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Khan, She Afgha - One of the best experts on this subject based on the ideXlab platform.

  • Experiment on of nozzle flow with sudden expansion at Mach 1.1
    Blue Eyes Intelligence Engineering & Sciences Publication, 2019
    Co-Authors: Faheem Mohammad, Aabid Abdul, Kareem Ullah Mohammad, Mokashi Imra, Khan, She Afgha
    Abstract:

    This present study discusses the outcome of the experimental investigations, and the efficacy of the tiny jets used to regulate the Base Pressure as well as the wall Pressure in suddenly expanded flow. The control mechanism as tiny jets having a cross-section of 1 mm diameter was employed as the Base Pressure regulator at the exit periphery of the nozzle. The experiments were carried out to investigate and record the flow field at the rear end of the separated flow region for area ratio 4.84. Four tiny jets were placed at a distance of 6.5 mm away from the primary jet coming from the nozzle exit at ninety degrees apart, and the tiny control jets were flowing at sonic Mach number. The actual Mach number of the main jet was 1.1. The experimentation was accomplished at a different level of expansion (i. e., NPR = 3, 5, 7, 9, and 11) and the L/D ratio considered was from 10 to 1. This study mainly focuses on the development of the flow in the suddenly expanded duct, nature of the flow in the duct, and the impact of the Control on the wall Pressure and the magnitude of the Pressure along the duct. The wall Pressure in the smooth duct is not unfavorably influenced by the control jets

  • Effect of nozzle Pressure ratio and control jets location to control Base Pressure in suddenly expanded flows
    REGIONAL INFORMATION CENTER FOR SCIENCE AND TECHNOLOGY, 2019
    Co-Authors: Pathan, Khize Ahmed, Dabeer, Prakash S, Khan, She Afgha
    Abstract:

    In this paper, computational fluid dynamic (CFD) analysis and experiments have been carried out to study the effect of nozzle Pressure ratio, i.e. the ratio of inlet Pressure to atmospheric Pressure, and the pitch circle diameter of the control jets to regulate the Base Pressure. The variables considered for the analysis as well as the experiments are the nozzle Pressure ratio (NPR), the Mach number (M) and the pitch circle diameter (PCD) of the control jets. The area ratio considered for the study is kept constant at 4.84 while the length to diameter (L/D) ratio of an enlarged duct is set constant at 5. The inertia parameter considered for the study is the Mach number. The Mach numbers considered for the study are 1.5, 2.0, and 2.5. The nozzle Pressure ratio considered for the study is 2, 5 and 8. Three different pitch circle diameters of control jets considered for the study are 13.1 mm, 16.2 mm and 19.3 mm. From the numerical simulations and the results of the experimental tests, it is found that the control jets are very beneficial to increase the Base Pressure at higher NPR when the jets issuing from the nozzles are under-expanded. The control jets were able to increase the Base Pressure value from 160% to 400% at a nozzle Pressure ratio 8. It is concluded that the parameter D3 is the most effective pitch circle diameter of the control jets to increase the Base Pressure

  • Effect of area ratio on Base Pressure and control effectiveness
    Blue Eyes Intelligence Engineering & Sciences, 2019
    Co-Authors: M, Fharukh G Ahmed, Khan, She Afgha
    Abstract:

    Reducing the Base drag and increasing the Base Pressure from aerodynamic devices involving suddenly expanded flows is of vital importance due to the higher rate of drag associated with them. The experimental effort put into understanding the variation in Base Pressure using active control of suddenly expanded flows employing microjets is reported in this article. The effect of tiny jets and nozzle Pressure ratio (NPR), and length to diameter (L/D) ratio on the percentage change in Base Pressure is investigated at supersonic Mach numbers at 1.7, 2.3, and 2.7, for area ratios of 2.56, 5.06, and 7.56. Apart from NPR, the L/D ratio has an influential role in percentage change in Base Pressure at different Mach numbers. An improvement of up to 360 % in Base Pressure is obtained with the use of sonic microjets at a particular Mach number and L/D ratio

  • Role of active control in increasing Base Pressure at Sonic Mach Number
    Blue Eyes Intelligence Engineering & Sciences, 2019
    Co-Authors: M, Fharukh G Ahmed, Khan, She Afgha
    Abstract:

    Use of microjets as an active control mechanism to control the Base Pressure in suddenly expanded flow from the C-D nozzle exhausted to the duct is investigated in this article. Experimental analysis is carried out at sonic Mach number and different nozzle Pressure ratios. The enlarged diameter used in this investigation is 16 mm, 22.5 mm, and 27.5 mm. The length and diameter of the duct where the flow expands are also varied during the analysis. The role played by four micro jets of 1 mm diameter as an orifice to regulate the Base Pressure. The results as the percentage increase in Base Pressure are plotted for different level expansion and area ratio. For higher NPR = 7, the control significantly increases the Base Pressure without disturbing the wall Pressure distribution. L/D = 3 and 4 seems to be optimum in resulting in a maximum increase in Base Pressure. For lower area ratio the minimum duct length required is L/D =3, whereas for the highest area-ratio this limit is L/D =4

  • Analysis of area ratio in a CD nozzle with suddenly expanded duct using CFD method
    Penerbit Akademia Baru, 2019
    Co-Authors: Khan, She Afgha, Aabid Abdul, Ghasi, Fharukh Ahmed Mehaboobali, Al-robaia Abdulrahma, Alsagri, Ali Sulaima
    Abstract:

    Whereas the demand for missiles and rockets has exponentially augmented, but the difficulties related to the gas dynamics of these vehicles remains to be a threat. Whenever there is a sudden expansion, the Pressure in the downstream is subatmospheric. This low Pressure in the recirculation zone leads to a considerable amount of drag, which is nearly two-thirds of the net drag of the aerospace vehicles. Hence, in view of the above problem, many researchers tried to control the Base Pressure depending upon the mission requirements. For example, in case of combustion chamber, we would like to decrease the Base Pressure as low as possible to have better mixing and efficient combustion, whereas, in case of the external ballistics application we would like to increase the Base Pressure as high as possible to reduce the drag of the projectiles to enhance the range. In this paper, investigated the effects of an area ratio in suddenly expanded duct and Base Pressure control with microjets using the computational fluid dynamics (CFD) method. A 1 mm orifice diameter of microjets placed at the pitch circle diameter (PCD) of 13 mm, located at 90 degrees for active control. The Mach number is M = 2.2, the L/D ratio is 8, the nozzle Pressure ratio’s (NPR) is 9 and the area ratios are 2.56, 3.24, 4.86 and 6.25 considered in the present study. The design and modeling of convergent-divergent (CD) nozzle simulated using K-ε turbulence model for standard wall function. From the present results, it has been observed that the area ratio plays a crucial role in fixing the Base Pressure values

Khan, Sher Afghan - One of the best experts on this subject based on the ideXlab platform.

  • Prediction of Base Pressure in a suddenly expanded flow the processes at supersonic Mach Number Regimes using ANN and CFD
    'Armenian Green Publishing Co.', 2020
    Co-Authors: Quadros, Jaimon Dennis, Khan, Sher Afghan
    Abstract:

    The sudden expansion of flow in a supersonic flow regime has gained relevance in the recent pasts for a wide run of applications. A number of kinematic as well as geometric parameters have been significantly found to impact the Base Pressure created within the suddenly expanded stream. The current research intends to create a predictive model for Base Pressure that is established in the abruptly extended stream. The artificial neural network (ANN) approach is being utilized for this purpose. The dataBase utilized for training the network was assembled utilizing computational fluid dynamics (CFD). This was done by the design of experiments Based L27 Orthogonal array. The three input parameters were Mach number (M), nozzle Pressure ratio (NPR) and area ratio (AR) and Base Pressure was the output parameter. The CFD numerical demonstrate was approved by an experimental test rig that developed results for Base Pressure and used a nozzle and sudden extended axisymmetric duct to do so. The ANN architecture comprised of three layers with eight neurons in the hidden layer. The algorithm for optimization was Levenberg-Marquardt. The ANN was able to successfully predict the Base Pressure with a regression coefficient R2 of less than 0.99 and RMSE=0.0032. The importance of input parameters influencing Base Pressure was estimated by using the ANN weight coefficients. Mach number obtained relative importance of 47.16% claiming to be the most dominating factor

  • Investigation and back-propagation modeling of Base Pressure at sonic and supersonic Mach numbers
    'AIP Publishing', 2020
    Co-Authors: Afzal Asif, Khan, Sher Afghan, Khan Ambareen, Islam, Md. Tariqul, Jilte R. D., Soudagar, Manzoore Elahi M.
    Abstract:

    The experimental analysis of Base Pressure in a high-speed compressible flow is carried out. The flow is made to expand abruptly from the nozzle into an enlarged duct at fifteen sonic and supersonic Mach numbers. The analysis is made for variation in the nozzle Pressure ratio (NPR), length to diameter ratio, and area ratio. The effect of active micro-jets on the Base and wall Pressure is assessed. The data visualization of the huge experimental data generated is performed using heat maps. For the first time, six back-propagation neural network models (BPMs) are developed Based on input and output possibilities to predict the Pressure in high-speed flows. The experimental analysis revealed that depending upon the type of expansion, the Base Pressure changes. A jet of air blown at the Base using micro-jets is found to be effective in increasing the Base Pressure during the under-expansion regime, while the wall Pressure remains unaffected. The data visualization provided an insight into the highest impact on the Base Pressure by the NPR. The six BPMs with two hidden layers having four neurons per layer are found to be most suitable for the regression analysis. BPM 5 and BPM 6 accurately predict the highly non-linear data of the Base and wall Pressure

  • An investigation of effect of control jets location and blowing Pressure ratio to control Base Pressure in suddenly expanded flows
    'Journal of Thermal Engineering', 2020
    Co-Authors: Pathan, Khizar Ahmed, Dabeer, Prakash S, Khan, Sher Afghan
    Abstract:

    The drag force is an essential factor in any projectile from road vehicles to rocket or aircraft. The total drag includes skin friction drag, wave drag, and Base drag. The Base drag is the drag due to low Pressure in the Base region of the projectile. In the case of suddenly expanded flows, due to the sudden expansion of flow from the nozzle into the enlarged duct, the low Pressure is created in the Base region of the enlarged tube, which results in Base drag and hence overall thrust reduced. In this paper Computational Fluid Dynamic (CFD) analysis is used to analyze the effect of secondary air blowing jets called control jets to control Base Pressure in the Base region of the suddenly enlarged duct. These control jets are placed at different Pitch Circle Diameters (PCD) on the Base face of the enlarged pipe. The objective of this work is to increase the Base Pressure up to atmospheric Pressure and hence reduces the Base drag. Mach number 3.0 is considered for analysis. The CFD analysis is done for different combinations of Area Ratios (AR) (2, 5 and 8), Nozzle Pressure Ratios (NPR ) (2, 5 and 8) and PCD (d 1, d 2, and d3. Further analysis is done for different air blowing Pressure ratios (BPR) to optimize air blowing Pressure. The analysis results are plotted for different area ratios, nozzle Pressure ratios, and PCD of control jets. By observing results, it can be concluded that the Base Pressure is strongly influenced by AR, NPR, and PCD of control jets. The air blowing Pressure should be optimum to save energy, and the optimum values can be selected from the results

  • Experimental and numerical investigation of suddenly expanded flow field for supersonic Mach numbers with and without annular cavities
    'Begell House', 2020
    Co-Authors: Quadros, Jaimon Dennis, Khan, Sher Afghan, Prashanth T.
    Abstract:

    The influence of cavities on a suddenly expanded flow field was analyzed. Air flow was passed through a convergent divergent axisymmetric nozzle, and expanded suddenly into a circular parallel shroud with annular cavities. Base Pressure and wall Pressures were measured for combinations of process variables, such as Mach number (M), nozzle Pressure ratio (NPR), area ratio (AR), the length to diameter ratio (L/D) of the enlargement section, and the cavity aspect ratio. The experimental results showed that the Base Pressure fin the suddenly expanded flow field was significantly influenced by annular cavities for low area ratios and high nozzle Pressure ratios. The cavities also yielded a weaker vortex street in the near wake in the vicinity of the nozzle exit, causing a slight increase in the Base Pressure for low Mach numbers. The wall Pressure studies showed that the introduction of cavities generated secondary vortices which reduced the oscillatory nature of the flow along the duct length. The generation of secondary vortices was confirmed by a numerical analysis of the suddenly expanded flow field without and with annular cavities. The two-dimensional coupled implicit Reynolds Averaged Navier-Stokes equations and the two equation standard k-ε turbulence model simulated the process numerically. The governing equations (continuity, momentum, and energy), along with the boundary conditions, were solved by the finite element method. They were flow patterns for various combinations of the process variables demonstrated that there is formation of secondary vortices for flows with annular cavities. Due to the formation of near wake and free shear instability, the vortices of these flows caused the boundary layer to roll up, forming secondary vortices in the suddenly expanded flow field. Immediately following their formation, the vortices underwent a strong three-dimensional distortion

  • Enlarge duct length optimization for suddenly expanded flows
    'Techno-Press', 2020
    Co-Authors: Pathan, Khizer Ahmed, Dabeer, Prakash S, Khan, Sher Afghan
    Abstract:

    In many applications like the aircraft or the rockets/ missiles, the flow from a nozzle needs to be expanded suddenly in an enlarged duct of larger diameter. The enlarged duct is provided after the nozzle to maximize the thrust created by the flow from the nozzle. When the fluid is suddenly expanded in an enlarged duct, the Base Pressure is generally lower than the atmospheric Pressure, which results in Base drag. The objective of this research work is to optimize the length to diameter (L/D) ratio of the enlarged duct using the CFD analysis in the flow field from the supersonic nozzle. The flow from the nozzle drained in an enlarged duct, the thrust, and the Base Pressure are studied. The Mach numbers for the study were 1.5, 2.0, and 2.5. The nozzle Pressure ratios (NPR) of the study were 2, 5, and 8. The L/D ratios of the study were 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Based on the results, it is concluded that the L/D ratio should be increased to an optimum value to reattach the flow to an enlarged duct and to increase the thrust. The supersonic suddenly expanded flow field is wave dominant, and the results cannot be generalized. The optimized L/D ratios for various combinations of flow and geometrical parameters are given in the conclusion section

Sylvain Lardeau - One of the best experts on this subject based on the ideXlab platform.

  • feedback control for form drag reduction on a bluff body with a blunt trailing edge
    Journal of Fluid Mechanics, 2012
    Co-Authors: Jeremy A Dahan, Aimee S Morgans, Sylvain Lardeau
    Abstract:

    The objective of this numerical study is to increase the Base Pressure on a backward-facing step via linear feedback control, to be ultimately translated to a drag reduction on a blunt-Based bluff body. Two backward-facing step cases are simulated: a laminar two-dimensional (2D) flow at a Reynolds number of , and a turbulent three-dimensional (3D) flow at using large-eddy simulation. The control is effected by a full-span slot jet with zero-net-mass-flux, and two jet locations are examined. Linear system identification is performed to characterize the flow response to actuation, used to synthesize a control law. The control strategy is Based on the premise that an attenuation of the instantaneous Pressure fluctuations on the Base of the step should lead to an increase in the time-averaged Base Pressure. Open-loop harmonic forcing is examined within a broad frequency range for both the 2D and 3D flows, which are found to respond differently to actuation. The controllers Based on disturbance attenuation lead to sensible increases in Base Pressure (up to 70 % in 2D and 20 % in 3D) with higher efficiency than the best results achieved in open-loop. The results support the conjecture about the link between the Base Pressure fluctuations and mean, although it is shown that such a black-box model approach is not suitable for optimization without further physical insight.

  • feedback control for form drag reduction on a bluff body with a blunt trailing edge
    Journal of Fluid Mechanics, 2012
    Co-Authors: Jeremy A Dahan, Aimee S Morgans, Sylvain Lardeau
    Abstract:

    The objective of this numerical study is to increase the Base Pressure on a backwardfacing step via linear feedback control, to be ultimately translated to a drag reduction on a blunt-Based bluff body. Two backward-facing step cases are simulated: a laminar two-dimensional (2D) flow at a Reynolds number of Reθ = 280, and a turbulent three-dimensional (3D) flow at Reθ = 1500 using large-eddy simulation. The control is effected by a full-span slot jet with zero-net-mass-flux, and two jet locations are examined. Linear system identification is performed to characterize the flow response to actuation, used to synthesize a control law. The control strategy is Based on the premise that an attenuation of the instantaneous Pressure fluctuations on the Base of the step should lead to an increase in the time-averaged Base Pressure. Open-loop harmonic forcing is examined within a broad frequency range for both the 2D and 3D flows, which are found to respond differently to actuation. The controllers Based on disturbance attenuation lead to sensible increases in Base Pressure (up to 70 % in 2D and 20 % in 3D) with higher efficiency than the best results achieved in open-loop. The results support the conjecture about the link between the Base Pressure fluctuations and mean, although it is shown that such a black-box model approach is not suitable for optimization without further physical insight.

S. A. Kha - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Nozzle Pressure Ratio and Control Jets Location to Control Base Pressure in Suddenly Expanded Flows
    Isfahan University of Technology, 2019
    Co-Authors: K. A. Patha, P. S. Dabee, S. A. Kha
    Abstract:

    In this paper, computational fluid dynamic (CFD) analysis and experiments have been carried out to study the effect of nozzle Pressure ratio, i.e. the ratio of inlet Pressure to atmospheric Pressure, and the pitch circle diameter of the control jets to regulate the Base Pressure. The variables considered for the analysis as well as the experiments are the nozzle Pressure ratio (NPR), the Mach number (M) and the pitch circle diameter (PCD) of the control jets. The area ratio considered for the study is kept constant at 4.84 while the length to diameter (L/D) ratio of an enlarged duct is set constant at 5. The inertia parameter considered for the study is Mach number. The Mach numbers considered for study are 1.5, 2.0, and 2.5. The nozzle Pressure ratio considered for study are 2, 5 and 8. Three different pitch circle diameters of control jets considered for study are 13.1 mm, 16.2 mm and 19.3 mm. From the numerical simulations and the results of the experimental tests, it is found that the control jets are very beneficial to increase the Base Pressure at higher NPR when the jets issuing from the nozzles are under-expanded. The control jets were able to increase the Base Pressure value from 160% to 400% at nozzle Pressure ratio 8. It is concluded that the parameter D3 is the most effective pitch circle diameter of the control jets to increase the Base Pressure

  • Study of Effect of Flow Parameters on Base Pressure in a Suddenly Expanded Duct at Supersonic Mach Number Regimes using CFD and Design of Experiments
    Isfahan University of Technology, 2018
    Co-Authors: J. D. Quadros, S. A. Kha, A. J. Antony
    Abstract:

    Effectiveness of active control of micro jets has been examined by conducting experiments through an abruptly expanded axi-symmetric duct in a view to control Base Pressure. For this purpose, 1mm orifice diameter micro jets have been deployed at an interval of 900 along the exit diameter of the nozzle. The experiments have been conducted by considering three flow parameters at three levels. Mach number (M), length to diameter (L/D) ratio and area ratio (AR) are the three parameters used to conduct and analyze the flow experiments. Base Pressure is considered to be the response variable. The experimentation has been carried out for two cases, i) without active control; ii) with active control. An L9 orthogonal array has been implemented to plan the experiments. It is observed that the control becomes effective for lower area ratios when compared to the higher ones. In addition to this, at high area ratios suction at the Base decreases and hence Base Pressure continuous to diminish with increasing L/D until it reaches a value of L/D=6. The obtained experimental results are subjected to multiple linear regression analysis and Analysis of variance (ANOVA). The performances of the two linear regression models were tested for their prediction accuracy with the help of 15 random test cases. It is observed that, both linear regression models for Base Pressure without and with control are statistically adequate and capable of making accurate predictions. Furthermore, this work also concludes that, Mach number is the most significant factor affecting Base Pressure followed by area ratio and L/D ratio for both cases of experimentation. The obtained experimental results are further validated by CFD analysis and are found to be in good concurrence with each other

  • studies on suddenly expanded flow at different levels of over expansion for area ratio 3 24
    2012
    Co-Authors: Maughal Ahmed Al Aig, S. A. Kha, E Rathakrishna
    Abstract:

    The experiments are carried out to study the effect of different levels of over expansion on Base Pressure in a suddenly expanded axi-symmetric duct. Accordingly the experiments are conducted at two different levels of Over Expansions (I.e. Pe/Pa = 0.277 and 0.56). The area ratio of the present study is 3.24. The jet Mach numbers at the entry to the suddenly expanded duct, studied are 2.2 and 2.58. The length-to-diameter ratio of the suddenly expanded duct is varied from 10 to 1. Active control in the form of four micro jets of 1mm orifice diameter located at 90 0 intervals along a pitch circle diameter of 1.3 times the nozzle exit diameter in the Base region are employed. In addition to Base Pressure, wall Pressure field along the duct is also studied. From the present studies it is found that at a high level of over expansion micro jets are not effective. Further, it is found from wall Pressure studies that the micro jets do not disturb the flow field in the enlarged duct. Index Terms-Active Control, over expanded jet, Wall Pressure distribution, Base Pressure

  • Base Pressure studies from over expanded nozzle for area ratio 2 56
    2012
    Co-Authors: Maughal Ahmed Al Aig, S. A. Kha, E Rathakrishna
    Abstract:

    The present paper aims at study of variations in Base Pressure at different levels of over expansion of jet in a suddenly expanded axi-symmetric duct. The results of an experimental investigation carried out at two different fixed levels of Over Expansion namely 0.277 and 0.56 are compared. The area ratio of the present study is 2.56. The jet Mach numbers at the entry to the suddenly expanded duct, studied are 2.2 and 2.58. The length-to-diameter ratio of the suddenly expanded duct is varied from 10 to 1. Active control in the form of four micro jets of 1mm orifice diameter located at 900 intervals along a pitch circle diameter of 1.3 times the nozzle exit diameter in the Base region are employed. In addition to Base Pressure, wall Pressure field along the duct is also studied. From the present studies it is found that at a high level of over expansion micro jets are marginally effective. It is also found from wall Pressure studies that the micro jets do not disturb the flow field in the enlarged duct.

  • active control of Base Pressure in suddenly expanded flow for area ratio 4 84
    2012
    Co-Authors: Ahmed Ali Aig, S. A. Kha, E Rathakrishna
    Abstract:

    Airflow from convergent-divergent axi-symmetric nozzles expanded suddenly into circular duct of larger cross-sectional area than that of nozzle exit area are studied experimentally, focusing attention on the Base Pressure and the flow development in the enlarged duct. Micro-jets of 1 mm orifice diameter located at 90 0 intervals along a pitch circle diameter (pcd) 1.3 times the nozzle exit diameter were employed as the controller of the Base Pressure. The tests are conducted for Mach numbers 1.87, 2.2 and 2.58. The area ratio of the present study is 4.84. The length-to-diameter ratio of the suddenly expanded duct is varied from 10 to 1 and nozzle Pressure ratio (NPR) in the range 3 to 11. It is found that the active control in the form of blowing through small orifices (micro jets) are effective in controlling the Base Pressure field and even do not augment the flow field in the duct. An increase of 45 percent in Base Pressure was achieved for certain combination of parameters of the present study.

Antony A J - One of the best experts on this subject based on the ideXlab platform.

  • Study of Base Pressure behavior in a suddenly expanded duct at supersonic mach number regimes using statistical analysis
    'Czestochowa University of Technology', 2018
    Co-Authors: Quadros, Jaimo Dennis, Khan, She Afgha, Antony A J
    Abstract:

    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 the 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

  • Base Pressure behaviour in a suddenly expanded duct at supersonic mach number regimes using Taguchi design of experiments
    Technical University of Lodz, 2018
    Co-Authors: Quadros, Jaimo Dennis, Khan, She Afgha, Antony A J
    Abstract:

    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 influential parameter affecting Base Pressure followed by NPR and L/D

  • Predictive modeling of suddenly expanded flow process in the Supersonic Mach number regime using response surface methodology
    Institute of Institutional Industrial Research, 2017
    Co-Authors: Quadros, Jaimo Dennis, Khan, She Afgha, Antony A J
    Abstract:

    The present work uses design of experiments (DOE) technique along with response surface methodology to develop linear models, to establish linear input-output relationships in a suddenly expanded flow process. Mach number (M), nozzle Pressure ratio (NPR), area ratio (AR) and length to diameter (L/D) ratio have been considered as the input parameters, which controls the output (i.e. Base Pressure). Full factorial DOE has been implemented for developing the linear model. Experiments were conducted to measure Base Pressure by two means i.e. without control (WoC) and with the use of active control (WC). The adequacy of developed models was checked through statistical analysis. Fifteen random test cases were conducted in order to validate the models. It is observed that, both linear regression models for Base Pressure without and with control are statistically adequate and capable of making accurate predictions

  • Investigation of effect of process parameters on suddenly expanded flows through an axi-symmetric nozzle for different Mach numbers using design of experiments
    IOP Publishing, 2017
    Co-Authors: Quadros, Jaimo Dennis, Khan, She Afgha, Antony A J
    Abstract:

    Experiments are conducted to determine Base Pressure variation through micro-jets from a suddenly expanded axisymmetric passage. Four micro-jets having an orifice diameter of 1mm are situated at 900 interims along the Base at 6.5 mm from the geometrical axis of the main jet. The Mach number and L/D ratios were the process parameters employed in the study. The flow stream was extended all of a sudden into an axi-symmetric duct of 4.84 cross-sectional area for all the Mach numbers and L/D ratios respectively. The test Mach numbers used in the study was 2, 2.5 and 3; length-to-diameter ratios selected for the sudden expansion tube were 4, 6 and 8. The jets were operated at an overexpansion level of (Pe/Pa = 0.277). The experiments are conducted as per Taguchi design of experiments. From this investigation, one will be able to identify the enlargement length to diameter ratio resulting in maximum increasing or decreasing Base Pressure. Mathematical models are also developed for Base Pressure Based on Mach number and L/D ratio with a maximum error of ± 10%