Introduction

Background

Objectives


Test facility

Diagnostic techniques


Cross-flow influence

Overall boiling curves

Intermittent cooling efficiency

Heat transfer correlations






 

 
Advances in Intermittent Spray Impact Research

micro nano engineering
   

  Background

Car manufacturers currently face evermore stringent emission levels of average carbon dioxide due to greater awareness expressed by environmental politics since the Kyoto Protocol. Protecting the environment demands cleaner and more efficient engines. This requires a better and accurate knowledge of the thermofluid and combustion phenomena for improving engine technology. A significant part of pollutants emitted to the atmosphere is attributed to the formation of liquid fuel films in interposed surfaces, as well as a defective preparation of the combustible mixture. This is the result of spray impingement.

Our research work on spray impingement has two complementary perspectives:

          i) impact on cold and;
          ii) hot surfaces.

In cold surfaces, most of our work is fundamental research focused on fuel sprays. The interaction between the spray with a stagnant or dynamic surrounding air is considered in the research, in order to characterize the influence of impinging droplets on the events of fuel deposition and secondary atomization.


In hot surfaces, our research work involving fuel sprays is aimed at extending the knowledge of heat transfer processes in intermittent sprays to optimize the fuel/air mixture preparation. However, the analysis performed on heat transfer is not limited to fuel sprays.


One of the most promising thermal management techniques is spray cooling. Most spray cooling systems involve the continuous injection of the cooling liquid. Our research work performed with intermittent fuel sprays led to propose the use of intermittent sprays instead of continuous, as a new technological concept for greater improvements in this cooling technique. Intermittent spray cooling is able to efficiently remove high heat fluxes by proper matching the frequency with the duration of injection and allows introducing intelligent control (e.g. neural networks) for better addressing heterogeneous heat dissipation demands in microprocessor technology.