Oil Film Method Research Articles

Thermal load distributions on the large-scale turbine blade tip with a rounded inlet edge

Thermal load and near-wall flow characteristics on the flat tip with a rounded inlet edge are investigated in a large-scale aeroengine turbine cascade with the change of tip gap-to-span ratio (h/s), using the naphthalene sublimation and oil film methods. When h/s ≤ 1.5%, there exists no distinct flow separation at the tip gap inlet. For h/s = 0.5% and 1.0%, the tip surface near the inlet has high local thermal load, whereas that near the exit has low local thermal load. When h/s ≥ 1.75%, however, there is a strong flow reattachment after the inlet flow separation, and severe thermal load is found at the reattachment site. Thus, the critical value of h/s, at which the inlet flow separation is triggered, is about 1.75%. The increments of h/s from 0.5% to 1.5%, from 1.5% to 1.75%, and from 1.75% to 2.5% result in a little decrease, a substantial increase, and a relatively small increase in the average tip thermal load, respectively. The rounded flat tip has much lower average thermal load than the simple flat tip especially when 0.5% ≤ h/s ≤ 1.5%. In this study, qualitative tip gap flow models over the rounded flat tip are suggested for the wide range of h/s.

Research on Stability of Gray Value of Excited-State Fluorescent Oil Film Based on Variable Light Vector Angle

In global skin-friction measurement of aircraft, the fluorescent oil film method can characterize the distribution of skin friction well. However, in an actual wind tunnel test, the wing of the aircraft will inevitably produce corresponding vibrations due to the influence of wind, which will change the relative position between fluorescent oil film and UV (ultraviolet) excitation light source (position fixed). This also directly affects gray value imaging of fluorescent oil films. Based on this, a mathematical model is established to judge the stability of the gray value of fluorescent oil film in this vibrational environment; then, the model can be solved to obtain the vibrational range constraint that enables the gray value of fluorescent oil film to be stabilized. In order to simplify the calculation process, the light vector angle is used to describe the constraint, which also makes the results more intuitive. Through experimental analysis and demonstration, the prediction accuracy of this model can reach 95.61%, which has certain practical engineering application significance.

Evaluation of separating-flow behavior on inner elbow by quantitative oil film method

Evaluation of separating-flow behavior on inner elbow by quantitative oil film method

Visualization of the flow field and aerodynamic force on a Horizontal Axis Wind Turbine in turbulent inflows

The evaluation of the stall phenomenon around an airfoil of the Horizontal Axis Wind Turbine (HAWT) was investigated experimentally in turbulent inflows. In order to observe the aerodynamic characteristics, pressures acting on a single rotor surface were measured by a multiport scanner. Furthermore, in order to present flow visualization, blade surface tufts and oil film methods were used to gain insight on the flow characteristics of HAWT airfoil. In this experiment, aerodynamic forces and flow visualization were discussed with different turbulence intensities and low Reynolds numbers. As a result, it is clarified that the flow is separated at the blade leading edge. For the case of TI = 0.20% and Re = 2.0 × 105, the flow is reattached at the trailing edge when the angle of attack is 7°. For the cases of TI = 5.0% and 13.9%, flow separation is generated near the trailing edge. For the flow visualization of oil film method, separation bubble is observed at the case of TI = 0.20% and Re = 2.0 × 105. However, separation bubble is not found at the high turbulence intensities of TI = 5.0% and 13.9%. These results are also similar to investigations at the result of pressure distribution.

境界層内に設置された正四角錐体に作用する抗力と渦構造

Effect of setting and apex angles on the flow drag acting on a pyramid placed in boundary layers has been investigated experimentally. Flow drag was measured by drag balance and flow patterns were examined by oil film method. Drag coefficient takes minimum value for certain range of setting angle. Some characteristic lengths were defined based on oil film observations. Possible behavior of vortical motion and separation or reattachment flows are correlated with the variation of drag coefficient due to setting and apex angles.

Investigations Of A Flow Around The Flying Wing Model At Natural Reynolds Numbers

Studies of flow structure near the surface model of drones have been conducted in the subsonic wind tunnel. Experimental data of flow visualization depending on attack angle were obtained by oil film method. Evolution of flow patterns inside the regions of boundary layer separation in different configurations was demonstrated. Ability of separation control and reduction zones of flow separation by local influence (ribs and cones) has been also studied on the wing surface.

S1160205 熱硬化油膜法による静圧気体軸受すきま内流れの可視化 : 熱硬化油膜の硬度

The heat curing oil film method using thermosetting property oil film is a new oil film method. The heat curing oil film method, in which not only the plane flow pattern in wall surface but also oil film thickness of the steady flow can be measured, is newly developed. The heat curing oil film method is a very useful method for visualization of an air flow in the clearance of an externally pressurized gas-lubricated circular thrust bearing with a central supply hole. The hardness of the heat curing oil film is investigated in this paper.

Experimental study of flow around a pole standing in a scour

The characteristics of fluid flow and fluid force of the pole standing in scour were investigated with several different scour depths conditions by using a wind tunnel. The scour was modeled into a mortar, with an inverted circular cone. The diameter of the pole was 40 mm and the scour depth was changed from H / D (= depth / diameter of the pole) 0.25 to 1.75. The free stream velocity was 16 m / s, making the Reynolds number 4.2 × 104 . Flow visualization was carried out using a surface oil-film method and smoke-wire method. The surface pressure distributions on the pole and the scour were measured and the drag coefficient acting on the pole was determined by integrating the surface pressure distribution on the pole. The characteristics of the flow around the pole and the drag acting on the pole standing on the scour were clarified. The results show that as the scour depth become deep, the flow around the pole is extremely characteristic and the drag coefficient has a maximum value at Z / D = 0.25 and a minimum value at about the midpoint between the ground level and the bottom of the scour.

Measurements of skin friction and heat transfer beneath an impinging slot jet

An experimental study was performed to measure skin friction and surface heat transfer for an orthogonal slot jet impinging on a flat plate. Surface pressure, total pressure, velocity profiles, skin friction and temperature distributions were obtained within twenty nozzle widths of jet centerline at a range of 20,000<Rej<36,000. Stanton gauge, and oil film methods were used to measure skin friction. Multiple micro-thermocouples attached to an iso-flux surface were utilized to acquire the target plate temperature distribution. The majority of the experimental data was taken at a nozzle-to-plate spacing of four nozzle widths where the jet was still within its potential core length. The local surface heat transfer and skin friction distributions showed local extrema that were not coincident, and whose behavior do not appear to be entirely consistent with hypotheses that attribute the secondary peak to laminar-to-turbulent transition of the surface layer. It is believed that these off center peaks occur as a consequence of enhanced turbulent momentum and heat transport in the wall-normal direction.

S1140202 熱硬化油膜法による静圧気体軸受すきま内流れの可視化 : 硬化固定した熱硬化油膜の硬度に及ぼす油膜成分の影響([S114-02]トライボロジーの基礎と応用(2),機素潤滑設計部門)

S1140202 熱硬化油膜法による静圧気体軸受すきま内流れの可視化 : 硬化固定した熱硬化油膜の硬度に及ぼす油膜成分の影響([S114-02]トライボロジーの基礎と応用(2),機素潤滑設計部門)

10307 千鳥・碁盤目配列の違いが60度傾斜ティアドロップディンプル面の伝熱総合性能へ及ぼす影響

Recently, heat transfer enhancement with dimples is going attention in internal cooling of gas turbine blade because it induces small pressure loss for moderate heat transfer enhancement. In this study, staggered and in-line arrangements with 60deg angled teardrop-shaped dimples were experimentally compared. Heat transfer measurements were performed by using transient technique with compensation of three-dimensional heat conduction for the Reynolds number of, Re=16,000-36,000. In addition, flow visualization with combination of oil-film method and particle image velocimetry was performed for Re=26,000. At trailing edge of the dimples, the in-line arrangement showed higher heat transfer enhancement than the staggered arrangement. However, the friction factor also increased in the in-line arrangement, and heat transfer efficiency of the in-line arrangement was lower than that of the staggered arrangement.

Experimental analysis of flow structure in contra-rotating axial flow pump designed with different rotational speed concept

As a high specific speed pump, the contra-rotating axial flow pump distinguishes itself in a rear rotor rotating in the opposite direction of the front rotor, which remarkably contributes to the energy conversion, the reduction of the pump size, better hydraulic and cavitation performances. However, with two rotors rotating reversely, the significant interaction between blade rows was observed in our prototype contra-rotating rotors, which highly affected the pump performance compared with the conventional axial flow pumps. Consequently, a new type of rear rotor was designed by the rotational speed optimization methodology with some additional considerations, aiming at better cavitation performance, the reduction of blade rows interaction and the secondary flow suppression. The new rear rotor showed a satisfactory performance at the design flow rate but an unfavorable positive slope of the head — flow rate curve in the partial flow rate range less than 40% of the design flow rate, which should be avoided for the reliability of pump-pipe systems. In the present research, to understand the internal flow field of new rear rotor and its relation to the performances at the partial flow rates, the velocity distributions at the inlets and outlets of the rotors are firstly investigated. Then, the boundary layer flows on rotor surfaces, which clearly reflect the secondary flow inside the rotors, are analyzed through the limiting streamline observations using the multi-color oil-film method. Finally, the unsteady numerical simulations are carried out to understand the complicated internal flow structures in the rotors.

S114016 熱硬化油膜法による静圧気体軸受すきま内流れの可視化 : 油膜のレオロジー特性に及ぼす油膜成分の影響([S114-01]トライボロジーの基礎と応用(1))

The heat curing oil film method using thermosetting property oil film is a new oil film method. The heat curing oil film method, in which not only the plane flow pattern in wall surface but also oil film thickness of the steady flow can be measured, is newly developed. The heat curing oil film method is a very useful method for visualization of an air flow in the clearance of an externally pressurized gas-lubricated circular thrust bearing with a central supply hole. The effect of oil component on the rheological characteristics of the heat curing oil without hardener is investigated in this paper.

823 熱硬化油膜法による静圧気体軸受すきま内流れの可視化(油膜成分の影響)(GS-10 振動(1))

823 熱硬化油膜法による静圧気体軸受すきま内流れの可視化(油膜成分の影響)(GS-10 振動(1))

Study and Application on the Oil-Film Method Used for Reservoir Protection Drilling and Completion Fluid Systems

To protect reservoir during drilling, the upper drilling fluid is generally converted into reservoir protection fluid by adding proper graded temporary plugging materials based on the average radius of pore throat in the reservoir, coupled with colloid filling particles. However, the fluid converted has a better temporary plugging effect on only some well sections because of the wide distribution of the average radius of pore throat in the reservoir. Aiming at present problems of reservoir protection drilling and completion fluid technology and reservoir characteristics such as strong heterogeneity, wide distribution of pore diameter, difficultly accurate prediction of pore diameter in reservoir, etc., a broad-spectrum oil-film fielding temporary plugging agent was developed with the oil-film method used for reservoir protection drilling. Completion fluid systems were established. The laboratory evaluation and field tests showed that there is good compatibility between the broad-spectrum oil-film fielding temporary plugging agent and common drilling fluid systems, as well, the plugging rate and recovery rate of cores treated by the developed systems are both over 90% and the field test skin factor is close to 0; thus, the developed systems have a better reservoir protection effect than conventional systems and can help to increase daily oil production.

Flow characteristics around a square cylinder with changing chamfer dimensions

It is known that for a square cylinder subjected to uniform flow, the drag force changes with the angle of attack. To clarify the flow characteristics around a square cylinder with corner cutoffs, we measured the drag coefficient and the Strouhal number for changing chamfer dimensions. We analyzed the flow around a square cylinder with corner cutoffs by applying the RNG k–e turbulent model, and investigated the surface flow pattern using visualization by means of the oil film and mist flow method. From these results, we obtained the surface flow patterns by the oil film method and numerical analysis. The numerical results agreed well with the experimental values. The drag coefficient of the square cylinder with corner cutoffs decreased suddenly at an angle of attack of about α = 0°– 10° when compared with the drag coefficient for a square cylinder. The minimum value of the drag coefficient for the square cylinder with corner cutoffs decreased by about 30% compared with that for the square cylinder. The drag coefficient of the square cylinder with 10% corner cutoffs was found to be smallest, since the wake area of this square cylinder was smaller compared with that of the other square cylinder.

G0500-5-2 テーパ形案内羽根を有する遠心圧縮機の動静翼間距離が性能・騒音に与える影響([G0500-5]流体工学部門一般講演(5))

The purpose of this research is to investigate the effects of tapered diffuser vane, which is installed into a centrifugal compressor with shortened impeller-diffuser distance, on compressor performance and radiated noise by experiments. In addition to shortening the length, a half of the original impeller-diffuser distance, diffuser vanes were placed on three variant inlet angle positions. The noise measurements show shortening impeller-diffuser distance enlarged radiated noise but changing inlet angles little influenced to noise. However in compressor performance, in the case of setting tapered diffuser vanes on the small inlet angle position, compressor performance improved 2.24% at designed flow-rate operation and stable operation range enlarged 30% compared with original diffuser setting The oil-film method at diffuser leading edge revealed that these remarkable improvements in compressor performance are caused by tapered diffuser vane. Tapered region suppresses the leading edge vortex growth that blocks the main stream into diffuser passages and causes a loss of a centrifugal compressor.

Tip gap height effects on flow structure and heat/mass transfer over plane tip of a high-turning turbine rotor blade

The effects of tip gap height-to-chord ratio, h/c, on the flow structure and heat/mass transfer over the plane tip surface of a large-scale high-turning turbine rotor blade have been investigated for h/c = 1.0%, 2.0%, 3.0% and 4.0%. For near-wall tip gap flow visualizations, a high-resolution oil film method is employed, and the naphthalene sublimation technique is used for local heat/mass transfer rate measurements. From the tip surface visualizations, a pair of vortices named “tip gap vortices” is identified in the leading edge region within the tip gap. The overall tip gap flow is characterized not only by the tip gap vortices but also by the flow separation/re-attachment process along the pressure-side tip edge. Within the separation bubble, there exist complicated near-wall flows moving toward a mid-chord flow converging area. With increasing h/c, the tip gap vortices, the flow separation/re-attachment, and the converging flows within the separation bubble tend to be intensified. In general, higher thermal load is found along the loci of the tip gap vortices and along the re-attachment line, while lower thermal load is observed behind the tip gap vortex system and near the mid-chord flow converging area. Heat/mass transfer characteristics with the variation of h/c are discussed in detail in conjunction with the tip gap flow features. Based on the flow visualizations and heat/mass transfer data, new realistic tip gap flow models have been proposed for h/c = 1.0 and 4.0%.

G0501-3-2 正方形角柱周りの流れにおける角部形状変化の影響(実験,後流)

It is known that for a square cylinder subjected to uniform flow, the drag force changes with the shape of corner cutoffs. To clarify the flow characteristics around a square cylinder with corner cutoffs we measured the drag coefficient for changing chamfer shape and dimensions. We analyzed the flow around a square cylinder with corner cutoffs by applying the RNG k-ε turbulent model, and investigated the surface flow pattern using visualization by means of the oil-film and mist flow method. From these results, we obtained the surface flow patterns by the oil-film method and numerical analysis. The drag coefficient of the square cylinder with 10% corner cutoffs was found to decrease by about 30 % compared with that for the square cylinder, since the wake area of this square cylinder was smaller compared with that of the other square cylinder.

Influence of Blade Profiles on Flow around Wells Turbine

The Wells turbine rotor consists of several symmetric airfoil blades arranged around a central hub, and the stagger angle is 90 degrees. These characteristics simplify the total construction of OWC type wave energy converters. Although the Wells turbine is simple, the turbine produces a complicated flow field due to the peculiar arrangement of blades, which can rotate in the same direction irrespective of the oscillating airflow. In order to understand these flows, flow visualization is carried out with an oil-film method in the water tunnel. This research aims to analyze the mechanism of the 3-D flows around the turbine with the flow visualization. The flow visualization explained the influence of attack angle, the difference between fan-shaped and rectangular wings, and the sweep angle.