Aircraft Icing Severity Evaluation

Aircraft icing refers to the ice buildup on the surface of an aircraft flying in icing conditions. The ice accretion on the aircraft alters the original aerodynamic configuration and degrades the aerodynamic performances and may lead to unsafe flight conditions. Evaluating the flow structure, icing mechanism and consequences is of great importance to the development of an anti/deicing technique. Studies have shown computational fluid dynamics (CFD) and machine learning (ML) to be effective in predicting the ice shape and icing severity under different flight conditions. CFD solves a set of partial differential equations to obtain the air flow fields, water droplets trajectories and ice shape. ML is a branch of artificial intelligence and, based on the data, the self-improved computer algorithms can be effective in finding the nonlinear mapping relationship between the input flight conditions and the output aircraft icing severity features.

Determining the Aerodynamic Characteristics of a Propeller-Driven Anti-UAV Fighter While Designing Air Propellers

Given the rising importance of unmanned aerial vehicles (UAVs), this article addresses the urgent scientific problem of determining the aerodynamic characteristics of a UAV while laying out the propellers for the wings. We discuss the methodology for experimental wind-tunnel studies of aircraft configurations with propellers. It is shown that a characteristic feature of the configuration small-elongation wing with propellers is the absence of elements that are not affected by propellers. This feature makes it difficult to implement and automate a wind tunnel experiment, since there are problems with providing similar criteria for a working propeller; it is difficult to achieve perfect balancing for solid drive propellers, which causes vibration, the level of which depends on uncontrolled factors; the inability to neglect the presence of the body elements influence to the blades of propellers; the difficulty of direct measuring propeller thrust and torque. The presented methodology involves the integrated usage of experimental and numerical methods to eliminate the difficulties in conducting physical experiments in a wind tunnel. This approach makes it possible to combine the high credibility of experimental data in the study of the physical essence of phenomena with high efficiency and accuracy in determining aerodynamic characteristics by numerical methods. Using this approach, we established dependences of the aerodynamic characteristics of the small-elongation wing configuration with counter-rotating propellers on the geometric and kinematic parameters of the configuration for other extensions and constrictions of the wings. These data can serve as the basis for the development of recommendations for the selection of sensible geometric parameters of the aerodynamic configuration of a small-elongation wing with counter-rotating propellers.

Modern parachute precision aerial delivery systems

The development of parachute precision aerial delivery systems (PADS) has been going on since 1940s. Relying on the analysis of the aerodynamic characteristics of various gliding parachutes, the paper specifies the aerodynamic configuration for modern parachute precision aerial delivery systems, determines the types and considers the possibility of unifying the design of the main parachutes of such systems. The paper describes the history of gliding parachutes, summarizes the experience of developing such parachutes, and considers the evolution of maneuverable and steerable parachutes. In our study, we introduce and substantiate a new for the Russian practice classification of parachutes with aerodynamic quality. First, aerodynamic characteristics of various gliding parachutes were generalized and the main requirements for parachute PADS were indicated. Then, modern combined parachute PADS of Airbone Systems, USA, developed on the basis of double-surface parafoil parachutes were analyzed and classified with the emphasis on the types of modern systems. Since unification is most responsible for reducing the cost of industrial production of any technical systems, we considered the issues of possible unification of parachute PADS. Findings of research show that the unification of modern combined PADS depends on the common elements of control systems. It is worth noting that unification for systems of the ultralight class in terms of main parachutes is possible when using individual parachutes. For parachute systems of the middle and heavy class, intraspecific unification is possible through the use of single parachute modules.

Adaptive attitude control and the modeling of hypersonic vehicles with mismatched disturbances

Hypersonic vehicles often use the aerodynamic configuration and light materials such as lifting body and waverider, which leads to the unmatched uncertain control problems caused by strong coupling characteristics and interference during reentry. To solve these problems, firstly, this paper analyzes the key factors and uncertainties that affect the attitude motion of hypersonic vehicle. Secondly, it studies the modeling and verification of rigid body and elastic body of hypersonic vehicle, establishes the error model with disturbance observation compensation, and proposes a new attitude control scheme of hypersonic vehicle, which realizes the stable tracking of attitude angle and improves the uncertainty of key parameters of the system. The simulation results show that the performance index meets the requirements and has good robust performance in the presence of unknown disturbance.

Influence of Splitter Blades on the Performance of a Single-Stage Centrifugal Compressor With Pressure Ratio 12.0

High performance centrifugal compressors with high pressure ratio are highly applied in turboshaft engines in order to obtain higher power-to-weight ratio and lower fuel consumption. The optimization of the aerodynamic configuration design of splitter blades is one of the effective ways to achieve higher efficiency. An in-house designed single-stage centrifugal compressor with a pressure ratio up to 12.0 is studied in this paper. By using a three-dimensional CFD (computational fluid dynamic) method, this paper investigates influences of the number of splitter blades and their leading edge position on the flow field characteristics and aerodynamic performance of the centrifugal compressor with ultra-high pressure ratio. Results show that three critical flow characteristics lead to severe losses in centrifugal compressor impeller when only full blades are applied. Those flow characteristics include the strong shock wave, the severe tip clearance flow at the inlet region and the severe flow separation at the rear region. Therefore, the inlet blade number should be reduced to decrease the loss caused by strong shock waves and tip clearance flow, while the outlet blade number should be sufficient enough to suppress flow separation. By optimizing the number and the leading edge position of splitters, the performance can be improved under the reduction of combined losses caused by shock waves, tip clearance flow and flow separation. When an aerodynamic configuration with single-splitters is used, numerical results indicate that the leading edge position of splitter blades should be located at 60% of the main blade chord length, and the centrifugal impeller isentropic efficiency with ultra-high pressure ratio can be increased from 82.4% (the aerodynamic configuration with only full blades) to 89.5%; when an aerodynamic configuration with double-splitters is used, the leading edge positions of middle and short splitter blades should be respectively located at 40% and 60% of the main blade chord length, and the impeller isentropic efficiency can be further improved to 90.9%.

МОДЕЛИРОВАНИЕ ИЗМЕНЕНИЙ В ГЕОМЕТРИИ КРЫЛА ПРИ ИХ СОГЛАСОВАНИИ С ПАРАМЕТРАМИ СИЛОВОЙ УСТАНОВКИ

Development modifications of aircraft have become the main direction of development of transport category airplanes, including military transport (МTА). However, there are several ways to solve such tasks:– to leave the same area and other geometric parameters of the wing and the problem are solved by significant changes in the power plant;– change the wing area and the aerodynamic configuration with the same parameters of the power plant.Both these ways have their advantages, but their implementation raises a number of problematic issues:- excessive growth of the starting mass modification;- the deterioration of its takeoff and landing characteristics;- deterioration in fuel efficiency and other technical and economic indicators, which leads to a decrease in the competitiveness of the modification.The most effective is getting the new aircraft when an agreement is called, changes are already in the preliminary design phase of the modification.The article formed the scheme of approval of such changes, with the essential growth of the load capacity, range, and improved fuel efficiency of the designed modifications. A distinctive feature of the proposed scheme is that modification changes the geometry of the wing reduces the magnitude of its inductive reactance at a predetermined lifting force.A model of the influence of design changes in the geometry of the wing, such as the narrowing and the corners of the geometric twist of the local chord along the span, expressed via the coefficients of the ellipticity of the trapezoidal wing, to change the polars of the wing and its aerodynamic quality.Developed a step-by-step evaluation of the aerodynamic performance of the required values of the coefficients and , the magnitude of which is stipulated by the conditions of approval modifications to the wing and thrust characteristics of the power plant. This is an area , in which a possible implementation of the required increase in capacity modifications.The obtained results related to the modeling of changes in the geometry of the wing are an integral part of the scheme approval deep modifications in the wing and the power plant is required when creating modifications with enhanced performance.