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1
Content available remote Investigation on performance of a cryosurgical probe in various feeding and environmental conditions
Mezyk L., Kobiera A., Karlinski G., Brojek W.
Journal of Power Technologies
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2018
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Vol. 98, nr 1
89--96
EN
Cryosurgery is a procedure in which diseased tissue is destroyed by freezing. During a strictly controlled process, low temperature is used to separate diseased from healthy tissue with minimal bleeding. It is an effective method that has been applied in many areas of medicine for a number of years, especially in dermatology, oncology, laryngology, gynecology, vascular surgery and ophthalmology. There are many technical solutions different probes for applying low temperature to tissue. The detailed construction of the probes are trade secrets and will not be discussed here. In the paper the authors present the results of research on a chosen type of cryosurgical probe for various conditions: feeding gases, flow rates and external conditions. The results are illustrated in the form of graphs showing the temperature of the tip of the probes in changing conditions.
2
Content available Resistojet thruster with a power system based on supercapacitors
Mezyk L., Kobiera A., Boruc L., Biczel P., Wolanski P.
Challenges of Modern Technology
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2014
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Vol. 5, no. 3
13--21
EN
This paper presents research into a resistojet model that can be powered by supercapacitors for satellite propulsion applications. The performance of the system, calculated including a preliminary study of mass and power budget, shows that this solution has potential for a certain range of space missions. The main problem when designing a pulsed resistojet is the compromise between the thermal capacity of the resistojet and the heat transfer efficiency of the device. When the heater is used in pulsed mode, it should have low mass and thermal capacity in order to reduce the energy required to heat the devices. On the other hand, the main technical restriction in resistojet thrusters is heat transfer due to the laminar regime of the flow in the heater. The heat transfer area should be as large as possible, but the mass of the device limits any such increase in area. In this research several design options were considered in an attempt to find the optimal solution. After research on the oscillating element and porous heater, capillary tubes directly heated by the current were determined to be the most effective solution. A power supply based on supercapacitors was constructed. It consists of 30 supercapacitors of 300 F each, connected to deliver 70 V of voltage, 10F of total capacitance and maximum peak power of 5 kW. Research for three different gases – ammonia, propane and butane – was conducted and the results are presented in this paper.
3
Content available Three - dimensional numerical simulations of the combustion chamber of the rotating detonation engine
Folusiak M., Swiderski K., Kobiera A., Lukasik B., Wolanski P.
Journal of KONES
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2013
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Vol. 20, No. 1
83--88
EN
From 2010 Warsaw University of Technology (WUT) and Institute of Aviation (IoA) jointly implement the project under the Innovative Economy Operational Programme entitled ‘Turbine engine with detonation combustion chamber’. The goal of the project is to replace the combustion chamber of turboshaft engine GTD-350 with an annular detonation chamber. During the project, the numerical group that aims to develop computer code allowing researchers to simulate investigated processes has been established. Simulations provide wide range of parameters that are hardly available from experimental results and enable better understanding of investigated processes. Simulations may be also considered as a cheap alternative for experiments, especially when testing geometrical optimizations. In this paper the analysis of simulation results of the combustion chamber of the Rotating Detonation Engine (RDE) investigated at the IoA in Warsaw is presented. Primarily, REFLOPS USG which has become a fundamental numerical tool in the research of the RDE at the IoA is briefly described and governing equations and numerical methods used are shortly presented. Some aspects of numerical simulations of the RDE, related to selection of combustion mechanism, and an initiation of rotating detonation are provided. Secondly, results of simulations of inviscid gas with numerical injectors of hydrogen are compared with available experimental results. Three different wave patterns are identified in numerical solution and briefly described. Results of simulations are compared to experimental results in combustion chamber. Results presented in this paper are part of the project UDA-POIG.01.03.01-14-071 ‘Turbine engine with detonation combustion chamber’ supported by EU and Ministry of Regional Development, Poland.
4
Content available Numerical tools for three dimensional simulations of the rotating detonation engine in complex geometries
Swiderski K., Folusiak M., Kobiera A., Lukasik B., Wolanski P.
Journal of KONES
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2013
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Vol. 20, No. 1
329--336
EN
This paper describes the development of a computational code REFLOPS USG (REactive FLOw solver for Propulsion Systems on UnStructured Grids) based on the Favre averaged Navier-Stokes equations with chemical reactions for semi-ideal multicomponent gas to predict the structure and dynamics of three-dimensional unsteady detonation as it occurs in the Rotating Detonation Engine (RDE). This work provides an overview of second order accurate in time and space finite volume method applied to conservation equations and its implementation on unstructured self-adaptive tetrahedral or hexahedral three-dimensional cell-centred meshes. The inviscid fluxes are given by the Riemann solver and stabilization is ensured by the proper limiters inherited from the TVD theory or gradient based limiters. The stiff equations of chemical kinetics are solved by use of implicit DVODE (Double precision Variablecoefficient Ordinary Differential Equation solver, with fixed-leading-coefficient implementation) routine or by explicit Chemeq2 routine. Additional improvements are incorporated into the code such as parallelization in OpenMP and implementation of NVIDIA CUDA technology. REFLOPS USG has become a fundamental numerical tool in the research of RDE at the Institute of Aviation in Warsaw, in frame of Innovative Economy project UDA-POIG.01.03.01-14-071 ‘Turbine engine with detonation combustion chamber’ supported by EU and Ministry of Regional Development, Poland. The simulations presented in this paper are based on inviscid or viscous multicomponent semi-ideal gas flow with chemical reactions. Due to high computational costs only simple chemical reaction mechanisms are used here.
5
Content available Analiza wymiany ciepła oscylującej płytki w ośrodku amoniaku jako nowej koncepcji wymiennika ciepła w elektrycznych silnikach rakietowych
Florczuk W., Kobiera A.
Prace Instytutu Lotnictwa
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2011
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Nr 12 (221)
89-101
PL
Elektrotermiczny napęd rakietowy ze względu na prostotę swego działania i konstrukcji jest atrakcyjnym rozwiązaniem dla inżynierów projektujących systemy kontroli położenia satelitów. Ciagłe poszukiwanie nowych rozwiązań oraz stosowanie nowych materiałów konstrukcyjnych znacząco podniosły sprawność obecnych silników rakietowych, w tym elektryczno-termicznych typu "Resistojet" . Nowym rozwiązaniem proponowanym w tego typu napędach jest wymiennik ciepła z oscylującym elementern grzewczym. Dzięki temu termiczna warstwa przyścienna Charakteryzująca się znacznie większą temperaturą niż temperatura przepływającego ośrodka, powstająca na płytce jako elemencie grzewczym, odrywa się, a następnie miesza z pozostałą częścią płynu ogrzewając ją. Wykazano, że istnieje granica częstotliwości oscylacji, która w sposób znaczący poprawia efektywność grzania czynnika roboczego. Badania wykonano w ramach projektu ESA PECS 98104 Gas Resistojet Thruster for Medium Size Satellite Attitude Control.
EN
Electric rocket propulsion belong to the group of rocket engines which use thermal energy converted from electric. This energy conversion is crucial problem for this kind of rocket engines. The electric rocket engines are divided by methods of energy conversion and in this work is presented solution for resistance rocket engines called "resistojet". Resistojets are mostly used as a propulsion for attitude control system of satellite platforms because their simplicity, relative high specific impulse and long work-time duration ability. Recently development of new solutions and new materials have significantly increased the efficiency of energy conversion and decreased losses of thermal energy in resistojets. New solution proposed to the resistojets is heat exchanger with flat plate. The phenomena of thermal boundary layer created on surface of plate is additional intensify by high frequency oscillating. Because of dynamic move the boundary layer is broken and mixed in downstream flow. Mixed fluid increase own temperature and enthalpy that is converted to high velocity in the supersonic nozzle. In this work was shown that there is limitation of frequency oscillation of flat plate to enhance thermal process to heating fluid. This work was done as a part of project "ESA PECS 98104 Gas Resistojet Thruster for Medium Size Satellite Attitude Control".
6
Content available Rotating detonation engine simulations in-house code - REFloPS
Folusiak M., Kobiera A., Wolański P.
Prace Instytutu Lotnictwa
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2010
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Nr 5 (207)
3-23
EN
The paper presents the results of three-dimensional preliminary simulations of a detonation propagating in Rotating Detonation Engine chamber. Simulations were performed using in-house code REFloPS (Reactive Euler Flow Solver for Propulsion Systems)[1]. The description of the code and presented results are also included in MSc thesis of Folusiak and Swiderski [2].
PL
W artykule przedstawiono wyniki trójwymiarowych symulacji detonacji w komorze silnika z wirującą detonacją (RDE). Symulacje przeprowadzono przy użyciu kodu REFloPS, który jest wynikiem pracy magisterskiej dwóch pracowników Instytutu Lotnictwa.
7
Content available remote Experimental and numerical research on rotating detonation in a small rocket engine model
Kindracki J., Kobiera A., Wolański P.
Silniki Spalinowe
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2009
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R. 48, SC2
392--400
EN
The paper describes reserch on posibility of use rotating detonation in rocket engine. The basic properties of the wave propagation were studied. Next the parameters of the rocket engine based on the rotating detonation were measured. The experimental reserch were supprote by numerical simulations which allow detailed analysisi of the structure of the detonation wave and the flow in the detonation chamber.
PL
Artykuł prezentuje wyniki badań nad możliwościom zastosowania detonacji wirującej w silniku rakietowym. W pierwszej fazie badań określono podstawowe własności takiej fali detonacyjnej. Następnie dokonano pomiarów osiągów silnika rakietowego wykorzystującego detonację wirującą. Badania doświadczalne były uzupełnione obliczeniami numerycznymi w celu określenia szczegółów struktury wirującej detonacji i przepływu w komorze detonacyjnej.
8
Content available Analiza dynamiczna komory do badania urządzeń górniczych w warunkach eksplozji
Klemens R., Zagrajek T., Kobiera A., Żydak P., Kozioł S., Zbrowski A.
Problemy Eksploatacji
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2009
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nr 3
97-106
PL
W artykule przedstawiono przebieg i wyniki analizy obciążeń działających na płaszcz komory ciśnieniowej przeznaczonej do badania urządzeń górniczych w atmosferach gazów palnych w warunkach wybuchu. Przeprowadzono analizę zależności maksymalnego ciśnienia wywołanego wybuchem od rodzaju mieszanin gazowych i charakteru ich spalania. Określono maksymalne naprężenia występujące w płaszczu komory podczas wybuchu i wymagania wytrzymałościowe materiału konstrukcyjnego przeznaczonego do jego budowy.
EN
The article presents the course and results of the analysis of loads influencing the shell of the pressure chamber meant for testing mining devices in the combustible gas atmospheres in the explosion conditions. The analysis of the dependence of maximum pressure caused by the explosion on the type of gaseous mixtures and the character of their combustion was carried out. The maximum stresses occurring in the chamber's shell during the explosion and resistance requirements of the engineering material meant for building the shell were determined.
9
"REFLOPS" - a New Parallel CFD Code for Reactive Euler Flow Simulation
Kobiera A., Świderski K., Folusiak M., Wolański P.
Archivum Combustionis
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2009
|
Vol. 29 nr 3-4
111-152
EN
A new parallel code for reactive flow simulation “REFLOPS” is presented. The code is based on Euler model of inviscid gas motion. The first part of the paper describes the numerical methods used in the code and its structure. Then, results of several test are presented. Finally, an example of application of this code to simulation of a Rotating Detonation Engine (RDE) is presented.
10
The Possibility of the Use of High Explosive Layers in Ram Accelerators
Kobiera A., Wolański P.
Archivum Combustionis
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2008
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Vol. 28 nr 3-4
149-171
EN
The possibility of the use a high energetic solid material in a ram accelerator is discussed in this paper. First, some facts about multiphase combustion observed in ram accelerators are presented. While the core problem of using high explosive in supersonic propulsion is fast combustion, the first stage of work consisted of measuring ignition delays of selected high explosives. The ignition is triggered by a passing detonation wave. The experimental results proved that those materials can be applied to the ram accelerator and PETN has been selected as the best material. Next, a numerical model of ignition and combustion of a high explosive layer in a ram accelerator has been created and applied in numerical simulations. The obtained results allowed estimations of thrust enhancement and parametric analysis of the influence of some parameters on performances of the device. It was found that use of layers of high explosive can increase the generated thrust by about 10%. However this depends on such parameters as the speed of the projectile, initial pressure of the gaseous mixture, and the geometry of the projectile.
11
Combustion of high explosive layers Ignited by detonation waves
Kobiera A., Wolański P.
Archivum Combustionis
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2004
|
Vol. 24 nr 1-2
3-20
EN
The paper presents results of experimental work on ignition of layers of high explosive initiated by detonation wave. The high explosive layers were placed on the bottom wall of a detonation tube in which the detonation wave propagated. Measured ignition delay was in the order of some scores of microseconds and combustion of the layer had deflagrative character. Analysis of experimental results showed that ignition mechanism had mainly thermal nature and relation between ignition delay and temperature behind detonation wave could be described by Arrhenius' law. Also influence of combustion of high explosive on pressure behind detonation wave was investigated.
12
Characteristics of a ram accelerator with a high explosive layer
Kobiera A., Wolański P.
Archivum Combustionis
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2004
|
Vol. 24 nr 1-2
21-38
EN
The paper presents possibility of improvement a ram accelerator. First part of the paper shortly describes different propositions of modifications of the device. The attention is focused on problems connected with use of different kind of propellants: gaseous and solid. A ram accelerator with high explosive layer is chosen to further analysis. A mathematical model of such device is derived. Solution of the model is analytical (algebraic) for subdetonative mode. A numerical solution was obtained for superdetonative mode. Characteristics of the ram accelerator show that the thrust can be significantly increased by combustion of the layer, especially in subdetonative mode.
13
Modelling of Ignition of PETN Layer by Gaseous Detonation
Kobiera A., Wolański P.
Archivum Combustionis
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2003
|
Vol. 23 nr 3-4
147-167
EN
Development of a new kind of ram accelerators with a high explosive layer is strictly connected with the research into combustion of high-energetic materials. In the paper there is presented mathematical model of ignition and combustion of PETN layer caused by propagating gaseous detonation. The model is based on the previous experimental research which allowed estimating basic features of the process e.g. activation energy of the explosive. The model was applied in numerical simulation. Computations and experimental data showed good qualitative agreement.
14
Możliwości zastosowania warstw skondensowanych materiałów palnych w ram akceleratorach
Wolański P., Kobiera A.
Prace Naukowe Politechniki Warszawskiej. Konferencje
|
2002
|
T. 4, z. 22
1355-1362
PL
W artykule krótko omówiono zasadę działania ram akceleratorów (ang. ram accelerator, ramac) i przeanalizowano możliwość poprawy ich osiągów przez zastosowanie warstwy skondensowanych mateńałów palnych. Druga część referatu poświęcona jest omówieniu badań nad zapłonem warstw palnych pod wpływem przejścia detonacji gazowej, które przeprowadzono na Politechnice Warszawskiej. Wyniki badań potwierdzają możliwość zastosowania warstw palnych substancji w ram- akceleratorach.
EN
An article considers methods of improving of ram accelerators performances by use of a combustible layers on walls of a tube. A general principle of ram accelerator's work is given in first part. Feasibility of implementing of combustible layer is analysed on the basis of research carried out in Warsaw University of Technology. Subject of the investigation is ignition of the layers caused by passing of detonation wave. This investigation shows that condensed explosive layers could be effectively used in ram accelerators since they are easily to ignite (initiate).
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