Yoshitaka Fukuyama

Turbulence Model Dependencies on Conjugate Simulation of Flow and Heat Conduction

This paper discusses the influences of the turbulence model selection on the heat transfer prediction in the conjugate simulation of flow and heat conduction. It is known that the heat transfer prediction by the flow simulation based on RANS is dependent upon the turbulence model. Common difficulties are the anomalous production of turbulent kinetic energy in a flow with large rates of strain and the laminar-turbulent transition, both of which are persistent aspects in typical turbine cascade flow. Similar and possibly greater impact is expected when these turbulence models are applied to the conjugate simulation of flow and heat conduction. An anomaly treatment called a time-scale bound is applied to the low Reynolds number k-ω and the SST turbulence models installed in the common CFD platform UPACS. The turbulence model dependencies on the conjugate simulation of flow and heat conduction are investigated in an axisymmetric turbulent jet impingement and the 2D turbine cascade vanes.Copyright

Experimental Study on Racetrack-Shaped Holes Impingement Cooling With Bump Type Roughening Element

Cooling effectiveness of an impingement cooling with array of racetrack-shaped impingement holes is investigated. Two types of specimens are investigated. One is a plain target plate and the other is a plate roughened with bump type elements. Sensitivity of relative location of bump to impingement hole on the cooling effectiveness is also investigated.Experiments are conducted under three different mainflow Reynolds numbers ranging from 2.6×105 to 4.7×105, with four different cooling air Reynolds numbers for each main flow condition. The cooling air Reynolds numbers are in the range from 1.2×103 to 1.3×104.Copyright

Local Cooling Effectiveness Distribution of an Integrated Impingement and Pin Fin Cooling Configuration

An integrated impingement and pin-fin cooling configuration is investigated experimentally. Temperature measurements have been performed for several test pieces with various pin/hole arrangements to clarify an influence of pin/hole arrangements on cooling effectiveness. The experiment has been conducted with 673K combustion gas flow and room temperature cooling air. Reynolds number of combustion gas flow is 380000 and Reynolds number of cooling air flow is in the range from 5000 to 30000. An infrared camera is used to measure a temperature distribution on a specimen surface. The area-averaged cooling effectiveness and the local cooling effectiveness are evaluated for each specimen and compared each other. There are evidences of the existence of pins on the local cooling effectiveness at the exact location of those. But the local cooling effectiveness are independent of the hole arrangement.© 2007 ASME

Study on Advanced Internal Cooling Technologies for the Development of Next-Generation Small-Class Aircraft Engines

An innovative internal cooling structure named multislot cooling has been invented for high-pressure turbine (HPT) nozzles and blades. This cooling structure has been designed to be simple and inexpensive and to exhibit good cooling performance. In order to confirm the cooling performance of this structure, test pieces of dummy turbine nozzles were manufactured. Three geometric parameters (width of slots, overall height of cooling channel, and height of jet impingement) are associated with these test pieces. The cooling performance tests were conducted by using these test pieces for several Reynolds numbers of the mainstream hot gas [2.2 × 10 5 -3.4 × 10 5 ] and cooling airflow [3 × 10 3 -1 × 10 4 ]. Infrared images of the heated surfaces of the test pieces were captured for every Reynolds number in the tests, and then the distributions of the cooling effectiveness were obtained. Simultaneously the pressure losses were measured, This paper describes the hot gas flow tests performed to confirm the effects of the geometric parameters on the cooling performance and pressure loss, and to obtain data of Nusselt number and pressure loss coefficient for the design of turbine nozzles in the future by applying this new cooling structure to next-generation small-class aircraft engines. Additionally a preliminary analysis of airfoil cooling was performed to evaluate both cooling performance of conventional impingement cooling and multislot cooling when applied to a HPT nozzle. As a result it was found that the multislot cooling is well applicable to cooling of HPT airfoils.

Leading Edge Cooling Performance of an Integrated Cooling Configuration

This paper presents the experimental work on the leading edge cooling performance of an integrated impingement and pin-fin cooling configuration. Experiments are conducted for seven different spatial geometries under the simulated condition of 1400 degree Celsius-class actual turbine vane leading edge with the temperature ratio of 2.1. The Reynolds number of the hot gas side was 91000 and the cooling air Reynolds number was varied in the range of 5900–47000. The test piece surface temperature distributions were measured using an infrared camera with the correction by a thermocouple embedded on the test piece surface. The cooling effectiveness obtained from the experiments showed the superior cooling performance by the pin-fin integration. The effect of the cooling effectiveness enhancement was more than the cooling surface area increment. The detailed analyses of the cooling performance and the pressure loss characteristics are discussed.© 2008 ASME

Rafting of Single Crystal Superalloy by High Thermal Stress

Rafting of the nickel-base single crystal superalloy CMSX-2 was investigated under the condition of high thermal stress using a newly constructed experimental equipment. The test piece with the diameter of 25 mm was tested at the maximum material temperature of 1 000 degree Celsius for 80 hours. The results showed that the raft structure occurred only under the influence of thermal stress. The raft structure developed parallel to the direction of the compressive thermal stress because of negative lattice misfit. The thickness of gamma phase and gamma prime phase in rafting increase with the increase in the temperature and the thermal stress.

Spatial Arrangement Dependance of Cooling Performance of an Integrated Impingement and Pin Fin Cooling Configuration

Experimental and numerical studies were conducted for the development of the integrated impingement and pin-fin cooling configuration. In the development, the spatial arrangements of impingement hole, pin-fin and film cooling (discharge) hole were the main concern. The temperature measurement was performed for different test pieces with various spatial arrangements to clarify the cooling effectiveness variation with the arrangement and the other cooling parameters. Experiments were conducted with 673K hot gas flow and room temperature cooling air. The Reynolds number of gas side flow was 380000 and cooling air Reynolds number was 5000–30000. Test plate surface temperatures were measured using an infrared camera. The cooling effectiveness obtained from the experiment for one specimen was different from that for a specimen that had the same pin density but a different spatial arrangement. So it was confirmed that an arrangement of hole and pin, as well as pin density, was an important parameter. CFD analysis was also conducted to make clear how spatial arrangement affected internal heat transfer characteristics. Pressure losses were also evaluated for each specimen, and total thermal performance was compared. A basic configuration with one pin at the center of a unit area showed the most superior total thermal performance.© 2005 ASME