scholarly journals Effect of Dimple Depth-Diameter Ratio on the Flow and Heat Transfer Characteristics of Supercritical Hydrocarbon Fuel in Regenerative Cooling Channel

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Lihan Li ◽  
Xin Li ◽  
Jiang Qin ◽  
Silong Zhang ◽  
Wen Bao
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Hydrocarbon Fuel ◽  
Diameter Ratio ◽  
Fluid Temperature ◽  
Cooling Channel ◽  
Heat Transfer Characteristics ◽  
Regenerative Cooling ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

In order to extend the cooling capacity of thermal protection in various advanced propulsion systems, dimple as an effective heat transfer enhancement device with low-pressure loss has been proposed in regenerative cooling channels of a scramjet. In this paper, numerical simulation is conducted to investigate the effect of the dimple depth-diameter ratio on the flow and heat transfer characteristics of supercritical hydrocarbon fuel inside the cooling channel. The thermal performance factor is adopted to evaluate the local synthetically heat transfer. The results show that increasing the dimple depth-diameter ratio h / d p can significantly reduce wall temperature and enhance the heat transfer inside the cooling channel but simultaneously increase pressure loss. The reason is that when h / d p is rising, the recirculation zones inside dimples would be enlarged and the reattachment point is moving downstream, which enlarge both the high Nu area at rear edge of dimple and the low Nu area in dimple front. In addition, when fluid temperature is nearer the fluid pseudocritical temperature, local acceleration caused by dramatic fluid property change would reduce the increment of heat transfer and also reduce pressure loss. In this study, the optimal depth-diameter ratio of dimple in regenerative cooling channel of hydrocarbon fueled is 0.2.

Flow and Heat Transfer Characteristics of Supercritical Hydrocarbon Fuel in Mini Channels With Dimples

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Yu Feng ◽  
Jie Cao ◽  
Xin Li ◽  
Silong Zhang ◽  
Jiang Qin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Hydrocarbon Fuel ◽  
Fuel Properties ◽  
Heated Wall ◽  
Cooling Channel ◽  
Heat Transfer Characteristics ◽  
Regenerative Cooling ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Cooling Passage

An idea of using dimples as heat transfer enhancement device in a regenerative cooling passage is proposed to extend the cooling limits for liquid-propellant rocket and scramjet. Numerical studies have been conducted to investigate the flow and heat transfer characteristics of supercritical hydrocarbon fuel in a rectangular cooling channel with dimples applied to the bottom wall. The numerical model is validated through experimental data and accounts for real fuel properties at supercritical pressures. The study shows that the dimples can significantly enhance the convective heat transfer and reduce the heated wall temperature. The average heat transfer rate of the dimpled channel is 1.64 times higher than that of its smooth counterpart while the pressure drop in the dimpled channel is only 1.33 times higher than that of the smooth channel. Furthermore, the thermal stratification in a regenerative cooling channel is alleviated by using dimples. Although heat transfer deterioration of supercritical fluid flow in the trans-critical region cannot be eliminated in the dimpled channel, it can be postponed and greatly weakened. The strong variations of fuel properties are responsible for the local acceleration of fuel and variation of heat transfer performance along the cooling channel.

Flow and Heat Transfer Characteristics in Models of Turbine Blade Tip-Walls With Three Kinds of Turning Vanes

2018 ◽  
Author(s):  
Bin Wu ◽  
Xing Yang ◽  
Lv Ye ◽  
Zhao Liu ◽  
Yu Jiang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Double Layer ◽  
Pressure Loss ◽  
Stokes Equations ◽  
Wall Heat Transfer ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Blade Tip

In this paper, effects of three kinds of turning vanes on flow and heat transfer of turbine blade tip-walls with a U-shaped channel have been numerically studied. Numerical simulations are performed to solve three-dimensional, steady, Reynolds-averaged Navier-Stokes equations with the standard k-ω turbulence model. The aspect ratio (AR) and the hydraulic diameter of the channel are 2 and 93.13 mm, respectively. The effects of single-layer, double-layer and double-layer dome-shaped turning vanes in the turn region on the tip-wall heat transfer and overall pressure loss of rectangular U-shaped channels are analyzed. Detailed flow and heat transfer characteristics over the tip-walls, as well as the overall performance, are presented and compared with each other. Results show that the tip-wall heat transfer coefficients with double-layer dome-shaped turning vanes are the highest among the three cases. Double-layer dome-shaped turning vanes can promote the lateral spreading of secondary flow and effectively increase the uniformity of heat transfer on the tip-wall. More importantly, this structure can make the cooling air expand and accelerate at the center region of the top of the U-shaped channel, resulting in more heat to be removed from the tip-wall. Additionally, double-layer dome-shaped turning vanes can effectively reduce the pressure loss of the channel.

Numerical Study on the Flow and Heat Transfer Characteristics in Rectangular Channels With Grooves and Different Protrusions

2017 ◽  
Author(s):  
Feng Zhang ◽  
Xinjun Wang ◽  
Jun Li ◽  
Daren Zheng ◽  
Junfei Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rectangular Channels

The present work represents a numerical study on the flow and heat transfer characteristics in rectangular channels with protrusion-grooved turbulators. The Reynolds averaged Navier-Stokes equations, coupled with SST turbulence model, are adopted and solved. In this paper, six geometric protrusion shapes (circular, rectangular, triangular, trapezoidal, circular with leading round concave and circular with trailing round concave) are selected to perform the study. The flow structure, heat transfer enhancement, friction factor as well as thermal performance factor of the rectangular channel fitted with combined groove and different protrusions have been obtained at the Reynolds number ranging from 5000 to 20000. The results indicate that the protrusion shapes affect the velocity distribution near the groove surface. The case of circular protrusion with leading round concave provides the highest overall heat transfer enhancement, while it also causes the highest pressure loss penalty. The case of rectangular protrusion has the lowest overall heat transfer enhancement with high pressure loss penalty. The case of circular protrusion has similar overall heat transfer enhancement with cases of trapezoidal protrusion as well as circular protrusion with trailing round concave, but the pressure loss penalty of the case of circular protrusion is the lowest. In addition, the best overall thermal performance can be observed for circular protrusion-grooved channel.

Detailed Studies on the Flow Field and Heat Transfer Characteristics Inside a Realistic Serpentine Cooling Channel With a S-Shaped Inlet

2018 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Hikaru Odagiri ◽  
Takeshi Horiuchi ◽  
Masahide Kazari
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Flow Visualization ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Cooling Channel ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Inner Surface

Accurate temperature prediction of turbine blades for gas turbine is very important to assure the life-span of the blade under a hostile hot gas environment and intense centrifugal force. Therefore, there have been a number of studies carried out to clarify the cooling performance of serpentine cooling channel inside a turbine blade for gas turbine, however, it remains to be quite difficult to make an accurate numerical prediction of the performance. Apart from the effects of disk rotation as well as large temperature gradient near the wall, such a poor predictability can be attributed to the complicated vortical motions caused by the rib-roughened cooling channel whose cross-sectional shape varies along the channel and by the existence of u-bends. Furthermore, since the cooling channel inside a real turbine blade usually has a curved or S-shaped inlet, which may induce flow separation as well as swirl developed in the inlet, it can be imagined that the flow and heat transfer inside the cooling channel is likely to become much more complicated than that with a straight inlet. Despite this situation, only few studies are made in order to examine the flow and heat transfer characteristics inside the cooling channel with s-shaped inlet. Accordingly, this study aims at detailed experimental and numerical investigations on the flow and heat transfer characteristics of a realistic serpentine rib-roughened cooling channel with an s-shaped inlet, which is modeled from an actual HP turbine blade for gas turbine. This study employs a transient TLC (Thermochromic Liquid Crystal) technique to measure the heat transfer characteristics, along with the flow visualization on the inner surface of the channel using oil mixed with titanium powder. Note that a special focus in this flow visualization is placed on the area of s-shaped inlet. As for the flow measurement, 2D-PIV (Particle Image Velocimetry) method is used to understand time-dependent vortical structures of the flow field that can have significant impacts on the heat transfer. RANS-based numerical simulation is also executed to predict the heat transfer distribution on the inner surface of the cooling channel.

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