Vincenzo Mulone

Torque Setpoint Tracking for Parallel Hybrid Electric Vehicles Using Dynamic Input Allocation

This paper addresses the coordinated control of the internal combustion engine and the electric motor in a parallel hybrid electric vehicle, when both of them are running. In deciding how much torque each motor contributes, both long term energy oriented and short term drivability goals must be considered. The first contribution in this paper consists of proposing an architecture in which three main functional blocks are present, namely a steady-state performance generator, providing an energy oriented torque contribution, a transient performance generator providing a drivability oriented torque contribution, and a dynamic input allocator blending the outputs of the other two blocks in such a way as to satisfy both the short and the long term goals. The second contribution consists in showing how the input allocator must be designed. The other two blocks can be designed following any of several recipes already described in the literature. Experimental validation of the proposed approach confirms the relevance of accounting for the different motor dynamics in the allocator design.

Numerical-Experimental Comparison of the Performance of a Partially Stratified Charge Natural Gas Fuelled Engine

Compressed natural gas (CNG) has great potential as an alternative fuel for vehicle engines, and can reduce emissions and improve fuel economy. A single cylinder research engine has been modified to enable direct injection of a small quantity of fuel near the spark plug, independently of an overall lean homogeneous charge. Thus a partially stratified charge is formed within the chamber, which allows significant extension of the lean limit of combustion. This results in an improvement in specific fuel consumption. Numerical simulation also plays an important role in the development of such technological solutions. 3D simulations, in particular, are desirable to provide complete information about thermal and fluid dynamical fields within the chamber. In particular, among the developed numerical tools linked to the KIVA-3V code, special attention was dedicated to the formulation of the combustion model (CFM) turbulent combustion model based on the flamelet hypothesis), to adequately model non-homogeneities and lean mixture compositions. In this paper an optimization procedure is assessed, with the ultimate goal of designing combustion chambers properly devoted to be operated under lean (homogeneous and PSC) mixture conditions. The results related to the procedure definition and to its experimental validation are presented. Experimental and numerical data have been compared in terms of pressure cycles and heat release rate profiles. The overall results are encouraging, taking into special account the difficulty to reliably predict the key performance parameters without any “tuning interventions”, even when mixture richness and homogeneity were varied.Copyright

Heat and Mass Transfer Evaluation in the Channels of an Automotive Catalytic Converter by Detailed Fluid-Dynamic and Chemical Simulation

The role of numerical simulation to drive the catalytic converter development becomes more important as more efficient spark ignition engines after-treatment devices are required. The use of simplified approaches using rather simple correlations for heat and mass transfer in a channel has been widely used to obtain computational simplicity and sufficient accuracy. However, these approaches always require specific experimental tuning so reducing their predictive capabilities. The feasibility of a computational fluid dynamics three-dimensional (3D) model coupled to a surface chemistry solver is evaluated in this paper as a tool to increase model predictivity then allowing the detailed study of the performance of a catalytic converter under widely varying operating conditions. The model is based on FLUENT to solve the steady-state 3D transport of mass, momentum and energy for a gas mixture channel flow, and it is coupled to a powerful surface chemistry tool (CANTERA). Checked with respect to literature available experimental data, this approach has proved its predictive capabilities not requiring an ad hoc tuning of the parameter set. Heat and mass transfer characteristics of channels with different section shapes (sinusoidal, hexagonal, and squared) have then been analyzed. Results mainly indicate that a significant influence of operating temperature can be observed on Nusselt and Sherwood profiles and that traditional correlations, as well as the use of heat/mass transfer analogy, may give remarkable errors (up to 30% along one-third of the whole channel during light-off conditions) in the evaluation of the converter performance. The proposed approach represents an appropriate tool to generate local heat and mass transfer correlations for less accurate, but more comprehensive, 1D models, either directly during the calculation or off-line, to build a proper data base.

Numerical and Experimental Characterization of a Natural Gas Engine With Partially Stratified Charge Spark Ignition

This paper outlines the development of a comprehensive numerical framework for the partially stratified charge (PSC) lean-burn natural gas engine. A 3D model of the engine was implemented to represent fluid motion and combustion. The spark ignition model was based on the works of Herweg and Maly (1992, “A Fundamental Model for Flame Kernel Formation in SI Engines,” SAE Technical Publication, Paper No. 922243) and Tan and Reitz (2006, “An Ignition and Combustion Model Based on the Level-Set Method for Spark Ignition Engine Multidimensional Modeling,” Combust. Flame, 145, pp. 1–15). The EDC model (Ertesvag and Magnussen, 2000, “The Eddy Dissipation Turbulence Energy Cascade Model,” Combust. Sci. Technol., 159, pp. 213–235) with a two-step mechanism was used to model natural gas turbulent combustion process. An open geometry simulation strategy was adopted to account for intake-exhaust gas and valve movements. Each simulation was executed for multiple cycles to produce a representative residual gas fraction. The numerical results were compared with the experimental data obtained on the Ricardo Hydra single cylinder research engine for both homogeneous and PSC cases and they were found to be in excellent agreement in pressure trace and heat release rate. The detailed investigation of the numerical data showed the development of an ignitable mixture under PSC cases, allowing stable kernel growth well beyond the lean misfire limit of the bulk mixture. Furthermore, limits on successful ignition can be identified using the ignition model, which exhibited self-similar behavior in terms of flame speed and turbulent fluctuation. It can also be shown that, at ultralean air-fuel ratios, the PSC plume helps replicate the ignition conditions that can be found under stoichiometric operation.

Soot Modeling for Advanced Control of Diesel Engine Aftertreatment

Diesel Particulate Filters (DPFs) are well assessed aftertreatment devices, equipping almost every modern diesel engine on the market to comply with today’s stringent emission standards. However, an accurate estimation of soot loading, which is instrumental to ensuring optimal performance of the whole engine-after-treatment assembly is still a major challenge. In fact, several highly coupled physical-chemical phenomena occur at the same time, and a vast number of engine and exhaust dependent parameters make this task even more daunting. This challenge may be solved with models characterized by different degrees of detail (0-D to 3-D) depending on the specific application. However, the use of real-time, but accurate enough models, may be of primary importance to face with advanced control challenges, such as the integration of the DPF with the engine or other critical aftertreatment components (Selective Catalytic Reduction (SCR) or other NOx control components), or to properly develop model-based OBD sensors. This paper aims at addressing real time DPF modeling issues with special regard to key parameter settings, by using the 1D code ExhAUST (Exhaust Aftertreatment Unified Simulation Tool), developed jointly by the University of Rome Tor Vergata and West Virginia University. ExhAUST is characterized by a novel and unique full analytical treatment of the wall that allows faithful representation with high degree of detail the evolution of soot loading inside the porous matrix. Numerical results are compared with experimental data gathered at West Virginia University (WVU) engine laboratory using a Mack heavy-duty diesel engine coupled to a Johnson Matthey CCRT (DOC, Diesel Oxidation Catalyst+CDPF, Catalyzed DPF) aftertreatment system. To that aim, the engine test bench has been equipped with a DPF weighing setup to track soot load over a specifically developed engine operating procedure. Obtained results indicate that the model is accurate enough to capture soot loading and back pressure histories with regard to different steady state engine operating points, without needing any tuning procedure of the key parameters. Thus, the use of ExhAUST for application to advanced after-treatment control appears promising at this stage.Copyright

Spent coffee enhanced biomethane potential via an integrated hydrothermal carbonization-anaerobic digestion process

This study reports the implications of using spent coffee hydrochar as substrate for anaerobic digestion (AD) processes. Three different spent coffee hydrochars produced at 180, 220 and 250 °C, 1 h residence time, were investigated for their biomethane potential in AD process inoculated with cow manure. Spent coffee hydrochars were characterized in terms of ultimate, proximate and higher heating value (HHV), and their theoretical bio-methane yield evaluated using Boyle-Buswell equation and compared to the experimental values. The results were then analyzed using the modified Gompertz equation to determine the main AD evolution parameters. Different hydrochar properties were related to AD process performances. AD of spent coffee hydrochars produced at 180 °C showed the highest biomethane production rate (46 mL CH4/gVS.d), a biomethane potential of 491 mL/gVS (AD lasting 25 days), and a biomethane gas daily composition of about 70%.

Biomass furnace study via 3D numerical modeling

Purpose – In the recent years the interest toward the use of biomass as a fuel for energy conversion, along with the continuous tightening of regulations, has driven the improvement of accurate design techniques which are required to optimize the combustion process and simultaneously control pollutant emissions. In this paper the use of a 3D Computational Fluid Dynamics approach is analyzed to that aim by means of an application to an existing 50 MW biomass fixed-bed combustion furnace fueled by grape marc. The paper aims to discuss these issues. Design/methodology/approach – The studied furnace is an interesting example of biomass utilization as it may integrate biomass with organic residual by an industrial process. The numerical model has been implemented into an OpenFOAM solver, with an Eulerian-Lagrangian approach. In particular, the fully 3D approach here presented, directly solves for the gas and solid evolution in both the combustion bed and the freeboard. Special care has also been devoted to the...

Dynamic input allocation of torque references for a parallel HEV

A novel strategy for the dynamic managment of the load request for the Internal Combustion Engine (ICE) and the Electrical Motor (EM) in a parallel hybrid vehicle is presented. The goal is the performing of a load splitting between ICE and EM subject to the achievement of good drivability of the vehicle in terms of coherence of the torque supply with the driver request (transient performance) for every load splitting between the two motors (static performance). In particular a dynamic allocation scheme is proposed, which dynamically distribute the power demand among the two propulsion systems, using suitable characterizations of their dynamics. Its stability and convergence properties are formally proven and the effectiveness of the control scheme is illustrated via simulations.

Polymer Electrolyte Fuel Cell Design Based on Three-Dimensional Computational Fluid Dynamics Modeling

An entirely numerical design procedure, based on computational fluid dynamics, is introduced to evaluate the performance of different polymer electrolyte fuel cell layouts and sets of operating conditions for assigned target parameters in terms of performance. The design procedure has been applied to a coflow design, characterized by large active area (500 cm 2 ), moderate temperature (70°C), liquid cooling, and metal supporting. The role of heat transfer between the cell and the cooling system is analyzed to properly address the influence of operating conditions on power density and flooding via a comprehensive parametric analysis.

Thermal-Fluid-Dynamic Simulation of a Proton Exchange Membrane Fuel Cell Using a Hierarchical 3D-1D Approach

The use of proton exchange membrane fuel cells (PEFC) based power trains and stationary systems has been technically demonstrated but is still far from commercial application. Technical development is still required to reach cost and durability targets, and to this aim, modeling and simulation are useful tools to obtain both better understanding of the fundamental occurring processes and to shorten design-associated costs and time. In this paper, a hierarchical 3D-1D approach is proposed, to overcome the deficiencies of a full 1D approach and the characteristic computational costs of a full 3D approach. The polymeric membrane and catalyst layers are represented by a local 1D model, while channels, gas diffusion layers, and solid electrodes are modeled by a full 3D approach. The model capabilities are first investigated with respect to experimental data by means of a full fuel cell simulation; the main chemical, fluid dynamic, and thermal fields are then analyzed in a straight channel configuration. The proposed 3D/1D model is able to accurately represent PEFC specific phenomena and their physical coupling. It could be then successfully applied to both design and development.