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Technical Paper

Under-Expanded Gaseous Jets Characterization for Application in Direct Injection Engines: Experimental and Numerical Approach

In the last years, increasing concerns about environmental pollution and fossil sources depletion led transport sectors research and development towards the study of new technologies capable to reduce vehicles emissions and fuel consumption. Direct-injection systems (DI) for internal combustion engines propose as an effective way to achieve these goals. This technology has already been adopted in Gasoline Direct Injection (GDI) engines and, lately, a great interest is growing for its use in natural gas fueling, so increasing efficiency with respect to port-fuel injection ones. Alone or in combination with other fuels, compressed natural gas (CNG) represents an attractive way to reduce exhaust emission (high H/C ratio), can be produced in renewable ways, and is more widespread and cheaper than gasoline or diesel fuels. Gas direct-injection process involves the occurrence of under-expanded jets in the combustion chamber.
Journal Article

The Evaluation of a New Kinematic Emissions Model on Real and Simulated Driving Cycles

The evaluation of vehicles real emissions circulating in urban areas is a basic activity for planning and management of implemented traffic measures aiming at emission control and air quality improvement. National, region, and city emission inventories require overall average emission estimation based on modeling technique with a few input parameters such as fleet composition and mission profile, represented by average speed. But in the field of emission modeling an important open issue is the very expensive costs of experimental campaigns needed to obtain driving cycle statistically representative of driving behavior, also if only in a specific link of a network. A possible approach to deal with this problem is represented by the use of traffic microscopic simulation models which are capable to simulate individual car motion on the basis of traffic conditions, road characteristics and management rules.
Technical Paper

Statistical Investigation of In Use Emissions and Fuel Consumption Measured by PEM on Different Gasoline Cars

In this paper some results relative to tests performed on road with a Fiat Panda Bipower, (CNG and gasoline powered), and a New Panda Twin Air with auto Start & Stop system, are presented. Gaseous emissions are measured with Portable Emission Measurement Systems (PEMS) on two different urban routes, in terms of traffic and slope characteristics during in use experiments. PEMS testing offers an easy and efficient way to evaluate the vehicle emissions over a huge variety of conditions and provides us a direct way to study the in-use emissions of combustion engines, when you want to verify the effect of the traffic and of a particular device on fuel economy and emissions reduction. Moreover now PEMS performances are very comparable to those obtained by standard laboratory instrumentation systems.
Technical Paper

Statistical Determination of Local Driving Cycles Based on Experimental Campaign as WLTC Real Approach

In the context of a transport sustainability, some solutions could be proposed from the integration of many disciplines, architects, environmentalists, policy makers, and consequently it may be addressed with different approaches. These solutions would be applied at different geographical levels, i.e. national, regional or urban scale. Moreover, the assessment of cars emissions in real use plays a fundamental role for their reductions. This is also the direction of the new harmonized test procedures (WLTP). Furthermore, it is fundamental to keep in mind that the new WLTC cycle will reproduce a situation closer to the reality comparing to the EUDC/NEDC driving cycle. In this paper, we will be focused on vehicle kinematic evaluation aimed at valuation of traffic situation and emissions.
Technical Paper

Some Comparisons between Real and KEM Predicted Emission Values on a EURO 4 Panda Bi-Fuel Vehicles

The problem of emission evaluation control and modelling is nowadays an open question. In the framework of a Decision Support System (DSS), a new approach was developed for modeling and evaluating automotive pollutant emissions. An interesting point of this proposal was the integration of the micro simulated model to obtain driving cycle. In fact an important open issue is the very expensive costs of experimental campaigns needed to obtain driving cycle statistically representative of driving behaviour. So to overcome these high costs and to extend the real vehicle operating conditions framework, a possible solution is to integrate a microsimulation model in the general context of emission modeling. But the reliability of driving cycles coming from simulation models must be evaluated with respect to the possible influence on test bench measured emissions. In this paper, we would try to present some results related to two aspects of the problem.
Journal Article

Real Time Emissive Behaviour of a Bi-Fuel Euro 4 SI Car in Naples Urban Area

An experimental campaign was carried out to evaluate the influence of CNG and gasoline on the exhaust emissions and fuel consumption of a bi-fuel passenger car over on-road tests performed in the city of Naples. The chosen route is very traffic congested during the daytime of experimental measurements. An on-board analyzer was used to measure CO, CO2, NOx tailpipe concentrations and the exhaust flow rate. Throughout a carbon balance on the exhaust pollutants, the fuel consumption was estimated. The exact spatial position was acquired by a GPS which allowed to calculate vehicle speed and the traffic condition was monitored by a video camera. Whole trip realized by the vehicle was subdivided in succession of kinematic sequences and the vehicle emissions and fuel consumption were analyzed and presented as value on each kinematic sequence. Moreover, throughout a multivariate statistical analysis of sequences, the driving cycles characterizing the use of vehicle were identified.
Technical Paper

Influence of Driving Cycles on Powered Two-Wheelers Emissions, Fuel Consumption and Cold Start Behavior

A wide investigation on powered two-wheelers (PTWs) is presented, aiming at the analysis of the influence of the driving characteristics on PTWs exhaust emissions and fuel consumption, a deeper comprehension of the engine and after-treatment system behavior within the cold start transient and the evaluation of cold start additional emissions for different two-wheelers classes. The study was developed with reference to an European context focusing on Euro 3 motorcycles and Euro 2 mopeds. An experimental investigation on instantaneous speed measurements was carried out with instrumented motorcycles, considering typical urban trips in the city of Genoa. A selection of speed profiles was then performed by processing experimental values.
Technical Paper

Influence of Catalyst Performance on Car Emissions in Urban Congested Traffic

A reason of the lack of agreement between measured pollutants concentration in the air of urban areas and vehicle pollutant emissions evaluated by available emission models is the fact that catalyst performance variability is not considered. In this paper, an experimental study on the effect of performance variability of catalyst on emissions is presented. Average emissions have been measured using driving cycles representative of different levels of urban traffic, determined by statistical methods on the basis of data detected on-road by an instrumented car. For each driving cycle, representative of a certain traffic level, different thermal starting conditions of catalyst have been tested. These conditions have been determined by the characterization of catalyst performance at steady state and are representative of real catalyst conditions experienced on the road.
Journal Article

Emissions and Combustion Behavior of a Bi-Fuel Gasoline and Natural Gas Spark Ignition Engine

In the last ten years, the number of natural gas vehicles worldwide has grown rapidly with the biggest contribution coming from the Asia-Pacific and Latin America regions. As natural gas is the cleanest fossil fuel, the exhaust emissions from natural gas spark ignition vehicles are lower than those of gasoline powered vehicles. Moreover, natural gas is less affected by price fluctuations and its resources are more evenly widespread over the globe than to oil. However, as natural gas vehicles are usually bi-fuel gasoline and natural gas, the excellent knock resistant characteristics of natural gas cannot be completely exploited. This paper shows the results of an experimental activity performed on a passenger car fuelled alternatively by gasoline and compressed natural gas (CNG). The vehicle has been tested on a chassis dynamometer over standard (NEDC) and real driving cycles (Artemis CADC), allowing to investigate a wide range of operating conditions.
Technical Paper

Emission Factors Evaluation in the RDE Context by a Multivariate Statistical Approach

The Real Driving Emission (RDE) procedure will measure the pollutants, such as NOx, emitted by cars while driven on the road. RDE will not replace laboratory tests, such as the current WLTP but it will be added to them. RDE is complementary to the laboratory-based procedure to check the pollutant emissions level of a light-duty vehicle in real driving conditions. This means that the car will be driven on a real road according to random acceleration and deceleration patterns conditioned by traffic flow. So, the procedure will ensure that cars deliver real emissions over on-road and so the currently observed differences between emissions measured in the laboratory and those measured on road under real-world conditions, will be reduced. However, the identification of a path on the road to check the test conditions of RDE is not easy and hardly repeatable.
Technical Paper

Effects of the Ambient Conditions on the Spray Structure and Evaporation of the ECN Spray G

The use of Gasoline Direct Injection (GDI) continuously increases due to the growing demand of efficiency and power output for i.c. engines. The optimization of the fuel injection process is essential to prepare an air-fuel mixture capable to promote efficient combustion, reduced fuel consumption and pollutant emissions. Good spray atomization facilitates fuel evaporation in i.c. engines thus contributing to the fuel economy and lowering the emissions. One of the key features of a multi-hole injector is to provide an optimal spray pattern in the combustion chamber and a good mixture homogenization considering the engine-specific characteristics such fuel mass-flow rate, cylinder geometry, injector position, and charge motion. This work aims to investigate the injection processes of an eight-hole direct-injection gasoline injector from the Engine Combustion Network (ECN) effort on gasoline sprays (Spray G, serial #19).
Technical Paper

Effects of Ultra-High Injection Pressures up to 100 MPa on Gasoline Spray Morphology

Very high pressures for injecting gasoline in internal combustion (i.c.) engines are recently explored for improving the air/fuel mixing process in order to control unburned hydrocarbons (UBHC) and particulate matter emissions such as for investigating new combustion concepts. The challenge remains the improvement of the spray parameters in terms of atomization, smaller droplets and their spread in the combustion chamber in order to enhance the combustion efficiency. In this framework, the raise of the injection pressure plays a key role in GDI engines for the trade-off of CO2 vs other pollutant emissions. This study aims contributing to the knowledge of the physical phenomena and mechanisms occurring when fuel is injected at ultra-high pressures for mapping and controlling the mixture formation.
Technical Paper

Analysis of the Cooling Plant of a High Performance Motorbike Engine

This paper is based on a Research Project of the Department of Mechanical Engineering (DiME) in collaboration with Aprilia, the Italian motorbike manufacturer. In an attempt to simulate the functioning of the cooling plant of the Aprilia RSV-4 motorbike a numerical model was constructed using mono-dimensional and three-dimensional simulation codes. Our ultimate aim was to create a simulation model which could be of assistance to engine designers to improve cooling plant performance, thereby reducing research and development costs. The model allows to simulate the running conditions of the whole cooling circuit upon variations in environmental and running conditions. In particular, the centrifugal pump of the cooling plant was simulated by a 3D commercial software, while the whole circuit was built by a 1D commercial code which allows simulation of all the thermal exchanges and pressure drops in the cooling circuit.
Technical Paper

A Calculation Procedure for the Evaluation of Cold Emissive Behavior of High-Performance Motorcycles

All the experimental investigations performed in the last years on newly sold motorcycles, equipped with a three-way catalyst and electronic mixture control, clearly indicate that CO and HC cold additional emissions, if compared with those exhausted in hot conditions, represent an important proportion of total emissions. Consequently, calculation programs for estimating emissions from road transports for air quality modeling in dedicated local areas should take into consideration this effect. From this motivation, an experimental activity on motorcycles cold emissive behavior is being jointly conducted by Istituto Motori of the National Research Council (IM-CNR) and the Department of Mechanic and Energetic (DiME) of the University of Naples.