Ionică Cîrciu

ASPECTS REGARDING VELOCITY DISTRIBUTION IN THE SECONDARY ZONE OF A GAS TURBINE COMBUSTOR

This paper deals with the modelling and simulation of the combustion in a turbojet engine in order to find the velocity distribution in the secondary zone of the flame tube. The Arrhenius relationship, which describes the basic dependencies of the reaction rate on pressure, temperature and concentration, has been used. Also, combustion efficiency has been defined and related to both the exhaust temperature and species concentration. Premixed laminar flames and the dependence of propagation rate on temperature and the fuel-air ratio have been highlighted. The main focus of this paper consists in a new configuration of the aircraft engine combustion chamber with an optimal distribution of gas velocity in front of the turbine. This constructive solution could allow a lower engine rotational speed, a lower temperature in front of the first stage of the turbine and the possibility to increase the turbine pressure ratio. Also, a higher thermodynamic cycle efficiency and thrust in comparison to traditional constant-pressure combustion gas turbine engines could be obtained.

Morphing Wing Concept for Small UAV

The biological flight involves the movement of a wing (lift surface) in viscous medium and it generates lift and resistance for going forward through friction compared to Reynolds number. The morphing concept is generally based on optimizing the aerodynamic form during the mission so it can execute a maneuver flight. This article desires a short passage through the mathematical aspect in 2D of the morphing profile concept.

Aircraft engine mathematical model – linear system approach

This paper examines a simplified mathematical model of the aircraft engine, based on the theory of linear and nonlinear systems. The dynamics of the engine was represented by a linear, time variant model, near a nominal operating point within a finite time interval. The linearized equations were expressed in a matrix form, suitable for the incorporation in the MAPLE program solver. The behavior of the engine was included in terms of variation of the rotational speed following a deflection of the throttle. The engine inlet parameters can cover a wide range of altitude and Mach numbers.

Aspects Regarding the Performances of Small Swept Flying Wings Mini UAV-s in Aggressive Maneuvers

The UAS are largely used both in civilian and operational theatre missions. The current paper shows an examples for the turning and the spiral as simple maneuvers are also relevant to the development of new tactical capabilities of small UAS through improving the performance itself.

RECOVERY SYSTEM OF THE MULTI-HELICOPTER UAV

The developments of UAS over the last decades have imposed approaches regarding the recover and rescue segment for aerial vectors. Operational and research requirements for UAV impose the use of recover systems due to the nature of the missions. The main purpose of the paper is to offer a global image regarding the recover and salvation systems used of the UAVs. Keyworks: Unmanned aerial vehicles/sistems (UAV/UAS), recover system, multi-helicopter, paragliding

The Limits of Downsizing - A Critical Analysis of the Limits of the Agile Flying Wing MiniUAV

The missions of small flying wing UAVs require maneuver capabilities as well as optimal flight performance to balance the low operating and manufacturing costs. The basic principles in designing aviation structures must be readjusted due to the innovative concepts regarding the use of advanced materials as well as to the perspectives of using alternative energy aboard UAVs. The current paper is a synthesis of the 2D and 3D aerodynamic analysis of small swept flying wing UAVs that offers a global image of the possibilities of a multidimension optimization (miniaturization-scalability, payload-flexibility, minimum performances requirements).

MATHEMATICAL MODEL AND CFD ANALYSIS OF PARTIALLY PREMIXED COMBUSTION IN A TURBOJET

In this paper are presented some results about the study of combustion chamber geometric configurations that are found in aircraft gas turbine engines. The CFD simulations were made with jet A fuel (which is presented in the Fluent software database) for an annular flame tube with 24 injectors. The temperature profile at the turbine inlet exhibits nonuniformity due to the number of fuel injectors used in the circumferential direction, the spatial nonuniformity in dilution air cooling and mixing characteristics as well as other secondary flow patterns and instabilities that are set up in the flame tube. The results show that a spiral (helicoidal) holes distribution could improve the flame tube efficiency, turbulent vortex influence and the actual rate of heat release.

Concerted Systems for Increasing the Survivability of the Aircraft against Terrorist Threats

The paper explores the threat posed by terrorism in aviation domain, especially surface-to-air missile attacks against transport aircraft. While the focus of this paper is the mitigation of security risks in the aviation domain, the proposed solution based on concerted countermeasure systems discussed here may be developed in the context of homeland security policy promoting the principle of flight safety. The reception and the processing of data through the detection of signals emitted by various sources are proceeding in the absence of users interest about the form of the wave of the message. The detection of the presence / absence of the signal or the identification of its value is proceed by identifying the signal associated to each value of the message, considered a discrete variable, hence triggering of the adequate defence mechanism.

SIMPLIFIED MATHEMATICAL MODEL FOR AIRCRAFTSRESPONSE CHARACTERISTICS

Human performance modeling provides a complementary technique to develop systems and procedures that are tailored to the pilots tasks, capabilities, limitations and also, offers a powerful technique to examine human interactions across a range of possible operating conditions. From an initial review of past efforts in cognitive modeling, it was recognized that no single modeling architecture or framework had the scope to address the full range of interacting and competing factors driving human actions in dynamic and complex environments. The paper presents two mathematical compensatory models, based on the aircraft dynamics characteristics and frequency responses.

Some aspects regarding unsteady fluid flow with time dependent boundary conditions

This study explores the dynamic characteristics of the unsteady fluid flow around an airfoil where the time dependency is introduced through the boundary conditions. The models of the vortex wake’s shape and strength were based on the time dependency history of the motion and the methods of solution that were developed for these models included the treatment of the zero normal flow on a solid surface. A numerical investigation has been performed using Maplesoft environment. As a result of the nonuniform motion, the path along which the airfoil moves was assumed to be prescribed. In the paper the wake shed from the trailing edge of the lifting surfaces was modeled by vortex distribution.