Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

/pdf/heat-transfer-in-rotating-serpentine-passages-with-trips-chvb37p563.pdf

Heat transfer in rotating serpentine passages with trips normal to the flow

This study adds CuO and Al2O3 nano particles and antifoam respectively into cooling engine oil. A comparison is made between their heat transfer performance and that of oil without adding such substances. The experimental platform is a real-time four-wheel-drive (4WD) transmisson system. It adopts advanced rotary blade coupling (RBC), where a high local temperature occurs easily at high rotating speed. Therefore, it is imperative to improve the heat transfer efficiency. Any resolution to such problems requires a thorough understanding of the thermal behavior of the rotating flow field within the power transmission system. The experiment measures the temperature distribution of RBC exterior at four different rotating speeds (400rpm, 800rpm, 1200rpm and 1600rpm), simulating the conditions of a real car at different rotating speeds and investigating the optimum possible compositions of a nanofluid for higher heat transfer performance.

Heat transfer enhancement of nanofluids in rotary blade coupling of four-wheel-drive vehicles

The simultaneous effects of curvature, rotation and heating/cooling in channel flow complicate the flow and heat transfer characteristics beyond those observed in the channels with simple curvature or rotation. The phenomena encountered are examined for steady, hydrodynamically and thermally fully developed flow in square channels. The governing equations are solved numerically by using a finite‐volume method. Certain hitherto unknown flow patterns are found. And the results show both the nature of the flow transition and the effect of this transition on the distributions of temperature, friction factor and Nusselt number in a square channel.

/pdf/flow-transitions-and-combined-free-and-forced-convective-1i08b4wzrs.pdf

Flow transitions and combined free and forced convective heat transfer in rotating curved channels: The case of positive rotation

Numerical Study of Convective Heat Transfer Enhancement in a Pipe Rotating Around a Parallel Axis

This paper presents experimental results for heat transfer in swirling internal flow, obtained in two ways. A test rig simulated a rotating blade’s leading edge internal passage with heated walls and screw-shaped cooling swirl generated by flow introduced through discrete tangential slots. Spatially resolved variations of the surface heat transfer coefficients were measured in the rotating rig using an IR radiometer.A blade tested in the actual engine environment had similar geometry of the leading edge cooling passage. The blade surface temperatures were mapped in the engine with thermal paints and compared with a traditional convective cooling configuration. The data from the rotating rig and engine measurements are also compared with non-rotating heat transfer results obtained in the hot cascade using a traversing pyrometer at a realistic wall-to-coolant temperature ratio.The results are presented for realistic rotational numbers, ranging from 0 to 0.023, and for representative Reynolds number of 20,000 based on the channel diameter. The effect of Coriolis forces is evident with the change of direction of the rotation. A slight negative influence of the crossflow, which increased toward the outer radius of the channel, was recorded in the rig test results.The results presented will assist in better understanding of the screw-shaped swirl cooling technique, providing the next step toward the application of this highly-effective internal cooling method for the leading edges of turbine blades.© 1998 ASME

W. David Morris

Papers

Heat transfer and fluid flow in rotating coolant channels