Gas Turbine Auxiliary Power Unit Research Articles

Analysis of a gas turbine auxiliary power unit system based on a fuel cell combustor

In this study, a gas turbine (GT) system for auxiliary power units (APUs) is proposed based on a fuel cell combustor, which separates combustion into three processes: fuel-rich combustion, electrochemical reaction through solid oxide fuel cells (SOFCs), and fuel-lean combustion. Compared with the traditional GT system, the efficiency of the proposed system is much higher due to the high efficiency of the electrochemical conversion process in SOFCs. Meanwhile, the advantage of the GT's high power density is conserved to improve the system power density by increasing the GT power proportion, which makes it possible to be used as an APU for aircraft. First, the system was simulated and evaluated at the base case with electrical efficiency reaching 45.62% and power density reaching 0.43 kW/kg. Then, extra fuel was added into the fuel-lean combustion chamber to increase the GT power proportion, which led to an increase in power density and a decrease in efficiency. Finally, the concept of a superhigh-temperature SOFC was proposed to further increase the system power density. When the SOFCs operate at a superhigh temperature of 1473 K, the power density of the system reaches 2.67 kW/kg, which is much higher than that of conventional SOFC-GT hybrid systems.

Technological analysis and fuel consumption saving potential of different gas turbine thermodynamic configurations for series hybrid electric vehicles

Gas turbine systems are among potential energy converters to substitute the internal combustion engine as auxiliary power unit in future series hybrid electric vehicle powertrains. Fuel consumption of these auxiliary power units in the series hybrid electric vehicle strongly relies on the energy converter efficiency and power-to-weight ratio as well as on the energy management strategy deployed on-board. This paper presents a technological analysis and investigates the potential of fuel consumption savings of a series hybrid electric vehicle using different gas turbine–system thermodynamic configurations. These include a simple gas turbine, a regenerative gas turbine, an intercooler regenerative gas turbine, and an intercooler regenerative reheat gas turbine. An energetic and technological analysis is conducted to identify the systems’ efficiency and power-to-weight ratio for different operating temperatures. A series hybrid electric vehicle model is developed and the different gas turbine–system configurations are integrated as auxiliary power units. A bi-level optimization method is proposed to optimize the powertrain. It consists of coupling the non-dominated sorting genetic algorithm to the dynamic programming to minimize the fuel consumption and the number of switching ON/OFF of the auxiliary power unit, which impacts its durability. Fuel consumption simulations are performed on the worldwide-harmonized light vehicles test cycle while considering the electric and thermal comfort vehicle energetic needs. Results show that the intercooler regenerative reheat gas turbine–auxiliary power unit presents an improved fuel consumption compared with the other investigated gas turbine systems and a good potential for implementation in series hybrid electric vehicles.

Dynamic Modeling and Fuel Consumption Potential of an Intercooled Regenerative Reheat Gas Turbine Auxiliary Power Unit on Series Hybrid Electric Vehicle

Abstract Gas turbine systems are among potential energy converters to substitute the internal combustion engine in future series hybrid electric vehicle. Fuel consumption of these powertrains strongly relies on the energy converter efficiency, the energy management strategy deployed on-board as well as on the transient operation during start-up phase. This paper presents a dynamic modeling and the fuel consumption calculation of an intercooled regenerative reheat gas turbine system used as an auxiliary power unit on a series hybrid electric vehicle. A vehicle model is developed and an optimization method is proposed to optimize the powertrain operation. It consists of using the dynamic programing as an energy management strategy in order to minimize the fuel consumption and the number of switching On/Off of the power unit. Fuel consumption simulations are performed on the worldwide-harmonized light vehicles test cycle while considering the electric and the thermal comfort vehicle energetic needs. Then, a gas turbine dynamic model is developed, where turbomachinery and heat exchanger components are modeled by taking into account their dynamic inertias. The efficiency, the power, and the fuel consumption are calculated during transient operations. Based on the optimization results of switching ON and OFF the system, the fuel consumption dynamic simulation results are considered instead of the dynamic programming results. A constant power start-up strategy and a constant fuel strategy were investigated. Results show an increase in fuel consumption between 2.4% and 3.8% with the first start-up scenario and between 5.7% and 6.4% with the second scenario, compared with static model.

The effect of alternative fuels on gaseous and particulate matter (PM) emission performance in an auxiliary power unit (APU)

ABSTRACTThere is a growing interest in the use of alternative fuels in gas turbine engines to reduce emissions. Testing of alternative fuels is expensive when done on a large-scale gas turbine engine. In this study, a re-commissioned small gas turbine auxiliary power unit (APU) has been used to test various blends of Jet A-1, synthetic paraffinic kerosene (SPK) and diesel with as well as eight other novel fuels. A detailed analysis of performance, gaseous emissions and particulate emissions has been presented in this study. It is observed that aromatic content in general as well as the particular chemical composition of the aromatic compound plays a vital role in particulate emissions generation. SPK fuel shows substantially lower particulate emissions with respect to Jet A. However, not all the species of aromatics negatively impact particulate emissions. Gaseous emissions measured are comparable for all the fuels tested in this study.

System Architectures for Solid Oxide Fuel Cell-Based Auxiliary Power Units in Future Commercial Aircraft Applications

Recent advancements in fuel cell technology through the auspices of the Department of Energy, the National Aeronautics and Space Administration, and industry partners have set the stage for the use of solid oxide fuel cell (SOFC) power generation systems in aircraft applications. Conventional gas turbine auxiliary power units (APUs) account for 20% of airport ground-based emissions. Alleviating airport ground emissions will continue to be a challenge with increased air travel unless new technology is introduced. Mission fuel burn and emissions can be significantly reduced through optimal systems integration of aircraft and SOFC subsystems. This study examines the potential total aircraft mission benefits of tightly integrating SOFC hybrids with aircraft subsystems using United Technologies Corporation Integrated Total Aircraft Power Systems proprietary methodologies. Several system concepts for optimal integration of the SOFC stack with aircraft subsystems are presented and analyzed in terms of mission fuel burn for technologies commensurate with 2015 entry into service. The performance of various hybrid SOFC-APU system architectures is compared against an advanced gas turbine-based APU system. In addition to the merits of different system architectures, optimal SOFC system parameter selection is discussed. The results of the study indicate that despite the lower power density of SOFC-based APU systems, significant aircraft fuel burn (5–7%) and emission reductions (up to 70%) are possible. The majority of the fuel burn savings are realized during aircraft ground operations rather than in-flight mission segments due to the greater efficiency difference between the SOFC system and the advanced APU technology.

Hybrid fuel cell power in aircraft

Traditionally, electric generators, driven by an aircraft's main propulsion engines or by a gas turbine (GT) auxiliary power unit (APU), have supplied the electrical needs of commercial aircraft. In flight, the marginal efficiency of electric power generated by the main engines and their generators is at most 30-40%, whereas on the ground with the engines shut off, the average fuel efficiency of the turbine-powered APU is typically less than 20% and also has undesirable noise and gaseous emissions. As environmental concerns mount, aircraft manufacturers and others are challenged to reduce fuel consumption while simultaneously reducing emissions. Hence, there is a very strong interest in developing fuel cells for aerospace applications. In this article, we report the study results of usingsolid oxide fuel cells (SOFCs) in combination with a GTas a hybrid APU system for a commercial aircraft. The purpose of this feasibility study is to investigate the potential use of fuel-cell-based APUs for onboard power generation in future more-electric commercial aircraft. In this article, the modeling of the major components of the SOFC-GT power generation system, summary of the findings, challenges, and final recommendations are presented.

Component and Procedural Improvements for the T-62T-40-7 Gas Turbine in the LCAC Fleet

The Sundstrand Power Systems T-62T-40-7 Gas Turbine Auxiliary Power Unit (APU) was adapted from an aircraft-borne APU to a marine application on the U.S. Navy’s Landing Craft Air Cushion (LCAC). Although the LCAC APU experienced less operating time than its aircraft version, the environmental conditions that exist cause unusual wear and component failures. Component and procedural improvements have been developed to extend the reliability of the T-62T-40-7 on board the LCAC.

Auxiliary Power

Requirements for civil and military applications are reviewed and power sources discussed. Features of the gas turbine auxiliary power unit are presented, including performance data, current units and operational considerations. The paper concludes by considering future design moves.

Fiber metal acoustic material for gas turbine exhaust environments

FELTMETAL fiber metal acoustic materials function as broad band acoustic absorbers. Their acoustic energy absorbance occurs through viscous flow losses as sound waves pass through the tortuous pore structure of the material. Exhaust gas noise attenuation requirements are reviewed. Their selection process for higher performance materials is discussed. A new FELTMETAL fiber metal acoustic material has been designed for use in gas turbine auxiliary power unit exhaust environments without supplemental cooling. The physical and acoustic properties of mesh supported fiber metal acoustic medium FM 827 are discussed. Exposure testing was conducted under conditions which simulated auxiliary power unit operation. Weight gain and tensile strength data as a function of time of exposure at 650{sup 0}C (1202{sup 0}F) are reported. Fabrication of components with fiber metal acoustic materials is easily accomplished using standard roll forming and gas tungsten arc welding practices.

Fiber Metal Acoustic Material for Gas Turbine Exhaust Environments

FELTMETAL® fiber metal acoustic materials function as broad band acoustic absorbers. Their acoustic energy absorbance occurs through viscous flow losses as sound waves pass through the tortuous pore structure of the material. A new FELTMETAL® fiber metal acoustic material has been designed for use in gas turbine auxiliary power unit exhaust environments without supplemental cooling. The physical and acoustic properties of FM 827 are discussed. Exposure tests were conducted under conditions that simulated auxiliary power unit operation. Weight gain and tensile strength data as a function of time of exposure at 650°C (1202°F) are reported. Fabrication of components with fiber metal acoustic materials is easily accomplished using standard roll forming and gas tungsten arc welding practices.