scholarly journals 0144 Improvement of the probe for simultaneous measurement of velocity and static pressure fluctuations and its application to measurement of plane jet

2009 ◽  
Vol 2009 (0) ◽  
pp. 89-90
Author(s):  
Yuki KOJIMA ◽  
Kouji NAGATA ◽  
Yasuhiko SAKAI ◽  
Takashi KUBO
Keyword(s):  
Simultaneous Measurement ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Plane Jet

Exploring Applicability of Acoustic Heat Transfer Enhancement Across Various Perturbation Elements

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Tapish Agarwal ◽  
Maximilian Stratmann ◽  
Simon Julius ◽  
Beni Cukurel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Acoustic Excitation ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Number Range ◽  
Flow Modulation ◽  
Spatially Resolved

Abstract The requirements of improved heat transfer performance on turbine surfaces and internal cooling passages drive the research into exploring new methods for efficiency enhancements. The addition of ribbed structures inside the cooling ducts has proven to be most practical, which increases heat transfer from surfaces to fluid flow at the cost of some pressure loss. Many active and passive methods have been proposed for enhancing the heat transfer, where acoustic excitation has been recently shown to be an effective option. Moreover, the existing pressure fluctuations due to rotor–stator interactions can also be utilized as a source of excitation. However, the sensitivity of the phenomenon to various flow and geometric parameters has not been fully characterized. The present study investigates various aspects of convective heat transfer enhancement and turbulent flow modulation caused by acoustic forcing on separating and reattaching flow over isolated rib obstacles. A parametric study is conducted; rib obstacles of various sizes and shapes (including rectangular, squared, triangular, and semi-cylindrical) are installed in a low-speed, fully turbulent wind tunnel, and measurements are taken at different velocities and excitation frequencies. Static pressure and spatially resolved surface temperature measurements are performed to quantify the ramifications of acoustic excitation on the wetted wall. Within the favorable Strouhal number range of 0.1–0.25, an optimum value of 0.16 is observed. It is shown that triangular ribs are more prone to acoustic heat transfer enhancement than rectangular or cylindrical perturbations. A linear correlation between static pressure recovery rate and acoustic heat transfer enhancement is observed, which is invariant to change in size/shape of the rib as well as flow and excitation parameters.

Design of a Transonic High-Pressure Turbine Stage 2D Section With Reduced Rotor/Stator Interaction

2004 ◽  
Author(s):  
Michele Vascellari ◽  
Re´my De´nos ◽  
Rene´ Van den Braembussche
Keyword(s):  
Rotor Blade ◽  
Static Pressure ◽  
Aerodynamic Force ◽  
Pressure Fluctuations ◽  
Uniform Field ◽  
Turbine Stage ◽  
Rotor Stator Interaction ◽  
Transonic Turbine ◽  
Blade Failure ◽  
Rotor Profiles

In transonic turbine stages, the exit static pressure field of the vane is highly non-uniform in the pitchwise direction. The rotor traverses periodically this non-uniform field and large static pressure fluctuations are observed around the rotor section. As a consequence the rotor blade is submitted to significant variations of its aerodynamic force. This contributes to the high cycle fatigue and may result in unexpected blade failure. In this paper an existing transonic turbine stage section is redesigned in the view of reducing the rotor stator interaction, and in particular the unsteady rotor blade forcing. The first step is the redesign of the stator blade profile to reduce the stator exit pitchwise static pressure gradient. For this purpose, a procedure using a genetic algorithm and an artificial neural network is used. Next, two new rotor profiles are designed and analysed with a quasi 3D Euler unsteady solver in order to investigate their receptivity to the shock interaction. One of the new profiles allows reducing the blade force variation by 50%.

The Development of Extremely-Compact Static Pressure Probe for the Simultaneous Measurement of Pressure and Velocity in the Turbulent Flows

2011 ◽  
Author(s):  
Kazuhiro Onishi ◽  
Osamu Terashima ◽  
Yasuhiko Sakai ◽  
Kouji Nagata
Keyword(s):  
Turbulent Flows ◽  
Simultaneous Measurement ◽  
Measurement Accuracy ◽  
Static Pressure ◽  
Pressure Tube ◽  
Pressure Probe ◽  
External Diameter ◽  
Space Resolution ◽  
Mems Microphone ◽  
Yaw Angle

A new static pressure probe was developed to improve the space resolution and the measurement accuracy of the combined probe for the simultaneous measurement of the static pressure and the velocity in turbulent flows. The external diameter of the static pressure tube is 0.3 mm and its internal diameter is 0.2 mm. There are 8 static pressure holes on the wall of the static pressure tube and their diameters are 0.1 mm. The MEMS microphone is used as the pressure sensor and embedded inside the flare of the static pressure tube. The diameter of the MEMS microphone is 2.54 mm and has the wide range flat frequency response. The measurement results by the new static pressure probe in the two-dimensional turbulent jet show that the measurement accuracy of the static pressure probe is sufficient and the seven-thirds power law is clearly observed in the power spectra of the fluctuating pressure measured at the position of a half width of the mean velocity distribution in the cross-streamwise direction apart from the jet center line. In addition, the yaw angle characteristics of this new pressure probe shows that the measurement accuracy of the static pressure has less dependency on the yaw angle of the probe to the flow direction than the one of the previous static pressure tube (its external diameter is 0.5 mm). From these results, it is found that the new static pressure probe is effective for the measurement of static pressure in turbulent flows and useful to improve the space resolution and the measurement accuracy of the combined probe for the simultaneous measurement of the velocity and the static pressure. By using this static pressure tube, the space resolution of the combined probe is reduced approximately 40%. Further, by combing two X-type hot-wire probes with the new pressure probe, the simultaneous measurement of three velocity components and static pressure is realized.

Exploring Applicability of Acoustic Heat Transfer Enhancement Across Various Perturbation Elements

2020 ◽  
Author(s):  
Tapish Agarwal ◽  
Maximilian Stratmann ◽  
Simon Julius ◽  
Beni Cukurel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Acoustic Excitation ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Number Range ◽  
Flow Modulation ◽  
Spatially Resolved

Abstract The requirements of improved heat transfer performance on turbine surfaces and internal cooling passages drive the research into exploring new methods for efficiency enhancements. Addition of ribbed structures inside the cooling ducts has proven to be most practical, which increases heat transfer from surfaces to fluid flow at the cost of some pressure loss. Many active and passive methods have been proposed for enhancing the heat transfer, where acoustic excitation has been recently shown to be an effective option. Moreover, the existing pressure fluctuations due to rotor-stator interactions can also be utilized as a source of excitation. However, the sensitivity of the phenomenon to various flow and geometric parameters has not been fully characterized. The present study investigates various aspects of convective heat transfer enhancement and turbulent flow modulation caused by acoustic forcing on separating and reattaching flow over isolated rib obstacles. A parametric study is conducted; rib obstacles of various sizes and shapes (including rectangular, squared, triangular, semi-cylindrical, etc.) are installed in a low-speed, fully turbulent wind tunnel and measurements are taken at different velocities and excitation frequencies. Static pressure and spatially resolved surface temperature measurements are performed to quantify the ramifications of acoustic excitation on the wetted wall. Within the favorable Strouhal number range of 0.1–0.25, an optimum value of 0.16 is observed. It is shown that triangular ribs are more prone to acoustic heat transfer enhancement than rectangular or cylindrical perturbations. A linear correlation between static pressure recovery rate and acoustic heat transfer enhancement is observed, which is invariant to change in size/shape of the rib as well as flow and excitation parameters.

Calculation of Aerodynamic Noise for Centrifugal Fan of Air-Conditioner

2013 ◽  
Author(s):  
Taku Iwase ◽  
Hideshi Obara ◽  
Hiroyasu Yoneyama ◽  
Yoshinobu Yamade ◽  
Chisachi Kato
Keyword(s):  
Sound Pressure ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Coarse Grid ◽  
Aerodynamic Noise ◽  
Absolute Velocity ◽  
Centrifugal Fan ◽  
Air Conditioner ◽  
Simulation Code ◽  
Fine Grid

Flow fields in a centrifugal fan for an indoor unit of an air-conditioner were calculated with finite element method-based large eddy simulation (LES) with the aim of predicting fan performance and aerodynamic noise in this study. The numerical simulation code employed throughout the LES was called FrontFlow/blue (FFB). We compared 10M grid [coarse grid] and 60M grid [fine grid] calculation results for investigation of influence of grid resolution. In the fine grid, the number of grid elements in blade-to-blade direction, and of region between the shroud and the bell mouth increased in particular. By calculating with the fine grid, calculated distributions of absolute velocities at blade exit reasonably agreed with experimental results. Because of this, maximum absolute velocity by fine grid near hub decreased as compared to those by coarse grid. Calculated sound pressure level by fine grid was therefore smaller than that by coarse grid, and the overestimation of sound pressure was suppressed by calculating with fine grid. This decrease of the absolute velocity was a first factor for the improvement of calculation accuracy. Moreover, number of captured streaks on the blade, hub, and shroud surfaces by fine grid increased as compared to those by coarse grid. As a result, size of streak by fine grid became smaller than that by coarse grid. Static pressure fluctuations by fine grid on the blade, hub, and shroud surfaces therefore reduced as compared to those by coarse grid. Aerodynamic noise was related to static pressure fluctuations according to Curle’s equation. This reduction of static pressure fluctuations was therefore a second factor for improvement of calculation accuracy.

Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 1 — Forcing Functions

1992 ◽  
Author(s):  
Gregory H. Henderson ◽  
Sanford Fleeter
Keyword(s):  
Linear Theory ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Perforated Plate ◽  
Flow Angle ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Forcing Functions ◽  
Relative Flow ◽  
Gust Response

The fundamental gust modeling assumption is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady periodic flow field is generated by rotating rows of perforated plates and airfoil cascades. In this paper, the measured unsteady flow fields are compared to linear-theory gust requirements, with the resulting unsteady gust response of a downstream stator cascade correlated with linear theory predictions in an accompanying paper. The perforated-plate forcing functions closely resemble linear-theory forcing functions, with the static pressure fluctuations small and the periodic velocity vectors parallel to the downstream mean-relative flow angle over the entire periodic cycle. In contrast, the airfoil forcing functions exhibit characteristics far from linear-theory gusts, with the alignment of the velocity vectors and the static pressure fluctuation amplitudes dependent on the rotor-loading condition, rotor solidity and the inlet mean-relative flow angle. Thus, these unique data clearly show that airfoil wakes, both compressor and turbine, are not able to be modeled with the boundary conditions of current state-of-the-art linear unsteady aerodynamic theory.

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