Browse Topic: Gas turbines
This SAE Aerospace Recommended Practice (ARP) recommends a methodology to be used for the design, analysis and test evaluation of modern helicopter gas turbine propulsion system stability and transient response characteristics. This methodology utilizes the computational power of modern digital computers to more thoroughly analyze, simulate and bench-test the helicopter engine/rotor system speed control loop over the flight envelope. This up-front work results in significantly less effort expended during flight test and delivers a more effective system into service. The methodology presented herein is recommended for modern digital electronic propulsion control systems and also for traditional analog and hydromechanical systems.
This SAE Aerospace Information Report (AIR) outlines a recommended procedure for evaluation of the vibration environment to which the gas turbine engine powerplant is subjected in the helicopter installation. This analysis of engine vibration is normally demonstrated on a one-time basis upon initial certification, or after a major modification, of an engine/helicopter configuration. This AIR deals with linear vibration as measured on the basic case structure of the engine and not, for example, torsional vibration in drive shafting or vibration of a component within the engine such as a compressor or turbine airfoil. In summary, this AIR discusses the engine manufacturer’s "Installation Test Code" aspects of engine vibration and proposes an appropriate measurement method.
Fuel cell systems have achieved a significant level of technological maturity in ground-based mobility over the past two decades. In particular, commercially available fuel cell propulsion systems are now in serial production for passenger cars and city buses, and are already in regular commercial operation. In the segment of heavy-duty vehicles - such as trucks and other long-haul applications - small-series production and technology demonstrators are currently available and are on the verge of entering the mainstream market. These developments have resulted in well-proven system architectures, sophisticated balance-of-plant components, and established supply chains. In contrast, the utilization of fuel cell propulsion in aviation is still at a very early stage. At present, only a handful of individual prototypes and technology demonstrators - mostly for small aircraft - exist, while serial production remains far in the future. Particularly in the field of lightweight, small, electrical vertical take-off and landing (eVTOL) aircraft there is a unique opportunity to leverage the proven fuel cell systems developed for ground vehicles, adapt them, and further develop them to meet aviation-specific requirements. Such an approach can shorten development timelines and reduce technical risks. Transferring existing fuel cell technologies into aviation, however, is far from a straightforward process. One decisive difference lies in the required specific power density. Aircraft - especially eVTOL - demand significantly higher power densities than those delivered by current commercial fuel cell systems from the automotive sector. This requires a direct adjustment of the stack design and system architecture. Likewise, thermal management poses particular challenges. Whereas piston engines and gas turbines discharge a large portion of their waste heat via exhaust gases, fuel cells must remove all waste heat directly through their cooling systems. This requires efficient radiators capable of transferring heat from the coolant to ambient air. Larger radiator surfaces, however, increase both total aircraft mass and aerodynamic drag, making compact radiator designs essential for aviation applications.
For decades, researchers have recognized the potential of rotating detonation engines (RDEs) in powering the next generation of hypersonic air-breathing engines, rocket engines, and stationary power generation gas turbine systems. But realizing the potential has been fraught with challenges.
This SAE Aerospace Recommended Practice (ARP) is written for individuals associated with the ground-level testing of large and small gas turbine engines and particularly for those who might be interested in constructing new or adding to existing engine test cell facilities.
The test procedure per the applicable Engine Manual does require a vibration check for the low/intermediate and high speed rotor systems. Release of an engine with high vibrations can result in: On-wing vibration complaints, with subsequent troubleshooting Rotor system failures Premature engine removals Limits are provided for transient conditions and steady state data points. Troubleshooting recommendations are limited to verification of the proper signal input and tracking. This practice provides recommendations for: Correct cable and transmitter installation and connections Calibration Recorded data interpretation and data analysis
A new high-temperature resistant material exhibits great potential for applications such as energy-efficient aircraft turbines. Karlsruhe Institute of Technology, Karlsruhe, Germany A new material might contribute to a reduction of the fossil fuels consumed by aircraft engines and gas turbines in the future. A research team from Karlsruhe Institute of Technology (KIT) has developed a refractory metal-based alloy with properties unparalleled to date. The novel combination of chromium, molybdenum, and silicon is ductile at ambient temperature. With its melting temperature of about 2,000 degrees Celsius, it remains stable even at high temperatures and is at the same time oxidation resistant. The results are published in the journal Nature. High-temperature-resistant metallic materials are required for aircraft engines, gas turbines, X-ray units, and many other technical applications. Refractory metals such as tungsten, molybdenum, and chromium, whose melting points are around or higher than 2,000 degrees Celsius, can be most resistant to high temperatures. Their practical application, however, has limitations: They are brittle at room temperature and, in contact with oxygen, they start to oxidize causing failure within short time already at temperatures of 600 to 700 degrees Celsius. Therefore, they can only be used under technically complex vacuum conditions - for example as X-ray rotating anodes.
A new material might contribute to a reduction of the fossil fuels consumed by aircraft engines and gas turbines in the future. A research team from Karlsruhe Institute of Technology (KIT) has developed a refractory metal-based alloy with properties unparalleled to date. The novel combination of chromium, molybdenum, and silicon is ductile at ambient temperature. With its melting temperature of about 2,000 degrees Celsius, it remains stable even at high temperatures and is at the same time oxidation resistant. The results are published in the journal Nature.
This document is reissued for application to helicopters.
Manufacturers of fans/propellers using hydraulically-actuated pitch control claim energy efficiency gains up to 75% over fixed-pitch solutions. Unfortunately, the added cost, weight, reliability and maintenance considerations of hydraulic solutions has limited the introduction of pitch control for small-to-medium fans and propellers leaving a large market unserved by the efficiency gains associated with changing the pitch of a blade when the blade shaft’s speed changes. Pilot Systems International and Cool Mechatronics are developing an electromagnetically controlled pitch (EMCP) fan/propeller that will produce a new pareto optimal in size, weight, power, cost and cooling (SWaP-C2). The technology will substantially improve the efficiency of military ground vehicle cooling fans which is typically the third greatest power draw (~20kW)1 in the entire vehicle and provide critical performance improvements during silent watch. It will be a key enabler for the electrification of aircraft.
This document is reissued for application to helicopters.
Electrification could improve full-size rotorcraft performance by reducing peak turbine power demand, reducing transmission system weight and complexity, and reducing operating costs. Integrating electric machines with mechanical powertrains requires careful consideration of the system-level weight and efficiency impacts. This paper presents an optimization framework for evaluating parallel hybrid powertrain configurations using Geometric Programming (GP). Both retrofit and clean-sheet vehicle designs are considered. The results show that high-speed electric motors integrated into a parallel hybrid configuration using batteries can reduce the sized gas turbine power, enabling more efficient engine operation at lower power levels. For retrofit designs, with a fixed vehicle gross weight, adding batteries and motors reduces usable fuel, decreasing mission capability. Clean-sheet designs offer additional flexibility to re-size the vehicle and rotor, resulting in energy savings for an equivalent design mission.
The purpose of the NATO Next Generation Rotorcraft Capability (NGRC) Support Partnership funded Novel Powerplant concept study was to identify, analyze, and compare novel powerplant concepts that could fulfill the NGRC need in a solution-agnostic approach. The outcome of the study provided NSPA and the NGRC participating nations with increased knowledge and understanding of the powerplant domain to inform assessment of future NGRC platforms. This study modeled four aircraft configurations to derive propulsion sizing requirements and compared propulsion configurations for each. The propulsion system configurations considered included three levels of conventional gas turbine technology (In-service GT, 2025 GT, and 2035 GT), hybrid electric (battery), hybrid hydrogen fuel cell, and hydrogen combustion. The results of the study considered both quantitative and qualitative evaluations. The quantitative analysis determined aircraft and propulsion system sizing to align with the expected NGRC need at different max cruise speeds, and compared performance along with recurring, non-recurring, and operational costs for each. The qualitative analysis investigated the impacts of wider technical, capability, and supportability considerations for each propulsion concept. Assuming a notional NGRC entry into service target date of 2035, this study shows that, when considering both quantitative analysis and a qualitative review, a modern gas turbine is the most reasonable solution space to deliver the performance and multi-mission capability expected.
Improvement and evolution of all aircraft technologies and the commercialization of new technologies are essential to the carbon-net-zero goal of air mobility. Passenger aircraft are required to provide the ultimate in comfort, economy, and safety, and gas turbine engines will not disappear, while promoting the conversion to SAF and hydrogen fuels. The More Electric Engine (or MEE) concept, which has been proposed since the late 2000s, is one alternative. This paper focuses on the electrification of engine accessories. When the concept of electrification of engine accessories was first presented at Aerotech 10 years ago, the discussion at Aerotech seemed to be negative. Attaching a motor to conventional engine accessories would obviously increase the weight. Next, the conventional engine accessories are centrally controlled and only FADEC is in command, but electrification of engine accessories will increase the cost by adding intelligence to all the accessories. On a more academic level, a complete solution for the multiplicity required to ensure safety has not yet been clearly defined. Currently, electrification of engine accessories is not on the list of practical scenarios as far as the authors are aware. MEE is not only a technology that simply replaces power with electricity but is also a necessary technology to improve performance while keeping up with the latest technologies. Electrification and intelligence are inseparable due to their physical characteristics, and various industrial machinery systems and mobility systems have been innovated to take advantage of this relationship. This paper summarizes the concept of MEE technology required for aircraft in the 2040s and beyond, and the research results necessary to realize it. Finally, the background of how MEE can be used as a useful technology in the practical application of SAF and hydrogen-based fuels, which are realistically required in the 2040s and beyond, is summarized.
As the world looks to net-zero emissions goals, hybrid electric vehicles may play an increasingly important role. For passenger electric vehicles (EVs) that predominantly make short journeys but occasionally need to make longer trips, electrofuel range extension may be more cost effective than either hydrogen or rapid charging. Micro gas turbines and catalytic combustion show significant potential to deliver low-cost, low-maintenance, lightweight engines with virtually no emissions, and hydrocarbon consuming solid oxide fuel cells show even greater potential in these areas. Aditioanlly, sodium-ion batteries for EVs, dispatachable vehicle-to-grid power and buffering, and variable intermittent renewable energy could also play key roles. The Role of Hybrid Vehicles in a Net-zero Transport System explores the costs, considerations, and challenges facing these technologies. Click here to access the full SAE EDGETM Research Report portfolio.
Liquid jet atomization is one of the key processes in many engineering applications, such as IC engines, gas turbines, and the like, to name a few. Simulating this process using a pure Eulerian or a pure Lagrangian framework has its own drawbacks. The Eulerian–Lagrangian spray atomization (ELSA) modeling seems like a viable alternative in such scenarios. ELSA simulations consist of solving an additional transport equation for the surface area density (Σ) of the issuing jet. In this study we have proposed a dynamic approach to compute the turbulent timescale constant (α1), which appears in the source of Σ-transport equation and is responsible for restoring the surface area back to its equilibrium. The dynamic approach involves an analytical computation of the turbulent timescale constant (α1), thereby eliminating the need for ad hoc adjustments to surface area values during computational fluid dynamics (CFD) simulations. Unlike previous research which suggests using constant values in the range (0, 1] for the α1-constant, we found that these values can be as high as 60,000 for the engine combustion network (ECN) spray-A nozzle conditions. The analytical closure procedure dampens the spurious overshoots seen in the sigma-Y field and maintains values close to the equilibrium conditions. The proposed approach is implemented in CONVERGE, a commercially available CFD code and validated by comparing against available experimental data.
Additive manufacturing (AM) is currently the most sought-after production process for any complex shaped geometries commonly encountered in Aerospace Industries. Although, several technologies of AM do exits, the most popular one is the Direct Metal Laser Sintering (DMLS) owing to its high versatility in terms of precision of geometries of components and guarantee of highest levels of reduction in production time. Further, metallic component of any complex shape such as Gas Turbine Blades can also be developed by this technique. In the light of the above, the present work focuses on development of iron silicon carbide (Fe-SiC) complex part for ball screw assembly using DMLS technique. The optimized process parameters, hardness and wear resistance of the developed iron-SiC composite will be reported. Further, since the material chosen is a metallic composite one, the effect of SiC on the thermal stresses generated during the DMLS processing of Fe-SiC composite will also be discussed. A novel approach to testing of wear resistance of the developed component will also be presented in this paper. The developed composite component exhibited lesser wear scars even after 1-lakh cycles of operation indicating excellent wear resistance. It is also observed that increased content of SiC in the developed composite results in higher extent of thermal stresses.
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