Istituto Motori Research Articles

Experimental Study of Additive-Manufacturing-Enabled Innovative Diesel Combustion Bowl Features for Achieving Ultra-Low Emissions and High Efficiency

<div class="section abstract"><div class="htmlview paragraph">In recent years the research on Diesel engines has been increasingly shifting from performance and refinement to ultra-low emissions and efficiency. In fact, the last two attributes are key for the powertrain competitiveness in the propulsion electrified future, especially in the European market where 95gCO<sub>2</sub>/km fleet average and Euro6D RDE Step2 are phasing in at the same time. The present paper describes some of the most innovative research that GM and Istituto Motori Napoli are performing in the field, exploring how the steel-based additive manufacturing can be used to create innovative combustion bowl features that optimize the combustion process to a level that was not compatible with standard manufacturing technologies. In particular, a novel profile combining highly-reentrant sharp-stepped bowl with inner radial-lips has been studied on a 0.5ℓ single-cylinder engine in conjunction to a state of art 2500bar fast-acting fuel injection system, with the objective to demonstrate the full potential of optimized fuel stratification and spray separation enabled by the Radial Mixing Zone (RMZ) concept. The results confirmed the improved fuel/air mixing and more complete combustion promoted by RMZ, that favors PM oxidation. Indeed, after fine-tuning of injector protrusion and spray indexing to the radial lips, excellent reduction of PM by 25-50% vs baseline Euro6B design was recorded, with no detriment to the indicated efficiency nor engine power density. The novel bowl profile was especially effective when compact injection patterns have been applied at part load. This initial study provides a good reference for further improvements that are already under investigation, including durability of the additive manufactured piston with complex geometry.</div></div>

XXVI AIVELA National Meeting

PROCEEDINGS OF THE XXVI A.I.VE.LA. ANNUAL MEETINGMilan, Italy, 29-30 November 2018http://www.aivela.org/XXVI_Meeting/programme.htmlEDITORIALA.I.VE.LA. – the Italian Association of Laser Velocimetry and non-invasive diagnostics is a non-profit cultural association whose objective is to promote and support research in the field of non-contact or minimally invasive measurement techniques, particularly of electromagnetic-based and optical techniques.Through its Annual Meeting, AIVELA aims at creating an active and stimulating forum where current research results and technical advances can be exchanged and the development of new systems for laboratory use, field testing and industrial application can be promoted. The techniques addressed include Laser Doppler Anemometry – LDA, Phase Doppler Anemometry – PDA, Image Velocimetry – PIV, Flow visualization techniques, Spectroscopic measurement techniques (LIF, Raman, etc.), Laser Doppler Vibrometry – LDV, Speckle Pattern Interferometry – ESPI, Holographic techniques, Shearography, Digital Image Correlation – DIC, Moiré techniques, Structured light techniques, Infrared imaging, Photoelasticity, Image based measurement techniques, Ultrasonic sensing, Acoustic and Aeroacoustic measurements, etc.The first Annual Meeting was held back in October 1992 and, since then, the event has met large consensus among the research and scientific communities worldwide for the high scientific interest of the papers presented.The XXVI AIVELA Annual Meeting was organised in collaboration with Politecnico di Milano and was held at the premises of the Department of Energy, in Milan, on 29-30 November 2018.This volume contains a selection of the papers presented at the event.The detailed Programme of the Meeting can be found at: http://www.aivela.org/XXVI_Meeting/programme.htmlThe next edition of the AIVELA Annual Meeting will be held at the premises of Istituto Motori – CNR, in Naples, on 30-31 October 2019 (http://www.aivela.org/XXVII_Meeting/index.html).Trusting our Association and its initiatives will meet your interest, I wish to thank you in advance for your kind attention and hope to meet you soon at one of our events.EDITOREnrico Primo TomasiniPresident of A.I.VE.LA.

Gerotor pump cavitation monitoring and fault diagnosis using vibration analysis through the employment of auto-regressive-moving-average technique

Gerotor pumps, as well known, are widely used in lubrication circuits of internal combustion engines for their simplicity, high efficiency and low costs.In this paper an experimental characterization of a Gerotor pump is shown. The research is a collaboration between the Hydraulic Power Research Group (HPRG) of the University of Naples “Federico II” and the Istituto Motori of CNR.The aim of this research is to investigate the possibility of using simple data to acquire, as vibrational data, on the pump under investigation to detect possible cavitation problem by implementing a proper mathematical procedure to this aim. As been demonstrated that these pumps are particularly subject to cavitation.The gerotor pumps are much subject to cavitate than expected, especially under particular operating conditions of the engine. Cavitation is also correlate to vehicle dynamics particularly with the recent tendency to reduce the mass of oil in the sump. Therefore, the research to avoid cavitation is crucial nowadays. Consequently this study has been firstly performed with an experimentation on the pump by monitoring the delivered oil flow-rate and the adsorbed torque on the pump shaft. An accurate analysis of the pressure oscillations in cavitation conditions, has been, also, conducted. Then, an accelerometer sensor has been properly located to study the cavitation with a fault diagnosis system based on vibration detection.The experimental tests have been performed on a test bench of the Hydraulic Laboratory of the University of Naples “Federico II” in Italy. The bench allows testing the pump working by varying the shaft speed, the oil temperature, the suction and the delivery pressure. The main measured parameters are shaft torque, oil flow rate, mean suction and delivery pressure and the instantaneous suction and delivery pressure.As expected, tests revealed the high influence of the suction pressure on the delivered oil flow rate, while no significant influence has been noted on the adsorbed torque. Furthermore, the pressure oscillations in the pump delivery are highly influenced by the suction pressure.A non intrusive accelerometer has been installed during the experimentation on the oil pump. Since the vibration due to cavitation is the main concern of this study, the accelerometer has been mounted at the suction port in the radial direction.More precisely, the paper presents a fault diagnosis system based on vibration detection. Firstly, a Fast Fourier Transform of the vibration signal has been computed. The investigation has been made with and without the presence of cavitation varying the pump rotation speeds. Limitations due to the detecting of the on line cavitation problems by monitoring the FFT vibration spectra have been overcame by implementing an alternative method based on stochastic approach.This diagnosis method of accelerometer time series analysis based on an Auto Regressive and Moving Average (ARMA) method has been used to determine the pump failure. The diagnosis results have demonstrated the ability of the proposed mathematical technique in the identification of cavitation phenomena proving that the proposed approach is a useful methodology to detect the presence of fault. The approach can predict, with good accuracy, pump failure in real time operation. In addition, a threshold vibration level in decibel scale is also fixed.

A high efficiency 10 kWe microcogenerator based on an Atkinson cycle internal combustion engine

The paper focuses on the design and the overall performance of a 10 kW electric power microcogeneration plant suitable for local energy production, based on an Atkinson-cycle internal combustion engine prototype and entirely set by Istituto Motori of the Italian National Research Council. The engine was originally a wide-spread Diesel automotive unit, then converted into a methane spark ignition system and finally modified to perform an Atkinson/Miller cycle with an extended expansion, capable of a higher global efficiency and low gaseous emissions. The paper starts by defining the ratio which leaded to this specific choice among many other automotive and industrial engines, in order to obtain a reliable, long endurance, cost effective, high efficiency base, suitable for microcogeneration in residential or commercial applications. The new engine has been coupled with a liquid cooled induction generator, a set of heat exchangers and finally placed in a sealed containing case, to reduce both noise emission and heat losses. Then the plant has been tested as an electricity and heat production system, ready for grid connection thanks to a new designed management/control system. During endurance test a complete description of its functioning behaviour has been given.

Burning Behaviour of High-Pressure CH4-H2-Air Mixtures

Experimental characterization of the burning behavior of gaseous mixtures has been carried out, analyzing spherical expanding flames. Tests were performed in the Device for Hydrogen-Air Reaction Mode Analysis (DHARMA) laboratory of Istituto Motori—CNR. Based on a high-pressure, constant-volume bomb, the activity is aimed at populating a systematic database on the burning properties of CH4, H2 and other species of interest, in conditions typical of internal combustion (i.c.) engines and gas turbines. High-speed shadowgraph is used to record the flame growth, allowing to infer the laminar burning parameters and the flame stability properties. Mixtures of CH4, H2 and air have been analyzed at initial temperature 293÷305 K, initial pressure 3÷18 bar and equivalence ratio = 1.0. The amount of H2 in the mixture was 0%, 20% and 30% (vol.). The effect of the initial pressure and of the Hydrogen content on the laminar burning velocity and the Markstein length has been evaluated: the relative weight and mutual interaction has been assessed of the two controlling parameters. Analysis has been carried out of the flame instability, expressed in terms of the critical radius for the onset of cellularity, as a function of the operating conditions.

Analysis of a Micro Gas Turbine Fed by Natural Gas and Synthesis Gas: MGT Test Bench and Combustor CFD Analysis

In recent years, the interest in the research on energy production systems fed by biofuels has increased. Gaseous fuels obtained through biomass conversion processes such as gasification, pyrolysis and pyrogasification are generally defined as synthesis gas (syngas). The use of synthesis gas in small-size energy systems, such as those used for distributed micro-cogeneration, has not yet reached a level of technological maturity that could allow a large market diffusion. For this reason, further analyses (both experimental and numerical) have to be carried out to allow these technologies to achieve performance and reliability typical of established technologies based on traditional fuels. In this paper, a numerical analysis of a combustor of a 100-kW micro gas turbine fed by natural gas and biomass-derived synthesis gas is presented. The work has been developed in the framework of a collaboration between the Engineering Department of the University of Ferrara, the Istituto Motori - CNR (Napoli), and Turbec S.p A. of Corporeno di Cento (FE). The main features of the micro gas turbine Turbec T100, located at the Istituto Motori - CNR, are firstly described. A decompression and distribution system allows the feeding of the micro gas turbine with gaseous fuels characterized by different compositions. Moreover, a system of remote monitoring and control together with a data transfer system has been developed in order to set the operative parameters of the machine. The results of the tests performed under different operating conditions are then presented. Subsequently, the paper presents the numerical analysis of a model of the micro gas turbine combustor. The combustor model is validated against manufacturer performance data and experimental data with respect to steady state performance, i.e., average outlet temperature and emission levels. A sensitivity analysis on the model capability to simulate different operating conditions is then performed. The combustor model is used to simulate the combustion of a syngas, composed of different ratios of hydrogen, carbon monoxide, methane, carbon dioxide and water. The results in terms of flame displacement, temperature and emission distribution and values are analyzed and compared to the natural gas simulations. Finally, some simple modifications to the combustion chamber are proposed and simulated both with natural gas and syngas feeding.

The Key Role of the Closed-loop Combustion Control for Exploiting the Potential of Biodiesel in a Modern Diesel Engine for Passenger Car Applications

The present paper describes the results of a cooperative research project between GM Powertrain Europe and Istituto Motori CNR aimed at studying the capability of GM Combustion Closed-Loop Control (CLCC) in enabling seamless operation with high biodiesel blending levels in a modern diesel engine for passenger car applications. As a matter of fact, fuelling modern electronically-controlled diesel engines with high blends of biodiesel leads to a performance reduction of about 12-15% at rated power and up to 30% in the low-end torque, while increasing significantly the engine-out NOx emissions. These effects are both due to the interaction of the biodiesel properties with the control logic of the electronic control unit, which is calibrated for diesel operation. However, as the authors previously demonstrated, if engine calibration is re-tuned for biodiesel fuelling, the above mentioned drawbacks can be compensated and the biodiesel environmental inner qualities can be fully deployed. In order to enable such calibration re-tuning, it is fundamental to achieve a reliable biodiesel blending detection, and to use it for realtime combustion optimization, chiefly by optimizing the injection train. Therefore, the authors investigated the capability of CLCC to detect biodiesel blending ratio on the recently released 2.0L Euro5 GM diesel engine equipped with embedded pressure sensors in the glow plugs. Various blends of biodiesel were tested, notably 20% by volume (B20), 50% (B50) and pure biodiesel (B100). Tests on the multicylinder engine were carried out in a wide range of engine operating points for the complete characterization of the biodiesel performance in the NEDC cycle. The results demonstrated the successful capability of the CLCC control to detect biodiesel blending with reasonable accuracy and to implement the corrective actions to avoid emission drift and performance losses.

An Integrated Knowledge Base for Modelling and Predicting Vehicle Real-world Emissions as a Function of Driving Behaviour Kinematics

A multivariate modelling approach was developed by Istituto Motori to model and predict vehicle real-world emissions. Complex driving kinematics is represented by two blocks of variables, which require the development of a hierarchical multiblock emission model, where the two blocks of variables represent overall and instantaneous features of each driving cycle associated to a trip. The multiblock model was applied to analyze and model emissions of the large database built in the ARTEMIS project. In this database we collected emission measurements performed in European laboratories relative to real driving cycles which are statistically representative of many European traffic/road conditions from congested to rush-hour traffic in urban, rural and highway roads. Data concern a varied fleet of vehicles differing in technology and class. To develop a tool useful for mobility analysts for traffic environmental impact assessment, a knowledge base was envisaged to integrate the data warehouse and the model base to build a user interface for driving cycle kinematics and emission analysis. In this paper the modelling approach is presented together with overall emission and driving kinematics characterization based on experimental results, as well as functional analysis of the knowledge base structure and the information tool.

Carbonyl Compounds and PAH Emissions From CNG Heavy-Duty Engine

Previous works carried out in Istituto Motori laboratories have shown that natural gas is a suitable fuel for general means of transportation. This is because of its favorable effects on engine performance and pollutant emissions. The natural gas fueled engine provided the same performance as the diesel engine, met R49 emission standards, and showed very low smoke levels. On the other hand, it is well known that internal combustion engines emit some components that are harmful for human health, such as carbonyl compounds and polycyclic aromatic hydrocarbons (PAH). This paper shows the results of carbonyl compounds and PAH emissions analysis for a heavy-duty Otto cycle engine fueled with natural gas. The engine was tested using the R49 cycle that is used to measure the regulated emissions. The test analysis has been compared with an analysis of a diesel engine, tested under the same conditions. Total PAH emissions from the CNG engine were about three orders of magnitude lower than from the diesel engine. Formaldehyde emission from the CNG engine was about ten times as much as from the diesel engine, while emissions of other carbonyl compounds were comparable.