Functional Requirements to Exceed the 100 kW/l Milestone for High Power Density Automotive Diesel Engines

The paper describes the challenges and results achieved in developing a new high-speed Diesel combustion system capable of exceeding the imaginative threshold of 100 kW/l. High-performance, state-of-art prototype components from automotive diesel technology were provided in order to set-up a single-cylinder research engine demonstrator. Key design parameters were identified in terms boost, engine speed, fuel injection pressure and injector nozzle flow rates. In this regard, an advanced piezo injection system capable of 3000 bar of maximum injection pressure was selected, coupled to a robust base engine featuring ?-shaped combustion bowl and low swirl intake ports. The matching among the above-described elements has been thoroughly examined and experimentally parameterized. The tests confirmed the benefits of the employment of very high fuel injection pressures as a way to decouple the trade-off between an excellent power rating and emissions / NVH / CO2 at part load, whose combination truly defines the leading edge of modern diesel engines for automotive application. The paper also discusses the system sensitivity to the boundary conditions, of the charging and exhaust systems, and develops a balanced set of targets for the entire system based on thermo-structural, fluid-dynamics and efficiency considerations. This would represent, in the authors' view, the 'recipe' for the next generation of premium diesel engines for automotive application