The additional operating cash flow that an organization receives from taking on a new project. A positive incremental cash flow means that the company's cash flow will increase with the acceptance of the project.
Investopedia Says:
There are several components that must be identified when looking at incremental cash flows: the initial outlay, cash flows from taking on the project, terminal cost or value and the scale and timing of the project. A positive incremental cash flow is a good indication that an organization should spend some time and money investing in the project.
按照NPV的逻辑，企业进行初始投资是预期未来会正的现金流，也就是所谓的positive incremental cash flow。
http://www.answers.com/topic/incremental-cash-flow

增量现金流反映的是一个流量量纲，并且并不一定都是positive。project的初始投资就是一个negative cash flow，增加负的就是减少。
这不是很难理解。
您说混淆，是同什么混淆呢？现金流还是income？还是return？

应该是指直接影响投资的现金流.
will this cash flow occur only if we accept the project? no matter it is positive or negative
这样沉没成本应该不算增量现金流吧？