Evaluation of Kerosene Fuelled Scramjet Combustor using a Combination of Cooled and Uncooled Struts

The scramjet combustor a vital component of scramjet engine has been designed by employing fuel injection struts. Several experimental studies have been carried out to evaluate the propulsive performance and structural integrity of the in-stream fuel injection struts in the connect-pipe test facility. As the mission objective of hypersonic demonstrator is to flight test the scramjet engine for 20 s duration, in-stream fuel injection struts which are designed as heat sink devices encounter hostile flow field conditions especially in terms of high thermal and high convective loads in the scramjet combustor. To circumvent these adverse conditions, materials like Niobium C-103 and W-Ni-Fe alloys have been used for the construction of struts and a number of tests have been carried out to evaluate the survivability of the in-stream fuel injection struts in the scramjet combustor. The results thus obtained show that the erosion of leading edges of the Stage-II fuel injection struts in the initial phase and subsequently puncturing of the fuel injection manifold after 10-12 s of the test are noticed, while the other stages of the struts are found to be intact. This deteriorating leading edges of Stage-II struts with respect to time, affect the overall propulsive performance of the combustor. To mitigate this situation, Stage-II struts have been designed as cooled structure and other Stages of struts are designed as un-cooled structure. Material of construction of struts used is Nimonic C-263 alloy. This paper highlights the results of the static test of the scramjet combustor, which has been carried out at a combustor entry Mach number of 2.0, total temperature of 2000 K, with an overall kerosene fuel equivalence ratio of 1.0 and for the supersonic combustion duration of 20 s. Low back pressure has been created at the exit of the scramjet combustor using ejector system to avoid flow separation.Visual inspection of the fuel injection struts after the test revealed that all the Struts are found to be thermo-structurally safe in the combustor environment except for minor erosion of the leading edges of the struts. Stage-II struts made of two-passage cooled configuration are found to be thermo-structurally safe. Although other stages of struts used in the test are of un-cooled configuration, they too are found to be safe and intact. This demonstrates the fact that they experience thermally benign flow conditions compared to Stage-II struts in the scramjet combustor.Defence Science Journal, 2014, 64(1),  DOI:http://dx.doi.org/10.14429/dsj.64.273

Wavy ribbon formation during planar flow melt spinning process – a 3D CFD analysis

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Planar flow melt spinning is a rapid solidification process used to produce amorphous ribbons for transformer core applications, etc. Molten metal is ejected via a nozzle onto a rotating cooling wheel for rapid solidification which bypasses crystallization. The study of surface feature (topography) is a measure of surface quality of the ribbon obtained. Experiments often result in formation of amorphous ribbons with different surface topographies such as wavy, dimple, herringbone, streak, etc which are imperfections, leading to non-uniform magnetic properties. An amorphous ribbon of polished surface topography is preferred for better performance of the magnetic core in the transformers. Hence to understand this phenomenon, a 3D numerical simulation of ribbon formation is performed to predict the ribbon surface. The computational domain consists of the space between the nozzle (from which the molten metal issues) and the rotating cooling wheel on which the molten metal falls, solidifies instantly and forms an amorphous strip. The Computational domain is extended on both sides of the nozzle to include the surrounding atmosphere. The solid cooling wheel is modeled as a curved wall boundary at constant temperature. A CFD technique called volume of fluid is used to simulate the two phase flow of melt in the air domain over the wheel surface. The conservation equations of Mass, Energy and Momentum are solved under transient conditions. Temperature dependent viscosity relation is used for the melt to employ the viscous changes in the ribbon flow. For a set of process conditions, wavy ribbon pattern is observed at lower melt ejection temperatures. By increasing the ejection temperature keeping other process conditions constant, polished ribbon is obtained. Upstream meniscus is observed to play an important role in the surface topography of the ribbon. Topographical changes in the ribbon are due to momentum transport mechanism during melt flow, which in turn depends on the surface tension and temperature dependent viscosity. Hence, a variation in ejection temperature leads to changes in surface topography of the ribbons. 3D model and simulations presented in the study are useful in predicting the surface topography of the ribbon for a set of process conditions selected for experimentation.cf201

Experimental Investigations of Hydrocarbon Fueled Scramjet Combustor by Employing High Temperature Materials for the Construction of Fuel Injection Struts

ABSTRACT For the Hypersonic Technology Demonstrator Vehicle (HSTDV) programme half-width strut based scramjet combustor has been designed, developed and tested for the short durations (5 s) as well as for the long durations (20 s) using various materials for the construction of fuel injection struts. Extensive experimental investigations have been carried out to identify suitable material for the long duration (20 s) tests. Niobium C-103 alloy and W-Ni-Fe alloy materials have been used for the construction of fuel injection struts and they have been employed in two different tests. In the first test struts made of Niobium alloy is used and in the second test struts made of W-Ni-Fe alloy is used. It is inferred from the results of the static tests for the 20 s test duration that the leading edges of the struts are eroding due to high thermal load, shear force and oxidizing environments in the five-strut scramjet combustor configuration. The failure of the struts is noticed in the Stage-II injection of the scramjet combustor. The thermo-structural failure of the stage-II fuel injection struts in the scramjet combustor in both the tests has detrimental effect on the performance of the combustor. In the case of Niobium C-103 alloy struts, erosion of the leading edges is found to be severe compared to W-Ni-Fe alloy struts. Hence, the total pressure loss in the former is found to be more compared to the latter. In the first test (Niobium struts used) the flow separation is occurring earlier compared to the second test (W-Ni-Fe struts employed). This is indicative of the onset of the severe leading edges erosion of Niobium C-103 alloy struts compared to W-Ni-Fe alloy struts resulted in more skin friction drag and hence the flow separation at a shorter length. Struts made of W-Ni-Fe alloy seem to be promising candidate material compared to Niobium C-103 alloy. Subsequent tests carried out by employing struts made of W-Ni-Fe alloy divulged that the powder metallurgy route to realise the W-Ni-Fe alloy plate is unable to deliver/impart consistent mechanical properties in all the directions of the plate i.e., anisotropy is prevailing. On this front, it is found that the material developed at this juncture is found to be unsuitable for the scramjet application. To circumvent such scenario two strategies have been proposed for the realization of fuel injection elements. Hypersonic, Scramjet, Strut, NOMENCLATURE H = height of the combustor P = pressure T = temperature = equivalence ratio SUBSCRIPTS f = fuel i = inlet t = stagnation condition w = wall wd = wedge Keywords

2-D analytical study of employment of thermal barrier coatings to evaluate the performance of actively cooled panels for air breathing engines

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Hypersonic vehicles operate at high flight Mach numbers exposing the airframe and engine structures to high heat loads which are quite severe in the combustor part of the high-speed air breathing engine. In order to withstand high heat loads experienced in the combustor region of the engine during hypersonic flight, actively cooled panels are employed. Herein, a fuel before being injected into the combustor serves as a coolant and is made to flow through the combustor heat exchanger panels such that the material and coolant temperatures are maintained below their critical limits. A few of the candidate materials considered for the active panels of the engine are Nb alloy Cb 752, Ni alloy Inconel X-750, and CSiC. To enhance the heat withstanding capacity of these materials, low thermal conductivity thermal barrier coatings (TBC) are employed. Currently Yttria-Stabilized Zirconia (YSZ) material and ceramic materials are being used as popular TBC materials because of their very low thermal conductivity and high phase stability. In this analytical study, thermal properties of air-plasma-sprayed zirconia based lanthanum zirconate (La2Zr2O7) – LZ- coatings were employed in the investigations. Lanthanum-cerium oxide (La2Ce2O7) –LC- is considered as a new candidate material for TBCs because of its low thermal conductivity and high phase stability. With the use of La2Ce2O7 and La2Zr2O7 as TBC materials, the difference in the weight of the active panel material and the heat gained by the fuel are nearly identical as compared to active panel material coated with YSZ TBC. Results showed that the effect of TBC thickness on the weight of the optimised actively cooled panel is negligible, because of very small TBC layer thickness ranging from 0.5 to 3.0 mm and nearly identical thermal properties of the TBC’s. Results showed that Inconel X-750 is capable of sustaining high heat transfer coefficients with fuel/coolant heat gain well below fuel coking temperature with moderate weight to area ratio.dc201

Heat transfer enhancement in natural convection using water based Fe3O4 nanofluid inside a square cavity

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Natural convection heat transfer has many applications, especially in the field of solar thermal applications, electronic cooling etc., Heat transfer enhancement techniques in natural convection deals essentially with addition of fins of various configuration. Since the introduction of nanofluids by Choi et al [1], nanofluids continue to be considered as one of the sought after options of heat transfer enhancement. This is due to the excellent improvement in heat transfer characteristics due to the addition of nanosized solid particles into base fluids such as water, ethylene glycol etc., in the present study, an effort is made to study the heat transfer enhancement inside a square cavity when the water is seeded with magnetic Fe3O4 nanoparticles using numerical experiments. The volume fractions considered in the analysis range from 0.1% to 0.6%. It is observed that the enhancement is less than 10% for 0.1% and 0.3% volume fractions considered in the analysis for the range of Rayleigh numbers considered.dc201

The biomechanical role of periodontal ligament in bonded and replanted vertically fractured teeth under cyclic biting forces

After teeth are replanted, there are two possible healing responses: periodontal ligament healing or ankylosis with subsequent replacement resorption. The purpose of this study was to compare the fatigue resistance of vertically fractured teeth after bonding the fragments under conditions simulating both healing modes. Thirty-two human premolars were vertically fractured and the fragments were bonded together with Super-Bond C&B. They were then randomly distributed into four groups (BP, CP, CA, BA). The BP and CP groups were used to investigate the periodontal ligament healing mode whilst the BA and CA groups simulated ankylosis. All teeth had root canal treatment performed. Metal crowns were constructed for the CP and CA groups. The BP and BA groups only had composite resin restorations in the access cavities. All specimens were subjected to a 260 N load at 4 Hz until failure of the bond or until 2×106 cycles had been reached if no fracture occurred. Cracks were detected by stereomicroscope imaging and also assessed via dye penetration tests. Finally, interfaces of the resin luting agent were examined by scanning electron microscope. The results confirmed that the fatigue resistance was higher in the groups with simulated periodontal ligament healing. Periodontal reattachment showed important biomechanical role in bonded and replanted vertically fractured teeth

Antimicrobial activity of ProRoot MTA in contact with blood

Dental materials based on Portland cement, which is used in the construction industry have gained popularity for clinical use due to their hydraulic properties, the interaction with tooth tissue and their antimicrobial properties. The antimicrobial properties are optimal in vitro. However in clinical use contact with blood may affect the antimicrobial properties. This study aims to assess whether antimicrobial properties of the Portland cement-based dental cements such as mineral trioxide aggregate (MTA) are also affected by contact with blood present in clinical situations. ProRoot MTA, a Portland cement-based dental cement was characterized following contact with water, or heparinized blood after 1 day and 7 days aging. The antimicrobial activity under the mentioned conditions was assessed using 3 antimicrobial tests: agar diffusion test, direct contact test and intratubular infection test. MTA in contact with blood was severely discoloured, exhibited an additional phosphorus peak in elemental analysis, no calcium hydroxide peaks and no areas of bacterial inhibition growth in the agar diffusion test were demonstrated. ProRoot MTA showed limited antimicrobial activity, in both the direct contact test and intratubular infection test. When aged in water ProRoot MTA showed higher antimicrobial activity than when aged in blood. Antimicrobial activity reduced significantly after 7 days. Further assessment is required to investigate behaviour in clinical situations.ERDF (Malta) for the financing of the testing equipment through the project: “Developing an Interdisciplinary Material Testing and Rapid Prototyping R&D Facility” (Ref. no. 012)

Working with Commercially Available Quantum Dots for Immunofluorescence on Tissue Sections

Quantum dots are semiconductor fluorescent nanocrystals that exhibit excellent characteristics compared with more commonly used organic fluorescent dyes. For many years quantum dot conjugated products have been available in multiple forms for fluorescence imaging of tissue sections under the trademark name Qdot®. They have much increased brightness, narrow emission spectrum, large Stokes shift and photostability compared with conventional organic fluorescent dyes, which together make them the fluorophores of choice for demanding requirements. Vivid Qdots are recent replacements for original Qdots, modified to improve brightness, however this has affected the fluorescence stability in commonly used conditions for immunohistochemistry. We present here our investigation of the stability of original and Vivid Qdots in solution and in immunohistochemistry, highlight the potential pitfalls and propose a protocol for stable and reliable multiplex staining with current commercially available original and Vivid Qdots

Review of nanomaterials in dentistry: interactions with the oral microenvironment, clinical applications, hazards, and benefits.

Interest in the use of engineered nanomaterials (ENMs) as either nanomedicines or dental materials/devices in clinical dentistry is growing. This review aims to detail the ultrafine structure, chemical composition, and reactivity of dental tissues in the context of interactions with ENMs, including the saliva, pellicle layer, and oral biofilm; then describes the applications of ENMs in dentistry in context with beneficial clinical outcomes versus potential risks. The flow rate and quality of saliva are likely to influence the behavior of ENMs in the oral cavity, but how the protein corona formed on the ENMs will alter bioavailability, or interact with the structure and proteins of the pellicle layer, as well as microbes in the biofilm, remains unclear. The tooth enamel is a dense crystalline structure that is likely to act as a barrier to ENM penetration, but underlying dentinal tubules are not. Consequently, ENMs may be used to strengthen dentine or regenerate pulp tissue. ENMs have dental applications as antibacterials for infection control, as nanofillers to improve the mechanical and bioactive properties of restoration materials, and as novel coatings on dental implants. Dentifrices and some related personal care products are already available for oral health applications. Overall, the clinical benefits generally outweigh the hazards of using ENMs in the oral cavity, and the latter should not prevent the responsible innovation of nanotechnology in dentistry. However, the clinical safety regulations for dental materials have not been specifically updated for ENMs, and some guidance on occupational health for practitioners is also needed. Knowledge gaps for future research include the formation of protein corona in the oral cavity, ENM diffusion through clinically relevant biofilms, and mechanistic investigations on how ENMs strengthen the tooth structure

Energy savings in a hermetic compressor : reducing heat losses

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.Energy is becoming dearer. Saving power of domestic appliances is not only for cost benefits but a social obligation and sustaining environment. Hermetic compressor being the heart of an air conditioner, in it's function and also in the power consumption, it is continuously redesigned for increased efficiency, capacity and noise. Two terms get optimised in improving efficiency the capacity delivered and the power consumed. Noise is independently evaluated. This study helped in identifying root causes of losses and providing corrections to improve the efficiency of fixed and variable frequency compressors to our customer's satisfaction.ej201