• Journal of the korean Society of Automotive Engineers
• /
• v.1 no.1
• /
• pp.28-41
• /
• 1979

Propane-Air premixed combustible gas was ignited by the conventional current break system inside the open combustion chamber under the atmospheric pressure and the room temperature to measure the flame propagating speed and the burning speed, also to elucidate the history of the propagating flame behavior and wall effects to flame shape by using Ion Gap Method and High Speed Schlieren Photography. The results obtained show that the maximum flame propagating speed and maximum burning speed are approximately 292 cm/sec and 36 cm/sec at the mixture ratio 4.6%, respectively. The cellular flame structures can be observable in the rich mixture region, moreover, the cellular structures become finer, with increasing the mixture strength.

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.1
• /
• pp.82-90
• /
• 2017

The aim of this work is to develop a new computational program to determine the effect of using the gas of propulsion of combustion chamber at high temperature on the shape of the two-dimensional Minimum Length Nozzle giving a uniform and parallel flow at the exit section using the method of characteristics. The selected gases are $H_2$, $O_2$, $N_2$, CO, $CO_2$, $H_2O$, $NH_3$, $CH_4$ and air. All design parameters depend on the stagnation temperature, the exit Mach number and the used gas. The specific heat at constant pressure varies with the temperature and the selected gas. The gas is still considered as perfect. It is calorically imperfect and thermally perfect below the threshold of dissociation of molecules. A error calculation between the parameters of different gases with air is done in this case for purposes of comparison. Endless forms of nozzles may be found based on the choise of $T_0$, $M_E$ and the selected gas. For nozzles delivering same exit Mach number with the same stagnation temperature, we can choose the right gas for aerospace manufacturing rockets, missiles and supersonic aircraft and for supersonic blowers as needed in settings conception.

• Journal of computational fluids engineering
• /
• v.20 no.4
• /
• pp.7-13
• /
• 2015

Vortex tube is a thermal static device that separates compressed air into hot and cold streams. In general, the cooling efficiency of vortex tubes is lower than that of traditional air conditioning equipment and vortex tubes are mainly used for industrial spot cooling applications because of their quick responses. In this study, conical frustums are employed in the nozzle chamber to improve the cooling performance. Conical frustums can be used to decrease the ineffective mass fraction that directly passes through the cold exit without energy separation. The shape optimization of conical frustums has been performed using full factorial design. It is found that the height of frustums has the largest main effects on the cooling performance. Computational results show that the cooling performance can be increased by about 10% within the considered range of the design parameters. This is because the ineffective mass fraction toward the cold exit is decreased by about 20%.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.3
• /
• pp.77-84
• /
• 2002

Measurements of NO and NOx emission of laminar partially premixed LPG/air flames with and without acoustic excitation are reported. The NOx emission at the tailpipe of a combustion chamber is determined by chemiluminescent analyser. The NOx measurements are taken in flames with several different center tube equivalance ratio( ø$\sub$o/), and overall equivalace ratio(ø$\sub$o/) for a fixed fuel flowrate. The NOx emission decrease to reach a minimum value at an optimum ø$\sub$c/ 2. Theø$\sub$c/ 2 flame gives a compromise of thermal NO and prompt NO mechanism. In the case of excitation. the visual shape of the flame is changed from laminar flame to turbulent-like flame. With increasing levels of excitation amplitude, an optimum value of the NO and NOx emission exists. A shorter flame caused by the enhanced upstream mixing due to acoustic excitation results in the reduction of NO and NOx emission in the present flames. The reduction of flame length affects the shorter residence time of center tube mixture, and significantly influences the NOx reduction.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.7 no.1
• /
• pp.15-23
• /
• 2001

In regulation of IGC code 12.1 mechanical ventilation should be arranged to ensure sufficient air movement through the space to avoid the accumulation of flammable or toxic vapours and ensure a safe working environment, but in no case should the ventilation system have a capacity of less than 30 changes of air per hour baed upon the total volume of the space. In this study, a scaled mode chamber was constructed to investigate the ventilation characteristics and stagnation area in the hood room of LNG carrier and pump room in tanker. An experimental study was performed on the model by using visualization equipment with a laser apparatus and an image intensifier CCD camera. Twelve different kinds of measuring areas were selected as the experimental condition. Instant simultaneous velocity vectors in the whole fields were measured by a 2-D PIV system A three-dimensional numerical simulation was also carried out for three different Reynolds numbers. Then the CFD predictions were discussed with the experimental results. The results show the spiral L-shape flow that moves from the opening on the left wall diagonally to the upper right part dominates the ventilation structure. The stationary area of hood room in the velcoity distributions was located in the upper left stern part.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.303-306
• /
• 2011

An experimental study has been conducted to investigate the effects of an ultrasonic standing-wave field to the behavior of methane/air premixed flame. Visualization technique utilizing the schlieren method was employed for the observation of premixed flame behavior. The shape of flame front and local flame velocity were measured according to the variation of reactants pressure and chamber opening/closing condition. The flame front was distorted and severely deformed to a lotus-type flame by the interaction of ultrasonic standing-wave and the reflection wave coming from an end wall of reactor.

• 한국연소학회:학술대회논문집
• /
• 2007.05a
• /
• pp.139-144
• /
• 2007

A micro cyclone combustor was developed to be used as a component of mobile power generator (MPG). The cyclone combustor was designed so that fuel and air were supplied to the combustion chamber separately to prevent a flash-back. The flame shape stabilized inside the micro cyclone combustor was visualized experimentally and the flow field and the combustion characteristics of the combustor were investigated numerically. The global equivalence ratio (${\Phi}$), defined using the fuel and air flow rates, was introduced to examine the overall flow and flame features of the combustor. The flame stabilization mechanism could be well understood using the velocity distribution inside the combustor. For only non-reacting case, it was found that a weak recirculating zone was formed upper the fuel-supplying tube in case of ${\Phi}$ < 1.0. It was also found that small regions that have a negative axial velocity exist near the fuel injection ports for both of non-reacting and reacting case. It was identify that a flame front was stabilized at the negative axial velocity regions near the fuel injection ports.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.162-168
• /
• 2001

In the present study, flow visualizations, hot-wire velocity measurements and computational fluid dynamics were performed in order to determine complicated air flow characteristics in a neonate incubator. In this study, following conclusions can be made: (1) The flow visualization technique developed in the present study revealed an enough qualitative information for the flow field in the neonate incubator. Flow structures in a neonate incubator with a realistic three-dimensional shape was successfully visualized the present study. (2) Results from the flow visualization were relatively in good agreements with those obtained from the computational fluid dynamics. (3) Velocities very near the neonate measured by the hot-wire anemometer were relevant to those obtained from the computational fluid dynamics. (4) Temperatures were higher at the neck region and the medial aspect of both thighs, but lower in both extremities. (5) Small vortices between the neonate and the mattress might interfere with convective and evaporative heat transfers on the neonate's surface. In the fluid dynamic aspect, it is important to eliminate the formation of these small vortices for the design of incubator chamber.

• Tribology and Lubricants
• /
• v.33 no.5
• /
• pp.214-219
• /
• 2017

Abrasive fluidized bed machining (AFBM) is similar to general abrasive fluidized machining (AFM) in that it can perform polishing of the outer and inner surfaces of a 3-dimensional shape by the flow of particles. However, in the case of AFM, the shear force generated by the flow of the particles causes material removal, while in AFBM, the abrasive particles are suspended in the chamber to form a bed. AFBM can be used for deburring, polishing, edge contouring, shot peening, and cleaning of mechanical parts. Most studies on AFBM are limited to metals, and research on application of AFBM to plastic materials has not been performed yet. Therefore, in this study, we investigate the effect of rotating speed of the specimen and the air flow rate on the material removal characteristics during AFBM of polyacetal with a horizontal AFBM machine. The material removal rate (MRR) increases linearly with increase of the rotating speed of the main shaft because of the shear force between the particles of the fluidized bed and the rotation of the workpiece. The reduction in surface roughness tends to increase as the rotating speed of the main shaft increases. As the air flow rate increases, the MRR tends to decrease. At a flow rate of 70 L/min or more, the MRR remains almost constant. The reduction of the surface roughness of the specimen is found to decrease with increasing air flow rate.

• Fashion & Textile Research Journal
• /
• v.2 no.5
• /
• pp.416-422
• /
• 2000

In this study, to find out the physiological reaction of the human body and the sensation of comfort when people are wearing sportswear which is made of waterproof breathable fabrics under general environmental conditions (temperature : $20{\pm}1^{\circ}C$, humidity : $60{\pm}5%RH$, air current : 0.1 m/sec) and rainy environmental conditions (temperature : $20{\pm}1^{\circ}C$, humidity : $60{\pm}5%RH$, air current : 0.1 m/sec, rainfall : 250 1/hr), we made an experiment with sportswear in an artificial climate chamber and studied the thermal physiological response and subjective sensation. Mean skin temperature of the subjects was low and had a big range of fluctuation in rainy environmental conditions of two condition. Temperature started to increase at the beginning of the exercise, reached the maximum at the 2nd level of the exercise and then started to decline. Rectal temperature showed a slighter increase and bigger range of fluctuation in general conditions than in rainy conditions. Except clothing micro climate in rainy conditions, temperature and humidity and their range of fluctuation around back were higher than those around chest. Humidity was high and had wide range of fluctuation in general conditions. Heart rate was 4.4 beats/min higher in general conditions. In subjective test on rainy conditions, the feeling of discomfort increased due to the raindrops fallen on the skin. Unlike that in general conditions, cold sensation increased and humidity sensation reached to the peak after the exercise. In wearing sportswear made of shape memory breathable waterproof fabric, controlling function over a small amount of heat and water was distinctive while it turned out to be not so comfortable over a large amount of heat and water. Through this, the limitation of shape memory breathable waterproof fabric was recognised.