Effect of Fuel Properties on Emissions from Euro 4 and Euro 5 Diesel Passenger Cars

Abstract The EN 590 specification allows up to 7% v/v FAME to be blended into conventional diesel fuel which can then be used in most light-duty diesel vehicles. It is anticipated that higher FAME levels may be needed in order to meet the 10% renewable energy target mandated by the Renewable Energy Directive (2009/EC/28). Certain diesel fuel specification properties are considered to be environmental parameters according to the European Fuels Quality Directive (FQD, 2009/EC/30) and previous regulations. These limits included in the EN 590 specification were derived from the European Programme on Emissions, Fuels and Engine Technologies (EPEFE) which was carried out in the 1990's on diesel vehicles meeting up to Euro 3 emissions standards. These limits could potentially constrain FAME blending levels higher than 7% v/v. No significant work has been conducted to investigate whether relaxing these limits would give rise to efficiency or emissions debits or benefits. For this reason, Concawe was interested in studying the impact of these parameters in Euro 4+ vehicle technology. A test programme has been conducted to evaluate the impact of specific diesel properties on emissions on a Euro 5 light-duty diesel vehicle. Tests were also carried out in a Euro 4 vehicle to provide comparison with previous work. Properties studied were Poly-Aromatic Hydrocarbon (PAH) content, density, and cetane number. The Fatty Acid Methyl Ester (FAME) content was an additional variable in the study. Results of emissions testing will be presented and discussed including effects of the above fuel properties on particulates, NOx, CO2 and fuel consumption

A simulation model of the real-world fuel and energy consumption of light-duty vehicles

The European Union has intensified efforts to reduce CO2 emissions from the transport sector, with the target of reducing tailpipe CO2 emissions from light-duty vehicle new registrations by 55% by 2030 and achieving zero emissions by 2035 according to the “Fit for 55” package. To promote fuel and energy consumption awareness among users under real-world conditions the MILE21—LIFE project provided tools such as a self-reporting tool and a find-a-car tool that included the official and representative on-road fuel/energy consumption values. In order to produce representative values, an in-house vehicle longitudinal dynamics simulation model was developed for use in the background of the on-line platform utilizing only a limited amount of inputs. To achieve this, the applied methodology is based on precalculated efficiency values. These values have been produced using vehicle micro-model simulations covering a wide range of operating conditions. The model was validated using measurements from a dedicated testing campaign and performed well for petrol vehicles with an average divergence of −1.1%. However, the model showed a divergence of 9.7% for diesel vehicles, 10.6% for hybrids and 8.7% for plug-in hybrids. The model was also applied to US vehicles and showed a divergence of 1.2% and 10% for city and highway driving, respectively. The application of the developed model presented in this work showed that it is possible to predict real-world fuel and energy consumption with the desired accuracy using a simplified approach with limited input data

Characterization of laboratory and real driving emissions of individual Euro 6 light-duty vehicles – Fresh particles and secondary aerosol formation

Emissions from passenger cars are one of major sources that deteriorate urban air quality. This study presents characterization of real-drive emissions from three Euro 6 emission level passenger cars (two gasoline and one diesel) in terms of fresh particles and secondary aerosol formation. The gasoline vehicles were also characterized by chassis dynamometer studies. In the real-drive study, the particle number emissions during regular driving were 1.1–12.7 times greater than observed in the laboratory tests (4.8 times greater on average), which may be caused by more effective nucleation process when diluted by real polluted and humid ambient air. However, the emission factors measured in laboratory were still much higher than the regulatory value of 6 × 10^(11) particles km^(−1). The higher emission factors measured here result probably from the fact that the regulatory limit considers only non-volatile particles larger than 23 nm, whereas here, all particles (also volatile) larger than 3 nm were measured. Secondary aerosol formation potential was the highest after a vehicle cold start when most of the secondary mass was organics. After the cold start, the relative contributions of ammonium, sulfate and nitrate increased. Using a novel approach to study secondary aerosol formation under real-drive conditions with the chase method resulted mostly in emission factors below detection limit, which was not in disagreement with the laboratory findings

Impact of Active Diesel Particulate Filter Regeneration on Carbon Dioxide, Nitrogen Oxides and Particle Number Emissions from Euro 5 and 6 Vehicles under Laboratory Testing and Real-World Driving

Particulate mass concentration is a crucial parameter for characterising air quality. The diesel particulate filter (DPF) is the primary technology used to limit vehicle particle emissions, but it needs periodic cleaning, a process called regeneration. This study aims to assess the impact of active DPF regeneration on the performance and emissions of Euro 5 and 6 vehicles. The study examined both carbon dioxide (CO2) and pollutant (nitrogen oxides (NOx) and particle number (PN)) emissions for eight vehicles tested in the laboratory and on the road. Apart from the DPF, a wide range of emission control systems was covered in this experimental campaign, including exhaust gas recirculation (EGR), diesel oxidation catalyst (DOC), lean NOx trap (LNT) and selective catalytic reduction (SCR) catalyst, revealing the different impacts on NOx emissions. The regeneration frequency and duration were also determined and used to calculate the Ki factor, which accounts for the emissions with and without regeneration, weighted over the distance driven between two consecutive regeneration events. Based on these outcomes, representative emission factors (EF) were proposed for the regeneration phase only and the complete regeneration interval. In addition, the effect of regeneration on efficiency was estimated and compared with other energy consumers. The results indicated a significant impact of DPF regeneration on CO2, NOx and PN emissions, higher in the case of driving cycle testing in the laboratory. The relevant mechanisms behind the elevated emission levels were analysed, focusing on the regeneration period and the test phase following immediately after. The calculation of the Ki factor and the comparison with the official values revealed some weaknesses in its application in real-world conditions; to overcome these, new NOx EF values were calculated, depending on the emission control system. It was revealed that Euro 6 vehicles equipped with SCR could comply with the applicable limits when considering the complete regeneration interval. Finally, it was indicated that the DPF regeneration impact on vehicle efficiency is similar to that of driving with the air conditioning (A/C) system and headlights on

Investigation of exhaust emissions during transient operation of diesel engines

The target of the current PhD thesis is the evaluation and interpretation of exhaust emissions and combustion noise during transient operation of turbocharged diesel engines, by studying the relevant phenomena and pointing out the substantial differences compared to the respective steady-state condition. The investigation consists of experimental measurements which are conducted on the test-bed of a six cylinder turbocharged diesel engine. Various measuring devices are installed in order to record continuously the engine’s operating parameters. Ultra fast response exhaust gas analyzers are used for the continuous measurement of pollutant emissions. The investigation includes nitric oxide (NO) and soot, as well as combustion noise, which has attracted much attention during the last years. The investigation focuses on acceleration, since the engine is intended for vehicle applications. Various accelerations are conducted commencing from different initial conditions, mimicking real vehicle acceleration with different gear. Moreover, the really measured values of exhaust emissions are compared with their steady-state counterparts in order to identify the crucial differences between the two operating conditions. The results point out turbocharger lag, while it is made clear that transient operation can not be considered as a series of steady-state operating points. The different formation mechanism of soot between transient and steady-state conditions is revealed, while a qualitative correlation between NO emissions and combustion noise is observed. Afterwards, engine starting is studied, with the main focus being on cold starting. Various other starting tests are included, which are conducted at different coolant temperatures and idling speeds. The results point out turbocharger lag, the effect of which is varied according to the starting conditions. Additionally, combustion instability is revealed, which is more intense during cold starting. Moreover, extremely high values of exhaust opacity are observed combined with high NO concentrations in the exhaust gas. The investigation also includes accelerations and a starting with blends of diesel with biodiesel or butanol. The results show that during acceleration soot emissions are lowered, NO emissions are higher, while combustion noise is affected only by the butanol blend. During starting, the only difference is that the biodiesel blend increases soot emissions.Ο στόχος της παρούσας διατριβής είναι η αξιολόγηση και η ερμηνεία των εκπομπών ρύπων και θορύβου της καύσης κατά τη μεταβατική λειτουργία υπερπληρωμένων κινητήρων diesel, εμβαθύνοντας στα σχετικά φαινόμενα και αναδεικνύοντας τις ουσιώδεις διαφορές από την αντίστοιχη μόνιμη κατάσταση. Η διερεύνηση περιλαμβάνει πειραματικές μετρήσεις, οι οποίες διεξάγονται στην κλίνη εξακύλινδρου υπερπληρωμένου κινητήρα diesel οχήματος. Στον κινητήρα εγκαθίστανται μετρητικές διατάξεις για την καταγραφή των λειτουργικών του παραμέτρων και αναλυτές καυσαερίων υπερταχείας απόκρισης για τη συνεχή μέτρηση των στιγμιαίων εκπομπών ρύπων. Η διερεύνηση περιλαμβάνει το μονοξείδιο του αζώτου (NO) και την αιθάλη, καθώς και το θόρυβο της καύσης, η μελέτη του οποίου έχει προσελκύσει μεγάλο ενδιαφέρον τα τελευταία χρόνια. Η διερεύνηση επικεντρώνεται στην επιτάχυνση του κινητήρα, λόγω της εφαρμογής του σε οχήματα. Εκτελούνται μεταβολές από διάφορες αρχικές συνθήκες αντιπροσωπεύοντας την επιτάχυνση ενός οχήματος με διαφορετική σχέση μετάδοσης. Επίσης, οι πραγματικά μετρημένες εκπομπές ρύπων συγκρίνονται με εκείνες των αντίστοιχων μόνιμων συνθηκών, για τον εντοπισμό των διαφορών ανάμεσα στις δύο καταστάσεις. Τα αποτελέσματα αναδεικνύουν την υστέρηση του υπερπληρωτή, ενώ καθίσταται σαφές ότι η μεταβατική λειτουργία δεν μπορεί να θεωρηθεί ως αλληλουχία σημείων μόνιμης λειτουργίας. Ακόμα, αναδεικνύεται ο διαφορετικός μηχανισμός σχηματισμού της αιθάλης ανάμεσα σε μεταβατικές και μόνιμες συνθήκες, ενώ διαπιστώνεται συσχέτιση ανάμεσα στις εκπομπές NO και θορύβου της καύσης. Ακολούθως, μελετάται η εκκίνηση του κινητήρα. Το κύριο ενδιαφέρον επικεντρώνεται στην ψυχρή εκκίνηση, ενώ περιλαμβάνονται και εκκινήσεις σε διάφορες θερμοκρασίες του ψυκτικού και ταχύτητες περιστροφής (“ρελαντί”). Τα αποτελέσματα αναδεικνύουν την υστέρηση του υπερπληρωτή, η επίδραση της οποίας μεταβάλλεται ανάλογα με τις συνθήκες εκκίνησης. Παράλληλα, φανερώνουν την αστάθεια της καύσης, η οποία είναι έντονη στην ψυχρή εκκίνηση. Ακόμα, επισημαίνονται οι πολύ υψηλές εκπομπές αιθάλης και η σημαντικότητα της μελέτης των εκπομπών NO κατά την εκκίνηση του κινητήρα. Η διερεύνηση περιλαμβάνει επιταχύνσεις και εκκίνηση με μίγματα του πετρελαίου με βιοντήζελ ή βουτανόλη. Τα αποτελέσματα δείχνουν ότι κατά την επιτάχυνση, οι εκπομπές αιθάλης μειώνονται, οι εκπομπές NO αυξάνονται, ενώ ο θόρυβος της καύσης επηρεάζεται μόνο από το μίγμα της βουτανόλης. Η μόνη διαφορά κατά την εκκίνηση είναι ότι το μίγμα του βιοντήζελ αυξάνει τις εκπομπές αιθάλης

Investigation of exhaust emissions during transient operation of diesel engines

476 σ.Η παρούσα διδακτορική διατριβή διαπραγματεύεται το θέμα της μεταβατικής λειτουργίας υπερπληρωμένων κινητήρων diesel, επικεντρώνοντας στις εκπομπές ρύπων και θορύβου της καύσης. Η μεταβατική λειτουργία αποτελεί μία κατάσταση εξαιρετικής σημασίας, λόγω των ιδιαιτεροτήτων που παρουσιάζει σε σχέση με τη μόνιμη, καθώς και εξαιτίας της σημαντικής της συνεισφοράς στις συνολικές εκπομπές ρύπων ενός κινητήρα. Τα φαινόμενα είναι ιδιαίτερα έντονα σε κινητήρες οχημάτων (π.χ. λεωφορεία, φορτηγά), των οποίων η λειτουργία είναι σχεδόν αποκλειστικά μεταβατική. Βασικός στόχος της παρούσας διατριβής είναι η αξιολόγηση και η ερμηνεία των εκπομπών ρύπων και θορύβου της καύσης κατά τη μεταβατική κατάσταση, μελετώντας τα σχετικά ιδιαίτερα φαινόμενα. Η κατανόηση των συνθηκών οι οποίες προκαλούν τις υψηλές εκπομπές ρύπων και θορύβου της καύσης κατά τη μεταβατική λειτουργία ενός κινητήρα αποτελεί τη βάση για την ανάπτυξη μεθόδων και συστημάτων ελέγχου τους. Έτσι, η παρούσα εργασία αποσκοπεί στην εμβάθυνση στους μηχανισμούς και τα φαινόμενα της μεταβατικής λειτουργίας υπερπληρωμένων κινητήρων diesel, καθώς και στην ανάδειξη των ουσιωδών διαφορών από την αντίστοιχη μόνιμη κατάσταση. Η διερεύνηση στα πλαίσια της παρούσας διατριβής διεξάγεται σε πειραματικό επίπεδο. Οι δοκιμές πραγματοποιούνται στην πειραματική κλίνη εξακύλινδρου υπερπληρωμένου κινητήρα diesel, ο οποίος βρίσκεται εγκατεστημένος στο εργαστήριο Μ.Ε.Κ. του Ε.Μ.Π.. Η ευρεία εφαρμογή του συγκεκριμένου κινητήρα σε οχήματα (π.χ. αστικά λεωφορεία, φορτηγά) τον καθιστά ιδανική επιλογή για τη μελέτη της μεταβατικής λειτουργίας. Στον κινητήρα εγκαθίσταται μία πληθώρα μετρητικών διατάξεων και συσκευών για τη συνεχή καταγραφή των βασικών λειτουργικών του παραμέτρων, καθώς και αναλυτές καυσαερίων υπερταχείας απόκρισης που είναι ειδικά σχεδιασμένοι για μετρήσεις σε μεταβατικές συνθήκες λειτουργίας μηχανών εσωτερικής καύσης. Με αυτόν τον τρόπο είναι εφικτή η συνεχής καταγραφή των στιγμιαίων (σε επίπεδο κύκλου λειτουργίας) εκπομπών ρύπων. Η διερεύνηση περιλαμβάνει τους δύο σημαντικότερους ρύπους των κινητήρων diesel, το μονοξείδιο του αζώτου (NO) και την αιθάλη. Η γνωστή “αντιθετική” μεταβολή των δύο αυτών ρύπων ενός κινητήρα diesel, καθιστά εξαιρετικής σημασίας την ταυτόχρονη μελέτη τους σε μεταβατικές συνθήκες. Πέραν των προαναφερθέντων ρύπων, η διερεύνηση επεκτείνεται και στη μελέτη ενός ακόμα ιδιαίτερου χαρακτηριστικού των κινητήρων diesel, του θορύβου της καύσης. Η μελέτη του τελευταίου έχει προσελκύσει μεγάλο ενδιαφέρον τα τελευταία χρόνια, ιδιαίτερα στις εφαρμογές οχημάτων, όπου ο θόρυβος σχετίζεται άμεσα με τα επίπεδα άνεσης (όχλησης) των επιβατών και των πεζών. Η διερεύνηση περιλαμβάνει ένα μεγάλο εύρος επιταχύνσεων και αυξήσεων φορτίου ενός υπερπληρωμένου κινητήρα diesel, με το κύριο ενδιαφέρον να επικεντρώνεται στην πρώτη περίπτωση, εφόσον ο κινητήρας προορίζεται για εφαρμογές οχημάτων. Έτσι, εκτελούνται επιταχύνσεις από διάφορες αρχικές συνθήκες (ταχύτητα περιστροφής και φορτίο) αντιπροσωπεύοντας την επιτάχυνση ενός οχήματος με διαφορετική σχέση μετάδοσης στο κιβώτιο ταχυτήτων. Επιπλέον, εκτελούνται κάποιες συνδυασμένες και σύνθετες μεταβολές της ταχύτητας περιστροφής και του φορτίου. Η διερεύνηση επεκτείνεται στη σύγκριση των πραγματικά μετρημένων εκπομπών ρύπων κατά τη μεταβατική λειτουργία με εκείνες των αντίστοιχων μόνιμων συνθηκών (λειτουργία στην ίδια ταχύτητα περιστροφής και θέση κανόνα της αντλίας πετρελαίου), για τον εντοπισμό των διαφορών ανάμεσα στις δύο καταστάσεις. Από τα αποτελέσματα της διερεύνησης αναδεικνύεται η σπουδαιότητα της υστέρησης του υπερπληρωτή (turbocharger lag), ενώ καθίσταται σαφές ότι η μεταβατική λειτουργία του κινητήρα δεν μπορεί να θεωρηθεί ως αλληλουχία σημείων μόνιμης λειτουργίας. Επιπλέον, προσδιορίζεται η επίδραση διαφόρων παραμέτρων (π.χ. ρυθμός επιτάχυνσης, θερμική κατάσταση κινητήρα) στις εκπομπές ρύπων και θορύβου της καύσης κατά την επιτάχυνση του κινητήρα, ενώ αναδεικνύεται ο διαφορετικός μηχανισμός σχηματισμού της αιθάλης σε μεταβατικές συνθήκες, σε σχέση με τις μόνιμες. Ακόμα, διαπιστώνεται μία ποιοτική συσχέτιση ανάμεσα στις εκπομπές NO και θορύβου της καύσης, τόσο κατά τη μόνιμη όσο και κατά τη μεταβατική λειτουργία του κινητήρα. Ακολούθως, μελετάται η τρίτη βασική περίπτωση μεταβατικής λειτουργίας των κινητήρων diesel, η εκκίνηση, η οποία είναι ιδιαίτερα σημαντική στους κινητήρες οχημάτων. Το κύριο ενδιαφέρον επικεντρώνεται στην ψυχρή εκκίνηση, λόγω των έντονων διαφοροποιήσεών της από οποιαδήποτε άλλη κατάσταση λειτουργίας του κινητήρα, ενώ περιλαμβάνονται και εκκινήσεις σε ενδιάμεσες θερμοκρασίες του ψυκτικού μέσου και διάφορες ταχύτητες περιστροφής άφορτης λειτουργίας (“ρελαντί”). Τα αποτελέσματα των πειραματικών μετρήσεων αναδεικνύουν και πάλι τη σπουδαιότητα της υστέρησης του υπερπληρωτή, η επίδραση της οποίας μεταβάλλεται ανάλογα με τις συνθήκες εκκίνησης (ταχύτητα περιστροφής και θερμική κατάσταση κινητήρα). Παράλληλα, φανερώνουν ένα ακόμα πολύ σημαντικό φαινόμενο, την αστάθεια της καύσης, η οποία είναι εντονότερη κατά την ψυχρή εκκίνηση. Επιπλέον, επισημαίνονται αφενός, οι υπερβολικά υψηλές εκπομπές αιθάλης και αφετέρου, η σημαντικότητα της μελέτης των εκπομπών NO κατά την (ψυχρή) εκκίνηση του κινητήρα. Στη συνέχεια, η διερεύνηση επεκτείνεται στην εξέταση της επίδρασης του τύπου του καυσίμου στις εκπομπές ρύπων και θορύβου της καύσης κατά τη μεταβατική λειτουργία του κινητήρα. Για το σκοπό αυτό πραγματοποιούνται διάφορες επιταχύνσεις και μία εκκίνηση με μίγματα του πετρελαίου με βιοντήζελ ή βουτανόλη. Τα αποτελέσματα των πειραματικών μετρήσεων δείχνουν ότι κατά την επιτάχυνση του κινητήρα, τα δύο συγκεκριμένα καύσιμα έχουν ευνοϊκή επίδραση στις εκπομπές αιθάλης, με παράλληλη αύξηση των εκπομπών NO, ενώ οι εκπομπές του θορύβου της καύσης διαφοροποιούνται μόνο για το μίγμα της βουτανόλης. Ωστόσο, κατά την εκκίνηση του κινητήρα, το μίγμα του βιοντήζελ αυξάνει τις εκπομπές αιθάλης, ενώ για το μίγμα της βουτανόλης παρατηρούνται οι ίδιες τάσεις με την προηγούμενη περίπτωση μεταβατικής λειτουργίας. Τέλος, μετά την ολοκλήρωση της πειραματικής διερεύνησης, εφαρμόζεται ένας κώδικας προσομοίωσης της μεταβατικής λειτουργίας κινητήρων diesel που περιλαμβάνει την εκτίμηση των εκπομπών ρύπων. Ο κώδικας συντίθεται από μοντέλα και κώδικες που έχουν αναπτυχθεί σε άλλες εργασίες και διατριβές εντός του εργαστηρίου Μ.Ε.Κ. του Ε.Μ.Π., με σκοπό την προκαταρκτική αξιολόγηση των εκτιμήσεών του.The current PhD thesis deals with the transient operation of turbocharged diesel engines, focusing on pollutant emissions and combustion noise radiation. Transient operation constitutes an extremely important operating condition, owing to its differentiations compared to steady-state operation, as well as due to its large contribution to the engine’s total emissions. The relevant phenomena are more prominent in vehicles engines (e.g. buses, trucks), whose operation is almost exclusively transient. The basic target of the current PhD thesis is the evaluation and interpretation of pollutant emissions and combustion noise radiation during transient operation, by studying the respective phenomena. Understanding the conditions under which high levels of pollutants and combustion noise are generated, constitutes the base for the development of systems and methods which are intended to their control. Thus, the current PhD thesis aims at a thorough examination of the mechanisms and phenomena taking place during transient operation of turbocharged diesel engines, as well as at pointing out the substantial differences compared to the respective steady-state conditions. The investigation is conducted on an experimental basis. The tests are realized on the test bed of a six-cylinder turbocharged diesel engine, which is installed in the Internal Combustion Engines (ICE) Laboratory of the National Technical University of Athens (NTUA). The specific engine is widely applied on vehicles (buses, trucks), a fact that renders it an ideal choice for the study of transient operation. A plethora of measuring devices is installed on the engine, in order to record continuously its basic operating parameters. Moreover, ultra-fast response exhaust gas analyzers are used, which are especially designed for transient measurements in internal combustion engines. In that way, continuous measurement of pollutant emissions is possible. The investigation concerns initially the two basic pollutants of diesel engines, namely nitric oxide (NO) and soot. The well established “trade-off” between these two pollutants, makes extremely important their combined examination during transient operation. Moreover, the investigation expands on another very important (but often neglected) diesel engine characteristic, namely combustion noise. During the last years, the study of combustion noise has attracted much attention, especially at vehicle applications, where noise is related to passengers and pedestrians discomfort. The investigation of the current PhD thesis includes a wide range of accelerations and load increases of a turbocharged diesel engine, with the main focus being on the former case, as the engine is intended for vehicle applications. Thus, a large number of acceleration tests are conducted, commencing from various initial conditions (engine speed and load), mimicking real vehicle acceleration under different gear in the gearbox. Additionally, some combined and complex speed and load transients are conducted, as parts of the legislated Transient Cycles. The investigation also includes a quasi-steady approximation of really measured pollutant emissions and combustion noise radiation with their respective values under steady-state conditions (operation at the same engine speed and fuel pump rack position). This methodology is applied in order to point out the substantial differences between steady-state and transient operation of a turbocharged diesel engine. The results of these tests make prominent the importance of turbocharger lag, the most notable phenomenon during turbocharged diesel engine transient operation. Moreover, it is made clear that turbocharged diesel engine transient operation can not be considered as a series of steady-state operating points. Additionally, the effect of various parameters (e.g. acceleration rate, engine thermal status) on pollutant emissions and combustion noise radiation is established. Also, the completely different soot formation mechanism between steady-state and transient operation is pointed out. Finally, a qualitative correlation between NO emissions and combustion noise radiation is revealed, at both steady-state and transient conditions. Afterwards, the third basic case of diesel engine transient operation is studied, namely starting, which is very important in vehicle applications. The main focus is on cold starting, owing to its great differentiations compared with any other operating condition of the engine. However, other starting tests are also included in the investigation, which are conducted at different coolant temperatures (engine thermal status) and idling speeds. The results of the starting tests make, once more, prominent the turbocharger lag phenomenon, the effect of which is varied according to the starting conditions (idling speed and engine thermal status). Additionally, another important phenomenon is revealed, namely combustion instability, which is more intense during cold starting. Concerning pollutant emissions, extremely high values of exhaust gas opacity are observed combined with high NO concentrations. Thus, contrary to the common belief, it is made clear that it is very important to study NO emissions during (cold) starting. Next, the investigation expands on the study of the effect of the fuel type on pollutant emissions and combustion noise radiation during diesel engine transient operation. To that aim, various acceleration tests as well as a starting one are conducted with the engine running on blends of diesel with biodiesel or n-butanol. The results of the experimental measurements show that during engine acceleration, these two specific blends have a positive effect on soot emissions, while an increase in NO emissions is observed. At the same time, combustion noise radiation is affected only by the n-butanol blend. However, during starting, biodiesel blend causes an increase in soot emissions, while the trends for the n-butanol blend are the same as with the previous transient case (i.e. acceleration). Finally, after completing the experimental investigation, a simulation code is applied. This code concerns diesel engine transient operation and includes pollutant emissions estimation. The final code is composed by two already existing codes, developed during other dissertations in the ICE laboratory of NTUA. The scope of its application is the preliminary evaluation of its estimations concerning pollutant emissions.Αθανάσιος Μ. Δημάρατο

Impact of Active Diesel Particulate Filter Regeneration on Carbon Dioxide, Nitrogen Oxides and Particle Number Emissions from Euro 5 and 6 Vehicles under Laboratory Testing and Real-World Driving

Particulate mass concentration is a crucial parameter for characterising air quality. The diesel particulate filter (DPF) is the primary technology used to limit vehicle particle emissions, but it needs periodic cleaning, a process called regeneration. This study aims to assess the impact of active DPF regeneration on the performance and emissions of Euro 5 and 6 vehicles. The study examined both carbon dioxide (CO2) and pollutant (nitrogen oxides (NOx) and particle number (PN)) emissions for eight vehicles tested in the laboratory and on the road. Apart from the DPF, a wide range of emission control systems was covered in this experimental campaign, including exhaust gas recirculation (EGR), diesel oxidation catalyst (DOC), lean NOx trap (LNT) and selective catalytic reduction (SCR) catalyst, revealing the different impacts on NOx emissions. The regeneration frequency and duration were also determined and used to calculate the Ki factor, which accounts for the emissions with and without regeneration, weighted over the distance driven between two consecutive regeneration events. Based on these outcomes, representative emission factors (EF) were proposed for the regeneration phase only and the complete regeneration interval. In addition, the effect of regeneration on efficiency was estimated and compared with other energy consumers. The results indicated a significant impact of DPF regeneration on CO2, NOx and PN emissions, higher in the case of driving cycle testing in the laboratory. The relevant mechanisms behind the elevated emission levels were analysed, focusing on the regeneration period and the test phase following immediately after. The calculation of the Ki factor and the comparison with the official values revealed some weaknesses in its application in real-world conditions; to overcome these, new NOx EF values were calculated, depending on the emission control system. It was revealed that Euro 6 vehicles equipped with SCR could comply with the applicable limits when considering the complete regeneration interval. Finally, it was indicated that the DPF regeneration impact on vehicle efficiency is similar to that of driving with the air conditioning (A/C) system and headlights on

Evaluation of a Hydrotreated Vegetable Oil (HVO) and Effects on Emissions of a Passenger Car Diesel Engine

In the coming years, the application of paraffinic biofuels, such as Hydrotreated Vegetable Oils (HVO), in the transportation sector is expected to increase. However, as the composition of HVO is different compared to conventional diesel, the engine optimized for conventional fuel cannot take full advantage of the HVO beneficial properties. Suitable adjustment of a number of engine parameters, if not complete engine re-calibration, will enable the full exploitation of such fuels' potential for lower exhaust emissions and reduced fuel consumption. In the present work, the emission characteristics of HVO fuel in a light-duty Euro 5 diesel engine have been studied, under steady-state operation, as well as during the New European Driving Cycle (NEDC). The study was expanded to the investigation of exhaust emissions under modified Main Injection Timing (MIT) and EGR rate. The NEXBTL fuel, produced by Neste, was considered in the study and was compared with conventional market diesel. Emissions of nitric oxides (NOx), soot, carbon monoxide (CO), carbon dioxide (CO2), and hydrocarbons (HC) were studied. At default MIT and EGR settings the use of HVO resulted in a significant reduction of all regulated emissions. In addition, it was observed that the adjustment of MIT and EGR can enhance the exploitation of HVO potential for emissions reduction, highlighting the differences with the conventional diesel fuel

Fuel consumption and CO2 emissions of passenger cars over the New Worldwide Harmonized Test Protocol

In 2014 the United Nations Economic Commission for Europe (UNECE) adopted the global technical regulation No. 15 concerning the Worldwide harmonized Light duty Test Procedure (WTLP). Having significantly contributed to its development, the European Commission is now aiming at introducing the new test procedure in the European type-approval legislation for light duty vehicles in order to replace the New European Driving Cycle (NEDC) as the certification test. The current paper aims to assess the effect of WLTP introduction on the reported CO2 emissions from passenger cars presently measured under the New European Driving Cycle and the corresponding test protocol. The most important differences between the two testing procedures, apart from the kinematic characteristics of the respective driving cycles, is the determination of the vehicle inertia and driving resistance, the gear shifting sequence, the soak and test temperature and the post-test charge balance correction applied to WLTP. In order to quantify and analyze the effect of these differences in the end value of CO2 emissions, WLTP and NEDC CO2 emission measurements were performed on 20 vehicles, covering almost the whole European market. WLTP CO2 values range from 125.5 to 217.9 g/km, NEDC values range from 105.4 to 213.2 g/km and the ΔCO2 between WLTP and NEDC ranges from 4.7 to 29.2 g/km for the given vehicle sample. The average cold start effect over WLTP was found 6.1 g/km, while for NEDC it was found 12.3 g/km. For a small gasoline and a medium sized diesel passenger car, the different inertia mass and driving resistance is responsible 63% and 81% of the observed ΔCO2 between these two driving cycles respectively, whereas the other parameters (driving profile, gear shifting, test temperature) account for the remaining 37% and 19%.JRC.C.4-Sustainable Transpor