This frame from simulation of reactive turbulent combustion with two flame fronts shows heat-release contours in the flow field.

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Toward Low-Cost Clean Power

A grant from DOE to support research between PSC and NETL laid the groundwork for (SC)². During the summer of 1999, PSC scientists collaborated on several projects related to producing electrical power with greater efficiency and lowered environmental impact. Along with the three projects described here, another project (with Stanford University) is described in The Edge of Reality.

Unsteady Flow in a Gas Turbine

PSC scientist Ravi Subramanya and Paul Cizmas of Texas A&M University used software they developed to simulate gas turbines. These huge jet-engine like machines do the heavy-duty work of converting fossil fuel into megawatts of electricity. Slight improvements in turbine efficiency can greatly reduce the cost of electrical energy.

The software — PaRSI3D (Parallel Rotor Stator Interaction 3D) — exploits the parallel-processing capability of machines like the CRAY T3E by using multiple processors to simultaneously calculate the flow at each turbine blade. This approach reduces simulation elapsed time compared to "serial" turbine-simulation, which sequentially calculates the flow at each blade. Along with greatly reducing turnaround time, PaRSI3D also produces more accurate results.

Cizmas and Subramanya first developed their parallel approach to turbine simulation in two dimensions. With PaRSI3D, they extended it to the much more challenging problem of three dimensions. Enhancements to the software provide useful information for turbine design, such as radial flow features. These simulations help to optimize the shape and relative positioning of turbine blades, design factors that can improve turbine efficiency.

Lean Combustion for Gas Turbines

This frame from simulations by NETL researchers (rendered by PSC scientist Nick Nystrom) depicts temperature during methane combustion in the NETL Dynamic Gas Turbine Combustor. Dowload a larger version of this image (321 KB).

As part of DOE's Advanced Turbine Systems Program, NETL researchers have used the CRAY T3E to simulate the NETL Dynamic Gas Turbine Combustor. With this experimental facility, NETL studies "lean, pre-mix combustion" — burning relatively low quantities of fuel relative to air, which reduces emissions of nitrogen-oxide pollutants.

Lean-fuel mixes often lead to combustion instability, rapid pressure oscillations that can create problems in the turbine. Using FLUENT (a commercial fluid-dynamics package) on the T3E, NETL researchers replicated a series of experiments using different combustor geometries at varying flow rates and fuel-air mixtures. Prior research indicates that the magnitude of the instability depends on the delay between when fuel is injected and the mixture reaches the flame. The simulations confirm this and suggest that the delay varies with flame shape and size and that these flame characteristics themselves vary with combustor geometry and operating conditions.

Improved Software for Turbulent Combustion

In another project of interest to NETL, PSC scientists Ravi Subramanya and Raghu Reddy collaborated with scientists at the Combustion Research Facility at Sandia-Livermore National Laboratory to develop a parallel implementation of software for direct numerical simulation (DNS) of combustion flow. The basic problem is what happens when gas or liquid fuel burns under conditions of turbulent flow, and DNS provides fundamental insight into the underlying physics, which helps to verify other forms of modeling.

Within three months of project inception, Subramanya and Reddy developed a scalable, parallel implementation of the 2D software. They also recently released a 3D implementation. Sandia researchers can now use parallel systems like the CRAY T3E to tackle complex problems that previously would have exceeded computational capability. Tests show excellent scaling on the T3E — increasing speedup with added processors, so that problems taking a year with the serial software now take a day on the 512-processor T3E.

More Information: PA and WV Form High-Tech Regional Partnership: http://www.psc.edu/publicinfo/news/1999/sc2_08-31-1999.html PSC Regional Partner Becomes National Laboratory: http://www.psc.edu/publicinfo/news/1999/netl_12-14-1999.html Energy Secretary Richardson Designates Technology Complex in West Virginia, Pennsylvania as Newest National Laboratory (NETL News Release): http://www.fetc.doe.gov/publications/press/1999/tl_fetclab.html PSC and NETL research collaborations: http://www.psc.edu/research/fetc/