Control-Oriented Engine Thermal Model

Abstract The optimization of modern internal combustion engines and vehicles led several researchers to investigate the effects of the coolant system on overall efficiency losses. Electric water pumps have been proposed as a solution to decrease the high power consumption that typically affects mechanically-driven water pumps at high engine speed. Furthermore, decoupling the coolant flow from engine speed allows achieving a better warm-up behavior. The coolant system components, however, also impact vehicle efficiency: the radiator area affects the overall aerodynamic drag coefficient, especially for race vehicles and motorcycles. A thermal model can be used to assess the effects of the components characteristics (pump size, efficiency, speed; radiator surface, fan size, etc.) both on the coolant system capability to reach and maintain the target temperature, and the power it requires. The same model-based approach can be used for optimal thermal management, to control the coolant system actuators (electric pump and valves, fan). The paper shows how the thermal behavior of the engine can be represented by means of a concentrated parameters model, taking into account the main coolant system components features. The model has been calibrated on a set of data referring to a high-performance motorcycle engine, including both idling and high vehicle speed conditions. The good agreement of the model output with experimental data both in static and dynamic conditions confirms that the model is able to catch a large part of the phenomena influencing the coolant temperature

model based control of intake air temperature and humidity on the test bench

Abstract Engine test benches are crucial instruments to perform tests on internal combustion engines. Possible purposes of these tests are to detect the engine performance, check the reliability of the components or make a proper calibration of engine control systems managing the actuations. Since many factors affect tests results in terms of performance, emissions and components durability, an engine test bench is equipped with several conditioning systems (oil, water and air temperature, air humidity, etc.). One of the most important systems is the HVAC (Heating, Ventilating and Air Conditioning), that is essential to control the conditions of the intake air. Intake air temperature, pressure and humidity should be controllable test parameters, because they play a key role on the combustion development. In fact, they can heavily affect the performance detected, such as power and specific consumption, and, in some cases, they may promote knock occurrence. This work presents an HVAC model-based control methodology, where each component of the air treatment system (humidifier, pre-heating and post-heating resistors, chiller and fan) is managed coupling open-loop and closed-loop controls. Each branch of the control model is composed of two parts, the first one to evaluate the target for the given HVAC component, based on the system physical model, the second one is a PID controller based on the difference between the set-point and the feedback values. The control methodology has been validated on an engine test bench where the automation system has been developed on an open software Real-Time compatible platform, allowing the integration of the HVAC control with all other functionalities concerning the test management. The paper shows the plant layout, details the control strategy and finally analyzes experimental results obtained on the test bench, highlighting the benefits of the proposed HVAC management approach

Wetland Plant Diversity in a Coastal Nature Reserve in Italy: Relationships with Salinization and Eutrophication and Implications for Nature Conservation

Wetlands are important centers of biodiversity. Coastal wetlands are subject to anthropogenic threats that can lead to biodiversity loss and consequent negative effects on nature conservation. We investigated relationships between wetland vegetation and habitat conditions in a coastal Nature Reserve in Northern Italy that has undergone seawater intrusion and eutrophication for several decades. The wetland vegetation in the Nature Reserve consisted of nine communities of hygrophytic and helophytic vegetation and five communities of waterplant vegetation. The hygrophytic and helophytic communities were arranged according to a salinity gradient, from salt-free habitats to strongly saline habitats. The saline habitats had high nutrient levels, due to the influx of nitrate-rich saltwater from an adjacent lagoon. The waterplant communities were all typical of freshwater habitats. Water-table depth and concentration of dissolved nutrients in the water were the main factors structuring waterplant vegetation. The main driver of future changes in the wetland vegetation of the Nature Reserve is the ongoing increase in salinity levels which may enhance expansion of halophilic species and communities, thus outcompeting locally rare freshwater species. If nutrient, especially nitrate, load further increases in the next future, this may exert negative effects on wetland species and communities preferring nutrient-poor habitats