Virtual Multi-Cylinder Engine. Experimental and simulation data "in loop" towards a "virtual multi-cylinder engine" for pre-mixed hydrogen combustion

Abstract

This project introduces an integrated methodology and tool set that couples experimental data from a single-cylinder engine (SCE) with a 0D/1D Three-Pressure- Analysis (TPA) model and a multi-cylinder engine (MCE) simulation in GT-Suite. The system developed utilizes measured data from a SCE and uses this to compute an apparent burn rate in a TPA model. This apparent burn rate, along with other operational data is extracted from the SCE and imposed onto a 0D/1D MCE simulation environment where the feedback is a set of boundary conditions corresponding to the inlet and exhaust manifold of the MCE. These boundary conditions are then used to adjust actuators on the SCE - enabling the continuation of a closed loop system until boundary condition convergence criteria have been met.

This concept addressed the two main shortcomings of SCE testing and 0D/1D simulation, respectively. In SCE testing, the entire engine system is decoupled, and each subsystem can be controlled independently for a specific load point. This implies that only steady state operation is possible, while the data that is collected is high fidelity measurement directly from the engine. A 0D/1D MCE simulation can model the system-level engine response, however in the context of premixed hydrogen engines, the combustion models are not mature enough to accurately represent in-cylinder combustion events.

The integration of a TPA-derived burn rate into the 0D/1D MCE model allowed the gap to be bridged between simplified simulation and experimental reality. A symbiotic looped workflow was established, and this paper shows that there exists potential to optimize the design quality and time of high-performance MCE concepts for future powertrain development.

A data sampling and averaging study was conducted to understand how the output of the simulation components reacted to cyclic variations. The study showed that key performance parameters are not significantly affected by the sample size when compared to a 200-cycle average; however are more sensitive to the sampling window - suggesting a sensitivity to cyclic variations. A minimum of 50 averaged cycles is required for accurate system results.

Furthermore, the output of an initial loop iteration of the ’virtual MCE’ simulation tool is compared to a similar experimental MCE as a means to understand the system’s initial conditions and validate the concept. This investigation was inconclusive, and hardware discrepancies were found to be evident in the test setups.

The continuation of loop iterations was halted by the lack of access to a dedicated SCE test bed. The initial iteration found absolute inlet manifold boundary condition errors of 7.14% for pressure, and 82.4% for temperature. While the absolute exhaust manifold back pressure error was found to be 3.98%.

The overarching research question was found to be inconclusive. However, this report sets the foundation for future work and discusses how further research can be conducted to aid in realizing its successful outcome. This thesis offers a set of recommendations for continued progression in realizing this as an industry tool. The thesis was therefore written in a manner to aid in future work and can be used as reference for configuring simulation models, addressing errors in future studies and is useful reference for relevant theory.