Steady and Unsteady Temperature Measurements in the Wake of a Linear Cascade with Heated Airfoils

2021 ◽  
pp. 1-14
Author(s):  
Svenja Aberle-Kern ◽  
Thomas Ripplinger ◽  
Reinhard Niehuis
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
High Speed ◽  
Measurement Data ◽  
Current Mode ◽  
Constant Current ◽  
Energy Separation ◽  
Hot Wire ◽  
Compressor Cascade ◽  
Unsteady Temperature

Abstract Understanding basic aerodynamic and thermodynamic processes in engine components is critical to achieving higher efficiencies and lower fuel consumption in aircraft engines. To aid in this process, a linear compressor cascade was investigated in the high-speed cascade wind tunnel of the Institute of Jet Propulsion to quantify the influence of heat transfer on the temperature distribution in the wake and, finally, the profile loss. For this purpose, a patented five-hole probe with an integrated thermocouple was developed and applied for steady measurements. Additionally, a hot-wire measurement set-up was implemented to receive temperature fluctuations via the constant current mode as well as velocity fluctuations via the constant temperature mode. A novel method for a two-way temperature and velocity correction for the two types of hot-wire measurement is presented. Good agreement between the measurement data of the five-hole probe and averaged data from hot-wire anemometry was found. The temperature distribution indicates the occurrence of energy separation which in some cases is overlain with the effects of heat transfer. In addition, the analysis of unsteady fluctuations of temperature and velocity give more detailed information about the vortex shedding in the wake, including the size of the vortices. Finally, this is the first discussion of energy separation at a compressor cascade combined with overlain effects of heat transfer on the blade surface.

Steady and Unsteady Temperature Measurements in the Wake of a Linear Cascade With Heated Airfoils

2020 ◽  
Author(s):  
Svenja Aberle-Kern ◽  
Thomas Ripplinger ◽  
Reinhard Niehuis
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
High Speed ◽  
Measurement Data ◽  
Current Mode ◽  
Constant Current ◽  
Energy Separation ◽  
Hot Wire ◽  
Compressor Cascade ◽  
Unsteady Temperature

Abstract Understanding basic aerodynamic and thermodynamic processes in engine components is critical to achieving higher efficiencies and lower fuel consumption in aircraft engines. To aid in this process, a linear compressor cascade was investigated in the high-speed cascade wind tunnel of the Institute of Jet Propulsion to quantify the influence of heat transfer on the temperature distribution in the wake and, finally, the profile loss. For this purpose, a patented five-hole probe with an integrated thermocouple was developed and applied for steady measurements. Additionally, a hot-wire measurement set-up was implemented to receive temperature fluctuations via the constant current mode as well as velocity fluctuations via the constant temperature mode. A novel method for a two-way temperature and velocity correction for the two types of hot-wire measurement is presented. Good agreement between the measurement data of the five-hole probe and averaged data from hot-wire anemometry was found. The temperature distribution indicates the occurrence of energy separation which in some cases is overlain with the effects of heat transfer. In addition, the analysis of unsteady fluctuations of temperature and velocity give more detailed information about the vortex shedding in the wake, including the size of the vortices. Finally, this is the first discussion of energy separation at a compressor cascade combined with overlain effects of heat transfer on the blade surface.

Loss determination at a linear cascade under consideration of thermal effects

2020 ◽  
Vol 124 (1280) ◽  
pp. 1592-1614
Author(s):  
S. Aberle-Kern ◽  
R. Niehuis ◽  
T. Ripplinger
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Measurement Data ◽  
Evaluation Procedure ◽  
Special Focus ◽  
Compressor Cascade ◽  
Linear Cascade ◽  
Research Activities ◽  
Set Up ◽  
Profile Loss

ABSTRACTTargeting higher efficiencies and lower fuel consumption of turbomachines, heat transfer and profile loss are research topics of particular interest. In contrast to that, the interaction of both was, so far, rarely investigated, but gains in importance in recent research activities. The profile loss of engine components can be characterised by the airfoil wakes at the blade rows utilising established measurement and evaluation methods for which an adiabatic flow is typically supposed. To enable the investigation of the influence of heat transfer at the blade on the loss characteristics, a novel evaluation procedure was set up. In addition to the pneumatic data, the total temperature in the airfoil wake at a linear cascade was measured by means of a five-hole probe with an integrated thermocouple. For the evaluation and analysis of these data, different definitions of the loss coefficient were investigated and, finally, extended to account for thermal aspects. Furthermore, established techniques to average the local wake data were applied and compared with special focus to their suitability for non-adiabatic cases. Moreover, an extended version of the mixed-out average as defined by Amecke was utilised applying not only a far-reaching consideration of a temperature gradient but also the inclusion of the third spatial dimension to enable the evaluation of field traverses in addition to single wake traverses. These techniques were applied to wake measurement data from a linear compressor cascade gained in a special test set-up in the high-speed cascade wind tunnel for different operating points and different blade temperatures. The suitability of the new methods could be proven, and initial steps of the aerodynamic analysis of the resulting data are presented. Thereby, the acquired techniques turned out as powerful methods for the evaluation of wake traverses on compressor and turbine cascades under non-adiabatic conditions.

Effect of Draw Furnace Geometry on High Speed Optical Fiber Manufacturing

2000 ◽  
Author(s):  
Xu Cheng ◽  
Yogesh Jaluria
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Optimal Design ◽  
Optical Fiber ◽  
High Speed ◽  
Graphite Furnace ◽  
Large Diameter ◽  
High Volume ◽  
Force Balance ◽  
Zonal Method

Abstract The motivation of manufacturers to pursue higher productivity and low costs in the fabrication of optical fibers requires large diameter silica-based preforms drawn into fiber at very high speed. An optimal design of the draw furnace is particularly desirable to meet the need of high-volume production in the optical fiber industry. This paper investigates optical fiber drawing at high draw speeds in a cylindrincal graphite furnace. A conjugate problem involving the glass and the purge gases is considered. The transport in the two regions is coupled through the boundary conditions at the free glass surface. The zonal method is used to model the radiative heat transfer in the glass. The neck-down profile of the preform at steady state is determined by a force balance, using an iterative numerical scheme. Thermally induced defects are also considered. To emphasize the effects of draw furnace geometry, the diameters of the preform and the fiber are kept fixed at 5 cm and 125 μm, respectively. The length and the diameter of the furnace are changed. For the purposes of comparison, a wide domain of draw speeds, ranging from 5 m/s to 20 m/s, is considered, and the form of the temperature distribution at the furnace surface is kept unchanged. The dependence of the preform/fiber characteristics, such as neckdown profile, velocity distribution and lag, temperature distribution and lag, heat transfer coefficent, defect concentration, and draw tension, on the furnace geometry is determined. Based on these numerical results, an optimal design of the draw furnace can be developed.

Exact Solution of Unsteady Conductive Heat Transfer in Cylindrical Composite Laminates

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
M. Norouzi ◽  
S. M. Rezaei Niya ◽  
M. H. Kayhani ◽  
M. Shariati ◽  
M. Karimi Demneh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Exact Solution ◽  
Temperature Distribution ◽  
Composite Laminates ◽  
Exact Analytical Solution ◽  
Conductive Heat Transfer ◽  
Orthotropic Materials ◽  
Conductive Heat ◽  
Multilayer Composite ◽  
Unsteady Temperature

This paper presents an exact analytical solution for unsteady conductive heat transfer in a cylindrical multilayer composite laminate. Here, it is supposed that fibers have been wound around the cylinder in each lamina. In order to find the exact solution, the Laplace transformation is applied on anisotropic heat conduction equation to convert the time scale of problem to frequency scale and the separation of variable method is used to solve the resulted partial differential equations. The effect of fibers arrangements of multilayer cylindrical laminates and thermal boundary conditions on unsteady conductive heat transfer of these orthotropic materials is studied based on the exact solution that is presented in the current investigation. The analytical results illustrated that the unsteady temperature distribution in any multilayer composite laminates is in a state between the temperature distribution in single layer laminates with fibers’ angle equal to 0 deg and 90 deg.

scholarly journals The Simultaneous Analysis of Droplets’ Impacts and Heat Transfer during Water Spray Cooling Using a Transparent Heater

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2730
Author(s):  
Vladimir Serdyukov ◽  
Nikolay Miskiv ◽  
Anton Surtaev
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Spray Cooling ◽  
Capillary Waves ◽  
Heat Fluxes ◽  
Small Scale ◽  
Unsteady Temperature ◽  
The Impact

This paper demonstrates the advantages and prospects of transparent design of the heating surface for the simultaneous study of the hydrodynamic and thermal characteristics of spray cooling. It was shown that the high-speed recording from the reverse side of such heater allows to identify individual droplets before their impact on the forming liquid film, which makes it possible to measure their sizes with high spatial resolution. In addition, such format enables one to estimate the number of droplets falling onto the impact surface and to study the features of the interface evolution during the droplets’ impacts. In particular, the experiments showed various possible scenarios for this interaction, such as the formation of small-scale capillary waves during impacts of small droplets, as well as the appearance of “craters” and splashing crowns in the case of large ones. Moreover, the unsteady temperature field during spray cooling in regimes without boiling was investigated using high-speed infrared thermography. Based on the obtained data, the intensity of heat transfer during spray cooling for various liquid flow rates and heat fluxes was analyzed. It was shown that, for the studied regimes, the heat transfer coefficient weakly depends on the heat flux density and is primarily determined by the flow rate. In addition, the comparison of the processes of spray cooling and nucleate boiling was made, and an analogy was shown in the mechanisms that determine their intensity of heat transfer.

Bead formation and wire temperature distribution during ULTRA-HIGH-SPEED GTA WELDING using pulse-heated hot-wire

2011 ◽  
Vol 55 (3-4) ◽  
pp. 12-18 ◽  
Author(s):  
Kenji Shinozaki ◽  
Motomichi Yamamoto ◽  
Koichi Mitsuhata ◽  
Toshiharu Nagashima ◽  
Tatsunori Kanazawa ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
High Speed ◽  
Gta Welding ◽  
Hot Wire ◽  
Wire Temperature ◽  
Bead Formation ◽  
Ultra High Speed

scholarly journals A Smart Two-Stage Charging Strategy Implemented on a PV Module Array with a Simple MPPT for LiFePO4 Batteries

2018 ◽  
Author(s):  
Pi-Yun Chen ◽  
Kuei-Hsiang Chao ◽  
Yu-Sheng Tsai
Keyword(s):  
High Speed ◽  
Current Mode ◽  
Buck Converter ◽  
Constant Current ◽  
Storage Device ◽  
Photovoltaic Module ◽  
Constant Voltage ◽  
Battery Charger ◽  
Two Stage ◽  
Charging Strategy

This paper aims to present a smart high speed battery charger, powered by a photovoltaic module array, for a LiFePO4 battery as a solar energy storage device. With a battery charging strategy, the presented battery charger involves a Buck converter as the core equipped with a simple maximum power point (MPP) tracker. Considering complexity reduction and easy hardware implementation, a constant voltage MPP tracking approach is adopted such that the maximum amount of output power can be delivered to the load in response to an arbitrary change in the solar radiation. A smart two-stage charging strategy, with a constant current mode followed by a constant voltage mode, is employed in such a way that the battery charge process can be accelerated largely, while the damage caused by overcharging can be prevented. In the end, the performance of this proposal is validated experimentally.

scholarly journals Temperature distribution of a test specimen with high-speed heat air-flow passing through

2018 ◽  
Vol 22 (6 Part A) ◽  
pp. 2527-2538 ◽  
Author(s):  
Kai Xiong ◽  
Yunhua Li ◽  
Sujun Dong
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Test Specimen ◽  
High Speed ◽  
Air Flow ◽  
Prediction Method ◽  
Average Temperature ◽  
Hot Air ◽  
Heat Transfer Theory ◽  
Good Agreement

In this paper, a solution method for the temperature distribution of rectangular test specimen with a high-speed heat air-flow passing through is proposed based on the heat transfer theory and numerical calculation, and the feasibility of temperature prediction method is validated. Firstly, the partial differential equations to describe the average temperature in the section of the hot air-flow and the specimen are established and the solving method using MATLAB solver is proposed. Then, based on heat transfer conduction equation and the average temperature, the temperature distribution at different point in each section is calculated. The comparison between numerical computation and experiment shows that two results are in good agreement, which verifies the correctness of the presented prediction method of the temperature distribution of the specimen.

scholarly journals Study on the Thermal Performance and Temperature Distribution of Ball Bearings in the Traction Motor of a High-Speed EMU

2020 ◽  
Vol 10 (12) ◽  
pp. 4373
Author(s):  
Yu Wang ◽  
Junci Cao ◽  
Qingbin Tong ◽  
Guoping An ◽  
Ruifang Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Generation ◽  
Thermal Performance ◽  
High Speed ◽  
Convection Heat Transfer ◽  
Ball Bearings ◽  
Convection Heat ◽  
Rolling Bearings ◽  
Traction Motors

The transient thermal performance of rolling bearings affects the mechanical performance and system safety of traction motors. Most of the traditional empirical formulas used in temperature analysis have been simplified and cannot be completely applied to the calculation of heat generation and convection heat transfer coefficients. Based on the comparative analysis of finite element transient temperature and experimental data, this paper proposes a correction method of mathematical model and derives an accurate calculation formula for the heat generation and lubricant convection heat transfer coefficient of ball bearings applicable for the non-driving end in the traction motor of a high-speed EMU (Electric Multiple Unit). The accuracy of the results has been verified by durability experiment data. In addition, with changes in speed, radial load and other factors taken into account, we have analyzed the influence of these time-varying factors on ball bearing temperature, as well as the temperature distribution law of each component in a grease-lubricated bearing, in a bid to lay a foundation for follow-up research on the heat transfer laws of traction motors and rolling bearings.

scholarly journals An Ultra-Fast TSP on a CNT Heating Layer for Unsteady Temperature and Heat Flux Measurements in Subsonic Flows

Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 657
Author(s):  
Martin Bitter ◽  
Michael Hilfer ◽  
Tobias Schubert ◽  
Christian Klein ◽  
Reinhard Niehuis
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Surface Temperature ◽  
Flat Plate ◽  
High Speed ◽  
Ambient Pressure ◽  
Frame Rate ◽  
Temperature Fields ◽  
Test Case ◽  
Unsteady Temperature

In this paper, the authors demonstrate the application of a modified Ru(phen)-based temperature-sensitive paint which was originally developed for the evaluation of unsteady aero-thermodynamic phenomena in high Mach number but short duration experiments. In the present work, the modified TSP with a temperature sensitivity of up to −5.6%/K was applied in a low Mach number long-duration test case in a low-pressure environment. For the demonstration of the paint’s performance, a flat plate with a mounted cylinder was set up in the High-Speed Cascade Wind Tunnel (HGK). The test case was designed to generate vortex shedding frequencies up to 4300 Hz which were sampled using a high-speed camera at 40 kHz frame rate to resolve unsteady surface temperature fields for potential heat-transfer estimations. The experiments were carried out at reduced ambient pressure of p∞ = 13.8 kPa for three inflow Mach numbers being Ma∞=[0.3;0.5;0.7]. In order to enable the resolution of very low temperature fluctuations down to the noise floor of 10−5 K with high spatial and temporal resolution, the flat plate model was equipped with a sprayable carbon nanotube (CNT) heating layer. This constellation, together with the thermal sensors incorporated in the model, allowed for the calculation of a quasi-heat-transfer coefficient from the surface temperature fields. Besides the results of the experiments, the paper highlights the properties of the modified TSP as well as the methodology.

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