No abstract

Understanding the mixing process of under-expanded gaseous-fuel jets from an outward opening injector is essential for developing Direct Injection (DI) internal combustion engines. This paper presents a Large-Eddy Simulation (LES) study of the DI of methane into a Constant Volume Chamber (CVC), considering the full, internal geometry of a prototype injector. Four cases at conditions relevant to Compressed Natural Gas (CNG) DI engines are investigated, with methane as a surrogate for CNG. A new post-processing method permits the 3D LES field to be projected into a 2D density gradient field that can be compared to a schlieren image. The LES results are then validated against high-speed, schlieren imaging experiments, demonstrating that the simulations are able to reproduce experimental trends. Three main regions of the external flow are observed: a recirculation zone just downstream of the injector tip, a stagnation zone and a far-mixing zone. The location of the stagnation zone increases as the CVC pressure decreases, consistent with a theory presented in the literature.The modelling of the full internal geometry of the injector leads to a determination of the injector pressure losses. Once the pressure loss within the injector is considered, a short version of the injector can reasonably represent the full injector for prediction of the external flow.

No abstract

Hydrogen is a promising alternative fuel to reduce the carbon footprint from combustion systems such as gas turbines. However, hydrogen has very different properties from methane, which is the main component of natural gas, a common fuel used in gas turbines. This introduces numerous challenges in the operation of combustion systems. One pathway towards reducing emissions and mitigating these challenges at the same time is to mix hydrogen with natural gas. To study the behaviour of hydrogen/natural gas flames, a Direct Numerical Simulation (DNS) of a turbulent 50% H 2 / 50% CH 4 (by volume) fuelled flame at a moderate Reynolds number of 10,300 is conducted. Key flame statistics, namely curvature and flame displacement speed, are examined. The results are also compared to the DNS results of a pure methane fuelled flame at a Reynolds number of 5,300.