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Abstract Many interconnected parameters are involved in the helicopter turboshaft engine’s design, implying numerous limitations on the design process. These parameters include the key parameters such as weight, dimensions, power, specific fuel consumption, combustion temperature, air mass flow rate, and compressor pressure ratio, all of which correlate with one another and collectively affect the engine’s design process and consequently the helicopter. The first step in any design process is the conceptual design stage, where using an initial guess, an iterative parameter estimation runs until convergence. For the initial guess, a database is required, and for estimation, knowledge of the relationships between different parameters is mandatory.

Abstract Electrostatic discharge during aircraft refueling operations has long been recognized as a safety hazard. To reduce the chances of this happening, different practices were developed, the most common being the addition of a static dissipator additive (SDA). Nowadays, the SDA is a well-established requirement in all the leading jet-fuel specifications and is in widespread use in commercial and military aviation industries. To deepen the understanding of the electrostatic behavior of nonconductive jet fuel and SDA, the Israeli Air Force (IAF) has conducted small-scale refueling tests in a simulated aircraft fuel tank. In these tests, the effect of flow rate, residence time, SDA concentration, bounding, grounding, and the method of filling were evaluated by measuring the electrostatic field strength generated. The simulation of the aircraft fuel tank was obtained using a nonconductive plastic tank jointed with a small faucet at the bottom.

The paper was originally published with the incorrect author reference in the citation. The correct citation should appear as follows: Murrieta-Mendoza, A., Botez, R., Ruiz, H., and Kessaci, S., “Particle Swarm Optimization with Required Time of Arrival Constraint for Aircraft Trajectory,” SAE Int. J. Aerosp. 13(2):269-291, 2020, doi:10.4271/01-13-02-0020.

Abstract The airline industry faces a crisis in the future as consumer demand is increasing, but the environmental effects and depleting resources of kerosene mean that growth is unsustainable. Hydrogen is touted as the leading candidate to replace kerosene, but it needs significant technological and economical endeavors. In such a scenario, cryogenic liquid hydrogen (LH2) is predicted to be the most feasible method of using hydrogen. The major challenge of LH2 as an aircraft fuel is that it requires approximately four times the storage volume of kerosene—due to its lower density. Thus the design of cryogenic storage tanks to handle larger quantities of fuel is becoming increasingly important. But the increase in drag associated with larger storage tanks causes an increase in fuel consumption. Hence, this paper aims to evaluate the aerodynamic performance of different storage configurations and aid in the selection of an economic and efficient storage system.

Abstract Global warming has motivated the aeronautical industry to develop new technologies that will reduce polluting emissions. A direct way to achieve this goal is to reduce fuel consumption. Reference trajectory optimization contributes to this goal by guiding aircraft to zones where meteorological conditions are favorable to execute their required missions and thereby to reduce flight costs. In this article, the reference trajectory was optimized in terms of geographical position, altitude, and speed, by taking into account a Required Time of Arrival (RTA) constraint and weather conditions. The algorithm assumes that there is no traffic and that the aircraft can fly anywhere in the search space. The search space was modeled in the form of a unidirectional weighted graph, fuel burn was computed using a numerical model, and the weather forecast was taken into account.

Abstract There has been an increased interest as regards the use of biofuels in aviation gas turbine engines due to global efforts to reduce greenhouse gas emissions along with fluctuating jet fuel prices. This work researches the use of soap-derived biokerosene (SBK) in aircraft engines. SBK is a promising biofuel option for emerging tropical countries as its production requires a relatively simple technology, and its feedstock sources are abundant in these countries. Blends of Jet A-1 with up to 20 vol.% SBK were tested on a 1S/60 Rover gas turbine engine over a range of brake powers to measure engine performance and emissions. The results were then compared to those of pure Jet A-1. It shows that the engine running on SBK/Jet A-1 blends and pure Jet A-1 have almost similar engine performance parameters including engine efficiency, specific fuel consumption (SFC), turbine inlet temperature (TIT), and exhaust gas temperature (EGT).

Abstract Federal Aviation Administration (FAA)’s 20 years of research and development with 200 unleaded blends and full-scale engine tests on 45 high-octane unleaded blends has not found a “drop-in” unleaded replacement for aviation gasoline (AVGAS) 100 low lead (100LL) fuel. In this study, analysis of compatibility via optimization of Lycoming O-320 engine fuelled with RON 97, RON 98, RON 100, and AVGAS was conducted using the Response Surface Methodology (RSM). Test fuels were compositionally characterized based on Gas Chromatography (GC) analysis and were categorized based on types of Hydrocarbon (HC). Basic fuel properties of fuels in this research were analyzed and recorded. For optimization analysis, engine speed and fuel were considered as the input parameters.

Abstract More than a decade ago, we proposed combined use of direct injection (DI) and jet ignition (JI) to produce high efficiency, high power-density, positive-ignition (PI), lean burn stratified, internal combustion engines (ICEs). Adopting this concept, the latest FIA F1 engines, which are electrically assisted, turbocharged, directly injected, jet ignited, gasoline engines and work lean stratified in a highly boosted environment, have delivered peak power fuel conversion efficiencies well above 46%, with specific power densities more than 340 kW/liter. The concept, further evolved, is here presented for unmanned aerial vehicle (UAV) applications. Results of simulations for a new DI JI ICE with rotary valve, being super-turbocharged and having gasoline or methanol as working fuel, show the opportunity to achieve even larger power densities, up to 430 kW/liter, while delivering a near-constant torque and, consequently, a nearly linear power curve over a wide range of speeds.

Abstract High-altitude long-endurance (HALE) unmanned aerial vehicles (UAVs) are used for high flight altitudes, which enable low drag and fast flight with minimal fuel consumption. Two-stage turbocharging is necessary to sustain sea-level power at high flight altitudes. In this study, the limitations of two-stage turbocharging at high flight altitudes typical for HALE UAVs are analyzed for the first time. The obtained results show that the minimum available engine power increases as the altitude rises. This will limit the ability of the aircraft to descend rapidly. Furthermore, at high altitudes, if a lower operating point is required for a fast descent, further recovery to full power for climbing or cruising could be unavailable. In the latter cases, a lower altitude must be reached before full power would be available again. A basic algorithm for the assessment and analysis of the limitations of UAV engines with two-stage turbochargers operating at high altitudes is suggested.