采用直接数值模拟方法对二甲醚(Dimethyl Ether，DME)射流推举燃烧进行了研究（DNS），分析了DME射流推举火焰结构、燃烧模式和推举稳定机理。数值模拟工况条件为：燃料由狭缝射出，初始温度500 K，射流速度138 m/s；伴流空气的初始温度1 000 K，流速3 m/s，压力为0506 6 MPa。研究表明：DME射流推举火焰与传统的边火焰有很大不同，在射流核心区内存在1条低温放热分支以及紧随其后的中温着火分支，并且推举稳定点位于贫燃侧；DME湍流射流推举火焰包含冷焰反应区(Cool Flame Zone，CFZ)、中温反应区(IntermediateTemperature Zone，ITZ)、富燃高温区(HighTemperature Rich Burn Zone，HTR)以及贫燃高温区(HighTemperature Lean Burn Zone，HTL)4种模式；在CFZ与ITZ区内湍流混合占主导，并且湍流混合会抑制低温放热；在HTR与HTL区内放热速率占主导地位，但是湍流会显著增强超贫燃区间内的高温放热速率；大部分热量在HTL和HTR区产生，而CFZ和ITZ区对总体产热的贡献微乎其微，但是所产生的中低温组分加快了高温着火过程；射流推举稳定性由贫燃侧的高温自着火反应机制所控制。

The direct numerical simulation(DNS) was conducted to analyze flame structure, combustion modes and liftoff stabilization mechanism of the dimethyl ether (DME) turbulent lifted jet flame. The fuel was ejected from the slot with an initial temperature of 500 K and the jet velocity of 138 m/s; the initial temperature of the coflow air was 1 000 K, the flow velocity was 3 m/s, and the initial pressure was 0.506 6 MPa. The results show that the DME lifted jet flame structure is rather different from the traditional edge flame, i.e. there exists a lowtemperature heat production branch as well as a following intermediatetemperature ignition branch in the jetcore zone, and additionally, the stabilization point is located at the fuellean side; four combustion modes including cool flame zone (CFZ), intermediate temperature zone (ITZ), high temperature rich burn zone (HTR) and high temperature lean burn zone (HTL) modes coexist in the turbulent lifted reacting zone; turbulent mixing is dominated in the CFZ and ITZ zones, and it will inhibit the local lowtemperature heat production rate; in HTR and HTL zones, heat release reaction overwhelms turbulent mixing, but turbulence can considerably enhance heat production in the ultralean and hightemperature zone; the majority heat is produced in the HTL and HTR zones, while contributions of CFZ and ITZ to the total heat production are fairly ignorable, however, the medium and low temperature species generated in CFZ and ITZ play an important role in accelerating the hightemperature mixture ignition; stabilization of the current liftoff DME jet flame is governed by the fuellean and hightemperature autoignition mechanism.

TK16

国家自然科学基金(22178032, 51706027)