Modeling of Gas Turbine Cycles Fueled by Syngas

Coal will inevitably be a substantial component of the world’s energy future, and the most likely scenario for using coal in future energy systems employs gasification, with the synthetic gas that is produced used to fire a gas turbine. In connection with local efforts to develop gasification methods applicable to Wyoming coals, we are modeling gas turbine performance and selected aspects of turbine design when fuel mixtures containing hydrogen and carbon monoxide are used. However, unlike most gasification proposals that incorporate costly steam cycles downstream of the gas turbine, we are considering means by which the gas turbine performance can be maximized. In particular, we are extending some of the author’s recent work on alternative regeneration schemes to investigate oxygen and syngas fired gas turbines that recycle carbon dioxide for temperature quenching. These cycles readily lend themselves to carbon sequestration.

Enhanced Heat Transfer Downstream of Synthetic Jets

In recent years, various schemes for introducing longitudinal vorticity into boundary layer flows have been examined for their influence on convective heat transfer enhancement. The goal of the present project is to examine the relatively new mechanism of vortex generation by synthetic, zero-mass flux jets introduced normal to the boundary layer, with particular emphasis on the resulting heat transfer enhancement downstream of the jets. Synthetic jets are being proposed for a wide range of applications, most of which pertain to delaying flow separation, and in most of these the heat transfer enhancement will be very important to the jets’ feasibility. A liquid crystal technique is being used in conjunction with real-time, color-video data capture. The heat transfer enhancement due to both a single jet and arrays of jets is to be examined as a function of a variety of variables, including jet velocity, jet angle, jet frequency, and jet mass flux.

The Effect of High Turbulence Levels on Convective Heat Transfer

As a consequence of having two unusually large data sets, one for swirling flows and another for flows through passages with ribbed walls, both of which entail highly turbulent flows, we have been interested in trying to characterize heat transfer coefficients as a function of turbulence level. Our work has been guided by that of Maciejewski and Moffatt who showed that relatively simple geometry-independent correlations could be developed, and that these correlations might not depend on some parameters that have been historically important, such as the Reynolds number. Rather, for some flows, the convective heat transfer appears to be dominated by the turbulent fluctuations, so that the resulting correlations are dominated by some appropriate characterization of the turbulence level. The current work is attempting to develop a geometry-independent correlation for internal flows that does not entail inclusion of a length scale, which appears to be an overly-complicated and unneeded parameter. Relative to this last goal, our measurements have shown that the heat transfer coefficient is directly proportional to the turbulence intensity for high levels of turbulence, but a general-purpose correlation for collapsing the data has been elusive. The most recent measurement focused on a new set of experiments intended to decouple the effects of Reynolds number and turbulence intensity, so that the effects of each can be clearly understood.