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Study of inline-slot ejector diffuser under varying ambient conditions: A passive infrared suppression device for ships

Singh L., Singh S. N., Sinha S. S.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14, no. 2

477--482

EN

Passive infrared (IR) suppression device, commonly known as ejector diffuser, is an integral part of the defence system of a ship. The definitive role of passive IR suppressor to counter the IR tracking and locking of the ship has made them indispensable for any combat marine. The gas turbine exhaust gases are the leading heat source on a ship. The exhaust temperature of the gases ranges between 650K-850K. At such temperatures, the ship can be easily detected by the enemy through IR imaging. The role of the ejector diffuser is to (i) lower the gas turbine exhaust gases temperature to the limits (< 450K) such that the IR locking of the marine can be avoided, and (ii) recover static pressure such that the engine performance of the gas turbine is not affected. Ejector diffuser has the ability to entrain ambient air and allow mixing it with the exhaust gases thereby, lowering the temperature of the exhaust gases. However, the mixed exhaust gases temperature depends on the ambient air temperature which under extreme conditions can fluctuate from 273K to 323K. This temperature range can affect the temperature characteristics of an ejector diffuser. The present study undertakes the effect of ambient temperature on the performance of inline-slot ejector diffuser. The ambient temperature (T0) has been varied in the range 273K ≤ T0 ≤ 323K in the step of 10K. It has been found that the mass entrainment increases (≈ 8%) as the ambient temperature decreases. The core temperature at the exit decreases, from 457.58 K to 417.75K, with a decrease in the ambient temperature. However, no significant changes in static pressure recovery.

2

Investigation of microwave and electrical characteristics of Co-Zr substituted M-type Ba-Sr hexagonal ferrite

Singh L., Malhotra J., Singh C., Narang S. B., Chandra M.

Materials Science Poland

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2015

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Vol. 33, No. 2

335--339

EN

Microwave characteristics of M-type hexagonal ferrite, Ba-0.Sr-5(0).5CoxZrxFe(12-2x) O-19 (x = 0.0 to 1.0 in steps of 0.2), have been investigated as a function of frequency and substitution at X-band. The microwave absorption has been investigated using absorber testing device method. The static I-V characteristics have been studied as a function of substitution. The results show maximum microwave absorption at higher substitution. The static current exhibits ohmic behavior from 0 to 3 V and exponential trend from 3 to 4.8 V. The microstructure influences both microwave and electrical properties. The ferrite compositions for different electromagnetic applications are also suggested by measuring the microwave absorbed, transmitted and reflected power.

3

Reflection of plane waves from a free surface of a generalized magneto-thermoelastic solid half-space with diffusion

Singh B., Singh L., Deswal S.

Journal of Theoretical and Applied Mechanics

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2014

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Vol. 52 nr 2

385--394

EN

Green-Naghdi’s theory of generalized thermoelasticity is applied to study the reflection of P and SV waves from the free surface of a magneto-thermoelastic solid half-space. The boundary conditions are satisfied by appropriate potential functions to obtain a system of four non-homogeneous equations in reflection coefficients. The reflection coefficients depend upon the angle of incidence of P and SV waves, magnetic field, thermal field, diffusion parameters and other material constants. The numerical values of the modulus of the reflection coefficients are shown graphically with the angle of incidence of P and SV waves. The effect of magnetic field is observed significantly on various reflected waves.