Abstract 
     Low temperature combustion has been the focus of various studies aiming to reach a cleaner combustion in a Diesel engine respect to pollutant emissions. The different concepts can introduce significant enhancements mainly towards NOX and soot emissions although they also present limitations regarding to engine load and combustion noise.
     Recently, Sandia Institute proposed a new concept for low temperature Diesel combustion (LTC) which presents simultaneous reduction on NOX and soot formation, maintaining the conventional diffusion Diesel combustion characteristics. This new combustion model, at that time developed in a constant volume combustion chamber, consisted in creating a low air temperature and low oxygen concentration environment associated to the use of high injection pressure and micro-orifice nozzle. Furthermore, they were able to achieve reduced adiabatic flame temperature and increase air entrainment upstream the lift-off length, avoiding in this way both NOX and soot formation simultaneously.
      The main objective of this thesis has been transferring this new LTC diffusion combustion technology to a small single-cylinder conventional engine, facing the obstacles that emerge when it is applied to a dynamic mechanism, such as wall impingement, the difficulty to control in-cylinder environment conditions and lift-off length shortening that reduces air entrainment upstream lift-off length. In the first part, the study has looked for reaching strictly-diffusion LTC combustion using two small engines with distinct geometric characteristics and understanding air thermodynamic parameter influences such as oxygen concentration, air density and temperature. Furthermore, the engine has been changed for another with more favorable characteristics, slightly bigger displacement volume and a larger bow in order to reduce wall impingement risk. Eventually, parameters related to engine design and injection system functionality, such as nozzle orifice diameter, orifice number and injection pressure have been explored in order to verify how they could enhance combustion process, with the objective to extend LTC combustion range. Thus, it has been presented the advantages of the best hardware configurations and suggestions for future works
     The results demonstrate this combustion concept potential, obtaining practically zero NOX and soot emissions, with poorly important indicated mean effective pressure penalties. In fact, there are some combustion concept aspects that can be enhanced in order to implement its application to in-production vehicle engine, some of them exposed in this doctorate thesis.