Combustion of reformed gas and liquid fuel in CRGT combustor

U ovom su radu provedene numeričke simulacije četiriju procesa izgaranja u komori izgaranja s dvodijelnom sapnicom za gorivo kemijski rekuperirane plinske turbine (CRGT). Goriva u ta četiri procesa izgaranja bila su tekuće gorivo, tekuće gorivo + para, tekuće gorivo + poboljšani (reformirani) plin i reformirani plin. Matematički modeli primijenjeni za izgaranje različitih goriva sastoje se od modela ostvarive k−ε turbulencije i modela funkcije gustoće vjerovatnoće (PDF). Dobivene su raspodjela temperature, koncentracije vrsta i emisije NO. Rezultati pokazuju da goriva mogu učinkovito sagorijevati u dvodijelnoj komori izgaranja za CRGT. U usporedbi s komorom izgaranja tekućeg goriva, temperatura plamena, srednja temperature stijenke komore izgaranja i emisija NO smanjeni su za 7,8 %, 4,8 % i 75,3 % kad se u komoru uštrcala para. Međutim ti su se iznosi još smanjili kad se tekuće gorivo zamijenilo poboljšanim (reformiranim) plinom i iznosili su 10,3 %, 5,6 % i 97,2 %. Malo pogoršanje ukupne raspodjele temperature ispuha komore izgaranja dobilo se kod komore izgaranja tekućeg goriva + para, dok se bolja raspodjela temperature na ispuhu postigla kod komore izgaranja reformiranog plina u usporedbi s izgaranjem tekućeg goriva.Numerical simulations of four combustion processes in a dual-fuel combustor of chemically recuperated gas turbine (CRGT) were carried out in this work. The fuels in the four combustion processes were liquid fuel, liquid fuel + steam, liquid fuel + reformed gas and reformed gas, respectively. The mathematical models adopted for different fuels combustion consist of realizable k−ε turbulence model and probability density function (PDF) model. The temperature distribution, species concentrations and NO emission were obtained. The results show that the fuels can burn effectively in the dual-fuel combustor for CRGT. Compared with the liquid fuel combustor, the flame temperature, average temperature of combustor wall and NO emission are reduced by 7,8 %, 4,8 % and 75,3 % respectively when the steam is injected into the combustor. However, they are reduced more when the liquid fuel is replaced by reformed gas, which are 10,3 %, 5,6 % and 97,2 % respectively. A little deterioration of the overall temperature distribution of combustor outlet is obtained for liquid fuel + steam combustor, while a better temperature distribution of combustor outlet is obtained for reformed gas combustor, in comparison with liquid fuel combustor

Synchronous charge extraction and voltage inversion (SCEVI): a new efficient vibration-based energy harvesting scheme

This paper presents a new interface technique called synchronous charge extraction and voltage inversion (SCEVI), which consists of a synchronous inductor and a buck-boost converter for vibration-based energy harvesting using piezoelectric elements. The theoretical calculation of the harvested power obtained by using such a technique are proposed and compared with the so-called Standard, SECE (Synchronous Electric Charge Extraction), Parallel-SSHI (Parallel Synchronized Switch Harvesting on Inductor) and Series-SSHI (Series Synchronized Switch Harvesting on Inductor) methods commonly used in piezoelectric vibration-powered generator considering both constant displacement amplitude and force amplitude. From the harvested power point of view, SCEVI and Parallel – SSHI techniques are the better ones and each has its own merits. But the harvested power of SCEVI is independent of the load connected to the generator and Parallel – SSHI depend on the load resistance. The harvested power of SECE is also independent of the load, but the further experimental results show that the proposed SCEVI interface technique dramatically increases the harvested power by almost up to 150 % compared with the SECE method under the same amplitude of displacement excitation

Research on the Integration and Development Path of College Students’ Labor Education and College Student Associations

Student organizations in colleges and universities are important carriers for implementing the fundamental task of cultivating morality and cultivating people and promoting quality education, and college and university organizations have a good foundation for the masses of students and play an important role in educating people in ideological and political education. Therefore, it is necessary to combine the educational platform of college student clubs to explore and analyze the reality of labor education integrated into college associations, clarify the community groups in college clubs that can effectively integrate labor education, and drive the implementation of labor education for college students from multiple perspectives

Free vibration studies of functionally graded magneto-electro-elastic plates/shells by using solid-shel ements

In this article, free vibration studies on functionally graded magneto-electro-elastic plates and cylindrical shells have been carried out by means of finite element method. The functionally graded material is assumed to be exponential in the thickness direction. The present finite element is formulated on the basis of assumed natural strain, enhanced assumed strain method and using displacement components, electric potential and magnetic potentials as nodal degrees of freedom. This element can be used as solid element and can also be applied to model thin curved shell structures. Numerical studies include the influence of the different exponential factor, magnetic and piezoelectric effect on the natural frequencies. Obtained numerical results are in good agreement with the semi-analytical finite element solutions available in the literature

Direct detonation initiation in hydrogen/air mixture: effects of compositional gradient and hotspot condition

Two-dimensional simulations are conducted to investigate the direct initiation of cylindrical detonation in hydrogen/air mixtures with detailed chemistry. The effects of hotspot condition and mixture composition gradient on detonation initiation are studied. Different hotspot pressure and composition are first considered in the uniform mixture. It is found that detonation initiation fails for low hotspot pressures and supercritical regime dominates with high hotspot pressures. Detonation is directly initiated from the reactive hotspot, whilst it is ignited somewhere beyond the nonreactive hotspots. Two cell diverging patterns (i.e., abrupt and gradual) are identified and the detailed mechanisms are analyzed. Moreover, cell coalescence occurs if many irregular cells are generated initially, which promotes the local cell growing. We also consider nonuniform detonable mixtures. The results show that the initiated detonation experiences self-sustaining propagation, highly unstable propagation, and extinction in mixtures with a linearly decreasing equivalence ratio along the radial direction respectively, i.e., 1 to 0.9, 1 to 0.5 and 1 to 0. Moreover, the hydrodynamic structure analysis shows that, for the self-sustaining detonations, the hydrodynamic thickness increases at the overdriven stage, decreases as the cells are generated, and eventually become almost constant at the cell diverging stage, within which the sonic plane shows a sawtooth pattern. However, in the detonation extinction cases, the hydrodynamic thickness continuously increases, and no sawtooth sonic plane can be observed

Detecting multiple cracks in beams using hierarchical genetic algorithms

This study deals with a method to identify multiple cracks in a beam. The novelty of this study is the use of a hierarchical genetic algorithm to detect the number, location, and the extent of multiple cracks. To demonstrate the feasibility of the present method, this algorithm is applied to the identification of double or triple cracks in a beam as well as four cracks. The detected crack locations and sizes are in excellent agreement with the actual ones. The numerical simulation reveal the HGA substantially reduces the total number of FE computation required and they are many orders smaller compared to conventional GA. The results also demonstrate the advantages of HGA from the viewpoints of its ability to avoid premature convergence