THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THE STEADY AND TRANSIENT OPERATION OF THE EXHAUST THROTTLED DIESEL ENGINE

AIM OF THIS STUDY IS THE THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THE EXHAUST THROTTLED DIESEL ENGINE OPERATION CHARACTERISTICS: THIS MODE OF ENGINE OPERATION RESULTS IN INCREASED EXHAUST GAS TEMPERATURES TO MAKE REGENERATION OF THECERAMIC SMOKE TRAP POSSIBLE OVER A WIDE RANGE OF OPERATING CONDITIONS. A STUDYOF THE DIESEL ENGINE ENERGY BALANCE IS FOLLOWED BY THE STUDY OF THE EFFECT OF EXHAUST THROTTLING ON THE STEADY AND TRANSIENT OPERATION OF THE DIESEL ENGINE (IN THEORY AND EXPERIMENTALLY). TEMPERATURE RESPONSE OF THE TRAP AND INTERVENINGPARTS BETWEEN ENGINE AND TRAP IS STUDIED IN THE SEQUEL, IN ORDER TO OPTIMIZE FORCED REGENERATION ON TRAP SYSTEMS BASED ON EXHAUST THROTTLING. STUDY OF EXHAUST THROTTLED DIESEL ENGINE THERMAL LOADING IS MADE THROUGH THE COMPUTATION OF ENGINE COMPONENT TEMPERATURE FIELDS (CYLINDER, HEAD, PISTONS, EXHAUST VALUES).ΕΞΕΤΑΖΕΤΑΙ ΤΟ ΕΝΕΡΓΕΙΑΚΟ ΙΣΟΖΥΓΙΟ ΤΟΥ ΚΙΝΗΤΗΡΑ DIESEL. ΜΕΛΕΤΑΤΑΙ ΘΕΩΡΗΤΙΚΑ ΚΑΙ ΠΕΙΡΑΜΑΤΙΚΑ Η ΜΟΝΙΜΗ ΚΑΙ ΜΕΤΑΒΑΤΙΚΗ ΛΕΙΤΟΥΡΓΙΑ ΤΟΥ ΚΙΝΗΤΗΡΑ DIESEL ΜΕ ΣΤΡΑΓΓΑΛΙΣΜΟ ΤΗΣ ΕΞΑΓΩΓΗΣ ΤΟΥ. ΕΞΕΤΑΖΕΤΑΙ Η ΘΕΡΜΟΚΡΑΣΙΑΚΗ ΑΠΟΚΡΙΣΗ ΤΩΝ ΕΝΔΙΑΜΕΣΩΝ ΚΟΜΜΑΤΙΩΝ ΚΑΙ ΤΗΣ ΠΑΓΙΔΑΣ, ΜΕ ΣΤΟΧΟ ΤΗ ΒΕΛΤΙΣΤΟΠΟΙΗΣΗ ΣΥΣΤΗΜΑΤΩΝ ΑΝΑΓΕΝΝΗΣΗΣ ΤΗΣ ΚΕΡΑΜΙΚΗΣ ΠΑΓΙΔΑΣ ΚΑΠΝΟΥ ΜΕ ΣΤΡΑΓΓΑΛΙΣΜΟ ΤΗΣ ΕΞΑΓΩΓΗΣ ΤΟΥ ΚΙΝΗΤΗΡΑ DIESEL. ΜΕΛΕΤΩΝΤΑΙ ΘΕΡΜΟΚΡΑΣΙΑΚΑ ΠΕΔΙΑ ΣΤΗΝ ΚΥΛΙΝΔΡΟΚΕΦΑΛΗ, ΤΟ ΕΜΒΟΛΟ ΚΑΙ ΤΗ ΒΑΛΒΙΔΑ ΤΟΥ ΚΙΝΗΤΗΡΑ DIESEL ΜΕ ΣΤΡΑΓΓΑΛΙΣΜΕΝΗ ΕΞΑΓΩΓΗ. ΣΤΟΧΟΣ ΤΗΣ ΕΡΓΑΣΙΑΣ ΕΙΝΑΙ Η ΜΕΛΕΤΗ ΤΩΝ ΧΑΡΑΚΤΗΡΙΣΤΙΚΩΝ ΛΕΙΤΟΥΡΓΙΑΣ ΤΟΥ ΚΙΝΗΤΗΡΑ DIESEL ΜΕ ΣΤΡΑΓΓΑΛΙΣΜΟ ΤΗΣ ΕΞΑΓΩΓΗΣ: ΜΕ ΤΗΝ ΤΕΤΟΙΑ ΛΕΙΤΟΥΡΓΙΑ ΕΠΙΤΥΓΧΑΝΕΤΑΙ Η ΑΝΥΨΩΣΗ ΤΩΝ ΘΕΡΡΜΟΚΡΑΣΙΩΝ ΚΑΥΣΑΕΡΙΟΥ ΤΟΥ ΚΙΝΗΤΗΡΑ DIESEL ΕΤΣΙ ΩΣΤΕ ΝΑ ΕΙΝΑΙ ΔΥΝΑΤΗ Η ΑΝΑΓΕΝΝΗΣΗ ΤΗΣ ΚΕΡΑΜΙΚΗΣ ΠΑΓΙΔΑΣ ΚΑΠΝΟΥ

Experimental Investigation of the Effect of Biodiesel Blends on a DI Diesel Engine’s Injection and Combustion

Differences in the evolution of combustion in a single cylinder, DI (direct injection) diesel engine fuelled by B20 were observed upon processing of the respective indicator diagrams. Aiming to further investigate the effects of biodiesel on the engine injection and combustion process, the injection characteristics of B0, B20, B40, B60, B80 and B100 were measured at low injection pressure and visualized at low and standard injection pressures. The fuel atomization characteristics were investigated in terms of mean droplet velocity, Sauter mean diameter, droplet velocity and diameter distributions by using a spray visualization system and Laser Doppler Velocimetry. The jet break-up characteristics are mainly influenced by the Weber number, which is lower for biodiesel, mainly due to its higher surface tension. Thus, Sauter mean diameter (SMD) of sprays with biodiesel blended-fuel is higher. Volume mean diameter (VMD) and arithmetic mean diameter (AMD) values also increase with blending ratio. Kinematic viscosity and surface tension become higher as the biodiesel blending ratio increases. The SMD, VMD and AMD of diesel and biodiesel blended fuels decreased with an increase in the axial distance from spray tip. Comparison of estimated fuel burning rates for 60,000 droplets’ samples points to a decrease in mean fuel burning rate for B20 and higher blends

Energy Performance Optimization of a House with Grid-Connected Rooftop PV Installation and Air Source Heat Pump

The use of air source heat pump systems for space heating and cooling is a convenient retrofitting strategy for reducing building energy costs. This can be combined with the rooftop installation of photovoltaic panels, which can cover, to a significant degree—or even significantly exceed the building’s electricity needs, moving towards the zero energy building concept. Alternatively, increased capacity for rooftop photovoltaic (PV) installation may support the ongoing process of transforming the Greek power system away from the reliance on fossil fuels to potentially become one of the leaders of the energy transition in Europe by 2030. Standard building energy simulation tools allow good assessment of the Heating, Ventilation and Air Conditioning (HVAC) and PV systems’ interactions in transient operation. Further, their use enables the rational sizing and selection of the type of panels type for the rooftop PV installation to maximize the return on investment. The annual performance of a three-zone residential building in Volos, Greece, with an air-to-water heat pump HVAC system and a rooftop PV installation, are simulated in a TRNSYS environment. The simulation results are employed to assess the expected building energy performance with a high performance, inverter driven heat pump with scroll compressor and high efficiency rooftop PV panels. Further, the objective functions are developed for the optimization of the installed PV panels’ area and tilt angle, based on alternative electricity pricing and subsidies. The methodology presented can be adapted to optimize system design parameters for variable electricity tariffs and improve net metering policies

Interaction of a House’s Rooftop PV System with an Electric Vehicle’s Battery Storage and Air Source Heat Pump

Understanding the implications of introducing increasing shares of low-carbon technologies such as heat pumps and electric vehicles on the electricity network demand patterns is essential in today’s fast changing energy mixture. Application of heat pumps for heating and cooling, combined with the rooftop installation of photovoltaic panels, is already considered as a convenient retrofitting strategy towards building electrification. This may further profit from the parallel, rapid electrification of the automotive powertrain, as demonstrated in the present study. Exploitation of the combined battery storage of the house owners’ electric car(s) may help cover, to a significant degree, the building’s and cars’ electricity needs. To this end, an efficient single family house’s energy system with an optimized rooftop PV installation, heat pump heating and cooling, and two high efficiency electric cars is studied by transient simulation. The use of TRNSYS simulation environment makes clear the interaction of the house’s heating, ventilation, and air conditioning (HVAC) system, the house’s and cars’ batteries, and the rooftop PV system in transient operation. The building’s and EV’s energy performance on a daily, monthly, and seasonal level is compared with the respective demand curves and energy sources of the Greek electricity network. The specific design of the house’s energy system makes it a net exporter of electricity to the grid, to an annual amount of 5000 kWh. On the other hand, electricity imports are slightly exceeding 400 kWh and limited to the first two months of the year. In addition to the self-sufficiency of the household, the impact to the electricity grid becomes favorable due to the phase shift of the electricity export towards the late afternoon hours, thus assisting the evening ramp-up and adding to the grid’s stability and resilience. Based on the results of this study, the possibility of combining the financial incentives for the purchase of an EV with those for the installation of rooftop PV in the owners’ house is very promising and worth considering, due to the demonstrated synergy of electrical storage with the rooftop photovoltaic installations

Energy Performance Optimization of a House with Grid-Connected Rooftop PV Installation and Air Source Heat Pump

The use of air source heat pump systems for space heating and cooling is a convenient retrofitting strategy for reducing building energy costs. This can be combined with the rooftop installation of photovoltaic panels, which can cover, to a significant degree—or even significantly exceed the building’s electricity needs, moving towards the zero energy building concept. Alternatively, increased capacity for rooftop photovoltaic (PV) installation may support the ongoing process of transforming the Greek power system away from the reliance on fossil fuels to potentially become one of the leaders of the energy transition in Europe by 2030. Standard building energy simulation tools allow good assessment of the Heating, Ventilation and Air Conditioning (HVAC) and PV systems’ interactions in transient operation. Further, their use enables the rational sizing and selection of the type of panels type for the rooftop PV installation to maximize the return on investment. The annual performance of a three-zone residential building in Volos, Greece, with an air-to-water heat pump HVAC system and a rooftop PV installation, are simulated in a TRNSYS environment. The simulation results are employed to assess the expected building energy performance with a high performance, inverter driven heat pump with scroll compressor and high efficiency rooftop PV panels. Further, the objective functions are developed for the optimization of the installed PV panels’ area and tilt angle, based on alternative electricity pricing and subsidies. The methodology presented can be adapted to optimize system design parameters for variable electricity tariffs and improve net metering policies

Energy Analysis of a NZEB Office Building with Rooftop PV Installation: Exploitation of the Employees’ Electric Vehicles Battery Storage

Near zero energy buildings are increasing worldwide, exploiting low-carbon technologies in heating and electricity self-production. Commercial buildings are increasingly considered as candidates for the installation of smart micro-grids, which may profit from the added storage capacity of the batteries of employees electric vehicles, stationed during daytime in their charging lots. Smart exploitation of the interaction of these electricity sources and sinks may prove essential to address the complex electricity network demand patterns in today’s fast changing energy mixture. The interaction of an efficient office building’s energy system with a big rooftop photovoltaic installation and the aggregate storage capacity of 40 electric cars that are connected in the building’s charging lots is studied by means of transient simulation in TRNSYS environment. The 18-zone building’s heating, ventilation, and air conditioning system, the cars’ batteries, and photovoltaic systems’ interactions are analyzed on a monthly, seasonal, and hourly basis, against the respective demand curves of the Greek network. The results suggest that the specific system’s size may profitably support the operation of a smart micro-grid. The total annual electricity consumption of the building is computed to reach 112,000 kWh, or 20 kWh/m2y. The annual electricity needs of the 40 electric cars, amounting to 101,000 kWh, can be fully met with 30% of the photovoltaic electricity production. Thus, the building becomes a net exporter of electricity to the network, with maximum exported electricity occurring daily between 12:00 and 14:00, which is favorable to meeting the demand curve. Thus, the establishment of smart micro-grids in commercial buildings with large rooftop photovoltaic panels’ capacity and a significant number of electric cars in the employees’ car fleet is quite effective in this direction

Diesel-Injection Equipment Parts Deterioration after Prolonged Use of Biodiesel

The application of biodiesel blends is known to significantly affect operation of diesel-injection equipment, especially the injectors and fuel pump. This paper summarizes experience on this subject from burning fuel blends with high-percentages of biodiesel (up to 70%) on a common-rail, high-pressure-injection diesel engine and a conventional DI engine. Both engines were unable to start after running for 100 h each and staying shut off for more than two months. In order to understand the wear characteristics of the injector nozzle, pump pistons, and elastomer parts (in the case of the high-pressure pump of the common-rail engine), due to the prolonged operation with high-percentage biodiesel blends, their injectors and pumps parts were examined and compared by performing normal photography and low magnification microscopy. Additionally, the various elastomer parts of the high-pressure fuel pump of the common-rail engine were examined for wear and deterioration. The results are compared with existing literature results from other researchers. The observed deterioration of diesel-injection equipment is caused by use of high-percentage biodiesel blends and subsequent engine shut down

Energy Cost Assessment and Optimization of Post-COVID-19 Building Ventilation Strategies

The advent of the COVID-19 pandemic puts stress on the requirements of indoor air quality. Significant improvements in the design of building ventilation systems have become necessary, as this allows for the supply of higher quantities of outdoor air in buildings. Additional capital investment is necessary for increases in the size of ventilation fans and ducts, as well as for the installation of efficient air-to-air recuperators, to recover the enthalpy of the rejected air. To address the increased operation costs, smart strategies are necessary to make rational use of the ventilation system. The required modifications are studied in the example of an 18-zone office building located in Volos, Greece. The building’s energy performance is studied by means of transient simulation. Operation of the ground-coupled heat pump, the upgraded ventilation system and the high-performance recuperators and filters’ interactions is presented in detail at various time scales. The results show the effect of increased ventilation requirements of new and renovated office and commercial buildings in the post-COVID era. The added capital equipment and operation costs must be met with a strong and sustained engineering effort. Especially in the case of nZEB buildings, the protection of public health must be attained, with reduction of the added electricity consumption penalties, in order to keep the nZEB character of the building

A Three-Zone Scavenging Model for Large Two-Stroke Uniflow Marine Engines Using Results from CFD Scavenging Simulations

The introduction of modern aftertreatment systems in marine diesel engines call for accurate prediction of exhaust gas temperature, since it significantly affects the performance of the aftertreatment system. The scavenging process establishes the initial conditions for combustion, directly affecting exhaust gas temperature, fuel economy, and emissions. In this paper, a semi-empirical zero-dimensional three zone scavenging model applicable to two-stroke uniflow scavenged diesel engines is updated using the results of CFD (computational fluid dynamics) simulations. In this 0-D model, the engine cylinders are divided in three zones (thermodynamic control volumes) namely, the pure air zone, mixing zone, and pure exhaust gas zone. The entrainment of air and exhaust gas in the mixing zone is specified by time varying mixing coefficients. The mixing coefficients were updated using results from CFD simulations based on the geometry of a modern 50 cm bore large two-stroke marine diesel engine. This increased the model’s accuracy by taking into account 2-D fluid dynamics phenomena in the cylinder ports and exhaust valve. Thus, the effect of engine load, inlet port swirl angle and partial covering of inlet ports on engine scavenging were investigated. The three-zone model was then updated and the findings of CFD simulations were reflected accordingly in the updated mixing coefficients of the scavenging model