Experimental Feasibility Study of Radial Injection Cooling of Three-Pad Air Foil Bearings

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Suman K. Shrestha ◽  
Daejong Kim ◽  
Young Cheol Kim
Keyword(s):  
Heat Exchange ◽  
Flow Rate ◽  
High Speed ◽  
Air Flow ◽  
Air Flow Rate ◽  
Design Factor ◽  
Cooling Performance ◽  
Radial Injection ◽  
Cooling Air Flow ◽  
Cooling Air

The foil bearing (FB) is one type of hydrodynamic bearing using air or another gas as a lubricant. When FBs are designed, installed, and operated properly, they are a very cost-effective and reliable solution for oil-free turbomachinery. Because there is no mechanical contact between the rotor and its bearings, quiet operation with very low friction is possible once the rotor lifts off the bearings. However, because of the high speed of operation, thermal management is a very important design factor to consider. The most widely accepted cooling method for FBs is axial flow cooling, which uses cooling air or gas passing through heat-exchange channels formed underneath the top foil. The advantage of axial cooling is that no hardware modification is necessary to implement it, because the elastic foundation structures of the FB serve as the heat-exchange channels. Its disadvantage is that an axial temperature gradient exists on the journal shaft and bearing. In this paper, the cooling characteristics of axial cooling are compared with those of multipoint radial injection, which uses high-speed injection of cooling air onto the shaft at multiple locations. Experiments were performed on a three-pad FB 49 mm in diameter and 37.5 mm in length, at speeds of 30,000 rpm and 40,000 rpm. Injection speeds were chosen to be higher than the journal surface speed, but the total cooling air flow rate was matched to that of the axial cooling cases. Experimental results show that radial injection cooling is comparable to axial cooling at 30,000 rpm, in terms of cooling performance. Tests at 40,000 rpm reveal that the axial cooling performance reaches saturation when the pressure drop across the bearing is larger than 1000 Pa, while the cooling performance of radial injection is proportional to the cooling air flow rate and does not become saturated. Overall, multipoint radial injection is better than axial cooling at high rotor speeds.

Air Entrainment and Bubble Generation by a Hydrofoil in a Turbulent Channel Flow

2019 ◽  
Author(s):  
Ichiro Kumagai ◽  
Kakeru Taguchi ◽  
Chiharu Kawakita ◽  
Tatsuya Hamada ◽  
Yuichi Murai
Keyword(s):  
Channel Flow ◽  
Flow Rate ◽  
High Speed ◽  
Air Flow ◽  
Air Entrainment ◽  
Air Bubbles ◽  
Air Flow Rate ◽  
Bubble Generation ◽  
Gas Liquid Flow ◽  
Entrained Air

Abstract Air entrainment and bubble generation by a hydrofoil bubble generator for ship drag reduction have been investigated using a small high-speed channel tunnel with the gap of 20 mm in National Maritime Research Institute (NMRI). A hydrofoil (NACA4412, chord length = 40 mm) was installed in the channel and an air induction pipe was placed above the hydrofoil. The flow rate of the entrained air was quantitatively measured by thermal air flow sensors at the inlet of the air induction pipe. The gas-liquid flow around the hydrofoil was visualized by a backlight method and recorded by a high-speed video camera. As the flow velocity in the channel increased, the negative pressure generated above the suction side of the hydrofoil lowered the hydrostatic pressure in the channel, then the atmospheric air was entrained into the channel flow. The entrained air was broken into small air bubbles by the turbulent flow in the channel. The threshold of air entrainment, the air flow rate, and gas-liquid flow pattern depends on Reynolds number, angle of attack (AOA), and hydrofoil type. We identified at least three modes of air entrainment behavior: intermittent air entrainment, stable air entrainment, and air entrainment with a ventilated cavity. At high flow speed in our experimental condition (9 m/s), a large volume of air bubbles was generated by this hydrofoil system (e.g. air flow rate was 50 l/min for NACA4412 at AOA 16 degrees), which has a high potential to reduce ship drag.

Thermal Environment Tests of a High-Speed Aircraft Cockpit

1964 ◽  
Vol 15 (3) ◽  
pp. 203-218 ◽  
Author(s):  
T. L. Hughes
Keyword(s):  
High Speed ◽  
Thermal Environment ◽  
Cooling System ◽  
Air Flow ◽  
Internal Heat ◽  
Inlet Temperature ◽  
A Value ◽  
Heat Leakage ◽  
Cooling Air Flow ◽  
Cooling Air

SummaryThis paper describes rig tests made to evaluate the effectiveness of the cockpit insulation and cooling system of a high-speed aircraft.The tests showed the dependence of cockpit internal temperature distribution and heat pick-up on the cooling air mass flow and inlet temperature. Analysis of the test data showed that there was considerable heat leakage into the cockpit; the heat leakage increased with cooling air flow and constituted two-thirds of the heat entering the cockpit when the air flow was moderately high (20 lb/min). Some of the leakage heat entered the cockpit through equipment mountings but it was evident that other leakage paths existed. One more obvious heat leakage path, at the canopy, is illustrated.The tests also showed that the internal heat transfer coefficient increased with air flow, reaching a value of 2·5 C.H.U./hr ft2°C when the flow was 20 lb/min.

Analysis of Influencing Factors of Pressure Pre-Cooling Rate for Fruits and Vegetables

2013 ◽  
Vol 732-733 ◽  
pp. 581-584
Author(s):  
Qiang Wang ◽  
Fan Wang ◽  
Qi Wang ◽  
Feng Zhen Liu
Keyword(s):  
Cooling Rate ◽  
Fruits And Vegetables ◽  
Air Flow ◽  
Evaluation Index ◽  
Air Flow Rate ◽  
Cooling Process ◽  
Flow Rates ◽  
Different Shapes ◽  
Cooling Air Flow ◽  
Cooling Air

Cooling rate is an important evaluation index of pressure pre-cooling effect for fruits and vegetables. Experimental device of pressure pre-cooling for fruits and vegetables has been established. Pre-cooling process of golden pears has been tested. The key parameters which affected pressure pre-cooling 7/8 cooling time of golden pears such as different air flow rates, different shapes and sizes of vent hole and arrange form have been analyzed. The results show that it is better that cooling air flow rate is between 1.5 m/s and 2 m/s. Ellipse vent hole shape is the best vent hole style and key-groove vent hole is the worst. The cooling rate of stagger array form is faster than the parallel array form.

scholarly journals Comparative Study of the Cross-Flow Heat and Mass Exchangers for Indirect Evaporative Cooling Using Numerical Methods

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3374 ◽  
Author(s):  
Yugang Wang ◽  
Xiang Huang ◽  
Li Li
Keyword(s):  
Numerical Methods ◽  
Comparative Study ◽  
Flow Rate ◽  
Air Flow ◽  
Evaporative Cooling ◽  
Cross Flow ◽  
Air Flow Rate ◽  
Cooling Performance ◽  
Indirect Evaporative Cooling ◽  
The Cross

This paper presents a comparative study of the cross-flow regenerative heat and mass exchanger (HMX) and the conventional cross-flow HMX for indirect evaporative cooling (IEC) with numerical methods. The objective of this study is mainly to clarify the applicability of the two HMXs. The numerical model was built and validated by existing experimental data. The difference in heat and mass transfer between the two HMXs was revealed by analyzing the change of the temperature and moisture content of the air, and the influence of the main operating parameters on the cooling performance of the HMXs was analyzed. In the typical operating conditions, when the HMXs are used alone, the cooling performance of the regenerative HMX is better than that of the conventional HMX under low supply air flow rate. When the HMXs are used in the multistage evaporative cooling systems with high supply air flow rate, the conventional HMX is more suitable as the first stage of the system to pre-cool the supply air, while the regenerative HMX is more suitable as the second stage to re-cool the supply air.

Cooling Air Flow Characteristics in Gas Turbine Components

1982 ◽  
Vol 104 (2) ◽  
pp. 275-280 ◽  
Author(s):  
H. F. Jen ◽  
J. B. Sobanik
Keyword(s):  
Gas Turbine ◽  
Analytical Model ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Air Flow ◽  
Flow Characteristics ◽  
Calibration Procedure ◽  
Bench Test ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (i) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (ii) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.

Spray Generated by an Airblast Atomizer at High-Pressure Conditions

2007 ◽  
Author(s):  
Feras Z. Batarseh ◽  
Ilia V. Roisman ◽  
Cam Tropea
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
High Speed ◽  
Velocity Vector ◽  
Ambient Pressure ◽  
Air Flow ◽  
Water Flow Rate ◽  
The Other ◽  
Air Flow Rate ◽  
Spray Visualization

We present an experimental investigation of a spray generated by an airblast atomizer. Experiments have been performed in a pressure chamber equipped by transparent windows allowing an optical access to the spray. Several techniques of spray investigation have been applied: spray visualization using the high-speed video system, spray visualization and instantaneous velocity measurements using the PIV technique, spray velocimetry and sizing using the IPI and phase Doppler instruments. Phase Doppler instrument has been used to characterize the droplets in the spray: their diameter, two components of the velocity vector. Also the integral parameters of the spray, such as the local volume flux density, have been characterized. We conduct a parametric study of the effect of the ambient pressure, the air flow rate and the water flow rate on an atomized spray. Measurements at different radial locations in the spray and in two planes were performed. The measurements in these two planes allow one to determine the distributions of all the three components of the average drop velocity vector: axial, radial and azimuthal. PDA measurements show that atomized spray is sensitive to any change in the studied parameters. For example, increasing air flow rate from 20 SCMH to 45 SCMH and keeping same water flow rate and pressure, leads to an increase in all velocity components and also to a change in droplets diameters. On the other hand, keeping constant pressure and air flow rate and increasing water flow rate from 0.7 to 1.4 l/hr, leads to an increase in water droplets sizes and the axial velocity component, whereas the other velocity components show a non uniform change. Moreover, increasing the ambient pressure leads to the growth of the spray velocity and drops diameters.

scholarly journals Cooling Air Flow Characteristics in Gas Turbine Components

1981 ◽  
Author(s):  
H. F. Jen ◽  
J. B. Sobanik
Keyword(s):  
Gas Turbine ◽  
Analytical Model ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Air Flow ◽  
Flow Characteristics ◽  
Calibration Procedure ◽  
Bench Test ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (1) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (2) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.

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