Analytical and numerical study of propulsion vector orientation by non-aligned fluid method

Dissertation for Master Degree in Mechanical Engineering

Energy Conversion

Abstract:

Fluid propulsion vector orientation has emerged as an important technology for high performance air vehicles. This technology can improve the maneuverability of the aircraft by changing the nozzle flow and its deviation from its axial direction. The purpose of this study is to investigate the effects of the secondary suction flow in the main output flow of a small jet engine that is integrated with a cylindrical duct and a diverging horn, as well as to investigate the effect of fluid and geometric parameters and to evaluate the performance of the fluid propulsion vector orientation. Numerical and analytical studies of the orientation of the propulsion vector were performed for the first time in the form of non-aligned flow on this nozzle, and then a series of researches and investigations were carried out in the direction of geometric optimization with the help of numerical analysis. Numerical calculations for different flow conditions with and without secondary flow suction and at different heights of the secondary gap and different curvature radii of Kevlar [1] have been investigated. Numerical simulation of the nozzle flow has been performed by solving the Navier-Stokes equations, and the input parameters have been adjusted to better match the experimental conditions. These studies have been investigated in the primary mass flow rate and different suction pressures for three secondary gap heights of 1, 1.5 and 2 mm and three Kevlar curvature radii of 106, 120 and 300 mm and the arc cutting angle of 42 degrees. The effect of these fluidic and geometrical parameters on the orientation of the propulsion vector and the performance of the nozzle have been discussed, and the results show that these parameters have a direct effect on the performance of the orientation and control of the propulsion vector. In analytical studies, two new methods have been developed in order to better analyze this phenomenon in Shipoureh. In the first method, by considering a control volume and in accordance with the laws of linear momentum and a series of assumptions, simplified relationships have been developed, and in the second method, the analysis of this phenomenon has been realized using the equations of flow movement on wavy or sinusoidal walls.

Keywords: propulsion force direction, non-aligned flow, Quanda surface, wavy wall, computational fluid dynamics

1-1- Research goals and motivations

The high performance of flying objects requires innovative specialized developments in the design of their power units. Propulsion vector orientation[1] is emerging as a key and promising technology for existing and future flying objects. This technology is aimed at spreading knowledge and information about the response of exhaust gases from turbine engines. Thrust vectoring nozzles are effective under all flight conditions, and they can meet design constraints such as low cost, low noise, light weight, short take-off distance, and improved radar evasion characteristics. Thrust vectoring is done by two known methods, which are mechanically oriented method[2] and fluid oriented method[3]. accepts In the mechanical direction method, mechanical parts are used to divert the outgoing gases. This not only increases the weight and complexity of the system, but also increases the costs, repairs and maintenance required. These factors motivated researchers to research new methods to achieve the same capabilities of vector orientation of the driving force but without using moving parts. Orientation of the propulsion vector through fluid was proposed as an alternative method to mechanical methods. This method uses a secondary jet flow to divert the flow path of the main exhaust gases. Potentially, the fluidic thrust vector control nozzle not only provides effective flow deflection but also eliminates the problems associated with additional mechanical parts. The technology of directing the propulsion vector through fluid has not been implemented yet. This point indicates that it is still necessary to carry out more research and progress on its effects and the variety of its applications.

In the present study, obtaining the highest efficiency and the highest directionality of the propulsion force vector with the least amount of energy is the first goal of this research.Examining effective and efficient geometrical parameters and primary and secondary flow parameters on nozzle performance can help to know this method more accurately. Also, one of the other goals of this research is to perform an analytical solution and validate the results of numerical simulations.

1-2- Introduction of propulsion vector control and the advancements of this technology

Propulsion vector direction technology can improve the maneuverability of flying objects by controlling the outflow from the nozzle and diverting it from its longitudinal axis. In addition, this technology offers many advantages for modern flying objects. Directional thrust vector nozzles can control flying objects at high angles of attack from the stall zone, while this efficiency and ability is lost in conventional aerodynamic flights [1]. Since thrust vector control nozzles may effectively generate yaw [4] and yaw [5] forces or torques with relatively low drag, these nozzles can be enhanced and even possibly a suitable alternative to aerodynamic controllers [2]. In flights that use thrust vector control nozzles instead of traditional nozzles, the need to use vertical and horizontal tails can be reduced or even eliminated [1]. One of the advantages of separating the rear tail of the aircraft can be mentioned is the reduction in weight and even their radar evasion compared to their conventional models. In addition, maintenance costs related to the tail of the aircraft are also reduced. Flying objects that are integrated with such nozzles can use less propulsion power to achieve the desired results such as maneuvering, patrolling, climbing and descending, and since the need for propulsion power is less, these flying objects can consume less fuel by achieving a greater flight range. Strengthen for short sitting and rising [3]. By using these nozzles and turbofan engines, flying objects can deviate the propulsion force vector even up to 90 degrees and provide the possibility of vertical landing and takeoff. With the possibility of landing and taking off in small areas, flying objects can perform well in smaller environments such as aircraft carriers and even damaged airports [4]. Propulsion vector direction technology has become a popular and promising technology due to its efficiency and more useful and effective performance in new flying objects.

1-2-1- Limitations of traditional control systems

A basic issue regarding the performance of any flying object is maneuverability, the ability to create and produce a change in its trajectory, position, speed and acceleration. A maneuver is the aircraft's response to a control input by the pilot and is typically performed using aerodynamic control surfaces. These surfaces include the moving parts of the airplane wing such as aileron [6], rudder [7], elevator [8] and canard [9] [5]. Control surfaces are located in specific parts of the bird's body, including the wings and tail. The deviation of these surfaces changes the external shape of the device at the critical points of the structure, and leads to a change and imbalance in the aerodynamic forces acting on the device, and this action leads to a rotation around the center of gravity, which is called maneuvering. But these conventional aerodynamic control systems are limited by constraints, because control is lost in situations where aerodynamic forces are small, such as low-speed stalls or high angles of attack. Normally, an airplane during a maneuver takes advantage of the deviation of the control surfaces in order to correct its external shape. Due to the aerodynamic limitations, this deviation is very small for a passenger plane and up to 80% of its range for a fighter plane.

An aerodynamic force for a given surface is proportional to the square of the speed. Therefore, only above a certain threshold of speed will deviation from a control level become effective. According to the angle of attack, the aerodynamic forces increase only up to a maximum value as this angle increases, and then when the angle of attack exceeds the maximum value, it causes the flow to separate and the appearance of aerodynamic drag.