• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.5
• /
• pp.449-456
• /
• 2010

The HCCI engine is a prospective internal combustion engine with which high diesel-like efficiencies and very low NOx and particulate emissions can be achieved. However, several technical issues must be resolved before HCCI engines can be used for different applications. One of the issues concerning the HCCI engine is that the operating range of this engine is limited by the rapid pressure rise caused by the release of excessive heat. This heat release is because of the self-accelerated combustion reaction occurring in the engine and the resulting engine knock in the high-load region. The purpose of this study is to evaluate the role of thermal stratification and fuel stratification in reducing the pressure rise rate in an HCCI engine. The concentrations of NOx and CO in the exhaust gas are also evaluated to confirm combustion completeness and NOx emission. The computation is carried out with the help of a multizone code, by using the information on the detailed chemical kinetics and the effect of thermal and fuel stratification on the onset of ignition and rate of combustion. The engine is fueled with dimethyl ether (DME), which allows heat release to occur in two stages, as opposed to methane, which allows for heat release in a single stage.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.1
• /
• pp.42-49
• /
• 2010

Increasing environmental concerns regarding the use of fossil fuels and global wanning have prompted researcher to investigate alternative fuels. The purpose of this study is to investigate the syngas production by biogas reforming using a compression spark ignition engine. The parametric screening studies were carried out according to the variations of oxygen enrichment rate, biogas $CO_2$ ratio, intake gas temperature, and engine revolution. When the oxygen enrichment rate and input gas temperature increased, hydrogen and carbon monoxide were increased. But the biogas $CO_2$ ratio and engine revolution increased, the syngas were reduced. For the reforming of methane 100% only, generation of hydrogen and carbon monoxide was 58% and 17%, respectively. However when the biogas $CO_2$ ratio was 40%, hydrogen and carbon monoxide concentration were about 20% each.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.1
• /
• pp.9-16
• /
• 2020

A performance evaluation of the 200 N-class GCH₄/LOx small rocket engine was performed through ground hot-firing test. As a result, the combustion pressure and thrust raised with the increase of the oxidizer supply pressure, and thus the specific impulse, characteristic velocity, and their efficiency increased. The characteristic velocity was measured at about 90% performance efficiency. The change of chamber aspect ratio did not affect the performance of the rocket engine in the test condition specified. In addition, uncertainty evaluation was conducted to ensure the reliability of the test results.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.85-92
• /
• 2020

Ground hot-firing tests were conducted to analyze the combustion performance according to the characteristic lengths 1.37 m, 1.71 m, and 2.06 m of the combustion chamber in 200 N-class GCH4-LOx small rocket engine. Thrust, specific impulse, and characteristic velocity at the steady-state could be obtained as the key performance parameters of the rocket engine. The performance characteristics acquired through the test were compared and analyzed with the theoretical performance calculated from CEA analysis. Observation of the influence of characteristic length on the combustion performance indicates that an optimal characteristic length shall remain between 1.71 m and 2.06 m.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.8
• /
• pp.733-741
• /
• 2013

This is the first paper on the combustion characteristics of landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine, and it discusses the fundamental characteristics of fuel from the viewpoint of thermochemistry and thermodynamics and compares these results with experimental ones. The results show that the final pressures obtained from theoretical analysis vary under the same heating value owing to the change in the constant volume specific heat owing to the difference in the burned gas composition according to the fuel gas compositions; furthermore, the stoichiometric ratios and trends of analytical and experimental pressures coincide very well, although some minor differences are observed between the two. The root cause of the difference is the heat transfer, which changes the specific heat and lowers the temperature considerably, in the real combustion process. In addition, the large chamber volume and ignition position promote the heat transfer to the wall. Finally, the fuel conversion efficiency increases as the methane mol fraction decreases, and it is maximum when the stoichiometric ratio ranges from 0.8 to 0.9. These increases due to the composition and stoichiometric ratio could sufficiently compensate the decrease due to the specific heat ratio drop, LFG might be more advantageous than pure methane in a real engine.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.6
• /
• pp.45-52
• /
• 2021

A hot-firing test was conducted using gaseous-methane and gaseous-oxygen under highly fuel-rich condition as a prior study for the development of a liquid propellant small rocket engine. To compare combustion characteristics for various equivalence ratios, the oxygen flow rate was set to 12 g/s and the methane flow rate was changed according to the equivalence ratio. As a result, it was observed that the steady-state characteristic velocity obtained during the hot-firing test steeply rose in the latter part of each test: the difference between the former and the latter steady value was enhanced overall in proportion to the equivalence ratio. Based on this, the equivalence ratio range depending on the variational characteristics of the characteristic velocity could be divided into three combustion regimes.

• 한국연소학회:학술대회논문집
• /
• 2014.11a
• /
• pp.153-156
• /
• 2014

This study was aimed to assess combustion stability for coaxial swirl injector and FOOF impinging injector which would be candidates in liquid rocket engine combustors. Simulating combustion tests under atmospheric condition have been conducted by gaseous oxygen and the mixture of methane and propane, using two actual injectors. By analyzing the measured dynamic pressure signals, we have evaluated the combustion stability margin of both injectors by drawing a stability map.

• 한국연소학회:학술대회논문집
• /
• 2014.11a
• /
• pp.141-142
• /
• 2014

This numerical study was carried out to optimize dual fuel combustion on natural gas-diesel in static chamber. Spray experiments conducted under conditions of premixed methan 0%, 5% and 10%. In the results, penetration decreases when premixed methane is increasing. Constants of numerical models were acquired from results of spray experiments to enhance accuracy of numerical study. And dual fuel engine simulation was implemented by using AVL-FIRE with acquired constants.

• Journal of Mechanical Science and Technology
• /
• v.14 no.6
• /
• pp.699-703
• /
• 2000

Experiments were carried out to investigate the characteristics of the hydrocarbon (HC) emissions and to reduce cold start hydrocarbons in gasoline engines. An HC adsorber was, used and it coated was by Pd/Rh catalyst with zeolite on a honeycomb monolith. The HCs were efficiently trapped at temperatures below $100^{\circ}C by physical adsorption. After adsorption, they were reduced gradually by the catalytic oxidation of Pd/Rh catalysts as the adsorber temperature increased above $100^{\circ}C. Increasing amounts of methane, ethylene and n-butane were emitted as the fuel-air mixture became richer and the engine speed decreased. As the temperature of adsorber increased, high-number carbons into low-number carbons. Thus, the C4 concentration decreased significantly during the first 30 seconds, and the C2 concentration increased continuously.

• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.2
• /
• pp.225-231
• /
• 1998

Flame propagation speed characteristics of methante-air mixtures were experimentally investigated in combustion chamber modelled engine. Flame propagation process was known as a funtion of equivalence ratio initial pressure and initial temperature. Ion probe and schlieren photograph were applied to measure the local flame speed and flame radius in quiescent mixtures. Pressure was also measured to make sure of the reproducibility and to apply combustion analysis. Burning velocity was calculated from the flame propagation speed and combustion analysis. Flames were developed faster with higher initial pressure and initial temperature but showed maximum propagation speed at equivalence ratio 1.1 regardless of initial pressure and temperature. Local flame speed was maximum values at near midpoint between center and wall.