受限空间内预混燃烧诱导射流点火的机理研究

The turbulent jet ignition, which can greatly improve the burning rate and expand the lean burn limit, is a new combustion mode which uses the ignition of micro jet chamber to ignite the mixture in main combustion chamber. The “Combustion-Gas Jet-Combustion” process during working involved complex interactions between combustion and turbulence. However, the existing studies only focused on the macroscopic performance of the combustor. Therefore, the project plans to deeply study the mechanism of turbulent jet ignition induced by premixed combustion in confined space based on an optical constant volume chamber system, by coupling use of the advanced experimental technologies including PIV, super high speed schlieren, multi-parameter LIF, GC/MS etc, and simulation methods of KIVA-Chemkin LES calculation. With the help of investigations, it is aimed to obtain the following achievements: Investigating the relationship between the premixed combustion of micro jet camber and the induced gas jet components and turbulence, to reveal the principle and mechanism of how does the combustion in confined space inducing the gas phase turbulent jet; Investigating the effect of turbulence, temperature and component of gas phase jet on the ignition and the process of chemical kinetics, to confirm the dominant factor of turbulent jet on ignition, and finally reveal the inducing ignition mechanism of turbulent jet; Investigating the microscopic development process of the gas jet and initial spatial structure of flame nucleus, to clarify the transmission mode of the flame propagation of initial fire nucleus, and finally reveal the propagation mechanism of the initial flame induced by turbulent jet. Therefore, the findings of the project could provide theoretical basis for further increase thermal efficiency and reduce emissions of internal combustion engines.

射流点火，是利用微型射流室点火引燃主燃室的一种新型燃烧模式，可大幅提高燃烧速率、拓展稀燃极限。它经历的“燃烧-射流-燃烧”过程涉及了复杂的燃烧湍流相互作用，但现有工作仅集中于宏观特性。为此，项目在定容燃烧弹上，综合利用PIV、超高速纹影、多参量LIF、GC/MS等实验手段和KIVA-Chemkin LES计算手段，对受限空间预混燃烧诱导射流点火机理展开研究。研究射流室预混燃烧与其诱导产生的气态射流成分及湍动的演变关系，揭示受限空间燃烧诱导射流的规律和机理；研究射流气体湍动、温度及组分对发火和化学动力学过程的影响规律，揭示影响射流诱导着火的主导因素，探明射流气体对主燃室混合气的诱导着火机理；研究射流气体和初始火焰微观发展过程及火核结构，明确初始火核火焰前锋面加速传播方式,揭示初始火焰的传播机制。从而，为发动机热效率的进一步提高、排放的进一步降低提供理论基础。

射流点火，是利用微型射流预燃室点火引燃主燃室的一种新型燃烧模式，用,但现有工作仅集中于宏观特性。为此，项目在定容燃烧弹上，综合利用高速摄影、纹影法、激光诱导荧光等实验手段和KIVA-Chemkin、Converge等计算手段，对受限空间预混燃烧诱导射流点火机理展开研究。结果表明：火花塞预燃室诱导的射流点火可大幅缩短滞燃期、前移燃烧重心、缩短燃烧持续期，并小幅提高最高燃烧压力；可以使燃烧放热过程对当量比变化的敏感性变弱；可大幅提高燃烧强化程度，且在稀燃区域更为显著；可有效抑制浓度较高时远端混合气的爆震燃烧现象。预燃室喉口对射流的影响主要体现在降温和淬熄，预燃室内点火位置以远离喉口为佳；射流在点燃主燃室时，温度起到比自由基更加重要的作用。提升射流的温度和速度，与稀薄燃烧技术相结合，有望实现点燃式发动机功率密度和效率的大幅提升。