Design and assembly of a throttle for an HCCI engine

Abstract

This report is about the inclusion of a throttle in the HCCI engine that is being developed in KTH. This must control the power and working mode of the engine. With an air throttle it is possible to change the engine from spark mode to HCCI mode. During this project, many other aspects have been improved, such as air and oil pump. In order to take conclusions it is necessary to analyse some of the engine’s data that was obtained during the development, such as cylinder pressure, injection pulse and ignition pulse. It was analysed different moments of engine’s development using different components, to achieve different performances in each case. To run the engine in HCCI mode it is necessary to have a Lambda value between 1.5 and 2. Even if the results show that is better to run in “Pump+Throttle+Intake”, the pump has to overwork due to additional throttle resistance. For that reason it is necessary to work in “Throttle+Pump+Intake” in the future. But for that it is necessary to reduce the injection timing, for that reason it is important to increase the air flow. At the last configuration tested, it was not possible to get more air from actual pump, within the pump rotational speed limits (max. 6000 rpm). Working over these speed limits, caused pump overheating and decreased engine's performance. Then it is recommended to use a more powerful pump. However, another file has been developed to know a little bit more about the behaviour of the engine. This file is called Task and gives to the user the possibility to know about the compression ratio, position of the pistons, port opening/closing, velocities and much more values of the engine just changing some values on it.