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Mechanical Engineering. 2015;137(12):S2-S6. doi:10.1115/1.2015-Dec-6.
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This article focuses on control-oriented engine modeling and model-based engine control techniques. The engine modeling research is centered on the engine combustion process. Multi-zone, three dimensional computational fluid dynamics (CFD) models, with detailed chemical kinetics are able to precisely describe the thermodynamics, fluid and flow dynamics, heat transfer, and pollutant formation of the combustion process. The simplified one-dimensional combustion models have also been implemented into commercial codes such as GT-Power and Wave. However, these high fidelity models cannot be used for model-based control since they are too complicated to be used for real-time computing. Crank-resolved engine air handling system modeling is also important for describing the in-cylinder charge-mixing process. Therefore, for model-based control and real-time hardware-in-the-loop simulations, it is necessary to have a crank-resolved engine model with its complexity intermediate between the time-based mean-value and one-dimensional CFD models.

Topics: Combustion , Engines
Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):S7-S10. doi:10.1115/1.2015-Dec-7.
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This article discusses the design of control system components for gasoline engines. Gasoline or, more precisely, spark ignition engines power a large majority of personal vehicles sold worldwide. A major task for the automakers is to provide good drivability and fuel economy while meeting increasingly stringent emission requirements. Achieving low emissions requires a significant reduction in cold start emissions and employment of catalytic converters to reduce tailpipe emissions once the engine is warmed up. The catalysts are loaded with precious metals – typically platinum, palladium, and rhodium. They achieve very high conversion efficiencies, but only if the engine is operated very close to stoichiometry that corresponds to the air-fuel ratio of about 14.6 for gasoline and of 9 for ethanol. Design of a control system component requires that an appropriate model be developed. The models range from very simple low-order, linear for the inner loop to a partial-differential-equation based model for the catalyst. In general, feedback controllers tolerate and even benefit from simpler models. Feed-forward control, estimation, diagnostics, and failure mode management requires more elaborate models.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):S11-S14. doi:10.1115/1.2015-Dec-8.
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This article provides an overview of control-oriented modeling and model-based estimation and control for diesel engine aftertreatment systems. The chemical reactions and physical processes that occur in diesel engine after-treatment systems are quite complex. Computational models describing the chemical reaction kinetics, flow, and thermo-physical phenomena in engine exhaust aftertreatment systems have been coming forth since the 1960s when catalytic converters were introduced for vehicle applications {AQ: This word ‘catalystic’ is not found in standard dictionaries. Please check and correct if necessary.}. Such models can provide insightful understanding and mathematical descriptions on the chemical reactions, mass transfer, and heat transfer processes in one-dimensional and multi-dimensional fashions. The primary purpose of diesel engine aftertreatment system control-oriented models is to serve for the designs of real-time aftertreatment control and fault-diagnosis systems to reduce tailpipe emissions during real-world vehicle operations. Because such control-oriented models contain physically-meaningful parameters of the actual treatment systems, the model-based estimation and control algorithms can have excellent generalizability among different platforms.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):S15-S18. doi:10.1115/1.2015-Dec-9.
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This article presents an overview of model-based transmission control. The transmission is an integral part of the automotive powertrain and connects the engine to the vehicle via the driveline. Just as for the internal combustion engine, traditional transmission control has been conducted with extensive calibrations. This is mainly due to the lack of precise models and low cost sensors that can enable real-time model-based feedback control. However the calibration-based approach is facing more challenges as the recent trend in transmission systems has driven up the time and cost associated with the calibration process. Recently, eight and nine speed transmissions have been introduced. The increasing number of different types of transmissions and the gear ratios can drastically increase the burden for control calibration. This calls for control-oriented model development and model-based control. Transmission control is mainly concerned with the transmission shift scheduling and gear ratio shift control. This shift scheduling determines when to shift and which gear to shift.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):S19-S21. doi:10.1115/1.2015-Dec-10.
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This article describes calibration of control systems for downsized boosted engines. Model-based design of powertrain and aftertreatment control systems includes plant modeling and controller synthesis. The article illustrates the typical work flow of the model-based calibration process for an engine. In the process, the first step is the design of experiment. The experiment design should cover a multisurface space. That guides the next step to collect data from an engine or powertrain at critical operating points. Once the data are collected, an engine system model is built along with its designed controller models, then the operation of the control systems and controller parameters are optimized or calibrated based on the plant models. With these initial values of the calibrations handy, one can either download the calibration into the production ECU or use a rapid prototyping controller to conduct a full validation or final fine tuning of the engine powertrain control system in test cells or on vehicles.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):30-35. doi:10.1115/1.2015-Dec-1.
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This article elaborates the advancement in internal combustion engine technology and explains why internal combustion engines will continue to be integral to the transportation of people and goods for the foreseeable future. The internal combustion engine has seen a remarkable evolution over the past century. Before 1970, the evolution of engine design was driven by quest for performance and increase in octane in the fuel supply. Since then, however, the imperative was the need to meet new emissions and fuel economy regulations. Some game-changing advances in automotive sector in recent years are improvements in engine technologies, sensors, and onboard computing power. This combination of technologies will enable unprecedented control of the combustion process, which in turn will enable real-world implementations of low-temperature combustion and other advanced strategies as well as improved robustness and fuel flexibility. In future, new engine concepts will also blend the best characteristics of both engine types to push the boundaries of efficiency while meeting stringent emissions regulations worldwide.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):36-41. doi:10.1115/1.2015-Dec-2.
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This article elaborates the features of Multi-Fluid/CO2 Plume Geothermal (CPG) energy storage system. This system provides utility-scale diurnal and seasonal energy storage and dispatchable power, while permanently sequestering carbon dioxide (CO2) from industrial-scale fossil-energy power plants. Operationally, a Multi-Fluid/CPG system is radically different from traditional power plants or energy storage systems, such as pumped hydroelectric. Most of the system resides below the ground surface, consisting of horizontal injection and production wells arrayed in concentric rings that could be five miles or more across. This ring configuration is used to pressurize and confine CO2 in the region in the center of the array and to pressurize brine between the outer two rings. Because the Multi-Fluid/CPG system relies on the injection of carbon dioxide, the cost of sequestration is turned into an operational investment. Just as enhanced oil recovery has made geological CO2 sequestration economically viable in the petroleum industry. Multi-Fluid/CPG can make it profitable to lock away CO2 that would otherwise be emitted.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):42-47. doi:10.1115/1.2015-Dec-3.
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This article discusses why Hawaii needs to find new ways to handle the influx of solar power. In Hawaii, rooftop solar panels are popping up everywhere. However, the solar boom has also created some complications, including sudden changes or disruptions in the system or problems at the distribution side, when there are lots of PV connected at the rooftops. Electrical loads in homes fluctuate all the time as power-hungry appliances like air conditioners and water heaters turn on and off, resulting in a high probability of low load and too much power. Power can go back through the nearby substation transformer and cause a rise in the voltage. That the state is split into several small islands further complicates matters. Another challenge unique to Hawaii is that each island in Hawaii is its own independent grid, and there are no neighbors to depend on for power.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):52-53. doi:10.1115/1.2015-Dec-4.
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The article presents an overview of the compressed air energy storage gas turbines (CAES GT). The CAES GT works at low turbine inlet temperatures and is capable of fast start and loading 10 minutes to full load. It is characterized by high ramp rates up or down with minimum load as low as 10%, and flat heat rate for most of the load range. With exceptional low fuel input efficiency of 85%, the kW/hr equivalent Btu input to the compression cycle must be added, resulting in an overall efficiency of close to 55%, impressive versus a 300 MW GTCC plant that is required to load follow when integrating renewable energy source. The metamorphosis from that of a “peak shaving” unit to that of a grid support and renewable energy enabler is now complete. Advanced Reheat Gas Turbines such as the GT24/26 with higher operating temperatures offer further potential development for CAES.

Commentary by Dr. Valentin Fuster
Mechanical Engineering. 2015;137(12):54-55. doi:10.1115/1.2015-Nov-5.
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This article explains how combined cycle gas turbine (CCGT) power plants can help in reducing greenhouse gas from the atmosphere. In the last 25 years, the development and deployment of CCGT power plants represent a technology breakthrough in efficient energy conversion, and in the reduction of greenhouse gas production. Existing gas turbine CCGT technology can provide a reliable, on-demand electrical power at a reasonable cost along with a minimum of greenhouse gas production. Natural gas, composed mostly of methane, is a hydrocarbon fuel used by CCGT power plants. Methane has the highest heating value per unit mass of any of the hydrocarbon fuels. It is the most environmentally benign of fuels, with impurities such as sulfur removed before it enters the pipeline. If a significant portion of coal-fired Rankine cycle plants are replaced by the latest natural gas-fired CCGT power plants, anthropogenic carbon dioxide released into the earth’s atmosphere would be greatly reduced.

Commentary by Dr. Valentin Fuster

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