• 대한금속재료학회지
• /
• 제49권9호
• /
• pp.678-685
• /
• 2011

The aim of this study was to determine the effect of applied pressure and sintering temperature on the microstructure and mechanical properties for spark plasma sintering (SPS) from commercial pure titanium (CP-Ti) powders. Spark plasma sintering is a relatively new sintering technique in powder metallurgy which is capable of sintering metal and ceramic powers quickly to full density at a fairly low temperature due to its unique features. SPS of -200 mesh or -400 mesh CP-Ti powders was carried out in an $Ar+H_2$ mixed gas flowing atmosphere between $650^{\circ}C$ and $750^{\circ}C$ under 10 to 80 MPa pressure. When SPS was carried out at relatively low temperatures ($650^{\circ}C$ to $750^{\circ}C$), the high (>60 MPa) pressure had a marked effect on densification and grain growth suppression. The full density of titanium was achieved at temperatures and pressures above $700^{\circ}C$ and 60 MPa by spark plasma sintering. The crystalline phase and microstructure of titanium sintered up to $700^{\circ}C$ consisted of ${\alpha}$-Ti and equiaxed grains. Vickers hardness ranging from 293 to 362 Hv and strength ranging from 304 to 410 MPa were achieved for spark plasma sintered titanium.

• 한국자동차공학회논문집
• /
• 제16권1호
• /
• pp.45-51
• /
• 2008

This paper presents theoretical and experimental analysis on the characteristics of the power spectrum of electormagnetic waves radiating from the spark plug and their cables of a distributorless ignition system. The theoretical study was conducted applying the microwave transmission line theory and the antenna theory. The experimental works were carried out to measure the standing wave ratio(SWR) and the radiation power spectrum of this system. As a result, it has been found that a spark plug and its cable is working as a monopole antenna radiating elelctromagnetic waves. Because of its similar structure to a monopole antenna, the envelope of radiation power spectrum distribution has a bell shape which can be obtained from a monopole antenna operating as a series resonant circuit. The frequency characteristics from the SWR measurements show a similar frequency characteristics of power spectrum of the system studied. Also, it has been found that the density of the power spectrum of the system fitting a long time used spark plug is higher than that of fitting a new spark plug.

• Journal of Advanced Marine Engineering and Technology
• /
• 제27권2호
• /
• pp.246-259
• /
• 2003

For predicting the performances of the four stroke cycle spark ignition engines. the gas behavior in the engine system has been analyzed. The calculations consist of two parts. the calculation of the gas behavior in the intake and exhaust systems which was described in the first paper, and the calculation of the variations of gas properties inside the engine cylinders. In this Paper the simulations for the in-cylinder processes were described for the MPI engine, naturally aspirated and turbocharged engines with a carburettor. With the combination of the calculations of the intake and exhaust systems and the calculation of the in-cylinder processes. the predictions of the engine Performances and the exhaust emission characteristics were carried out. And the result showed good agrements with the experimental results under wide range of operating conditions.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권6호
• /
• pp.128-139
• /
• 2000

Environmental concerns and shortage of petroleum have promoted considerable interest in the use of alternate fuels in stationary diesel engine. In this study, a heavy-duty, intercooler-turbocharged 6-cylinder stationary diesel engine was converted into stationary gas engine fueled with propane or natural gas for the cogeneration plants. One of the most important factors in the combustion features of a stationary gas engine is the fuel composition and operating parameters in terms of compression ratio, spark advance, and engine loads. Experiments with different fuel gas and load conditions were carried out with combustion pressure analysis and NOx measurement. Combustion analysis based on P-$\theta$ diagrams was also investigated by means of combustion duration and cycle variation. Compression ratio is 10.0 and ignition timing is set by using the gasoline setting as a base line and advanced toward BTDC. The results show that fuel composition and spark advance have dominant effects on combustion and NOx characteristics at operating conditions.

• Environmental Engineering Research
• /
• 제14권2호
• /
• pp.95-101
• /
• 2009

Natural gas is a promising alternative fuel of internal combustion engines. In this paper, the combustion and emission characteristics were investigated on a natural gas engine at two different fuel injection timings during the intake stroke. The results show that fuel injection timing affects combustion processes. The optimum spark timing (MBT) achieving the maximum indicated mean effective pressure (IMEP) is related to fuel injection timing and air fuel ratio. At MBT spark timing, late fuel injection timing delays ignition timing and prolongs combustion duration in most cases. But fuel injection timing has little effect on IMEP at fixed lambdas. The coefficient of variation (COV) of IMEP is dependent on air fuel ratio, throttle positions and fuel injection timings at MBT spark timing. The COV of IMEP increases with lambda in most cases. Late fuel injection timings can reduce the COV of IMEP at part loads. Moreover, engine-out CO and total hydrocarbon (THC) emissions can be reduced at late fuel injection timing.

• 한국자동차공학회논문집
• /
• 제9권2호
• /
• pp.75-83
• /
• 2001

This paper presents the evaluation of combustion characteristics of sing-hole plasma jet ignitions in comparison with conventional spark ignition for variable of swirl velocity. Plasma jet plugs are three types according to ejecting directions : center of chamber, positive and negative swirl flow direction. Experiments are carried out for equivalent ratio 1.0 of LPG-air mixture in a constant volume cylindrical vessel. Not only the flame propagation is photographed at intervals, but the pressure variation in the combustion chamber is also recorded throughout the entire combustion process. The results show that the plasma jet ignitions and spark ignition enhance the overall combustion rate by increasing the swirl velocity. The dependence of the combustion rate swirl velocity leade to the conclusion that the placma jet plug, which ejects plasma jet to the cwnter of combustion chamber is the most desirable ignitor than other plugs.

• 오토저널
• /
• 제10권6호
• /
• pp.39-47
• /
• 1988

A disk photo sensor system was constructed and installed on engine for the crank angle measurement. Statically measured TDC crank angle data were compared with those obtained from engine motoring. Two groups of cylinder pressure data were compared each other, one measured by pressure transducer mounted flush on the combustion chamber and the other obtained with the help of spark plug type adaptor. A simple analysis on the gas flow in the spark plug type pressure transducer displayed reasonably good agreement with those from engine motoring tests. In various firing tests, the IMERs obtained from the spark plug type pressure transducer turned out to be higher than those from the flush mounted one at low engine speed while those two were nearly the same at high engine speed. As the engine load decreased the relative difference in IMEP measurement between the two types tended to be enlarged.

• 한국자동차공학회논문집
• /
• 제2권5호
• /
• pp.30-40
• /
• 1994

The direct-injection stratified-charge engine has the advantages of higher thermal efficiency and less CO and $NO_x$ emission levels than conventional spark ignition engines. However, its actual utilization is prevented by high unburned hydrocarbon emission levels during light-load operations. In this paper, fundamental studies were carried out using a pancake type constant volume bomb. The effects of intensification of local premixing by tangential and radial fuel injection were examined experimentally. Unburned hydrocarbon emission levels with radial fuel injection were shown to be lower than those of tangential fuel injection cases. The stratification and mixing process of fuel jet and combustion process were observed by schlieren photography.

• 한국분말재료학회지
• /
• 제15권5호
• /
• pp.405-410
• /
• 2008

SOFC (Solid Oxide Fuel Cell) Ni-YSZ anode was fabricated by the spark plasma sintering (SPS) process and its microstructure and electrical properties were investigated in this study. The spark plasma sintering process was carried out at $800{\sim}1000^{\circ}C$ for holding time of 5 min under 40 MPa. To fabricate Ni-YSZ anode, the SPS processed specimens were reduced at $800^{\circ}C$ under $H_2$ atmosphere. The reduced specimens showed relative density of $48.4{\sim}64.8%$ according to sintering temperature. And also, the electrical conductivity of reduced specimens after sintering at 900 and $1000^{\circ}C$ showed $480{\sim}600$ (S/cm) values at the measuring range of $600{\sim}900^{\circ}C$.

• 한국자동차공학회논문집
• /
• 제22권4호
• /
• pp.98-104
• /
• 2014

The technologies employing spray-guided type combustion system for ultra-lean combustion direct injection engine is focused as a promising technology for satisfying emission regulations and improving fuel economy. In the present study, control and design optimization of lean-burn LPG direct injection engine was carried out with control strategy and injection position changes. Inter-injection spark ignition strategy was applied and the effect of the strategy was assessed at relatively higher load operation condition than previous researches. In order to create richer mixture in the vicinity of spark plug electrode, relative distance between the dead-end of injector and the electrode of spark plug was changed.