• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.491-496
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• 2008

New concept ramjet propulsion system with liquid bipropellant rocket using "Green Propellant" hydrogen peroxide for launch stage is proposed. In this novel concept, hydrogen peroxide gas generator produces hot oxygen at launch stage and kerosene injects to this jet in combustor. For basic study of this new concept ramjet system, investigation of auto-ignition characteristics and combustion of decomposed hydrogen peroxide and kerosene was conducted. In various test cases, auto-ignition and stable combustion was verified. The combustion temperature of 400°C and Fuel/Oxidizer mixture ratio of 0.6 were the limit of auto ignition. Through the experiment results, the possibility of novel concept combined propulsion system using hydrogen peroxide gas generator is ascertained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1681-1690
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• 1998

The aim of this paper is to investigate combustion characteristics of lean premixed mixture stabilized by catalytic surface reaction. The catalytic combustor consisted of a catalyst bed and a thermal combustor. The catalyst bed was made of two stage, Pd catalyst in the first stage and Pt catalyst in the second stage. Auto ignition of lean mixture took place in the thermal combustor. Ignition temperature was about $810{\sim}820^{\circ}C$ at the fuel-air ratio of 1.5~3.0 % and the mixture velocity of 11~18m/sec. The position of flame front in the thermal combustor moved toward back as preheat temperature increased and fuel-air ratio decreased. The f1ame supported by surface reaction was stabilized without any flame stabilizers. NOx emissions from the catalytic combustor were below 2.0 ppm ($O_2$ 15 %) when gas temperature was limited below $1350^{\circ}C$. This result demonstrates that NOx emission from the catalytic combustor is much low comparing with conventional combustors.

• Journal of Power System Engineering
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• v.13 no.2
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• pp.5-10
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• 2009

In recently, studies concerned to the diesel engine uses a natural gas as a fuel oil whose infra has been built already was approached to PCCI or HCCI with keeping a high thermal efficiency and reducing NOx and PM have been researching actively in normally single cylinder. An ignition source is required to bum the natural gas by a spark plug in gasoline engines, due to a higher auto-ignition temperature of natural gas. Then gas oil and DME were introduced as the ignition source. In this study as basic data for practical use of natural gas PCCI and HCCI engines, combustion characteristics and emission characteristics on 4-cylinders natural gas PCCI and HCCI engines with gas oil and DME as ignition sources were analyzed and the engine load range that is main object for practical use of PCCI and HCCI engines was made clearly by empirical experiment.

• Journal of the korean Society of Automotive Engineers
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• v.25 no.5
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• pp.34-36
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• 2003

• Journal of Energy Engineering
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• v.16 no.3
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• pp.113-119
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• 2007

The auto-ignition characteristics and combustion behaviors of one-dimensional array of water-in-fuel droplets suspended in a high temperature chamber have been investigated experimentally with various droplet spacing and number of droplets. The fuels used were pure n-decane and emulsified n-decane with water contents varied from 10% to 30%. All experiments have been performed at 920 K under the atmospheric pressure. The number of droplets in an array were fixed as 3 or 5 and its spacing was varied from 3 mm to 7 mm by 1mm interval. The imaging technique with a high-speed camera has been adopted to measure the ignition delay and flame life time. The micro-explosion behaviors were also observed. As the droplet array sparing increased, the ignition delay also increased regardless of water contents. However, the life time of droplet array decreased as the droplet spacing increased. The full combustion time in array of 3 droplets was found to be longer than that for 5 droplets case due to the longer ignition delay.

• Journal of the Korean Society of Safety
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• v.25 no.1
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• pp.17-21
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• 2010

The chemistry and ignition delay of hydrogen/air/HFP premixed mixtures was investigated numerically with unsteady perfectly stirred reactor(PSR). The detailed chemistry of 93 species and 817 reaction mechanism was introduced for hydrogen/air/HFP mixtures. The results shows the temporal concentration variations of major or reactants such as hydrogen and oxygen during autoignition were similar to the spatial distribution of premixed flame while water vapor produced at the ignition temperature was decomposed later, which can be clarified with the relate species production rates that the the re-growth (or shoulder) of OH concentration is a result of F radicals attacking $H_20$ forming OH and HF. For the stoichiometric $H_2$/air mixture inhibited by 20% HFP, HFP thermal decomposition reaction prevails over the radical attack such as H at initial stage. Even though relatively large HFP addition contributes to delay the ignition, chemical effect on the ignition delay is not effective because of late thermal decomposition of HFP. The most small ignition delay was observed at a slightly fuel lean condition ($\phi$ = 0.9), and temperature dependency of ignition delay was clearly shown near 900 K.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.83-90
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• 2004

A flywheel-driven rapid compression and expansion machine is developed and utilized for experimental study of homogeneous charge compression ignition combustion. Compression ignition of homogeneous charge in IC engines offers possibilities of realizing ultra-lean engine operation with greatly reduced NOx and particulate formation. Fundamental investigations are carried out in order to better understand this ideal engine combustion mechanism. Perfectly premixed propane-air mixtures of various equivalence ratio are compression-ignited in the rapid compression and expansion machine, and the characteristics of the auto-ignition and the following combustion process are analyzed.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.57-64
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• 1991

Spart-ignition engine knock is an abnormal combustion phenomenon originated from auto- ignition of a portion of or the entire end-gas during the later stage of combustion process. And engine knock is accompanied by a vibration of engine cylinder block and a high-pitched metallic noise. Engine knock is characterized in terms of its intensity, its occurrence crank angel and the percentage of engine knock cycles. To characterize engine knock, a precise measurements of cylinder pressure and a statistical analysis of cylinder pressure data are needed. The purpose of this study is to develope a technique to measure engine knock and its characteristics as a function of ignition timing change. A 4-cylinder spark-ignition engine and unleaded gasoline, whose octane number was 94, were used for experiments. To measure engine knock and to analyze engine knock characteristics, cylinder pressure data were sampled by a high speed data acquisition system which was developed in this study. Cylinder pressure data were sampled at each 0.1.deg. crank angle and the number of cycles continuously sampled was 80.

• Journal of ILASS-Korea
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• v.16 no.4
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• pp.167-175
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• 2011

The HCCI engines have been known with high efficiency and low pollution and can be actualized as the new internal combustion engines. However, As for(??) the ignition and combustion depend strongly on the oxidation reaction of the fuel, so it is difficult to control auto-ignition timing and combustion duration. Purpose of this paper is creating the database for development of multi-dimensional simulation and investigating the influence of different molecular structure. In this research, the effect of n-heptane mole ratio in fuel (XnH) on the ignition delay from homogeneous charge compression ignition(HCCI) has been investigated experimentally. By varying the XnH, it was possible to ascertain whether or not XnH is the main resource of ignition delay. Additionally, the information on equivalence ratio for varying XnH was obtained. The tests were performed on a RCM (Rapid Compression Machine) fueled with n-heptane and iso-octane. The results showed that decreasing XnH (100, 30, 20, 10,0), the ignition delays of low temperature reaction (tL) and high temperature reaction (tH) is longer. And the temperature of reaction increases by about 30K. n-heptane partial equivalence ratio (fnH) affect on tL.and TL. When ${\phi}$nH was increased as a certain value, tL was decreased and TL was increased.