VIBRATION PROTECTION SYSTEM WITH AN ELASTIC INTERFERENCE RING CONSTRUCTIVE SOLUTIONS AND THEIR TESTING

The article considers a vibration protection system with an elastic intermittent link. A constructive solution is presented in the form of a mechanical oscillator simulating the process of operation of the considered vibration protection system. The results of experimental studies of the operation of a mechanical oscillator are presented. Conclusions have been drawn on the prospects of using a vibration protection system with an intermittent elastic link.

THE PARACHUTE SYSTEM WITH THE ELASTIC LINK AND THE LOAD DIVIDED INTO TWO PARTS AS A TANDEM

The article suggests a new type of the parachute system (PS). Its distinctive feature is the presence of an elastic link (EL) for attaching the cargo to the parachute, and the cargo itself is divided into two parts, m1 and m2, comparable in weight and suspended one under the other. The cargo is connected by a cable through the cable length control mechanism. PS in flight consists of a parachute, stretched EL, cargo m1, the cable length control mechanism, cable, cargo m2. The main feature of this type of PS is the ability to provide low dynamic overloads of m1 cargo during the entire flight, including landing. For a soft landing of m1 cargo, it is necessary to choose the main parameters of the PS correctly: the parachute area, the EL stiffness, the weight of m1 and m2 cargo, the length of the cable. To confirm the efficiency and feasibility of the proposed concept, an experimental PS with a flight mass of m ≈ 10 kg was designed, prepared and tested. The parachute is made of zero porosity fabric, its area is S = 2.2 m2 It has a cylindrical skirt that is used to give stability to the PS in flight. As an EL a silicone tube is used with the length of l0 = 6 m when unstretched, but in flight under the weight of cargo ml and m2 it is stretched to l0 + Δl ≈ 17 m. The mass of the cargo ml is m1 - 5.5 kg, m2 cargo has a mass of m2 ≈ 4.5 kg. To raise the PS a two-seat hang-glider was used. The drop occurred from the height of H ≈ 200 m. The rate of decent before landing was Ve = 8...9 m/s. The analysis of the final records of dynamic overloads shows that during the entire flight, including landing, the total cargo overload ml did not exceed n = 5. Thereby operability, feasibility and the declared properties of the offered type of PS are confirmed.

Whole Engine Interaction in a Bladed Rotor-to-Stator Contact

Reducing the clearances between rotating and fixed parts is an important factor in increasing the performances of turbomachines. The physical counterpart however is an evolution in possible rotor-stator contacts capable of causing unstable dynamic behavior. A proper prediction of the rotor-stator contact occurrences and associated induced phenomena, has therefore become of a great interest for aero-engine mechanical engineers. Most numerical simulations involving rotor-stator contact can be divided into two types of physical behavior. The first focuses on contact induced blade/casing interactions, in only taking into account the blades and casing flexibility. The second type of behavior takes into account the shaft dynamic while neglecting blade flexibility. Future designs of aircraft engines will however raise the need to combine these two types of models. Since, the structural components are more flexible, the dynamic coupling between engine modules is increased. This paper proposes a study based on a structure representative of the whole aircraft engine, including the contacts that may arise between the fan-blade tips and fan casing. We have introduced a fully-coupled phenomenological model with flexible blades, shaft and casing. Furthermore, this model includes an elastic link between shaft and casing to simulate the fan frame behavior. We begin by explaining the linear results, which highlight the dynamic couplings between these various model components. During a second step, this paper presents the nonlinear results obtained by introducing a contact law. These results demonstrate the influence of the whole engine dynamic on contact-related behavior with special focus on the system dynamic stability.