• 한국자동차공학회논문집
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• 제20권4호
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• pp.25-32
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• 2012

Cold start driving cycles exhibit an increases in friction losses due to the low temperatures of metal components and media compared to the normal operating engine conditions. These friction losses are adversely affected to fuel economy. Therefore, in recent years, various techniques for the improvement of fuel economy at cold start driving cycles have been introduced. The main techniques are the upward control of coolant temperature and the fast warm-up techniques. In particular, the fast warm-up techniques are implemented with the coolant flow-controlled water pump and the WHRS (waste heat recovery system). This paper deals with an effect of fast ATF (automatic transmission fluid) warm-up on fuel economy using a recovery system of EGR gas waste heat in a diesel engine. On a conventional diesel engine, two ATF coolers have been connected in series, i.e., an air-cooled ATF cooler is placed in front of the condenser of air conditioning system and a water-cooled one is embedded into the radiator header. However, the new system consists of only a water-cooled heat exchanger that has been changed into the integrated structure with an EGR cooler to have the engine coolant directly from the EGR cooler. The ATF cooler becomes the ATF warmer and cooler, i.e., it plays a role of an ATF warmer if the temperature of ATF is lower than that of coolant, and plays a role of an ATF cooler otherwise. Chassis dynamometer experiments demonstrated the fuel economy improvement of over 2.5% with rapid increase in the ATF temperature.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.92-99
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• 2013

High oil price and global warming problem are being continued all over the world. For this reason, fuel economy and emission of greenhouse gas are regulated by law in many countries. Therefore many companies are researching and producing hybrid electric vehicles (HEVs) which substitute conventional internal combustion engine vehicle. However, these researches and productions are restricted to mainly passenger cars. Because of cost and physical problems, commercial vehicles are difficult to evaluate fuel economy. So simulations are important and it is necessary to know how sensitive parameters that enter into simulation affect. In this paper, forward simulations using AVL Cruise were conducted for analysis of fuel economy for parallel hybrid bus and were repeated by changing each parameter. Based on these results, root mean square errors (RMSE) are calculated for analysis of fuel economy sensitivity. The number of target parameters are 15. These parameters were classified with high and low sensitivity parameter relatively.

• 대한기계학회논문집B
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• 제36권7호
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• pp.705-710
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• 2012

본 연구에서는, 차량용 에어컨 시스템으로 구성된 벤치 장비에서의 실험을 통하여 에어컨 관련 북미 실차 연비 평가 모드 중의 하나인 SC03 모드 연비 평가의 벤치 모사 시험 가능성을 검증하였다.본 연구에 사용된 설비는 차량용 에어컨 시스템을 실차 조건처럼 구성할 수 있는 각각의 챔버로 구분되어져 있으며, 외부 환경을 재연할 수 있도록 온도와 습도, 풍속을 제어할 수 있도록 구성하였다. 지금까지 실차 환경 풍동에서 평가 되어지던 SC03 모드 연비 평가에 대하여 시스템 벤치에서 모사가 가능하도록 실차에서 가장 중요한 변수인 차속과 차량 전면 풍속에 대응하는 압축기 회전수와 응축기 전면풍속에 대한 신뢰성을 확보하였다.이를 바탕으로 다양한 토출 용량을 가지는 압축기를 가지고 에어컨 시스템 벤치 장비에서 SC03 연비 모사 실험을 수행하여, 압축기 토출량의 차이에 따른 연비의 차이가 특징 지어지는 것을 확인하였다.

• 한국자동차공학회논문집
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• 제24권4호
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• pp.480-486
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• 2016

Manufacturers have been applying several technologies that can improve the fuel economy of their cars. The regulated voltage control(RVC) system, is one of those technologies being used in passenger cars. In RVC, the voltage of an alternator is controlled depending on the electrical load demand or battery SOC, although each manufacturer differs from another in terms of detail. RVC can reduce the load of an alternator by consuming the stored energy of a battery and simultaneously generate energy. In this paper, a diesel passenger car equipped with an RVC system was tested under FTP-75 and HWFET modes to evaluate fuel economy as their initial battery SOC(100, 90, 80 and 60 %). The test results showed that the initial SOC affects fuel economy only under the FTP-75 mode. FTP-75 fuel economy of the 60% SOC was 13.2 % lower than the 100 % SOC. Also, the simultaneous consumption of the two energy sources did not appear in 60 % SOC.

• 동력기계공학회지
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• 제20권4호
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• pp.52-62
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• 2016

Nowadays, emissions of a vehicle are been getting by testing on a chassis dynamometer and a test modes. Also, fuel efficiency is calculated by carbon-balance method that is applying the emissions(CO, THC and $CO_2$) to the fuel calculation formular. In Korea, before 2014, the formular did not include the fuel factors (density, net heat value and carbon weight fraction), but the constants were based on the fuel properties of 2000s. So, this formular did not consider a characteristic of test fuel property that was changed when progressing fuel efficiency test. The characteristics of test fuel property which was distributed in domestic have a difference of quality depending on production regions and oil-refining facilities. Because the fuel properties are variable value during refineries, crude oils and blending contents of a bio-fuel, vehicle fuel is changed for each test. Therefore, the fuel qualities need to apply for a fuel economy test. In this paper, changing patterns of a fuel properties were reviewed during history of fuel standards. Also, the appropriateness of the methods was discussed by calculating and comparing fuel economies with the fuel factors and the constants.

• International Journal of Automotive Technology
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• 제5권4호
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• pp.287-295
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• 2004

A performance simulator for the fuel cell hybrid electric vehicle (FCHEV) is developed to evaluate the potentials of hybridization for fuel cell electric vehicle. Dynamic models of FCHEV's electric powertrain components such as fuel cell stack, battery, traction motor, DC/DC converter, etc. are obtained by modular approach using MATLAB SIMULINK. In addition, a thermodynamic model of the fuel cell is introduced using bondgraph to investigate the temperature effect on the vehicle performance. It is found from the simulation results that the hybridization of fuel cell electric vehicle (FCEV) provides better hydrogen fuel economy especially in the city driving owing to the braking energy recuperation and relatively high efficiency operation of the fuel cell. It is also found from the thermodynamic simulation of the FCEV that the fuel economy and acceleration performance are affected by the temperature due to the relatively low efficiency and reduced output power of the fuel cell stack at low temperature.

• 한국자동차공학회논문집
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• 제14권1호
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• pp.138-143
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• 2006

Modification of injector, oil ring tension reduction and oil pump rotor re-matching with optimization of relevant engine control parameters could drive fuel consumption reduction of HSDI diesel engine. A 5 holes injector was replaced with a 6 holes with smaller nozzle hole diameter and 1.5 k factor, and evaluated in a view of fuel economy and emission trade-offs. With introducing smaller nozzle hole diameter injector, PM(Particulate Matter) was drastically decreased for low engine load and low engine rpm. Modification of oil pump and oil ring was to reduce mechanical friction and be proved to better fuel economy. Optimization of engine operating conditions was a great help for the low fuel consumption. Influence of the engine operating parameters· including pilot quantity, pilot interval, air mass and main injection timing on fuel economy, smoke and NOx has been evaluated with 14 points extracted from NEDC(New European Driving Cycle) cycle. The fuel consumption was proved to $7\%$ improvement on an engine bench and $3.7\%$ with a vehicle.

• 대한전자공학회논문지TE
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• 제39권1호
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• pp.71-76
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• 2002

차량의 폭발적 증가로 인해 저속, 서행형태로 주행시간이 점점 늘어나므로, 본 연구에서는 연비향상을 목적으로 정차상태에서는 일부 실린더만으로 일정한 엔진회전수를 유지하고, 주행상태에서는 전 실린더를 이용하는 가변실린더에 대해 실제 하드웨어로 제작하여 실험해 보았다. 과거에 일부 제작되었던 가변실린더 엔진은 정차상태나 저속상태에서 사용하는 실린더 주위에 열이 집중하여 열응력이 발생하고, 사용하지 않는 실린더는 냉각수의 순환으로 인해 주변의 온도가 더욱 떨어지게 되어, 재점화시에 많은 유해가스가 배출되고 연료 소모량도 많아지게 되며, 엔진회전수가 고르지 못하는 문제가 있었다. 이러한 문제점을 극복하고자 정지상태나 저속주행상태에서와 같이 많은 출력을 요하지 않는 운행조건에서는 새로운 점화방식과 밸브 개폐시기를 이용하여 연비를 향상시키는 방안을 제시하고, 그 타당성을 검증하였다.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.1-7
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• 2013

This paper focuses on cooling fan control by using a magnetic clutch type for the improvement of fuel economy on a heavy city bus. In general, Heavy duty vehicles use viscous clutch type cooling fan which has some disadvantages, such as slow response, wide temperature variation of engine coolant water. But a magnetic clutch type cooling fan can be controlled electronically so the engine coolant temperature can be precisely controllable and this effects could be used to reduce fuel consumption. A control system for applying the magnetic clutch type cooling fan was developed in this study and applied to the real field test and chassis dynamometer test. The result showed well controlled coolant temperature and enhancement of fuel economy.

• 한국추진공학회지
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• 제19권2호
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• pp.81-87
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• 2015

디젤 엔진에서 저압 배기재순환 시스템의 적용을 통한 질소산화물 저감과 연비 향상에 관한 효과를 확인하였다. 엔진의 정상 상태 및 과도 상태에서 시험이 진행되었으며, 차량상사를 통한 NEDC 모드 테스트를 위하여 별도의 제어로직도 개발되었다. 정상 상태의 시험결과에서 저압 배기재순환 시스템은 고압 배기재순환 시스템에 비하여 질소산화물 저감 및 연비 향상에 유리함을 확인하였고, NEDC 모드 테스트 결과로부터 배출가스의 증가없이 연비를 향상시킬 수 있는 것으로 나타났다.