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1
Content available Design and validation of a single-jack variable Mach number nozzle in a cryogenic transonic wind tunnel
Yu Chengguo, Zhang Zhili, Wang Ning, Nie Xutao, Peng Qiang, Chen Zhenhua
Journal of Theoretical and Applied Mechanics
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2022
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Vol. 60 nr 4
719--732
EN
The wind tunnel with variable Mach numbers controlled by a single jack is highly desired in the aerospace, automobile and building industry due to its superior controllability and working range. Decreasing the temperature of a test gas is an efficient and economical approach to achieving higher Reynolds numbers that accommodate all working statuses of test subjects, which however, brings new challenges to the wind tunnel design nowadays. This paper proposes a new design concept of a single-jack variable Mach number nozzle based on its particular cryogenic characteristics, as the nozzle is the core structure to achieve variable Mach numbers. The contours of the nozzle under different Reynolds numbers and Mach numbers are modeled and solved by an incomplete elliptic integral, followed by modification with cryogenic characteristics. A 0.3-m cryogenic wind tunnel is utilized as a validation platform for the nozzle design, resulting in designed contours being in line with the measured contours. Moreover, the root means square (RMS) deviations of Mach number 1.3 at the core position are controlled within 0.011 in low and high temperatures, which surpasses the other existing wind tunnels.
2
Content available Fuzzy-based prediction for suddenly expanded axisymmetric nozzle flows with microjets
Quadros Jaimon D., Suhas P., Khan Sher A., Aabid Abdul, Baig Muneer, Mogul Yakub I.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2022
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Vol. 70, nr 5
art. no. e142654
EN
The current research focuses on the implementation of the fuzzy logic approach for the prediction of base pressure as a function of the input parameters. The relationship of base pressure (β ) with input parameters, namely, Mach number (M), nozzle pressure ratio (η), area ratio (α), length to diameter ratio (ξ ), and jet control (ϑ ) is analyzed. The precise fuzzy modeling approach based on Takagi and Sugeno’s fuzzy system has been used along with linear and non-linear type membership functions (MFs), to evaluate the effectiveness of the developed model. Additionally, the generated models were tested with 20 test cases that were different from the training data. The proposed fuzzy logic method removes the requirement for several trials to determine the most critical input parameters. This will expedite and minimize the expense of experiments. The findings indicate that the developed model can generate accurate predictions
3
Content available Analytical dynamic model of coefficient of friction of air pipeline under pressure
Dmytriv Vasyl, Dmytriv Ihor, Horodetskyy Ivan, Dmytriv Taras
Diagnostyka
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2019
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Vol. 20, No. 4
89--94
EN
To transport of the air in the pipeline, an analytical model is developed that takes into account the gas velocity, its kinematic and dynamic characteristics - density, viscosity depending on the pressure in a given space of the pipeline. The analytical model makes it possible to calculate the coefficient of friction of gas transportation in the pipeline at intervals of the absolute pressure from 220 to 2 kPa and M < 1 Mach numbers, depending on the diameter and length of the pipeline and physical and technological characteristics of the gas. The K1* aspect ratio is proposed, which characterizes in time the ratio of the dynamic force of movement of gas to the static pressure related to the diameter of the pipeline. The coefficient of air friction was modeled according to the vacuum pressure as a parameter of density and air flow. Air flow was taken from 1.917·10-3 m 3/s to 44.5·10-3 m 3/s respectively, diameters from 0.030 to 0.070 m and Mach number was M = 0.005-0.13. At the vacuum and excess pressures with increasing of Reynolds number and decreasing of Mach number the gas friction coefficient increased linearly. According to the simulation results as the pressure loss and the diameter of the pipeline are increased the friction coefficient increased as well. Analogically, at the vacuum metric pressure when the pressure loss and the diameter of the pipeline are increased the friction coefficient increased. At the pipeline internal diameters of 22, 30, 36 mm accordingly for pressure losses from 2 to 14 kPa the coefficient of air friction varies from 0.006 to 54.527 respectively.
4
Content available Nowe rozwiązania środków transportu na przykładzie kolei niskociśnieniowej
Rydzek Marcin
Autobusy : technika, eksploatacja, systemy transportowe
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2019
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R. 20, nr 6
116--119
PL
W pracy przedstawiono przyszłościowy środek lokomocji w postaci technologii kolei niskociśnieniowej - Hyperloop. Opisano stan obecny wdrażanej technologii oraz odniesiono się do problemów związanych prędkościami w tunelu próżniowym, gdzie jednym z podstawowych jest granica Kantrowitza. Montaż turbosprężarek ma temu zapobiec, lecz taka strategia jest zbyt kosztowna. Przedstawiona technologia może stanowić alternatywę dla obecnych środków transportu.
EN
The paper presents a forward-looking means of transport in the form of hyperloop technology. The paper describe current state of the implemented technology and refers to the problems related to speeds in a vacuum tunnel. The basic problem related to speed is the limit of Kantrowitz. The presented technology can be an alternative to the current means of transport.
5
Content available remote Base pressure behaviour in a suddenly expanded duct at supersonic Mach number regimes using Taguchi design of experiments
Quadros J. D., Khan S. A., Antony A. J.
Mechanics and Mechanical Engineering
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2018
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Vol. 22, nr 4
1077--1097
EN
Experimental investigations are carried out to study the control of base pressure without and with the use of micro-jets through suddenly expanded axi-symmetric passage in the supersonic regime. Four micro jets having an orifice diameter of 1mm were located at 90˚ intervals. In the base area, active controls jets have been placed on a pitch of a circle diameter that is 1.3 times the exit diameter of the nozzle. The jets were dispensed abruptly into the axi-symmetric tube maintained at a cross-sectional area of 4.84 times the exit nozzle area. The variation of base pressure as a function of flow control parameters namely Mach number, nozzle pressure ratio (NPR) and length to diameter) ratio (L=D) are evaluated experimentally. This study also assesses the impact of flow control variables on base pressure for two cases viz. with control and without control respectively. An L9 orthogonal array of Taguchi and the analysis of variance were employed to investigate the percentage of contribution of these parameters and their interactions affecting the base pressure. The correlations between the various factors affecting the base pressure were obtained by using multiple linear regression equations. Confirmation tests were conducted in order to test the developed linear regression equations for their practical significance. Both the regression models were found to be significant and reliable with a percentage deviation lying in the range of -6:12% to 10.26% for base pressure without control and -13:92% to 6.58% for base pressure with control. Analysis of variance was also performed in order to determine the statistical significance of each parameter on the total variability of base pressure. The study concluded that Mach number is the most in fluential parameter affecting base pressure followed by NPR and L=D.
6
Content available Study of base pressure behavior in a suddenly expanded duct at supersonic Mach number regimes using statistical analysis
Quadros J. D., Khan S. A., Antony A. J.
Journal of Applied Mathematics and Computational Mechanics
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2018
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Vol. 17, nr 4
59--72
EN
The present experimental evaluation deals with the behavior of base pressure (BP) in a suddenly expanded duct at supersonic Mach number regimes. The experiments have been conducted for two cases viz. Without and with the use of microjets or active control. The plan of experiments was planned as per Taguchi design of experiments for acquiring data in a controlled manner. An L27 orthogonal array and analysis of variance (ANOVA) has been employed to investigate the contribution (in terms of percentage) of distinct process parameters like Mach number (M), Nozzle Pressure Ratio (N), Area Ratio (A) and their interactions affecting base pressure. The correlation between these parameters affecting base pressure has been obtained using multiple linear regression analysis. It has been concluded that the Mach number and area ratio were the factors that had high statistical significance on the behavior of base pressure for both cases. The performances of the developed linear regression models have been validated for accuracy prediction by use of 15 test cases. The performance of both the base pressure models was found to be better with percentage prediction in deviation lying in the range of –12.92% to +15.88% for base pressure without control and –10.27% to +19.23% for base pressure with control.
7
Content available remote A study of rotational gas flows
Bagewadi C. S., Bhagya S.
International Journal of Applied Mechanics and Engineering
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2006
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Vol. 11, no 3
547-556
EN
We decompose the compatibility equations of steady rotational gas flows and obtain solutions in three dimensional flows and also Mach numbers on the surfaces (i) small spherical balls (ii) in circular tunnels. Further cavity ratio for the critical Mach number is discussed using hodograph transformation.
8
Content available remote Zastosowanie metody "preconditioning" do obliczenia przepływów ściśliwych
Tyliszczak A., Barbante P.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
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2000
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nr 117, vol. 2
175-180
PL
W niniejszej pracy przedstawiono zastosowanie metody "preconditioning" do rozwiązywania przepływów ściśliwych dla małych liczb Macha. Na przykładzie prostego przepływu w kanale pokazano, że metoda ta w znacznym stopniu przyspiesza uzyskanie zbieżności procesu rozwiązywania oraz zwiększa dokładność obliczeniową uzyskiwanych wyników.
EN
The paper presents the preconditioning method applied to compressible flows for low Mach number. A testcase of channel flow shows that the method speeds up significantly the convergence of the iterative scheme and improves approximation accuracy.
9
Content available remote Transoniczny opływ profilu w warunkach zmiennej wilgotności powietrza
Nosal Z., Selerowicz W.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
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2000
|
nr 117, vol. 1
85-90
PL
W pracy przedstawiono wyniki badań doświadczalnych transonicznego opływu profilu NACA0012 powietrzem wilgotnym. Obejmowały one pomiary ciśnień oraz wizualizacje pola przepływu. Przebadano pełny zakres wilgotności powietrza dla dwóch typowych przypadków transonicznego opływu profilu: z falą uderzeniową o średniej intensywności oraz z falą intensywną i wynikającym z tego oderwaniem warstwy przyściennej.
EN
Results of experimental investigations concerning transonic humid flow over NACA0012 airflow are presented. Pressure measurements and flow visualizations were made. Two typical cases of transonic flow in a wide range of air humidity were studied. The first one with a presence of a shock of middle intensity and the second one with a strong shock forcing boundary layer separation.
10
Content available remote Obliczanie płaskich poddźwiękowych przepływów gazu lepkiego metodą prostych
Kosma Z.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
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2000
|
nr 117, vol. 2
125-130
PL
Przedstawiono metodę wyznaczania niestacjonarnego ruchu gazu lepkiego w zakresie przepływów poddźwiękowych. Układ równań różniczkowych cząstkowych opisujący ruch gazu lepkiego sprowadzono do układu równań różniczkowych zwyczajnych względem czasu, po zastąpieniu wszystkich występujących w tym układzie pochodnych względem zmiennych przestrzennych symetrycznymi i niesymetrycznymi ilorazami różnicowymi. Wykonano obliczenia poddźwiękowego przepływu gazu w obszarze kanału z uskokiem ścianki metodami predyktor-korektor.
EN
The aim of this paper is to present a method for determining the unsteady motion of the viscous fully compressible fluid at subsonic Mach numbers. The proposed method of lines consists in discretizing the spatial derivatives by the use of the finite difference method and converting the solution of the compressible Navier-Stokes equations into a system of ordinary differential equations with respect the time, followed by some predictor-corrector methods. Efficiency of the algorithms was demonstrated by solving problem of compressible viscous flow for a 2D backward-facing step.
11
Content available remote Modelowanie nieustalonych sił aerodynamicznych
Nowak M.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
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2000
|
nr 117, vol. 1
85-90
PL
Znajomość zlinearyzowanych nieustalonych sil aerodynamicznych (czyli tzw. funkcji aerodynamicznej transmitancji operatorowej) odpowiadających małym zaburzeniom ruchu konstrukcji lub podmuchom, jest istotna dla analizy stabilności mchu układów aeroelastycznych. Na podstawie wyników obliczeń numerycznych oraz rozważań teoretycznych, zaproponowano ogólną postać liniowego (dyskretnego) operatora aerodynamicznego w dziedzinach Laplace* a i czasu, dla dwu- i trojwvmiarowveh nieustalonych oplywów poddźwiekowych. Jest on w pewnym sensie uogólnieniem znanego rozwiązania Theodorsena dla profilu w przepływie nieściśliwym.
EN
The knowledge of linearized unsteady aerodynamic forces i.e. the aerodynamic transfer matrices related to small structural motion and gusts, is essential for stability analyses of aeroelastic systems. On the basis of numerical results and theoretical considerations, a general form of the (unsteady) linear, discretized aerodynamic operator in the Laplace- and in the time-domain, for two- and three-dimensional subsonic flow is proposed. It corresponds to the classical Theodorsen solution lor an airfoil in incompressible flow.
12
Content available remote Kształtowanie szablowe przy stopie łopatek kierowniczych w stopniu wylotowym turbiny dużej mocy
Lampart P.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2000
|
nr 117, vol. 1
225-232
PL
Niniejsza praca stanowi studium numeryczne konstrukcji stopnia wylotowego turbiny dużej mocy z kształtowaniem szablowym łopatek kierowniczych u stopy. Obliczenia wykonano przy pomocy programu FlowER - solwera przepływu gazu przez maszyny wirnikowe w modelu 3D RANS. Przedstawiono korzyści wynikające z zastosowania kształtowania szablowego u stopy dla pracy stopni części niskoprężnej turbin, którymi są, przede wszystkim, zmiana rozkładu reakcyjności przy stopie wraz z odciążeniem łopatki kierowniczej i dociążeniem łopatki wirnikowej. Otrzymane zyski sprawności zalezą od natężenia przepływu i są największe dla niskich obciążeń
EN
The paper is a numerical study of the LP exit stage of a large-power turbine with stator blade compound lean at root. The computations are carried out with the help of a 3D RANS-based turbomachinery code FlowER. It is found that the application of compound lean at the root of stator blades can be advantageous for LP turbines, mainly by increasing reaction at the root, that is unloading the overloaded stator blade and reloading the underloaded rotor blade at the root. The CFD-predicted efficiency gains depend on the flow regime, and are the largest for low loads
13
Content available remote Badanie strat przepływowych w wieńcach łopatkowych stopni turbinowych z wykorzystaniem CFD. Cz. II Charakterystyki sprawnościowe
Gardzilewicz A., Lampart P., Świrydczuk J., Kwidziński R., Kosowski K.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
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2000
|
nr 117, vol. 1
187-192
PL
W Części II pracy nt. numerycznych badań strat przepływowych w wieńcach stopni turbinowych zamieszczono przykładowe charakterystyki palisad kierowniczych i wirnikowych części WP dla różnych parametrów geometrycznych i przepływowych palisady, opracowane przy użyciu metodologii przedstawionej w Części I. Charakterystyki te obrazują wpływ głównych parametrów geometrycznych, takich jak smukłość łopatki, podziałka palisady, kąt ustawienia profilu, oraz przepływowych, jak liczba Macha i kąt napływu strumienia, na współczynnik strat energii kinetycznej.
EN
Part II of the paper on CFD investigations of flow losses in turbine cascades presents sample characteristics of HP stator and rotor performance in a range of geometrical and flow parameters. The characteristics are elaborated based on the methodology described in Part I and illustrate the impact of the main geometrical parameters, like the chord/span ratio, pitch/chord ratio and stagger angle as well as flow parameters like the Mach number or inlet angle on the coefficient of kinetic energy losses.
14
Content available remote Shock-induced dynamics of an elastically turbine cascade at transonic flow
Urban B., Stetter H., Vortmeyer N.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
1999
|
nr 115
387--396
EN
This paper presents experimental investigations on shock-induced flutter in a linear transonic turbine cascade. To examine these phenomena, an elastic suspension system has been developed so that only aerodynamic coupling occurs. The profiles are typical for the tip section of a transonic low pressure steam turbine last stage. The examination at the two-dimensional test rig with superheated steam as working fluid mainly deals with the oscillatory behaviour of the blades with respect to a variation of the isentropic outlet Mach number. In addition, the complex shockboundary layer interactions on the blades' suction sides are described.
15
A pair of equal collinear interfacial griffith cracks
Das S., Patra B.
Applied Mechanics and Engineering
|
1999
|
Vol. 4, no 1
97-112
EN
The plane strain problem of determining stress intensity factors and crack energy for a pair of equal collinear moving Griffith cracks situated at the interface of two bonded dissimilar orthotropic half planes has been considered. The problem is reduced to solving a pair of simultaneous singular integral equations which have finally been solved by using Jacobi polynomials. Expressions for stress intensity factors and crack energy are obtained for some particular cases and the results are presented graphically.
16
Absolute instability in the compressible three dimensional boundary layer
Tuliszka-Sznitko E.
Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska
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1998
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z. 7
453-458
EN
In the present paper the character of instability of compressible three dimensional viscous flow is analyzed. Following the works of Briggs and Bers in the field of plasm a physics - , the absolute instability region is identified by singularities of dispersion relation called pinch - points . Regions of absolute instability in boundary layers of a rotating cone have be n found . Calculations have been made for different Mach numbers , wall temperatures and rotational speeds of the cone.
PL
Badany jest charakter niestabilności przepływu ściśliwego, lepkiego i trójwymiarowego . Zastosowano kryterium Briggsa i Bersana niestabilność absolutną zgodnie z którym o charakterze niestabilności decydują osobliwość i funkcji dyspersji . Obliczenia przeprowadzono dla stożka wirującego w przepływie jednorodnym. Badano wpływ liczby Macha , temperatury ścianki oraz liczby Reynoldsa crossflow na obszary absolutnie niestabilne.
17
Two collinear griffith cracks in an orthotropic strip with punches
Singh P. C., Patra B., Maulik T. N.
Applied Mechanics and Engineering
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1998
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Vol. 3, no 4
621-653
EN
Integral transform technique is employed to solve the elastodynamic problem of steady-state propagation of two symmetrically situated identical collinear Griffith cracks along the mid plane of orthotropic strip of finite thickness 2h with centrally situated moving punches along the boundaries of the layer. The problem is reduced to the solution to a pair of simultaneous singular integral equations with Cauchy type singularities which have finally been solved through finite Hilbert transform technique. For large h, analytical expressions for the local stress field near the crack tip and the stress intensity factors are obtained. Graphical plots of the numerical results are also presented.
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