Search

Background Sacubitril/valsartan has been proved to reduce mortality in heart failure and reduced ejection fraction (EF) and is currently recommended as first-line therapy. However, effects in patients with a systemic right ventricle (sRV) have not been systematically investigated yet. Purpose We aimed to assess safety and efficacy of sacubitril/valsartan in patients with a sRV Methods From September 2020 to April 2021, all patients with congenitally corrected transposition of the great arteries (TGA) or TGA after Senning/Mustard repair attending our tertiary centre were prospectively enrolled. Inclusion criteria were: age ≥18 years, 3-months of optimal medical therapy including ACEi/ARB and sRV EF≤40%. Patients with univentricular physiology, systolic blood pressure (SBP) 5.5 mEq/L were excluded. SBP and blood samples were obtained at 1-month of treatment. Other clinical and echocardiographic variables were reassessed at 6 and 12-month follow-up and the medication was progressively up-titrated to the highest tolerated dose. Results Fifty-one patients (38±11 years, 60% male, 34% ccTGA) were included. Up to March 2022, 48 (92%) patients were reviewed after 6 months of therapy and 35 (68%) completed the first year of follow-up. Baseline patients' characteristics are summarized in Table 1. At 1 month, treatment did not impact on the serum potassium values (4.5±0.3 vs 4.4±0.3 mEq/L, p=0.9) and GFR (112±33 vs 112±31 ml/min, p=0.3), while SBP dropped significantly (119±13 vs 108±18 mmHg, p=0.003). Two patients ceased the treatment due to symptomatic hypotension during the first month. One patient developed a nephrotic syndrome at 4 months of follow-up, which was likely unrelated to the treatment. No other major adverse events were reported. One patient was lost to follow-up after 3 months. Despite no significant change in the NYHA class (p=0.9), the 6-minute walking distance increased significantly at 6-month (Table 2). Nt pro BNP values were significantly decreased at 6-month, and returned to baseline at 12-month. Improved sRV systolic function was demonstrated at 6 and 12-month by significant increase in fractional area change, RV global longitudinal strain and sRV EF measured with 3D echocardiography. Conclusions Our mid-term results showed that sacubitril/valsartan is well tolerated in patients with a sRV and leads to signficant improvement of sRV systolic function, supporting its use in this complex population. Funding Acknowledgement Type of funding sources: None.

Background Wolf-Parkinson-White Syndrome (WPW) has been associated with reduced local myocardium deformation during systole. According to guidelines, when the left ventricle (LV) dysfunction is present catheter ablation of the accessory pathway may be required, even in asymptomatic patients. Purpose The study aimed to assess the diagnostic value of non-invasive myocardial work in predicting subtle myocardial abnormalities in children with WPW. Methods Eighty pediatric patients (age 7.91±3.2 years) were included in the study: 20 cases with manifest WPW and 60 age- and sex-matched controls (CTR). Global myocardial work index (MWI) was measured as the area of the LV pressure-strain loops. From MWI, global Constructive Work (MCW), Wasted Work (MWW) and Work Efficiency (MWE) were estimated. In addition, standard echocardiographic parameters of LV function were evaluated. Results Patients characteristics are summarized in the table. Despite normal LV EF and GLS, children with WPW had worse MWI (WPW 1292.90±307.67 mmHg% vs CTR 1658.73±241.74 mmHg%, p=0.0000005), MCW (WPW 1844.15±267.96 mmHg% vs CTR 2104.90±237.85 mmHg%, p=0.00009), MWW (WPW 101.5 [85–148.25] mmHg% vs CTR 72 [54.75–109.25] mmHg%, p=0.004) and GWE (WPW 94 [91.75–95] mmHg% vs 96 [95–97] mmHg%, p=0.00012) (table). In the WPW group, MWE (r=−0.6, p=0.009) and MWW (r=0.6, p=0.01) was found to correlate with a prolonged QRS (figure). A multiple regression model was generated to identify the relation between abnormal myocardial work indices (worst interquartile range as dependent variable) and several independent variables. QRS was the best independent predictor of impaired myocardial work. In particular, a QRS>110 msec showed an 86% sensibility and 85% specificity for abnormal MWE (AUC of 0.85), and a 75% sensibility and 83% specificity for abnormal MWW (AUC of 0.83) (figure). Conclusion In children with WPW, myocardial work indices were found significantly reduced, even in presence of normal LV EF and GLS. Prolonged QRS independently predicted myocardial impairment. In pediatric patients with WPW, myocardial work may represent a sensitive measure of LV dysfunction and help in the decision-making. Funding Acknowledgement Type of funding sources: None.

Background Adults with congenital heart disease (ACHD) are a vulnerable population. Routine vaccination is the only strategy to prevent a life-threatening infection. However, concerns on the cardiac safety and efficacy of COVID-19 vaccines have been raised. Aim To assess safety and efficacy of available COVID-19 vaccines in ACHD patients. Methods Data on COVID-19 infection and vaccines including booster doses and any suspected or confirmed adverse events were prospectively collected for all ACHD patients attending our tertiary centre from the beginning of the vaccination campaign (March 2021). A group of 75 healthy volunteers, matched per age and sex, was included for comparison. Antispike IgG titre was routinely obtained at the ACHD clinic. Patients' attitude towards COVID-19 was explored with a questionnaire. Results As of February 2022, 498 ACHD patients (36.7±16 years, 54% male,69% with moderate-complex defects, 48% with advanced physiological stage) were enrolled. Four hundred and sixty-one (92%) were fully vaccinated: the type of vaccine was Pfizer-BioNTech for 399 (86%) patients, Moderna for 20 (4%) and AstraZeneca for 26 (6%), 9 received a mixed vaccine regimen (2%). Forty-two (9%) had a history of previous COVID-19 infection and therefore received only one dose. Two-hundred and sixty-nine (58%) patients received a booster dose. Adverse events were mainly mild and transient. One patient complaining of chest pain following administration of mRNA-based vaccination was diagnosed with acute pericarditis, which made full remission after appropriate therapy. Two patients reported a non-specific increment of inflammatory markers. No other severe adverse events were reported. Thirty-seven (7%) refused COVID-19 vaccination being scared of potential cardiac/extra-cardiac adverse events. Among those not-vaccinated, 9 (24%) had a history of previous mild COVID-19 infection. IgG titre was measured in 243 patients at 1915 [835–5934] BAU/ml, which was significantly higher compared to controls (1196 [827–2048] BAU/ml, p=0.002). Three ACHD patients contracted COVID-19 infection after the first dose, while 65 (14%) fully vaccinated patients tested positive for COVID-19, all with mild to moderate symptoms. COVID-19 symptoms duration was significantly longer in case of infection before vaccination (10 [2.7–15] vs 3 [1.2–7], p=0.03). One Fontan patient was tested positive for COVID-19 twice, before and after COVID-19 vaccination, requiring hospitalization in both cases. Four hundred and seven patients completed the questionnaire: 128 (31%) declared to be scared of potential cardiac effects of the vaccine and that the discussion with the ACHD cardiologist was crucial to decide to undergo COVID-19 vaccination. Conclusions Our data provide real-world evidence on COVID-19 vaccines safety and efficacy in ACHD patients. Patients' education from the ACHD team may play a key role in vaccine acceptance in this vulnerable population. Funding Acknowledgement Type of funding sources: None.

Funding Acknowledgements Type of funding sources: None. Background Blood speckle imaging (BSI) is a new speckle-tracking-based technique for the evaluation of blood flow. Ventricular flow vortices have been studied in sinus rhythm in normal and dysfunctional hearts, however, data are lacking in patients with Kent accessory pathway (KAP) and short atrio-ventricular (AV) conduction. Purpose We aimed to evaluate the characteristics of left ventricle blood vortices in children with KAP. Methods Nineteen paediatric patients (age 7 ± 2.9 years) were included in the study: 13 patients with manifest KAP (KAP group) and 6 age and sex -matched controls with normal AV conduction (CTR group). A thorough echocardiographic evaluation with 2D, color doppler and BSI was performed in all the included patients. BSI was recorded in apical 3-chamber view with a 6S-D probe. Vortices characteristic were analysed during filling phase of the left ventricle. We focused on the anterior vortex generated by mitral valve, which persisted longer during the cardiac cycle and is assumed to contribute to optimizing cardiac function. A standard 12-lead ECG was also recorded for each child in KAP group to esteem KAP localization. Results According to Arruda criteria for KAP localization, all patients in KAP group manifested the accessory pathway in the septal region. All patients in CTR group presented one major anterior vortex during filling phase, while in KAP group 10 patients out of 13 (p= 0.009) lacked of this main anterior vortex, showing instead fragmented different vortices. There were no differences in term of left ventricle function (KAPg 59.8 ± 4.02% vs CTRg 59.0 ± 2.5%, p= 0.6) and global longitudinal strain (KAPg -18.6 ± 1.0% vs CTRg -19.6 ± 3.1%, p= 0.5) between the two groups. Conclusion In our preliminary analysis, in patients with septal KAP, blood vortices adapted their diastolic traces to the septal dyssynchrony showing a fragmented pattern. We speculate this fragmentation may contribute to impair the performance of the left ventricle. Abstract Figure. BSI in control vs patient with WPW

Funding Acknowledgements Type of funding sources: None. Background Wolff-Parkinson-White Syndrome (WPW) has been associated with reduced local myocardium deformation during systole. Left ventricle (LV) dysfunction due to electrical dyssynchrony may require catheter ablation of the accessory pathway, even in asymptomatic patients. Purpose The study aimed to assess the diagnostic value of non-invasive myocardial work in predicting subtle myocardial abnormalities in patients with WPW. Methods Forty-four paediatric patients (age 8.2 ± 4.3 years) were included in the study: 12 cases with manifest WPW and 32 age-, sex- and arterial pressure- matched controls (CTR). LV ejection fraction (EF) and global longitudinal strain (GLS) were evaluated. Global myocardial work index (MWI) was measured as the area of the LV pressure-strain loops. From MWI, global Constructive Work (MCW), Wasted Work (MWW) and Work Efficiency (MWE) were estimated. Results Despite normal LV systolic function by standard echocardiographic parameters, patients with WPW had lower MWI (1233.5 ± 281.6 mmHg% in WPW vs 1624.0 ± 305.8 mmHg% in CTR, p = 0.0004), MCW (1833.4 ± 257.9 mmHg% in WPW vs 2069.0 ± 319.9 mmHg% in CTR, p= 0.03), MWW (187.6 ± 117.7 mmHg% in WPW vs 90.9 ± 58.9 mmHg% in CTR, p= 0.0008) and GWE (90.5 ± 4.8% in WPW vs 95.2 ± 2.2% in CTR, p= 0.00006). There were no significant differences in GLS and EF between patients with WPW and controls. Conclusion Myocardial work indices were found significantly reduced in patients with WPW, even in presence of normal LV EF and GLS. In patients with WPW, MWI may represent a sensitive measure of myocardial dysfunction and help in the decision-making for catheter ablation. Abstract Figure. Myocardial work in WPW Abstract Figure. Myocardial work in control patient

Funding Acknowledgements Type of funding sources: None. Background Adults with coarctation of the aorta (CoA) may present residual aortic obstruction and develop arterial vasculopathy and subclinical left ventricular (LV) dysfunction. Myocardial work (MW) is a novel non-invasive index of myocardial efficiency calculated from echocardiographic LV pressure-strain loops, which yields incremental information over ejection fraction and global longitudinal strain. (GLS) Purpose Aim of the present study is to analyze LVMW in a cohort of adult patients with operated aortic CoA Methods CoA patients aged > 18 years who underwent transthoracic echocardiography between September 2020 and July 2021 at our tertiary centre were included. Exclusion criteria were significant recoarctation, impaired LVEF, significant valvular disease and suboptimal image quality. A group of healthy individuals with no cardiac abnormalities. GLS and peak strain dispersion(PSD) were measured. MW indices were calculated using the blood pressure measured in the right arm at the time of the exam. Results Sixty patients (26[22-33]years, 66%male) were included. Data on previous medical history, clinical status at last assessment and Coa-related echocardiographic findings are showed in table 1. No significant differences in traditional parameters of LV systolic and diastolic function were found between groups (EF 60[57-64] vs 57[53-61],p = 0.6), however Coa patients had higher LVmass (84[75-97] vs 68[56-75]g). GLS and MW indices in the study population and in the control group are reported in table 2. Coa group showed lower GLS values and higher PSD (p 0.0001). Conclusion MW indices assessment is feasible in Coa patients may provide a more comprehensive understanding of the overall myocardial mechanics and performance. In particular, MW demonstrated impaired LV efficiency, which was strongly related to increased mechanical dispersion in Coa patients. Abstract Figure. Abstract Figure.

Background Sacubitril/valsartan has been shown to reduce mortality and morbidity inpatients with heart failure and reduced systolic function. However, the effects of this novel association in patients with congenital heart disease and a systemic right ventricle (sRV) have not been investigated yet. Purpose We aimed to assess tolerability and efficacy of sacubitril/valsartan in patients with a sRV Methods From September 2020 to March 2021, 38 patients with congenitally corrected transposition of the great arteries or transposition of the great arteries after Senning or Mustard repair were prospectively enrolled. Inclusion criteria were: age ≥18 years, optimal medical therapy including ACEi/ARB for at least 6 months and EF of the sRV ≤40%. Patients with univentricular physiology, systolic blood pressure (SBP) 5.5mEq/L were excluded. RV systolic function was assessed on echocardiography using a multiparametric evaluation. The study protocol contemplates serial assessments at 1, 3, 6 and 12 months after treatment initiation. Results Up to March 31th, 23 patients completed 1-month and 15 completed 3-month assessment after treatment initiation. Baseline patients' characteristics are summarized in table 1. The medication dose was up-titrated to the highest tolerated dose during follow-up. During early follow-up, no major adverse events were reported. Treatment did not impact significantly on the values of serum potassium (basal K+ 4.4 [4.2–4.6] mEq/L, K+ at 3 months 4.4 [4.3–4.6] mEq/L, p=0.7) and GFR (basal GFR 113.9±35ml/min, GFR at 3 months 107.8±21 ml/min, p=0.7). Although SBP did not change significantly (114±12 vs 113.9±19 mmHg at 1-month and 117.3±12 mmHg at 3 months; p=0.9 for both), 2 (5%) patients ceased the treatment due to symptomatic hypotension during the first month of treatment. There was no significant change in the NYHA class. However, the 6-minute walking distance increased significantly after 3 months (365±120 vs 498.3±71 min; p=0.01). Furthermore, while traditional echocardiographic parameters of RV systolic function (TAPSE, s wave and FAC) did not change significantly, RV global longitudinal strain (GLS) and RV free wall GLS demonstrated subclinical improvement in right ventricular systolic function (table 2). Conclusions Our short-term results from an ongoing prospective study showed that sacubitril/valsartan is well tolerated in patients with a sRV with early evidence of improvement in exercise tolerance and sRV systolic function. Longer follow-up is warranted to confirm these data. Funding Acknowledgement Type of funding sources: None. Table 1Table 2

Background Adults with congenital heart disease (ACHD) are frequently affected by thyroid diseases (TD). However, the clinical relevance of TD in ACHD remains unknown. Purpose We aimed to describe the prevalence of TD in the ACHD population and to ascertain whether TD are associated with worse outcome. Methods Clinical data on all consecutive patients aged >18 years attending our ACHD unit for a day-case between 2014 and 2019 were retrospectively collected. For statistical analysis, a composite endpoint was created combining the following events at follow-up: hospitalization for heart failure, new-onset tachyarrhythmic or bradyarrhythmic events and death. Results Four hundred ninety-five ACHD patients with a median age of 32.2 [24.5–45.6] years (46% male) were included. There was an overall prevalence of patients with moderate or complex lesions (414=84%). Compared to the group with no history of TD, patients in the TD were older, (41.9 [29.7–53.5] vs 30.2 [24.3–39] years; p Median follow-up was 9.4 [4.5–13.1] years. Patients with TD had a higher unadjusted mortality rate, with a trend towards statistical significance (p=0.07). Sixty-four (42%) patients in the TD group and 43 (12.5%) met our composite endpoint, leading to a 10-year survival free from events of 53.7% Vs 86.5%, respectively (p Conclusion TD is a strong predictor of adverse outcome in the ACHD population after exclusion of potential confounding factors, being related to a fourfold increased risk of events at follow-up. Funding Acknowledgement Type of funding sources: None. Figure 1Table 1

Nowadays internal combustion engines can operate under lean combustion conditions to maximize efficiency, as long as combustion stability is guaranteed. The robustness of combustion initiation is one of the main issues of actual spark-ignition engines, especially at high level of excess-air or dilution. The enhancement of the in-cylinder global motion and local turbulence is an effective way to increase the flame velocity. During the ignition process, the excessive charge motion can hinder the spark discharge and eventually cause a misfire. In this perspective, the interaction between the igniter and the flow field is a fundamental aspect which still needs to be explored in more detail to understand how the combustion originates and develops. In this work, a combined experimental and numerical study is carried out to investigate the flow field around the spark gap, and its effect on the spark discharge evolution. Two different velocities of the flow field are explored and compared to the static configuration under ambient conditions in an air flow channel, investigating the effect of the orientation of a conventional J-type spark plug. Results of numerical simulations predict spark stretching that is in close agreement with experimental observations. The model results are used to provide insight into the spatial and temporal development of the spark discharge. This work provides a numerical tool that can be extremely useful to link the interaction between the in-cylinder charge motion and the spark discharge to the engine cycle-to-cycle variability prediction.

A dielectric barrier discharge igniter (BDI) ensures engine stable combustion at lean and/or diluted conditions by the generation of non-equilibrium low-temperature plasma (LTP), strong promoter of the ignition, in a wide mixture volume. Beside this, a substantial amount of thermal energy is also released in the medium to enhance the chemical reactions of fuel oxidation. Therefore, the measurement of thermal energy is crucial to characterize the igniter capability to guarantee a robust combustion onset and it can be performed only in controlled environments. In this work, a Radio-Frequency BDI was tested via pressure-based calorimetry by evaluating the thermal energy released during the discharge in a controlled environment represented by a constant volume vessel. The corresponding thermal efficiency was evaluated as well. Pure nitrogen and air were exploited at engine-relevant pressure levels by varying the discharge features as its time duration and intensity (the latter by peak electrode voltage variation), to fully characterize the igniter behavior. Both media showed similar trends of absorbed and released energy but differences up to 50% were found for the latter. This trend was found to be linear, unexpectedly in contrast to the quadratic one showed by the LTP corona streamer-type igniter (CSI). Furthermore, the thermal energy dependence from pressure showed a change up to complete independence at a specific electrode value. To provide an explanation for such different behaviors, a comparative analysis between the diverse discharges of the two igniters was carried out. Moreover, by varying voltage and duration, the device was found to be able to release up to 60 mJ in the tested point with very low dispersion, essential to guarantee stable combustion ignition at challenging operating conditions for next-generation internal combustion engines.

Currently, the Radio-Frequency Corona Ignition systems represent an important solution for reducing pollutant emissions and fuel consumption related to Internal Combustion Engines while at the same time ensuring high performance. These igniters are able to extend the lean stable limit by increasing the early flame growth speed. Kinetic, thermal and ionic effects, together with the peculiar configuration of the devices, allow to start the combustion process in a wider region than the one involved by the traditional spark. In this work two corona igniters, namely a Barrier Discharge Igniter and a Corona Streamer Igniter, were tested in a single-cylinder research engine fueled with gasoline at different engine loads in order to investigate the igniters performance through indicated analysis and pollutant emissions analysis. For each operating point, the devices control parameters have been set to ensure maximum energy releasement into the medium with the aim of investigating, at the extreme operating conditions, the capability of the devices to extend the lean stable limit of the engine. The Corona igniters have been tested on a constant volume calorimeter as well, reproducing the engine pressure conditions at the corresponding ignition timing. The target is to give an estimation of the thermal energy released during the discharge and then to compare their capability to provide high-stability energy.

Polyethyleneimine (PEI) has been used extensively for transient gene expression (TGE) in mammalian cell cultures. However, the relationship between DNA/PEI complex preparation and their biological activity has not been fully established. Here, a systematic study of DNA/PEI complexes, their physicochemical properties during formation and their transfection efficiency was performed on a virus-like particle (VLP) production platform. The same chemically defined cell culture medium for DNA/PEI complex formation was used as an alternative to simple ionic solutions to minimize changes in complex properties during transfection. Upon formation, an initial concentration of 1E + 10 DNA/PEI complexes/mL underwent partial aggregation with an average size of 300 nm. The participation of NaCl ions in the evolution of complexes was analyzed by X-ray spectroscopy, stressing the relevance of complexing media composition in TGE strategies. After 15 min incubation, 250 complexes plus aggregates per cell were estimated at the time of transfection. Such heterogeneous preparations cannot be easily characterized; subsequently, nanoparticle tracking analysis (NTA) and cryo-electron microscopy were combined to achieve a complete picture of the preparation. Finally, the contribution of each DNA/PEI complex subpopulation was tested by drug inhibition endocytosis. Interestingly, all complexes delivered DNA efficiently and high size aggregates, which enter through macropinocytosis, when inhibited presented a major contribution to transfection efficiency. There is a need to understand the physicochemical factors that participate in DNA delivery protocols. Hence, this study provides new insights into the characterization of DNA/PEI complexes that will assist in more productive and reproducible TGE strategies., This work was financially supported by MINECO (SIDI), Spain, grants MOTHER MAT2016-80826-R, by AGAUR, Generalitat de Catalunya, Grant 2014 SGR 17, 2014 SGR 1216 and 2017 SGR 898 and by the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centers of Excellence in R&D (SEV- 2015-0496). ICTS “Nanobiosis”, more specifically by the U6 Unit of CIBER-BBN is also acknowledged.

Charging a motorcycle engine is challenging, since requirements of lightness, system simplicity and engine responsiveness are key factors. This paper reports on a preliminary study on a pressure wave compressor, the “Impulse Drum Charger”. Performances of a 4-stroke motorcycle engine with and without Drum Charger were compared at the test bench and a pressure analysis in the intake manifold was carried out as well. Results show that this system is able to effectively improve engine power (up to 1.4 kW at 9500 rpm WOT) without an ECU recalibration.

The Radio-Frequency Corona Ignition System is characterised by a wide initial combustion volume and precursors production, via radical insemination by the streamers, in addition to high released thermal energy. These features lead to faster combustion, a higher tolerance for lean mixtures and EGR dilutions and, in general, more adaptability. The thermal energy released by the igniter to the surrounding medium can help to understand the performance, the behaviour and the application range. This paper proposes a systematic experimental analysis of the thermal energy released by the igniter at room temperature, via pressure-based calorimetry. This analysis, carried out at different pressures (up to 10 bar) and medium type (air or nitrogen), is extended to the whole range of the corona igniter control parameters, namely streamer duration and driving voltage. The latter is proportional to the maximum electrode voltage, as shown in the model here presented, and as confirmed by experiments. The results show, for all the vessel pressures, the high energetic efficiency of the ignition system and the high amount of the released energy. The latter is found to increase linearly with the corona streamers duration and quickly with the driving voltage up to the streamer-to-arc transition threshold. The efficiency tends to reach a defined upper limit. For each tested point, the energy released to pure nitrogen is higher than to air, which evidences the impact of the oxygen presence under streamer exposure.

In recent years, radio-frequency corona igniters have been extensively studied for their capability to ensure an effective ignition also in lean or diluted mixtures. Corona ignition is volumetric, with streamers coming from a star-shaped electrode. During the discharge, many radicals and excited species, able to speed up the combustion onset, are generated. At the same time, corona igniters are able to release a considerable amount of thermal energy inside the combustion chamber. The correct determination of such energy is crucial to evaluate the effectiveness of the ignition. In this work, corona discharge is experimentally evaluated inside an optical vessel. In this apparatus, the released thermal energy is measured by means of pressure-based calorimetry, and at the same time the natural luminosity of the streamers is recorded with a high-speed camera. The goal is to find a relationship between thermal energy release and streamers luminosity. Tests are performed using nitrogen as medium, at different pressure levels inside the vessel. The peak electrode voltage is varied to characterize the igniter behaviour in different operating conditions. The results of this work can be used to quantify the corona ignition capabilities to involve a wide amount of medium while releasing a high amount of thermal energy. A repeatability evaluation of streamer evolution is investigated as well.

Low-temperature plasma (LTP) ignition concepts rely on the production of radical and charged species to speed up the onset of combustion in spark-ignition engines. These features are responsible for the superior performance of LTP igniters under extremely dilute combustion operation that is not achievable by conventional spark igniters. Additionally, LTP discharges extend the lifetime of the igniters, due to the avoidance of spark processes. For these reasons, the engine research community and the automotive industry have shown growing interest in this technology in the recent years. As of today, computational fluid-dynamics (CFD) codes typically used by the multi-dimensional engine modeling community do not have reliable models to describe LTP ignition processes. One key missing piece of information is the physical and chemical properties of the plasma and their effect on combustion ignition. Most non-equilibrium plasma simulations reported in literature are based on simplified, canonical geometries, with simple discharge excitation schemes. In this paper we conduct multi-dimensional modeling of the non-equilibrium plasma generated by an application-relevant radio-frequency (RF) corona discharge in air. Three test cases are simulated, characterized by different environmental pressure levels and peak electrode voltage values at room temperature. Streamer penetration, electron number density, atomic oxygen production, and bulk gas temperature distribution in the first 10 sinusoidal pulses are presented and discussed. This model can be used as a key tool for an in-depth understanding of RF-corona discharge for automotive applications and provides the basis for future implementations of dedicated LTP ignition models in CFD codes.

Three-dimensional computational fluid dynamics internal combustion engine simulations that use a simplified combustion model based on the flamelet concept provide acceptable results with minimum computational costs and reasonable running times. Moreover, the simulation can neglect small combustion chamber details such as valve crevices, valve recesses, and piston crevices volume. The missing volumes are usually compensated by changes in the squish volume (i.e., by increasing the clearance height of the model compared to the real engine). This paper documents some of the effects that such an approach would have on the simulated results of the combustion phenomena inside a conventional heavy-duty direct injection compression-ignition engine, which was converted to port fuel injection spark ignition operation. Numerical engine simulations with or without crevice volumes were run using the G-equation combustion model. A proper parameter choice ensured that the numerical results agreed well with the experimental pressure trace and the heat release rate. The results show that including the crevice volume affected the mass of a unburned mixture inside the squish region, which in turn influenced the flame behavior and heat release during late-combustion stages.

Engine research community interest in the Radio-Frequency corona-based ignition systems is currently gaining in importance mainly due to their capability to ensure robust combustion at challenging operating conditions such as very lean mixture and/or high EGR dilution. The benefits of Corona low-temperature plasma foster the early flame development thanks to combustion precursors production and to a more energetic and volumetric discharge, resulting in a larger amount of involved mixture. The corona discharge generates ionizing waves, named streamers, whose temporal and spatial variability in orientation, length and branching can affect the combustion onset and, therefore, the engine cycle-to-cycle variability. In this work, the discharge natural luminosity of a RF corona igniter, characterized by four tips electrodes, was recorded in an optically accessible engine via high-speed camera detection. A preliminary statistical analysis of the spatial and temporal streamer variability was performed by operating in motored conditions. Four different engine speeds and two different loads were explored in order to deeply investigate the streamer behaviour at diverse engine operating conditions. A comparison between a motored and a lean operating condition is also proposed to analyse, at a specific engine speed, the mixture influence on the streamers propagation before the start of the combustion.

The robustness of combustion initiation is one of the main issues of actual spark-ignition engines, especially for highly-diluted or lean mixtures. In this work, the effects on combustion stabilization obtained by the usage of a radio-frequency corona igniter were evaluated on a single-cylinder optical engine. The comparison with a conventional spark igniter was carried out using pure methane fuel and a blend of hydrogen and methane. For each combination of fuel and igniter, the combustion stability was explored at different air–fuel ratios, from stoichiometric conditions to the lean stable limit (up to λ = 2.0 with the corona igniter and the hydrogen-methane mixture). The combustion analysis was carried out by using the synchronized indicating and imaging data. The latter is essential to estimate the contribution of the corona igniter, which was found to be considerable only before the 5% of mass fraction burned. The corona effect igniter, with respect to a conventional spark igniter, was able to extend the lean stable limit of about 0.15 λ units with methane fuel, and about 0.10 λ units with the hydrogen-methane blend in the tested engine point. Early flame analysis confirmed the capability of corona igniter to improve combustion onset speed and to obtain a more stable and repeatable flame kernel. The findings of this study can help for a better implementation of corona ignition with gaseous low-carbon fuels, and in particular to achieve a higher lean limit extension without the drawback of a performance decay given by a substantial hydrogen enrichment.

3D CFD IC engine simulations that use a simplified combustion model based on the flamelets concept can provide acceptable results with minimum computational costs and reasonable running times. More, the simulation can neglect small combustion chamber details such as valve crevices, valve recesses and piston crevices volume. The missing volumes are usually compensated by changes in the squish volume (i.e., by increasing the clearance height of the model compared to the real engine). This paper documents some of the effects that such an approach would have on the simulated results of the combustion phenomena inside a conventional heavy-duty direct-injection CI engine, which was converted to port-fuel injection SI operation. 3D IC engine simulations with or without crevice volumes were run using the G-equation combustion model. A proper parameter choice ensured that the simulation results agreed well with the experimental pressure trace. The results show that including the crevice volume affected the mass of unburned mixture inside the squish region, which in turn influenced the flame behavior and heat release during late-combustion stages.

Water injection in highly boosted gasoline direct injection (GDI) engines has become an attractive area over the last few years as a way of increasing efficiency, enhancing performance and reducing emissions. The technology and its effects are not new, but current gasoline engine trends for passenger vehicles have several motivations for adopting this technology today. Water injection enables higher compression ratios, optimal spark timing and elimination of fuel enrichment at high load, and possibly replacement of EGR. Physically, water reduces charge temperature by evaporation, dilutes combustion, and varies the specific heat ratio of the working fluid, with complex effects. Several of these mutually intertwined aspects are investigated in this paper through computational fluid dynamics (CFD) simulations, focusing on a turbo-charged GDI engine with port water injection (PWI). Different strategies for water injection timing, pressure and spray targeting are investigated. Two combustion modeling approaches are used and compared, the perfectly stirred reactor model with reduced chemical kinetics for a TPRF surrogate, and the G-equation turbulent combustion model. Combustion rate results are validated against available experimental engine data, in regular and knocking conditions. Multi-cycle simulations are required because of the wall film dynamics, and therefore have been performed to assess the effect of water injection strategies. The results of the study are an assessment of the optimal injection parameters, in terms of injector location, injection timing and primary atomization quality, for achieving the maximum effectiveness of water injection. Knock occurrences are in very good agreement with the experimental data and its suppression is demonstrated through the injection of water at a ratio of 30% to the fuel mass.

In recent decades, the increasingly tight emissions regulations, along with the ever-increasing price of fuels and the request for more power from the engines, has pushed the world car industry to improve the performances of the applications of electronics, designed to control the internal combustion engines (ICE) and the pollutant emissions systems. At present, one of the main problems, in the development of diesel engines is represented by the achievement of an increasingly strict control on the systems used for the pollutant emission reduction. In particular, as far as NOx gas is concerned, EGR systems are mature and widely used, but increased efficiency in terms of emissions abatement, is necessary in order to determine as best possible the actual oxygen content in the charge at the engine intake manifold. The present work compares the ability of the ANN and Neuro-Fuzzy approach (ANFIS) to predict the volumetric oxygen concentration at the intake, using experimental data acquired on a compression ignition engine in transient operational conditions. In an off-line evaluation of results, both models show good predicting abilities; in particular the ANFIS model presents an absolute error value for the training and test phases respectively equal to 0.7 and 0.9 (as a percentage of 3.5% and 4.5%), while, the same evaluation obtained using the ANN-BP model provides 0.92 and 0.9 (as a percentage of 4.6% and 4.5%). The comparison shows that the ANFIS model produces more accurate solutions in less time, using linear rules that bind the input variables with the output. The linearity of the rules is a key feature to decrease the convergence time especially when the model is used for the on-board periodic training activity due to the aging of the engine.

A scalable, single step, synthetic approach for the manufacture of biocompatible, functionalized microgels and nanogels has been developed. Pulsed EB irradiation of PVP aqueous solutions, at relatively low energies per pulse and doses within the sterilization dose range, has led to a variety of ‘as-born’ sterile, functional nanostructures that exhibit a combination of favourable properties which make them suitable as biomedical nanocarriers. Reactive functional groups have been generated by graft copolymerization of functional acrylic monomers. These groups can be used to attach fluorescent probes to the NPs, to bioconjugate ligands of specific cell receptors and to incorporate therapeutics. To support the applicability of these nanogels, as well as their preparation procedure, for biomedical use, several different biocompatibility tests have been carried out.

This work presents a study on a gas-solid cyclone separator used in a complex cement production plant. The objective of the study consists on the performance evaluation and optimization of the cyclone separator in terms of particle separation and heat transfer efficiencies, while keeping pressure losses under control. The thermal interaction is between two gas-solid mixtures, one feeded at 850 °C and the other at 600 °C, respectively. The solid phase consists, mostly, of calcium carbonate subsequently intended to the so-called baking process for the production of clinker and then cement. The main goal of the study is maximizing the separation efficiency, minimizing the temperature at the exit of the plant and maintain the pressure drop not far from its value in the running plant. In a previous study, the authors defined the suitable setup of the mesh, physical models and turbulence; the same setup has been adopted in the present work during all the optimization phase. Vortex finder length (initially of cylindrical shape), its conicity angle and the pressure losses are the parameters (independent variables), taken into account to optimize the separation efficiency and the temperature of the gas at the exit of the plant. The optimization process was started with the base case that replies the geometric shape of the plant in operation. A detailed overview of the classical and recent optimization methods, is included in the Appendix, together with a brief illustration of a general pattern concerning an optimal design procedure. The numerical approach, for all the cases, is based on implicit unsteady simulations using the Eulerian Multiphase model.

The aim of the paper is the comparison of the injection process with two fuels, a standard diesel fuel and a pure biodiesel, methyl ester of soybean oil. Multiphase cavitating flows inside injector nozzles are calculated by means of unsteady CFD simulations on moving grids from needle opening to closure, using an Eulerian–Eulerian two-fluid approach which takes into account bubble dynamics. Afterward, spray evolutions are also evaluated in a Lagrangian framework using results of the first computing step, mapped onto the hole exit area, for the initialization of the primary breakup model. Two nozzles with cylindrical and conical holes are studied and their behaviors are discussed in relation to fuel properties. Nozzle flow simulations highlighted that the extent of cavitation regions is not much affected by the fuel type, whereas it is strongly dependent on the nozzle shape. Biodiesel provides a slightly higher mass flow in highly cavitating nozzles. On the contrary using hole shaped nozzles (to reduce cavitation) diesel provides similar or slightly higher mass flow. Comparing the two fuels, the effects of different viscosities and densities play main role which explains these behaviors. Simulations of the spray evolution are also discussed highlighting the differences between the use of fossil and biodiesel fuels in terms of spray penetration, atomization and cone-angle. Usage of diesel fuel in the conical convergent nozzle gives higher liquid penetration.

The paper reports on the optical investigation of a multiple spark ignition system carried out in a closed vessel in inert gas, and in an optical access engine in firing condition. The ignition system features a plug-top ignition coil with integrated electronics which is capable of multi-spark discharges (MSD) with short dwell time. First, the ignition system has been characterized in constant ambient conditions, at different pressure levels. The profile of the energy released by the spark and the cumulated value has been determined by measuring the fundamental electrical parameters. A high speed camera has been used to visualize the time evolution of the electric arc discharge to highlight its shape and position variability. The multiple spark system has then been mounted on an optical access engine with port fuel injection (PFI) to study the combustion characteristics in lean conditions with single and multiple discharges. The natural luminosity of the deflagration front was observed by means of the high speed camera, while correspondingly quantitative combustion analyses were performed based on the indicated pressure signal. The impact of the ignition system on the combustion stability is studied focusing on stable, near-limit and unstable operating conditions, as the relative air fuel ratio is increased. The results indicate that a extension of about 0.10 can be achieved using the MSD ignition. The benefit is associated with the presence of a non-homogeneous mixture preparation produced by the gasoline PFI fueling strategy. The high speed flame imaging allows to quantify cycle resolved equivalent flame radii as a function of time. The lower cycle-to-cycle variability attained with the MSD on the engine correlates to the higher ignition probability. A lower standard deviation of flame radius growth in the early stage of combustion is detected.

Engines are machines designed to provide mechanical energy to a wide variety of systems by converting the chemical energy of a fuel (devices that are capable of producing a mechanical output starting from different types of energy, such as electric or hydraulic energy, are usually called motors). Internal combustion engines (ICEs) exploit the conversion of the chemical energy contained in suitable fuels—typically hydrocarbons (HCs)—into mechanical energy, owing to a combustion process. The heat generated by oxidation reactions of elements such as carbon or hydrogen produces a temperature increase in the fluid that acts as the working fluid in the power plant. The enthalpy increase is then exploited to generate mechanical work in suitable machines, thanks to the fluid expansion. If the combustion takes place within the working fluid itself, the machine is then called ICE; on the contrary, if the working fluid receives the heat from the combustion products remaining separated from them by a solid surface (for instance, in a heat exchanger), the machine is referred to as external combustion engine. Typical examples of external combustion engines are steam turbine plants or Stirling engines, whereas the ICEs category includes gas turbines and reciprocating and rotary ICEs. External combustion engines operate according to a thermodynamic closed cycle, as the working fluid undergoes thermodynamic transformations in a closed loop without any Handbook of Clean Energy Systems, Edited by Jinyue Yan. C2015 John Wiley & Sons, Ltd. ISBN: 978-1-118-38858-7. need of being replaced. On the contrary, the fluid operating in an ICE undergoes chemical transformations that require its periodical replacement with fresh fluid, thus performing a thermodynamic open cycle. Even though gas turbine plants can also be designed to operate through a closed cycle, they are typically operating in open cycle: consequently, strictly speaking, they should be included in the ICEs category. Nevertheless, only reciprocating and rotary engines are commonly designated as ICEs and will therefore be discussed in this chapter

The paper reports on the experimental analysis of a multiple spark ignition system, carried out with conventional and optical non intrusive methods. The system features a plug-top ignition coil with integrated electronics which delivers high ignition energy and high voltage compared to conventional ignition coils, and is capable of multiple discharges with reduced dwell time. The ignition system is characterized in terms of electrical parameters to evaluate the spark power and energy as a function of different hardware configurations and operating conditions. A high speed camera is used to visualize, at different ambient pressures, the time evolution of the electric arc discharge in order to highlight its position variability, which could have an impact on combustion kernel development and deflagration front stability in engines.

The emissions limits of CO2 for vehicles are becoming more stringent with the aim of reducing greenhouse gas emissions and improve fuel economy. The New European Driving Cycle (NEDC) is adopted to measure emissions for all new internal combustion engines in the European Union, and it is performed on cold vehicle, starting at a temperature of 22°C ± 2°C. Consequently, the cold-start efficiency of internal combustion engine is becoming of predominant interest. Since at cold start the lubricant oil viscosity is higher than at the target operating temperature, the consequently higher energy losses due to increased frictions can substantially affect the emission cycle results in terms of fuel consumption and CO2 emissions. A suitable thermal management system, such as an exhaust-to-oil heat exchanger, could help to raise the oil temperature more quickly. To evaluate CO2 emissions and the benefits deriving from thermal management devices, an integrated model of the engine under consideration has been developed in GT-SUITE. The model is characterized by the integration of engine performance, vehicle, cooling system, lubricant system and friction sub-models. In particular, a friction sub-model has been developed in this work, by extending the Chen-Flynn engine friction model to take into account the actual oil temperature. The calibration of the thermal and friction sub-models has been done by defining a methodology based on few simple engine tests on a dynamometric bench. The tool, once calibrated and verified, can be used to predict the efficiency of different thermal management devices and strategies during engine warm-up and in different driving cycles.

In this work, first results are presented of the analysis of the behaviour, in actual, non-new operational conditions, of a lean burning, natural gas (NG) fueled, 1 MWe Caterpillar (CAT)-3516 engine, installed at the Engineering Faculty of Perugia University for the cogeneration of electrical and thermal energy. Data collected daily by the plant manager operators along 24 months of engine operation, which refer to power, electrical efficiency, NG flowrate, availability, and charge temperature, were analysed in connection with the recorded events of breakdown/defects and of maintenance/repair. An acquisition system for the continuous monitoring of several engine and plant quantities is described in detail.

The optimization of the air-fuel mixture formation plays a very important role in order to reduce the total amount of emissions from an SI engine. To comply with the EURO5 emission restrictions is necessary to understand the influence of injection timing (with respect to engine load) and injector geometry on the air-fuel dynamic interaction. The aim of this paper is to define a CFD methodology for the simulation of a PFI engine. The goals of this analysis are the evaluation of the injector geometry and injection timing influences on the air-fuel mixture preparation and so on the equivalence ratio distribution inside the combustion chamber. Preliminary assessments of the wall-film and droplet-wall interaction sub models have been carried out in order to validate the methodology [1]. In particular a three-step work procedure has been adopted; the first two steps are necessary to properly initialize the secondary breakup model while the third step regards the CFD RANS simulation of the PFI engine considered for this analysis. In particular, a motor-scooter SI engine at a low load operating condition has been considered in the present work. This operating condition has been chosen because of the urban stop-and-go use of a motor-scooter implies that frequently the engine is running at a low load operating condition.

The ever more strict pollutant emissions regulations urge to make further steps in the evolution of the internal combustion engines, in particular as far as the emissions generation. A direct observation of the phaenomena taking place inside the cylinder can hence help in better understanding the effects obtainable by using different solutions (injection systems, ignition systems,…). To this end, the use of an optical access engine can be very helpful. This paper presents the first step made at the Department of Industrial Engineering of the University of Perugia for the set-up of an experimental line to be used for the analysis of combustion events observed in a single cylinder optical access engine. The combustion was characterized by using different techniques: thermodynamic (heat release) based on in-cylinder pressure measurements, and non intrusive optical observations by means of images acquisition. The flame images collected by a synchronized CCD camera were post-processed in order to evaluate the rates of the in-cylinder flame front evolution, observing the combustion process from the flame kernel formation on. Different fuels were used in the spark ignition, four valves, optical access engine: pure gasoline, pure ethanol, a 50% gasoline/ethanol blend. The experimental tests were carried out at 900 rpm engine speed, in rich and lean conditions, the latter being of interest for the achievement of significant CO2 reduction.