Analysis of ethanol spray behavior into a Single Cylinder Optical Research Engine

The work focuses on studying ethanol spray behavior injected directly inside a spark ignited internal combustion engine in the compression stroke. An experimental procedure for measuring spray penetration and spray overall cone angle produced by a multi-hole direct injector was developed by means of computational codes written in Matlab environment for working with images of spray injections and to acquire calculated results in an automatic way. The shadowgraph technique with back continuous illumination associated with a high speed recording image process was used in a single cylinder optical research engine for acquiring images of Brazilian ethanol fuel injected at 120° before the top dead center of compression stroke. The process of spray injections occurred with engine speeds of 1000 rpm, 2000 rpm and 3000 rpm. The results showed that spray penetrations decrease and spray cone angle increase when the engine speed is raised. The rising pressure behavior in the compression stroke with the upward air flow induced by piston bowl ascendant movement possible decreased the rate of spray penetrations at the end of injections. In the 2000 and 3000 rpm injection cases the ethanol sprays remained in the superior region of the cylinder and do not wetted any cylinder surface while the spray injected in the 1000 rpm case collided with the piston bowl. Single images of sprays at 110° crank angle before the Top Dead Center of compression stroke for the three engine speed cases were qualitatively analyzed and showed macroscopic shapes very coherent with spray penetration and spray cone angle.