Optimal Sizing of Waste Heat Recovery Systems for Dynamic Engine Conditions

In this study, a methodology for optimal sizing of waste heat recovery (WHR) systems is presented. It deals with dynamic engine conditions. This study focuses on Euro-VI truck applications with a mechanically coupled Organic Rankine Cycle-based WHR system. An alternating optimization architecture is developed for optimal system sizing and control of the WHR system. The sizing problem is formulated as a fuel consumption and system cost optimization problem using a newly developed, scalable WHR system model. Constraints related to safe WHR operation and system mass are included in this methodology. The components scaled in this study are the expander and the EGR and exhaust gas evaporators. The WHR system size is optimized over a hot World Harmonized Transient Cycle (WHTC), which consists of urban, rural and highway driving conditions. The optimal component sizes are found to vary for these different driving conditions. By implementing a switching model predictive control (MPC) strategy on the optimally sized WHR system, its performance is validated. The net fuel consumption is found to be reduced by 1.1% as compared to the originally sized WHR system over the total WHTC

From hit to vial: Precision discovery and development of an imidazopyrimidine TLR7/8 agonist adjuvant formulation

Vaccination can help prevent infection and can also be used to treat cancer, allergy, and potentially even drug overdose. Adjuvants enhance vaccine responses, but currently, the path to their advancement and development is incremental. We used a phenotypic small-molecule screen using THP-1 cells to identify nuclear factor-κB (NF-κB)–activating molecules followed by counterscreening lead target libraries with a quantitative tumor necrosis factor immunoassay using primary human peripheral blood mononuclear cells. Screening on primary cells identified an imidazopyrimidine, dubbed PVP-037. Moreover, while PVP-037 did not overtly activate THP-1 cells, it demonstrated broad innate immune activation, including NF-κB and cytokine induction from primary human leukocytes in vitro as well as enhancement of influenza and SARS-CoV-2 antigen-specific humoral responses in mice. Several de novo synthesis structural enhancements iteratively improved PVP-037’s in vitro efficacy, potency, species-specific activity, and in vivo adjuvanticity. Overall, we identified imidazopyrimidine Toll-like receptor-7/8 adjuvants that act in synergy with oil-in-water emulsion to enhance immune responses

Age‐related changes to the satellite cell niche are associated with reduced activation following exercise

Skeletal muscle satellite cell (SC) function and responsiveness is regulated, in part, through interactions within the niche, in which they reside. Evidence suggests that structural changes occur in the SC niche as a function of aging. In the present study, we investigated the impact of aging on SC niche properties. Muscle biopsies were obtained from the vastus lateralis of healthy young (YM; 21 ± 1 yr; n = 10) and older men (OM; 68 ± 1 yr; n = 16) at rest. A separate group of OM performed a single bout of resistance exercise and additional muscle biopsies were taken 24 and 48 hours post‐exercise; this was performed before and following 12 wks of combined exercise training (OM‐Ex; 73 ± 1; n = 24). Muscle SC niche measurements were assessed using high resolution immunofluorescent confocal microscopy. Type II SC niche laminin thickness was greater in OM (1.86 ± 0.06 µm) as compared to YM (1.55 ± 0.09 µm, P < .05). The percentage of type II‐associated SC that were completely surrounded by laminin was greater in OM (13.6%±4.2%) as compared to YM (3.5%±1.5%; P < .05). In non‐surrounded SC, the proportion of active MyoD+/Pax7+ SC were higher compared to surrounded SC (P < .05) following a single bout of exercise. This “incarceration” of the SC niche by laminin appears with aging and may inhibit SC activation in response to exercise

Dynamic model of supercritical Organic Rankine Cycle waste heat recovery system for internal combustion engine

The supercritical Organic Rankine Cycle (ORC) for the Waste Heat Recovery (WHR) from Internal Combustion (IC) engines has been a growing research area in recent years, driven by the aim to enhance the thermal efficiency of the ORC and engine. Simulation of a supercritical ORC-WHR system before a real-time application is important as high pressure in the system may lead to concerns about safety and availability of components. In the ORC-WHR system, the evaporator is the main contributor to thermal inertia of the system and is considered to be the critical component since the heat transfer of this device influences the efficiency of the system. Since the thermo-physical properties of the fluid at supercritical pressures are dependent on temperature, it is necessary to consider the variations in properties of the working fluid. The wellknown Finite Volume (FV) discretization method is generally used to take those property changes into account. However, a FV model of the evaporator in steady state condition cannot be used to predict the thermal inertia of the cycle when it is subjected to transient heat sources. In this paper, a dynamic FV model of the evaporator has been developed and integrated with other components in the ORC-WHR system. The stability and transient responses along with the performance of the ORC-WHR system for the transient heat source are investigated and are also included in this paper

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 misre. 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 simplied 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 misre. The performance of each control strategy is evaluated over a specic 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

Integrated energy and emission management for heavy-duty diesel engines with waste heat recovery system

Rankine-cycleWasteHeatRecovery (WHR)systems are promising solutions to reduce fuel consumption for trucks. Due to coupling between engine andWHR system, control of these complex systems is challenging. This study presents an integrated energy and emission management strategy for an Euro-VI Diesel engine withWHRsystem. 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 systemperformance and dealswith emission constraints. Fromsimulations, the potential of this IPC strategy is demonstrated over a World Harmonized Transient Cycle (WHTC) using a highfidelity simulationmodel. 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 tailpipeNOx emission limit. In addition, the proposed low-levelWHR 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. 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 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

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

Modeling and control of a parallel waste heat recovery system for Euro-VI heavy-duty diesel engines

This paper presents the modeling and control of a waste heat recovery systemfor a Euro-VI heavy-duty truck engine. The considered waste heat recovery system consists of two parallel evaporators with expander and pumps mechanically coupled to the engine crankshaft. Compared to previous work, the waste heat recovery system modeling is improved by including evaporator models that combine the finite difference modeling approach with a moving boundary one. Over a specific cycle, the steady-state and dynamic temperature prediction accuracy improved on average by 2% and 7%. From a control design perspective, the objective is to maximize the waste heat recovery system output power.However, for safe system operation, the vapor state needs to be maintained before the expander under highly dynamic engine disturbances. To achieve this, a switching model predictive control strategy is developed. The proposed control strategy performance is demonstrated using the high-fidelity waste heat recovery system model subject to measured disturbances from an Euro-VI heavy-duty diesel engine. Simulations are performed usinga cold-start World Harmonized Transient cycle that covers typical urban, rural and highway driving conditions. The model predictive control strategy provides 15% more time in vaporand recovered thermal energy than a classical proportional-integral (PI) control strategy. In the case that the model is accurately known, the proposed control strategy performance can be improved by 10% in terms of time in vapor and recovered thermal energy. This is demonstrated with an offline nonlinear model predictive control strategy