Experimental Study On The Spray Atomization And Combustion 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. The atomization of fuel, gas injection and the combustion of stirling engine were studied in this thesis.Spray testing bench and combustion testing bench of stirling engine was built firstly. The influence of fuel property on spray characteristics of pressure-swril nozzle were studied. The spray characteristic of DME on pressure-swirl nozzle were studied. The influence of the gas injecting on the macroscopic and microscopic fuel spray characteristics were studied. The influencing factor of combustion flame were studied, the temperature field of combustion flames of stirling engine were studied in this thesis.The mainly contents are as follows:(1) spray characteristics of pressure-swirl nozzles of stirling engineFluid physical properties were changed by melted with little additives, the influence of viscosity and surface tension of fuel on spray macro characteristics were studied. The spray macro characteristics of DME on pressure-swirl nozzle were studied. Results show that: (a) Surface tension of fuel has little influence on spray cone angle; Spray cone Angle is decreased obviously with the increase of the viscosity of fuel under various working condition. (b) DME is required significantly higher pressure injection pressure to achieve the same fuel flow as diesel oil.(c) Under low ambient pressure conditions, The spray pattern of DME is thin when that is full for the spray of diesel oil.(d)Compare to diesel oil, the injection pressure of DME has little influence on drop size distribution, the drop size distribution are more uniform due to the boiling gasification DME under low ambient pressure.(2)Influence of the gas injecting on spray characteristicsHigh speed camera technology and FAM laser testing technology was applied to study influence of the gas injecting on both macroscopic characteristics and micro characteristics of stirling engine. Results show that:(a) Liquid drop at the beginning of spray which was common in no-gas-injection spray was disappeared in spray with gas injection. The preparative and development period of injection decrease in spray with gas injection. Diffusion area is increased in spray with gas injection compare to no-gas-injection spray. (b) The distribution of drop size relatively concentrated on a narrow interval in spray with gas injection. (c)The SMD of spray drop in spray with gas injection have a little increased. (3)Experimental study of combustion temperature of stirling engine The visualized test bench is established. High speed camera technology was applied to study ignition, flame structure. Double-color CCD method was applied to test temperature field. Results show that: (1) For the Stirling engine, the flame is formed stable only when injection pressure is big enough, and the flow rate of gas is not very much.(2) The flame itself has certain rotation. Flame length become shorter as the increase of the amount of the ejection gas. (3) The highest temperature area appears in the periphery of the flame without gas injection, the area of high temperature and the average temperatures became larger with air injection.This research will provide supports for improving Stirling Engine's combustion and emission performances, which has great theoretical and engineer application values.