Papers by Keyword: Steady-State

Abstract: The creep response and stress relaxation of X20 CrMoV12-1 steam piping under diverse operating conditions were simulated using finite element analysis (FEA) code, Abaqus alongside fe-safe/Turbolife software. In the study, steady-state creep and creep analysis characterized by 24 hours daily cycle consisting of a total of 6 hours peak, 4 hours transient and 14 hours off-peak period was considered. Modified hyperbolic sine creep model used in the analysis was implemented in Abaqus via a special creep user-subroutine to compute the stress relaxation and creep behaviour, while the useful service life and creep damage was estimated using fe-safe/Turbolife. The optimum creep strain, stress, damage, and worst life were found at the intrados of the piping, with the steady-state analysis having a higher useful creep life and slower creep damage accumulation. Furthermore, slower stress relaxation with faster damage accumulation was observed in the analysis involving cycles. Finally, a good agreement was obtained between the analytical calculated and simulated rates of the piping.

Abstract: Performance of activated sludge wastewater treatment plants are mainly dependent on bacterial growth, which is limited by many factors. These factors include availability of suitable substrate, limiting nutrients, environmental conditions, and energy. In activated sludge model no. 3 (ASM3), constituents in wastewater are divided into two main categories: carbonaceous compounds and nitrogenous compounds, which are further subdivided depending on their solubility and biodegradability. These compounds are not mutually independent; hence, the fate of one compound in the biological processes is affected by one or more of the other compounds. In this study, a steady-state analysis was conducted to investigate the effect of initial readily biodegradable substrate, oxygen, ammonia nitrogen, nitrite plus nitrate, and heterotrophic organisms’ concentrations on the effluent concentrations of readily biodegradable COD and nitrogen compounds. The studied ranges of the selected wastewater state variables were identified based on literature surveys including previous studies concerning domestic, industrial, and synthetic wastewaters. The results proved that the effluent readily biodegradable substrate and ammonia nitrogen concentrations are reduced as the initial dissolved oxygen and nitrite plus nitrate concentrations are increased. Moreover, better nitrification-denitrification process is achieved at lower initial readily biodegradable concentration leading to lower nitrite plus nitrate concentrations.

Abstract: A steady state magnetohydrodynamic laminar solver with low magnetic Reynolds number has been developed in OpenFOAM platform. SIMPLE method has been used to solve the velocity vector and pressure. The induced electric potential and induced electric current has been solved according to a consistent and conservative scheme on a collocated structure grid. The solver has been validated by simulating Shercliff's case with medium Hartmann number. The results show that the numerical solution results match the analytical solutions well.

Abstract: In many practical applications, the impulse responses of the unknown system are sparse. However, the standard Least Mean Square (LMS) algorithm does not make full use of the sparsity, and the general sparse LMS algorithms increase steady-state error because of giving much large attraction to the small factor. In order to improve the performance of sparse system identification, we propose a new algorithm which introduces a variable step size method into the Reweighted Zero-Attracting LMS (RZALMS) algorithm. The improved algorithm, whose step size adjustment is controlled by the instantaneous error, is called Variable step size RZALMS (V-RZALMS). The variable step size leads to yielding smaller steady-state error on the premise of higher convergent speed. Moreover, the sparser the system is, the better the V-RZALMS performs. Three different experiments are implemented to validate the effectiveness of our new algorithm.

Abstract: In this paper, the axisymmetric general steady-state solution for porous media is presented. And the completeness of the P-Ns representation for the axisymmetric displacement field equation is proved directly from the equations governing the displacement field, which can be applied to homogeneous and isotropic poroelastic materials. At last, the Boussinesq general solution and Timpe general solution are obtained from P-N General Solution.

Abstract: PHE (Process Heat Exchanger) is a key component for transferring the high-temperature heat generated from a VHTR (Very High Temperature Reactor) to a chemical reaction for massive production of hydrogen. Recently, Korea Atomic Energy Research Institute (KAERI) has manufactured a medium-scale PHE prototype made of Hastelloy-X of high-temperature alloy and a performance test on the PHE prototype is scheduled in a small-scale nitrogen gas loop established at KAERI. In this study, in order to evaluate the high-temperature structural integrity of the PHE prototype under the steady-state and trip conditions of the gas loop before the performance test on the PHE prototype, elastic and elastic-plastic structural analyses on the PHE prototype were carried out and the analyses results were compared each other.

Abstract: Today CFD is an important tool for engineers in the automotive industry. To simulate and optimize the fluid flow and heat transfer in the engine, the research is carried out. The geometric models of a gasoline engine and the cooling water jacket are simplified by Pro/E software firstly. Then solid - liquid coupled heat transfer analysis is done by using CFD software FLUENT. Temperature field distributions in the engine body and the cooling water jacket are obtained. An engine temperature test bench is set up, on which temperature values of key points are measured. The analysis on the errors between the experimental data and the calculation results shows that the temperature distributions in the engine are reasonable and the cooling performance of the water jacket meets the design requirements. The deviations between the experimental data and calculated values on the measuring points are not big, so the calculation method has high accuracy. The data obtained in this experiment can be used as the basis in the following study.

Abstract: An all terrain vehicle is a kind of special vehicle that travels on all-road. It should have better handling characteristics. In order to evaluate handling performance of an ATV, steady-state circular motion performance experiments about the ATV are done and steady state response characteristic is analyzed. The results show that the ATV studied has under-steering characteristics which is a good turning state and the results correspond with test report about Santana Xi5 on the road test at Journal of Motor Fan in Japan.

Abstract: During the design process of Internal Combustion (IC) engine, what is often taken into consideration is the temperature of the important heated parts. The temperature distributions are the primary causes of thermal fatigue in the engine. A combined experimental and analytical approach was followed in this work to study temperature distributions of gasoline engine under steady-state and transient operation condition. Experimental studies were conducted to measure temperatures under a series of steady-state and transient operating conditions. A comparison of the steady-state and transient measurements has been made and the character of transient temperature distributions is concluded. Subsequently, a calculation analysis was conducted to predict the detailed temperature distributions. Solid-Fluid whole conjugated heat transfer method is applied in the numerical calculation, which can take the mutual influence both the fluid flow and the heat transfer into account. The predicted temperatures met well with the measurements. Furthermore, the predicted location of coolant boiling phenomena in the water jacket can be made certain. This can give some suggests for the further observation experiment of boiling heat transfer.

Abstract: A novel model of steady-state sliding wear with electrical current was created, which gives an accurate relational expression of three factors (electrical current, sliding velocity and contact pressure) and wear rate of the pin material. The experiments were carried out on the couple of QCr0.5 against copper-based powder metallurgical materials. The results show that the model is accurate and it is able to clearly show the influence of electrical current, sliding velocity and contact pressure on wear rate of pin.