• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.36-46
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• 2000

The performance improvement and emission reduction in a turbocharged D.I. diesel engine was studied experimentally in this paper. The system of intake port, fuel injection and turbochager are very important factors which have influence on the engine performance and exhaust emission because the properties in the injected fuel depend on the combustion characteristics. Through these experiments it can be expected to meet performance and emission by optimizing the main parameters; the swirl ratio of intake port, fuel injection system and turbocharger. The swirl ratio of intake port was modified by hand-working and measured by impulse swirl meter. Through this steady flow test, we knew that the increase of swirl ratio is decreasing the mean flow coefficient, whereas the gulf factor is increasing. And the optimum results of engine performance and emission are as follows; the swirl ratio is 2.43, injection timing is BTDC 13。 CA, compression ratio is 16, combustion bowl is re-entrant 5$^{\circ}$, nozzle hole diameter is $\Phi$0.28＊6, turbocharger is GT40 model which are compressor A/R 0.58 AND turbine A/R 1.19.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.1-11
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• 2004

In order to recognize thermal efficiency and power improvement in case that diesel cycle is turned into diesel-atkinson cycle, the fuel-air diesel-atkinson cycle considered gas exchange process is analyzed non-dimensionally and thermodynamically. As a result, in case of diesel-atkinson cycle, as expansion ratio is increased, thermal efficiency and mean effective pressure is increased and it has maximum value at Rec=1. When diesel cycle is turned into diesel-atkinson cycle by late intake valve closing timing, thermal efficiency and power is decreased because of the decline of effective compression ratio and intake airflow, but it could be compensated by increase of compression ratio or super-charged. In case compression ratio is compensated, Rec appears 1 around 100$^{\circ}$ ABDC, and it is expected that thermal efficiency is enhanced by 14.3% compared with conventional diesel cycle. In case compression ratio and intake airflow are compensated simultaneously, super-charged pressure is demanded 2.06bar at Rec=1 and it is more efficient when only compression ratio is compensated in the view point of thermal efficiency.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.69-74
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• 2016

Most hot water heating valves for apartments are constant-flow types, which limit the flow rate through an individual household for even distribution of heating water to other households. The constant-flow type is implemented by an on-off control. As a result, heating water is supplied intermittently and hence, indoor air temperature also fluctuates. Returning water temperature is also high, which reduces energy efficiency. To implement continuous feedback control, the indoor temperature dynamics was simulated to fit a measured temperature history by a state-of-the-art physical model. From the model, it was found that the most important disturbance is outdoor temperature and its effect on indoor temperature lasts about an hour. To cope with the slow response and the significant disturbance, a prediction control with proportional feedback is proposed. The control was found to be successful in implementing continuous heating water flow and improved indoor temperature control.

• The KSFM Journal of Fluid Machinery
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• v.20 no.2
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• pp.17-25
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• 2017

Prediction of performance and operating characteristics of a state-of-the-art ultra-supercritical (USC) steam turbine is an important issue in many ways. Theoretical and empirical correlation equations, developed a few decades ago, have been widely used in commercial programs for a prediction of performance. To improve of these correlation equations and apply them to the high pressure turbine of a USC steam turbine, computational fluid dynamic analysis was carried out and correlation equations to calculate efficiency variation of each stage were made. Both fluid dynamic characteristic and thermodynamic performance was analyzed for the development of the correlation equations. In particular, the impact of flow addition through an overload valve (OLV) between stages was examined throughly. The trend of pressure drop due to the flow mixing by the OLV flow addition was analyzed and an efficiency correlation equation considering the OLV flow was also made.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.5
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• pp.20-27
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• 2010

In this study, we improved problems in the existing product by PARKER and developed the swivel valve tube couplers that can be produced by a low price in Korea. The major development was that a modulized production method was implemented by introducing a part assembling method that uses a cocking jig, and the production cost was reduced by operating the production process more simply than that of PARKER. Also, it was possible to avoid the patient registered by PARKER through the differences in the number of grooving processes and the type of o-ring. In the results of the rotation test by varying its application angle after installing it to a vehicle, it was verified that the structure proposed in this study can endure the eccentric torque and transformation pressure for various angles that have been considered as the problem in the existing fixed tube couplers. In addition, the structure was developed to adopt the problem that represents differences in the installation position of an air tank or the length and direction of hoses according to the type of vehicles produced in vehicle manufacturers. Furthermore, it was possible to verify that the product developed in this study was more excellent than that of PARKER through comparing the performance according to the Federal Motor Vehicle Safety Standard.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.6
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• pp.257-262
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• 2014

This paper describes an experimental study for heating performance that can be used in R-134a automobile heat pump systems. The heat pump system is widely studied for heating system in zero-emission vehicles to attain both the small power consumption and the effective heating of the cabin. This paper presents the experimental results of the influence on heating capacity and coefficient of performance of heat pump system. Tests were performed with different sizes of internal and external heat exchangers, and refrigerant flow rate was also considered in two-way flow devices. In addition, the heat, air, and water sources with the heat pump system were examined. The experimental results with the heat pump system were used to analyze the impact on performances. The best combination of performance was A-inside heat exchanger, B-outside heat exchanger, and B-flow device, respectively. In addition, a water heat-source was found to give roughly 40% of better performance than an air heat-source heat pump system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.9
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• pp.361-366
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• 2016

As an alternative of well-mixed storage tank with lower coil only, we have proposed a tank with lower and upper coils and verified a superior thermal stratification in a tank, which results in increased collector efficiency and solar fraction. But the phenomenon of temperature reversal was often experimentally observed in the tank, so a revised control was successfully applied which is to heat only lower coil using three way valve if temperature reversal occurs and to operate the collector with low flow rate when the condition of solar radiation is not good. In the present study, using TRNSYS we compared the existing lower heating and the proposed lower and upper heating with a control preventing temperature reversal. The results showed that the proposed method has an increase of collector efficiency by 5.1% and solar fraction by 3.2%.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.5
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• pp.625-632
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• 2014

It is required a lot of strength in aquaculture, such as dragging up or moving heavy loads. So, a helper system like excavator at construction is need for fishermen. As most of HFMSC(Hydraulic Fishery Managing Small Crane)s are operated based on ON/OFF control, it can make sway the contents in the crane. In worse case, it could threaten workers. In this paper, we development the MICOM based controller which can reduce the swing sway. This paper describes the hydraulic characteristics, the design method of controller and the control algorithms. And, the proposed controller show the efficiency to carry out the experimental validation.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.701-706
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• 2007

Recently, a number of researches about linear magnetorheological(MR) damper using valve-mode characteristics of MR fluid have sufficiently undertaken, but researches about rotary MR damper using shear-mode characteristics of MR fluid are not enough. In this paper, we performed vibration control of shear-mode MR damper for unlimited rotating actuator of mobile robot. Also fuzzy logic based vibration control for shear-mode MR damper is suggested. The parameters, like scaling factor of input/output and center of the triangular membership functions associated with the different linguistic variables, are tuned by genetic algorithm. Simulation results demonstrate the effectiveness of the fuzzy-skyhook controller for vibration control of shear-mode MR damper under impact force.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.374-377
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• 2006

본 논문은 에어컨 시스템의 효율성과 안정성에 기초하여, 과열도와 저압을 제어하는 Fuzzy 제어기 설계를 제안한다. 에어컨 시스템은 Compressor(압축기), Condenser(응축기), Evaporator(증발기), Expansion Valve(확장 밸브) 로 구성되며, 각각의 기기에 대한 제어가 독립적으로 이루어져 있다. 기존의 제어가 한 제어기를 사용한 단일방식으로 이루어지다보니 에어컨 시스템의 특성인 냉매의 상태가 달라지면 시스템 전반적으로 그 영향이 파급되는 부분까지 고려를 해 주지 못하고, 제어기의 성능이 효율적이고 안정적이지 못했다. 본 논문에서는 에어컨 시스템의 효율과 안정도에 결정적인 영향을 미치는 과열도와 저압(증발기의 압력)을 제어하기 위해, 비선형성이 강하고 불확실하며 복잡한 시스템을 쉽게 제어할 수 있는 Fuzzy 제어기를 구성하여, Expansion Valve 와 Compressor 에서 동시에 제어하는 Multi 제어기를 설계한다. 제안된 Fuzzy 제어기는 이산형 lookup_table 방식과 연속형 간략추론 방식을 사용하여 제어기를 설계하고, 유전자 알고리즘(GAs)을 이용하여 최적의 Fuzzy 제어기의 환산계수를 구한다. 그리고 시뮬레이션 결과를 통해 이산형 lookup_table 방식과 연속형 간략추론 방식의 각각의 제어기를 사용한 결과를 비교한다.