Experimental Investigation of Flow Instability in a Supersonic Inlet

2010 ◽  
Author(s):  
Mohammad Reza Soltani ◽  
Mohammad Farahani
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Instability ◽  
Wind Tunnel Test ◽  
External Flow ◽  
Pressure Data ◽  
Supersonic Inlet ◽  
Shock Oscillation

An extensive wind tunnel test series were conducted on an axisymmetric supersonic inlet. The model was tested at Mach numbers from 1.8 to 2.2 and at different values of mass flow rate. Shadowgraph flow visualization was used to capture the external shock structure in front of the inlet. The goal of this study is to find out the general characteristics of the inlet buzz. Frequencies of the buzz have been achieved from the analysis of the pressure data as well as the shadowgraph pictures. The amplitude of the shock waves motion has been measured from the visualization pictures too. In the some large value of mass flow rate, the frequency of shock oscillation increased versus Mach number. Also in each Mach number due to the mass flow rate decrement, the buzz frequency decreases and its amplitude increases conversely. Also buzz instability affects the external flow by the same frequency of the internal one.

scholarly journals Centrifugal Compressor Stall Control by the Application of Engineered Surface Roughness on Diffuser Shroud Using Numerical Simulations

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2033
Author(s):  
Amjid Khan ◽  
Muhammad Irfan ◽  
Usama Muhammad Niazi ◽  
Imran Shah ◽  
Stanislaw Legutko ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Control Method ◽  
Flow Instability ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Low Mass

Downsizing in engine size is pushing the automotive industry to operate compressors at low mass flow rate. However, the operation of turbocharger centrifugal compressor at low mass flow rate leads to fluid flow instabilities such as stall. To reduce flow instability, surface roughness is employed as a passive flow control method. This paper evaluates the effect of surface roughness on a turbocharger centrifugal compressor performance. A realistic validation of SRV2-O compressor stage designed and developed by German Aerospace Center (DLR) is achieved from comparison with the experimental data. In the first part, numerical simulations have been performed from stall to choke to study the overall performance variation at design conditions: 2.55 kg/s mass flow rate and rotational speed of 50,000 rpm. In second part, surface roughness of magnitude range 0–200 μm has been applied on the diffuser shroud to control flow instability. It was found that completely rough regime showed effective quantitative results in controlling stall phenomena, which results in increases of operating range from 16% to 18% and stall margin from 5.62% to 7.98%. Surface roughness as a passive flow control method to reduce flow instability in the diffuser section is the novelty of this research. Keeping in view the effects of surface roughness, it will help the turbocharger manufacturers to reduce the flow instabilities in the compressor with ease and improve the overall performance.

scholarly journals Comparison of Swing and Tilting Check Valves Flowing Compressible Fluids

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 758
Author(s):  
Zhi-xin Gao ◽  
Ping Liu ◽  
Yang Yue ◽  
Jun-ye Li ◽  
Hui Wu
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Check Valve ◽  
Small Mass ◽  
Working Fluid ◽  
Valve Disc ◽  
Valve Opening ◽  
The Difference

Although check valves have attracted a lot of attention, work has rarely been completed done when there is a compressible working fluid. In this paper, the swing check valve and the tilting check valve flowing high-temperature compressible water vapor are compared. The maximum Mach number under small valve openings, the dynamic opening time, and the hydrodynamic moment acting on the valve disc are chosen to evaluate the difference between the two types of check valves. Results show that the maximum Mach number increases with the decrease in the valve opening and the increase in the mass flow rate, and the Mach number and the pressure difference in the tilting check valve are higher. In the swing check valve, the hydrodynamic moment is higher and the valve opening time is shorter. Furthermore, the valve disc is more stable for the swing check valve, and there is a periodical oscillation of the valve disc in the tilting check valve under a small mass flow rate.

Performance study of an inlet in supersonic flow

2012 ◽  
Vol 227 (1) ◽  
pp. 159-174 ◽  
Author(s):  
Mohammad R Soltani ◽  
Mohammad Farahani
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Free Stream ◽  
Characteristic Curve ◽  
Pressure Recovery ◽  
Internal Boundary ◽  
Performance Study ◽  
Free Stream Mach Number

The performance characteristics of an axisymmetric inlet at its design and off-design operational conditions are experimentally investigated. The model is tested for wide ranges of free stream Mach numbers, M∞ = 1.5–2.5, and mass flow rates. For each test, the pressure recovery, the mass flow passing through the inlet and the pressure distribution over the spike and the cowl are measured. In addition, the shock wave formed in front of the inlet is visualized. The characteristic curve of the inlet is then obtained for each free stream Mach number. As the Mach number is increased, the pressure recovery is reduced, but the maximum value of the mass flow rate grows up. Variations of the mass flow affect the surface pressure over both the front portion of the cowl and the entire surface of the spike. Further, it has changed both pressure and Mach number at the end of the diffuser, which would consequently affect the performance of the propulsion system. In addition, contrary to the internal boundary layer, the external one far from the cowl lip has been found to be almost independent of the inlet mass flow rate for a constant free stream Mach number.

scholarly journals Analysis and Development of Restrictor for Parallel Twin Engine in FSAE Cars

2018 ◽  
Vol 7 (3.6) ◽  
pp. 311 ◽  
Author(s):  
M Vignesh Kumar ◽  
Sivanesan Murugesan
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Software Tool ◽  
Ansys Fluent ◽  
Formula Sae ◽  
Standard Design ◽  
Fluent Software ◽  
Convergence And Divergence

This research aims to the development of intake restrictor of a formula SAE car engine which is of 300cc parallel twin cylinder engine. In this paper we have considered different venturi designs which have different convergence and divergence angles. The main aim is to optimize the pressure and velocity of air which tends to offer better combustion reflects in performance. The parameters which are to be considered for design as well as analysis are mach number, intake velocity, mass flow rate, etc.., To perform this research we have chosen the Ansys fluent software tool and the analytical calculations were made for standard design. It is observed that the continuous variations in converging and diverging angles offers better results in both pressure and velocity characteristics of air entering for combustion. 

scholarly journals Development of a Flowmeter Using Vibration Interaction between Gauge Plate and External Flow Analyzed by LSTM

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5922
Author(s):  
Jie Jin ◽  
Youngbeen Chung ◽  
Junhong Park
Keyword(s):  
Neural Network ◽  
Fourier Transform ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Short Term Memory ◽  
External Flow ◽  
Information Measurement ◽  
Flow Information ◽  
Vibration Responses

(1) Background: This study is aimed at the development of a precise and inexpensive device for flow information measurement for external flow. This novel flowmeter uses an LSTM (long short-term memory) neural network algorithm to analyze the vibration responses of the gauge plate. (2) Methods: A signal processing method using an LSTM neural network is proposed for the development of mass flow rate estimation by sensing the vibration responses of a gauge plate. An FFT (fast Fourier transform) and an STFT (short-time Fourier transform) were used to analyze the vibration characteristics of the gauge plate depending on the mass flow rate. For precise measurements, the vibration level and roughness were computed and used as input features. The actual mass flow rate measured by using a weight transducer was employed as the output features for the LSTM prediction model. (3) Results: The estimated flow rate matched the actual measured mass flow rate very closely. The deviations in measurements for the total mass flow were less than 6%. (4) Conclusions: The estimation of the mass flow rate for external flow through the proposed flowmeter by use of vibration responses analyzed by the LSTM neural network was proposed and verified.

Design and aerodynamic performance analysis of a variable geometry axisymmetric inlet for TBCC

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yunfei Wang ◽  
Huacheng Yuan ◽  
Jinsheng Zhang ◽  
Zhenggui Zhou
Keyword(s):  
Mach Number ◽  
Performance Analysis ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Design Method ◽  
Aerodynamic Performance ◽  
Combined Cycle ◽  
Variable Geometry

Abstract Design and aerodynamic performance analysis of a variable geometry axisymmetric inlet was carried out for tandem scheme turbine-based combined cycle (TBCC) propulsion system. The operation Mach number of the inlet was between 0 and 4. The design point was chosen as Mach number 4.0 in this paper. The determination of external and internal compression and the design method of annular to circle diffuser were illustrated. The inlet was unstart under Ma 3.0 without adjustment. Then, a variable scheme was designed to ensure self-start of the inlet and match the requirement of mass flow rate during the whole flight envelope. And four supports were used to fix the spike. According to the 3D numerical simulations, the total pressure recovery was 0.52 at Ma 4.0 at critical condition and the mass flow rate was consistent with the requirement at different flight Mach number.

Numerical Investigation of Diffuser Rotating Stall and System Instability in a Centrifugal Compressor With Vaned Diffuser

2018 ◽  
Author(s):  
Yang Zhao ◽  
Guang Xi ◽  
Jiayi Zhao
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Flow Instability ◽  
Leading Edge ◽  
Rotating Stall ◽  
Vaned Diffuser ◽  
Corner Separation ◽  
Lumped Parameter

The operating range of a centrifugal compressor is often limited by the occurrence of the flow instability, such as diffuser rotating stall or system surge. In the paper, the unsteady numerical simulations are performed on a low-speed centrifugal compressor to investigate the characteristic of the rotating stall in the vaned diffuser. And also, the developed model of lumped parameter is used to predict the system instability. The flow field in the diffuser is firstly investigated at near stall condition. It is found that the leading-edge vortex and the secondary flow induce the hub-corner separation at the suction side of the diffuser blade. When the mass flow rate is reduced gradually, the fore part of the volute turns to act as a diffuser from a nozzle. Under the influence of the asymmetry induced by the volute, the hub-corner separation firstly develops into rotating stall in the passage with the lowest mass flow rate when at critical stall point. And then the diffuser rotating stall propagates along the circumferential direction at about 7% of the impeller speed. And also, the model of lumped parameter considering the effect of rotating stall is developed to analyze the system instability of mild surge. The predicted vibration frequency is within 5.8% of the measurement and the predicted transient process in mild surge matches well with the measurement. With different volume of the compressed air, the transient compressor characteristic tends to be stabilized or oscillates in a cycle along the counter-clockwise with different magnitude.

An experimental study of compressible combining flow at 45° T-junctions

2014 ◽  
Vol 229 (9) ◽  
pp. 1600-1610 ◽  
Author(s):  
Wenhui Wang ◽  
Zhenhua Lu ◽  
Kangyao Deng ◽  
Shuan Qu
Keyword(s):  
Experimental Study ◽  
Mach Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Measurement Data ◽  
Junction Flow ◽  
Wide Range ◽  
Loss Coefficients

Junction flow loss is one of the sources of flow losses in many engineering pipe systems. An experimental study was carried out in order to investigate the combining steady pressure loss coefficients at 45° T-junctions with three area ratios between lateral branch and main duct. Extensive measurement data were obtained at a wide range of Mach number (0.1–0.6) and mass flow rate ratios using air as the tested fluid. Comparative analysis of the results includes the pressure difference in the two flow paths of the junction, the effect of Mach number in common branch due to gas compressibility, as well as the loss coefficients with various geometry condition. The following conclusion is drawn: the total pressure loss coefficient ( K) was mainly dependent on the Mach number ( M3), mass flow rate ratio ( q), and area ratio ( a), while almost independent on Reynolds number. The results provide reference for the research of junction flow and can be valuable in the correction of the boundary condition in one-dimensional simulation models.

Numerical Study of Supersonic Film Cooling in Diverging Section of Nuclear Rocket Laval Nozzle

2018 ◽  
Author(s):  
Xiaokai Sun ◽  
Ping Ye ◽  
Peixue Jiang ◽  
Wei Peng ◽  
Jie Wang
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Film Cooling ◽  
Laval Nozzle ◽  
Numerical Study ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Nuclear Rocket

Nuclear rockets with specific impulse have obvious advantages by greatly reducing the mass of the propellant and potentially decreasing the cost of launching material from the earth’s surface. Nuclear thermal rockets use hydrogen propellant with coolant exit temperature of near 3000 K, which is very high, so the cooling of airframe surfaces in the vicinity of the exhaust is needed, of which film cooling is an effective method. Most of previous studies mainly focus on the film cooling effectiveness using two dimensional backward-facing step model, however, the nuclear rocket exhaust using the converging-diverging Laval nozzle, so the film cooling would be different. The present study numerically investigated the influence of coolant Mach number, coolant inlet height on supersonic film cooling in the diverging section of Laval nozzle, while keeping the coolant mass flow rate constant, with the results showing that: increasing the coolant inlet Mach number and the coolant inlet height can increase the film cooling effectiveness; for the same coolant mass flow rate, reducing the coolant inlet height and increasing the inlet Mach number improves film cooling effectiveness.

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