EVALUATION OF LOW-TEMPERATURE DIESEL COMBUSTION REGIMES WITH n-HEPTANE FUEL IN A CONSTANT-VOLUME CHAMBER

U. B. AZIMOV,김기성,정동수,이용규 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.3

The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot simultaneously Various LTC regimes that yield specific emissions have been investigated by a great number of experiments. To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC, and to implement the LTC concept in real diesel engines, LTC is modeled and simulated. However, since the physics of LTC is rather complex, it has been a challenge to precisely compute LTC regimes by applying the available diesel combustion models and considering all spatial and temporal characteristics as well as local properties of LTC. In this paper, LTC regimes in a constant-volume chamber with n-Heptane fuel were simulated using the ECFM3Z model implemented in a commercial STAR-CD code. The simulations were performed for different ambient gas O2 concentrations, ambient gas temperatures and injection pressures. The simulation results showed very good agreement with available experimental data, including similar trends in autoignition and flame evolution. In the selected range of ambient temperatures and O2 concentrations, soot and NOx emissions were simultaneously reduced. The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot simultaneously Various LTC regimes that yield specific emissions have been investigated by a great number of experiments. To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC, and to implement the LTC concept in real diesel engines, LTC is modeled and simulated. However, since the physics of LTC is rather complex, it has been a challenge to precisely compute LTC regimes by applying the available diesel combustion models and considering all spatial and temporal characteristics as well as local properties of LTC. In this paper, LTC regimes in a constant-volume chamber with n-Heptane fuel were simulated using the ECFM3Z model implemented in a commercial STAR-CD code. The simulations were performed for different ambient gas O2 concentrations, ambient gas temperatures and injection pressures. The simulation results showed very good agreement with available experimental data, including similar trends in autoignition and flame evolution. In the selected range of ambient temperatures and O2 concentrations, soot and NOx emissions were simultaneously reduced.

OPTIMIZATION OF INTAKE PORT DESIGN FOR SI ENGINE

Y. L. QI,L. C. DONG,H. LIU,P. V. PUZINAUSKAS,K. C. MIDKIFF 한국자동차공학회 2012 International journal of automotive technology Vol.13 No.6

It is well known that in-cylinder flow is very important factor for the performance of SI engine. An appropriate in-cylinder flow pattern can enhance the turbulence intensity at spark time, therefore increasing the stability of combustion, reducing emission and improving fuel economy. In this paper, the effect of intake port design on in-cylinder flow is studied. It is found a vortex existed at the upper side of intake port of a production SI engine used in the study, during the intake stroke, which will reduce both tumble ratio and volumetric efficiency. A minor modification on intake port is made to eliminate the vortex and increase tumble ratio while keeping volumetric efficiency at the same level. It is demonstrated that the increase in tumble in the new design results in a 20 per cent increase in the fuel vaporization. In this study, both KIVA and STAR-CD are used to simulate the engine cold flow, as well as ICEM CFD and es-ice used as pre-processor respectively due to the complexity of engine geometry. Simulation results from KIVA and STAR-CD are compared and analyzed.

STAR-CCM+를 활용한 자동차 공기역학적 성능 개선 디자인 연구

정현지(Hyunji Jung),김정용(Jeongyong Kim),최웅철(Woongchul Choi) 한국자동차공학회 2016 한국자동차공학회 학술대회 및 전시회 Vol.2016 No.11

It is important to develop design reducing air resistance for improving fuel consumption of vehicle. Specific of air resistance is different each types of vehicle, so it is necessity to understand each aircraft specific of types for developing improvement aerodynamic design. For example, air resistance of Notchback is usually occurred on c-pillar and rear turbulence. In this paper, developed design for reducing vortex of c-pillar of Notchback and confirmed air flux and reducing drag coefficient of aerodynamic improvement design model by using STAR-CCM+.

화재시 연기거동에 관한 실험 및 해석적 연구

신이철(Shin, Yi-Chul),김수영(Kim, Soo-Young),이주희(Lee, Ju-Hee),권영진(Kwon, Young-Jin) 한국화재소방학회 2008 한국화재소방학회 학술대회 논문집 Vol.2008 No.춘계

A study on the fire and smoke behavior on experiments and analysis through STAR-CD in using about behavior analysis of the smoke. Kerosene of 3L in using on the experimental garden of 30cm in diameter same applies to heat release rate(HRR), buoyant force by Plume can be calculated at a rate of 1m/s. The result of experiment in average of velocity were 0.29m/s, and interpreted result were 0.28m/s. Besides, it is proved by interpreted that behavior of smoke movement can be not observed in the experiment. After smoke is Plume increased, ceiling-jet in formation being descend in smoke layer will be more thick smoke layer, and then vertical wall is collapsed in formation of wall-jet being descend. It is defined that smoke layer is more thick through descending course in wall-jet and ceiling-jet.

원심형 날개를 부착한 축류홴의 유동특성 해석

최중근,이석종,이명호,성재용,Choi Jung-Geun,Lee Seok-Jong,Lee Myoeng-Ho,Sung Jae-Yong 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.5

This study aims to propose a new model axial flow fan which attachs centrifugal blades, and to investigate the effect of centrifugal blades on the performance improvement of new model axial flow fan. A numerical simulation has been conducted using STAR-CD commercial code to solve the three dimensional incompressible Navier-Stokes equation for high Reynolds number $k-{\epsilon}$ turbulent model. Numerical simulation is carried out to investigate the detail phenomenon in the flow field and performance characteristics of new model and normal model fan. Calculation results are compared with normal model's results to investigate which centrifugal blades effect on velocity profile and pressure distribution at various flow field positions. and calculation results show that new model fan can improve the performance of total pressure.

CFD ANALYSIS OF HEAVY LIQUID METAL FLOW IN THE CORE OF THE HELIOS LOOP

A. BATTA,JAE HYUN CHO,A.G. CLASS,IL SOON HWANG 한국원자력학회 2010 Nuclear Engineering and Technology Vol.42 No.6

Lead-alloys are very attractive nuclear coolants due to their thermo-hydraulic, chemical, and neutronic properties. Byutilizing the HELIOS (Heavy Eutectic liquid metal Loop for Integral test of Operability and Safety of PEACER2) facility, athermal hydraulic benchmarking study has been conducted for the prediction of pressure loss in lead-alloy cooled advancednuclear energy systems (LACANES). The loop has several complex components that cannot be readily characterized withavailable pressure loss correlations. Among these components is the core, composed of a vessel, a barrel, heaters separatedby complex spacers, and the plenum. Due to the complex shape of the core, its pressure loss is comparable to that of the restof the loop. Detailed CFD simulations employing different CFD codes are used to determine the pressure loss, and it is foundthat the spacers contribute to nearly 90 percent of the total pressure loss. In the system codes, spacers are usually accountedfor; however, due to the lack of correlations for the exact spacer geometry, the accuracy of models relies strongly on assumptionsused for modeling spacers. CFD can be used to determine an appropriate correlation. However, application of CFD alsorequires careful choice of turbulence models and numerical meshes, which are selected based on extensive experience withliquid metal flow simulations for the KALLA lab. In this paper consistent results of CFX and Star-CD are obtained andcompared to measured data. Measured data of the pressure loss of the core are obtained with a differential pressure transducerlocated between the core inlet and outlet at a flow rate of 13.57kg/s

CFD ANALYSIS OF HEAVY LIQUID METAL FLOW IN THE CORE OF THE HELIOS LOOP

Batta, A.,Cho, Jae-Hyun,Class, A.G.,Hwang, Il-Soon Korean Nuclear Society 2010 Nuclear Engineering and Technology Vol.42 No.6

Lead-alloys are very attractive nuclear coolants due to their thermo-hydraulic, chemical, and neutronic properties. By utilizing the HELIOS (Heavy Eutectic liquid metal Loop for Integral test of Operability and Safety of PEACER$^2$) facility, a thermal hydraulic benchmarking study has been conducted for the prediction of pressure loss in lead-alloy cooled advanced nuclear energy systems (LACANES). The loop has several complex components that cannot be readily characterized with available pressure loss correlations. Among these components is the core, composed of a vessel, a barrel, heaters separated by complex spacers, and the plenum. Due to the complex shape of the core, its pressure loss is comparable to that of the rest of the loop. Detailed CFD simulations employing different CFD codes are used to determine the pressure loss, and it is found that the spacers contribute to nearly 90 percent of the total pressure loss. In the system codes, spacers are usually accounted for; however, due to the lack of correlations for the exact spacer geometry, the accuracy of models relies strongly on assumptions used for modeling spacers. CFD can be used to determine an appropriate correlation. However, application of CFD also requires careful choice of turbulence models and numerical meshes, which are selected based on extensive experience with liquid metal flow simulations for the KALLA lab. In this paper consistent results of CFX and Star-CD are obtained and compared to measured data. Measured data of the pressure loss of the core are obtained with a differential pressure transducer located between the core inlet and outlet at a flow rate of 13.57kg/s.

A Simulation Analysis on the Effect of the Change in Cavity Profile on the Inner Cylinder Flow and Combustion Characteristics

Chunming Liao,Jongsang Park,Jeongkuk Yeom,Sumgsik Chung,Jongyul Ha 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

In order to investigate the mixture forming and combustion quality, finding the rule of performance influenced by the shape of combustion chamber, atomization and combustion of fuel in different geometrical combustion chambers was calculated using STAR-CD. The results show that the shape of chamber plays an important role to combustion process. The contracted cavity (A) has much strong squish lasting long-term period and distributing reasonably, which is favor to formation of the mixture. The diffuse combustion could be enhanced with higher pressure and temperature, which demonstrates chamber (A), has the best performance. The engine performance with chamber (B) is correspondingly worse, and chamber (C) is the worst. But thermal stress of chamber A is higher, and residual gas is not easy to be discharged.

A Flow Analysis of a Refrigeration Warehouse where an Unusual Death of an Operator Occurred by Deficiency of Oxygen

Park, Chan-Seong,Moon, Jung-Eun,Kim, Yoon-Ho,Kim, Jin-Pyo The Korean Society of Safety 2006 International Journal of Safety Vol.5 No.2

A numerical flow analysis of the case of a refrigeration warehouse where an unusual death of an operator occurred by deficiency of oxygen is performed by using STAR-CD program of the computational fluid dynamics (CFD) code. The refrigeration room of the warehouse for storing the fruits maintains an atmosphere of 95% nitrogen and 5% oxygen by volume. When the operator was found dead in the refrigeration room, the room was in normal operating conditions except for the fact that the auxiliary door had been left open. For the flow analysis, unsteady 3-dimensional natural convection with mass transfer is considered. The flow analysis result is compared with the oxygen concentration level measured against time during on-site investigation. The change in oxygen concentration level in the warehouse due to the opening of the auxiliary door is found to be negligible.

AA5083-H18판재의 마찰 교반 점 용접 공정에 대한 전산 해석

김돈건(Dongun Kim),Badarinarayan Harsha,유일(Ill Ryu),김지훈(Ji Hoon Kim),김종민(Chongmin Kim),Okamoto Kazutaka,Wagoner R. H.,정관수(Kwansoo Chung) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5

Thermo-mechanical simulation of the Friction Stir Spot Welding (FSSW) processes was performed for the AA5083-H18 sheets, utilizing commercial Finite Element Method (FEM) and Finite Volume Method (FVM) which are based on Lagrangian and Eulerian formulations, respectively. The Lagrangian explicit dynamic FEM code, PAM-RASH, and the Eulerian Computational Fluid Dynamics (CFD) FVM code, STAR-CD, were utilize to understand the effect of pin geometry on weld strength and material flow under the unsteady state condition Using FVM code, material flow pattern near the tool boundary was analyzed to explain the weld strength difference between the weld by cylindrical pin and the weld by triangular pin, while the frictional energy concept using the FEM code had limitation to explain the weld strength difference.