Impact of injection strategy and GTL fuels on combustion process and performance under diesel engine start

- Cycle to cycle engine start has been studied under hot and relative cold thermal conditions.
- Diesel and paraffinic fuels have been tested under engine start and both thermal conditions.
- Injection strategy has been modified under engine start with three fuels tested.
- Injection strategy and cetane number have impact on indicated efficiency under engine start.
- Paraffinic fuels have impact on efficiency under start of engines with delayed injection strategy.

The impact of three fuels (a diesel fuel without biodiesel and two Fischer Tropsch low temperature gas to liquid paraffinic fuels from natural gas) on the indicated engine performance and the timing of the combustion process under the engine start has been studied by means of cycle to cycle thermodynamic diagnosis during the first 5-6 cycles along the whole starting process. The study was carried out varying the beginning of the start of pre-injections at different thermal conditions of the engine. In all cases exhaust gas recirculation valve was closed. Both, the rate of apparent heat release and the indicated efficiency, were mainly used as comparative parameters. The work was carried out on a Nissan Qashqai light duty diesel vehicle equipped with a Kistler Kibox thermodynamic analyzer. Piezoelectric in-cylinder pressure sensors were mounted on each engine cylinder. This work demonstrates the relevance of fuel used during the engine tuning. The efficiency of GTL fuels was better when delayed strategy was tested. Compared to diesel fuel, there is potential for improving the benefits of GTL fuels on engine performance.