Unsteady Heat Transfer Between Gas and Tube in a Wave Rotor Refrigerator

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Dapeng Hu ◽  
Jingxian Wang ◽  
Mei Wu ◽  
Tingjiang Liu ◽  
Yiming Zhao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Shock Wave ◽  
High Pressure ◽  
Wave Propagation ◽  
Wall Temperature ◽  
Great Influence ◽  
Longitudinal Direction ◽  
Heat Absorption ◽  
Wave Rotor ◽  
Unsteady Heat Transfer

Abstract The performance of a wave rotor refrigerator (WRR) is strongly affected by unsteady heat transfer between gas and tubes. In this work, the mechanism of the heat transfer and its effects on WRR were investigated numerically and experimentally. Results show that the heat absorption of wave rotor occurs in the process of shock wave propagation, and heat release happens in other processes. The unsteady heat transfer causes an uneven wall temperature. The temperature varies along the longitudinal direction, while the time variation can be neglected. Furthermore, the position of the bolts, which link the wave rotor and the shaft, has a great influence on WRR gaps. The closer the position of bolts to the high-pressure (HP) nozzle is, the less effect of gaps would be. The research is an important guiding significance to the improvement of WRR refrigeration performance and WRR design.

Uncertainty Analysis of Heat Transfer Predictions Using Statistically Modeled Data From a Cooled 1-1/2 Stage High-Pressure Transonic Turbine

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Harika S. Kahveci ◽  
Kevin R. Kirtley
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
High Pressure ◽  
Wall Temperature ◽  
Temperature Measurements ◽  
Navier Stokes ◽  
Inlet Temperature ◽  
Statistical Representation ◽  
Computational Fluid Dynamics Analysis ◽  
Transonic Turbine

This paper compares predictions from a 3D Reynolds-averaged Navier–Stokes code and a statistical representation of measurements from a cooled 1-1/2 stage high-pressure transonic turbine to quantify predictive process sensitivity. A multivariable regression technique was applied to both the inlet temperature measurements obtained at the inlet rake, the wall temperature, and heat transfer measurements obtained via heat-flux gauges on the blade airfoil surfaces. By using the statistically modeled temperature profiles to generate the inlet boundary conditions for the computational fluid dynamics analysis, the sensitivity of blade heat transfer predictions due to the variation in the inlet temperature profile and uncertainty in wall temperature measurements and surface roughness is calculated. All predictions are performed with and without cooling. Heat transfer predictions match reasonably well with the statistical representation of the data, both with and without cooling. Predictive precision for this study is driven primarily by inlet profile uncertainty followed by surface roughness and gauge position uncertainty.

Unsteady Stagnation Point Heat Transfer with Blowing or Suction

1981 ◽  
Vol 103 (3) ◽  
pp. 448-452 ◽  
Author(s):  
Takao Sano
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Prandtl Number ◽  
Asymptotic Solution ◽  
Stagnation Point ◽  
Wall Temperature ◽  
Step Change ◽  
Surface Heat ◽  
Unsteady Heat Transfer ◽  
Prandtl Numbers

The effects of blowing and suction on unsteady heat transfer at a stagnation point due to a step change in wall temperature are examined. Two asymptotic solutions for the temperature field at large and small Prandtl numbers are presented. It is shown that the asymptotic solution for large Prandtl number gives sufficiently accurate results for the surface heat transfer even for the moderate values of Prandtl number if Euler transformation is applied to the series.

Experimental Characterization of the Vane Heat Flux Under Pulsating Trailing-Edge Blowing

2016 ◽  
Author(s):  
J. Saavedra ◽  
G. Paniagua ◽  
B. H. Saracoglu
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Shock Wave ◽  
Heat Flux ◽  
Wall Temperature ◽  
Separation Bubble ◽  
Convective Heat Transfer Coefficient ◽  
Trailing Edge ◽  
Power Extraction ◽  
The Impact

The steady improvement of aircraft engine performance has led towards more compact engine cores with increased structural loads. Compact single-stage high-pressure turbines allow high power extraction, operating in the low supersonic range. The shock waves formed at the airfoil trailing edge contribute substantially to turbine losses, mainly due to the shock-boundary layer interactions as well as high-frequency forces on the rotor. We propose to control the vane trailing edge shock interaction with the downstream rotor, using a pulsating vane-trailing-edge-coolant at the rotor passing frequency. A linear cascade of transonic vanes was investigated at different Mach numbers, ranging from subsonic to supersonic regimes (0.8, 1.1) at two engine representative Reynolds numbers (4 and 6 million). The steady and unsteady heat flux was retrieved using thin-film 2-layered gauges. The complexity of the tests required the development of an original heat transfer post-processing approach. In a single test, monitoring the heat flux data and the wall temperature we obtained the adiabatic wall temperature and the convective heat transfer coefficient. The right-running trailing edge shock wave impacts on the neighboring vane suction side. The impact of the shock wave on the boundary layer creates a separation bubble, which is very sensitive to the intensity and angle of the shock wave. Increasing the coolant blowing rate induces the shock to be less oblique, moving the separation bubble upstream. A similar effect is caused by the pulsations of the coolant.

scholarly journals High Pressure Turbine Vane Annular Cascade Heat Flux and Aerodynamic Measurements With Comparisons to Predictions

1998 ◽  
Author(s):  
Christopher R. Joe ◽  
Xavier A. Montesdeoca ◽  
Friedrich O. Soechting ◽  
Charles D. MacArthur ◽  
Matthew Meininger
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Heat Loss ◽  
Short Duration ◽  
Wall Temperature ◽  
Measured Temperature ◽  
Unique Contribution ◽  
Pressure Measurements ◽  
High Pressure Turbine

Experimental tests were performed at the USAF Turbine Research Facility (TRF) to obtain heat transfer and aerodynamic data on a first stage vane of a modern high pressure turbine. This is a transient blowdown facility that provides data from short duration tests. Data for a matrix of test conditions were obtained to document the effect of inlet Reynolds number, the stage pressure ratio across the vane, and the gas-to-wall temperature ratio. The objectives of these tests were to assess the capability of obtaining accurate aerodynamic total pressure loss measurements and airfoil static pressure measurements as well as determine the heat transfer coefficient distributions on the vanes. Results from these tests were compared to analytical predictions and are presented. The unique contribution of the work presented herein is: 1) demonstration of circumferential traversing temperature and pressure data in a short duration facility test, and 2) heat loss closure during a short duration test using heat flux gauges and the measured temperature loss. The transient heat loss during a short duration test is a fundamental requirement to determine turbine efficiency when work extraction is determined from the temperature drop across the turbine stage. Heat transfer data were acquired from heat flux gauges that were fabricated using thin-film sputtering techniques and placed on the airfoil surfaces. The surface temperature of the gauge was measured and heat flux was determined from a closed form transient semi-infinite solution that included the resistance of the heat flux gauge and the underlying metal substrate. Circumferentially, pressure measurements were obtained on the airfoil surfaces and on traversing rakes at the inlet and exit of the vane test section. Total and differential pressure rake instrumentation was required to obtain accurate aerodynamic loss measurements over a range of gas-to-wall temperature ratios.

scholarly journals A novel shock tube with a laser–plasma driver

2017 ◽  
Vol 35 (4) ◽  
pp. 610-618 ◽  
Author(s):  
Y. Kai ◽  
W. Garen ◽  
T. Schlegel ◽  
U. Teubner
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Wave Propagation ◽  
Initial Conditions ◽  
Optical Breakdown ◽  
Laser Interferometry ◽  
Aluminum Film ◽  
Glass Capillary ◽  
Sudden Appearance ◽  
Novel Method

AbstractA novel method to generate shock waves in small tubes is demonstrated. A femtosecond laser is applied to generate an optical breakdown an aluminum film as target. Due to the sudden appearance of this non-equilibrium state of the target, a shock wave is induced. The shock wave is further driven by the expanding high-pressure plasma (up to 10 Mbar), which serves as a quasi-piston, until the plasma recombines. The shock wave then propagates further into a glass capillary (different square capillaries with hydraulic diameter D down to 50 µm are applied). Shock wave propagation is investigated by laser interferometry. Although the plasma is an unsteady driver, due to the geometrical confinement of the capillaries, rather strong micro shocks can still propagate as far as 35 times D. In addition to the experiments, the initial conditions of this novel method are investigated by hydrocode simulations using MULTI-fs.

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