Numerical Simulation of Three Dimensional Flow in Large Mixed-Flow Pump System

Effect of induced airflow on the surface static pressure of pleated fabric filter cartridges during pulse jet cleaning

This study focuses on local heat transfer characteristics on the tip and near-tip regions of a turbine blade with a flat tip, tested under transonic conditions in a stationary, 2-D linear cascade with high freestream turbulence. The experiments were conducted at the Virginia Tech transonic blow-down wind tunnel facility. The effects of tip clearance and exit Mach number on heat transfer distribution were investigated on the tip surface using a transient infrared thermography technique. In addition, thin film gages were used to study similar effects in heat transfer on the near-tip regions at 94% height based on engine blade span of the pressure and suction sides. Surface oil flow visualizations on the blade tip region were carried-out to shed some light on the leakage flow structure. Experiments were performed at three exit Mach numbers of 0.7, 0.85, and 1.05 for two different tip clearances of 0.9% and 1.8% based on turbine blade span. The exit Mach numbers tested correspond to exit Reynolds numbers of 7.6 × 105, 9.0 × 105, and 1.1 × 106 based on blade true chord. The tests were performed with a high freestream turbulence intensity of 12% at the cascade inlet. Results at 0.85 exit Mach showed that an increase in the tip gap clearance from 0.9% to 1.8% translates into a 3% increase in the average heat transfer coefficients on the blade tip surface. At 0.9% tip clearance, an increase in exit Mach number from 0.85 to 1.05 led to a 39% increase in average heat transfer on the tip. High heat transfer was observed on the blade tip surface near the leading edge, and an increase in the tip clearance gap and exit Mach number augmented this near-leading edge tip heat transfer. At 94% of engine blade height on the suction side near the tip, a peak in heat transfer was observed in all test cases at s/C = 0.66, due to the onset of a downstream leakage vortex, originating from the pressure side. An increase in both the tip gap and exit Mach number resulted in an increase, followed by a decrease in the near-tip suction side heat transfer. On the near-tip pressure side, a slight increase in heat transfer was observed with increased tip gap and exit Mach number. In general, the suction side heat transfer is greater than the pressure side heat transfer, as a result of the suction side leakage vortices.

Experimental investigation of wall thickness and hole shape variation effects on full-coverage film cooling performance for a gas turbine vane

Detailed heat transfer coefficient distributions on a squealer tip of a gas turbine blade were measured using a hue detection based transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip region of the pressure and suction sides of a blade were also measured. Tests were performed on a five-bladed linear cascade with blow down facility. The blade was a 2-dimensional model of a first stage gas turbine rotor blade with a profile of a GE-E3 aircraft gas turbine engine rotor blade. The Reynolds number based on the cascade exit velocity and axial chord length of a blade was 1.1×106 and the total turning angle of the blade was 97.7°. The overall pressure ratio was 1.23 and the inlet and exit Mach number were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. The heat transfer measurements were taken at the three different tip gap clearances of 1.0%, 1.5% and 2.5% of blade span. Results showed that the overall heat transfer coefficient on the squealer tip was higher than that on the shroud and the near tip region of the pressure and suction side. Results also showed that the heat transfer coefficients on the squealer tip and its shroud were lower than that on the plane tip and shroud, but the heat transfer coefficients on the near tip region of suction and pressure sides were higher for the squealer tip case.

This publication presents results of the ongoing investigation of transpiration cooling of scramjets conducted at the German Aerospace Center (DLR). It summarizes the results on the influence of the shock-boundary layer interaction on the static wall pressure distribution downstream of the transpiration cooling system obtained in more than 1000 hot run tests. Special focus is placed on the local static pressure distribution in the coolant wake region on the combustion chamber’s upper wall. Furthermore, different flow interaction phenomena were discovered and are thoroughly analyzed by the application of state of the art optical and intrusive measurement techniques like Background Oriented Schlieren (BOS) combined with pressure data analysis and correlation. The unique SBLI behavior of two coolants (hydrogen and nitrogen) and their influence on the static wall pressure distribution gets addressed in this publication. Three different porous wall materials are compared and analyzed in terms of performance, sensitivity to shock- boundary layer interaction issues and their influence on the wall pressure in the coolant wake region. An outlook is presented on
\nthe results of additional experiments using different types of porous media (e.g. ceramics) and improved measurement techniques with the same coolants. Further research requirements and subsequent changes in the test setup are discussed.

The aim of this experimental study is to investigate the diffusion of jets, with particular attention focused on the relationship between the static pressure and the stream wise mean velocity on the development of a two-dimensional air jet. A jet with three injection velocities (11.7, 23.3 and 35.0 m/s) was generated in a two-dimensional wind tunnel. The velocity distributions were measured by an X-type hot-wire anemometer. The static pressure distributions were measured by a static pressure probe developed in our laboratory, which incorporates a hot-wire anemometer. The probe is designed to be able to measure the mean static pressure and pressure fluctuation simultaneously. The sensitivity is 92.3 mV/Pa. The frequency response is flat from 16 Hz to 2.5 kHz. As a result of the experiment, it was found that negative static pressure exists in the turbulent shear layer. It is considered that the entrainment process from the negative static pressure by the vortex structure motion of the turbulent shear layer.

Fluid-Structure Coupling Effects on the Dynamic Response of Pump-Turbine Guide Vanes

The film cooling effectiveness on the surface of a high pressure turbine blade is measured using the Pressure Sensitive Paint (PSP). Four rows of fan-shaped, laid-back compound angled cooling holes are distributed on the pressure side while two such rows are provided on the suction side of the blade. The coolant is only injected to either the pressure side or suction side of the blade at five average blowing ratios from 0.4 to 1.5. Presence of wake due to upstream vanes is simulated by placing a periodic set of rods upstream of the test blade. The wake rods can be clocked by changing their stationary positions to simulate a progressing wake. Effect of wake is recorded at four phase locations with equal intervals along the pitch-wise direction. The free stream Reynolds number, based on the axial chord length and the exit velocity, is 750,000 and the inlet and the exit Mach numbers are 0.27 and 0.44, respectively, resulting in a blade pressure ratio of 1.14. Results reveal that the tip leakage vortices and endwall vortices sweep the coolant film on the suction side to the midspan region. The fan-shaped, laid-back compound angled holes produce good coolant film coverage on the suction side except for those regions affected by the secondary vortices. Due to the concave surface, the coolant trace is short and effectiveness level is low on the pressure surface. However, the pressure side acquires relatively uniform film coverage with the design of multiple rows of cooling holes. The presence of stationary upstream wake results in lower film cooling effectiveness on the blade surface. Variation of blowing ratio from 0.4 to 1.5 shows steady increase in effectiveness on the pressure side or the suction side for a given wake rod phases locations. The compound angle shaped holes outperform the compound angle cylindrical holes by the elevated film cooling effectiveness particularly at higher blowing ratios.

Tip-vortices on axial compressor rotor blades develop due to the pressure difference between suction and pressure side and roll up above the suction side. On a transonic rotor blade the leading edge thickness causes a bow shock which changes over to an expansion wave on the suction side. On the pressure side the shock is being intensified and crosses the passage hitting the neighbouring blade on its suction side. The tip-vortex has to cross the passage shock. The shock-vortex interaction leads to a sudden and strong deceleration of the flow, a rapid expansion of the vortex and, as a consequence, to a strong change in the vorticity distribution of the vortex. Depending on the intensity of the shock-vortex interaction, vortex breakdown occurs and possibly causes compressor stall.

BackgroundPlantar pressure analysis is widely used in the study of knee osteoarthritis (KOA). The present study aimed to investigate the static and dynamic plantar pressure distribution in patients with different stages of unilateral KOA using the Footscan® platform system.Material/MethodsWe recruited 94 patients aged 61.75±7.23 years old with different stages of unilateral KOA for static and dynamic analysis using the Footscan® platform system. The static pressure (%) of the left, right, anterior, posterior, and the pelvic rotation (°) was assessed. The peak pressure (PP, kPa) was investigated in 10 areas of the foot: medial heel (MH), lateral heel (LH), midfoot (MF), first to fifth metatarsals (M1–M5), hallux (T1), and toes 2–5 (T2–5). The correlation between KOA stages and plantar pressure distributions was investigated.ResultsThe results revealed that static pressure on the unaffected side and pelvic rotation were positively correlated with KOA stages. In addition, there was a positive correlation between KOA stages and PP of M5, MF, and LH zones on the affected side and PP of M2, M3, and M4 zones on the unaffected side, and a negative correlation between KOA stages and PP of T1 and T2–5 zones on the affected side.ConclusionsWith the progression of KOA, static plantar pressure tends to distributed on the unaffected side, and the dynamic plantar pressure tends to be distributed laterally on both feet. The plantar pressure distributions in unilateral KOA patients are abnormal and are closely related to the severity of KOA.

As a part of a systematic research program isothermal investigations on the aerodynamics and the heat transfer of a large scale turbine cascade with suction side film cooling with shaped holes and compound inclination were carried out. The film cooling through a row of holes at forty percent chord length on the suction side was supplied by a large plenum chamber. The axial component inclination was kept constant at 30°. All holes have a cylindrical inlet combined with a shaped outlet. Three injection geometries were tested. The first two investigated configurations had no lateral inclination. The hole geometries can be briefly described as follows: Fan-shaped holes with lateral expansion, fan-shaped holes with lateral expansion and streamwise laid-back. The last investigation combined the most complex hole shape with a lateral hole inclination of 45°. Typical engine conditions for the Mach and Reynolds number as well as the inlet turbulence level were maintained. Due to hardware limitations the total temperature was set to 303 Kelvin. The measured data comprise local and integral total pressure loss coefficients obtained by pressure probe traversing at midspan downstream of the cascade. The static profile pressure distribution together with oil-and-dye flow visualisation gives information on the surface flow conditions and boundary layer development especially in the near hole region. Three dimensional hot wire anemometry is used for detailed flow measurements in the hole region. Based on the steady state liquid crystal heat transfer measurement technique pseudo colour contour plots are used for the documentation of the local surface heat transfer coefficient distribution. Laterally averaged and statistically analysed data of the surface heat transfer is applied in further heat transfer examinations. The aim of all investigations is an aerodynamical optimisation of film cooling configurations taking into account the thermal aspects. The most important conclusions can be summarised as follows: Compared to cylindrical holes with the same axial injection angle, shaped holes have a tremendous influence on the flow type in the near hole region. This leads to a more homogeneous pattern of the suction side heat transfer coefficient. The combination of shaped holes and lateral inclination induces definitely higher losses downstream of the cascade compared to the case with no inclination. Due to the lateral injection the former symmetrical vortex branches downstream of the hole are increased asymmetrically. This leads to higher mean heat transfer coefficients in the near hole region downstream of the injection. On the other side laterally blowing increases the homogeneity of the heat transfer coefficient.

There are various types of the windblown sediment traps developed for wind tunnel and field studies. One of the main supports expected from these traps is in measuring surface dust concentrations to appropriately derive flux equations. The measurement performance and accuracy of a trap is very important and depends strictly upon the physical characteristics and the behaviors of dust grains with air flows. This paper presents the measurement results of static pressure distribution (SPD) of wind flow around Vaseline-coated slide (VCS) catchers with an aim of finding out whether or not particle trapping efficiency (η) of the VCS is related to the SPD. The SPD was evaluated by a wind reduction coefficient (Rc) in a series of wind tunnel experiments with different VCS settings which have different attachment configurations on a pole. Three VCS configurations were considered: a configuration on a circular plastic pole (CPP) and two configurations on wooden square poles (WSP1 and WSP2, respectively). Thus, the primary contribution of this work was to experimentally analyze the effect of the different attachment configurations on the SPD, and the secondary objective was to determine the effect of the SPD on the η. It was shown that spatial correlation and spatial pattern of the Rc were different in the surrounding area of each configuration, and ANOVA and DUNCAN tests indicated that η(s) of WSP1, WSP2, and CPP were different at the significant level of P ≤ 0.05 with the mean of 0.94 ± 0.09, 0.63 ± 0.14, and 1.13 ± 0.07, respectively. Additionally, the amount of PM20, PM40, PM60, PM80, and PM100 trapped by the configurations of WSP1, WSP2, and CPP considerably varied depending upon the particular aerodynamic circumstances associated with every configuration.

Distribution of static interference pressure between a thin-wall flexible cup and a flexible shaft fluctuates heavily along the axis of the cup and is quite different from pressure distribution of common interference styles. In this article, aiming at solving distribution of static interference pressure between a thin-wall flexible cup with much thicker bottom and a hollow flexible shaft, mechanical model and mathematical model of solving the problem were built based on classic thin shell theory. Special difference is that precise special solution of bending equation of thin cylindrical shell was used to substitute the special solution which is original from bending deformation of thin cylindrical shell in no moment status. And a brand new general solution, the relational expression between bending deformation of thin wall of the cup and distribution of the static interference pressure, was obtained. Then, a method used to solve the pressure distribution was presented by solving integral equation and applying superposition principle for the first time. Through using the method to solve an example and comparing calculated results with FEM results, it was proved that the method is correct and effective.

Film cooling on a gas turbine blade pressure side or suction side with axial shaped holes

The flow characteristics of homogeneous gases in complex systems are an important issue in many areas, including underground mines. The flow in mine excavations and ventilation systems is described by known mathematical relationships that could be applied to various cases. In this paper, a flow in a duct with a local sink of mass and momentum for multiple variants of cooperation of a mechanical fan was analyzed. The relationships for the total and static pressure of air in the duct were derived. In the next stage, a calculation example of how the mass flow rate of air, and the total and static pressure of the flowing air will change in the tested sections for the duct with and without a sink, is presented. The derived formulas and calculated values for the considered calculation case allow the verification of the obtained relationships at the measurement station. Analyzing the results of the examples presented in the article, it can be concluded that the total and static pressure at the sink point differ depending on the equation of motion used. In the case of the classic equation, the value of total pressure is lower than the value calculated from the new equation of motion, and the difference between them is about 20 Pa. In the case of static pressure, this difference is about 46 Pa. Qualitative differences in the static pressure distribution at the release location were also demonstrated. Depending on the applied approach, positive or negative changes in the static pressure are noticed. The presented form of the equation of motion made it possible to determine the flow characteristics in the duct with a point mass and momentum sink in the case of the operation with and without a fan.