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Presently the on-the-road transportation sector is responsible of the 21% of the whole CO2 amount emitted into atmosphere. This pushes the International Governments and Organizations to provide strict limitations in terms of ICEs emissions, also introducing fees payment for the car manufacturers. The vehicle electrification allows certainly to meet these requirements, but the higher cost and the need of a green electricity still limit a widespread diffusion among all social classes. Thus, the technological improvement of internal combustion engine plays a key role in the transition period. Among these technologies, the engine thermal management allows to achieve a good compromise between the CO2 emission reduction and related costs. It was demonstrated that replacing the conventional centrifugal pump of engine cooling system with a sliding vane rotary pump (SVRP), important benefits in terms of CO2 emission reduction can be achieved as centrifugal pump efficiency decreases significantly when the engine works far from the maximum load (i.e. design point of the pump). Nevertheless, the complex thermo-fluid-dynamic phenomena taking place inside a SVRP make its design not immediate, particularly if heavy duty ICE cooling systems are considered. These applications indeed are challenging due to the wide operating range and the huge flow rates which pump must deliver. These operating requirements make difficult the choice of the main design parameters: among the different ones, the pump revolution speed and displaced volume. In the present paper a design strategy is developed for this type of pumps based on a comprehensive mathematical model of the processes occurring, predicting volumetric, indicated and mechanical efficiencies. The model was validated with a wide experimental activity so acting as virtual development platform. The results show how the best global efficiency (0.59) is achieved adopting a dual axial intake port configuration, with a suitable choice result of a trade-off between displaced volume and revolution speed. The analysis also show that the pump keeps its efficiency close to the design one for a wide operating range which is particularly suitable for the cooling of an ICE.

Suitability to off-design operation, applicability to combined thermal and electrical generation in a wide range of low temperatures and pressures and compliance with safety and environmental limitations qualify small-scale Organic Rankine Cycle plants as a viable option for combined heat and power generation in the residential sector. As the plants scale down, the electric and thermal output maximization has to account for issues, spanning from high pump power absorption, compared to the electric output of the plant, to intrinsically low plant permeability induced by the expander, to the intermittent availability of thermal power, affected by the heat demand for domestic hot water (DHW) production. The present paper accounts for a flat-plate solar thermal collector array, bottomed by an ORC unit featuring a sliding vane expander and pump and flat-plate heat exchangers. A high-temperature buffer vessel stores artificially heated water – electric heaters, simulating the solar collector - and feeds either the hot water line for domestic use or the ORC evaporator, depending on the instantaneous demand (i.e., domestic hot water or electric power), the temperature conditions inside the tank and the stored mass availability. A low-temperature receiver acts like the heat sink of the ORC unit and harvests the residual thermal power, downstream the expander: a dedicated control, modelled to properly modulate the mass addition/subtraction to this storage unit allows to restore the operating points of the cycle and to limit the incidence of off-design operation, via real-time adjustment of the cycle operating parameters. Indeed, the possibility of continuous ORC generation depends on (i) the nature of the demand and (ii) the amount of hot water withdrawn from the high-temperature buffer vessel. The time-to-temperature for the mass stored inside the buffer affects the amount of ORC unit activations and eventually the maximum attainable generation of electric energy. The plant energy performance is experimentally assessed, and various characteristic operating points are mapped, based on test runs carried out on a real-scale ORC pilot unit.

The high viscosity of the lubricant oil in internal combustion engines at cold starts is responsible for poor friction reduction and inadequate thermal stabilization of metallic masses and represents a major bottleneck in the efforts to reduce specific fuel consumption and pollutant emissions. Consequently, the possibility of integrating techniques for proper thermal management of the lubricant oil on internal combustion engines is of utmost importance to both homologation and daily on-road operation. Main options for reducing the warm-up time for the engine lubricant are the upgrade of the engine cooling and lubricating circuits, dedicated heating, different flow management of the oil/coolant heat exchanger, a renewed design of the oil sump or a thermal storage section to increase the oil temperature in the early phases of the warm up. The paper presents a new opportunity, using a hot storage medium to heat up the oil in the early phase of a driving cycle. A certain quantity of hot water, so, is stored in a tank, which can be used to warm up the lubricating oil when the engine is started up. The heating of this service water can be done by using exhaust gas heat, which is always wasted in the atmosphere. The activity is realized on an IVECO 3.0 L light-duty diesel engine, during a transient cycle (NEDC) on a dynamometric test bench. The benefits in terms of both fuel consumption and CO2 emissions reduction. The characterization of the backpressure associated with an eventual additional heat exchangers and the more complex layout of the oil circuit is assessed, as well as the transient effects produced by the faster oil warm-up and oil-coolant interaction on the engine thermal stabilization.

Recent EU Regulations have been pushing the transportation sector increasingly towards the reduction of primary harmful pollutants and CO2 emissions. In this context, the Internal Combustion Engine (ICE) cooling system is gaining a new technological interest. In fact, improvements on pump efficiency can significantly reduce its absorbed energy during real on-the-road operation. Typically, centrifugal pumps are adopted, but their efficiency is highly dependent on rotational speed, wasting energy during real operation, even if they are designed to have a very high efficiency at the design point. This study investigates the three screws pumps potentiality to substitute traditional centrifugal pumps in engine cooling applications. In fact, triple-screw pumps belong to positive displacement pumps, which have an efficiency ideally independent on rotational speed. A zero-dimensional mathematical model of this pump previously developed by the authors was improved, giving a specific focus on the mechanical efficiency of the pump. The validation of the model resulted in a good agreement with experimental results. The model has been used to design a pump for an IVECO F1C diesel engine. The energy requested to drive the pump over a Worldwide Harmonized Light Vehicles Test Cycle (WLTC) has been calculated and compared with that of the traditional existing centrifugal pump. Results show that the electrically actuated triple screw pump allows to reduce the energy of about 14 %.

In this paper, an experimentally based procedure is presented to re-orient the design point of the pump in order to minimize the energy absorbed during the homologation cycle or during any real driving one. During it, in fact, every benefit on the pump’s efficiency is appreciated and produces fuel consumption and CO2 reduction. The procedure takes the advantage from a dynamic test bench for coolant pump, realized and engineered at University of L’Aquila. It has been linked to a model-based methodology, which evaluates, according to a specified vehicle’s mission profile, the speed and load variation of the engine propelling the vehicle, and, therefore, the pump speed. The knowledge of the engine cooling circuit for closed and fully opened thermostat allows the calculation of the flow rates and pressure delivered in each time instant of the drive cycle. The speed-flow rate-pressure delivered pump profile has been reproduced on the bench, and all the relevant quantities have been measured: an exact evaluation of the scatter of the efficiency of the pump, the instantaneous power and the overall energy absorbed have been obtained. Results show how the pump efficiency is far from its Best Efficiency Point. This conclusion invited the Authors to reorient the design pump considering an operating condition, which has a greater occurrence among all the operating points characteristic of a drive cycle. Four pumps have been designed following this approach, showing a sensible reduction of the energy absorbed: this represents a key point also for pump electrification.

To date, Sliding Vane Pump (SVP) technology is one of the most attractive solution in different technical applications thanks to its reliability and compactness and capability to keep a high efficiency even when it is working far from rated condition. In particular, this feature makes the SVP suitable to be employed for the oil circulation (SVOP) in Internal Combustion Engine (ICE) which is characterized by a wide oil flow rates variation, delivered pressure and temperature variation which causes operating conditions of the pump far from the design point. Flow delivered changes in these machines are produced by varying the eccentricity for a mechanical connection with the engine - or by varying the speed of revolution. The mild hybridization of the powertrains calls for a strong development of electrically assisted engine auxiliaries which undoubtedly makes the flow variations easier to be done, but the presence of an electric motor requires some technological choices not fully assessed, a cost increase and a reliability decrease. The paper presents a mathematical model of a SVOP for oil circulation in ICE, suitably validated by a wide experimental activity. The model integrates a mono and zero-dimensional fluid-dynamic analysis and allows to represent the intimate behaviour of the machine. Moreover, it was employed as virtual platform to discuss pros and cons of different flow rate variation strategies and their effect on the efficiency of the SVOP.

Integrating flat solar thermal collectors and organic Rankine cycle (ORC)-based power units in micro-cogeneration systems ensures a reduction in CO 2 emissions in domestic applications. The key component of these systems is the expander, which must withstand frequent off-design operating conditions owing to the intermittent nature of the solar source. Despite being in the first stage of technological development, scroll expanders are widely adopted in small-scale applications owing to their operating flexibility and robustness. In this study, a domestic micro-cogeneration unit equipped with a scroll expander is characterised experimentally. The experimental data are used to calibrate the expander and ORC unit models. The models are used to evaluate the operating limits of the units as functions of the main operating parameters. The maximum power and efficiency are obtained as 300 W and 3 %, respectively, for hot water temperatures between 90 °C and 100 °C, close to the rated performances. Finally, the effect of adopting a dual-intake port on the expander and unit performance is assessed. The technology facilitates the widening of the operating range (20–140 g/s mass flow rate of WF) and a peak power production of 1.2 kW. • Development of novel operating maps of solar ORC unit for micro-cogeneration. • Assessment of the impact of scroll expander improvement on ORC unit operability. • Development of a novel regulating strategy based on Dual Intake Port (DIP) technology. • DIP regulation ensures a wider operability than expander variable speed regulating approach. • DIP regulating strategies avoid unworking region with a power peak of 1.2 kW. [ABSTRACT FROM AUTHOR]

The efficiency improvement of Internal Combustion Engines (ICEs) is still necessary, providing them a valid contribution to the future of road propulsion, increasingly governed by regulations aimed at curbing CO 2 emissions. In this context, technologies related to engine thermal management, and more specifically to the cooling pump, offer a good potential. Screw-type cooling pumps, notably triple-screw pumps (TSP), emerge as a solution, demonstrating superior efficiency compared to centrifugal pumps at design and off-design operating conditions. A TSP optimized in terms of efficiency for the cooling system of a turbocharged gasoline engine was investigated. The requested high speed of rotation suitable for engine cooling to reduce size and weight led to the introduction of a new screws' arrangement, which improved pump durability and mechanical efficiency, but enhanced the impact of clearances on the so-called blowhole backflow, usually negligible for bigger pump sizes. Hence, a refined mathematical model capable to predict the new screw pump's performances was developed and experimentally validated. A stable and high mechanical efficiency (>80 %), and a global efficiency greater than 50 % even very far from the design point, were reached. This feature applies in engine cooling, but can be useful also in industrial applications requiring high pump efficiency. • Development of a prototype screw pump optimized for engine cooling. • Mathematical modeling of blowhole backflow and friction power losses. • Experimental validation of the mathematical model; testing of the prototype. • Mechanical efficiency improved by 10 % compared to simpler screw pumps. • High efficiency (>50 %) in harsh off-design conditions. [ABSTRACT FROM AUTHOR]