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At least 379 records · Page 21Linked to original sources
PubMed2001

Heat transfer technology for internal passages of air-cooled blades for heavy-duty gas turbines.

The present review paper, although far from being complete, aims to give an overview about the present state of the art in the field of heat transfer technology for internal cooling of gas turbine blades. After showing some typical modern cooled blades, the different methods to enhance heat transfer in the internal passages of air-cooled blades are discussed. The complicated flows occurring in bends are described in detail, because of their increasing importance for modern cooling designs. A short review about testing of cooling design elements is given, showing the interaction of the different cooling features as well. The special focus of the present review has been put on the cooling of blades for heavy-duty gas turbines, which show several differences compared to aero-engine blades.

Journal Article↗
PubMed2001

Selection of a turbine cooling system applying multi-disciplinary design considerations.

The presented paper describes a multi-disciplinary cooling selection approach applied to major gas turbine engine hot section components, including turbine nozzles, blades, discs, combustors and support structures, which maintain blade tip clearances. The paper demonstrates benefits of close interaction between participating disciplines starting from early phases of the hot section development. The approach targets advancements in engine performance and cost by optimizing the design process, often requiring compromises within individual disciplines.

Journal Article↗
PubMed2001

Experimental investigation of film cooling flow induced by shaped holes on a turbine blade.

The present study is the second half of a piece of work carried out in collaboration with SNECMA. It investigates shaped hole film cooling, numerically and experimentally. The aim of this paper is the experimental analysis of shaped hole film cooling on a large scale turbine blade (1.4 m chord). The test section is a large scale turbine inlet guide vane cascade. The test airfoil is equipped with a row of nine 50 degrees sloped shaped holes. They are located on the suction side at 20% of the curvilinear length of the blade from the stagnation point. The inlet film cooling hole diameter is 12 mm. The jet flow is heated to 55 degrees C above the crossflow temperature. Velocity and temperature field measurements have been done to obtain mean and fluctuating values. The results are compared to those obtained by Béral on the same experimental apparatus and in the same test conditions, for a row of cylindrical holes.

Journal Article↗
PubMed2002

Thermal barrier coatings for gas-turbine engine applications.

Hundreds of different types of coatings are used to protect a variety of structural engineering materials from corrosion, wear, and erosion, and to provide lubrication and thermal insulation. Of all these, thermal barrier coatings (TBCs) have the most complex structure and must operate in the most demanding high-temperature environment of aircraft and industrial gas-turbine engines. TBCs, which comprise metal and ceramic multilayers, insulate turbine and combustor engine components from the hot gas stream, and improve the durability and energy efficiency of these engines. Improvements in TBCs will require a better understanding of the complex changes in their structure and properties that occur under operating conditions that lead to their failure. The structure, properties, and failure mechanisms of TBCs are herein reviewed, together with a discussion of current limitations and future opportunities.

Journal Article↗
PubMed1993

Evaluation of the VMM turbine for spirometry in the applied physiology laboratory.

The volume measurement module turbine (VMM) was evaluated in 51 subjects for spirometry in applied physiology against the Stead-Wells spirometer (SW) and Wright peak flow meter (WM). The volume and flow ranges (VMM) were, FEV1 1.32 to 3.94 L (mean 2.62, confidence interval [CI] 2.46 to 2.78); forced vital capacity (FVC) 1.97 to 5.06 L (mean 3.50, CI 3.29 to 3.71); and peak expiratory flow rate (PEFR) 290 to 624 L.min-1 (mean 434, CI 407 to 461). The mean difference for FEV1 was 0.09 L (CI 0.05 to 0.14), FVC 0.04 L (CI -0.02 to 0.10), and PEFR 18.0 L min-1 (CI 8.7 to 27.3) less than SW or WM. Bias with FEV1 and FVC was not significant, though PEFR demonstrated a significant proportional error. The repeatability coefficients for FEV1 and FVC were 0.18 and 0.20, comparable to the SW; but for PEFR they were greater, 58.4 versus 33.8 L.min-1 by WM. The VMM turbine is accurate and reliable for the measurement of FEV1 and FVC over the ranges studied; however, care should be taken when interpreting PEFR.

Adult↗
PubMed2004

Integrated gas analyzer for complete monitoring of turbine engine test cells.

Fourier transform infrared (FT-IR) spectroscopy is proving to be reliable and economical for the quantification of many gas-phase species during testing and development of gas turbine engines in ground-based facilities such as sea-level test cells and altitude test cells. FT-IR measurement applications include engine-generated exhaust gases, facility air provided as input to engines, and ambient air in and around test cells. Potentially, the traditionally used assembly of many gas-specific single gas analyzers will be eliminated. However, the quest for a single instrument capable of complete gas-phase monitoring at turbine engine test cells has previously suffered since the FT-IR method cannot measure infrared-inactive oxygen molecules, a key operational gas to both air-breathing propulsion systems and test cell personnel. To further the quest, the FT-IR sensor used for the measurements presented in this article was modified by integration of a miniature, solid-state electrochemical oxygen sensor. Embedded in the FT-IR unit at a location near the long-effective-optical-path-length gas sampling cell, the amperometric oxygen sensor provides simultaneous, complementary information to the wealth of spectroscopic data provided by the FT-IR method.

Journal Article↗
PubMed1993

Bacteriological analysis of high-speed handpiece turbines.

The microbial contamination of handpiece turbines was examined clinically. In 20 handpieces, no bacterial growth was found on any culture from an autoclaved or non-autoclaved handpiece group. But growth occurred in the positive control inoculated with fresh whole human saliva. An adjunctive investigation with saliva substitute showed that oral fluids can contaminate handpiece turbines during simulated clinical treatment.

Colony Count, Microbial↗
PubMed2002

The air turbine and hearing loss: are dentists at risk?

BACKGROUND: Damage to the dentist's hearing because of the popularity of the air turbine has been the subject of many articles, but no conclusive proof has been given that the turbine is a health factor. OVERVIEW: The author provides a historical review of the literature regarding hearing loss among dentists. CONCLUSIONS: In light of the inconclusive results of the literature review, the author recommends that further studies be conducted.

Audiometry↗
PubMed1999

Refining and blending of aviation turbine fuels.

Aviation turbine fuels (jet fuels) are similar to other petroleum products that have a boiling range of approximately 300F to 550F. Kerosene and No.1 grades of fuel oil, diesel fuel, and gas turbine oil share many similar physical and chemical properties with jet fuel. The similarity among these products should allow toxicology data on one material to be extrapolated to the others. Refineries in the USA manufacture jet fuel to meet industry standard specifications. Civilian aircraft primarily use Jet A or Jet A-1 fuel as defined by ASTM D 1655. Military aircraft use JP-5 or JP-8 fuel as defined by MIL-T-5624R or MIL-T-83133D respectively. The freezing point and flash point are the principle differences between the finished fuels. Common refinery processes that produce jet fuel include distillation, caustic treatment, hydrotreating, and hydrocracking. Each of these refining processes may be the final step to produce jet fuel. Sometimes blending of two or more of these refinery process streams are needed to produce jet fuel that meets the desired specifications. Chemical additives allowed for use in jet fuel are also defined in the product specifications. In many cases, the customer rather than the refinery will put additives into the fuel to meet their specific storage or flight condition requirements.

Aviation↗
PubMed2003

A functional and aesthetic solution for saddle nose deformity: the use of the inferior turbinate bone.

The use of a new autologous material, the inferior turbinate bone, for nasal augmentation is presented together with surgical treatment of a 24-year-old male patient with moderately severe saddle nose deformity. In the postoperative period, no complications were observed. Photographs and three-dimensional computed tomography views obtained 13 months after the operation showed that the reconstruction area was highly free of postoperative resorption. The patient's complaints disappeared, and he was satisfied with functional and cosmetic results. Moreover, a histologic evaluation which was made to assess the depth of the glandular component showed that the inferior turbinate bone could be used over the nasal dorsum in a smoother shape, retaining its overlying soft tissue.

Adult↗
PubMedDate not supplied

[Problems of the design of turbine stomatologic tips with light guides].

The systems of turbine stomatologic tips with light guides for local illumination of the tooth area to be treated are analyzed. The basic problems that arise in the elaboration of such systems and the results obtained are specified. The technical characteristics of a halogen mini-lamp to be employed in turbine stomatologic tips are provided.

Dental Instruments↗
PubMedDate not supplied

The performance of air-turbine handpieces in general dental practice.

OBJECTIVE: To investigate variation in performance measures of fibre-optic, high-speed air-turbine handpieces during the course of daily use in general dental practice. MATERIALS AND METHODS: Four groups of five new high-speed fibre-optic handpieces were used in the routine treatment of patients over a period of 30 months by four general dental practitioners in two dental practices: Groups A, B: Super-Torque Lux 3 650B (KaVo, Biberach, Germany); Group C: BORA 898LE (BienAir SA, Bienne, Switzerland) and Group D: Toplight (W&H Dentalwerk, Burmoos, Austria). The dental practice teams had been rehearsed in the procedures to be followed before starting the study. Each dentist used the handpieces in strict rotation, while the groups were rotated monthly between practitioners. Four performance characteristics were measured before use, then at regular intervals: free-running speed (Hz) and bearing resistance (microNm) were measured using a purpose-built testing machine (Darvell-Dyson); illuminance (lux) and sound pressure level (dB(A)) were also measured. Handpieces were cleaned and lubricated in accordance with manufacturers' directions; all were autoclaved wet at 134 degrees C for three minutes. RESULTS: Free-running speed showed an initial increase after use for Groups A, B and C, which may be associated with a decrease in bearing resistance. All handpieces in Group C suffered bearing failure between months 21 and 23, preceded by a substantial increase in noise, while those in Group D suffered failure of the fibreoptic system between months 18 and 24. Other deterioration due to use was identified but Groups A, B and D were still in use at month 30. CONCLUSIONS: Variation in free-running speed, bearing resistance, illuminance and sound pressure level can be used effectively to monitor changes in air-turbine handpieces due to normal use. Although an increase in bearing resistance is associated with decreasing free-running speed, noise appears to be a useful indicator of imminent bearing failure. Assiduous adherence to manufacturers' directions for cleaning and lubrication may have contributed to increased bearing life.

Air↗
PubMed1989

[Slowing of turbine under different pressures (torque)].

A comparative examination of in vivo measured revolutions proves that turbines with torque have a 100% wider usable revolution band than conventional ones. The resulting increased grinding capacity may seen at first sight as a positive effect, but is combined with a more than proportional increasing heat development. Literature, research and own considerations allow the statement, that revolutions used today and the possible pressures make a sufficient cooling of the grinded surface a problem. In order to reduce the recent distinct increase of preparation damages, a reduction of the possible exerted pressure as well as the current level of revolutions must be called for. In the same way as usual in the production industry the optimum rate of grinding capacity to heat development should be determined for each grinding instrument. In this respect not only the turbine is a step into a wrong direction.

Dental Cavity Preparation↗
PubMed1980

[A model study on air contamination at the stomatologic work place by use of the turbine].

Certain dental measures, e. g., the application of a turbine, an ultra-sonic hand-piece or a spray, produce aqueous, polydisperse aerosols which escape from the patient's oral cavity during treatment and contaminate the room air with micro-organisms from the oral microbial flora. An aerobacteriometric model study at a stomatological work place showed that the germ content of the air was significantly higher on days when the turbine was used than on days when it was not used.

Aerosols↗
PubMedDate not supplied

Microbiological evaluation of a newly designed dental air-turbine handpiece for anti-cross contaminations.

The effectiveness of a newly developed anti-cross contamination device for a dental air-turbine handpiece was tested. The handpiece with or without the anti-cross contamination device was contaminated with two bacterial strains, Staphylococcus aureus and Streptococcus mutans, as well as two bacteriophage strains, T2 and MS2. After contamination with these microorganisms, the handpieces were disinfected with glutaraldehyde or replaced with newly autoclaved ones. Residual microorganisms inside the handpiece or an air/water supply hose line were collected and counted after overnight cultivation. The anti-cross contamination device effectively reduced the contamination level of an air-turbine handpiece to that of the negative control. No microbial contamination in the air/water supply hose line was detected with this device.

Air Microbiology↗
PubMedDate not supplied

[A new device for the disinfection of handpieces and turbines].

Dental handpieces are often difficult to disinfect. This is one of the main reasons for the considerable risk of cross-infections in dental offices. The aim of the present study was the evaluation of the disinfectant property of a recent, commercially available, automatic instrument, described as capable to clean, disinfect and lubricate dental handpieces. The following experimental evaluations were made: 1) antimicrobial activity of the disinfectant (glyoxalaldehyde) used. The method described by the European Committee for Standardization was followed. Test microorganisms were Pseudomonas aeruginosa and Staphylococcus aureus. 2) disinfection of dental handpieces (69 contra-angles and 97 turbines of different marks). They were naturally infected using them on patients for 30 minutes at least. 3) disinfection of dental handpieces infected with bacterial suspensions of Staphylococcus aureus, Streptococcus pyogenes (beta-haemolyticus, group A), Candida albicans and Pseudomonas aeruginosa. The results of the first experiment showed a strong bactericidal power of the disinfectant with both the tested strains, after a contact time of only 1 minute. A great proportion of the dental handpieces tested during the second experiment were found disinfected: from 84% through 89% out of the various models of turbine handpieces; from 89% through 100% out of the models of contra-angle handpieces. Even though bacterial contamination level was low (about 10(3) microorganisms per handpiece), a satisfactory disinfectant ability in natural conditions was found. The results of the third experiment were unclear. The tested instrument reduced 10(5)-10(8) times the original bacterial count when the gram positive microorganisms (Staphylococcus aureus, Streptococcus pyogenes) were used. On the other hand, when Pseudomonas aeruginosa and Candida albicans were used, the results were different: the bacterial count was reduced 10(6)-10(7) times in some cases, and only 10(2) times in other cases. This difference was found in the tests made using the same attachment and in those made using various attachments. In conclusion, the tested instrument showed, in most cases, a good disinfectant property, but the presence of unclear results suggests that some technical modifications are required.

Cross Infection↗
PubMed1995

[Hygienic processing of dental transmission instruments (handpieces and instruments, turbines) in dental practice].

The efficacy of a steam disinfection method for the processing of used instruments in dental practice was tested with 274 high-speed turbines and handpieces. The instruments treated with streaming steam were both taken out of the dental practice of treatment and artificially contaminated with five different test-microorganisms (E. coli, P. aeruginosa, S. aureus, E. faecium, C. albicans) and different concentrations of serum (1%, 10%, 20%). In spite of the narrow channels of these instruments a microbial reduction of more than 5 log10 steps could be achieved in all cases. Thus dental high-speed turbines and handpieces can reliably be disinfected with streaming steam.

Colony Count, Microbial↗
PubMed2006

The histopathology of the hypertrophic inferior turbinate.

OBJECTIVE: To analyze the quantitative and qualitative characteristics of the hypertrophic inferior turbinate (IT). DESIGN: A prospective, nonrandomized, controlled, morphometric study. SETTING: University-affiliated hospital. Subjects Seventeen patients with refractory IT hypertrophy and 12 with normal ITs. INTERVENTIONS: Twenty ITs were removed from patients with refractory IT hypertrophy and 14 from patients with normal ITs. MAIN OUTCOME MEASURES: The soft tissue and bony elements and the relative proportions of the soft tissue constituents of the hypertrophic and normal ITs were measured and compared. The Bonferroni correction was used to adjust for multiple comparisons. Qualitative assessment was performed to assess possible pathologic changes in all IT tissues. RESULTS: The hypertrophic ITs were significantly wider. The medial mucosal layer, which thickened from a mean +/- SD of 1.39 +/- 0.28 mm to 2.53 +/- 0.56 mm (P</=.001), made the greatest contribution to the total increase in the width of the IT (64.4%). The enlargement in width of the lateral mucosal layer from 0.91 +/- 0.26 mm to 1.26 +/- 031 mm was of borderline statistical significance. The portion of the medial, lateral, and inferior layers of the lamina propria that houses inflammatory cells enlarged significantly in patients with IT hypertrophy compared with healthy control subjects. The relative proportion of the connective tissue, submucosal glands, and arteries remained unchanged, whereas that of venous sinusoids increased significantly in all aspects of the hypertrophic mucosa. Fibrosis, inflammation, and engorged venous sinusoids were noted in hypertrophic ITs, yet there was no evidence of tissue destruction. CONCLUSION: Understanding the histopathology of the hypertrophic IT is imperative for the development and management of IT reduction surgery.

Adolescent↗