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- MakaleYalnız künye2023Scopus SJRQ1Analysis of the mechanical behavior and prediction of the plastic zone of a large-diameter buried gas pipeline under ground overload
Xu, Qian; Zhong, Liqiong; Shu, Mengjie; Zou, Zhenwei; Yang, Gang; Zheng, Qiang; Chen, Xingli; Akkurt, Nevzat; Zhang, Hui; Qiang, Yujie
Plastic failure of pipelines caused by ground overload is increasing. The one-dimensional model based on mechanical nodal parameters cannot predict the plastic failure characteristics of the three-dimensional structure of the pipeline. In order to predict the evolution of the plastic failure of the pipeline with the yield strength as the evaluation criterion, a multidimensional model is needed to consider the changes in the external loads and the changes in the mechanical properties of the pipeline along the circumferential and axial directions. In this study, a finite element calculation model for a large-diameter gas pipeline underground overload was established to investigate the law of stress change in the plastic zone. The nonlinear surface fitting method was used to establish the angle fitting model of the plastic zone and the depth fitting model of the plastic zone. The variation of the area of the plastic zone was described, and the reliability of the results was verified. In addition, the accuracy of the fitting model and the cost of the finite element calculation were evaluated. The results showed that the pipeline entered plasticity at a ground load of P = 25 MPa, and the plastic zone developed continuously in the axial and circumferential directions as the ground load increased. The angle and depth increased to 36° and 1.8 m, respectively, at P = 50 MPa. The average absolute errors for the plastic zone depth fitting model and the plastic zone angle fitting model were 6.42% and 6.64%, respectively, both of which can provide an accurate description of the plastic zone. The calculation results of the plastic zone angle fitting model could meet requirements of data processing and analysis. The plastic zone depth fitting model could be used to obtain solutions with higher accuracy, but it increases the cost of finite element simulation.
AtıfScopus6OpenAlex6
İncele - MakaleYalnız künye2022Scopus SJRQ1Dynamic response model and equivalent solution method of large-diameter buried energy transportation pipeline under moving load
Xu, Qian; Yang, Gang; Li, Zhuorui; Zou, Zhenwei; Zheng, Qiang; Zhong, Liqiong; Chen, Xingli; Akkurt, Nevzat; Du, Yanping; Xiong, Yaxuan
Long-distance energy pipeline pass under roads, subjecting them to repeated stress and posing pipeline safety problems. To simulate the effects of vehicles driving over energy transmission pipeline, this paper examines large-caliber buried pipelines in the suburbs. In this study, a mechanical action model of vehicle-soil-pipeline (VSP) interactions to transform the process of a vehicle driving into the dynamic process of a load changing with time in the specified area was created. The VSP model was used to analyze the influence of moving load and position on the structural characteristics of the pipeline section. An equivalent solution method with high precision and high calculation efficiency was proposed. The results showed that as the loading position approaches the pipeline or the load increases, the stress value at the top of the pipeline gradually exceeded the stress value at the bottom of the pipeline and became the area with the maximum stress value. The minimum stress location also changed from the lower half near the pipeline bottom (Point D-135°) to the upper half near the pipeline top (Point B-45°or Point H-315°). Using the polynomial fitting method, the stress values of the maximum points were equivalently converted. Under the premise of considering pipeline safety, the most suitable functional relationship for the moving load equivalent model was obtained.
AtıfScopus16OpenAlex13İncele - MakaleYalnız künye2022Scopus SJRQ1Numerical evaluation of the coupled/uncoupled effectiveness of a fluid-solid-thermal multi-field model for a long-distance energy transmission pipeline
Wang, Kang; Xie, Kai; Zhang, Hui; Qiang, Yujie; Du, Yanping; Xiong, Yaxuan; Zou, Zhenwei; Zhang, Mingbao; Zhong, Liqiong; Akkurt, Nevzat
As the main component of energy transmission, long-distance energy transmission pipeline (LETP), whose safety problem is becoming more and more prominent with the development of the oil and gas transportation industry, is susceptible to the traffic loading, temperature loading, pressure loading and other loadings. In this paper, the mechanical characteristics of LETP under the interaction of temperature loading and pressure loading are investigated. Based on the theory of multi-field coupling, the mathematical model of fluid-solid-thermal coupling of fluid-filled pipelines under the combined effect of temperature and pressure loadings is established and verified. Meanwhile, an equivalent model is proposed to accurately calculate the stress of any pipeline segment in LETP. The results show that the coupling of temperature loading and the pressure loading is significantly affected by the end-side constraints of the pipelines. For strong end-side constraint, the coupling effect of temperature and pressure loadings has a significant effect on the calculated equivalent stress. The difference between the stress solution under coupling effect and decoupling effect is above 30 MPa. However, for weak end-side constraints, the error is within 10 MPa. The equivalent stress can be approximated by the decoupling solution instead of the coupling solution.
AtıfScopus15OpenAlex15İncele - MakaleYalnız künye2021Scopus SJRQ2Effects of Optimized Operating Parameters on Combustion Characteristics and NOx Emissions of a Burner based on Orthogonal Analysis
Xu, Qian; Akkurt, Nevzat; Yang, Gang; Zhu, Lidong; Shi, Kejian; Wang, Kang; Zou, Zhenwei; Liu, Zhihui; Wang, Jiulong; Du, Zhiwei
To optimize the structure of the burner, improve the combustion performance, and reduce the emission of NOx, a self-circulating low NOx combustion technology was used to design a new type of flue gas self-circulating low NOx burner. Based on previous research on the numerical model of combustion and the composition of mixed gas on combustion and NOx emissions, the effect of various factors on the ejection coefficient of the flue gas self-circulating structure was analyzed using the orthogonal test method, and the burner operating parameters, such as preheating temperature and excess air coefficient, were deeply studied through the three-dimensional finite element numerical model in this paper. The results show that the diameter ratio of the nozzle and the length of the cylindrical section of the flue gas self-circulating structure have great influence on its ejection and mixing ability. The optimal ejection coefficient was 0.4829. Overall, the amount of NOx emissions greatly increased from 6.23×10−6 (volume fraction) at the preheating temperature 973 K to 3.5×10−3 at preheating temperature 1573 K. When the excess air coefficient decreased from 1.2 to 1, the maximum combustion temperature decreased from 2036.3 K to 1954.22 K, and the NOx emissions decreased from 352.29×10−6 to 159.73×10−6.
AtıfScopus7OpenAlex8İncele - MakaleYalnız künye2021Scopus SJRQ1A new type of two-supply, one-return, triple pipe-structured heat loss model based on a low temperature district heating system
Xu, Qian; Wang, Kang; Zou, Zhenwei; Zhong, Liqiong; Akkurt, Nevzat; Feng, Junxiao; Xiong, Yaxuan; Han, Jingxiao; Wang, Jiulong; Du, Yanping
Based on the design concept of a fourth-generation smart pipe network system, this paper innovatively proposes a new TOTS (Two-supply/One-return, triple pipe structure) arrangement method for district heating systems. Moreover, to accurately predict the heat loss due to the pipeline operation of the multi-pipe system, based on the multipole calculation method, a new heat loss theoretical analytical model for the TOTS was created; additionally, a corresponding three-dimensional numerical simulation model was established, which was analyzed and numerically solved. The results showed that in comparison with thermal loss data measured by Danfoss et al., the above analytical and numerical models have a high accuracy, and the deviation is within 2%. Additionally, through calculations, it was found that the distance between the heating pipes is an important factor that affects the total heat loss from the new multi-control heating system and the actual heat exchange between pipes.
AtıfScopus74OpenAlex75İncele - MakaleYalnız künye2020Scopus SJRQ2Synthesis and Characterization of Disodium Hydrogen Phosphate Dodecahydrate-Lauric-Palmitic Acid Used for Indoor Energy Storage Floor Units
Xu, Qian; Akkurt, Nevzat; Zou, Zhenwei; Liu, Yang; Feng, Junxiao; Yu, Chuqiao; Ding, Chong; Xiong, Yaxuan; Zhou, Jingzhi; Zang, Yong
Organic and inorganic phase change materials (PCMs) are considered potential materials for thermal energy storage (TES) with different phase change characteristics. In this study, a novel organic-inorganic composite phase change material (PCM) called disodium hydrogen phosphate dodecahydrate-lauric-palmitic acid (D-LA-PACM) was prepared. Expanded graphite (EG) was selected as the support material, and the novel organic-inorganic form-stable PCM called D-LA-PAPCM/EG was prepared using the vacuum adsorption method. Differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, leakage testing, melting and solidification cycle testing, thermal conductivity testing, scanning electron microscopy observation of the micromorphology, and other characterization methods were used to study the micro structure and morphology, thermal physical parameters, thermal conductivity, stability of the PCMs, and the comprehensive material properties of D-LA-PAPCM under the composite action of EG. Results indicated that the melting and freezing temperatures and latent heats of D-LA-PAPCM/EG were measured to be 31.6°C and 34.3°C and 142.9 and 142.8 J/g, respectively. Although some of the lauric-palmitic acid (LA-PA) and disodium hydrogen phosphate dodecahydrate (DHPD) separated in the multiple porous structures of EG after 1000 cycles, they could still absorb and release latent heats independently, with D-LA-PAPCM/EG still exhibiting good thermal stability. The thermal conductivity of D-LA-PAPCM/EG was 1.361 W/(mK). Therefore, the material and thermal properties of the prepared D-LA-PAPCM/EG indicate that it could be well used as a feasible material for energy-saving phase change floor units in indoor TES systems.
AtıfScopus18OpenAlex18İncele