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Homogeneous charge compression ignition (HCCI) is a new combustion concept which achieves high efficiency, low nitrogen oxides (NOx), and particulates matter (PM) emissions. In order to realize the HCCI combustion, a homogenous mixture preparation plays an important role in the HCCI engine. However, it is well known that diesel fuel is very difficult to achieve a uniform mixture distribution within the engine cylinder because of its high viscosity and poor fuel vaporization. In order to eliminate these problems, the low viscosity and high volatility Dimethyl ether (DME) was added into diesel fuel to enhance the spray and atomization. The spray tip penetration and spray cone angle of DME/diesel-blended fuel has been examined by using direct photography technology. Measurements were achieved by using spray images taken with a high-resolution CCD camera synchronized with strobe light.

Homogeneous charge compression ignition (HCCI) is a new combustion concept, which achieves high thermal efficiency and ultra-low emissions. In order to realize the HCCI combustion, a homogenous mixture preparation plays an important role in the HCCI engine concept. However, there are some problems for conventional diesel fuel to achieve a uniform mixture distribution in the cylinder because of its high viscosity and low volatility. This paper describes the effects of the DME addition on the spray behavior and atomization characteristics of diesel fuel. Pure diesel fuel, pure DME fuel and DME/diesel blended fuels with DME mass fraction of 25% and 50% were used to evaluate the effects of the DME concentration on the macroscopic and microscopic structure of the steady spray.