Abstract: As the Lycoming engine had failed its attempt on using variable valve timing for aircraft piston engine back in 1940s, the idea of the technology was abandoned as the turbines were then introduced in the aviation for better performance and greater power. Since piston engines produce smaller power efficiently in the low speed than turbine engines, they are presently still practically used in most of lightweight aircraft. With the use of a variable valve timing mechanism, it may help to increase the amount of air inlet and to provide more power output with lesser fuel consumption. With the use of this new valve system, improvements in the performance of automobile engines have been recorded. The indicated improvements, however, are limited to automobile engines running with high revolutions only. Engine simulation program was run in this investigation as an attempt to predict engine performances that are appropriate for lightweight aircraft.
Abstract: Flying activities of sport aviation vehicles normally use Internal Combustion Engines (ICE) for their powerplant, which emits Carbon Dioxide (CO2) and also produces noise. Environmental issues regarding harmful gas emission and noise may restrict the sport aviation activities and resulting in reduction of interest in flying as a sport activity. The feasible solution for this issue is by replacing the Internal Combustion Engines (ICE) with Electric Engines on all sport flying vehicles. The Modenas CTric Electric Engines was tested to measure the parameters required by comparable Internal Combustion Engine used by sport aviation flyers. Other parameters; engine endurance, temperature and performance, were also tested. The bench test was conducted using specially design test rig. The results show that there is a possibility for the Modenas CTric Motorcycles Electric Engine used as an alternate source of powerplant for paramotors and microlight aircraft. However, there is penalty on the vehicle payloads due to weight of the battery. Lighter battery technology integration is to be developed to reduce the weight of the flight vehicles. This study serves as a platform for further work in electric engine technology for commercial aircraft application. Availability of green engine (no emission and noise output) will generate more interest in sport aviation activities and prepare for the future commercial Electric Engine aircraft application.
Abstract: Due to the lack of historical data, sealing performance of O-rings in the fuel system of aircraft engines is particularly difficult to study. As great efforts are being made to develop alternative fuels in aviation industry, their compatibility issue with elastomeric O-ring materials has become a major concern. So far, no data has been published on how O-rings would behave in alternative fuel scenario while taking the temperature factor into consideration. The purpose of this paper is to investigate into O-ring’s sealing performance under various temperature conditions, with comparison between Gas-to-Liquid (GtL) synthetic fuel and Jet A-1. Technique used to stimulate the real service scenario for O-rings is the stress relaxation test. Distinguishing from regular relaxation techniques, an advanced stress relaxation rig (Elastocon EB17) with the capability of temperature cycling was employed for this study. Nitrile and fluorosilicone O-ring materials which are commonly found in the fuel system were tested respectively. Three sets of tests were designed to look at how each O-ring material will behave under different temperature conditions. Results obtained so far indicated under extremely low temperature conditions, the relaxation processes of both O-ring materials seem to be ‘frozen’ as the sealing force stops decreasing and maintains a relatively stable level. No fuel preference has shown during the process as O-rings in both GtL and Jet A-1 behaved similarly. Nitrile O-ring showed better relaxation characteristic in Jet A-1 than that in GtL under the 24-hour temperature cycling test; while fluorosilicone presented little differences in these two fuels.
Abstract: This study was carried out to investigate the effects of different cooling holes configurations on the thermal field characteristics inside a combustor simulator. In this research, a three-dimensional presentation of a true Pratt and Whitney aero-engine was simulated and analyzed. This combustor simulator combined the interaction of two rows of dilution jets, which were staggered in the stream wise direction and aligned in the span wise direction. The findings of the study indicate that the thickness of the film-cooling layer was thicker for the greater penetration depth. Furthermore, for the combustor simulator with more cooling holes, the temperature near the wall and between the jets was slightly increased. Also at the leading edge of the jet, the gradients of temperature were quite high at the jet-mainstream interface.
Abstract: A nonlinear mathematical model with thermodynamic relations permitting an accurate assessment of the dynamic influence on performance is developed in this study. The model is used within the framework of engine design in the development stage and in implementation stage. The use of simulations can give an invaluable insight into transient response and control problems; a significant saving is achieved with minimum test bed hardware development without endangering an engine. Successful simulations have been carried out using the proposed algorithm; an application utilizing Object Orientated Programming (OOP) was developed. The results obtained by the present developed model are in fair agreement with available experimental data.
Abstract: Most landing gears used in aircraft employ very efficient oleo-pneumatic dampers to absorb and dissipate the impact kinetic energy of the aircraft body frame. A single-acting shock absorber is most commonly used in the oleo strut that has a metering pin extending through the orifice, which can vary the orifice area upon compression and extension of the strut. This variation is adjusted by shaping the metering pin so that the strut load is fairly constant under dynamic loading. In this paper, it is proposed to further change the damping coefficient as a function of time in order to achieve a semi-active control of the aircraft vibrations during landing by using Magnetorheological (MR) fluid in the Oleo. With the metering pin designed for a nominal flight condition, further variation in the fluid viscosity would help achieve the optimal performance in off-nominal flight conditions. A simulation approach is employed to show the effect of different profiles for viscosity variation in the MR fluid. The utility of such a damper can be very well exploited to include different criteria such as the landing distance after touchdown. This type of system can be used also in Unmanned Aerial Vehicle (UAV) application where the focus of design may be to accomplish the task without the consideration of passenger comfort.
Abstract: This paper presents a methodology to design the optimum proprotor for tilt-body micro-air-vehicles (TB-MAV) with efficient global propulsion system and long flight endurance in both cruise and hover modes. The TB-MAV developed at ISAE, which is called MAVion, was used as a baseline in the design process. To acquire maximum performance of TB-MAV’s global propulsion system, an efficient optimization process of the proprotor propulsion system was carried out. The optimization process consists of two-step inverse design methods. The first step determines the optimal operating conditions in terms of power and rotational speed of proprotor and the second step designs the optimal blade geometry in terms of twist angle distribution. The optimal blade twist distribution along the blade was computed using the Glauert’s strip theory for minimum energy loss condition. Meanwhile, the optimal operating conditions were determined by the motor outputs corresponding to high motor efficiency. A comparison of performance in terms of total efficiency and flight endurance between the optimized flexible proprotor, the optimized rigid proprotor, optimized propeller and optimized rotor is presented.
Abstract: Aircraft redesign process normally does not start from scratch and requires a well-defined reference baseline design as the starting point for redesign changes. In general, the baseline design is often chosen based on the closeness of its existing performance capability to the driving requirement. This practice essentially presumes that such condition guarantees a minimum amount of required redesign changes, hence the least development risk. However, it is argued here in this study that such notion can be misleading because risk also depends on the type and the extent of the changes. Instead, it is believed that the existing baseline design architecture is an important element that will influence its suitability for the redesign task at hand. Through a sample aircraft redesign case study, the possible effects of existing design architecture on the redesign process is demonstrated and highlighted.
Abstract: Product development process involves conceptual design selection, which is an activity engaging with numerous types of data including technical-customer specifications and current design developments. This paper presents a conceptual design selection which employs a new technique which accommodates Concurrent Engineering (CE) – Multi Criteria Decision Making (MCDM) strategies. This new technique combines Concurrent Network (CE-ANP), Quality Function Deployment (QFD) and Analytical Hierarchy Process (AHP), referred as CoNQA. To illustrate this technique, a case study is presented involving aerospace application which is the selection of wing spar material. The result shows that the proposed new technique proved to be a sound method which considers product performance, product specification, technical specifications and selection of the best alternative in the selection process. This new method should be a useful aid for designers in collaboration with engineers to perform systematic and parallel technique involving early consideration of technical-customer requirements during conceptual design, hence to establish good product design and increase product competitiveness.
Abstract: The solar-powered aircraft represents a major step forward in environmentally friendly vehicle technology. An unmanned aircraft vehicle (UAV) was designed to fly for 24 hours continuously to achieve surveillance at low altitude. It is a lightweight, solar-powered, remotely piloted flying wing aircraft that is demonstrating the technology of applying solar power for long-duration and low-altitude flight. Several programs and codes were used in the designing process of the UAV and generating its layout. A MATLAB computer programming code was written to optimize on various values of aspect ratio (AR) and wingspan (b) after setting the mission requirements and estimating the technological parameters. A program called Java Foil was used to calculate the lift. Another program called RDS was used to obtain the final layout of the aircraft. The great benefit is that the design is general enough to be applied to different values of aspect ratio and wingspan. Moreover, the analytical form of the method allows identifying clear some general principles like the optimization on various values of aspect ratio and wingspan, and the calculation of the lift.