An increasing demand for efficient and environmentally clean use of biomass and wood waste byproducts as fuel requires major developments in gas turbines. Gas turbines are designed primarily to handle either natural gas or in some cases diesel fuels. Introducing low BTU, contaminants containing biofuels into a gas turbine would require proper understanding of fuel characteristics, combustor capability to burn these fuels, compressor surge margins, and ability of the turbine section to withstand deposition, erosion and corrosion.
Allison Engine Company (Allison), in cooperation with the U.S. Department of Energy and other partners, has initiated a bioturbine development project which would lead to commercialization of a bioturbine to operate on major categories of biofuels. The project will address six key issues:
• Quantify chemical, physical and combustion characteristics of biofuels, gasifiers, and the mass volume
• Conduct emission modeling of existing combustor with low BTU fuels
• Conduct rig tests
• Modify current design of the combustor to handle low BTU fuels
• Evaluate compressor surge margins to handle increased mass flows
• Conduct full scale engine field test
The total cost of this two and a half years project is approximately $8 million. The DOE will contribute over $3 million. Allison and partners will contribute the remaining $5 million.
There is an additional vital task which must be performed, but is not a part of the current project. The capability of the turbine to withstand deposition, erosion and corrosion must also be evaluated in order to protect the turbine, and provide long term, uninterrupted operation of the gas turbine on biofuels.
An important first step is to obtain quantitative data on gasified biofuels, including the contaminants. This information will be used in combustor modeling and to develop rig tests. The combustor will then be modified and made capable of handling these fuels. Allison will use the 601-K engine combustor (similar to the RB211 DLE combustor), and modify its hardware and software as required. The combustor modification will involve modeling, rig test, hardware and software modifications, and final engine test The entire project is expected to be complete during the second half of 1999.
Concurrent with these tasks, Allison will evaluate the options available to increase the capability of engine mass flow due to low BTU fuels. A parallel task of “ruggedizing” the turbine section is also planned. The resulting turbine is expected to be comparable to natural gas fired commercial gas turbines in performance, durability, reliability and major overhaul cycles.