• Energy Research

Abstract An experimental and theoretical investigation is being performed to evaluate exhaust emissions and fuel consumption of Heavy Duty Vehicles (HDVs) circulating in urban areas and involved in commercial shipping activities. The study is focused on the city of Genoa, whose urban road network is influenced by highway connections and shipping activities, as seven motorway exits and more than twenty accesses to port area are located within the urban area. In a first step, the HDV flows crossing highway exits, urban zones and port areas were evaluated, as well as the relevant vehicle classes. The typical urban trips linking highway exits to port gates and the HDV mission profiles within the port area were then defined, whose validation was performed through an experimental campaign for HDV instantaneous speed measurements on urban trips and in port zones. The availability of speed patterns enabled the application of Passenger Car and Heavy Duty Emission Model (PHEM) for the estimation of fuel consumption and emission factors for selected HDV classes. The main results of the different investigation steps are presented and discussed in the paper, outlining the specific activities of HDVs in port area and the relevant emissive behaviour.

Abstract An experimental investigation on instantaneous speed measurements with instrumented motorcycles was performed considering three typical urban trips, divided in twelve sections according to different road classes. The main kinematic parameters obtained by processing experimental values are presented and compared with those referred to standard cycles, confirming that real world driving conditions are hardly reproduced by statutory cycles. Several applications of measured data are then analysed. Exhaust emission and fuel consumption factors were calculated for different motorcycle classes by applying the functions of Copert, Artemis and Progress models and the Artemis traffic situation approach, considering typical average speed levels and the experimental values. Results are then compared in order to highlight the differences between applied functions and methodologies. A selection of speed profiles was also performed in order to define the emissive behaviour of two-wheelers on the chassis dynamometer: experimental emission and consumption factors for a Euro 3 scooter are related to calculated levels, while measured cold and hot exhaust emissions and fuel consumption of a Euro 2 moped are compared with the results obtained on standard and real world driving cycles, proving that the new speed patterns may be useful to define emissions and fuel consumption of these vehicles.

Experimental investigations on automotive engine intake and exhaust components are fundamental to achieve a better understanding of their behaviour both in steady and transient operation. To this purpose a dedicated test facility, particularly suited for the evaluation of exhaust turbochargers performance, has been operating at the University of Genoa (ICEG). In the paper a new arrangement of the testing circuit and of the relevant measuring system is presented. At the conclusion of the plant setup a first investigation on a typical automotive turbocharger for spark ignition application was developed. After measuring compressor and turbine steady flow curves in a wide operating range, the attention was focused on unsteady flow phenomena in the exhaust subsystem when using the two pulsating flow generators available on the test rig. The relevant results are presented in the paper referring to measured pressure diagrams. In particular, the effect of the turbine feeding circuit geometry and of the turbocharger regulating device is analysed and discussed.

Abstract To make simulation models able to accurately predict engine performance, a better understanding of compressor behavior over an extended range can be accomplished by using a specialized test facility and measuring equipment. Besides, the correct surge line position is another important aspect to be considered to optimize engine-turbocharger matching calculation. In the paper the results of an experimental investigation developed on a turbocharger compressor for heavy duty vehicle application is presented. The study was focused on the definition of surge line position adopting different methods and on the evaluation of compressor performance over an extended range, taking into account compressor behavior both in the stable and unstable operating region.

In the last few years, the effect of diabatic test conditions on compressor performance maps has been widely investigated leading some Authors to propose different correction models. The aim of the paper is to investigate the effect of heat transfer phenomena on the experimental definition of turbocharger maps, focusing on turbine performance. An experimental investigation on a small turbocharger for automotive application has been carried out and presented. The study focused onto the effects of internal heat transfer on turbine thermomechanical efficiency. The experimental campaign was developed considering the effect of different heat transfer state by varying turbine inlet temperature, oil and coolant temperature and compressor inlet pressure. An original model previously developed by the Authors is adopted for the correction of compressor steady flow maps. The major benefit of this method is represented by the easiness of data post-processing, the data base economy, the reduced number of geometrical and physical input parameters required and the accuracy of the solution. Besides, this model does not need an out-of-standard test bench to obtain the compressor maps. The corrected compressor results were then used to evaluate turbine thermomechanical efficiency, generally assessed on the basis of compressor power absorption.

In the paper the results of an experimental investigation developed on a small turbocharger turbine for automotive application are presented, including the effect of the waste-gate valve opening. The study was focused on the evaluation of turbine efficiency, especially under unsteady flow conditions typically occurring in automotive turbocharged engines. Turbine efficiency values measured under steady and pulsating flow conditions are compared, also considering a quasi-steady flow approach.

Abstract In the last few years, the effect of diabatic test conditions on compressor performance maps has been widely investigated leading some Authors to propose different correction models. The aim of the paper is to investigate the effect of heat transfer phenomena on the experimental definition of turbocharger maps, focusing on compressor performance. This work was developed within a collaboration between the Polytechnic School of the University of Genoa (Italy) and the testing center CRITT M2A (France). In particular, an original model for the correction of compressor steady flow maps is presented and discussed. The major benefit of this method is represented by the easiness of data post-processing, the data base economy, the reduced number of geometrical and physical input parameters required and the accuracy of the solution. Besides, this model does not need an out-of-standard test bench to obtain the compressor maps. In the paper, experimental tests under quasi-adiabatic conditions developed to validate the proposed model are reported. A satisfactory agreement between measured and calculated compressor maps is highlighted.

In the paper the results of an experimental campaign regarding the steady characterization of a turbocharger waste-gated turbine (IHI-RHF3) for gasoline engine application are presented. The turbine behavior is analyzed in a specialized test rig operating at the University of Genoa, under different openings of the waste-gate valve. The test facility allows to measure inlet and outlet static pressures, mass flow rate and turbocharger rotational speed. The above data constitute the basis for the tuning and validation of a numerical procedure, recently developed at the University of Naples, following a 1D approach (1D turbine model – 1DTM). The model geometrically schematizes the entire turbine based on few linear and angular dimensions directly measured on the hardware. The 1D steady flow equations are then solved within the stationary and rotating channels constituting the device. All the main flow losses are properly taken into account in the model. A preliminary tuning is carried out based on the characteristic map measured for a completely closed waste-gate valve. A 1D schematization of the experimental test rig is implemented within the commercial GT-PowerTM software, including the turbine, the waste-gate and the upstream and downstream circuits. In particular, the turbine model itself consists of a sequence of pipes that schematize each component of the device (inlet/outlet ducts, volute and wheel). The pipes dimensions are automatically provided by the geometrical module of the 1DTM. In the turbine schematization, the “wheel-map”, estimated by means of the above mentioned 1DTM, is utilized. The latter does not take into account phenomena and losses occurring in the volute and in the intake/outlet ducts, as well. A refined modeling of the waste-gate system reveals to be necessary to correctly reproduce the swallowing capacity of the by-pass port. The waste-gate model is tuned against the experimental findings for a completely closed turbine wheel and various settings of the by-pass port. Finally, once the 1D models of the turbine and of the waste-gate system are independently tuned, their behavior under parallel flow is analyzed. The proposed numerical and experimental results demonstrate the mutual interaction of the two components. In addition, it is put into evidence that turbine and waste-gate circuit cannot be considered as two systems working in parallel under the same pressure ratio, as usually assumed in 1D codes.