Authors:T.A. Granberg; T. Polishchuk, V. Polishchuk, C. Schmidt Pages: 567 - 585 Abstract: Route planning and airspace sectorisation are two central tasks in air traffic management.Traditionally, the routing and sectorisation problems were considered separately, with aircraft trajectories serving as input to the sectorisation problem and, reciprocally, sectors being part of the input to the path finding algorithms.In this paper we propose a simultaneous design of routes and sectors for a transition airspace. We compare two approaches for this integrated design: one based on mixed integer programming, and one Voronoi-based model that separates potential “hotspots” of controller activity resulting from the terminal routes.We apply our two approaches to the design of Stockholm Terminal Maneuvering Area. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.29 Issue No:Vol. 123, No. 1263 (2019)
Authors:D. Hwang; Y. Song, K. Ahn Pages: 586 - 599 Abstract: The combustion instability characteristics in a model dump combustor with an exhaust nozzle were experimentally investigated. The first objective was to understand the effects of operating conditions and geometric conditions on combustion instability. The second objective was to examine more generalised parameters that affect the onset of combustion instability. Three different premixed gases consisting of air and hydrocarbon fuels (C2H4, C2H6, C3H8) were burnt in the dump combustor at various inlet velocity, equivalence ratio and combustion chamber length. Dynamic pressure transducer and photomultiplier tube with a bandpass filter were used to measure pressure fluctuation and CH* chemiluminescence data. Peak frequencies and their maximum power spectral densities of pressure fluctuations at same equivalence ratios showed different trends for each fuel. However, the dynamic combustion characteristics of pressure fluctuations displayed consistent results under similar characteristics chemistry times regardless of the used hydrocarbon fuels. The results showed that characteristic chemistry time and characteristic convection time influenced combustion instabilities. It was found that the convective-acoustic combustion instability could be prevented by increasing the characteristic chemistry time and characteristic convection time. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.19 Issue No:Vol. 123, No. 1263 (2019)
Authors:P. Janhunen; P. Toivanen, K. Ruosteenoja Pages: 600 - 616 Abstract: Launching orbital and suborbital rockets from a high altitude is beneficial because of e.g. nozzle optimisation and reduced drag. Aircraft and gas balloons have been used for the purpose. Here we present a concept where a balloon is filled with pure water vapour on ground so that it rises to the launch altitude. The system resembles a gas balloon because no onboard energy source is carried, and no hard objects fall down. We simulate the ascent behaviour of the balloon. In the baseline simulation, we consider a 10 tonne rocket lifted to an altitude of 18 km.We model the trajectory of the balloon by taking into account steam adiabatic cooling, surface cooling, water condensation and balloon aerodynamic drag. The required steam mass proves to be only 1.4 times the mass of the rocket stage, and the ascent time is around 10 minutes. For small payloads, surface cooling increases the relative amount of steam needed, unless insulation is applied to the balloon skin. The ground-filled steam balloon seems to be an attractive and sustainable method of lifting payloads such as rockets into high altitude. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.10 Issue No:Vol. 123, No. 1263 (2019)
Authors:B. Khandelwal; J. Cronly, I.S. Ahmed, C.J. Wijesinghe, C. Lewis Pages: 617 - 634 Abstract: There 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. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.16 Issue No:Vol. 123, No. 1263 (2019)
Authors:D.C. Su; Y.J. Shi, G.H. Xu Pages: 635 - 657 Abstract: Numerical simulations of ship/rotor-coupled flowfield have been performed to investigate the rotational direction effects on a shipborne single-rotor helicopter in different deck landing trajectories (i.e., lateral and longitudinal translation) based on Reynolds-averaged Navier-Stokes (RANS) solver. Both the momentum source model and moving overset mesh model are employed to simulate the effect of the rotor on the ship airwake for different levels of fidelity requirement. The aerodynamic loading characteristics in terms of time-averaged and root-mean-square (RMS) thrust and pitch and roll moments are compared for two helicopter rotors with opposite rotation directions in a starboard 30 degrees wind condition. The time-averaged results show that the mean thrust of a counterclockwise rotor is greater than that of a clockwise rotor, particularly in the lateral translation phase. This suggests that a helicopter with a counterclockwise rotor could provide more collective control margin under this condition. Furthermore, a more significant reduction in pitch moment is experienced by the counterclockwise rotor during the two landing trajectories, and thus the effect of the aircraft being pulled towards the hangar tends to be more severe on the helicopter with the counterclockwise rotor. RMS loading results indicate that the unsteady loading levels on the clockwise rotor are much higher than that of the counterclockwise rotor in all three axes for most of the lateral and longitudinal translation phases. As a result, the pilot is likely to experience a higher workload when operating a helicopter with a clockwise rotor in the case of a deck landing in this wind condition. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.20 Issue No:Vol. 123, No. 1263 (2019)
Authors:K. Zhao; D. Kennedy, C.A. Featherston Pages: 658 - 677 Abstract: Stiffened wing and fuselage panels often have a postbuckling reserve of strength, enabling them to carry loads far in excess of their critical buckling loads. Therefore allowing for postbuckling in design can reduce their weight, hence reducing fuel consumption and environmental impact. The present paper extends the postbuckling analysis in the exact strip software VICONOPT to more accurately reflect the skewed mode shapes arising from shear load and anisotropy. Such mode shapes are represented by a series of sinusoidal responses with different half-wavelengths which are coupled together using Lagrangian multipliers to enforce the boundary conditions. In postbuckling analysis the in-plane deflections involve responses with additional half-wavelengths which are absent from the out-of-plane deflection series. Numerical results are presented and compared with finite element analysis for validation. The present analysis gives close results compared to the finite element and finite strip methods and saves computational time significantly. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.27 Issue No:Vol. 123, No. 1263 (2019)
Authors:S. Nguyen; M. Corey, W. Chan, E.S. Greenhalgh, J.M.R. Graham Pages: 678 - 705 Abstract: To accurately predict the probabilities of impact damage to aircraft from runway debris, it is important to understand and quantify the aerodynamic forces that contribute to runway debris lofting. These lift and drag forces were therefore measured in experiments with various bodies spun over a range of angular velocities and Reynolds numbers. For a smooth sphere, the Magnus effect was observed for ratios of spin speed to flow speed between 0.3 and 0.4, but a negative Magnus force was observed at high Reynolds numbers as a transitional boundary layer region was approached. Similar relationships between lift and spin rate were found for both cube- and cylinder-shaped test objects, particularly with a ratio of spin speed to flow speed above 0.3, which suggested comparable separation patterns between rapidly spinning cubes and cylinders. A tumbling smooth ellipsoid had aerodynamic characteristics similar to that of a smooth sphere at a high spin rate. Surface roughness in the form of attached sandpaper increased the average lift on the cylinder by 24%, and approximately doubled the lift acting on the ellipsoid in both rolling and tumbling configurations. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.15 Issue No:Vol. 123, No. 1263 (2019)
Authors:J. Tang; X. Wang, D. Duan, W. Xie Pages: 706 - 726 Abstract: An improved variational optimization approach is established to optimize and analyse the propulsion efficiency of the high-altitude contra-rotating propellers for high-altitude airships based on the Vortex Lattice Lifting Line Method. The optimum radial circulation distribution, chord and pitch distribution are optimized under the maximum lift-to-drag ratio of aerofoils. To consider the effects of the actual Reynolds number and the Mach number of each aerofoil section, aerodynamics such as lift coefficient, drag coefficient and lift-to-ratio are obtained by interpolating a CFD database, which is established by numerical simulations under different Reynolds number, Mach number and angles-of-attack. The improved method is verified by validation cases on a high-altitude CRP using the three-dimensional steady Reynolds-averaged Navier-Stokes solver and moving reference frames technique. The optimization results of thrust, torque and efficiency for both the individual front/rear propeller and CRP are shown to agree reasonably well with the CFD results. Using the improved approach, the influence of blade numbers, diameter, rotation speeds, axial distance and torque ratio on the optimum efficiency of CRPs is illustrated in detail by conducting parametric studies. PubDate: 2019-05-01T00:00:00.000Z DOI: 10.1017/aer.2019.14 Issue No:Vol. 123, No. 1263 (2019)
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