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For further increase in thermal efficiency of heavy-duty diesel engines, flexible regulation of the heat release rate (HRR) profile combined with higher compression ratio could have more rooms to improve indicated thermal efficiency by overcoming various drawbacks relevant to higher compression ratio. A new ideal HRR profile, which starts as a kind of delta shape to fulfil the isobaric cycle from top-dead-center (TDC) and is followed by the significant increase in HRR to reach the maximum cylinder pressure in the retarded timing, was proposed. We call it as ‘High-heels’ HRR profile from its two-step-increase delta shape. To confirm the potential of the ideal HRR profile by utilizing a single- cylinder heavy-duty diesel engine, a variable fuel injection rate equipment, novel combustion chamber designs, and an offset orifices nozzle were investigated as the technologies for modifying HRR profile.

The set-off length (also referred to as the “lift-off length”) is reduced by the re-entrainment of the burned gas by the backward flow surrounding a diesel spray jet produced by a multi-hole nozzle. In the present study, to estimate the equivalence ratio at the set-off length, a means of estimating the amount of burned gas that is re-entrained into the near-nozzle region of the diesel spray jet was established. The results revealed that the suppression of soot formation in quasi-steady diesel spray flames produced by a multi-hole nozzle and a high injection pressure is not attained by reducing the equivalence ratio at the set-off length. Analysis of the amount of soot along the spray axis using a two-color method revealed that the maximum soot amount position appears in a quasi-steady spray flame, after the collapse of the head vortex in which a dense soot cloud is formed. The maximum soot amount position does not change even if the injection pressure varies.

With the diesel emissions and fuel consumption regulations and laws being tightened up, Common Rail System (CRS), capable of accurate and high-pressure diesel fuel injection, has become very popular in the world, and this CRS market is expected to continue to grow in the future. As use of the CRS becomes widespread, CRS is supposed to be used in a wide variety of environment, e.g. bad fuel (for example, much dust [1] and/or water), which increases concerns of CRS reliability. In an attempt to cope with such bad fuel properties, CRS and Fuel collected from the market was investigated. And based on this result, a new test method was worked out to simulate fuel stresses in the market. This test method verified the improved design of CRS with enhanced fuel robustness. This paper describes the new test method and the fuel robustness-enhancing effect of CRS based on the test method.

The challenge for the diesel engines today is to reduce harmful emissions, such as particulate matter (PM) and Nitrogen oxides (NOx), and enhance the fuel efficiency and power, which are its main advantages. To meet this challenge, DENSO has developed an advanced common rail system (CRS) that uses piezo actuated fuel injectors capable of delivering up to five injection events per combustion cycle at 180MPa, currently the world's highest commercially available diesel fuel injection pressure. The DENSO piezo injector incorporates an internally developed piezoelectric element that energizes quicker than its solenoid counterpart, thereby reducing the transition time for the start and end of the fuel injection event. The piezoelectric element and unique passage structure of the DENSO injector combine to provide a highly reliable and responsive fuel injection event.

There is increasing demand for a finer atomization of fuel spray in order to improve the engine performance and mileage, reduce exhaust emissions and then improve the transient response. [1]. We are improving the shape of holes in order to enhance finer atomization. It is especially important to reveal the spray break-up process and droplet diameter quantitatively for a better development of holes shape. In this paper, we set our focus on a multiple-hole nozzle and developed a quantitative visible analysis method to investigate the spray break-up process and droplet diameter. With this method, index of the relationship between break-up process and droplet diameter was defined. And by re-shaping the holes and by arrangement of the holes, the break-up process and droplets diameter were investigated.

In an effort to protect the earth's environment, emission regulations in the diesel engine field are becoming increasingly strict. One way of meeting these regulations is to atomize the fuel spray by using a fuel injection system with high-pressure injection, which activates engine combustion. With current in-line pump systems, however, it is still possible to satisfy the demand for cleaner emissions by improving the fuel spray, through measures such as reviewing high-pressure injection and initiating improvements in the nozzle. This report describes the new in-line pump system for medium duty diesel engines to meet future emission regulations. In this report, we will describe how analytical technology, such as computer simulation, was used on the pump side to make improvements for higher injection pressure.