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박석범,구자예,Park, Seok Beom,Koo, Ja Ye 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.8
Computational investigation was conducted to examine the performance of a high pressure common-rail fuel injection system which is used to power a passenger car direct injection (Dl) diesel engine. The pipe flows were modeled by one dimensional wave equation and solved by implicit FDM Each volume of injector was considered as chambers with orifice nozzle in connections. These simulation results were compared with the experimental data of Ganser Hydromag. The comparison of needle life and rate of injection between simulation data and experimental data showed quite a good agreement Different shape of injection rate can be made by adjusting the size of inlet orifice and exit orifice in the piston chamber The pilot injection was accomplished by adjusting command signal.
가압 분무실내 스프레이 충돌판에서 나타나는 비정상 열전달 측정에 관한 연구
조창권,이열,구자예,Cho, Chang-Kwun,Lee, Yeol,Koo, Ja-Ye 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.1
An experimental investigation on transient heat transfer phenomena of impinging diesel-spray on a flat plate in a pressurized chamber is carried out. A diesel spray is injected from a single-hole nozzle and impinges to a heated flat plate in the chamber. A fast-response thermocouple installed in the top surface of the plate measures the transient variation of surface temperature of the plate under various conditions of the chamber pressures. Utilizing the semi-infinite model, the temporal variation of the heat flux on the plate is determined. Effects of various parameters, such as vertical distances between the nozzle and the plate, radial distances from the injection-axis, and the chamber pressures, on the heat flux characteristics of impinging diesel-spray are studied.
이봉수,이경재,김종현,구자예,Lee, Bong-Su,Lee, Kyung-Jae,Kim, Jong-Hyun,Koo, Ja-Ye 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.11
Droplet combustion at high ambient pressures is studied numerically by formulating one dimensional combustion model in the mixture of n-heptane fuel and air. The ambient pressure is supercritical conditions. The modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties to account for the real gas effect on fluid p-v-T properties in high pressure conditions. Non-ideal thermodynamic and transport property at near critical and supercritical conditions are also considered. Several parametric studies are performed by changing ambient pressure and initial droplet diameter. Droplet lifetime decreased with increasing pressure. Surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.
나노유체를 이용한 차세대 냉각 유체의 난류유동 특성 연구
장원재(Won Jae Jang),구자예(Ja Ye Koo),문희장(Hee-Jang Moon),장석필(Seok Pil Jang) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this study, nanofluids characteristics containing Al₂O₃ nanoparticles of 0.3% volume fraction suspended in base fluids are investigated. The fluid flow characteristics of nanofluids are experimentally found in the turbulent domain. The turbulent flow measurement is carried through an experiment rig using water pump as the pumping system, where friction factor for both base fluid and nanofluids are studied. Measurement of flow rate and pressure drop in the test section is followed with the uncertainty analysis. The applicability of the nanofluids for the next generation coolant is suggested by comparing the friction factor values and pressure drop of both fluids.
이준(Jun Lee),구자예(Ja ye Koo),박성우(Sungwoo Park) 한국연소학회 2022 KOSCOSYMPOSIUM논문집 Vol.2022 No.11
This study focused on the combustion characteristics of premixed NH₃/air flames in terms of improved Ammonia combustion kinetic model and NOx Emission. To understand premixed NH3/air flame characteristics, previously published chemical kinetic models were used for the present study. For confirming the capability of the models, laminar burning velocity (LBV) and ignition delay time were compared with experimental results. After that, the tendency of NOx emission according to equivalence ratio was derived from the perspective of temperature, NH3, and NO. Major chemical reactions affecting NOx production were analyzed through the NOx production pathway using rate of production and sensitivity analysis of NO at equivalence ratio of 0.9 and 1.2
터보팬 엔진의 축류압축기 서지가 엔진성능에 미치는 영향
오창용(Chang-Yong Oh),구자예(Ja-Ye Koo) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.5
본 연구에서는 PW4000 엔진의 축류압축기 서지 발생이 엔진성능에 미치는 영향에 대하여 연구하였다. EPR은 서지 발생과 동시에 급격히 저하하는 것으로 나타나 민감도가 가장 큰 파라미터였다. N1 rpm과 N2 rpm도 EPR과 거의 동일한 경향으로 감소하였으며, Vibration 변화는 크지 않았으나 N1 Vibration 변화가 상대적으로 크게 나타났다. 따라서 비행중 EPR, N1 rpm, Wf 값이 급격히 저하되고 EGT가 비선형적으로 상승하는 상태로서 서지 발생을 감지할 수 있을 것으로 판단된다. This thesis has analyzed the effect of the surge happening in flight on the engine performance of the PW4000 turbofan engine. EPR is judged to be the most highly sensitive parameter responding when surge occurs. Both N1 rpm and N2 rpm decreases almost simultaneously just like an EPR. During the take-off rolling, the N1 vibration is more sensitive than the N2 vibration. Consequently, the surge can be detected by EGT increase, while the other parameters decrease.