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Enhanced power density in hydrocarbon-compatible anode-supported solid oxide fuel cell facilitated by a functional anode catalyst layer
No full textIn the present study, solution combustion synthesis (SCS) is employed to prepare a hydrocarbon-compatible composite anode oxide powder containing nickel (Ni), copper (Cu), yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) (Ni0.9–Cu0.1–YSZ0.95–GDC0.05) through the single-step solution combustion method using two different fuels. The effect of fuel on the nature of the synthesized anode powder is established. Carburization studies are carried out on the synthesized anode powder to study the carbon-retarding ability. Phase stability and interface reactivity are studied by X-ray diffractometry and field emission scanning electron microscopy. The SCS-synthesized anode powder is used for the fabrication of electrolyte-supported solid oxide fuel cells (SOFCs). The fabricated SOFC single cells are characterized for their electrical and electrochemical performance. Based on their performance, it is realized that they can be used as an anode functional layer instead of the anode support. The SOFC containing the SCS-synthesized anode as the functional layer yields a high power density of 884 mW/cm2 in methane fuel at 800°C, which is higher than the reported power density of such cells. The electrode impedance and exchange current density are also derived for the SOFC
Experimental evaluation of elastic ring squeeze film dampers for small gas turbine engine
No full textSqueeze film dampers play a vital role in absorbing vibration energy in a rotor bearing system. The damper under study has an elastic ring with pedestals between bearing and stator dividing oil cavity into small oil pockets. This arrangement is different from conventional squeeze film damper where a single annular oil film is formed. This provides the required support stiffness as well as damping to the rotor. These types of dampers are called elastic ring squeeze film dampers (ERSFD) which are mainly used in high-speed small gas turbine engines by virtue of its compact design. There are very few literatures available to evaluate the damping offered by these SFDs. The main objective of this work is to determine the damping offered by ERSFD experimentally. For this study the rotor is designed to simulate the dynamics of a typical gas turbine engine. The rotor has to cross two rigid critical speeds within 18,000 rpm. The rotor response is measured under undamped (UND-without oil supply) and damped (D-with oil supply) conditions to evaluate the damper performance. The performance data is generated at three different oil temperatures (40, 70 and 100 ℃) under unbalanced load ranging from 2 to 8 g at 58.5 mm radius (UBR). This experimentation and performance analysis shows enhanced damping at critical speeds leading to the reduction in rotor vibrations after introducing ERSFD. The experimental data is further processed to calculate the amount of damping offered by ERSFD using rotor dynamic relations
Effect of Forward Splitter Plate Leading Edge Shape on the Cylinder Flow
No full textExperiments have been conducted on a cylinder with a forward splitter plate at Reynolds number of 5.33 × 104. Ten different splitter plate configurations are considered wherein the leading edge of the splitter plate is modified. The flow development on the splitter plate and on the cylinder has been examined using PIV. Static pressure on the cylinder surface and hot wire measurements in the cylinder wake have been carried out. A maximum of 57% increase in base pressure is observed with the use of splitter plate leading edge modification as compared to the simple cylinder case
Extremely high temperature stable nanometric scale multilayer spectrally selective absorber coating: Emissivity measurements at elevated temperatures and a comprehensive study on ageing mechanism
No full textSpectrally selective W/WAlSiN/SiON/SiO2 solar absorber coatings were sputter-deposited on stainless steel and silicon substrates. The optimized as-deposited sample exhibits a high solar absorptance of 0.955 and a low thermal emissivity of 0.10 at 82 °C. The coating exhibits a very low reflectance of 1.2% in the wavelength range of 0.5–1.5 μm in the solar spectrum. The spectral emissivity measurements at various operating temperatures and with varying emergence angles were investigated. Also, the impact of emissivity on the photothermal efficiency at different temperatures of the developed solar absorber coating was calculated. The calculated optical properties of the as-deposited sample exhibited low thermal emissivity of 0.157 (at 500 °C) and a high heliothermal efficiency of 89.5%. Angular reflectance measured at room temperature illustrates an insignificant change in the hemispherical and near normal emissivities of the samples. In addition to these studies, the ageing tests of the as-deposited samples at various operating temperatures were studied in detail. The thermal ageing tests of the samples in air and vacuum environments indicated excellent thermal stability at elevated temperatures, i.e., in air at 400 °C for 500 h, at 450 °C for 175 h and at 500 °C for 100 h, whereas, in a vacuum it was stable at 700 °C for 200 h. The top anti-reflection layers and the fine nano-multilayers of WAlSiN (W2N and AlSiN) prevent the inward diffusion of oxygen and thereby improve the overall thermal stability of the tandem absorbe
3D Finite Element Vibrational Analysis of T385 Turbine Rotor BLISK Using SAFE Diagram
No full textIntegrally bladed rotors (BLISK) are most stressed part of aircraft engines due to high rotational speeds, elevated temperatures and pressures. Turbine blades fail mainly due to fatigue under alternating stresses resulting from vibration of rotor systems. Non-uniform pressure field is experienced by turbine BLISK due to interaction of stator and rotor blades which acts as a source of excitation during turbine operation. The number of stator blades dictates the occurrence of resonance in the rotor BLISK during steady-state operation. Therefore, it is necessary to design a mechanically feasible rotor with respect to stator and verify its modal and harmonic response to ensure its resonance-free operation. Design and development of T385 turbine stage for 1 kN small gas turbine engine are carried out in Propulsion Division, CSIR-NAL. The dynamic behaviour of T385 turbine rotor BLISK is evaluated for vibration reliability. This paper presents vibrational analysis of the T385 turbine rotor BLISK using finite element technique to evaluate critical nodal diameter, critical frequencies and response in engine environment. The turbine speed is 50,500 rpm at the engine design point based on the inlet temperature. Detailed vibration analysis of T385 turbine is carried out using FEA to plot Campbell and SAFE diagrams. The critical nodal diameter extracted from plotted SAFE diagram is 19, which is very well agreeing with Bertini analytical formulae. The Campbell diagram is plotted for T385 turbine at critical nodal diameter of 19. The obtained critical speed from this Campbell diagram is 33,000 rpm, which ensures the rotor is safe in the operating conditions
Control of shock-induced vortex breakdown on a delta-wing-body configuration in the transonic regime
No full textShock-induced vortex breakdown, which occurs on the delta wings at transonic speed, causes a sudden and significant change in the aerodynamic coefficients at a moderate angle-of-attack. Wind-tunnel tests show a sudden jump in the aerodynamic coefficients such as lift force, pitching moment and centre of pressure which affect the longitudinal stability and controllability of the vehicle. A pneumatic jet operated at sonic condition blown spanwise and along the vortex core over a 60° swept delta-wing-body configuration is found to be effective in postponing this phenomenon by energising the vortical structure, pushing the vortex breakdown location downstream. The study reports that a modest level of spanwise blowing enhances the lift by about 6 to 9% and lift-to-drag ratio by about 4 to 9%, depending on the free-stream transonic Mach number, and extends the usable angle-of-attack range by 2°. The blowing is found to reduce the magnitude of unsteady pressure fluctuations by 8% to 20% in the aft portion of the wing, depending upon the method of blowing. Detailed investigations carried out on the location of blowing reveal that the blowing close to the apex of the wing maximises the benefits
Sol-gel based organic-inoganic hybrid coatings for corrosion protection of aerospace aluminium alloy
No full textAluminum alloy 2024 is the most commonly used aircraft alloy because of its high damage tolerance, relatively
high tensile strength and high strength to weight ratio. These properties are achieved by appropriate alloying
with copper and magnesium which, in addition to strengthening phases, form copper -and magnesium-
containing constituent particles. However, the presence of these alloying elements makes the alloy
susceptible to localized corrosion making it impossible to use it without prior application of
a corrosion protection system. Historically, the corrosion protection systems are based on Cr(VI) compounds which are now restricted due to
their carcinogenic nature. In this direction, extensive research is pursued on organic–inorganic hybrid silane coatings to replace the toxic Cr (VI) component. In the present study, silica alumina hybrid sol -gel coatings are developed and explored for anticorrosion properties using electrochemical techniques and industry
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standard tests. Apart from the basic coating, co
rrosion inhibitors are explored to impart active protection to the alloy. The ability of silica
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alumina coating to act as reservoir for storage of
inhibitors is investigated. The results confirm that coatings containing cerium nitrate inhibitor in an optimum concentration offer superior protection to the surface. X-ray photoelectron and Raman spectroscopy studies provide evidence for the migration of cerium ions from the coating. Improved corrosion protection is attributed to the combined effect of the barr
ier nature of the coating and the corrosion inhibiting nature of Ce3+ ions. Further, the role of morphology of the inhibitor when used in the form of solid particles instead of salts is studied. The compatibility of the developed sol -gel layer with subsequ
ent top layers of the paint system is also evaluated
Effect of dopants on electrical properties of BCT-BZT lead free piezo ceramics: a review
No full textLead free piezo materials are becoming popular as the world is conscious about toxicity of PbO present in PZT. As a result, lot of R&D efforts are made in last two decades to find out suitable lead free piezo ceramics as effective as PZT. There are many lead free piezo systems explored. Among them, BZT-BCT is more promising due to its high piezoelectric coefficients. This system is well researched by modifying its structure with a large number of dopants. In this paper, an effort has been made to review the effect of various dopants on electrical properties of BCT-BZT systems
Mitigation of cutting point deviation by generating provisional corrugations during milling of thin walls
No full textThe nominal cutting contour for the thin wall deviates in response to the cutting forces during the end milling process. Elimination of mass in the milling process links to loss of stiffness, which favors the wall to deflect and promote error. This article proposes a novel way of generating rigidity during the process of milling. The tool paths were drafted to mill away mass in the central region and make corrugations at the edges simultaneously. This approach mitigated the thin wall deformation. Comparison experiments were conducted to analyze between open wall conventional type (OWC) and end corrugated pillar type (ECP). Force polygons were constructed to evaluate the effectiveness of machining. The experiments resulted in 36% more effectiveness in up milling and with 93% in down milling. An increase in the cutting effectiveness exhibited error-free and minimized cutting point deviation at the top of the wall. Eventually, the error diminished as the tool traversed to the bottom edge of the wall
Development of LabVIEW based mass flow plug control for wind tunnel application
No full textIn order to study the intake characteristics of any air intake model in a wind tunnel, the mass flow through the intake duct needs to be simulated accurately. This can be done by a precise control of the mass flow plug at the downstream end of the intake model. In this work, an existing mass flow plug which is fixed to a DC motor is used and is moved axially at different positions in order to simulate the pressure ratios across the plug and thereby characterise the different engine parameters like total pressure recovery, total pressure distortion etc. This paper presents the development of a new NI LabVIEW based control system for the precise control of the mass flow plug during the testing of air intake model. This system can be used for continuous mode, step mode or preposition modes of mass flow plug operation. The control system is validated by conducting static tests of a typical air intake model at High Speed combustor test facility