Gas Turbines are an important contributor to the world’s power generation at base and peak load conditions, and this participation is expected to last for the decades to come, even with the increasing use of renewable energies given their unique ability to supply large amounts of power in a short period of time (unlike coal or nuclear plants). On the other hand, the power produced by gas turbines is significantly reduced at higher ambient temperatures, which coincides with the peak power demand. Air density is reduced, either as consequence of high elevation above the sea level, or due to higher ambient temperatures, and the air mass flow passing into a gas turbine diminishes consequently. With this flow down, the fuel flow is reduced proportionately in order to maintain combustion temperature, reducing, in turn the power generation. This paper presents a parametric evaluation of a novel power enhancement scheme: intercooled compressed air injection, with performance simulations of a “F” class industrial gas turbine in a 1×1 combined cycle application made with Thermoflow GTPro and GTMaster ® software. Results show that compressed air injection achieves significant levels of power boost at heat rates better than those of simple cycle power plants, resulting in an attractive option for power-starved utilities during summer days.
The recent volatility in oil prices has fueled uncertainty about the world’s ability to meet future demands. Furthermore, the growing concern over the negative environmental impacts produced by emissions has resulted in worldwide efforts for developing renewable jet-fuel alternatives. This has led current military and civilian fuel specifications to allow the use of Fischer-Tropsch (FT) and Hydroprocessed fuels (HEFA) in blends up to 50% in volume with regular Jet-A/JP-8. On the other hand, physical properties, and the broad chemical composition, including trace elements in those fuels, may result in engine performance issues found only after extensive operation. This may result in higher maintenance and operation costs. This study presents the coking depositions of several renewable fuels after being stressed in a fixed bed reactor. This was done in an effort to assess the effects (if any) on the thermal stability of renewable fuels interacting with materials representative of state of the art aircraft systems (steel, aluminum, titanium tubing) and to determine whether the use of renewable fuels enhances thermal stability when blended, up to 50%, with oil-derived fuels.
Environmental and supply considerations are playing a pivotal key in the economics and operation rationale behind power generation. A once fossil-fuel dependent industry is embracing renewable sources, albeit slowed by technical and economic challenges. With gas turbines comprising a large part of the world’s electric generation pool, increasing the power output of the existing combined cycle plants and avoiding the use of less efficient peakers has the potential of reducing greenhouse gas emissions. Performance simulations show that compressed air injection can increase the power output of 2×1 combined cycle “F” class plants above 40 MW, equivalent to the typical output of simple cycle peaking units. Resultant total power output can be maintained while reducing pollutants, infrastructure resources, and capital cost compared to peaking plants.
Increased oil prices and environmental awareness have resulted in worldwide efforts for developing renewable jet-fuel alternatives, at the point when several synthetic fuels are currently certified for blending with Jet-A/JP-8. However there are uncertainties regarding the effects in aircraft performance and systems of properties such density, heating value and chemical composition. While the higher heating value and lower density synthetic common in renewable fuels under development might result in higher aircraft performance, the lack of aromatic components could result in damage in the elastomer materials used in the fuel system. This paper presents results of the changes in performance characteristics (Thrust, SFC, and TIT) of a micro-turbine operated with various Fischer-Tropsch (FT) and Hydrotreated Esters and Fatty Acids (HEFA) jet fuels and their blend with Jet-A, a payload vs. range analysis of a commercial airliner. Mass and volume swelling measurements of nitrile rubber O-rings immersed during 28 days in Jet-A and renewable fuels blends are also presented. Nomenclature FT = Fischer-Tropsch HEFA = Hydrotreated Esters and Fatty Acids L/D = lift to drag ratio LHV = low heating value Mt = million tones P = Pressure [psi] R = aircraft range [nm] SFC = engine specific fuel consumption TIT = turbine inlet temperature V = velocity (m/s) W 1 = aircraft maximum weight [kg] We = operational empty weight [kg] Wf = fuel weight [kg] Wp = payload weight [kg] Wto = take-off weight [kg] Greek symbols = fuel density [kg/m 3 ] Subscripts o = baseline value ren = renewable
Historically, gas turbine fuels have been procured based on availability and low cost criteria. But in the last few decades, with the growing concern over the negative environmental impacts produced by emissions, alternative fuels have been developed and tested with the objective to reduce such negative effects. Physical properties and the broad chemical composition, including trace elements, may result in engine performance issues found only after extensive operation. This, in turn, results in higher maintenance and operation costs. This paper studies the feasibility for microturbine application of several renewable fuels, identifying key relationships between physical and chemical properties, thermal stability, materials compatibility, and turbine performance.
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