The present study investigates the transient processes controlling ignition by a hot jet issued from a pre-chamber. Direct numerical simulations (DNS) have been performed to study the characteristics of the turbulent jet flow and of the associated flame during the whole ignition process, quantifying the relevant physicochemical interactions between pre-chamber and main chamber. Thanks to a detailed analysis of the DNS results, the transient ignition is found to consist of three main sequential processes: (1) near-orifice local ignition in the main chamber; (2) further flame development supported by the jet flow; and (3) global ignition and propagation of a self-sustained flame in the main chamber, independently from the hot jet. The characteristic time-scale of the hot jet as well as jet-induced effects (local enrichment, supply of radicals and heat) are found to be essential for successful ignition in the main chamber. A more intense turbulence in the main chamber appears to support local ignition. However, it also induces local quenching, thus delaying global ignition. An ignition threshold based on a critical Damköhler number is a promising concept, but is not sufficient to describe the process in all its complexity.

本研究调查了由预燃室发出的热射流控制点火的瞬态过程。已经进行了直接数值模拟 (DNS) 来研究整个点火过程中湍流射流和相关火焰的特征，量化前室和主室之间的相关物理化学相互作用。通过对 DNS 结果的详细分析，发现瞬态点火由三个主要的连续过程组成：（1）主室近孔口局部点火；(2) 在射流的支持下进一步发展火焰；(3) 独立于热射流的主燃烧室中自持火焰的全局点火和传播。热射流的特征时间尺度以及射流引起的效应（局部富集、发现自由基和热量的供应对于在主室中成功点火至关重要。主室中更强烈的湍流似乎支持局部点火。然而，它也会引起局部淬火，从而延迟全局点火。基于临界 Damköhler 数的点火阈值是一个很有前景的概念，但不足以描述该过程的所有复杂性。