No abstract

Processes resulting in average power limitations in high-repetition-rate pulsed lasers are studied. The description and performance of a CO(2) laser with an average power up to 10 kW as well as of an optically pumped CF(4) laser are given.

ДУ «Інститут нейрохірургії імені акад. А.П. Ромоданова НАМН України», м. Київ *Conflict of Interest Statement (We declare that we have no conflict of interest). *Заява про конфлікт інтересів (Ми заявляємо, що у нас немає ніякого конфлікту інтересів). *Заявление о конфликте интересов (Мы заявляем, что у нас нет никакого конфликта интересов). *No human/animal subjects policy requirements or funding disclosures. *Жодний із об'єктів дослідження (людина/тварина) не підпадає під вимоги політики щодо розкриття інформації фінансування. *Ни один из объектов исследования не подпадает под политику раскрытия информации финансирования.

No abstract

Durability and reliability are the most important parameters of gas turbine engines combustion chamber. Combustion chamber flame tube walls are the most temperature-loaded engine components. Therefore, eliminating wall burnout is an key issue as well as keeping temperature of combustion chamber elements within the materials operating temperature range. Thus, there is a need to define thermal state of these elements. Currently, the problem of flame tube wall burnout is exacerbated by trends of increasing the compressor pressure ratio and temperature before the turbine. It is important to resolve this problem during the gas turbine engine design phase. This will reduce time and material costs for launch of their serial production. CFD is one way of resolving this problem. The numerical method of simulating thermal state of flame tube walls was applied and tested. This method takes into account a thermal barrier coating and a cooling system. Three-dimensional geometric model consists of the flow area and the flame tube walls with multi-layer thermal barrier coating. Flow area is needed to simulate fluid dynamic processes. Flame tube walls geometry was created for heat transfer simulation. Mathematical model of the workflow in the combustion chamber had been created previously and was validated. The study is carried out by numerical methods, using the commercial software Ansys. Temperature distribution on the combustion chamber flame tube walls was obtained by the simulation. It agrees well with the results of the experiments. The maximum temperature of the walls was reduced from 1400 K to 1100 K through the reallocation of holes area between the cooling system belts. This ensures the operability of the wall material. Then, the simulations of the flame tube walls deformation were conducted. As a result, the deformations and stresses, that occurred due to the walls heating, were evaluated using the one-way Fluid-Structure-Interaction (FSI) module. The maximum displacement along the axis of the combustion chamber was less than 2 mm, when the acceptable move in telescopic connection is 6 mm. It was found that the outer flame tube wall exposed the highest heat load. The area of the outer annular channel decreased by 18% and the area of the internal annular channel increased by 7%. Air distribution of the cooling system was changed due to walls deformation and velocity changes in annular channels, therefore the additional simulations and some modification in the design are required. The methodology created on the base of this study can be used for the simulation of the various combustion chamber designs.