• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.76-86
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• 1994

Combustion of diesel engine depends on the mixing of air and evaporating fuel during ignition delay greatly. Variation of air-fuel mixing rate and ignition delay for engine operating condition causes difference of combustion, performance and exhaust emissions. This study is investigated in a turbocharged diesel engine of IDI swirl chamber type. In the results, As injection timing is advanced until $12.6^{\circ}$ BTC, ignition delay decreases. NOx concentration and smoke level in exhaust gas increases for advanced injection timing Ignition delay, combustion period, pressure rise rate and exhaust gas temperature are increased with increasing engine speed. And ignition delay at high load is more decreased than that at low load. Ignition delay and combustion period are decreased with increasing intake pressure. Power increases, temperature and CO, NOx concentration in exhaust gas decreases as intake pressure increases. With increasing load, ignition delay is decreased and combustion period, motoring pressure are increased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.69-72
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• 2011

Hot-firing tests were performed on the third sub-scale gas generator for development of a 75 ton-class liquid rocket engine. This paper deals with the analysis results of low-frequency combustion instabilities that were encountered during combustion tests of the gas generator. The low-frequency pressure fluctuations seem to be related to chamber pressure and pressure drops through oxidizer/fuel injectors.

• Current Optics and Photonics
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• v.8 no.2
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• pp.170-182
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• 2024

The dimensional accuracy and consistency of a dual oil circuit centrifugal fuel nozzle are important for fuel distribution and combustion efficiency in an engine combustion chamber. A point cloud measurement method was proposed to solve the geometric accuracy detection problem for the fuel nozzle. An improved variance focus measure operator was used to extract the depth point cloud. Compared with other traditional sharpness evaluation functions, the improved operator can generate the best evaluation curve, and has the least noise and the shortest calculation time. The experimental results of point cloud slicing measurement show that the best window size is 24 × 24 pixels. In the height measurement experiment of the standard sample block, the relative error is 2.32%, and in the fuel nozzle cone angle measurement experiment, the relative error is 2.46%, which can meet the high precision requirements of a dual oil circuit centrifugal fuel nozzle.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.1-8
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• 2020

In this study, a configuration design of a CH₄/LOx small rocket engine was made and test system was established for the performance evaluation. A coaxial swirl injector was chosen because of its remarkable atomization performance and low combustion instability. Three aspect ratios for the combustion chamber configuration, i.e., 1.5, 1.8, and 2.1 were also set for the comparison of the combustion efficiency. The reliability of the thrust measurement rig was enhanced by pre-and post-calibration process. From the preliminary ground hot-firing test, the measured thrust and specific impulse values were 89.2 N and 181.8 s, respectively, which were 21.6% lower than the ideal values. In addition, the efficiency of characteristic velocity was measured as 84.2%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.615-627
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• 1997

An experiment was performed to local heat transfer coefficient and Nusselt number in the circular duct of 180.deg. bend for Re=6*10$^{4}$, 8*10$^{4}$ and 1*10$^{5}$ at swirling flow and non-swirling flow conditions. The test tube with circular section was made by stainless which has curvature ratio 9.4. The wall of test tube was heated directly by electrical power to 3.51 kw and swirling motion of air was produced by a tangential inlet to the pipe axis at the 180 degree. Measurements of local wall temperatures and bulk mean temperature of air are made at four circumferential positions in the 16 stations. The wall temperatures show particularly reduced distribution curve at bend for non-swirling flow but this effect does not appear for swirling flow. Nusselt number distributions for swirling flow which was calculated from the measured wall and bulk temperatures were higher than that of non-swirling flow. Average Nusselt number of swirling flow increased about 90 ~ 100% than that of non-swirling flow whole through the test tube. The Nu/N $u_{DB}$ values at the station of 90.deg. for non-swirling flow and swirling flow are respectively about 2.5 and 4.8 at Re=6*10$^{4}$. Also that is good agreement with Said's result for non-swirling flow. flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.991-997
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• 2014

This study investigated the swirling flow fields of a gun-type gas burner (GTGB) without a combustion chamber under cold flow conditions. Three velocity components and the static pressure were measured with a straight-type five-hole pressure probe (GHPP) using a non-nulling calibration method and compared with the results of an X-type hot-wire probe (X-probe) and computational fluid dynamics (CFD). The GHPP measured the velocity and static pressure for the swirling flow of the central region of the GTGB better than the X-probe but produced slightly worse results than the CFD.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.3
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• pp.1-6
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• 2007

A 3-tonf-class high pressure sub-scale combustor was designed and manufactured to study the performance improvement of combustor. The combustor consists of a combustion chamber with film cooling, thermal barrier coating and water cooling channels to prevent thermal demage of the hardware and an injector head with 37 coaxial swirl injectors. Hot-firing tests were carried out at the design point with varying flow rate for film cooling. The test result revealed that the increase of film cooling flow rate decreases the combustion performance, but in the cases of similar film cooling flow rates, the combustion performance is dependent on the mixture ratio of main injector excluding the film cooling flow rate.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.47-53
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• 2015

Design parameters required for Methane/oxygen bipropellant small-rocket-engine were derived through a theoretical performance analysis. The theoretical performance of the rocket engine was analyzed by using CEA and optimal propellant mixture ratio, characteristic length, and optimal expansion ratio were calculated by assuming chemical equilibrium. A coaxial-type swirl injector was chosen because of its outstanding atomization performance and high combustion efficiency compared to other types of injector and also a bell nozzle with 80% of its full length was designed. The rocket engine configuration with 1.72 MPa of chamber pressure, 0.18 kg/s in total propellant mass flow, and O/F ratio of 2.7 was proposed as a ground-firing test model.

• Korean Journal of Agricultural Science
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• v.11 no.2
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• pp.284-294
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• 1984

Effects of orifice diameter, operating angle and swirl chamber distance were examined to study a reasonable distribution pattern on the maximum available travel distance in the triple nozzle system. The results of the study were as follows; 1. Discharge rate was increased with increase of orifice diameter, and a quadratic line for the 1st nozzle and linear lines for the 2nd or the 3rd nozzle. 2. The operating angle of $15^{\circ}$ had showed the maximum available travel distance, and 17m in orifice diameter of 3.0mm and operating pressure of $24.5{\times}10^5pa$ ($25Kg/cm^2$). 3. Nozzle setting methods (reference Table 6.) for improvement of uniformity of deposit distribution were varied depending on the size of orifice diameter of the 1st nozzle, nevertheless coefficients of uniformity were improved about 6 percents. 4. Adjustment of the swirl chamber distance of the 2nd nozzle could improve the minimum area of about 6m from the triple nozzle.

• Korean Journal of Agricultural Science
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• v.14 no.1
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• pp.81-97
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• 1987

Two nozzles with different size (Figure 2) were particularly designed to supply air through the swirl core into the central part of the liquid stream in the same parallel direction to produce a well-mixed air and water in the whirl chamber as spray liquid in bubble formation. Atomization was attempted to improve by using both the preliminary break-up process with less viscosity and less surface tension in the whirl chamber and the effects of increased frequency of the band of drops with the raised ambient air density in front of the nozzle orifice. The volumetric ratio between spray liquid and air on four levels was used to investigate the effects of air as a component of the mixture on atomization. The results of the experiment were summarized as follows; Droplet size became progressively finer as the operating pressure was increased in the range of $0.70kg/cm^2$ to $6.33kg/cm^2$, which was similar to the previous works. The new atomizing mechanism so-called 'air-center nozzle' gave a narrower range in droplet size distribution with smaller volumetric median diameter (VMD) than that of the existing spray system at a given pressure, which showed the possibility of improvement of atomization in a certain limit. The volumetric median diameter produced by the new atomizing mechanism was decreased from the central region toward the exterior edges across the spray pattern.