Fuel is a substance that is burned to produce energy. In the context of the article, clean-fuel work refers to the development and use of alternative fuels that produce fewer emissions and are more environmentally friendly. This is likely in response to growing concerns about climate change and the need for more sustainable energy sources.
The article does not provide detailed information on how fuel works in general, but it does discuss the impact of new defense deals and clean-fuel work on investors in KBR, a company that provides services to the energy and defense industries. KBR is likely involved in the development and implementation of clean-fuel technologies, but the article does not provide specific information on the technical aspects of fuel.
The article focuses on the business and financial implications of clean-fuel work and new defense deals for KBR investors, rather than the technical details of fuel itself. As such, it does not provide a comprehensive explanation of how fuel works.