• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.108-115
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• 2014

In this study, experimental approaching method was applied under and single-cylinder engine to research the performance of direct needle-driven piezo injector (DPI) for CR direct-injection. As key-point factor of this DPI that relies on direct-acting operating of injector needle, unlike conventional hydraulic-servo, its nozzle needle can be directly driven by piezo actuator. Thus, effect of direct-acting injection of DPI on diesel combustion and emission characteristics was investigated under common-rail single-cylinder direct-injection engine, equipped with three different driving mechanism, including indirect-acting solenoid, piezo and DPI system. As main results, it found that a direct-acting piezo injector has higher of IMEP. And it has higher heat release rate during premixed combustion and mixing controlled combustion phase due to its higher heat release, even though nitrogen oxide (NOx) formations were increased slightly.

• Journal of Biosystems Engineering
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• v.32 no.2 s.121
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• pp.97-101
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• 2007

A CRDI diesel engine used to commercial vehicle was fueled with diesel fuel and 5% biodiesel blended fuel (BDF 5%) and tested at the Seoul-10 mode for 150 hours. Engine dynamometer testing was completed at regularly scheduled intervals to monitor the engine performance and exhaust emissions. To check the engine parts (valve, injector), the engine was inspected after 150 hours running test. It was concluded that there was no unusual deterioration of the engine, or the changes in engine power (below 2.6%), smoke (below 6.2%), NOx (below 2%) and durability characteristics in spite of operation of 150 hours run with BDF 5%. The difference of kinetic viscosity for engine oil (before and after durability testing) was below 0.36%

• Journal of ILASS-Korea
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• v.17 no.2
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• pp.57-63
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• 2012

For reduction of CO, NOx and soot emission emitted by diesel diffusion combustion, the authors focused on injection actuator to improve fuel availability inside combustion chamber. In this study, it was investigated the internal dynamic characteristics of two-stage injection with diesel injectors with different driving type for the common rail direct injection by using the AMESim simulation code. The analysis parameter defined such as fuel pressure, injection hole's diameter and driven voltage. As the results, it was shown that the piezo-driven injector had a faster response and had better control capability than the solenoid-driven injector. It was found the piezo-driven injector can be utilized effectively as multiple injector than solenoid-driven injector.

• Journal of ILASS-Korea
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• v.17 no.3
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• pp.158-163
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• 2012

This paper presents spray characteristics of piezo-driven type common-rail injector and comparisons to those of solenoid-driven type. Experiments were conducted to measure spray penetraion and SMD distributions using a spray visualization system and PDPA (phase Doppler particle analyzer) system. Injection conditions including injection pressure and energizing durations were varied in order to analyzing effects of injection conditions on spray characteristics. Furthermore, ambient pressures were increased for keeping ambient gas density close to in-cylinder pressure of diesel engine. Results showed that injection delay of piezo-driven type injector was much shorter than those of solenoid driven type and exhibited enhanced atomization performances.

• Journal of ILASS-Korea
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• v.24 no.2
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• pp.66-72
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• 2019

Diesel vehicles suffer from poor starting and running problems at cold temperatures. Diesel vehicles have the characteristic that CO and PM are reduced or similarly discharged when going from low temperature to high temperature. In this study, a bypass type piezo injector for electronic control based common rail injection system was used. Numerical analysis using injector drive analysis model was performed to analyze injector drive and internal fuel flow characteristics according to fuel temperature change. The results show that the rate of density change due to the fuel temperature is proportional, and that the effect of the kinematic viscosity is relatively large between $-20^{\circ}C$ and $0^{\circ}C$. Comparing the results of temperature condition at $0^{\circ}C$ and $20^{\circ}C$, it is considered that the viscosity is more correlated with the needle displacement than the pressure chamber of the delivery chamber.

• Journal of ILASS-Korea
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• v.8 no.4
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• pp.31-38
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• 2003

Constant volume combustion chamber has been designed to investigate diesel spray characteristics with Common-Rail injection system to realize high pressure injection. In this study, two methods of measurements, Schlieren shadowgraphy and Mie scattering imaging method ate applied experimentally to study spray form and liquid phase zone in high pressure, high temperature conditions. Diesel fuel is injected at the point which ignited mixture gas is completely burned. The effect of injection pressure, injector hole diameter, ambient gas temperature and density are investigated experimentally.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5980-5987
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• 2014

As a response to exhaust gas regulations, the electronic control system was applied to the diesel engine. The injected fuel mass and injection timing are accurately controlled using it, and the fuel efficiency and the engine output are significantly increased. In addition, the noise and the vibration of vehicles are decreased. To maintain the optimal performance of an electronic control diesel engine, it is important to control the fuel injection pressure accurately using the fuel pressure regulator. When the fuel pressure regulator is not worked normally, the failure phenomena (starting failure, staring delay, accelerated failure, engine mismatch et al.) occurred because the fuel pressure is not stabilized and controlled accurately. In this study, the effects on a fuel pressure, return fuel mass flow, and engine rotating speed according to the control rate of fuel pressure regulator were investigated to analyze the performance variation under the failure conditions of a fuel pressure regulator. As a result, when the control rate of a fuel pressure regulator decreased by 4%~6% compared to that of the standard condition, the variation of engine rotating speed and return fuel flow were increased greatly, and the abnormal condition occurred. In addition, it is possible to diagnose the failure of a fuel pressure regulator by monitoring these conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.553-559
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• 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
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• v.20 no.4
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• pp.217-222
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• 2015

In this study, Injection rate tests of a Diesel common-rail injector have been performed with injection volume measurement type injection rate test system EMI21 for construction of injector model can be used in an engine calibration mean valued model. The measuring principle of the test system is based on measurement of dispalcement of a movable measurement piston by the volume of fluid released by the injector. From these injection rate test results, the characteristics on shape of instantaneous injection rate and injection fuel amount have been investigated and injection fuel amount calculation equation based on test results has been newly constructed. This equation is very simple and calculation error is less than 5% with test results for wide range injection pressure (200~1800 bar) and injection duration ($200{\sim}1800{\mu}s$) conditions. So, it is anticipated that newly constructed simple injection fuel amount model in this study can be efficiently used on engine calibration and control model.

• Journal of ILASS-Korea
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• v.19 no.1
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• pp.9-14
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• 2014

Performance of DI diesel engine with high-pressure fuel injection equipment is directly related to its emission characteristics and fuel consumption. So, the electro-hydraulic injector for the common-rail injection system should be designed to meet the precise high fuel delivery control capability. Currently, most high pressure injector in use has a needle driven by the solenoid coil energy or the piezo actuator controlled by charge-discharge of output pulse current. In this study, macroscopic spray approaching method was applied under constant volume chamber to research the performance of three different injectors : solenoid, indirect-acting piezo and direct-acting piezo type for CR direct-injection. LED back illumination for Mie scattering was applied on the liquid spray visible of direct-acting piezo injector, including hydraulic-servo type solenoid and piezo-driven injectors. As main results, we found that a direct-acting piezo injector had better a spray tip penetration than hydraulic-servo injectors in spray visualization.