Transducers dynamic pressure

The use of dynamic pressure transducer in the combustor section, especially in the Low NOx Combustors ensures that each combustor can is burning evenly. This is achieved by controlling the flow in each combustor can till the spectrums obtained from each combustor can match. This technique has been used and found to be very effective and ensures smooth operation of the turbine. 

The use of dynamic pressure transducers gives early warning of problems in the compressor. The very high pressure in most of the advanced gas turbines cause these compressors to have a very narrow operating range between surge and choke. Thus, these units are very susceptible to dirt and... 

Implementation of advanced performance degradation models, necessitate the inclusion of advanced instrumentation and sensors such as pyrometers for monitoring hot section components, dynamic pressure transducers for detection of surge and other flow instabilities such as combustion especially in the new dry low NO combustors. To fully round out a condition monitoring system the use of expert systems in determining fault and life cycle of various components is a necessity. 

P. Dario, R. Bedini. and D. DeRossi, A piezoelectric polymer catheter lip dynamic pressure transducer, Digest t Parers BtoMed 80 229 (1960). 

Strain-gauge pressure transducers are manufactured in many forms for measuring gauge, absolute, and differential pressures and vacuum. Full-scale ranges from 25.4 mm of water to 10,134 MPa are available. Strain gauges bonded direc tly to a diaphragm pressure-sensitive element usually have an extremely fast response time and are suitable for high-frequency dynamic-pressure measurements. 

The oil-water dynamic interfacial tensions are measured by the pulsed drop (4) technique. The experimental equipment consists of a syringe pump to pump oil, with the demulsifier dissolved in it, through a capillary tip in a thermostated glass cell containing brine or water. The interfacial tension is calculated by measuring the pressure inside a small oil drop formed at the tip of the capillary. In this technique, the syringe pump is stopped at the maximum bubble pressure and the oil-water interface is allowed to expand rapidly till the oil comes out to form a small drop at the capillary tip. Because of the sudden expansion, the interface is initially at a nonequilibrium state. As it approaches equilibrium, the pressure, AP(t), inside the drop decays. The excess pressure is continuously measured by a sensitive pressure transducer. The dynamic tension at time t, is calculated from the Young-Laplace equation... 

Cavity Type Transducer suitable for making dynamic pressure measurements of ordnance items was discussed by C.L.Pataky, PATR 232"1(1956)(U)... 

The controlled drop tensiometer is a simple and very flexible method for measuring interfacial tension (IFI) in equilibrium as well as in various dynamic conditions. In this technique (Fig. 1), the capillary pressure, p of a drop, which is formed at the tip of a capillary and immersed into another immiscible phase (liquid or gas), is measured by a sensitive pressure transducer. The capillary pressure is related to the IFT and drop radius, R, through the Young-Laplace equation [2,3] ... 

Successful engine design tailors the cylinder aerodynamics to achieve the desired burn rate. In recent times, this has been aided by laser diagnostics and computational fluid dynamics. In-cylinder diagnostic techniques for production engines include the use of rapid response pressure transducers, ion gauges as markers of flame progress, laser doppler velocimetry and emission spectroscopy. These have been reviewed historically by Witze [103]. The two zone analysis of Chun and Heywood [104] enables the net heat release rate to be derived from the pressure-volume relationship [105]. 

Harmonic interfacial disturbances can be induced by bringing an air bubble at the tip of a capillary in oscillation by a piezoelectric excitation system. In more modem Instmments pressure variation in the bubble is directly monitored by pressure transducers. Such a set-up allows the determination of Interfacial dynamic moduli. 

The ballistic bomb (pressure bomb, manometric bomb) is used to study the burning behavior of a -> Gunpowder or -> Propellant charge powder. It consists of a pressure-resistant (dynamic loading up to about 1000 MPa (10000 bar) hollow steel body that can be bolted together and has a hole to adapt a piezoelectric pressure transducer. The pressure p in the bomb is measured as a function of time t. 

Measuring device. This can be a variable capacitance differential pressure transducer (Section 13.3), measuring the pressure of a liquid column of height h. The dynamic response of the sensor is given by eq. (13.9). Let Ap = ah, where a is a constant. Then take... 

IV.2 Consider the liquid level control loop of Figure 13.2d. The differential pressure transducer cell exhibits second-order dynamics, the controller is proportional, and the control valve is linear with flow characteristic curve given by... 

Response times of 15-40 ms seem to be currently in use. Fry et al. (1957) analyzed the dynamic characteristics of three types of commercially available, differential-pressure pneumotachographs which employed concentric cylinders, screen mesh, and parallel plates for the air resistors. Using a high-quality, differential-pressure transducer with each, they measured total flow resistance ranging from 5 to 15 cm HjO. Frequency response curves taken on one model showed fairly uniform response to 40 Hz the second model showed a slight increase in response at 50 Hz, and the third exhibited a slight drop in response at this frequency. 

In a microprocessor-based ventilator, an electronically actuated valve can be employed that has adequate dynamic response ( 20 ms rise time) to regulate PEEP. For this purpose, the pressure in the patient s breath delivery circuit is measured using a pressure transducer (Figure 18.8). The microprocessor initially opens the exhalation valve completely to minimize resistance to expiratory flow. At the same time, it samples the pressure transducer s output and begins to close the exhalation valve as the pressure begins to approach the desired PEEP level, Because the patient s exhaled flow is the only source of pressure, if the airway pressure drops below PEEP, it cannot be brought back up until the next inspiratory period. Hence, an overrun (i.e., a drop to a level below PEEP) in the closed-loop control of PEEP should be avoided. 

Each position command issued to the motor controller caused the pneumatic pressure sensor to expand and contract to simulate respiratory movement. Note that while the motor position was controlled in a close-loop manner, the loop was not closed on the linear displacement. In a reasonable assumption, all mechanical dynamics from the motor shaft to the pressure transducer were neglected. 

Two primary limitations of these modeling efforts involve the representation of tissue properties across the entire limb and the interface condition between the residual limb and prosthesis. The ability of current finite-element models to estimate prosthetic interface stresses, while performing reasonably well in some cases, has not been highly accurate. Nevertheless, the methodology has potential. Advances in finite-element software enabling nonlinear elastomeric formulations of bulk soft tissue, contact analysis, and dynamic analysis may help address some of the current model limitations. Corresponding advances in pressure-transducer technology will help validate the computer models and facilitate interpretation of the analyses. 

The earthquake engineering experimental facility at Northeastern University provides large-scale dynamic testing of soil samples under uniform cyclic or earthquake motions. It includes a shaking table (Fig. 21.2), a data acquisition card (NI-DAQ) and software (LabVIEW), a set of instmments including accelerometers (Crossbow, Ig, 2g, 5g, Fig. 21.3a), linear variable displacement transducers (LVDT, RDP DCTH400AG, Fig. 21.3b), miniature pore pressure transducers (GE Druck PDCR 81, Fig. 21.3c), and multiple bender element and bending disk measurement equipment for S and P wave measurements (Fig. 21.3c-e). 

Pressure transducers that can measure dynamic pressures above 10 kbar and pressure gradients up to 300 bar/ms have been developed. 

The principle of the dynamic pressure determination piezoelectric pressure transducer is described in Section 3.1. In its simplest version, the measuring equipment includes a charge amplifier and a storage oscilloscope. From the voltage signal recorded on the oscilloscope, the shock wave pressure as a function of time is obtained and the shock wave impulse as well. 

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