An Experimental and Theoretical Investigation of Wave Propagation in Teflon and Nylon Tubing With Methods to Prevent Aliasing in Pressure Scanners

2013 ◽  
Author(s):  
Adam M. Hurst ◽  
Joe VanDeWeert
Keyword(s):  
Frequency Response ◽  
Dynamic Pressure ◽  
Sampling Rate ◽  
Aircraft Design ◽  
Experimental Results ◽  
Analytical Models ◽  
Pressure Measurements ◽  
Pressure Transmission ◽  
Dynamic Pressure Measurements ◽  
Nylon Tubing

Accurate static and dynamic pressure measurements provide the feedback needed to advance gas turbine efficiency and reliability as well as improve aircraft design and flight control. During turbine testing and aircraft flight testing, flush mounting pressure transducers at the desired pressure measurement location is not always feasible and recess mounting with connective tubing is often used as an alternative. Resonances in the connective tubing can result in aliasing within pressure scanners even within a narrow bandwidth and especially when higher frequency content DC to ∼125Hz is desired. We present experimental results that investigate tube resonances and attenuation in 1.35mm inner diameter (ID) (used on 0.063in tubulations) and 2.69mm ID (used on 0.125in tubulations) Teflon and Nylon tubing at various lengths. We utilize a novel dynamic pressure generator, capable of creating large changes in air pressure (<1psi to 10psi, <6.8kPa to 68.9kPa), to determine the frequency response of such tubing from ∼1Hz to 2,800Hz. We further compare these experimental results to established analytical models for propagation of pressure disturbances in narrow tubes. While significant theoretical and experimental work relating to the frequency response of connective tubing or transmission lines has been published, there is limited literature presenting experimental frequency response data with air as the media in elastic tubing. In addition, little progress has been made in addressing the issue of tubing-related aliasing within pressure scanners, as the low sampling rate in scanners often makes post-processing antialiasing filters ineffective. The experimental results and analytical models presented herein can be used as a guideline to prevent aliasing and signal distortion by guiding the proper design of pressure transmission systems, resulting in accurate static and dynamic pressure measurements with pressure scanners. The data presented here should serve as a reference to instrumentation engineers so that they can make higher frequency measurements (up to ∼125Hz, currently) and are able to quantify the expected pressure transmission line (tube) attenuation and know if aliasing will be a concern. This information will give engineers greater measurement capability when using pressure scanners to make static and dynamic pressure measurements.

An Experimental and Theoretical Investigation of Wave Propagation in Teflon and Nylon Tubing With Methods to Prevent Aliasing in Pressure Scanners

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Adam M. Hurst ◽  
Joe VanDeWeert
Keyword(s):  
Frequency Response ◽  
Transmission Lines ◽  
Flight Control ◽  
Dynamic Pressure ◽  
Sampling Rate ◽  
Aircraft Design ◽  
Experimental Results ◽  
Analytical Models ◽  
Experimental Frequency ◽  
Nylon Tubing

Accurate static and dynamic pressure measurements provide the feedback needed to advance gas turbine efficiency and reliability as well as improve aircraft design and flight control. During turbine testing and aircraft flight testing, flush mounting pressure transducers at the desired pressure measurement location is not always feasible and recess mounting with connective tubing is often used as an alternative. Resonances in the connective tubing can result in aliasing within pressure scanners even within a narrow bandwidth and especially when higher frequency content dc to ∼125 Hz is desired. We present experimental results that investigate tube resonances and attenuation in 1.35 mm inner diameter (I.D.) (used on 0.063 in. tubulations) and 2.69 mm I.D. (used on 0.125 in. tubulations) Teflon and Nylon tubing at various lengths. We utilize a novel dynamic pressure generator, capable of creating large changes in air pressure (<1 psi to 10 psi, <6.8 kPa to 68.9 kPa), to determine the frequency response of such tubing from ∼1 Hz to 2800 Hz. We further compare these experimental results to established analytical models for propagation of pressure disturbances in narrow tubes. While significant theoretical and experimental work relating to the frequency response of connective tubing or transmission lines has been published, there is limited literature presenting experimental frequency response data with air as the media in elastic tubing. In addition, little progress has been made in addressing the issue of tubing-related aliasing within pressure scanners, as the low sampling rate in scanners often makes postprocessing antialiasing filters ineffective.

A Study of Bulk Modulus, Entrained Air, and Dynamic Pressure Measurements in Liquids

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Adam M. Hurst ◽  
Joe VanDeWeert
Keyword(s):  
Bulk Modulus ◽  
Frequency Response ◽  
Measurement System ◽  
Pressure Transducer ◽  
Dynamic Pressure ◽  
Pressure Measurements ◽  
Liquid Media ◽  
Pressure Transducers ◽  
Dynamic Pressure Measurements ◽  
Dissolved Air

Accurate static and dynamic pressure measurements in liquids, such as fuel, oil, and hydraulic fluid, are critical to the control and health monitoring of turbomachinery and aerospace systems. This work presents a theoretical and experimental study of the frequency response of pressure transducers and pressure measurement systems in liquid media. First, we theoretically predict the frequency response of pressure transducers based upon a lumped-parameter model. We then present a liquid-based dynamic pressure calibration test apparatus that validates this model by performing several critical measurements. This system first uses a vibrating liquid column to dynamically calibrate and experimentally determine the frequency response of a test pressure transducer, measurement system or geometry. Second, this calibration system experimentally extracts the bulk modulus of the fluid and the percent of entrained and/or dissolved air by volume. Bulk modulus is determined by measuring the speed of sound within the liquid and through static pressure loading while measuring the deflection of the liquid column. Bulk modulus and the entrained/dissolved gas content within the liquid greatly impact the observed frequency response of a pressure transducer or geometry. Gases, such as air, mixed or dissolved into a fluid can add substantial damping to the dynamic response of the fluid measurement system, which makes measurement of the bulk modulus and entrained and/or dissolved air critical for accurate measurement of the frequency response of a system when operating with a liquid media. All experimental results are compared to theoretical predictions.

scholarly journals Reproducibility of C. I. P.-compatible dynamic pressure measurements

2020 ◽  
Vol 87 (10) ◽  
pp. 630-636
Author(s):  
Oliver Slanina ◽  
Susanne Quabis ◽  
Robert Wynands
Keyword(s):  
Dynamic Pressure ◽  
Storage Conditions ◽  
Dynamic Measurement ◽  
Gas Pressure ◽  
Pressure Measurements ◽  
Small Arms ◽  
Minimum Pressure ◽  
Maximum Value ◽  
Preliminary Study ◽  
Dynamic Pressure Measurements

AbstractTo ensure the safety of users like hunters and sports shooters, the dynamic pressure inside an ammunition cartridge must not exceed a maximum value. We have investigated the reproducibility of the dynamic measurement of the gas pressure inside civilian ammunition cartridges during firing, when following the rules formulated by the Permanent International Commission for the Proof of Small Arms (C. I. P.). We find an in-house spread of 0.8 % between maximum and minimum pressure for runs with the same barrel and of 1.8 % among a set of three barrels. This sets a baseline for the expected agreement in measurement comparisons between different laboratories. Furthermore, a difference of more than 3 % is found in a preliminary study of the influence of ammunition storage conditions.

Application of side-hole fibers for dynamic pressure measurements

2000 ◽  
Author(s):  
Wojtek J. Bock ◽  
Magdalena S. Nawrocka ◽  
Waclaw Urbanczyk
Keyword(s):  
Dynamic Pressure ◽  
Pressure Measurements ◽  
Side Hole ◽  
Dynamic Pressure Measurements

Highly sensitive fiber optic sensor for dynamic pressure measurements

1999 ◽  
Author(s):  
Magdalena S. Nawrocka ◽  
Wojtek J. Bock ◽  
Waclaw Urbanczyk ◽  
Jan Wojcik
Keyword(s):  
Fiber Optic ◽  
Dynamic Pressure ◽  
Fiber Optic Sensor ◽  
Pressure Measurements ◽  
Optic Sensor ◽  
Highly Sensitive ◽  
Dynamic Pressure Measurements

Experimental Study on Pressure Fluctuations in the Boundary Layer of an Axisymmetric Body

2011 ◽  
Vol 66-68 ◽  
pp. 1488-1493
Author(s):  
Hong Xiao ◽  
Chao Gao ◽  
Zhen Kun Ma
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Mach Number ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Axisymmetric Body ◽  
Pressure Measurements ◽  
Fluctuating Pressure ◽  
Frequency Domains ◽  
Dynamic Pressure Measurements

The characteristics of the fluctuating pressure in the boundary layer of an axisymmetric body have been investigated experimentally using dynamic pressure measurements and Schlieren photograghs. Data were acquired at subsonic and super-sonic Mach numbers. The angles of attack ranged from 0° to 5°. Pressure signals were measured simultaneously in several positions along the model and were analyzed both in the time and frequency domains. The Mach number shows the relevant influence on . Furthermore, the pressure fluctuations’ level decreases with the increasing of Mach number except M=1.15. And it is shown that, the location along the axis of the model and the angles of attack have small effect on pressure fluctuations.

Frequency Response Characterization for Dynamic Measurement of Pressure

2019 ◽  
Author(s):  
George Papadopoulos ◽  
Daniel Bivolaru
Keyword(s):  
Frequency Response ◽  
Dynamic Pressure ◽  
Harsh Environments ◽  
Measured Signal ◽  
Sensing Element ◽  
Optimum Frequency ◽  
Size Constraints ◽  
Dynamic Pressure Measurements ◽  
Point Level ◽  
Transducer Frequency

Abstract Transducer requirements for making true dynamic pressure measurements point to a miniature point-level sensing element that is exposed to the flow. Meeting this requirement, however, is often challenged by transducer size constraints, integration at the location of measurement, and packaging, especially when one considers applications in harsh environments where protection of the sensing element may be needed. As part of an effort towards the development of a high frequency pressure measurement device for use in harsh environments (ultra-high temperature), an investigation was performed to evaluate the effect of sensing element packaging and geometry at the point of measurement on the dynamic response of a nominal transducer. Frequency and time domain calculations were performed to assess variations on the magnitude and phase between an input signal and a “measured” signal at the sensing element location for a range of probe tip parameters. The results offer insights and metrics that can govern transducer sensing element and probe tip implementation for optimum frequency response and strategies for compensation.

Comparison Between Self-Excited and Forced Flame Response of an Industrial Lean Premixed Gas Turbine Injector

2011 ◽  
Author(s):  
Stephen Peluso ◽  
Bryan D. Quay ◽  
Jong Guen Lee ◽  
Domenic A. Santavicca
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Dynamic Pressure ◽  
Variable Length ◽  
Finite Limit ◽  
Pressure Measurements ◽  
Operating Condition ◽  
Lean Premixed ◽  
Flame Response ◽  
Dynamic Pressure Measurements

An experimental study was conducted to compare the relationship between self-excited and forced flame response in a variable-length lean premixed gas turbine (LPGT) research combustor with a single industrial injector. The variable-length combustor was used to determine the range of preferred instability frequencies for a given operating condition. Flame stability was classified based on combustor dynamic pressure measurements. Particle velocity perturbations in the injector barrel were calculated from additional dynamic pressure measurements using the two-microphone technique. Global CH* chemiluminescence emission was used as a marker for heat release. The flame’s response (i.e. normalized heat release fluctuation divided by normalized velocity fluctuation) was characterized during self-excited instabilities. The variable-length combustor was then used to tune the system to produce a stable flame at the same operating condition and velocity perturbations of varying magnitudes were generated using an upstream air-fuel mixture siren. Heat release perturbations were measured and the flame transfer function was calculated as a function of inlet velocity perturbation magnitude. For cases in this study, the gain and phase between velocity and heat release perturbations agreed for both self-excited and forced measurements in the linear and nonlinear flame response regimes, validating the use of forcing measurements to measure flame response to velocity perturbations. Analysis of the self-excited flame response indicates the saturation mechanism responsible for finite limit amplitude perturbations may result from nonlinear driving or damping processes in the combustor.

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