Objective - Phase II
The objective of Phase II of the Advanced Turbine Systems Program is to develop conceptual designs of gas fired advanced turbine systems that can be adapted for operation on coal and biomass fuels. The technical, economic, and environmental performance operating on natural gas and in a coal fueled mode is to be assessed. Detailed designs and test work relating to critical components are to be completed and a market study is to be conducted.
Background Information
Throughout its 35 year history as a supplier of industrial gas turbines, Solar has maintained a careful surveillance of the marketplace into which the company's product is sold. This effort has paid off in the growth of Solar into the world's leading supplier of midsized industrial gas turbine systems.
Based on the ongoing evaluation of the marketplace, Solar established short- and long-term product development goals which coincide exactly with ATS goals as set by the DOE in four areas:
- Reduced exhause emissions.
- Increased Reliability, Availability, Maintainability, Durability (RAMD).
- Reduced cost of power.
- Increased thermal efficiency.
Entering into Phase II of the ATS Program, Solar has quantified goals in these four areas as shown in Table 1.
| Parameter | Solar's ATS | Thermal Efficiency | 50% |
|---|---|
| Exhaust Emissions NOx | 8 ppm |
| Exhaust Emissions CO and UHC | 15 ppm |
| Cost of Power (COP) | 10% Reduction from Today | Reliability, Availability, Maintainability, and Durability (RAMD) | Equal to or Better than Today |
Project Description and Results
An intercooled and recuperated (ICR) gas turbine has been identified as the power plant best suited for development to meet ATS objectives. The technologies that will need to be incorporated into an ICR to meet these objectives are within the capability of development by a manufacturer of industrial gas turbines, i.e., Solar. More importantly, these technologies are likely to find ready acceptance in the industrial gas turbine marketplace, i.e., characterized by moderate risk and reasonable cost. Many of these technologies will also find application in Solar's current product line and as retrofit improvements in Solar's 9200-unit installed fleet.
Recuperation of the classic Brayton cycle gas turbine is a well-known efficiency improvement that has been applied at levels of success primarily established by the cost and durability of the required heat exchange device. At any given level of peak temperature a recuperated Bryaton cycle will have an optimum overall pressure ratio. At pressure ratios above this optimum, recuperation capability is reduced by the narrowing gap between exhause temperature and compressor discharge temperature
The addition of one or more stages of intercooling into the compression process of the Brayton cycle will significantly reduce the work input required by the compression process. The combination of intercooling and recuperation into an ICR cycle produces an increase in both specific power and thermal efficiency. The thermal efficiency improvement derives from an increased temperature differential between the exhaust gas stream and the compressor discharge air. This enables the recovery of a greater portion of the thermal energy in the exhause gas. In a modern ICR, thermal efficiency continues to increase with pressure ratio and with temperature.
Summary
Solar approached Phase II of the ATS program with the goal of providing a system that would be capable of 50 percent thermal efficiency. An intercooled and recuperated (ICR) gas turbine was identified as the ultimate system to meet this goal in a commercial gas turbine environment. Proceeding with commercial input from detailed market studies and examining the boundaries of the DOE's ATS program as defined in the Solicitation for Cooperative Agreement (SCAP) for Phases III and IV, Solar redefined the company's proposed ATS to fit both market and sponsor (DOE) requirements. the resulting optimized recuperated gas turbine will be developed in two sizes, 5 MWe and 15 MWe. It will demonstrate a thermal efficiency of approximately 43 percent -- a 23 percent improvement over current gas turbine product in the industrial size range. Other ATS goals -- emissions, RAMD (reliability, availability, maintainability, and durability), and cost of power will be met or exceeded. During FY 1995, advanced development of key materials, combusion and component technologies proceeded to the point of accepting them for inclusion in ATS Phase II development along with parallel path risk-reduction approaches.
S. Gates, Solar Turbines Incorporated Return to the Top
Allison Engine ATS Program Technical Review
Introduction
Gas turbines in industrial and utility applications can help meet future national and worldwide power generation requirements. Turbine systems burning natural gas offer environmentally sound and economical power generation and cogeneration. Since U.S. demand alone will require up to 15 gigawatts per year of new and replacement capacity after the year 2000, the availability of Advanced Turbine Systems (ATS) to fill a share of this need will save significant amounts of fuel and benefit the environment. Implementation of the ATS Program will also keep U.S. manufacturers on the cutting edge of turbine technology for power generation applications and enhance the nation's economic competitiveness.
Objectives
Allison was awarded an ATS Phase 2 program in August 1993 with an 18-month period of performance. The specific primary objectives for this program were:
- select the design thermodynamic cycle for the ATS
- complete the preliminary design of the engine components
- complete preliminary design of the engine skid and all ancillary components
- test the prototype high pressure turbine section of 2600 deg F and analyze the resultant data
- validate and refine the fabrication of turbine blades using the existing Castcool(R) process
- accomplish sufficient testing of combustor components to determine the best approach to achieving the emissions requirements
- perform laboratory tests on a turbine vane design utilizing two-phase cooling to reduce airflow requirements
- select coating systems for turbine blades and vanes for oxidation/corrosion protection
Project Description
Allison's ATS addresses the program goals in the following manner:
- Efficiency - The turbine selected for the ATS uses Allison's latest single crystal alloys incorporating the most efficient component cooling technology Allison has developed. These features allow the turbine to operate at a rotor inlet temperature (RIT) of 1427 deg C (2600 deg F). The compression system for this engine has an overall pressure ratio of more than 20:1 and is based on technology previously demonstrated at Allison. The engine that uses these components will demonstrate a thermal efficiency that is 18% better than the best in class today.
- Environment - The combustion system selected for this engine incorporates a catalytically stabilized, lean premix system with ceramic components requiring no significant wall cooling. This system will achieve acceptance in severe nonattainment areas, producing less than 8 ppm for oxides of nitrogen (NOx), with acceptable carbon monoxide (CO) and unburned hydrocarbon (UHC).
- Fuel Flexibility - Allison has production engines in commercial service that are operating on biomass fuels. Previous DOE-funded programs have allowed Allison to develop and demonstrate coal-fueled gas turbine technology. The ATS program will use this experience to create a design that will be adaptable for the use of these fuels in the future.
- Cost of Power - The busbar cost of energy for the Allison ATS ranges from 23.6 to 27.6% lower than the current state of the art for systems meeting ATS environmental requirements. The requirement of the program is a 10% reduction in busbar cost. This improvement is the result of the high efficiency and the low emissions inherent in Allison's system design.
- Reliability, Availability, and Maintainability - The Allison ATS will be designed to have high reliability and low maintenance costs. Critical components will be designed using Allison's latest life analysis methods. Component and materials tests will be conducted to verify these analyses. The engines and skids will be modular by design to allow field maintenance and service in the minimum time possible.
D. Mukavetz (iedwm@agt.gmeds.com; 317-230-2575), Allison Engine Company.
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