Integrated energy and emission management for diesel engines with waste heat recovery using dynamic models

Rankine-cycle Waste Heat Recovery (WHR) systems are promising solutions to reduce fuel consumption for trucks. Due to coupling between engine and WHR system, control of these complex systems is challenging. This study presents an integrated energy and emission management strategy for an Euro-VI Diesel engine with WHR system. This Integrated Powertrain Control (IPC) strategy optimizes the CO2-NOx trade-off by minimizing online the operational costs associated with fuel and AdBlue consumption. Contrary to other control studies, the proposed control strategy optimizes overall engine-aftertreatment-WHR system performance and deals with emission constraints. From simulations, the potential of this IPC strategy is demonstrated over a World Harmonized Transient Cycle (WHTC) using a high- fidelity simulation model. These results are compared with a state-of-the-art baseline engine control strategy. By applying the IPC strategy, an additional 2.6% CO2 reduction is achieved compare to the baseline strategy, while meeting the tailpipe NOx emission limit. In addition, the proposed low-level WHR controller is shown to deal with the cold start challenges

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.\u3cbr/\u3e\u3cbr/\u3eIn 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 heavy-duty 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 mode-switching sequence in a low load operating point, the closed-loop 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.\u3cbr/\u3

Two-phase plate-fin heat exchanger modeling for waste heat recovery systems in diesel engines

This paper presents the modeling and model validation for a modular two-phase heat exchanger that recovers energy in heavy-duty diesel engines. The model is developed for temperature and vapor quality prediction and for control design of the waste heat recovery system. In the studied waste heat recovery system, energy is recovered from both the exhaust gas recirculation line and the main exhaust line. Due to the similar design of these two heat exchangers, only the exhaust gas recirculation heat exchanger model is presented in this paper. Based on mass and energy conservation principles, the model describes the dynamics of two-phase fluid flow. Compared to other studies, the model is able to capture multiple phase transitions along the fluid flow by combining finite difference approach with moving boundary approaches. The developed model has low computational complexity, which makes it suitable for control design and real-time implementation. To validate the model, experiments are performed on a state-of-the-art Euro-VI heavy-duty diesel engine equipped with the waste heat recovery system. Simulation results show good accuracy, over the complete engine operating range, with average error below 4%. This is demonstrated on transitions between stationary operating points and on a dynamic response to a standard world harmonized transient cycle for both cold-start and hot-start conditions

Model-based control development for future Diesel engines

Heavy duty diesel vehicles compliant with current Euro VI/EPA13 emission limits employ aftertreatment systems based on DOC/DPF technology for soot and particulate matter reduction and SCR catalysts with urea dosing for NO x reduction. Traditionally, the majority of the control systems used for urea dosing are map based. However, increasing system complexity combined with real-world performance requirements are a strong motivation to switch to a model-based control approach. Firstly, this article describes a model-based design approach for aftertreatment control development. Focus is on urea dosing control for Euro VI level SCR systems. To achieve the legal emissions limits, including in-service conformity over the vehicle lifetime, advanced model-based control strategies enable maximal NO x conversion in combination with minimum ammonia slip, while ensuring robustness against real-life disturbances. Simulation and experimental results of the control system are presented, which demonstrate the performance and robustness properties. Following this model-based approach, a concept study is performed to explore aftertreatment and control technologies to achieve ultra-low NO x emissions as will be imposed by regulatory bodies in the near future. It is shown that aftertreatment concepts with Passive NO x Adsorber and SCR on DPF are most promising. To optimize overall engine-aftertreatment performance, the modelbased control approach is extended towards Integrated Emission Management(IEM). Based on the actual system state, this supervisory controller minimizes operating costs at each instant in time under all operating conditions. This is key for costoptimal and robust performance

Temperature control of evaporators in automotive waste heat recovery systems

his paper presents a control strategy for the steam generation process in automotive waste heat recovery systems that are based on the subcritical Rankine cycle. The central question is how to regulate the flow of water into the evaporator such that dry steam is generated at its outlet, subject to large variations in the heat input. Tight control of this process increases the amount of recovered energy while ensuring safe system operation. The method consists of inversion-based feedforward combined with output feedback on the temperature of the evaporator, which is estimated using exhaust gas measurements. As this method does not require a high fidelity evaporator model, it is easy to implement. It is demonstrated on an experimental setup, where the exhaust flow is imitated by electrically heated air. On an automotive driving cycle, steam was generated reliably with a superheating temperature of 10-20 [K]