Performance of a jaws inlet under off-design conditions

2016 ◽  
Vol 231 (2) ◽  
pp. 294-305 ◽  
Author(s):  
Tianlai Gu ◽  
Shuai Zhang ◽  
Yao Zheng
Keyword(s):  
Mach Number ◽  
Flow Fields ◽  
Back Pressure ◽  
Low Mach Number ◽  
Mass Capture ◽  
Constant Area ◽  
Flow Capture ◽  
Mach Numbers ◽  
High Mach ◽  
Better Than

Numerical analysis was conducted of a jaws inlet under different working conditions, including angles of attack of 0° and 3°, varying Mach number, and varying back pressure with a constant-area isolator, to investigate its performance and flow fields of starting and unstarting states. Results reveal that the jaws inlet has an enhanced flow capture capability in starting states, with the mass capture ratio higher than 0.96, but relatively reduced working range of inflow Mach numbers. Its performance at a low Mach number is better than that at a high Mach number. Non-uniform flow fields are observed in unstarting cases at low Mach numbers and high back pressures, while separation structures are confined in the pitching compression section. Further increase in Mach number or decrease in back pressure does not result in significant changes in the separation structures. In the unstarting case under a high back pressure, it is hard to achieve restarting through reductions in the back pressure.

Heat Transfer in Rotating Serpentine Coolant Passage With Ribbed Walls at Low Mach Numbers

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Shang-Feng Yang ◽  
Je-Chin Han ◽  
Salam Azad ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Low Mach Number ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers ◽  
Wide Range ◽  
Mach Numbers

This paper experimentally investigates the effect of rotation on heat transfer in typical turbine blade serpentine coolant passage with ribbed walls at low Mach numbers. To achieve the low Mach number (around 0.01) condition, pressurized Freon R-134a vapor is utilized as the working fluid. The flow in the first passage is radial outward, after the 180 deg tip turn the flow is radial inward to the second passage, and after the 180 deg hub turn the flow is radial outward to the third passage. The effects of rotation on the heat transfer coefficients were investigated at rotation numbers up to 0.6 and Reynolds numbers from 30,000 to 70,000. Heat transfer coefficients were measured using the thermocouples-copper-plate-heater regional average method. Heat transfer results are obtained over a wide range of Reynolds numbers and rotation numbers. An increase in heat transfer rates due to rotation is observed in radially outward passes; a reduction in heat transfer rate is observed in the radially inward pass. Regional heat transfer coefficients are correlated with Reynolds numbers for nonrotation and with rotation numbers for rotating condition, respectively. The results can be useful for understanding real rotor blade coolant passage heat transfer under low Mach number, medium–high Reynolds number, and high rotation number conditions.

Relation Between Sound Sources and Vortical Structures in Isotropic Compressible Turbulence

2014 ◽  
Author(s):  
Daiki Terakado ◽  
Taku Nonomura ◽  
Makoto Sato ◽  
Kozo Fujii
Keyword(s):  
Mach Number ◽  
Sound Source ◽  
Compressible Turbulence ◽  
Fine Scale ◽  
Sound Sources ◽  
Vortical Structures ◽  
Scale Structures ◽  
Mach Numbers ◽  
High Mach ◽  
Lighthill Equation

We investigate the relation between vortical structures and sound source in isotropic compressible turbulence by direct numerical simulations with various turbulent Mach numbers. The sound source is obtained numerically from the Lighthill equation. As a first step, we study the sound source from the Reynolds stress, which is the dominant source in flows at low Mach numbers. We investigate, especially, sound source structures around the “coherent fine scale eddies” [1–4] to lead a universal conclusion of sound generation mechanism from the fine scale structures in supersonic flows. We find that the sound source structures around the coherent fine scale eddies show some distorted structures only in high Mach number flows because shocklets appear around the fine scale eddies in those flows. This change in sound source structures around the coherent fine scale eddies does not appear in low and moderate Mach number cases.

Compressibility effects in a turbulent annular mixing layer. Part 1. Turbulence and growth rate

2000 ◽  
Vol 421 ◽  
pp. 229-267 ◽  
Author(s):  
JONATHAN B. FREUND ◽  
SANJIVA K. LELE ◽  
PARVIZ MOIN
Keyword(s):  
Growth Rate ◽  
Mach Number ◽  
Mixing Layer ◽  
Mixing Layers ◽  
Velocity Difference ◽  
Mean Velocity ◽  
The Mean ◽  
Mach Numbers ◽  
High Mach ◽  
Compressibility Effects

This work uses direct numerical simulations of time evolving annular mixing layers, which correspond to the early development of round jets, to study compressibility effects on turbulence in free shear flows. Nine cases were considered with convective Mach numbers ranging from Mc = 0.1 to 1.8 and turbulence Mach numbers reaching as high as Mt = 0.8.Growth rates of the simulated mixing layers are suppressed with increasing Mach number as observed experimentally. Also in accord with experiments, the mean velocity difference across the layer is found to be inadequate for scaling most turbulence statistics. An alternative scaling based on the mean velocity difference across a typical large eddy, whose dimension is determined by two-point spatial correlations, is proposed and validated. Analysis of the budget of the streamwise component of Reynolds stress shows how the new scaling is linked to the observed growth rate suppression. Dilatational contributions to the budget of turbulent kinetic energy are found to increase rapidly with Mach number, but remain small even at Mc = 1.8 despite the fact that shocklets are found at high Mach numbers. Flow visualizations show that at low Mach numbers the mixing region is dominated by large azimuthally correlated rollers whereas at high Mach numbers the flow is dominated by small streamwise oriented structures. An acoustic timescale limitation for supersonically deforming eddies is found to be consistent with the observations and scalings and is offered as a possible explanation for the decrease in transverse lengthscale.

Design and Numerical Investigations on a Dual-Duct Variable Geometry RBCC Inlet

2020 ◽  
Vol 37 (2) ◽  
pp. 111-122 ◽  
Author(s):  
Xiaowei Liu ◽  
Lei Shil ◽  
Peijin Liu ◽  
Fei Qin ◽  
Guoqiang He
Keyword(s):  
Combined Cycle ◽  
High Mass ◽  
Variable Geometry ◽  
Status Transition ◽  
Flight Range ◽  
Operational Window ◽  
Mass Capture ◽  
Temperature Environment ◽  
Mach Numbers ◽  
High Mach

AbstractA widely applicable and variable geometry 2-D rocket based combined cycle (RBCC) inlet characterized by the dual-duct design is conceptually put forward. The inlet operates as dual-duct status in the low Mach range (0~4), and transits to single-flowpath status in the following high Mach range (4~7). It accomplishes operational status transition through an 8.0-degree ramp rotation and a 4.0-degree cowl rotation at Mach 4. Through numerical simulations on typical flight Mach numbers, the observed starting Mach number is 2.2, which provides a sufficient operational window for a smooth ejector-to-ramjet mode transition. The RBCC inlet achieves comprehensive high mass capture coefficients in the overall wide flight range, especially in the low speed regimes. Suitable Mach numbers satisfying various combustion requirements in different modes together with high total pressure recovery coefficients are also obtained since the physical throat areas, compression angles, and the corresponding contraction ratios can be adjusted by a large margin through very limited rotations. The variable geometry scheme is not only feasible for practical realizations, but is also simple to arrange the dynamic sealing issues in a low-temperature environment in the RBCC engine.

scholarly journals Prediction of total pressure characteristics in the settling chamber of a supersonic blowdown wind tunnel

2011 ◽  
Vol 115 (1171) ◽  
pp. 557-566 ◽  
Author(s):  
G. K. Suryanarayana ◽  
S. R. Bhoi
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Storage Tank ◽  
Stagnation Pressure ◽  
Rate Of Change ◽  
Settling Chamber ◽  
Low Mach Number ◽  
High Mach ◽  
And Storage ◽  
Pressure Characteristics

Abstract Occurrence of transient starting and stopping loads during tests at high Mach numbers is one of the major problems in intermittent blowdown wind tunnels. It is believed that in order to overcome this problem, the wind tunnel could be started at a low Mach number and low stagnation pressure; the desired high Mach number condition could be reached by continuously changing the nozzle contour while synchronously increasing the stagnation pressure. After completing the tests, the nozzle could be brought back to the initial low Mach number accompanied by synchronous decrease in the stagnation pressure. In such a scenario, it is important to ensure that the pressure regulating valve (PRV) of the wind tunnel delivers and maintains a specified minimum stagnation pressure at any Mach number, so that supersonic breakdown of the test section flow does not occur. In this paper, the problem is formulated based on quasi-steady one-dimensional isentropic equations and numerically solved to predict the time histories of settling chamber pressure and storage tank pressure for a given trajectory of the opening of the PRV, as the Mach number is changed from Mach 1 to 4·0 continuously in four seconds and vice versa. The effects of rate of change of PRV open area and rate of change of Mach number on the stagnation pressure characteristics in the settling chamber and storage tank are predicted. The measured trajectories of the PRV in experiments in the NAL 0·6m transonic wind tunnel are used as input to the prediction program to validate the methodology. Predictions indicate that when the nozzle throat is changed from Mach 1 to 4 in four seconds, the settling chamber stagnation pressure rapidly builds up and approaches the pressure in the storage tank. Predictions show an alarming rise in free stream dynamic pressure during transition from Mach 1 to 4 and vice versa, which needs to be verified through measurements.

Sweep Effects on Fan-Intake Aerodynamics at High Angle of Attack

2021 ◽  
Author(s):  
Ben Mohankumar ◽  
Cesare A. Hall ◽  
Mark J. Wilson
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Angle Of Attack ◽  
Pressure Rise ◽  
Low Pressure ◽  
Rotating Stall ◽  
High Angle ◽  
High Angle Of Attack ◽  
Mach Numbers ◽  
High Mach

Abstract Sweep in a transonic fan is conventionally used to reduce design point losses by inclining the passage shock relative to the incoming flow. However, future low pressure ratio fans operate to lower Mach numbers meaning the role of sweep at cruise is diminished. Instead, sweep might be repurposed to improve the performance of critical high Mach number off-design conditions such as high angle of attack (AOA). In this paper, we use unsteady computational fluid dynamics to compare two transonic low pressure ratio fans, one radially stacked and one highly swept, coupled to a short intake design, at the high AOA flight condition. The AOA considered is 35°, which is sufficient to separate the intake bottom lip. The midspan of the swept fan was shifted upstream to add positive sweep to the outer span. Based on previous design experience, it was hypothesised the swept fan would reduce transonic losses when operating at high AOA. However, it was found the swept fan increased the rotor loss by 24% relative to the radial fan. Loss was increased through two key mechanisms. i) Rotor choking: flow is redistributed around the intake separation and enters the rotor midspan with high Mach numbers. Sweeping the fan upstream reduced the effective intake length, which increased the inlet relative Mach number and amplified choking losses. ii): Rotor-separation interaction (RSI): the rotor tip experiences low mass flow inside the separation, which increases the pressure rise across the casing to a point where the boundary layer separates. The swept fan diffused the casing streamtube, causing the casing separation to increase in size and persist in the passage for longer. High RSI loss indicated the swept fan was operating closer to the rotating stall point.

Design Point Efficiency of Radial Turbines

2018 ◽  
Author(s):  
Graham D. Cox
Keyword(s):  
Mach Number ◽  
Numerical Solutions ◽  
Flow Coefficient ◽  
Speed Ratio ◽  
Low Mach Number ◽  
High Mach Number ◽  
Specific Speed ◽  
High Mach ◽  
Nozzle Guide ◽  
New Applications

Results are presented from CFD calculations on a large database of 3D, radially-stacked, radial turbine geometries. The database covers a comprehensive range of basic geometrical features allowing the most appropriate geometry to be selected for optimum efficiency over extensive ranges of blade-speed-ratio, flow coefficient and specific speed. Initial studies considered the wheel only and used 78 geometries for low Mach number applications and 102 geometries for high Mach number applications. Each was run over a range of blade-speed-ratios and inlet flow angles to generate preliminary results. Designs that did not contribute to the optimum efficiency trends were discarded. The remaining 17 low Mach number and 24 High Mach number wheels were recalculated with a range of nozzle guide vanes and back-face cavities to provide increased fidelity numerical solutions. The calculated optimum efficiency is presented on charts of blade-speed-ratio against flow coefficient, against specific speed and against non-dimensional mass-flow. The effect of exducer trim reduction, as often required for mechanical reasons, is demonstrated. The charts can be used for preliminary design of new applications.

High Inlet Relative Mach Number Centrifugal Compressor Impeller Design

2007 ◽  
Author(s):  
James M. Sorokes ◽  
Jason A. Kopko
Keyword(s):  
Mach Number ◽  
Test Data ◽  
Centrifugal Compressor ◽  
High Mach Number ◽  
Performance Map ◽  
Compressor Impeller ◽  
The Subject ◽  
Mach Numbers ◽  
High Mach

This document presents an overview of impeller inlet relative Mach number, how the parameter is calculated, and its importance as an indicator of impeller performance. Comments are also offered regarding the comparison of inlet relative Mach numbers obtained from different compressor vendors. A sample impeller is used to illustrate the various methods used to calculate the inlet relative Mach number. Test data for that impeller is also offered to indicate the performance map achievable with high Mach number designs. Please note that this document is not intended to be an all-inclusive treatment of the subject; rather, it summarizes the OEM’s methodologies and perspective.

Design and validation of a two-dimensional variable geometry inlet

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Huacheng Yuan ◽  
Yunfei Wang ◽  
Jun Liu ◽  
Zhengxu Hua
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Back Pressure ◽  
Variable Geometry ◽  
Two Dimensional ◽  
Validation Experiment ◽  
Mach Numbers ◽  
Dimensional Variable

Abstract The design of a two-dimensional variable geometry inlet which applied to a tandem type turbine-based combined cycle (TBCC) propulsion system was investigated in the present paper through three-dimensional simulations and wind tunnel tests. The operation Mach number range was between 0 and 3. A multi-ramp geometry scheme was adopted to achieve acceptable performance at different inflow Mach number. The first ramp angle was fixed whilst the angles of the second and the third ramps were variable at different inflow Mach numbers. The Mach numbers at throat region were maintained between 1.3 and 1.5 at different inflow Mach numbers according to this variable geometry scheme. A fixed geometry rectangular-to-circular shape diffuser was adopted to improve aerodynamic performance of the inlet. Three-dimensional numerical simulations were carried out between Ma1.5 and Ma3.0. The results indicated that good aerodynamic performance can be achieved at different inflow speed. At the design point, total pressure recovery of the inlet was 0.66 at critical condition. Wind tunnel validation experiment tests were conducted at Ma2.0, showing the movement of terminal shock wave from downstream to upstream as the back pressure increased. The inlet operated at supercritical, critical and subsonic conditions at different back pressure.

Axial Flow Compressor and Turbine Loss Coefficients: A Comparison of Several Parameters

1972 ◽  
Vol 94 (3) ◽  
pp. 193-201 ◽  
Author(s):  
L. E. Brown
Keyword(s):  
Mach Number ◽  
Test Data ◽  
Axial Flow ◽  
Loss Coefficient ◽  
Low Mach Number ◽  
Loss Parameter ◽  
Loss Coefficients ◽  
Flow Compressor ◽  
Stage Efficiency ◽  
Better Than

Many loss parameters are used in the turbomachinery field for correlating the effects on losses of numerous geometric and aerodynamic variables associated with blade rows. The parameter most common to these correlations is the ratio of a loss parameter to a velocity parameter, here called the loss coefficient. Such loss coefficients of different forms used for compressors by Howell and the NACA and those used for turbines by Ainley and Soderberg, plus an additional one, are compared explicitly for possible use in both compressors and turbines. Over a range of Mach numbers, loss coefficient values are compared with loss levels fixed and for representative blading cascade test data, and pressure recoveries and stage efficiencies are compared with loss coefficient values fixed. It is shown that for a low Mach number the different parameters are equal and interchangeable; however, as the Mach number increases, differences appear and grow larger, so that a given combination of loss coefficient value and Mach number implies different entropy-rise values depending upon which parameter is being used. The criteria used here for comparing the different parameters are that one loss coefficient is better than another a– if its loss coefficient values corresponding to test data vary less over a significant range of Mach number, and b– if the stage efficiency implied by a fixed loss coefficient value varies in a more realistic way over a range of Mach number. The Soderberg parameter was found to be better for both compressors and turbines than the other loss coefficients investigated.

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