E Emanuel Feru

Experimental validation of a dynamic waste heat recovery system model for control purposes

This paper presents the identification and validation of a dynamic Waste Heat Recovery (WHR) system model. Driven by upcoming CO2 emission targets and increasing fuel costs, engine exhaust gas heat utilization has recently attracted much attention to improve fuel efficiency, especially for heavy-duty automotive applications. In this study, we focus on a Euro-VI heavy-duty diesel engine, which is equipped with a Waste Heat Recovery system based on an Organic Rankine Cycle. The applied model, which combines first principle modelling with stationary component models, covers the two-phase flow behavior and the effect of control inputs. Furthermore, it describes the interaction with the engine on both gas and drivetrain side. Using engine dynamometer measurements, an optimal fit of unknown model parameters is determined for stationary operating points. From model validation, it is concluded that the identified model shows good accuracy in steady-state and can reasonably capture the most important dynamics over a wide range of operating conditions. The resulting real-time model is suitable for model-based control. Copyright

Heat exchanger modeling and identification for control of Waste Heat Recovery systems in diesel engines

To meet future CO2 emission targets, Waste Heat Recovery systems have recently attracted much attention for automotive applications, especially for long haul trucks. This paper focuses on the development of a dynamic counter-flow heat exchanger model for control purposes. The model captures the dynamic phenomena of two-phase fluid flow using the mass and energy balance equations. While most of the studies use chemical libraries to retrieve the working fluid properties, in this model mathematical equations are derived. Compared to other evaporator models, the proposed model is validated on data from a complete engine platform. Experiments are done on a state-of-the-art Euro-VI heavy-duty diesel engine, which is equipped with a Waste Heat Recovery system. For transient conditions over a wide range of operating points, simulation results show good agreement in comparison with experimental data. This makes the model suitable for real-time simulations, diagnostics and control algorithm designs.

Model predictive control of a waste heat recovery system for automotive diesel engines

In this paper, a switching Model Predictive Control strategy is designed for an automotive Waste Heat Recovery system with two parallel evaporators. The objective is to maximize Waste Heat Recovery system output power, while satisfying safe operation under highly dynamic disturbances from the engine. Safe system operation is associated with vapor state after the evaporators. The closed-loop performance of the Model Predictive Control strategy is demonstrated on a high-fidelity validated Waste Heat Recovery system model subject to realistic disturbances from an Euro VI heavy-duty diesel engine. The simulation results, based on a World Harmonized Transient Cycle, demonstrate that the proposed control strategy outperforms a classical PI control strategy in terms of safety and relative average power, up to 15% and 3%, respectively.

Lyapunov-based constrained engine torque control using electronic throttle and variable cam timing

In this paper, predictive control of a spark ignition engine equipped with an electronic throttle and a variable cam timing actuator is considered. The objective is to adjust the throttle angle and the engine cam timing in order to reduce the exhaust gas emissions while maintaining fast and monotonic transient engine torque response. To this end, using a mean-value nonlinear model for the air intake system of the engine, a receding horizon control scheme based on a flexible control Lyapunov function is developed. The proposed control scheme can adjust the throttle plate angle and the cam timing to provide a fast and monotonic air flow response into the engine cylinders, while explicitly taking into account constraints. Compared to a previous parameter governor controller, the simulation results show that the proposed solution provides better performance in terms of settling time. Moreover, the computational complexity of the algorithm is compatible with current electronic control units, despite using a full nonlinear model.

Control of a Waste Heat Recovery system with decoupled expander for improved diesel engine efficiency

In this paper, a switching Model Predictive Control strategy is proposed for a Waste Heat Recovery system in heavy-duty automotive application. The objective is to maximize the WHR system output power while satisfying the output constraints under highly dynamic engine variations. For control design, a WHR system architecture with the expander and pumps decoupled from the engine is considered. Compared to a WHR system with the expander coupled to the engine, up to 29% more output power is obtained for the considered design. This holds for both steady state and highly dynamic engine conditions. The simulation results are obtained using a validated high-fidelity WHR system model with realistic disturbances from a Euro VI heavy-duty diesel engine.

Towards constrained optimal control of spark-ignition engines

In this paper, the torque control problem for spark-ignition engines is considered. The objective is to provide good output torque tracking with minimum fuel consumption, while avoiding engine knock and misfire. To this end, three control strategies are proposed: a feed-forward controller with recalibrated engine maps, a PI control scheme and a model predictive controller. For the model predictive control strategy, a simplified air-path engine model is developed based on the Wiener model structure. The proposed controllers are shown to provide safe engine operation by avoiding engine knock and misfire. The performance of each control strategy is evaluated over a specific driving cycle and compared with a baseline control strategy. Simulation results show up to 40% performance improvement for the model predictive control strategy as compared to the baseline strategy.

Towards model-based control of RCCI-CDF mode-switching in dual fuel engines

The operation of a dual fuel combustion engine using combustion mode-switching offers the benefit of higher thermal efficiency compared to single-mode operation. For various fuel combinations, the engine research community has shown that running dual fuel engines in Reactivity Controlled Compression Ignition (RCCI) mode, is a feasible way to further improve thermal efficiency compared to Conventional Dual Fuel (CDF) operation of the same engine. In RCCI combustion, also ultra-low engine-out NOx and soot emissions have been reported. Depending on available hardware, however, stable RCCI combustion is limited to a certain load range and operating conditions. Therefore, mode-switching is a promising way to implement RCCI in practice on short term. In this paper, a model-based development approach for a dual fuel mode-switching controller is presented. Simulation results demonstrate the potential of this controller for a heavyduty engine running on natural gas and diesel. An existing control-oriented engine model is extended with a new CDF model to simulate both CDF and RCCI operation. This model shows good agreement with experimental data. As a first step towards model-based control development, this extended model is used for system analysis to understand the switching behavior and to design a coordinated air-fuel path controller. This closed-loop controller combines static decoupling with next-cycle CA50-IMEP-Blend Ratio control. For a modeswitching sequence in a low load operating point, the closedloop controlled engine demonstrates stable behavior and good reference tracking. The paper concludes with an outlook on necessary steps to bring model-based control strategies for dual fuel mode-switching in a multi-cylinder engine on the road.