Journal of Aerospace Science and Technology
Volume:15 Issue: 2, Summer and Autumn 2022

Recently, engineering systems are quite large and complicated. Conceptual design process of Space Transportation Systems (STSs) is a multidisciplinary task which must take into account interactions of various disciplines and analysis codes. Current approach for the conceptual design of STSs requires the evaluation of a large number of different configurations and concepts. With existing legacy codes, estimating the performance of all design combinations becomes very time consuming and computationally expensive. A possible solution to this problem could be employing of surrogates during design tasks. This paper describes an effort to optimize the design of an entire STS to achieve a low Earth orbit, consisting of multiple stages using an efficient surrogate-based Multidisciplinary Design Optimization (MDO) framework with the goal of minimizing vehicle weight and ultimately vehicle cost. Furthermore, a combination of Response Surface Methodology (RSM) and Kriging surrogates has been used for building surrogate models. The disciplines of aerodynamics, propulsion, trajectory simulation, geometry, and mass properties, have been integrated to produce an engineering system model of the entire vehicle. In addition, the system model has been validated using the existing design data of STS’s trajectory and their subsystems. For the design optimization, in order to ensure that the payload achieves the desired orbit, a hybrid algorithm has been used to minimize the deference between the actual and desired orbital parameters. The objective function of the optimization problem is to minimize the overall system mass, thus minimizing the system cost per launch. The proposed design and optimization methodology provides designers with an efficient and powerful approach in computation during designing space transportation systems and can also be developed for more complex industrial design problems with comparable characteristics.

Importance of study of pulsating heat pipes (PHPs) behavior and limitations in conducting experimental studies, the necessity of numerical simulations is getting critical in this area. In present work, numerical simulations are carried out for pulsating heat pipes. Thermal performance of closed loop pulsating heat pipes is investigated at different operating conditions such as evaporator heating power and filling ratio. Water, ethanol, methanol and acetone are employed as working fluids. A two-dimensional single loop PHP is used for present study. Computational Fluid Dynamics (CFD) video technique is employed for flow visualization purpose. Perfect match was observed between the present CFD video clip and previous experimental video-based studies in terms of flow pattern and behavior. Present study shows how researchers can benefit from developments of numerical tools to test pulsating heat pipes behavior at different operating conditions or different working fluids without facing difficulties and limitations of applying laboratory thermal measurement equipment or high-speed cameras. The CFD video clip as result of numerical simulation was found very informative for flow visualization purpose. The simulated clip made it much easier to capture phenomena occur in a pulsating heat pipe. The thermal performance investigation at different operating conditions and working fluids was found very informative in terms of application and design purposes especially for experimental studies. By increasing heating power greater than 60 W, circulation velocity was increased for most cases. Phase contour videos are inserted at the bottom of the article.

Unmanned Aerial Vehicles (UAVs) have numerous applications in military, commercial and hobby fields. Among these vehicles, drones with vertical take-off and landing (VTOL) capability have attracted more attention due to their specific capabilities such as better maneuverability and hover flight. In recent years, numerous concepts emerged which trying to propose new configurations to enhance UAVs performance. In this paper, we propose a novel concept which integrates single main rotor helicopter and quadrotor structure to overcome some difficulties exist in those applications. This suggested configuration, include a variable pitch main rotor equipped with four smaller counterrotating rotors to overcome its opposite torque (instead of a tail rotor in helicopters) and also sustain a portion of the UAV weight which make it possible to use a smaller main rotor. This design preserves maneuverability of helicopters, while eliminates tail rotor power loss and its asymmetric lateral force and also enhances the flight stability and maneuverability by properly using other four rotors’ thrusts. Preliminary dynamic modeling and control system design are presented in the text and the results show that this idea can be investigated further. The next steps are planned to be studied in next researches.

In this research, the thermodynamic analysis of a three-spool mixed-flow turbofan engine has been studied by examining parameters such as flight altitude, flight Mach number, fan pressure ratio, high and Intermediate-pressure compressor pressure ratios, bypass ratio and burner exit temperature. First, the effect of these parameters on the thrust, thrust specific fuel consumption (TSFC) and engine efficiency was investigated and then in the exergy analysis, it was found that the lowest exergy efficiency with a value of 85.45% belongs to the combustion chamber; Therefore, a parametric study was conducted to improve the performance and exergy efficiency of the burner; For example, in the case of bypass ratio of 2.2 and fan pressure ratio of 2, the exergy efficiency of the burner is increased by 12.23% compared to the base case. In addition, the results of sensitivity analysis show that the burner exit temperature and the HPC pressure ratio with 21.81 and 2.2%, respectively, have the most and the least effect on the engine net thrust; Also, the burner exit temperature and the flight altitude with 4.57% and 0.11%, respectively, have the most and the least effect on the TSFC.

Inertial navigation amplifies the noise of the input sensors over time due to the presence of an integrator in the output path to determine the position and attitude of the object. This system has high bandwidth and good short-term accuracy. On the other hand, GPS navigation has low bandwidth, low noise processing power, and long-term accuracy. However, it can only determine the position and does not give us information about the object's attitude. Most papers have presented integrated algorithms related to GPS/INS tightly coupled navigation and have provided relatively acceptable results. Nevertheless, the main problem in this integration model is when there is an intentional or stochastical signal interference for GPS, which is not far from the mind in military applications. Therefore, navigation faces a problem. This article provides a solution with a tightly coupled integrated algorithm for high accuracy in integrated navigation.

In present research, the interaction between single liquid droplet with particles inside a porous media is investigated numerically in two dimensions. The He’s model is used to simulate two phase flow and multiple relaxation time collision operator is implemented to increase numerical stability. Simulations have performed in three non-dimensional body forces of 0.000108, 0.000144, 0.000180, porosity values of 0.75, 0.8, 0.85 and Ohnesorge range of 0.19-0.76. In the range of investigated non-dimensional parameters, two distinct physics of droplet trapping and break up have observed. The related results revels that for every values of investigated non-dimensional body forces and porosity, there is a critical Ohnesorge number that droplet breaks up occurs for larger values. This critical value decreases as non-dimensional body force and porosity increases. Based on these results, a droplet trapping or break up behavioral diagram is drown with respect to the investigated density ratio, Ohnsorge, Reynolds and Capilary numbers.

This paper provides an academic insight into the design of a three-dimensional guidance law which can be utilized to reach the maneuvering targets in definite angles. Firstly, the theoretical phenomenon of a conventional dynamic inversion which can be implemented for reaching targets with constant velocity will be addressed. However, given that this method is not applicable for reaching accelerated targets, a combination of dynamic inversion method and sliding mode control is presented. These mechanisms can impact maneuvering targets with bounded acceleration. Proceeding the discussion of these observations, an improved form of the proposed controller will be introduced as this method guarantees a finite reaching time. Furthermore, the chattering phenomenon, which is the predominant disadvantage of the sliding mode, will be analysed. Given these findings, a second terminal sliding surface will be presented. This approach will be able to generate continuous guidance law whilst effectively eliminating the chattering problem that was evident in the sliding mode mechanism. Finally, through the application of numerical simulations, the effectiveness of the proposed guidance laws against maneuvering targets will be demonstrated.

In this paper, the control of a three-axis rigid satellite attitude control system with a fractional order proportional-integral-derivative (PID) controller is investigated in the presence of disturbance and parametric uncertainties. The reaction wheel actuator with the first-order dynamic model is used to control the attitude of the satellite. Uncertainties are considered on satellite moment inertia, actuator model and amplitude and frequency of external disturbances. External disturbances are modeled with two fixed and periodic parts and uncertainty is also considered on the disturbances model. The integer order controller is also used for the same conditions to compare the results with the fractional order controller. The usual Granwald-Letinkov definition is used to solve integrals and fractional order derivatives. The mean absolute of the pointing error of the satellite pointing maneuver has been selected as an objective function of the optimization problem. The controller gains in integer and fractional order are obtained by particle swarm evolution algorithm (PSO) optimization method. The performance criterion has been studied in terms of the controller time response and also in terms of the standard deviation of the mentioned uncertainties and external disturbance. The results show that the fractional order controller performs more accurate and robustness than the integer order controllers in the face of uncertainty and disturbance.

In this research, combustion modeling inside the combustion chamber of a typical turboprop engine has been investigated. The complex geometry of this combustion liner was modeled according to the technical drawings and the turbulent flow and internal combustion were simulated numerically and three-dimensionally. The non-premixed combustion model is used to simulate combustion and the K-ω method is used to simulate turbulent flow. This study investigated how the combustion phenomenon occurs, the internal temperature distribution, the outlet, and the wall of the combustion tube, for which comprehensive three-dimensional data were not previously available. These simulations have identified the weaknesses of the combustion tube and by eliminating these weaknesses, the problem of reducing the efficiency of several gas turbine engines has been solved. Comparison of the results of the present study with a similar numerical analysis showed that the results of this study are more in line with laboratory results. The results of the simulation of combustion pipe defects show that the combustion liner that had a welding line near the outlet had a 25% higher pressure drop than a typical combustion liner and the effective cross-sectional area of ​​the fluid flow was reduced by 11%. The output of a repaired combustion tube is different from a typical type.

In this paper, the buckling behavior of functionally graded simply supported nanocomposite beams reinforced by nano clay is studied. The specimens were prepared and the experimental tensile and buckling tests are carried out. The elastic modulus of epoxy/clay nanocomposite for functionally graded and uniformly distributed of nanoclay are estimated through a model based on the genetic algorithm approach. The results show that GA can be considered as an acceptable optimization research technique to identify Young’s modulus of nanocomposites with maximum accuracy. For simply supported beam, the first order shear deformation beam theory is applied for displacement field and the governing equations are derived by using Hamilton principle. The influence of nanoparticles for functionally graded and uniform distribution on the buckling load of a beam is presented. Comparison study is conducted to assess efficacy and accuracy of the present analysis. A comparison for theoretical analysis with the experimental results demonstrated the high accuracy.

In multi-stage Missiles, stabilizer wings are responsible for stabilizing the Missile. The control fins located upstream of the stabilizer wings affect the flow by spinning, which influences stability as well as control. One method for resolving this problem is to design stabilizer wings with less affectability against the upstream flow. The present paper deals with this issue by considering multiple planar fins and grid fins. Once validation is performed, after selecting the appropriate turbulence model and choosing the planar and grid fins, the appropriate Missile model is established; then, on a model with speeds of 0.6, 0.7, and 0.8 Mach, at attack angles of 0, 2, 4, and 6 degrees, and with control fins, variation at angles of 0, 1, 3, and 6 degrees, the aerodynamic coefficients as well as the effects of the upstream stabilizer wings are investigated in pitch and roll modes at an appropriate trim angle . The obtained results indicated that the use of grid fin downstream of the control surfaces would be less affected due to its physical nature; thus, the lower capacity of the control surface would be used for control during the flight, which would significantly facilitate the process of designing.

The use of urban and rural scale wind turbines that in addition to generating power can play the role of old wind turbines in arid areas will be very attractive. In this research it has been tried to first evaluate the wind energy potential in Zahedan city and then to evaluate a sample of vertical axis wind turbine. First, a three-dimensional semi-analytic code based on the DMST method was developed, the validation of which was studied and presented. Using this tool, the performance of the turbine in terms of power and ventilation has been investigated and in the results of this parametric study, the effect of the cone angle on the power and ventilation coefficient has been explained in detail. Based on the results of this study, it can be seen that increasing the cone angle to 20 degrees, although it reduces the power of the turbine, but does not have a significant effect on the power coefficient and at the same time causes a ventilation coefficient of about 1.6 percent. It was also observed that at a conical angle of 10 degrees and at the working point of the turbine, the output power will be 30 kW and the ventilation flow will be 30,000 m^3⁄h.