Simultaneous measurement of pressure and temperature in a supersonic ejector using FBG sensors

Abstract

In this work, we have demonstrated the use of Fiber Bragg Grating (FBG) sensors for simultaneous measurement of wall static pressure and temperature in a supersonic ejector. Supersonic ejectors are ground based high speed aerodynamic test facilities characterized by harsh conditions such as high pressure and temperature gradients. FBG based sensor setup was developed consisting of pressure measuring bare FBG and specially designed pressure-insensitive FBG temperature probe that could be mounted on the wall of the supersonic ejector. The FBG temperature probe was used for temperature measurement as well as temperature compensation of pressure measuring FBG sensor. Wall static pressure measurements in the supersonic ejector were carried out at different tank pressures and Mach number flows. The FBG pressure measurements were validated with that of standard piezoresistive based sensor measurements. Both the responses were found to match closely with FBG sensor having a faster response time and higher pressure resolution. Fluid structure interaction simulation was carried out in Comsol Multiphysics to understand the interaction of high speed turbulent flow on the fiber based FBG sensor. The FBG strain profile due to flow-induced stress and its dependence on flow pressure was studied. A detailed analysis of effect of preceding fiber length on FBG pressure measurement was carried out. FBG sensors, owing to their miniature size, ability to withstand harsh environments and multi parameter sensing capability can be used in ground-based aerodynamic test facilities with minimum intrusion to the flow.

Sensor for Simultaneous Measurement of Temperature and Humidity Based on a Chirped Fiber Bragg Grating Partially Bonded With Thick Polyimide Film

“…When broadband light from the source propagates through the grating, the maximum light intensity reflected occurs at the FBG center wavelength λ, which then can be defined as Eq. ( 1) [15]. The effective refractive index, 𝑛 𝑒𝑓𝑓 , and the grating period, 𝛬, are affected by the measurand, such as strain or temperature, resulting in a wavelength shift from the initial value, 𝜆.…”

Embedded measurement of process monitoring in melt-cast explosive based on distributed optical fiber sensing and numerical verification

“…In recent years, DOFS has been applied in aircraft structures [15], civil engineering [16], medical devices [17], structural health monitoring [18] and other fields [19][20][21]. As a sensor, optical fiber has many key advantages over other traditional sensors, such as large range, adaptability to harsh environments, high embeddability, sensitivity to a wide range of parameters, resistance to electromagnetic and voltage, etc [22].…”

Dual-FBG arrays hybrid measurement technology for mechanical strain, temperature, and thermal strain on composite materials

“…Electromechanical sensors can not provide reliable monitoring for spacecraft during service. Unlike electromechanical sensors, FBG sensors exhibit many advantages, such as miniature size, corrosion resistance, immunity to EMI, and multiplexing capability [9]. Therefore, FBG sensors effectively monitor spacecraft deformation to increase transport efficiency and meet the need for lightweight development for new-generation spacecraft.…”

“…Generally, some strategies such as special package design of FBG sensors and combination configuration of FBG sensors, have been presented to distinguish the cross-sensitivity effect between strain and temperature [9][10][11][12][13][14][15][16][17]. A number of similar techniques for simultaneously measuring temperature and strain have been proposed [9][10][11][12], including the use of two types of FBGs, such as a pair of etched and un-etched polymer FBG functions as a sensor [11], the combination of a FBG and two PM-PCF with different coatings [10], a FBGembedded CFRP rod [12]. While these methods may be able to distinguish a cross-sensitivity between strain and temperature, most of them require the use of different fibre types and FBGs or any extrinsic special techniques [11].…”

“…Since the use of more than one fibre element increases the cost of the system and complicates the fabrication of the sensor, these factors are severely restricted for use in spacecraft. Besides, the existing studies primarily focus on decoupling double physical parameters [9,[13][14][15][16][17], such as mechanical strain and temperature or thermal strain and temperature. Especially in large temperature gradient scenarios, ignoring the effect of thermal strain on the host material would cause non-negligible measurement errors in the decoupling of strain (strain in a broad sense) and temperature.…”