• 기계저널
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• 제30권6호
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• pp.564-571
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• 1990

최근의 기관은 DOHC 또는 SOHC로 4밸브나 5밸브를 채용하여 흡기계의 효율향상을 시도하고 있다. 그러나 고속성능에 중점을 두고 기관제원을 설정하게 되면서 저속 실용역에서 토크의 저하를 초래하는 경우가 많아지고 있으며 금후 이러한 문제의 해결에 많은 노력이 계속될 것으로 전망된다. 또한 전자기술의 발전과 자동차에 대한 적용 기술이 향상됨에 따라 앞으로 가변흡기 시스템, 가변밸브 타이밍, 가변 터보, 가변 기통수, 가변 압축비등 가변기술에 대한 연구개발이 더욱 활발히 이루어질 것이다.

• 한국수소및신에너지학회논문집
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• 제18권1호
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• pp.67-74
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• 2007

고효율의 실현이 가능한 흡기관 분사식 수소기관의 역화 억제 가능성을 파악하고자 밸브 오버랩 기간의 변화에 따른 제반 기관성능과 역화가 발생되는 역화한계 당량비를 실험적으로 해석하였다. 실험에는 기계식 연속 가변밸브 타이밍 시스템이 부착된 연구용 수소기관을 사용하였다. 밸브 오버랩기간은 배기밸브 개폐시기를 고정하고 흡기밸브 캠의 위상각을 조절하여 변화시켰다. 해석결과 밸브 오버랩 기간의 감소에 따른 제반기관성능은 통상의 기관과 유사하지만 역화한계 당량비가 확장되어 초기 단계이지만 수소기관의 역화발생에 밸브오버랩 기간이 관여하는 것이 보였다. 기관 회전수 1600 rpm, WOT의 실험 조건에서 밸브 오버랩 기간을 $20^{\circ}CA$에서 $0^{\circ}CA$로 감소시킨 경우 역화한계당량비는 약 45% 정도 확장되고 정미 토크는 16% 감소했다.

• 한국자기학회지
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• 제20권1호
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• pp.24-27
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• 2010

솔레노이드 전자기 엔진 밸브 액츄에이터는 현재의 내연 연소 엔진의 가변 밸브 타이밍에 가장 적합하고 진보된 장치이다. 하지만 솔레노이드 전자기 액츄에이터는 전력소모가 크다는 단점을 가지고 있다. 따라서 전력소모가 작은 가변 밸브 타이밍을 구현하기 위해 영구자석을 활용한 새로운 전자기 엔진 밸브 액츄에이터를 제안한다. 이 연구에서는 엔진 밸브의 과도운동 시간의 최소화를 통해 엔진의 속도를 극대화하기 위하여 새롭게 제안한 액츄에이터의 형상을 최적 설계하였다. 최적화를 위해 유전자 알고리즘을 사용하고 Matlab과 Maxwell을 활용하여 전역 최적화 시뮬레이션을 수행하였다.

• 한국정밀공학회지
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• 제25권9호
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• pp.53-58
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• 2008

The traditional engine valve train in a combustion engine is the mechanically driven camshaft system that provides one-fixed valve timing. The variable valve timing (VVT), however, is highly required to achieve the significant improvement in fuel economy. To achieve VVT in combustion engine, the solenoid type of actuator had been developed in past years, but it requires current in all operation period, the starting is difficult and the efficiency is low. In this paper, a new linear actuator using permanent magnet (PM) is proposed and verified its feasibility by finite element (FE) analysis.

• Journal of Advanced Marine Engineering and Technology
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• 제33권8호
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• pp.1100-1106
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• 2009

최근, 디젤기관의 고효율달성을 위한 방법으로 밀러방식의 고팽창사이클에 대한 연구가 관심이 높다. 본 연구에서는 고팽창 디젤사이클을 구성하여 열역학적으로 해석하고, 몇몇 인자에 의한 사이클 특성을 분석하였다. 이론해석 결과 흡기밸브 닫힘시기가 지각될수록 유효압축비의 감소로 상대적인 팽창비의 효과는 커져 팽창-압축비의 비는 기대할 수 있었으나, 압축압력 및 흡입공기의 역류로 인해 평균유효 압력과 출력의 감고를 수반하였다. 따라서 이에 대한 대책이 있어야 진정한 의미의 고팽창 디젤사이클이 실현되고 열효율향상 가능성이 있음이 확인되었다. 위와 같은 사이클을 실제기관으로부터 구현하기 위해 흡기밸브 닫힘시기를 늦게 하는 제어시스템을 구축하고, 시험을 위해서 S/B가 약 3인 저속 단기통 디젤기관에 가변밸브타이밍(VVT)시스템을 적용하여 성능을 평가하였다. 그 결과 시험기관의 밸브제어에는 큰 문제없는 것으로 평가되었다.

• 한국분무공학회지
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• 제25권2호
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• pp.45-50
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• 2020

Recently, global warming and environmental pollution are becoming more important, and fuel economy is becoming important. Each automobile company is actively developing various new technologies to increase fuel efficiency. CVVD(Continuously Variable Valve Duration) system means a device that continuously changes the rotational speed of the camshaft to change the valve duration according to the state of the engine. In this paper, VVT(Variable Valve Timing) and CVVD were applied to a single-cylinder diesel engine, and the characteristics of intake and exhaust flow rate and in-cylinder pressure characteristics were analyzed by numerical analysis. In order to analyze the effect of CVVD on the actual engine operation, the study was performed by setting the valve control and injection pressure as variables in two sections of the engine operating region. As a result, In the case of applying CVVD, the positive overlap with the exhaust valve is maintained, thus it is possible to secure the flow smoothness of air and increase the volumetric efficiency by improving the flow rate. The section 2 condition showed the highest peak pressure, but the pressure rise rate was similar to that of the VVT 20 and CVCD 20 conditions up to 40 bar due to the occurrence of ignition delay.

• 대한기계학회논문집B
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• 제29권3호
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• pp.384-389
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• 2005

Experimental study of variation of exhaust gas temperature was carried out with the changes of spark timing and exhaust valve timing during the cold start operation of an SI engine. To investigate the effects of these variables on combustion stability, cylinder pressure and exhaust gas temperature were measured and analyzed. Experimental results showed that exhaust gas temperature increased when spark and exhaust valve timings were retarded from the baseline cases. However, combustion stability during cold start deteriorated under the retarded conditions. To increase exhaust gas temperature for fast warmup of catalysts while maintaining combustion stability, an optimal condition for spark and valve timing retard should be appied for the cold start period.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3108-3113
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• 2008

This paper investigated the behaviors of combustion characteristics at part load condition with various intake charge motions induced by the port masking schemes in the CVVT (Continuously Variable valve Timing) engine. Time resolved in-cylinder and exhaust emissions were measured by the fast response HC and NOx analyzers to examine their formation mechanisms and behavior characteristics. As a result, in-cylinder HC decreased with the advanced intake valve timings but HC at the exhaust port increased due to the worse combustion stabilities. However HC reduction could be achieved by the application of the port maskings with a enhancement of the engine stability. NOx also decreased with early intake timings by internal EGR but increased with the charge motion controls which enhance the combustion behavior.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.42-49
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• 2006

In this research. the diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting diesel engines to the high expansion diesel cycle, and general cycle features were analyzed after comparing these two cycles. Based on these analyses. an experimental single cylinder a long stroke with high expansion-diesel engine. of which S/B ratio was more than 3, was manufactured. After evaluating the base engine through basic experiments, a diesel engine was converted into the high expansion diesel engine by establish VCR device and VVT system Accordingly, the high expansion diesel cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case, heat efficiency increased by $5.0\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle, heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged pressure equipment. Then a high expansion diesel cycle engine is realized.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.82-88
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• 1999

The object of this study is to find new evaluation index for in-cylinder flow chracteristics istead of current swirl, tumble coefficient using steady flow test rig on intake port system. To this end, port flow system. To this end, port flow rig test was conducted on DOHC head varying intake valve lift respectively. Finally combination angular coefficient and inclination angle were introduced as new evaluation index for in-cylinder angularflow characteristics instead of swirl and tumble coefficient.