Mathematical model of turbojet engine combustion chamber primary zone

Razvijen je i eksperimentalno potvrđen matematički model primarne zone komore sagorevanja turbomlaznog motora. Komora sagorevanja je prstenasta sa prstenastim jediničnim isparivačem postavljenim centralno u primarnu zonu. Ovakva konfiguracija je vrlo interesantna za aplikacije kod kojih su dominantni zahtevi za malim dimenzijama. Model je ispitivan u sklopu cele komore sagorevanja i ocenjivan je preko potpunosti sagorevanja cele komore.Mathematical model of turbojet engine primary zone was developed and tested Combustion chamber was of annular type with single annular vaporizer positioned at the center. This configuration is very attractive for the applications where small dimensions are of primary interest. The model was tested as a part of combustion chamber and it was estimated through the overall combustion chamber efficiency

Mathematical model of turbojet engine combustion chamber primary zone

Razvijen je i eksperimentalno potvrđen matematički model primarne zone komore sagorevanja turbomlaznog motora. Komora sagorevanja je prstenasta sa prstenastim jediničnim isparivačem postavljenim centralno u primarnu zonu. Ovakva konfiguracija je vrlo interesantna za aplikacije kod kojih su dominantni zahtevi za malim dimenzijama. Model je ispitivan u sklopu cele komore sagorevanja i ocenjivan je preko potpunosti sagorevanja cele komore.Mathematical model of turbojet engine primary zone was developed and tested Combustion chamber was of annular type with single annular vaporizer positioned at the center. This configuration is very attractive for the applications where small dimensions are of primary interest. The model was tested as a part of combustion chamber and it was estimated through the overall combustion chamber efficiency

Research of expendable turbojet tubular combustion chamber

This paper presents research related to the tubular combustion chamber of an expendable turbojet. Although annular combustors are dominant at present, tubular combustors are still attractive because they are simpler to produce and require lower amounts of air flow for testing. The objective of this research was to assess the combustor's primary zone configuration, and four configurations were tested to obtain experimental answers for use in future work. The configuration of the combustion chamber is a simple and classic design in line with its expendable purpose. The test methodology was to perform initial testing of the primary and secondary zones under atmospheric conditions using the four configurations, and then to subsequently complete the combustor using the best configuration. The complete combustor was then tested under both atmospheric conditions and working conditions. The results showed that the stability margin was wide enough to cover the combustor's entire working area. The measured efficiency and pressure drop were in very good agreement with the corresponding designed values. The design and testing methodology proposed here could be used for similar scientific and engineering research applications

Analysis and design of the gas generator multifunctional bulkhead considering the thermal and structural loads

The operation of gas generators brings relatively high thermo-mechanical loads on the gas generator structure. The objective of this article is to determine the operating conditions, in terms of mechanical loads at extremely high temperatures in very limited and narrow space, of a multifunctional bulkhead for application on specific kinds of gas generators with back-to-back rotor concept. The paper contains numerical analysis and experimental investigation for determining the loads and behavior of the structure. Numerical analysis indicates that there is significant influence of the Tesla turbine effect on flow parameters. Also, uneven pressure distribution and significant thermal loads are identified. With experimental investigation and subsequent exploitation tests, it was concluded that the presented methodology identifies the operating conditions, truthfully simulates the bulkhead stress state and deformations and that the presented design solution satisfied all demands. Regarding results obtained by these numerical simulations, the innovative design solution for the multifunctional bulkhead was proposed

SEM analiza kvaliteta adhezivne veze glasjonomercementnih restauracija

Introduction. Lack of proper adhesion is one of the most common problems in modern restorative dentistry and the main cause of the occurrence of microcracks at the interface between materials and hard dental tissue. The aim of this study was to assess the quality of bond between two types of glass-ionomer cement (GIC) class V restorations and hard dental tissues by SEM. Materials and Methods. This clinical study included 20 intact teeth (premolars and molars) recently extracted for orthodontic reasons in patients of both genders and different ages. Class V cavity with rounded walls was prepared on vestibular and oral surfaces of all teeth (3x2x2 mm). Conventional GIC Fuji II was applied on vestibular surface of teeth whereas on oral surface resin-reinforced glass ionomer Fuji II LC was placed. The bond between fillings and hard dental tissue was assessed by SEM. Results. Both materials showed microcracks, however, microleakage was lower with Fuji II LC than with Fuji II. Microcracks were observed in 65% of cases (13 restorations) restored with GIC Fuji II and 35% (7 fillings) restored with GIC Fuji II LC. The size of microcracks for Fuji II LC was 9 μm while this value for Fuji II was 17 μm. The difference was statistically significant. Conclusion. Better bond between material and hard dental tissue was achieved with the material of new generation, resin modified GIC.Uvod. Nedostatak odgovarajuće adhezivnosti je jedan od najčešćih problema u savremenoj restaurativnoj stomatologiji i glavni uzrok nastanka mikropukotine na spoju materijala i tvrdih zubnih tkiva. Cilj ovog rada je bio da se SEM (skening-elektronska mikroskopija) analizom proveri kvalitet veze dve vrste glasjonomercementnih (GJC) restauracija za tvrda zubna tkiva kod kaviteta V klase. Materijal i metode rada. Kliničko istraživanje je obuhvatilo 20 sveže ekstrahovanih intaktnih zuba (premolari i molari), odstranjenih iz ortodontskih razloga kod pacijenata oba pola i različite starosti. Na svim zubima su sa vestibularne i oralne strane urađene jednopovršinske preparacije V klase adhezivnog tipa sa zaobljenim zidovima kaviteta (dimenzija 3×2×2 mm). Sa vestibularne strane primenjen je klasični GJC Fuji II, a sa oralne smolom ojačani GJC Fuji II LC. Kvalitet veze između ispuna i zubnih tkiva je procenjivan SEM analizom. Rezultati. Dobijeni nalazi su pokazali da je kod oba materijala zabeležena mikropukotina i da je stepen mikrocurenja kod Fuji II LC bio manji nego kod Fuji II. Kod zuba restaurisanih sa GJC Fuji II mikropukotina je uočena u 65% slučajeva (13 ispuna), a kod zuba restaurisanih sa GJC Fuji II LC u 35% slučajeva (sedam ispuna). SEM analizom je utvrđena srednja vrednost mikropukotine za Fuji II LC od 9 µm, dok je ova vrednost za Fuji II bila 17 µm. Razlika je bila statistički značajna. Zaključak. Na osnovu rezultata istraživanja može se zaključiti da je bolji kvalitet veze ostvaren primenom materijala novije generacije, odnosno primenom GJC modifikovanih smolom

Influence of different factors on the RAID 0 paired magnetic disk arrays

The rapid technological progress has led to a growing need for more data storage space. The appearance of big data requires larger storage space, faster access and exchange of data as well as data security. RAID (Redundant Array of Independent Disks) technology is one of the most cost-effective ways to satisfy needs for larger storage space, data access and protection. However, the connection of multiple secondary memory devices in RAID 0 aims to improve the secondary memory system in a way to provide greater storage capacity, increase both read data speed and write data speed but it is not fault-tolerant or error-free. This paper provides an analysis of the system for storing the data on the paired arrays of magnetic disks in a RAID 0 formation, with different number of queue entries for overlapped I/O, where queue depth parameter has the value of 1 and 4. The paper presents a range of test results and analysis for RAID 0 series for defined workload characteristics. The tests were carried on in Microsoft Windows Server 2008 R2 Standard operating system, using 2, 3, 4 and 6 paired magnetic disks and controlled by Dell PERC 6/i hardware RAID controller. For the needs of obtaining the measurement results, ATTO Disk Benchmark has been used. The obtained results have been analyzed and compared to the expected behavior

Modification of existing turboshaft engine in order to operate on synthetic gas

Sintetički gas je danas ko-proizvod procesa kao što su gasifikacija otpada i prerade biomase, uglja i drugih potencijalnih goriva. Iako sastav sintetičkog gasa zavisi od prethodnih procesa, generalno se sastoji od mešavine vodonika, ugljen-monoksida i metana u različitim odnosima. Ideja da se sintetički gas dobijen preradom otpada koristi kao gorivo za turbo-generator je veoma privlačna, ali i vrlo zahtevna. U ovom radu je prezentovana modifikacija postojećeg turbo-vratilnog motora da bi mogao da koristi sintetički gas kao gorivo. Pored problema kao što su mala toplotna moć, drugačiji stehiometrijski odnos u poređenju sa kerozinom i visok procenat vodonika, inženjerski zadatak je bio da se problem reši sa minimalnim brojem izmena. Problem je rešen modifikaciojom postojećih vazdušnih raspršivača i verifikovan je eksperimentalno.Synthetic gas is nowadays the co-product of procceses such as waste gasification and processing biomass, coal and other potentional fuels. Although its composition depends on previous process, synthetic gas is generally mixture of hydrogen, carbon-monoxide and methane in different ratios. The idea to use gases from waste as a fuel for gas-turbine generator producing electric energy is very attractive but also challenging. In this paper is presented modification of an existing turbo-shaft engine in order to be capable to operate with synthetic gas. Together with problems such as low heating value of the gas, different stochiometric ratio of gas and air compared to kerosene/air combination and high hydrogen contents, the engineering task was to do it with minimum number of changes. Problem is solved by adjusting existing airblast atomizers and experimentally verified

Modification of existing turboshaft engine in order to operate on synthetic gas

Sintetički gas je danas ko-proizvod procesa kao što su gasifikacija otpada i prerade biomase, uglja i drugih potencijalnih goriva. Iako sastav sintetičkog gasa zavisi od prethodnih procesa, generalno se sastoji od mešavine vodonika, ugljen-monoksida i metana u različitim odnosima. Ideja da se sintetički gas dobijen preradom otpada koristi kao gorivo za turbo-generator je veoma privlačna, ali i vrlo zahtevna. U ovom radu je prezentovana modifikacija postojećeg turbo-vratilnog motora da bi mogao da koristi sintetički gas kao gorivo. Pored problema kao što su mala toplotna moć, drugačiji stehiometrijski odnos u poređenju sa kerozinom i visok procenat vodonika, inženjerski zadatak je bio da se problem reši sa minimalnim brojem izmena. Problem je rešen modifikaciojom postojećih vazdušnih raspršivača i verifikovan je eksperimentalno.Synthetic gas is nowadays the co-product of procceses such as waste gasification and processing biomass, coal and other potentional fuels. Although its composition depends on previous process, synthetic gas is generally mixture of hydrogen, carbon-monoxide and methane in different ratios. The idea to use gases from waste as a fuel for gas-turbine generator producing electric energy is very attractive but also challenging. In this paper is presented modification of an existing turbo-shaft engine in order to be capable to operate with synthetic gas. Together with problems such as low heating value of the gas, different stochiometric ratio of gas and air compared to kerosene/air combination and high hydrogen contents, the engineering task was to do it with minimum number of changes. Problem is solved by adjusting existing airblast atomizers and experimentally verified

Experimental Investigation of the High-Speed Roller Bearing Assembly Lubricated by Oil Mist

High speed bearing assemblies have been always challenging in terms of the heat removal and bearing lubrication. Evolution of these lubrication systems led to the oil-mist concept, which consists of the air under high pressure, together with oil droplets. Too high pressure combined with too much of oil would cause the additional resistance to the rolling elements’ movement, while the low pressure with the small amount of oil wouldn’t be effective in terms of the heat removal and lubrication. In this paper, it is analysed the influence of the air pressure and the amount of oil onto the bearings’ temperature

Experimental Investigation of the High-Speed Roller Bearing Assembly Lubricated by Oil Mist

High speed bearing assemblies have been always challenging in terms of the heat removal and bearing lubrication. Evolution of these lubrication systems led to the oil-mist concept, which consists of the air under high pressure, together with oil droplets. Too high pressure combined with too much of oil would cause the additional resistance to the rolling elements’ movement, while the low pressure with the small amount of oil wouldn’t be effective in terms of the heat removal and lubrication. In this paper, it is analysed the influence of the air pressure and the amount of oil onto the bearings’ temperature