Applied Mechanics and Materials Vols. 465-466

Abstract: It is in the interest of proponents of biodiesel to increase the utilization of the renewable fuel. The similarities of the methyl ester properties to diesel fuel and its miscibility proved to be an attractive advantage. It is however generally accepted that there are some performance and emissions deficit when a diesel engine is operated with biodiesel. There are research efforts to improve the diesel engine design to optimize the combustion with biodiesel. Since the common rail engines operates on flexible injection strategies, there exist an opportunity to improve engine performance and offset the fuel economy deficit by means of optimizing the engine control strategies. This approach may prove to be more practical and easily implemented. This study investigated the effects of the fuel injection parameters - rail pressure, injection duration and injection timing - on a common rail passenger car engine in terms of the fuel economy. Palm oil based biodiesel up to 30% blend in diesel was used in this study. The end of injection, (EOI), was found to be the most important parameter for affecting fuel consumption and thermal efficiency.

Abstract: The aim of this research is to indicate a steam double effect chiller-heater equipped with solar heat pipe in a certain space with the area of 975 m² located in Tehran, which is currently equipped with a direct-fired single effect absorption chiller-heater. Thereafter , the most obvious differences of the two chiller-heater systems are compared: the solar cooling system increases coefficient of performance as high as 0.54, decreases CO₂ dissemination by 829 tons in each year, and reduces energy consumption by 1552.42 MWh/Yr. Economic analysis of the two systems using break-even-point showed that the use of solar system is attractive in applications that have excess thermal energy, and the conversion of this energy to higher value energy markets is to be more profitable than absorption gas-fired system from 13^th year on. Keywords: Technical-economic analysis, energy optimization, solar chiller, absorption chiller-heater, solar heat pipe.

Abstract: Spin-off maneuver of a flexible satellite using constant-amplitude thrusters is studied in this paper. The satellite consists of a rigid main body and two symmetrical solar panels. The panels are having structural flexibility and their motions are discretized following the finite element method. Under constant-amplitude thrusts, steady-state attitude angle oscillations may occur in large amplitude after the maneuvers. Since in operation the satellite should point to certain area on the earth precisely, these oscillations of course are not acceptable. To reduce the oscillations, proportional derivative (PD) based constant-amplitude input shaping logic is proposed to determine time locations of thruster switching. Then, under such inputs, spin-downs of the satellite are simulated numerically. Results of simulations indicate that the precise orientation of the satellite can be achieved.

Abstract: Unmanned Aerial Vehicle (UAV) has an enormous role to both military and civilian missions. However, a short range endurance of current UAV system affects the life expediency, data monitoring, and output performance of a mission. This is due to having UAVs that are dependent on batteries. The weight of the battery and low temperature environment has undoubtedly been the main cause for the poor UAV performance. In spite of its prolific improvement in UAV system, the endurance permissible is between 45 minutes to 4 hours. Therefore, this situation makes battery no longer attractive to be widely used for UAV. Lately attention has been focused on the use of solar cell in UAV in replacement to battery as its power system. Nevertheless, current solar cells characteristic and efficiency is insufficient to sustain a long endurance flight. This is due to failure to identify an appropriate selection of material and parts in designing the UAVs solar augmented power module system. Therefore, comprehensive work on the solar power system and its integration is essential for an excellent UAV performance. Thus, a research work has been done to studies on the design of a solar and battery power system for an electric UAV. Subsequently, a small solar powered electric UAV has been developed. As a result, the UAVs specification, layout and systems description are presented extensively in this paper. This UAV has enabled an understanding how the solar augmented system has enhanced the endurance performance the electric UAV to almost 24 hours. Moreover, this UAV has 5 successfully flight up till date with useful data that predicted this UAV aerodynamic characteristic.

Abstract: High-aspect-ratio wings, with the inherent nature of maximizing the lift-to-drag ratio, have been widely employed in modern airplanes. However, highly flexibility wing structure renders previous rigid model in aerodynamic simulation and ideal aerodynamic force distribution in structural simulation meet serious challenges. In this article, a high fidelity aero-structural coupled method is employed to better evaluating the deformation of a high-aspect-ratio wing. Summarily, this method takes into consideration the aerodynamic redistribution and the geometrical nonlinearity caused by large deformation of the wing, and the deflection calculated using coupled method is approximately 20% more than traditional unidirectional method, providing a more accurate model for structural design and optimization.

Abstract: This study presents Two Dimensional Compressible Flow Analysis Over a Generic Cruise Missile Model. The aerodynamics analysis carried out by use of Fluent Software. Here the pertinent Cruise missile geometry data had been chosen is BGM-109 tomahawk missile. Basically the flow problem around this missile model is a three dimensional flow problem. Treating the flow problem in view as two dimensional flow case, since their result will be used as a comparison purposes with the CFD code which currently under development. The aerodynamics analysis of this missile model carried at the free stream Mach number M = 0.7 for three different angle of attacks α = - 5⁰, 0 and α = 5⁰ . Here the flow is treated as an inviscid compressible flow applied to the missile configuration as (1) fuselage alone, (2) a combined configuration as fuselage and tail and (3) as wing body tail configuration. The results obtained by use of fluent software for those three configurations indicate the flow pattern surrounding object in term of flow properties ( pressure, density and Mach number ) change significantly between the missile as fuselage alone and their other combined configurations. As the angle of attack increase the change of flow pattern surrounding the missile become apparently compared to flow pattern at zero angle of attack. In addition to this, a symmetrical solution between the result at angle of attack α = 5⁰ and α = -5⁰ are also found.

Abstract: The present work focuses on the development of computer code related to the longitudinal stability analysis on a propeller driven light aircraft model. The computer code designed in such a way, so for a given aircraft data will produce the result in term of: 1) Longitudinal stability derivatives in non dimensional form as well as in their dimensional form, 2) The longitudinal stability aircraft characteristics related to position of neutral point ( stick free and stick fixed ) also the requested forces for deflecting the control surface, 3) The transfer function in response to the control surface deflection for the component velocity and pitch angle. Through this developed computer code one can make an assessment the longitudinal behavior for the propeller driven light aircraft [.

Abstract: This paper presents the experimental determination of the moment of inertia of USM e-UAV by using pendulum method. Compound pendulum experiment is used to determine the moment of inertia about x and y axes while the moment of inertia about z-axis is determined using bifilar torsion pendulum method. An experimental setup is developed with appropriate dimension to accommodate USM e-UAV. Experimental data are presented and discussed.

Abstract: Cargo transportation is a very serious business and cost of delivering a pound of cargo for a mile keeps rising every day. Today, there are two options exist; fast but expensive aircraft and slow but inexpensive sea freight. A Hybrid Air Vehicle (HAV) was designed to solve this problem by combining the aerodynamic lift advantages from a lifting body shape and the effectiveness of lighter than air from buoyancy. These combined lifting capabilities gave the HAV enough lifting force to carry additional cargo compared to aircraft and its propeller engine gave it the ability to travel relatively fast compared to sea freight. The cost of transporting a pound of cargo a mile using proposed HAV is $ 0.00022/lb-mile as compared to $0.00043/lb-mile for C-5 Galaxy which translates to nearly 48% saving. The HAV cost 1000% more than sea freight but it is 647% faster.

Abstract: The fly of wing-in-ground effect (WIG) crafts can be affected by ground boundary layers. In this study, the effect of ground viscous on aerodynamic coefficients of a compound wing of WIG craft was numerically investigated. Computational fluid dynamics (CFD) was used for numerical study. The simulations were done respect to different ground clearance and Reynolds number. A realizable k-ε turbulent model was employed for the modelling flow field around the wing area. The numerical results of the compound wing for fixed ground validated with the experimental data. Aerodynamic coefficients of the compound wing were determined for fixed and moving ground. Accordingly, the numerical result presented that lift and drag coefficients and lift to drag ratio has been affected by ground boundary layers while moment coefficient and centre of pressure of compound wing had no more variation due to remove ground viscous. The effect of ground viscous on aerodynamics of the compound wing had a slight changes respect to Reynolds number. CFD can be employed as a good method to find the influence of ground viscous on aerodynamics of WIG crafts.