PRIN 2022 CALL. DECREE NO. 104 OF 2 FEBRUARY 2022
PROJECT TITLE: Digital Twin Technology for the Development of LP-DI Hydrogen engine for heavy-duty applications (DHYCE-HD)
CODICE CUP: D53D23004150006
Politecnico di Bari Budget: € 148,702
Research Unit Coordinator: Prof. Pietro De Palma
Other Research Units: Polytechnic University of Milan (Prof. Gianluca D’Errico)
Brief project description
The DHYCE-HD project (Digital Twin Technology for the Development of LP-DI Hydrogen Engine for Heavy-Duty Applications) was conceived to accelerate the transition towards zero-emission propulsion systems through the development of an advanced numerical framework dedicated to hydrogen-fueled internal combustion engines.
The project is divided into distinct Work Packages (WPs), which have fostered collaboration between the two research groups of the Polytechnic University of Milan and the Polytechnic University of Bari. The PoliMI group is primarily responsible for developing a reliable numerical approach that will form the backbone of the Digital Twin. The research activities have focused on the development and integration of advanced 1D and 3D CFD simulation tools, in particular the Gasdyn and LibICE codes. These tools have been enhanced to address the distinctive and complex characteristics of hydrogen combustion, such as its extremely high flame speed, low ignition energy, and wide flammability range.
The Polytechnic University of Bari is responsible for implementing non-oscillatory numerical methods (WENO). These high-order accuracy schemes are essential for capturing complex shock waves and discontinuities typical of high-speed hydrogen jets, significantly improving the robustness and accuracy of the simulations.
The main research activity consists of the parallel study of a heavy-duty engine equipped with direct hydrogen injection (H₂-DI). This analysis is conducted at several operating points, comparing established modeling approaches with the newly developed methods. Finally, the entire numerical framework is subjected to a rigorous validation process using experimental data available in the literature, in order to ensure that the predictive capabilities of the DHYCE-HD platform are accurate and reliable for industrial applications.
Objectives
Identification of the main advantages and disadvantages of a low-pressure-direct injection (LP-DI) hydrogen engine for heavy-duty applications.
Strengthening of know-how relating to hydrogen engine technology, with particular reference to: a) the complex physical processes involved in the direct injection of hydrogen into engines and the subsequent formation of the mixture; b) the effects of H₂ injection pressure and flow rate, as well as injector position and geometry, on engine efficiency and emissions; c) the turbulent combustion of premixed air–hydrogen mixtures, including stratified conditions, with the determination of the lean combustion limit and knocking risk; d) the formation of nitrogen oxides inside the cylinder and strategies for minimising them;
Development of fast and accurate CFD methodologies for application to direct-injection (DI) hydrogen engines, based on open-source technologies accessible for future research activities;
Definition of a virtual LP-DI hydrogen engine configuration for heavy-duty applications, characterized by high efficiency and low NOx emissions.
Main expected results:
Preparation of an up-to-date report on the state of the art regarding the use of hydrogen as a fuel in internal combustion engines;
Definition of correlations for laminar flame speed to be used in CFD codes and 1D models;
Acquisition of knowledge regarding the fundamental aspects of hydrogen injection, mixing, and combustion, including the assessment of high-accuracy numerical schemes;
Definition of an accurate numerical methodology specifically developed for hydrogen LP-DI engines;
Evaluation of the performance, fuel consumption and emissions of a turbocharged and optimized virtual hydrogen LP-DI engine under both steady-state and transient operating conditions;
Evaluation of the influence of the start of injection timing and ignition advance on pre-ignition and NOx emissions under lean-combustion conditions;
Definition of a digital twin of the combustion chamber of a hydrogen LP-DI engine, demonstrating the feasibility of breakthrough performance in terms of efficiency and emissions using a carbon-free fuel;
Production of detailed technical information for the development of a “green” hydrogen engine, with significant economic and social impacts in the mobility and energy sectors in Europe and Italy, within the context of the ecological transition towards a sustainable economy.
Results obtained
Significant results were achieved by the research unit (RU) of the Polytechnic University of Bari, which developed and validated high-fidelity numerical methodologies for hydrogen injection and mixing. In particular, the implementation of high-order WENO schemes enabled the accurate resolution of underexpanded hydrogen jets, capturing complex shock structures, hydrogen-jet instabilities and mixing dynamics with greater accuracy than conventional schemes. These developments represent a significant advancement in addressing one of the main challenges of direct-injection hydrogen engines, namely the rapid and efficient air–fuel mixing under highly compressible-flow conditions.
In parallel, analytical correlations were developed for laminar flame speed, together with tabulated kinetic approaches for autoignition, providing robust and computationally efficient models for predicting combustion and knocking in both 1D and 3D simulations.
The validated numerical framework was extended to three-dimensional CFD simulations of the entire engine cycle. A reliable 1D–3D coupling methodology was also developed and validated against experimental data from a hydrogen-fueled engine, demonstrating its ability to accurately reproduce in-cylinder pressure evolution, flow structures and turbulence characteristics. Detailed analyses of mixture formation and combustion processes were also conducted for hydrogen-fueled configurations.
The WENO methodology was successfully applied to full 3D simulations of the internal combustion engine under consideration. Three operating conditions were analysed, characterised by different hydrogen injection start-of-injection timings (SOI = 540, 630 and 660 CAD) at constant injection pressure. This activity enabled a direct assessment of the impact of high-order numerical schemes on the prediction of injection, mixing and in-cylinder flow evolution phenomena under realistic engine operating conditions. The results confirmed the greater ability of WENO-based approaches to capture sharp gradients, shock-wave interactions and stratification effects, thereby improving the predictive reliability of CFD simulations and directly contributing to the development of a high-fidelity digital twin.
Overall, these results provide a sound scientific and technological basis for future developments in the field of hydrogen internal combustion engines and contribute to the advancement of zero-carbon-emission propulsion technologies for the heavy-duty sector.
