CFD Study on the Isolator Performance of a Dual-Mode Scramjet

Ruoyu Deng,Yingzi Jin,Heuy Dong Kim 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.11

As one of the most promising propulsive systems in the future, the dual-mode scramjet has drawn the attention of many researchers. Detailed flow features concerned with the isolator play the important role in the dual-mode scramjet. The two-dimensional numerical model has been established to replicate the generic features of the dual-mode scramjet. Numerical results have been compared with the experimental results for validation. Overall pressure distribution shows quite good agreement with the experimental result. The constant-area variable-length isolator followed by a diffuser section has been researched in this study. The cases of isolator lengths from 8.7 to 20.7 show higher maximum back pressure than other cases. The option of optimal isolator length not only depends on maximum back pressure but also on total pressure loss in the isolator. In conclusion, the optimal isolator length (L/Hth) is 12.7 in this study.

Numerical Visualization of the Pseudo-Shock Waves using LES

Ruoyu Deng,Yingzi Jin,Heuy Dong Kim(김희동) 한국가시화정보학회 2015 한국가시화정보학회지 Vol.13 No.3

The interaction between a normal shock wave and a boundary layer along a wall surface in internal compressible flows causes a very complicated flow. This interaction region containing shock train and mixing region is called as pseudo-shock waves. Pseudo-shock waves in the divergent part of a rectangular nozzle have been investigated by using large-eddy simulation (LES). LES studies have been done for the complex flow phenomena of three-dimensional pseudo-shock waves. The LES results have been validated against experimental wall-pressure measurements. The LES results are in good agreement with experimental results. Pseudo-shock length and corner separation have been studied in three-dimensional LES model. Comparison of centerline pressure measurement and 3D visualization measurement has been discussed for the corner separation position. It has been concluded that the pseudo-shock length should be measured by using 3D visualization measurement.

Optimization study on the isolator length of dual-mode scramjet

Ruoyu Deng,Yingzi Jin,김희동 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

The dual-mode scramjet is a prime candidate for air-breathing propulsion engines given its broad speed range and high efficiency. The detailed structure of the pseudo-shock wave in the isolator is worth investigating. Therefore, the present study investigates the effect of isolator length on the pseudo-shock wave. We replicate the experimental work of the reference paper with a two-dimensional numerical model. Pressure distribution on the body surface is applied in the numerical validation. The numerical result is in good agreement with that of the existing experimental work. We simulate the thermal choking condition with a throttling device. As the throat area of throttling device decreases, the back pressure continues increasing and the pseudo-shock wave moves upstream. Avoiding unstart phenomenon is a key objective in the operation of dual-mode scramjet. Therefore, we investigate the critical condition shortly before unstart phenomenon occurs. The pseudo-shock wave structure is described by pressure distribution. Our main objective is to explore the effect of isolator length on the dual-mode scramjet. The optimal isolator length depends on the maximum back pressure and total pressure loss in the critical condition shortly before the unstart phenomenon occurs. The maximum back pressure in the critical condition is higher when the isolator length ranges from 8.7 to 20.7. The total pressure loss in the critical condition decreases at the beginning and then increases when the isolator length ranges from 8.7 to 20.7.

Numerical Study on the Characteristics of Dual-Mode Scramjet Isolator

Ruoyu Deng,Heuy Dong Kim(김희동),Yingzi Jin 한국추진공학회 2015 한국추진공학회지 Vol.19 No.5

As one of the most promising propulsive systems in the future, the dual-mode scramjet engine has drawn the attention of many researches. Detailed flow features concerned with the isolator play an important role in the dual-mode scramjet system. The 2D numerical method has been used for the dual-mode scramjet with wind tunnel. To validate the ability of the numerical model, numerical results have been compared with the experimental results. Overall pressure distributions show quite good match with the experimental results. Back pressure has been studied for maximum pressure rising. According to the results, pressure distribution of supersonic inlet section is not influenced by back pressure. The shock train is pushed towards upstream as the back pressure increases. The maximum value of back pressure without inlet unstart goes up rapidly and then keeps constant when the isolator length increases. The optimal length of isolator section (L/H<SUB>th</SUB>) is 8.7 in this model.

컨덕턴스의 개념을 사용한 공압관 시스템의 유량 예측

김진현(Jin-Hyeon Kim),Ruoyu Deng,김희동(Heuy-Dong Kim) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.5

컨덕턴스는 유동저항의 반대되는 개념으로써, 광범위하게 유동지표로써 현재 사용되고 있다. 하지만, 유동 컨덕턴스 연구들은 지금까지 매우 드물며, 압축 공기의 표준화 장치에 대한 체계적인 연구가 필요하다. 본 연구에서는 2차 방정식 난류모델을 이용한 압축성 N-S 방정식을 적용하여 수치해석적(CFD) 연구를 수행하였다. 본 CFD 결과는 기존의 실험 데이터를 통해 검증되었으며 공압 배관의 입구 및 출구에서의 컨덕턴스와 마찰 계수의 값은 유량을 평가하기 위해 사용되었다. 본 결과는 컨덕턴스가 공압 배관의 입구 및 출구에서의 압력 비율에 의존한다는 것을 보여준다. Conductance is a concept contrary to flow resistance and is extensively used as a flow index on how easily fluid is transported through a pneumatic pipe or fluid device. However, research on flow conductance is very rare to date, and a systematic investigation is needed for the standardization of pneumatic devices. In the present study, a computational fluid dynamics method was applied to solve the compressible Navier?Stokes equations with two-equation turbulence models. The present CFD results were validated with existing experimental data. The conductance values and friction factors at the inlet and outlet of a pneumatic pipe were used to assess the flow rates. The present results showed that the conductance depends on the pressure ratio at the inlet and outlet of a pipe.

Case-based reasoning approach to estimating the strength of sustainable concrete

구충완,Ruoyu Jin,Bo Li,차승현,Dariusz Wanatowski 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.6

Continuing from previous studies of sustainable concrete containing environmentally friendly materials and existing modeling approach to predicting concrete properties, this study developed an estimation methodology to predicting the strength of sustainable concrete using an advanced case-based reasoning approach. It was conducted in two steps: (i) establishment of a case database and (ii) development of an advanced case-based reasoning model. Through the experimental studies, a total of 144 observations for concrete compressive strength and tensile strength were established to develop the estimation model. As a result, the prediction accuracy of the A-CBR model (i.e., 95.214% for compressive strength and 92.448% for tensile strength) performed superior to other conventional methodologies (e.g., basic case-based reasoning and artificial neural network models). The developed methodology provides an alternative approach in predicting concrete properties and could be further extended to the future research area in durability of sustainable concrete.

컨덕턴스의 개념을 사용한 공압관 시스템의 유량 예측

김진현(Jin-Hyeon Kim),Ruoyu Deng,김희동(Heuy-Dong Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

Conductance is a concept contrary to flow resistance and is extensively being used as a flow index on how easily fluid is transported through a pneumatic pipe or a fluid device. It can be very useful in specifying the characteristic values of flow rate regardless of the kind of the pneumatic devices and pipes used. ISO6358 states that the flow rate characteristics of pneumatic devices should be based on the sonic conductance and the critical pressure ratio in which flow is choked at a minimum cross sectional area of the devices. Such a regulation of flow rate characteristics is quite different from the flow rate equations concerned with incompressible flows. However, researches on the flow conductance are very rare to date and systematic investigation is needed for standardization of pneumatic devices. In the present study, a computational fluid dynamics method has been applied to solve the compressible Navier-Stokes equations with two-equation turbulence models. The present CFD results were validated with existing experimental data. Values of the conductances and friction factors at the inlet and outlet of a pneumatic pipe were used to assess the flow rates. The present results show that the conductance depends on the pressure ratio at the inlet and outlet of the pipe.

Investigation of Demographic Factors in Construction Employees’ Safety Perceptions

Yu Han,Ruoyu Jin,Hannah Wood,Tong Yang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7

This study focused on the effects of these demographic factors on construction employees’ safety perceptions. It first initiated a theoretical framework illustrating the impacts of demographic factors (i.e., education level, gender, and age) on employee’s perceptions towards pre-defined site hazards as well as their general safety perception. Then site questionnaire survey approach was adopted in nine construction jobsites in southeastern China followed by statistical analysis. The study revealed that construction employees’ education level, although not affecting their perceptions towards safety hazards/accidents, could create differences in other general safety perceptions between management staff and workers. Gender differences were found in safety perceptions of hazard/accident scenes and general safety perceptions, indicating that gender issue in safety perceptions applied consistently crossing different industries. Employees between 37 and 46 years old tended to underestimate safety risks from commonly encountered hazards, suggesting the needs of continued safety refreshers for employees in the middle of their career. This study contributed to the body of knowledge in safety perceptions by investigating the effect of three major subgroup or demographic factors, including education level, gender, and age, which had not been sufficiently addressed in construction safety subculture or sub-climate.

Analyzing the Key Drivers of Contractors’ Temporary Competitive Advantage in the Competition of International High-Speed Rail Projects

Qianwen Zhou,Xiaopeng Deng,Ruoyu Jin,Tengyuan Chang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.11

After temporary competitive advantage (TCA) being proposed, this concept has received a lot of attention from academia and industry. For international high-speed rail (HSR) contractors, how to form their TCA and win out over the competition for new projects is crucial, while only a few studies focus on this issue. This research aims to develop a TCA system that reflects the characteristics of HSR contractors in the corporation and project levels. At first, exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) was conducted to explore and examine the key drivers and their relationships with contractors’ TCA. The results revealed that experience-mining advantage was the most critical factor of the six common factors. Next, common factors were divided into three dimensions and discussed in-depth, including resource-based TCA (i.e., technical resource and social image) which had the highest significance, followed by performance-based TCA (experience-mining advantage and risk-controlling performance), and action-based TCA (i.e., funding strategy and organizational management). Finally, two case study projects were selected to investigate the competitive situation between CRH (China Railway High-speed) and Shinkansen (Japan) in the international HSR market. This study not only provides suggestions for contractors to improve their TCA in international HSR projects, but also contributes to the theoretical framework for the TCA theory.

Synthesis of poly[2-(3-butenyl)-2-oxazoline] with abundant carboxylic acid functional groups as a fiber-based sol–gel reaction supporter for catalytic applications

Wu Bin Ying,배기현,고나영,김수희,류삼곤,Jin Zhu,Ruoyu Zhang,이범재,이경진 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.80 No.-

Polymer-based catalysts have been of special interest because of their several advantages such as easyprocessibility. Inorganic catalyst generally have been introduced into polymer-based media to endowcatalytic activity. Surface decoration or sol–gel reaction have been performed so far, but inherent lowaffinity between organic/inorganic causes low efficiency in loading amount, resulting in low catalyticactivity. Herein, we synthesized easily processible and highly functionalizable polyoxazoline as polymernonwovenfiber-based catalytic supporter. Zr(OH)4 was grown on surface offiber-web via sol–gelreaction. The Zr(OH)4 grownfiber exhibited not only excellent mechanical properties but also effectivedecontamination efficiency against organophosphate-based toxic agents.