To develop injection nozzles and to improve the numerical simulation technology of fuel spray, a measuring technology to analyze the process of disintegration into droplets accurately is required. Performances required by a spray droplets measuring device are: “ability to measure in the combustion condition inside the engine cylinder”, “ability to measure the diameter of spray droplets in high-density fields”, “ability to measure the structure of spray droplets in 3D”, and an improved measuring accuracy of non-spherical droplets. These elements are required in order to analyze the spray droplets structure of gasoline direct injection engines.
As a promising method to satisfy these requirements, the laser holography method has been already suggested. However, it has some drawbacks, such as a difficulty in measuring spray droplets in high-density fields and over a long analysis period. In order to enable measurement of spray droplets in high-density fields, the authors have made some improvements to the optical system of recording. With these improvements, we have achieved a resolution of 5.3um or higher in a space corresponding to the engine cylinder (high temperature and high pressure) and a measuring accuracy of 0.16um in high-density fields. To reduce time required for analyze an enormous amount of droplets, we have developed an automatic analysis device.
In this paper, we report the droplet size analysis of port fuel injectors and gasoline direct injectors by using the developed method. Furthermore, we have researched the behavior of the droplet size of the impinging spray in a space corresponding to the engine cylinder.