• Journal of Power System Engineering
• /
• v.3 no.3
• /
• pp.22-28
• /
• 1999

The injected liquid does not break-up instantly after injection for diesel engine. There is some unbroken portion, which is the liquid core(The length of liquid core is called the break-up length) in the spray. If the liquid core is longer than the depth of the bowl in the small DI diesel engine, the liquid core impinges on the surface of the piston. Once the liquid core impinges on the surface, it cannot ignite or burn rapidly and thus prolongs burning time with a degradation in thermal efficiency. The break-up length of a diesel spray in a compressure vessel was measured by an electric resistance method, A voltage was applied between the nozzle and screen, bar, needle electrode inserted at various axial and radial positions into atomizing sprays. As a result, a current flows not only in the region of liquid core but also through the droplets of the spray. It is found that the break-up length measured with screen electrode is overestimated. The break-up length of the spray is found to be proportional to the square root of the density ratio of fuel and surrounding gas. The break-up length of the spray decreases as the injection pressure and the back pressure increase.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.9
• /
• pp.569-576
• /
• 2016

The objective of this study was to investigate, using a numerical method, the fuel injection targeting for improving the combustion performance in a HSDI diesel engine. In this work, the ECFM-3Z model was applied as the combustion model, and the injection mass, inclined spray angle, and injection timing were varied for the study on the targeting of fuel spray. The results of this work were compared in terms of cylinder pressure, rate of heat release, and exhaust emissions characteristics. It was found that the cylinder pressure increased when the injection timing was advanced, and the rate of heat release increased when more fuel was injected into the piston bowl. In addition, $NO_x$ emission increased owing to the increase in the rate of heat release. On the other hand, CO and soot emissions decreased because of the improvement in combustion performance.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.3
• /
• pp.103-111
• /
• 2006

The spray behavior of direct-injection spark-ignition(DISI) engines is crucial for obtaining the required mixture distribution for optimal engine combustion. The spray characteristics of DISI engines are affected by many factors such as piston bowl shape, air flow, ambient temperature, injection pressure and fuel temperature. In this study, the effect of fuel temperature on the spray and combustion characteristics was partially investigated for the wall-guided system. The effect of fuel temperature on the fan spray characteristics was investigated in a steady flow rig embodied in a wind tunnel. The shadowgraphy and direct imaging methods were employed to visualize the spray development at different fuel temperatures. The microscopic characteristics of spray were investigated by the particle size measurements using a phase Doppler anemometry(PDA). The effect of injector temperature on the engine combustion characteristics during cold start and warming-up operating conditions was also investigated. Optical single cylinder DISI engine was used for the test, and the successive flame images captured by high speed camera, engine-out emissions and performance data have been analyzed. This could give the way of forming the stable mixture near the spark plug to achieve the stable combustion of DISI engine.