Turbocoating (Italy)

Abstract The leakage flow through a traditional labyrinth seal reduces the compressor capacity of an oil-free magnetic bearing centrifugal compressor. Also, the super-heated leakage flow pollutes the downstream coolant flow, affecting motor cooling. A novel design is introduced to utilize the pressure loss across the seal by injecting liquid refrigerant near the seal inlet. The liquid-injected seal also functions as an expansion valve, producing low-temperature wet vapor at the seal exit. The wet vapor is projected to be utilized for motor cooling. A multiphase numerical simulation is performed to quantify the compressor performance of the liquid-injected seal and traditional seal under adiabatic conditions. The numerical simulation utilizes a Eulerian-Eulerian approach with an equilibrium phase change model. This study evaluates the compressor performance at three-speed lines: N1, N2, and N3. The base case results are validated with the experimental findings, with a maximum error of 3% in compressor efficiency. The local distribution of vapor mass fraction, pressure, and temperature are analyzed. The numerical results show that the leakage flow in the liquid-injected seal is reduced by 95%, and the compressor capacity is increased by 2.9%.

Significance: A systematic approach to develop experts-based recommendations could have a favorable impact on clinical problems characterized by scarce and low-quality evidence as heel pressure ulcers.Recent Advances: A systematic approach was used to conduce a formal consensus initiative. A multidisciplinary panel of experts identified relevant clinical questions, performed a systematic search of the literature, and created a list of statements. GRADE Working Group guidelines were followed. An independent international jury reviewed and voted recommendations for clinical practice. Consent was developed according to Delphi rules and GRADE method was used to attribute grade of strength.Critical Issues: The extensive search of the literature retrieved 42 pertinent articles (26 clinical studies, 7 systematic reviews or meta-analysis, 5 other reviews, 2 consensus-based articles, and 2 in vitro studies). Thirty-five recommendations and statements were created. Only 1 of 35, concerning ankle–brachial pressure index reliability in diabetic patients, was rejected by the panel. No sufficient agreement was achieved on toe brachial index test to rule out the orphan heel syndrome, removing dry eschar in adult patients without vascular impairment, and using an antimicrobial dressing in children with infected heel pressure injuries. Eleven recommendations were approved with a weak grade of strength. Experts strongly endorsed 20 recommendations. Offloading, stages I and II pressure injuries, and referral criteria were areas characterized by higher level of agreement.Future Directions: We believe that the results of our effort could improve practice, especially in areas where clear and shared opinions emerged. Barriers and limits that could hinder implementation are also discussed in the article.

Abstract Thermal barrier coatings (TBCs) are one of the most promising applications for suspension thermal spraying. By using a liquid feedstock, coating morphologies close to the columnar-like structure of electron-beam physical vapor deposition (EB-PVD) are possible. Additionally, vertically cracked TBC coatings (VC-TBC) have shown a great potential for industrial applications. In this work, we will analyze the process window for TBCs produced by using suspension spraying. Commercially available alcohol- and water-based YSZ suspensions have been processed using suspension atmospheric plasma spraying (S-APS) and suspension high-velocity oxy-fuel (S-HVOF) to achieve both columnar-like and VC morphologies. The coatings have been analyzed and compared in terms of microstructure, phase composition, bond strength and thermal cycling performance. Additionally, the suitability of S-APS and S-HVOF TBCs for industrial applications will be discussed, as well as which actions are needed to increase its competitiveness.

Hot section gas turbine parts need protection against oxidation and hot corrosion. The essential element is Al to build the protective Al2O3. Al can be applied on the gas path surfaces by overlay techniques or by diffusion of Al into the base material — the “aluminizing”. Aluminizing can be done by slurry, pack cementation, out of pack, or by “pure” CVD. Additional elements can be added to the aluminide. The different techniques are discussed under the aspects of advantage/disadvantage, limits and possible coating structures.

Abstract In order to improve gas turbine performance it is possible to decrease back flow gases in the high temperature combustion region of the turbo machine reducing shroud/rotor gap. Thick and porous TBC systems and composite CoNiCrAlY/Al2O3 coatings made by Air Plasma Spray (APS) and composite NiCrAlY/graphite coatings made by Laser Cladding were studied as possible high temperature abradable seal on shroud. Oxidation and thermal fatigue resistance of the coatings were assessed by means of isothermal and cyclic oxidation tests. Tested CoNiCrAlY/Al2O3 and NiCrAlY/graphite coatings after 1000 hours at 1100°C do not show noticeable microstructural modification. The oxidation resistance of new composite coatings satisfied Original Equipment Manufacturer (OEM) specification. Thick and porous TBC systems passed the thermal fatigue test according to the considered OEM procedures. According to the OEM specification for abradable coatings the hardness evaluation suggests that these kinds of coatings must be used with abrasive tipped blades. Thick and porous TBC coating has shown good abradability using tipped blades.

Abstract The most commonly used structural materials for blades and other high temperature components of gas turbines are nickel superalloys such as Inconel 738, MAR M247M or Hastelloy. Thermal barrier coatings (TBCs) are widely used on these substrates as protection against high temperatures and oxidation. A TBC system consists of a top coat of yttria partially stabilized zirconia deposited by air plasma spray and an underlying bond coat (usually MCrAlY, where M is Ni, Co or a combination of both). MCrAlYs are normally deposited by thermal spray processes such as air plasma spray, vacuum plasma spray (VPS/LPPS) or high velocity oxygen fuel (HVOF). In general, the adhesion of the whole thermal barrier system is strongly dependent on the surface preparation of the substrate and it is generally believed that a certain degree of roughness promotes better adhesion. OEM’s (Original equipment manufacturer) procedure for preparation of substrates and analysis have been reviewed and considered as basis of this work. The scope of this work is to set up a new cleaning methodology in order to obtain a completely pollution free surface to be coated afterwards with HVOF or VPS/LPPS. The properties of this new methodology have been compared with standard surface preparation techniques such as blasting with corundum and silicon carbides. The obtained samples have been analysed by means of metallography and chemical composition of the interface in order to measure the interfacial pollution between substrate and coating. Finally adhesion of MCAlY coating have been tested and compared with specification of the main OEMs.

One of the most important factors determining the degree of tissue interaction of an implanted device is the property of its surface. Thus, great importance is given to chemical and morphological characteristics of biomaterial surfaces to improve biocompatibility, cell migration, proliferation and differentiation, mechanical stability and endogenous tissue ingrowth. In order to obtain new and healing stimulating properties, it is possible to apply a coating or more generally a surface treatment to the surface of a prosthetic device. One of the most versatile methods for coating is thermal spray technology. This paper considers the principle of thermal spray processes and their application in the biomedical field, namely the coatings used for orthopedic prostheses and dental implants. Among thermal spray processes, plasma spray as well as High Velocity Oxygen Fuel (HVOF) processes will be particularly considered and their most important aspects will be illustrated.