The Advanced Vortex Combustor

Ramgen Power System’s lean-premixed Advanced Vortex Combustor (AVC) is an enabling technology for gas turbine engines, which can allow them to meet stringent emission regulations with a simple retrofit and without the need to modify the engine casing. The unique AVC combustion technology can provide low exhaust emissions without additional catalytic or SCR after treatment systems. The inherent stability of the AVC can provide added operational stability with challenging fuels such as low Btu biomass or coal-derived syngas, and can address the growing problem of varying LNG fuel quality that is creating operational problems for many of the turbines operating on pipeline service.

The AVC has the potential to:

- Increase the overall engine efficiency by three to five percentage points
- Enhanced the engine durability with a significant increase in engine shaft power
- Achieve < 3ppmv NOx
- Offer a dry low NOx “drop-in” retrofit with minimum casing modifications, if at all
- Improved engine operating stability with wide and varying fuel quality composition
- Increase time intervals between scheduled maintenances.

This combustor has been tested with natural gas fuel at the General Applied Sciences Laboratory (GASL) in Ronkonkoma, NY, the U.S. Department of Energy’s National Energy Technology Laboratory (DOE/NETL) in Morgantown, WV, and the Air Force Research Laboratory (AFRL) in Dayton, OH. The tests have been performed at elevated pressures and temperatures at lean fuel-air ratios traceable to typical operating conditions of industrial gas turbines.

Ramgen’s AVC technology achievements:

· Simultaneous NOx/CO/UHC emissions of 4/4/0 ppmv (corrected to 15% O2 dry);
· Less than 3 ppmv NOx with combustion efficiencies in excess of 99.5%;
· Excellent acoustic dynamic stability over a wide range of operating conditions;
· Fuel flexibility including combustion of high flame speed fuels;
· Significantly lower pressure drop than traditional gas turbine combustors.

These results have been documented in a peer-reviewed paper (GT2006-90319) and presented at the ASME TurboExpo 2006 in May 2006.

Figure 1 shows the NOx emissions for the baseline vortex cavity equivalence ratio (i.e., fuel setting 1) and the NOx levels for reduced cavity equivalence ratios. At a main equivalence ratio of 0.54, NOx emissions were below the program goal of 3 ppmv. Combustor optimization should enable further reduction of the cavity equivalence ratio with subsequent improvement in NOx emissions beyond that shown.

Effect of equivalence ratio on NOx.

Effect of equivalence ratio on CO- NOx curve

The CO-NOx data in Figure 2 shows that the curve shifted to lower NOx levels for different fuel settings. CO emissions, however, were insensitive to cavity equivalence ratio. The emphasis for these tests was to reduce the NOx emissions and not to optimize the overall combustor design for reduction of CO to CO2, but the results indicate that further optimization is highly probable.

The CO emission (primary y-axis) and the RMS pressure (secondary y-axis) as a function of NOx emissions are shown in Figure 3 for two main equivalence ratio sweeps. RMS pressure remained very low with increasing CO and was an order of magnitude lower than the typically accepted industrial level of 1.5% RMS. Although not an original design goal, the dynamic stability of this design was a significant achievement of this project.

CO and RMS Pressure as a function of NOx
Note: Colored data is RMS pressure;
black and white data is CO.

Market Potential
The potential market has been identified as the Industrial & Marine gas turbine class for power generation and mechanical drive applications. The projected $50 million value is based on a market penetration rate of 15% at maturity, with operating margins of 35% to 40% per unit.

Other potential markets are available but have not been quantified and include:

· Mixed fuel turbines;
· High Hydrogen content fuel applications; and
· Combustors for aviation applications, including military engine applications

The value of low-NOx combustion capability is validated by the Alstom purchase of Power Systems Manufacturing (PSM) in 2007 for $225mm. PSM redesigns GE combustors for the Frames 6B, 7E/EA and 9E, as well as the state-of-the-art F-class systems. The PSM technology is best characterized as a further optimization of conventional approaches.

The breakthrough AVC technology has the ability to improve on these emission levels and offer the additional and substantial benefits of improved engine efficiency and operational

The basis for the AVC value is that Ramgen has succeeded in producing verifiable test results where others have failed, and has earned the comment from a leading combustion scientist at NETL of “the most stable combustion he has ever seen.”