• Journal of ILASS-Korea
• /
• v.9 no.4
• /
• pp.38-45
• /
• 2004

This study describes the analysis results of unsteady cavitating flows behavior inside nozzle of the prototype piezo-driven injector. This piezo-driven injector has been recognised as one of the next generation diesel injector due to a higher driven efficiency than the conventional solenoid-driven injector. The three dimensional geometry model along the central cross-section regarding of one injection hole has been used to simulate the cavitating flows for injection time by at fully transient simulation with cavitation model. The cavitation model incorporates many of the fundamental physical processes assumed to take place in cavitating flows. The simulations performed were both fully transient and 'pseudo' steady state, even if under steady state boundary conditions. We could analyze the effect the pressure drop to the sudden acceleration of fuel, which is due to the fastest response of needle, on the degree of cavitation existed in piezo-driven injector nozzle

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.10
• /
• pp.60-65
• /
• 2003

An experimental study was performed to understand ignition characteristics of gas turbine combustor with rotating fuel injection system. Liquid fuel applied to the inner surface of rotating fuel nozzle which was driven by high speed electrical motor is flung away by centrifugal forces. The real scale combustor and test rig was manufactured and tested under atmospheric condition in KARl combustion test facility. From the test results, this combustor ignition characteristics are highly dependent upon fuel nozzle rotating speed. Futhermore, combustor exit gas temperature was rapidly changed by increasing or decreasing the fuel nozzle rotating speed.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.2
• /
• pp.271-278
• /
• 1987

The experimental study was carried out to investigate the pressure fluctuation, operating frequency, noise emission and combustion characteristics in an aero-valved pulsating combustor. Measurements of the pressure fluctuation, mean temperature and ion current inside the combustion chamber indicate that combustion phenomena are characteristically similar to those in the diffusion flame. The measured frequency schedue indicates that the acoustic theory of the quarter wave tube can be approximated to give the operating frequency, but correction factor must be involved to estimate the correct operating frequency. The spectral behavior of the noise emission exhibits that frequency bands with high noise intensity are narrowly restricted to the neighborhood of the operating frequency signalling the low-frequency combustion characteristics of the pulsating combustor. Measurements of the operating characteristics as variation of the fuel nozzle diameter and injection angle with 4 fuel nozzles have been made, and it was found that the system produced the stable operating conditions up to the turn down ratio of 3 when the fuel nozzle diameter is 1.2mm, and the optimum fuel injection angle is thought to be in the neighborhood of 30.deg. radially.

• International Journal of Automotive Technology
• /
• v.4 no.3
• /
• pp.119-124
• /
• 2003

Dimethyl Ether (DME) is an excellent alternative fuel that provides lower particulate matter (PM) than diesel fuel under the same engine operating conditions. Spray characteristical of DME in common rail injection system were investigated within a constant volume chamber by using the particle motion analysis system. The injector used in this study has a single hole with the different orifice diameter of 0.2, 0.3 and 0.4 mm. The injection pressure was fixed at 35MPa and the ambient pressure was varied from 0.6 to 1.5 MPa. Spray characteristics such as spray angle, spray tip penetration and SMD (Sauter mean diameter) were measured. Spray angle was measured at 30d$_{0}$, downstream of the nozzle tip. The measured spray angie increased with increase in the ambient pressure. Increase of the ambient pressure results in a decrease of spray penetration. The experimental result, of spray penetration were compared with the predicted one by theoretical and empirical models. Increase in the ambient pressure and nozzle diameter results in an increase of SMD at a distance 30, 45 and 60d$_{0}$, downstream of the nozzle, respectively.ely.

• Journal of Advanced Marine Engineering and Technology
• /
• v.17 no.4
• /
• pp.49-62
• /
• 1993

It has been a principle research topic on the diesel engine development to increase the efficiency and the performance of engine to satisfy the user's needs for high reliability and durability. However, recently with the worldwide concerns at the global climate change and environmental protection, the main target in the diesel engine research has been changed to solve the exhaust emission problem in order to satisfy the strict emission regulations. To reduce the pollutant for the diesel engine, the researchs on the combustion chamber is the most important and has to be performed first of all. The diesel fuel injection system plays major role to air-fuel mixing process and influences engine output, themal efficiency, reliability, noise, and emissions. The experimental studies were conducted by varying the various parametric conditions and the results were campared with the computation and calculated results by using the fuel injection simulation program developed during previous research. From the experiments, the matching technique of a fuel injection pump and nozzle was conducted to understand under the various parametric conditions. Also, the relations between needle lift and wave propagation characteristics in high pressure pipe were examined. The basic design data from the experimentations and computation works would be applied to actual design works of diesel fuel injection system.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.8
• /
• pp.1101-1110
• /
• 1998

Computational investigation was conducted to examine the performance of a high pressure common-rail fuel injection system which is used to power a passenger car direct injection (Dl) diesel engine. The pipe flows were modeled by one dimensional wave equation and solved by implicit FDM Each volume of injector was considered as chambers with orifice nozzle in connections. These simulation results were compared with the experimental data of Ganser Hydromag. The comparison of needle life and rate of injection between simulation data and experimental data showed quite a good agreement Different shape of injection rate can be made by adjusting the size of inlet orifice and exit orifice in the piston chamber The pilot injection was accomplished by adjusting command signal.

• Journal of Advanced Marine Engineering and Technology
• /
• v.27 no.1
• /
• pp.57-64
• /
• 2003

The characteristics of fuel spray have an important effect on engine performance such as power, specific fuel consumption and emission because fuel spray controls the mixing and combustion process in an engine. Therefore, if the characteristics of fuel spray can be measured, they can be effectively used for improving engine performance. The major factors controlling fuel spray are injection pressure, ambient pressure and engine speed. In this study, the experiment is performed in a high temperature and high pressure chamber. In experiments, spray tip penetration, spray angle and spray tip velocity are measured at various injection pressure (10 and 14 MPa), ambient pressure(3,4 and 5 MPa), fuel pump speed(500, 700 and 900 rpm). Experimental results are useful for deriving an experimental spray equation and design an optimal engine. The results showed that injection pressure, ambient pressure and fuel pump speed are important factors influencing on the characteristics of spray. 1) Injection pressure influences on the characteristics of spray. That is, as injection pressure is increased, spray angle is decreased but spray penetration and spray tip velocity is increased. 2) Spray angle and spray penetration are increased as fuel pump speed is increased.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.2
• /
• pp.28-34
• /
• 2001

Great attentions are paid to HSDI diesel engine for passenger cars because of its high thermal efficiency. The most interesting research in HSDI diesel engine developments is focused on applying common rail system as a fuel injection equipment. In this study, a series of tests are carried out to investigate the effect of injection pressure variation on the smoke and fuel concluded in a small HSDI diesel engine with common rail system. As a result of this study it is concluded that there is an optimum rail pressure dependent on combustion system such as nozzle type, combustion chamber geometry.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.6 s.249
• /
• pp.553-559
• /
• 2006

Most diesel injector, which is currently used in high-pressure common rail fuel injection system of diesel engine, is driven by the solenoid coil energy for its needle movement. The main disadvantage of this solenoid-driven injector is a high power consumption, high power loss through solenoid coil and relatively fixed needle response's problem. In this study, a prototype piezo-driven injector, as a new injector mechanism driven by piezoelectric energy based on the concept of inverse piezo-electric effect, has been designed and fabricated to know the effect of piezo-driven injection processes on the diesel spray structure and internal nozzle flow. Firstly we investigated the spray characteristics in a constant volume chamber pressurized by nitrogen gas using the back diffusion light illumination method for high-speed temporal photography and also analyzed the inside nozzle flow by a fully transient simulation with cavitation model using VOF(volume of fraction) method. The numerical calculation has been performed to simulate the cavitating flow of 3-dimensional real size single hole nozzle along the injection duration. Results were compared between a conventional solenoid-driven injector and piezo-driven injector, both equipped with the same micro-sac multi-hole injection nozzle. The experimental results show that the piezo-driven injector has short injection delay and a faster spray development and produces higher injection velocity than the solenoid-driven injector. And the predicted simulation results with the degree of cavitation's generation inside nozzle for faster needle response In a piezo-driven injector were reflected to spray development in agreement with the experimental spray images.

• Journal of ILASS-Korea
• /
• v.11 no.2
• /
• pp.81-88
• /
• 2006

The spray characteristics of the rotating fuel injection system were investigated. The special test rig was devised to get the spatial and momentary droplet information. This experimental apparatus consists of a high-speed motor, a shaft, a rotating fuel nozzle and an acrylic case. Spray droplet size and velocity were measured by PDPA(Phase Doppler Particle Analyzer) and instantaneous velocity field was measured by 1'IV (Particle Image Velocimetry) system. At the same time, spray visualization was performed by using ND-YAG laser-based flash photography. From these two different laser diagnostic techniques, we could get spatial and instantaneous spray information fur rotating fuel injection system. The results presented in this paper indicate that spray characteristics such as droplet size, velocity and spray pattern were strongly influenced by rotational speed.