When writing an academic paper (or for that matter a dissertation or thesis) you must be careful to understand the roles of the units. For a detailed discussion see the post “How (not) to write an abstract“. I agree wholeheartedly with the sentiments.
The essence? Abstracts are concise summaries for experts; introductions are for a wider audience.
Conclusions are more than just the “results”, it also answers the “so what?” question.
Unfortunately bad practice gets promoted by conferences first expecting an abstract and then weeks, sometimes months later expecting the full paper. When preparing a paper that way be careful, what you submit probably is closer to an introduction than an abstract.
Papers must report on research, but when you write an abstract first you may commit to a paper when results are not available. How do you write a paper without having a “story” to tell? Only once you have your “story” figured out can you write a really good abstract, introduction and conclusion.