heat transfer of the diffuser outlet hightemperature airflow and the radiation of the high temperature gas in the main combustion zone further raise the fuel temperature in the fuel pipeline.And with the continuous development of the aero-engine,the pressure ratio of the compressor is increasing,the temperature of the inlet airflow of the combustor is further increased,and the heating effect of the fuel in the pipeline is even more prominent,which causes deposit formation in the pipeline and affects the normal work of the aeroengine.Therefore,the deposition formation is mainly caused by thermal oxidation reactions.And the characteristics of the coke due to thermal oxidation coking obtained can be used as theoretical guidelines to the design of the pipelines.In this paper,on the background of thermal protection of aero-engine injector,The experimental study on the thermal oxidation coking characteristics of RP-3 aviation kerosene was carried out and its variation with the flow and environmental parameters are summarized which support the design of the thermal protection scheme for aero-engine injector.Based on the experimental results of coking experiments at home and abroad,the experimental scheme was established based on the constant temperature experiment.A set of experimental Research system for autoxidation coking test bench was established.Experimental study on the autoxidation coking characteristics of RP-3 aviation kerosene was carried out.The influence of inlet temperature Tin,inlet velocity vin,inlet reynolds number Re,ambient temperature Ts and heating time ? on autoxidation coking characteristics of RP-3 aviation kerosene were analyzed.It was determined that the RP-3 fuel kerosene autoxidation coking critical wall temperature.The critical wall temperature of the autoxidation coking of RP-3 aviation kerosene is obtained,and the coking characteristics under static conditions are studied.In addition,the effects of four kinds of tubing materials on the autoxidation coking characteristics of RP-3 aviation kerosene are studied.Through the analysis of the experimental results obtained the following main conclusions: to improve the fuel inlet temperature Tin and ambient temperature Tw,fuel outlet temperature Tout is increased.The deposition amount of the coke increases first and then decreases,and the peak of the deposition amount appears in the middle and back of the test pipes.The coking amount along the test pipe and total deposition amount of the coke increase with the inlet temperature Tin increasing.The coking volume changes with the heating time nonlinearly.And the coking volume increases with the increase of ambient temperature Tw,and the peak point of coking along the road has a tendency to move forward.With the increase of the fuel inlet flow velocity vin,the coking volume along the road and the total coke volume decrease significantly.The influence of the Reynolds number Re on the thermal oxidation characteristics of fuel is various,which can affect the rate of chemical reaction and the physical diffusion of coke precursor.There is a balance between them.The critical wall temperature of coking thermal oxidation of RP-3 kerosene was obtained.When the fuel inlet flow velocity vin > 1m/s,the critical coking temperature Tc= 465 K.When the RP-3 aviation kerosene is stationary in the fuel pipeline,there will not be coking the wall temperature is lower than 423 K.And when the wall temperature will rise to 450 K,the deposition of the coke will be occurd.And the critical point of temperature is between 423 K and 450 K.The total coke volume in different materials is as follows: brass tube> 316 stainless steel tube> 304 stainless steel tube> 321 stainless steel tube. |
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