• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.259-262
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• 2002

Application of combustion stabilization devices such as baffle and acoustic cavity to liquid propellant rocket engine is investigated to suppress high-frequency combustion instability, i.e., acoustic instability. First, these damping devices are designed based on linear damping theory. As a principal design parameter, damping factor is considered and calculated numerically in the chambers with various specifications of these devices. Next, the unbaffled chambers with/without acoustic cavities are tested experimentally for several operating conditions. The unbaffled chamber shows the specific stability characteristics depending on the operating condition and has small dynamic stability margin. The most hazardous frequency is clearly identified through Fast Fourier Transform. As a result, the acoustic cavity with the present design has little stabilization effect in this specific chamber. Finally, stability rating tests are conducted with the baffled chamber, where evident combustion stabilization is observed, which indicates sufficient damping effect. Thrust loss caused by baffle installation is about $2{\%}$.

• 제어로봇시스템학회논문지
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• 제4권4호
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• pp.427-432
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• 1998

There are many demands for ship control system and many studies have been proposed. For example, if a ship diesel engine is operated by consolidated control with Controllable Pitch Propeller(CPP), the minimum fuel consumption is achieved, satisfying the demanded ship speed. For this, it is necessary that the ship is operated on the ideal operating line which satisfies the minimum fuel consumption. In this context of view, this paper presents a controller design method for a ship propulsion system with CPP by Linear Matrix Inequality(LMI) which satisfies the given $H_{\infty}$ control performance and robust stability in the presence of physical parameter perturbations. The validity and applicability of this approach are illustrated through a simulation in the all operating ranges.

• 한국군사과학기술학회지
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• 제8권4호
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• pp.152-158
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• 2005

In this paper, we have proposed a fuel metering unit of ai breathing engine. The proposed valve system consists of a constant pressure drop valve and a metering valve, which are controlled by servovalve. We carried out nonlinear and linear analysis, computer simulation and experimentation to find effects of some factors on system performance. Analysis and experimental results show a good agreement. It is also shown that the system stability is affected by pressure drop of metering valve and inlet pressure of injectors.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.73-79
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• 2002

The NO emissions at the exhaust manifo1d were investigated with a fast NO analyzer to investigate the cycle-by-cycle variations on NO emissions level and the dependence of NO emissions on combustion. The measurement was performed with a part load condition with respect to the mixture ratios and the changes in loads at 1800rpm. The averaged values were obtained during 200 cycles. We found that there is characteristic pattern in 70 emissions from exhaust port and it was possible to set a representative value with the data sampled during specific period. As the load increased, the characteristics of NO emissions were more dependent on combustion pressures. It was also analyzed that the correlation between combustion pressures and NO emissions for different equivalence ratios tends to increase as the mixture goes leaner, Furthermore, this correlation for the lean mixture near the lean limit seemed to be kept.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.128-136
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• 1997

Spray characteristics of a fuel injector have an important effect upon engine power and emission. Thus this study was investigated the spray characteristics of the intermittent injection using a gasoline fuel injector. Image processing system and PDA system were utilized for visualization of a spray behavior and measurements of a droplet size and velocity, respectively. Fuel injection duration was fixed with 3ms and injection pressure was varied such as 250kPa, 300kPa, 350kPa. for a high fuel injection pressure, spray tip arrival time was fluctuated at a vigorously disintegrated cross section. Axial velocity was linear correlated with fuel droplet size in the time interval of an injected main spray at spray downstream.

• 품질경영학회지
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• 제15권2호
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• pp.2-9
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• 1987

The Deterioration Factor (DF) for a single pollutant within an engine family is computed as the ratio of two points on a linear regression line describing durability vehicle test results as a function of accumulated mileage. It is inteded to represent the factor by which emissions will increase during the ''useful life" of a vehicle in the engine family. Here are discribed procedures for computing the DF and how consideration of the DF is included in the development for the motor vehicle emission certification process. This paper is aimed to develop the distribution of the DF for three pollutant and to estimate the parameter values for the distribution of the DF.

• International journal of advanced smart convergence
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• 제12권1호
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• pp.130-139
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• 2023

With the increasing popularity of computer-generated virtual influencers, the trend is rising especially on social media. Famous virtual influencer characters Lil Miquela and Imma were all created by CGI graphics workflows. The process is typically a linear affair. Iteration is challenging and costly. Development efforts are frequently siloed off from one another. Moreover, it does not provide a real-time interactive experience. In the previous study, a real-time graphic workflow was proposed for the Digital Actor Hologram project while the output graphic quality is less than the results obtained from the CGI graphic workflow. Therefore, a real-time engine graphic workflow for Virtual Influencers is proposed in this paper to facilitate the creation of real-time interactive functions and realistic graphic quality. The real-time graphic workflow is obtained from four processes: Facial Modeling, Facial Texture, Material Shader, and Look-Development. The analysis of performance with real-time graphical workflow for Digital Actor Hologram demonstrates the usefulness of this research result. Our research will be efficient in producing virtual influencers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.17-19
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• 2005

Variety of methods were discussed to reduce the cogging force in tubular permanent magnet type linear single phase AC generator. In paticular, the proposed methods depend on the variations of the permanent magnet construction. These methods Include two approaches in the form of sloped magnets, and conical magnets in addition to the conventional method of varying the magnet length. The undesired cogging force ripples were calculated by a two dimensional Finite Element Method(FEM). Moreover, the generated electromotive force in the stator coils was calculated fur each configuration of the permanent magnet. The experimental results agreed well with those obtained from the FEM-based simulations. Sufficient reduction in the cogging force was achieved over the range of 40% while the root mean square of the output voltage was maintained. It was found that the sloping the permanent magnet decreased the cogging force and at the same time increased the generated rms voltage of the AC generator. The performance of the designed linear AC generator was evaluated in terms of its efficiency, total weight, losses, and power to weight ratio.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권5호
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• pp.241-248
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• 1999

Recently, many linear motion generators and motors are rapidly finding applications that ranges from short stroke linear motion vibrators, such as dynamic cone type loudspeakers to stirling engine driven linear reciprocating alternators, compressors, textile machines etc. The stroke-length may go up to 2m, and the maximum speed is in the range of 5 to 10m/s with oscillating frequency as high as 15 kHz. Therefore, the linear oscillating actuators(LOAs) may be considered as variable speed drivers of precise controller with stoke-length and reversal periods during the reciprocating motion. In this paper, the design, fabrication, experiments, and extraction of control parameters of a moving coil type LOA for driving of linear reciprocating motion control systems, are treated. The actuator consists of the NdFeB permanent magnets with high specific energy as the stator produced magnetic field, a coil-wrapped nonmagnetic hollow rectangular bobbin structure, and an iron core as a pathway for magnetic flux. Actually, the design is accomplished by using FEM analysis for the basic configuration of a magnetic circuit, and characteristic equations for coil design. In order to apply as the drivers of a linear motion reciprocating control system, the control parameters and circuit parameters, such as input voltage-stoke, exciting frequency-stoke, coil inductance and so on, are extracted from the analysis and experiments on concerning a fabricating LOA.

• 한국추진공학회지
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• 제2권3호
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• pp.99-106
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• 1998

현재 국내에서 개발되어왔던 중형항공기 후보엔진인 터보팬 엔진의 성능해석과 성능최적화를 위한 제어기법을 연구하였다. 선행된 연구에서 동적모사 및 실시간 선형모사를 수행한 결과 지상 정지조건 하에서 70% 엔진로터 회전수에서 100% 엔진로터 회전수로 급상승하는 경우 고압터어빈 입구온도에서 오버슈트가 발생하여 제한온도인 3105 $^{\cire}R$ 을 넘어감을 확인할 수 있었다 또한 압축기의 서지여유도 협소하여 엔진에 손상을 가져올 수 있다. 이에 본 연구에서는 보다 빠른 가속성능과 함께 엔진 성능의 최적화를 위해 LQR 제어기를 설계하였다. 제어기의 설계를 위해서는 선형모델을 구성해야하며 엔진의 비선형 거동에 보다 근접한 선형화를 위해서는 실시간 선형모사가 요구된다. 선형모델에 필요한 행렬은 자동점에 %의 섭동을 주어 5% 간격으로 구하였으며, 최소자승법을 이용하여 저압 엔진로터 회전수의 함수로 보간하는 방법으로 실시간 선형모사를 수행하였다. 제어변수는 연료유량의 증가속도와 압축기 블리드 공기유량으로 하였으며, 제어 결과 고압 터빈입구온도의 오버슈트를 제거하였으며 최대 압축기 서지여유도 0.55 이하로 확보였다. 비연료소모율도 0.353에서 0.43으로 안정됨을 확인할 수 있었다.