Modern combustion devices are designed to balance the need for efficient performance with the need for robust performance. Presently available design techniques are capable of meaningfully informing how this balance should be struck. To truly optimize the efficiency and robustness of a combustor, however, the predictive capabilities of numerical simulations will have to be more heavily relied u...

As a fundamental study in the application to direct-injection spark-ignition engines or gas turbines, in which mixture stratification and partial quenching are of serious concerns, unsteady premixed methane/ air flames subjected to time-varying composition fluctuations are investigated computationally. The code OPUS employs an unsteady opposed-flow combustion configuration, including detailed c...

The present work addresses unsteady flame dynamics in a lean-premixed swirl-stabilized combustor, with attention focused on the transition of flame structure from a stable to an unstable state. It was found that the inlet temperature and equivalence ratio are the two most important variables determining the stability characteristics of the combustor. A slight increase in the inlet mixture tempe...

A multi-pulse injection strategy for premixed charge compression ignition (PCCI) combustion was investigated in a four-valve, direct-injection diesel engine by a computational fluid dynamics (CFD) simulation using KIVA-3V code coupled with detailed chemistry. The effects of fuel splitting proportion, injection timing, spray angles, and injection velocity were examined. The mixing process and fo...

Gibson scaling and related properties of flame-surface geometry in turbulent premixed combustion are demonstrated using a novel computational model, Deterministic Turbulent Mixing (DTM). In DTM, turbulent advection is represented by a sequence of maps applied to the computational domain. The structure of the mapping sequence incorporates pertinent scaling properties of the turbulent cascade. He...

We consider a three-dimensional thermal-diffusion model for a premixed burner flame. Many experimental and theoretical works in condensed-phase and gas combustion show that the flame front may propagate in a number of different ways. The structure and stability properties of the front depend essentially on the physical parameters of the model. This article describes the use of the symbolic mani...

Hot surface ignition was examined using a variety of heat sources in a series of premixed hydrocarbon, hydrogen, and air mixtures. Building off previous work, hexane-air, heptane-air and hydrogen-air experiments were performed in addition to the eventual hexane-hydrogen-air mixtures. Using high-speed schlieren photography, thermocouples, and a fast-response pressure transducer, flame characteri...

Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures). The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability ...