Wyniki wyszukiwania - BazTech

1

Metodyka badań eksperymentalnych rozwoju i zaniku stanu pierścienia wirowego

Surmacz K., Ruchała P., Stryczniewicz W.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

|

2016

|

Vol. 7, Nr 1 (23)

79--96

PL

Jednym z zagrożeń bezpieczeństwa lotu śmigłowców jest stan pierścienia wirowego (ang. Vortex Ring State - VRS). W niniejszej pracy przedstawiono metodykę oraz przykładowe wyniki badań eksperymentalnych dotyczących zagadnienia VRS, przeprowadzonych w tunelu aerodynamicznym Instytutu Lotnictwa. Badanym obiektem był zdalnie sterowany śmigłowiec, umieszczony w przestrzeni pomiarowej tunelu niskich prędkości o średnicy 1,5 m. Zakres badań obejmował pomiary wagowe za pomocą wagi tensometrycznej oraz badania wizualizacyjne metodą anemometrii obrazowej (PIV). W trakcie prowadzonych testów zarejestrowano spadek siły ciągu generowanej przez wirnik nośny śmigłowca towarzyszący wejściu w stan pierścienia wirowego oraz dokonano wizualizacji powstałych struktur wirowych. Uzyskane wyniki potwierdziły, że przyjęta metodyka jest skuteczna do analizy procesu rozwoju i zanikania pierścienia wirowego na wirniku nośnym śmigłowca.

EN

The Vortex Ring State (VRS) of the main rotor is one of the threats for the safety of a helicopter. Therefore this phenomenon has been intensively investigated for several years, in order to understand the mechanisms of its development and the possibilities of avoiding the danger flight regime. The paper presents a research methodology applied for investigations of development of the VRS of the main rotor of a helicopter. The object of investigation was a model of a helicopter with a powered rotor, placed in a low-speed wind tunnel with test section diameter of 1.5 m. The investigation includes a strain gage measurements and flow visualization with the Particle Image Velocimetry (PIV) method. The results show the decrease in the thrust generated by the main rotor due to the VRS. The velocity field, measured with PIV method, shows the process of the VRS forming, development and demise. The results proved the feasibility of the presented methodology for investigation of the Vortex Ring State.

2

Study on the effect of the descent rate of a helicopter in the Vortex Ring conditions

Surmacz K., Kowaleczko G.

Journal of KONES

|

2016

|

Vol. 23, No. 1

345--352

EN

One of the limiting factors for a helicopter operation is the Vortex Ring State (VRS). This aerodynamic phenomenon, known as the VRS or “Settling with Power”, is characterized by the formation of circulating air stream moving along a ring shaped track around the main rotor of a helicopter. Conditions, conducive to development of the vortex ring state, occur in the vertical or nearly vertical descent. This leads to decrease in thrust and thus rapidly increasing the rate of descent. This phenomenon occurs for an appropriate combination of induced velocity and the velocity of the stream of airflow from the bottom to the rotor. The rates of change of velocities delimit dangerous areas of flight. The objective of this work was to investigate the influence of the descent rate of a helicopter on the vortex ring formation process and determinants of the occurrence of vortex rings. For better understanding of the nature of this state, a computational method was applied. Series of three-dimensional (3D) unsteady analysis was carried out using Computational Fluid Dynamics tools (CFD). Simulations were realized using geometry and performance of the W-3 “Sokol” helicopter. The paper presents results of a helicopter operation in axial and non-axial descent conditions. Three calculation cases of vertical flight of a helicopter with different rates of velocity changes were considered. A simulation of non-axial descent was based on the measured flight test data for the W-3 helicopter. The results provide information about the changing nature of the flow in the course of the movement of a helicopter and show the influence of the rate of descent during initiation on the development of VRS. Results of the calculations provide guidelines for helicopter pilots.

3

Experimental and computational studies of stall on a helicopter rotor airfoil

Surmacz K.

Journal of KONES

|

2016

|

Vol. 23, No. 3

511--517

EN

In the case of forward flight of a helicopter, the flow field around rotating blades of a rotor is highly threedimensional and very complex. Helicopter blades work across a wide range of angles of attack and airspeed. The stall occurs on the retreating blade in forward flight and causes dissymmetry of lift on a rotor disc. The investigation of the stall phenomenon has been performed using experimental and computational methods. Experimental analysis was made at the Ohio State University 6’’x 22’’ unsteady transonic wind tunnel. Research in the wind tunnel was performed using two methods: oil visualization (over a wide range of alpha and Ma) and pressure measurements. Computational part of the research has been done using Computational Fluid Dynamics tool. 2- and 3-dimensional calculations performed using ANSYS FLUENT software. In both experimental and computational cases, the 3D flow around a section of a rotor blade based on the SSC-A09 airfoil was analysed. The test article of the research was a section, which was located in the tip region of the main rotor blade of UH-60M Black Hawk helicopter. The research was conducted for a wide range of angles of attack and at several velocities. The most interesting part of the analysis concerned on unsteady flow conditions corresponding to stall.

4

Badania eksperymentalne stanu pierścienia wirowego na wirniku nośnym śmigłowca metodą anemometrii obrazowej (PIV)

Stryczniewicz W., Surmacz K.

Prace Instytutu Lotnictwa

|

2014

|

Nr 2 (235) June 2014

17--27

PL

W pracy przedstawiono wyniki badań wizualizacyjnych w tunelu aerodynamicznym przeprowadzonych w celu zbadania stanu pierścienia wirowego na wirniku nośnym śmigłowca. Badania wizualizacyjne przeprowadzono metodą anemometrii obrazowej (PIV). Cechą charakterystyczną opadania śmigłowca w warunkach stanu pierścienia wirowego (VRS, Vortex Ring State) jest powstanie wokół wirnika cyrkulacyjnego ruchu strug powietrza po torach w kształcie pierścieni. W przeprowadzonych badaniach warunki VRS uzyskano poprzez umieszczenie modelu śmigłowca w przestrzeni pomiarowej tunelu tak, aby oś wirnika nośnego pokrywała się z osią symetrii przestrzeni pomiarowej. Wykonane analizy potwierdziły skuteczność sytemu PIV stosowanego w Laboratorium Badań Aerodynamicznych Instytutu Lotnictwa do badań opływu śmigłowa z pracującym wirnikiem oraz stanowią przyczynek do kontynuacji badań nad dynamiką powstania stanu pierścienia wirowego na wirniku nośnym śmigłowca.

EN

The paper presents results of the investigation of the vortex ring state (VRS, settling with power) of the main rotor of a helicopter with the use of Particle Image Velocimetry (PIV) method. One of the most distinguished features in the conditions known as settling with power is a formation of toroidal vortices around the rotor of a helicopter. In order to provide the necessary conditions for the development of VRS the rotation axis of the main rotor and the axis of symmetry of the wind tunnel’s test section were set coaxially. The results of the measurements proved the feasibility of the Applied Aerodynamics Laboratory’s PIV system for investigations of the flow over a powered rotor in a test section of the wind tunnel. The presented results constitute a contribution to performance of a more detailed research on the development of the VRS of the main rotor of a helicopter.

5

An improved algorithm for feature extraction from a fingerprint fuzzy image

Surmacz K., Saeed K., Rapta P.

Optica Applicata

|

2013

|

Vol. 43, nr 3

515--527

EN

Proper fingerprint feature extraction is crucial in fingerprint-matching algorithms. For good results, different pieces of information about a fingerprint image, such as ridge orientation and frequency, must be considered. It is often necessary to improve the quality of a fingerprint image in order for the feature extraction process to work correctly. In this paper we present a complete (fully implemented) improved algorithm for fingerprint feature extraction, based on numerous papers on this topic. The paper describes a fingerprint recognition system consisting of image preprocessing, filtration, feature extraction and matching for recognition. The image preprocessing includes normalization based on mean value and variation. The orientation field is extracted and Gabor filter is used to prepare the fingerprint image for further processing. For singular point detection, the Poincaré index with a partitioning method is used. The ridgeline thinning is presented and so is the minutia extraction by CN algorithm. The paper contains the comparison of obtained results to the other algorithms.