Numerical study of the substitutional diesel fuel energy in a dual fuel diesel-LPG engine with two direct injectors per cylinder

- Two DI injectors diesel-LPG permits diesel-like efficiencies.
- High loads pre and pilot diesel energy is below 5%.
- Low loads pre and pilot diesel energy drastically increases.
- Significant diesel energy only needed at low speeds and loads.

The paper proposes a numerical study of the operation of a dual fuel diesel-Liquefied Petroleum Gas (LPG) engine featuring direct injection (DI) of both the diesel and the LPG with two separate injectors per cylinder. Aim of the study is the determination of the pilot/pre diesel fuel energy needed to operate the engine diesel-like in terms of combustion with a main injection of LPG. Computational results are proposed over the full range of speeds and loads for a 1.6 l high speed direct injection (HSDI) diesel engine. The engine is modified to accept the direct injection of the LPG fuel through the adoption of a second direct injector per cylinder. Only the opportunity of injecting the main LPG after the pilot/pre diesel injections is considered in the study. However, more complex strategies are certainly possible. The results demonstrate the opportunity to achieve diesel-like fuel conversion efficiency and torque and power outputs while replacing the most part of the diesel energy - up to 95% at medium - high loads - with the more environmentally friendly LPG. This replacement reduces the pollutants' emissions and improves the energy mix of transportation fuels.