Experimental Study On The Fuel Spray Characteristics Of Stirling Engine

Stirling Engine has great application prospects because of its high efficiency and low emission performance. Especially, it has wide energy adaptability and excellent variation & noise characteristics. Under the support of NSFC(No. 5077608), the macroscopic & microscopic fuel spray characteristics of Stirling Engine were studied in this thesis.Spray testing bench was built firstly, and Pressure Swirl Injector was used in the experiment. Relations between injection pressure and oil flow rate were calibrated, then Stirling Engine’s fuel spray characteristics were studied, including the impacting of oil flow rate, back pressure, gas density, nozzle, and fuel’s physical properties on it.The mainly contents are as follows:(1) Macroscopic characteristics of fuel spray in Stirling Engine High speed filming technology was used to study time history of Stirling Engine’s spray. Fuel flow rate, back pressure, gas density, nozzle and fuel’s physical properties’impacts on spray’s macroscopic characteristics were studied and analyzed. The results showed that:①penetration and spray angle would increase with fuel flow rate’s increasing;②back pressure’s increase would cause penetration’s increase and spray angle’s decrease;③gas density’s increase would cause spray angle’s decrease, in equivalent pressure conditions, penetration and spray angle had little difference;④W-2 nozzle spray penetration was longer than W-1 nozzle, and its spray angle was smaller;⑤fuels with smaller viscosity had bigger spray angle and shorter penetration.(2) Particle size and distribution of the fuel spray tested by FAM FAM laser testing technology was used to analyze particle size and distribution, as well as the impact factions which including the oil flow rate, back pressure, gas density, nozzle and fuel’s physical properties’. The results showed that:①spray’s average particle size decreases with fuel flow rate’s increase;②spray’s average particle size decreases with back pressure’s increase;③spray’s average particle size was smaller in gas with higher density;④W-2 nozzle’s spray had smaller particle size than that of W-1 nozzle’s;⑤higher viscosity fuel’s particle size decreases with oil flow rate’s increase, while lower viscosity fuel’s particle size slightly increases;⑥spray’s particle size was smaller in positions near the nozzle’s axis than other positions in the chamber.(3) Flow field of the fuel spray tested by PIVPIV technology was used to analyze flow field characteristics of Stirling Engine’s spray, as well as the impact factions which including the fuel flow rate, back pressure, gas density, nozzle and fuel’s physical properties’. The result showed that:①particle’s moving speed increases with fuel flow rate’s increase;②particles velocities near the nozzle’s axis are higher than other positions’, and the flow field was not symmetrical, its symmetry would be improved with the oil flow rate’s increase;③particle velocities decrease with back pressure’s increase;④particle velocities in W-2 nozzle was higher and the velocity distribution was more uniform than that of W-1 nozzle’s.This research will provide supports for improving Stirling Engine’s combustion and emission performances, which has great theoretical and engineer application values.