• New & Renewable Energy
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• v.7 no.3
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• pp.29-35
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• 2011

This paper describes an internal flow characteristics of a fuel pressurized blower, used for 1kW domestic fuel cell system. To analyze the flow field inside the diaphragm cavity, compressible unsteady numerical simulation is introduced. SST model with scalable wall function is employed to estimate the eddy viscosity. Moving mesh system is applied to the numerical analysis for describing the volume change of a diaphragm cavity in time. Throughout numerical simulation with the modeling of the inlet and outlet valves in a diaphragm cavity, unsteady nature of an internal flow is successfully analyzed. Force variations on the lower plate of a diaphragm cavity are evaluated in time. It is found that the driving force at the suction stage of a diaphragm cavity is more necessary than that at the discharging stage.

• New & Renewable Energy
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• v.8 no.3
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• pp.6-13
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• 2012

This paper describes unsteady internal flow characteristics of a cathode air blower, used for the 1 kW fuel cell system. The cathode air blower considered in the present study is a diaphragm type blower. To analyze the flow field inside the diaphragm cavity, compressible unsteady numerical simulation is performed. Moving mesh system is applied to the numerical analysis for describing the volume change of the diaphragm cavity in time. Throughout a numerical simulation by modeling the inlet and outlet valves in a diaphragm cavity, unsteady nature of an internal flow is successfully analyzed. Variations of mass flow rate, force and pressure on the lower moving plate of a diaphragm cavity are evaluated in time. The computed mass flow rate at the same pressure and rotating frequency of a motor has a maximum of 5 percent error with the experimental data. It is found that flow pattern at the suction process is more complex compared to that at the discharge process. Unsteady nature of internal flow in the cathode air blower is analyzed in detail.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.769-772
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• 2009

Diaphragm compressors are used for a hydrogen compression because it can achieve high gas pressure with high purity. But diaphragm's lifetime may depend on the shape of the cavity and deflection from fluctuation the pressure change, which is necessary to monitored. In this study, the gas and hydraulic oil pressure in the cavity were measured as piston speed varies for diaphragm compressor. The results show pressure change quantities were reduced and maximum pressure points are delayed as the piston moves faster. And the hydraulic pressure were elevated as gas pressure elevated. And the compression period was more faster than expansion period.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.298-302
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• 2002

Equivalent volume estimation of the coupler and two coupled microphones has a key role in standard microphone pressure calibration. The equivalent volume of the microphone is determined by the dynamic characteristics of the diaphragm system and front cavity. Therefore the modal parameters of diaphragm system - natural frequency and damping fatter - should be measured explicitly for the estimation of the equivalent volume. The diaphragm system is composed of the vibrating diaphragm, back slit behind diaphragm, pressure equalization vent, and front cavity which are acoustically coupled. In the measurement, the electrostatic actuator was used to excite the system with the swept sine, and the frequency response was obtained. The close actuator in front of the diaphragm must influence the radiation impedance of the system, and then the modal parameters. From the measured frequency response, the natural frequency and the damping factor could be estimated with the Complex exponential method based on the Prony model and the zero crossing real and imaginary plot.

• ETRI Journal
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• v.38 no.4
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• pp.685-694
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• 2016

A surface micromachined piezoresistive pressure sensor with a novel internal substrate vacuum cavity was developed. The proposed internal substrate vacuum cavity is formed by selectively etching the silicon substrate under the sensing diaphragm. For the proposed cavity, a new fabrication process including a cavity side-wall formation, dry isotropic cavity etching, and cavity vacuum sealing was developed that is fully CMOS-compatible, low in cost, and reliable. The sensitivity of the fabricated pressure sensors is 2.80 mV/V/bar and 3.46 mV/V/bar for a rectangular and circular diaphragm, respectively, and the linearity is 0.39% and 0.16% for these two diaphragms. The temperature coefficient of the resistances of the polysilicon piezoresistor is 0.003% to 0.005% per degree of Celsius according to the sensor design. The temperature coefficient of the offset voltage at 1 atm is 0.0019 mV and 0.0051 mV per degree of Celsius for a rectangular and circular diaphragm, respectively. The measurement results demonstrate the feasibility of the proposed pressure sensor as a highly sensitive circuit-integrated pressure sensor.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.91-91
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• 2011

This paper describes development procedure of the four types of fuel cell's blowers: pressurized fuel blower, selective oxidation air blower, cathode air blower, and burner air blower. Diaphragm blowers having two heads are selected to maintain force balance when the rotating arms are moving by the driving motor. Dimensions of a diaphragm cavity is designed according to the optimal design procedure using numerical simulation and experimental measurement. Experimental apparatus is designed by considering the bower characteristics having low flow rate and high pressure. Test blower is operated by a diaphragm, which has suction and discharge port on the top of the blower. For analyzing the internal flow of the blower, three-dimensional Navier-Stokes analysis is introduced in the present study. Throughout the optimal design of the blowers, blower performance is enhanced by reducing the unbalance motion of the rotating arm and loss region in the diaphragm cavity.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.63-68
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• 1998

The absolute pressure sensor using SDB wafer has been fabricated. the structure of the sensor consists of two wheatstone bridges and a diaphragm. One of the two wheatstone bridges is located on the edge of diaphragm, and the other is located on the center of diaphragm. The diaphragm cavity is sealted in vacuum (~10$^{5}$ Torr) to reduce the effect of temperature due to the vapor in the cavity on the sensitivity of pressure sensor. This is the minor method of temperature compensation method. In this experiment the main compensation method is to use the difference of the two bridge offset voltages. The drift of offset voltage with temperature is reduced by using this method so that temperature charcteristics is improved. In this method the temperature effect in the range of 22~100.deg. C was compensated over 80%.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.463-467
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• 2001

In this study, we developed a FFPI (fiber optic Fabry-Perot interferometer) pressure sensor using the Si diaphragm which measures pressure in vivo. The diaphragm and its supporting structure were etched in KOH solution and were fabricated with micromachining technology. For the configuration of the sensor, the length of the cavity of the Fabry-Perot etalon is 15 mm and one end of the etalon was bonded to a Si diaphragm with 507m thickness. When the area of the Si diaphragm was 2$\times$2 mm2 (cavity length 15 mm), it turns out that the pressure sensitivity was about 1.5 degree/kPa. The pressure sensor developed in this study showed that the phase change was linearly proportional to the increasing pressure in the range of 80 kPa.

• Journal of Veterinary Clinics
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• v.16 no.2
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• pp.478-481
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• 1999

A 8 years old male Pomeranian weighing 4 kg was referred because of coughing of 4 months' duration. Heart sounds and cardiac apex beat were showed more intense on the right side. On radiographic views, loss of normal line of the diaphragm, gas-containing intestines and stomach in thoracic cavity, and right displacement of heart were observed. Ultrasonography revealed that liver located adjacent to the heart. Although the dog died due to severe respiratory disorder in surgical procedure, in thoracic and abdominal surgery, a large defect was found in the left and right ventral muscular portion and left central tendon of the diaphragm, extending from the esophageal hiatus to rib. Left and right cranial lobe of liver, small intestines, stomach and spleen were herniated in the thoracic cavity. Because of the size and chronicity of the defect in the diaphragm, closure was impossible with an abdominal muscle graft.

• Journal of Chest Surgery
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• v.44 no.1
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• pp.80-82
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• 2011

A 12-year-old female presented with the abnormal findings on the chest PA. The chest CT revealed a retrosternal defect of the diaphragm and a fatty opacity in the pleural cavity, resulting in a diagnosis of Morgagni hernia. It was decided to undergo a laparoscopic surgery. The retrosternal defect of the diaphragm measuring 3.5 cm in diameter was found, through which a portion of the greater omentum and the fatty tissue connected with the falciform ligament were herniated into the pleural cavity. The greater omentum was pushed back into the peritoneal cavity and the fatty tissue connected with falciform ligament was excised. The mediastinal pleura was plicated and the defect of the diaphragm was repaired primarily. Immediately after the operation, the patient developed a right pneumothorax for which a chest tube was inserted. She was discharged at the post-operative third day without any further complications.