• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.6
• /
• pp.11-19
• /
• 2013

An experimental study was conducted to investigate fuel injection characteristics through swirl injectors when the fuel was heated to very high temperature conditions. Three swirl injectors with different orifice diameters and swirler geometries were used to measure the flow coefficient (${\alpha}$) for the injection pressure ranges between 3 and 10 bar and the fuel temperature from 50 to $270^{\circ}C$. The results showed that the variation characteristics of ${\alpha}$ with respect to cavitation number ($K_c$) were highly dependent on both the orifice diameter and the swirler geometry. In addition, the characteristics of ${\alpha}$ variation with respect to AR, the area ratio of the flow through the swirler and the orifice, has revealed that the effect of boiling is retarded but the slope of decreasing ${\alpha}$ after the boiling effect is present tumbles as AR increases.

• Journal of Energy Engineering
• /
• v.7 no.1
• /
• pp.17-23
• /
• 1998

A simplified experiment was performed to figure out the atomization characteristics of highly viscous liquid of rice-bran oil by applying ultrasonic energy to improve the atomization of spray droplets. A spray system, an ultrasonic system, and three kinds of pintle-type nozzles(pin-edge angle: 5 , 10 , 15 ) were manufactured. To investigate the effects of ultrasonic energy on the atomization of a highly viscous liquid, a phase doppler particle analyzer was used for the measurement and calculation of spray droplets data. Nozzle opening pressures were chosen of 3 levels, i.e, 10, 13, 16 MPa. As a result, it could be concluded that the ultrasonic energy was effective to improve the spray atomization when applied to the fuel by means of 3 different nozzles because of the effects of the liquid fuel cavitation and relaxation between molecules caused by ultrasonic energy. The improvement rate of the spray atomization by the ultrasonic spray atomization by the ultrasonic spray compared with the conventional spray was about 10% increase in the case of pintle type nozzles. With the increase of pin-edge angles the distribution lines by nozzle opening pressures are declined for both conventional and ultrasonic sprays. This means that the increase of the pin-edge angle improves the atomization of sprays.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.10
• /
• pp.33-39
• /
• 2019

The improvement of emissions, fuel economy, and combustion noise is a primary target in the development of heavy-duty diesel engines. Multiple injection has been introduced as one of the most promising strategies for this goal. In this research, various multiple injection methods were applied to achieve the optimal strategy in terms of emissions, fuel economy, and combustion noise. In the case of one pilot injection, the smoke emission deteriorated, while the NOx emission was reduced. In the case of 2 pilot injections, the NOx and smoke emissions were reduced by 73% and 84%, respectively. In this case, the combustion noise was analyzed with the maximum pressure-rise rate, and the fuel economy was evaluated with the help of the indicated specific fuel consumption. A 15%:15% 2-pilot injection strategy accomplished improvements of 32.9% for NOx, 60.4% for smoke, 1.95% for fuel consumption, and 19.4% for combustion noise compared to the case of single injection. Based on the data, an optimal injection strategy will be developed for a greater operating range in future work.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.18 no.2
• /
• pp.42-51
• /
• 2014

An experiment was conducted to study fuel injection characteristics of high boiling point test fuels (HBPTF), which are newly developed with higher boiling points than conventional aviation fuels, for various injection pressures when the fuel was heated to the temperature higher than their boiling points. The injection characteristics with elevating fuel temperature were quantified by the flow coefficient (${\alpha}$) and the cavitation number ($K_c$), and it was found that the trends between ${\alpha}$ and $K_c$ for various fuels were very similar with each other. In addition, compared with a conventional fuel, HBPTFs not only have higher fuel temperatures at which the effect of fuel boiling on the injection initiates, but also are less affected by the fuel boiling inside the injectors at temperatures over the boiling point.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.12 no.5
• /
• pp.1-8
• /
• 2008

Dual-mode Phase Doppler Anemometry (DPDA) was used to scrutinize the spatial distribution characteristics of spray emanating from a small Liquid-Rocket Engine (LRE) injector. Droplet size and velocity were measured according to the variation of injection pressure along the plane normal to the spray stream and then the spray characteristic parameters such as Arithmetic Mean Diameter (AMD), Sauter Mean Diameter (SMD), number density, span of drop size distribution, and volume flux were deduced for an investigation of spray breakup characteristics. As the injection pressure increases, the number density, span, and volume flux of spray droplets become higher, whereas the AMD gets smaller.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.10a
• /
• pp.9-12
• /
• 2004

A numerical simulation is presented for investigating the effects of pressure ratio of $D_2$ injector to supersonic nozzle on the Population inversion in the DF chemical laser cavity, while a latins concurrently takes place. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules, while simultaneously estimating the maximum small signal gains and power in the DF chemical laser cavity. Major results reveal that the higher $D_2$ injection pressure provides a favorable condition for $DF^{(1)}$-$DF^{(0)}$ transition to generate the higher power laser beam.

• Journal of ILASS-Korea
• /
• v.22 no.1
• /
• pp.1-7
• /
• 2017

Recently, Performance and fuel efficiency of gasoline engines have been improved by adopting direct injection (DI) system instead of port fuel injection (PFI) system. However, injecting gasoline fuel directly into the cylinder significantly reduces the time available for mixing and evaporation. Consequently, particulate matters(PM) emissions increase. Moreover, as the emission regulations are getting more stringent, not only the mass but also the total number of PM should be reduced to satisfy the Euro VI regulations. Increasing the fuel injection pressure is one of the methods to meet this challenge. In this study, the effects of increased fuel injection pressures on combustion and emission characteristics were experimentally examined at several part load conditions in a 1.6 liter commercial gasoline direct injection engine. The main combustion durations decreased about $2{\sim}3^{\circ}$ in crank angle base by increasing the fuel injection pressure due to enhanced air-fuel mixing characteristics. The exhaust emissions and number concentration distributions of PM with particle sizes were also compared. Due to enhanced combustion characteristics, THC emissions decreased, whereas NOx emissions increased. Also, the number concentrations of PM, larger than 10 nm, also significantly decreased.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.4
• /
• pp.298-304
• /
• 1984

본 연구에서는 저자들이 디이젤기관 제조업체에서 디이젤 기관의 성능개선을 효율적으로 수행하기 위하여 기업체 연구소에서 쉽게 적용할 수 있는 시뮬레이션 프로 그램을 개발하는 과정에서 수행된 것이며, 아울러 각 기관 회전수에서의 연료분사 관 내에서의 압력변화와 노즐 니이들 밸브 양정을 측정함으로써 수학적 시뮬레이션 결과 와 실제결과를 비교할 수 있게 하였다. 그 결과, 개발된 시뮬레이션 프로그램은 실 제 연료분사 과정을 충분히 잘 예측할 수 있었으며, 향후 이 프로그램을 이용하여 연 료분사계의 조정에 의한 디이젤기관 성능개선을 효율적으로 수행할 수 있을 것으로 기 대한다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.9
• /
• pp.909-916
• /
• 2015

In this study, to investigate the effect of spray behavior characteristics, we induce the mixing ratio of emulsified fuel using impinging spray. We formulate the emulsified fuel by mixing diesel and hydrogen peroxide($H_2O_2$). We set the temperature of the heating plate to $150^{\circ}C$, $200^{\circ}C$, and $250^{\circ}C$, and set the injection pressures to 400, 600, 800, and 1000bar. The surfactants for the emulsified fuel mixture, which were mixed span80 and tween80 was mixed as 9:1, were fixed to 3% of the total volume of the emulsified fuel. We set the mixing ratio of $H_2O_2$ in the emulsified fuel as emulsified fuel(EF)0, EF2, EF12, and EF22. Further, we visualize the evaporation impinging spray using the Schlieren method. Based on the results of this study, we found that a higher temperature and injection pressure of the heating plate impingement led to the active diffusion of the fuel vapor, which promoted emulsified fuel evaporation. When the emulsified fuel is utilized in an actual engine, because of the temperature-drop effect of the combustion chamber, which is due to the evaporation of $H_2O_2$ in fuel and faster mixture formation is expected to decrease the engine emissions.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.3
• /
• pp.92-100
• /
• 2005

An optimal fuel manifold is suggested to improve the cooling performance of an injector face plate. The cooling performance at the center area of the injector face plate is to be augmented while the spatial injection uniformity is maintained. The comparison of the cooling performance of f candidates gives the conclusion that the dividing plate from 2-3 injector .ow to 9-10 injector. row is an optimal. The maximum face plate temperature decreases by 27$\%$ while the injection uniformity is close to that of the original design. The pressure drop in the fuel manifold of the optimal design is also same as the original design.