采用可控散射喷嘴的高响应柴油喷油器和闭环喷油控制实现稳定性燃烧的研究

共轨系统自1996年首次推出以来,柴油机性能已得到了显著提升。多年来,共轨技米持续发展,降低了发动机燃油消耗和排放,提高了驾驶性能。然而,为满足世界范围内持续严格的排放限值并提供性能更加优越的柴油车,还需进一步提升燃烧精确控制技术。通过精确控制喷油量并提高喷油压力,共轨喷油器可显著提升燃烧性能,此外,还需要更接近矩形的喷油规律、更短间隔期内稳定多次喷射的能力及喷雾形状控制来优化燃油混合。另外,在优化喷射和燃烧时,还需考虑世界范围内燃油品质的不同。分别阐述了两种能够实现以上目标的创新喷油器技术,第一种是第四代压电喷油器(G4P)及具有特殊孔状(可控散射喷雾(CDS))的新型喷孔设计,有助于提高燃烧性能。其优势是降低热损失,提高燃烧效率。第二种是通过闭环控制提高喷油量的精确性,实现稳定性燃烧。主要实现途径是基于内置在喷油器中的压力传感器检测实际的喷油速率和燃油特性。上述两个技术是提高发动机性能和针对世界范围内所用燃油品质的多样性以改善燃烧稳定性的关键技术。

Pressure Drop Control Using Multiple Orifice System in Compressible Pipe Flows

In order to investigate the effectiveness of an orifice system in producing pressure drops and the effect of compressibility on the pressure drop, computations using the mass-averaged implicit Navier-Stokes equations were applied to the axisymmetric pipe flows with the operating pressure ratio from 1.5 to 20.0. The standard k- ε turbulence model was employed to close the governing equations. Numerical calculations were carried out for some combinations of the multiple orifice configurations. The present CFD data showed that the orifice systems, which have been applied to incompressible flow regime to date, could not be used for the high operating pressure ratio flows. The orifice interval did not strongly affect the total pressure drop, but the orifice area ratio more than 2.5 led to relatively high pressure drops. The total pressure drop rapidly increased in the range of the operating pressure ratio from 1.5 to 4.0, but it nearly did not increase when the operating pressure ratio was over 4.0. In the compressible pipe flows through double and triple orifice systems, the total pressure drop was largely due to shock losses.