Real-time capable simulation of diesel combustion processes for HiL applications

Abstract

The complexity of the development processes for advanced diesel engines has significantly increased during the last decades. A further increase is to be expected, due to more restrictive emission legislations and new certification cycles. This trend leads to a higher time exposure at engine test benches, thus resulting in higher costs. To counter this problem, virtual engine development strategies are being increasingly used. To calibrate the complete powertrain and various driving situations, model in the loop and hardware in the loop concepts have become more important. The main effort in this context is the development of very accurate but also real-time capable engine models. Besides the correct modeling of ambient condition and driver behavior, the simulation of the combustion process is a major objective. The main challenge of modeling a diesel combustion process is the description of mixture formation, self-ignition and combustion as precisely as possible. For this purpose, this article introduces a novel combustion simulation approach that is capable of predicting various combustion properties of a diesel process. This includes the calculation of crank angle resolved combustion traces, such as heat release and other thermodynamic in-cylinder states. Furthermore, various combustion characteristics, such as combustion phasing, maximum gradients and engine-out temperature, are available as simulation output. All calculations are based on a physical zero-dimensional heat release model. The resulting reduction of the calibration effort and the improved model robustness are the major benefits in comparison to conventional data-driven combustion models. The calibration parameters directly refer to geometric and thermodynamic properties of a given engine configuration. Main input variables to the model are the fuel injection profile and air path-related states such as exhaust gas recirculation rate and boost pressure. Thus, multiple injection event strategies or novel air path control structures for future engine control concepts can be analyzed.

Transient prediction capabilities of a novel physics-based ignition delay model in multi-pulsed direct injection diesel engines

“…Hence, premixed combustion was assumed for the pilot fuel. 36 A simple heat release model, such as the Wiebe model 13 (equation (A22) in the supplemental material), was used to predict the burnt mass fraction of the pilot injected fuel at the start of main combustion, 37–39 when the main injection starts before the end of the pilot combustion. When the main injection starts after the end of pilot combustion, the pilot fuel is assumed to be burnt completely before the main injection occurs.…”

Combustion rate shaping for flex-fuel applications

“…The quality of the injector model is demonstrated in Figure 13 where injection quantity variation is performed at 1200 bar from 0 to 30 mg for the given injector and the model predicts the hydraulic fuel rate. Injector modelling is based on Bernoulli's equation as stated in Jo¨rg et al 17 and Neumann et al 29 The hydraulic injection profile is predicted from the digitalization model which is then converted into an electric injection profile using an inverted injector model.…”

Symposium for Combustion Control 2016

“…Advanced modeling techniques covering the range from reduced-order to detailed models have been presented by Frommater et al 3 and Pasternak et al 4 Real-time capability has become a key requirement for simulations utilizing Hardware-in-the-Loop environments for the calibration of electronic control units. The paper by Neumann et al 5 shows the potential of a zero-dimensional (0D) model to predict the combustion rate over a wide range of operation conditions of a modern diesel engine. Premixed charge compression ignition is a promising concept to improve the emission behavior of the diesel engine process while maintaining its high efficiency.…”