• 대한기계학회논문집B
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• 제30권5호
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• pp.465-471
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• 2006

Controlled auto-ignition(CAI) combustion, offers the potential to improve fuel economy and reduce emission simultaneously. In this study, CAI-combustion was achieved in a single cylinder gasoline DI engine with modified camshafts in order to restrict the gas exchange process. We investigated the effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region. The effect of injection timings on combustion characteristic such as start of combustion, combustion duration and heat release rate was also investigated. From the result early injection causes the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gives rise to good mixing of the fuel/air. On the other hand, late injection extended the operation region more than early injection but the emissions of HC and NOx were more or less increased than early injection.

• 한국분무공학회지
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• 제13권1호
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• pp.1-8
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• 2008

It was investigated how fuel injection timing - early injection and later injection - in conjunction with throttle open rate effect the fuel-air mixing characteristics, Engine power, combustion stability and emission characteristics on a DI CNG spark Engine and control system that had been modified and designed according to the author's original idea. It was verified that the combustion characteristics were changed according to fuel injection timings and Engine conditions determined by different throttle open rates and rpm. It was found that the combustion characteristics greatly improved at the complete open throttle rate with an early injection timing and at the part throttle rate with a late injection timing. Combustion duration was governed by flame propagation duration in a late injection timing and by an early flame development duration in an early injection timing. As the result, we discovered that combustion duration is shortened, lean limit is improved, air-fuel mixing conditions controlled, and emissions reduced through control of fuel injection timing according to change of the throttle open rate.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.26-31
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• 2006

An experimental investigation of an early injection strategy was conducted on a small single cylinder common-rail DI diesel engine to reduce the oxides of nitrogen($NO_x$) emission. The main objectives of this study were to investigate the emissions, performance and combustion characteristics in a diesel engine with early and two-stage injections. The two- stage injection was conducted to reduce the wall-wetting of early injected fuels on the cylinder wall or to promote the ignition of premixed charge. The engine test was performed at conditions of 1500rpm, injection timing ranging from TDC to BTDC $80^{\circ}$. The experimental results show that $NO_x$ emissions were decreased in both cases of early injection and two stage injection compared to the conventional diesel combustion by the near TDC injection. However, soot and products of incomplete products (i.e. HC and CO) are slightly increased. Also, the second injection near TDC promoted the ignition of premixed fuel, therefore, IMEP was increased.

• 대한기계학회논문집B
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• 제30권5호
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• pp.457-464
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• 2006

Controlled auto ignition (CAI) combustion, also known as HCCI (homogeneous charge compression ignition), offers the potential to simultaneously improve fuel economy and reduce emission. CAI-combustion was achieved in a single cylinder gasoline DI engine, with a cylinder running in a CAI mode. Standard components were used the camshafts which had been modified in order to restrict the gas exchange process. The effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region were investigated. The effect that injection timings on factor such as start of combustion, combustion duration and heat release rate was also investigated. From results early injection caused the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gave rise to good mixing of the fuel-air.

• Journal of Advanced Marine Engineering and Technology
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• 제32권7호
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• pp.1013-1018
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• 2008

For a sequential port fuel injection natural gas engine, its combustion and emission characteristics at low loads are crucial to meet light duty vehicle emission regulations. Fuel injection timing is an important parameter related to the mixture formation in the cylinder. Its effect on the combustion and emission characteristics of a natural gas engine were investigated at 0.2 MPa brake mean effective pressure (BMEP)/2000 rpm and 0.26 MPa BMEP/1500 rpm. The results show that early fuel injection timing is beneficial to the reduction of the coefficient of variation (COV) of indicated mean effective pressure (IMEP) under lean burn conditions and to extending the lean burn limits at the given loads. When relative air/fuel ratio is over 1.3, fuel injection timing has a relatively large effect on engine.out emissions. The levels of NOx emissions are more sensitive to the fuel injection timing at 0.26 MPa BMEP/1500 rpm. An early fuel injection timing under lean burn conditions can be used to control engine out NOx emissions.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.20-25
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• 2006

Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and injection angle affects the mixture formations. Thus the purpose of this study was to investigate relationship of combustion and mixture formations according to injection timing and injection angle in a common rail direct injection type HCCI engine using a early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel. injection timing and injection angle affect the mixture formations and in turn affects combustion in the PCCI engine.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.9-18
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• 2005

The objective of this study is to analyse the spray characteristics according to the injection duration under the ambient pressure condition, and the injection timing in the visualization engine. In order to investigate the spray behavior, we obtained the spray velocity using the PIV method that has been an useful optical diagnostics technology, and calculated the vorticity from spray velocity component. These results elucidated the relationship between vorticity and entropy which play an important role in the diffusion process for the early injection case and the stratification process for the late injection case. In addition, we quantified the homogeneous diffusion rate of spray using the entropy analysis based on the Boltzmann's statistical thermodynamics. Using these method, it was found that the concentration of spray droplets caused by the increase of injection duration is more effective than the increase of momentum dissipation. We also found that the homogeneous diffusion rate increased as the injection timing moved to the early intake stroke process and BTDC $50^{\circ}$ was the most efficient injection timing for the stratified mixture formation during the compression stroke.

• 대한족부족관절학회지
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• 제15권1호
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• pp.27-31
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• 2011

Purpose: This study evaluated the efficacy of an intra-articular injection of sodium hyaluronate in the treatment of early stage osteoarthritis of the ankle. Materials and Methods: Early stage ankle osteoarthritis (Takakura stage I and II) patients who received hyaluronic acid injection therapy were retrospectively reviewed. Patients underwent intra-articular injections of 2 mL of sodium hyaluronate for 3 consecutive weeks. Clinical evaluation and Visual Analogue Scale (VAS) scoring were performed at every three months after treatment. Results: Total 27 patients were involved and mean age was 55 year old (range 33 to 77 years). There were 13 male and 14 female patients. Mean follow up duration was 13 month and. Pre-intra-articular VAS score was $8.9{\pm}0.7$ and three month follow up score was $3.8{\pm}2.8$. VAS score of last follow up was $3.2{\pm}3.4$. The effect of hyaluronic acid continued about one year when analyzed the VAS score change of the patients followed for more than one year. Patients' satisfaction was "very satisfied" in nine, "satisfied" in 12, "fair" in one, and "not satisfied" in five patients. Overall satisfaction rate was 82%. There were no ankle osteoarthritis stage changes in serial follow up radiograph. Conclusion: Symptomatic relief of signs and symptoms of osteoarthritis of the ankle was achieved by injection of an intra-articular hyaluronate injection. Efficacy of Hyaluronate acid injection persisted more than 1 year in our study. Intra-articular hyaluronate injection to ankle osteoarthritis is safe and effective as knee joint and should be considered as a valid conservative treatment for ankle osteoarthritis.

• 한국수정란이식학회지
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• 제9권2호
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• pp.167-172
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• 1994

This experiment was arried out to investigate the development of ea4y rabbit embryos in vivo. Twenty-six New Zealand White does were superovulated by treatment with PMSG(Intervet Co; I. M single injection, 150. U./rabbit) followed 3 day later by simultaneous I.V injection of 100 I.U HCG (Intervet Co, )and natural service with fertile male. All of does was killed at the specific times (24, 27, 30, 36, 42, 50 and 93 h post-hCG) to find out the early embryonic development in vivo respectively. Embryos at the specified stages of development were obtained at the following times after injection of hCG; one-ceH at 24 h, two-cell at 24~27h, four-cell at 27~36 h, morulae at 50 h and early blasto-cyst at 93 h and expanded or hatching blastocyst at 144 h. Number of embryos recovered per rabbit superovulated was 26.1 and average of recovery rate was 83.7%. The results suggest that superovulation was efficient for the increase of embryo number in rabbits, and as shown in results, asynchronous cleavage was prevalent among the recovered embryos.

• 한국분무공학회지
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• 제27권2호
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• pp.101-108
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• 2022

Performance and emissions with different diesel injection methods were analyzed in a natural gas-diesel, dual-fuel engine under low-load conditions. Natural gas was supplied to intake port during the intake stoke to form a natural gas-air premixed mixture for all methods. Diesel was injected directly into the cylinder during the compression stroke in three ways: early injections, late injections, and a combination of early and late injections. The early injections had the highest thermal efficiency among the three methods owing to its highest combustion efficiency. The wide dispersion of diesel before the combustion initiation also allowed superior emissions characteristics.