• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.6
• /
• pp.60-65
• /
• 2004

Numerical simulations and experiments have been carried out to investigate the effect of fuel injection nozzles on the combustion and NOx formation processes in a medium-speed marine diesel engine. Spray visualization experiment was performed in the constant-volume high-pressure chamber to verify the numerical results on the spray characteristics such as spray angle and spray tip penetration. Time-resolved spray behaviors were captured by high-speed digital camera and analyzed to extract the information on the spray parameters. Spray and combustion phenomena were examined numerically using FIRE code. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Numerical results were verified with experimental data such as cylinder pressure, heat release rate and NOx emission. Finally, the effects of fuel injection nozzles on the engine performance were investigated numerically to find the optimum nozzle parameters such as fuel injection angle, nozzle hole diameter and number of nozzle holes. From this study, the optimum fuel injection nozzle (nozzle hole diameter, 0.32 mm, number of nozzle holes, 8 and fuel injection angle, $148^{\circ}$) was selected to reduce both the fuel consumption and NOx emission. The reason for this selection could be explained from the highest fuel-air mixing in the early phase of injection due to the longest spray tip penetration and the highest heat release rate after $19^{\circ}$ ATDC due to the increased injection duration.

• Journal of Acupuncture Research
• /
• v.24 no.2
• /
• pp.155-167
• /
• 2007

Objectives : This study was performed to evaluate the general distribution and the efficacy of oriental medical treatment for low back pain. Methods: We have selected of the moxa bucket moxibustion. We make a comparative study of the thermodynamic characteristics of moxa bucket moxibustion. We examined combustion times, temperatures, temperature gradients in each period during a combustion of moxa bucket moxibustion made by oak wood. Results : The 80 cases of low back pain patients was analyzed according to the distribution of sex, age, the period of disease, contributing factor, the patient-condition on admission, the symptom on admission, the duration of admission, the reading of the X-ray and the treatment efficacy was evaluated respectively. 1. Female was more than male in the ratio of 1:1.2, and thirties and seventies 25% the most, the acutest phase 46.3% the most, reason unknown 33.8% the most, Grade III 50% the most, L.B.P. only 51.3% the most, the day of 6-10 30% the most, compression Fx 30% the most. 2. In the total treatment result, the good was 51.3%, the excellent 22.5%, the fair 17.5%, the poor 8.8% in order. About 'the effective rate'(the percentage of positive effective treatment cases) of each distribution, the fifties 100% the most, the acutest phase 97.3% the most, the slip down, weight lifting, overuse 100% the most respectively, Grade III 97.5% the most, L.B.P. only 95.1% the most, the day of 11-15 100% the most, HN.P. 93.3% the most. Conclusions : We have known the efficacy of oriental medical treatment for L.B.P. was good and early treatment was better than late treatment and main cause of L.B.P. was degenerative change.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.9
• /
• pp.789-795
• /
• 2016

Laser-induced combustions and explosions generated by high laser irradiances were explored by Laser-Induced Breakdown Spectroscopy (LIBS). The laser used for target ablation is a Q-switched Nd:YAG laser with 7 ns pulse duration at wavelength of 1064 nm laser energies from 40 mJ to 2500 mJ ($6.88{\times}10^{10}-6.53{\times}10^{11}W/cm^2$). The plasma light source from aluminum detected by the echelle grating spectrometer and coupled to the gated ICCD(a resolution (${\lambda}/{\Delta}{\lambda}$) of 5000). This spectroscopic study has been investigated for obtaining both the atomic/molecular signals of aluminum-oxygen and the calculated ambient condition such as plasma temperature and electron density. The essence of the paper is observing specific electron density ratio which can support the processes of chemical reaction and combustion between ablated aluminum plume and oxygen from air by inducing high laser energy.

• Journal of the Korean Institute of Gas
• /
• v.19 no.6
• /
• pp.28-33
• /
• 2015

In this study, a dual fuel engine fueled with natural gas and diesel was tested to investigate the effects of heating value variation of CNG fuel. CNG substitution rate which is defined as the ratio of CNG and diesel supplied in a heating value basis was fixed at 80%. The higher heating value was varied from $10,400kcal/Nm^3$ to $9,400kcal/Nm^3$ by mixing nitrogen gas with pure CNG and diesel fuel was injected at a fixed injection timing. The engine test results showed that thermal efficiency and power output were decreased as the heating value of mixed CNG fuel was decreased. And the peak cylinder pressure was also decreased but the ignition delay time and the combustion duration and timing were almost same.

• Korean Journal of Acupuncture
• /
• v.27 no.4
• /
• pp.35-47
• /
• 2010

Objectives : To characterize the thermal properties of traditional warm needle and new warm needle with various air flows as an important environmental factor and to suggest the necessity of maintaining suitable environment of clinics to maximize their efficacy. Methods : We measured the temperature characteristics of traditional moxa warm needle and new moxa charcoal warm needle by applying an automatic temperature acquisition system with thermocouples while external various air flows were supplied. Temperatures of two positions at the needle body were measured while a moxa cone burned. Typical temperature characteristics like peak temperature, duration, curve shape and the efficiency of the heat stimuli by heat amount analysis were executed. Results : Both warm needles showed similar temperature curve with an increase in the air flow. Peak temperature and duration of effective heat decreased with the air flow, as shown in indirect moxibustion on garlic. The temperature change pattern by the air flow became more apparent when the total combustion heat was compared with the effective heat. The values from two positions on the needle body were significantly different, showing a distance dependency from the heat source of warm needle acupuncture. Conclusions : Thermal properties of warm needle acupuncture was observed variously with surrounding air flow of 0.0 - 0.7 m/s. It emphasized the importance of environmental control as well as the warm needle itself such as heat source and needle. The latter has already been known to deliver designated heat to subjects. It also indicated the importance of education and skill of the practitioners of warm needle acupuncture.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.3
• /
• pp.270-275
• /
• 2016

The characteristics of the fuel quantity, injection rate and macro spray development was investigated under a range of diesel fuel temperatures. The actual injection quantity decreased despite the same signal of the injection start and injection duration as the fuel temperature decreased. The injection rate measurements confirmed that the actual injection commencement was delayed and the actual injection duration was shortened under lower fuel temperature conditions, which explains why the injection quantity decreased. Spray tip penetration with a lower fuel temperature was longer than that with a higher fuel temperature due to the deteriorated atomization. As a pre-test for the combustion experiment under low temperature conditions, piston targeting with pilot injection was accomplished, which showed that the fuel droplet from pilot injection was introduced into the crevice area. This suggests that the pilot injection quantity and timing should be chosen with careful consideration for actual applications.

• The Journal of Korean Medicine
• /
• v.29 no.3
• /
• pp.11-20
• /
• 2008

Objectives: Warm-needling is a method combining the effects of acupuncture with the effects of moxibustion. We need to standardize the characteristics of warm-needling in order to achieve consistency in its operational mechanisms and effects, which will improve clinical ability in the field of Eastern medicine. Methods: In this study, using the LabVIEW system on the warm-needling technique, we measured and compared partial temperature changes which varied according to the density of the moxa cone and the moxa cone's core peak temperature. Results& Conclusions: Examination of the warm-needle's partial temperature in relation to the cone density of the 0.8g moxa specimen suggests that a lower density of the moxa cone corresponds to a higher peak temperature and but with a shorter duration. During the effective stimulus time, the lower the density of the moxa cone, the shorter the duration of the effective stimulus time and the higher the mean temperature. Conversely, the higher the density of the moxa cone, the longer the effective stimulus time and lower the mean temperature.

• Journal of the Korean Society of Safety
• /
• v.29 no.3
• /
• pp.114-120
• /
• 2014

The purpose of this study is to conduct the study of the combustion and thermal characteristics through transportation oil for the analysis of fire hazard. Transportation oil breaks down into fuels such as diesel for civilian demands, gasoline, DF1(diesel for military), high sulfur diesel(for marine), kerosene and JP1(for aviation), and lubricants like brake fluid, power steering oil, engine oil, and automatic and manual transmission oil. The experiments of flash point, ignition point, flame duration time, heat release rate were carried out using TAG closed cup flash point tester(AFP761), Cleveland open cup auto flash point analyzer(AFP762), KRS-RG-9000 and Dual cone calorimeter. As a result, the fuel's ignition points were lower than lubricants, especially that of gasoline was not conducted as it has below zero one. Gasoline has the highest ignition point of about $600^{\circ}C$, while the other fuels showed $400{\sim}465^{\circ}C$. For flame duration time, lubricants had over 300 seconds, but fuels had less than 300 seconds except high sulfur diesel(350 seconds). Total heat release rate ranged $287{\sim}462kW/m^2$ for lubricants and gasoline showed the highest total heat release rate, $652kW/m^2$.

• Journal of the Korean Society of Safety
• /
• v.26 no.5
• /
• pp.118-129
• /
• 2011

In this study, species resistant to forest fire were extracted from high trees through an investigation of combustion mechanism. Here, the average flameless ignition temperatures of living leaves, branches and barks of oak were respectively, $365^{\circ}C$, $440^{\circ}C$ and $435^{\circ}C$, and the average flameless ignition temperatures of living leaves, branches, barks and cones of pine tree were respectively, $320^{\circ}C$, $405^{\circ}C$, $435^{\circ}C$ and $363^{\circ}C$. It shows that generally, pine tree has a lower flameless ignition temperature than oak and thus, has a relatively high risk of flameless ignition. When comparing risk of fire depending on ignition characteristics, Quercus serrata had a low risk of stem fire, and Quercus acutissima and Quercus serrata had a low risk of crown fire, as well. When analysing risk of fire depending on a duration of flame, also, Quercus dentata had a low risk of stem fire, and Quercus variabilis Blume had a low risk of crown fire too. Lastly, when comparing risk of fire, according to heat release rates, Quercus acutissima had a low risk of stem fire, and Quercus acutissima and Quercus dentata had a low risk of crown fire, as well. In conclusion, it was observed that as fire-resistant species, Quercus serrata and Quercus dentata have a low risk of ignition, Quercus variabilis Blume has a short duration of flame after discharging ignition when a forest fire occurs, and Quercus acutissima, Pinus Rigida and Antipathes japonica Brook have low heat release rates.

• Journal of Hydrogen and New Energy
• /
• v.24 no.3
• /
• pp.242-248
• /
• 2013

The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched LPG fuel in LPG engine and is to clarify the effects of hydrogen enrichment in LPG fuelled engine on exhaust emission and performance. An experimental study was carried out to obtain fundamental data for performance and emission characteristics of hydrogen enrichment in LPG engine. The research was held by changing the hydrogen ratio to 0, 5, 10, 20% in 1500rpm, bmep 2 and 4bar. The result turned out that the combustion duration was shortened due to fast flame propagation of hydrogen. And the amount of Carbon dioxide and Hydrocarbon decreased. However, the amount of NOX increased, which is thought to be the result of high adiabatic flame temperature of hydrogen. It has been confirmed that this phenomenon has changed by the Hydrogen mixing ratio.