Development of an engine variable geometry intake system for a Formula SAE application

The Formula SAE is an international competition for vehicle fully designed and built by students from worldwide Universities. The engine and vehicle design in the Formula SAE competition has to comply with a strict regulation. Regarding the engine intake line an air restrictor of circular cross-section no greater than 20 mm must be fitted between the throttle valve and the engine inlet. The aim of the throat is to limit the engine air flow rate as it strongly influences the volumetric efficiency and then the maximum power. The present paper is focused on the design of the engine intake system of the Firenze Race Team vehicle in order to optimize its performance in terms of both the maximum power and the drivability of the vehicle. One of the typical solutions for limiting the air restrictor influence consists of a plenum chamber placed along the intake line downstream of the restrictor. However the plenum involves also a delay in the engine response during the transient phases. The greater is the plenum, the lower are the power losses but the greater is the engine response delay. Taking advantage of a calibrated 1D model of the engine and a simplified vehicle model, the authors numerically analyzed an innovative solution that is constituted by a variable length duct inside the plenum. When the duct is at the maximum extension, the plenum is excluded from the intake line improving the engine response time. The optimization of the plenum volume and the definition of a preliminary control logic of the innovative system were done in order to obtain the maximum advantages in terms of both performance and engine drivability

Optimization of the Performance of a Formula SAE Engine by Means of a Wastegate Valve Electronically Actuated

Abstract The engine and vehicle design in Formula SAE competition has to accomplish a strict regulation. In order to limit the maximum power, an air restrictor of 20mm of diameter is imposed in the intake line. To overcome the limitations caused by the restrictor, Firenze Race Team equipped its one-cylinder engine with a turbocharger, which is conventionally provided with a wastegate (WG) valve to limit the maximum boost pressure and avoid knocking phenomena. Typically, the WG valve is controlled by a pneumatic actuator, which opens the valve according to a defined and constant maximum boost pressure downstream the compressor in the whole engine operating range. Therefore, the boost pressure at high engine speed, in which knocking problems are less intense and the volumetric efficiency is lower, is limited by the threshold value defined at medium-low engine speeds, i.e. the pneumatic WG limits the maximum power that the engine can supply. In this study, the implementation of an electronic control system for the WG valve is described together with a dedicated control strategy aimed at providing the desired boost pressure at full load for each engine speed, in order to get the maximum power avoiding knocking phenomena. The electronic WG provided higher power values and a more extended torque curve in comparison to the conventional pneumatic one

Experimental assessment of a methodology for the indirect in-cylinder pressure evaluation in four-stroke internal combustion engines

Recent innovations in engine control and diagnostics are providing room for development of innovative combustion approaches (e.g., low-temperature combustion) able to minimize the creation of pollutants. To ensure the constant fulfillment of the prescribed thermodynamic conditions, however, a fast real-time monitoring of the in-cylinder pressure is needed. To this end, dynamic pressure sensors, flush-mounted on the cylinder head, are commonly used. With this approach, the measurement accuracy is high, but the durability is limited by the harsh working conditions. The installation on the cylinder head is also complex. The development of robust and effective indirect measurement systems could then represent the enabler of a further development of this technology. In the present study, an innovative methodology to measure the in-cylinder pressure has been conceived and extensively tested on a four-stroke single-cylinder engine. The proposed approach is based on the analysis of the mechanical stress on the engine studs by means of a piezoelectric strain washer. This solution allows the user for a rapid and cost-effective sensor installation, described in the paper along with the signal post-processing techniques. Results showed good accuracy and robustness of the methodology, making the results of practical use for engine control

fine tuning of a two stoke engine in full power configuration provided with a low pressure direct injection system

Abstract The main drawbacks of two stroke (2S) engines consist in poor engine efficiency and high level of pollutant emissions. The contemporary opening of transfer and exhaust ports during the scavenging process causes the short circuit of fresh air-fuel mixture in case of indirect injection or carbureted engines. Despite the intrinsic strengths such as high power density, simplicity, compactness, lightweight and low production costs, 2S engines have been substituted by four stroke (4S) engines in many applications. Direct injection represents an effective solution to reduce the short circuit of fuel in 2S engines. Usually it is carried out by adopting high-pressure systems but the related increase of complexity and costs is inevitable. In order to maintain the intrinsic simplicity of a 2S engine, the most suitable solution is represented by a Low Pressure Direct Injection (LPDI) system. 2S LPDI engines are characterized by the presence of one or two injectors, working at 5 bar, installed on the cylinder wall. Previous works of the authors have shown the effectiveness of an LPDI system applied to a 300cc single cylinder engine in underpowered version with different ports timing and exhaust system with respect to the full power configuration. In the present paper, the authors show the fine-tuning of a 2S engine in full power configuration provided with two injectors installed on the cylinder and directed towards the exhaust port; the injector nozzles were located above the scavenge ports in order to guarantee the maximum interaction between injected fuel and inlet air flow. The engine has been deeply tested and analyzed at the test bench. Particular attention was paid to definition of the optimal injection timing in order to guarantee the best compromise between performance, efficiency and emissions. The experimental setup and the calibration methodology are discussed in detail. The results show the advantages of the LPDI system in terms of increased engine efficiency and emissions reduction with respect to the original carbureted engine maintaining the same level of performance

an indirect in cylinder pressure measurement technique based on the estimation of the mechanical strength acting on an engine head screw development and assessment

Abstract The increasing application of new concepts for the combustion process in internal combustion engines, e.g. HCCI or RCCI, is mainly aimed at reducing pollutant emissions and fuel consumption. A typical drawback of these technologies is the difficulty of properly controlling the combustion process in the area of medium-high brake mean effective pressure (BMEP), where the thermodynamic conditions inside the cylinder promote a very fast combustion process. To this end, the availability of a fast real-time monitoring of the in-cylinder pressure is then becoming pivotal. This is commonly done by means of piezoelectric dynamic pressure sensors, which are indeed very accurate, but also extremely expensive and characterized by a limited durability due to the harsh working conditions. Moving from this background, the present study describes a new methodology to evaluate the in-cylinder pressure by correlating it with the mechanical stress measured by a strain washer installed on an engine head screw. The strain washer can indeed work in a much more favorable environment with respect to a dynamic pressure sensor flush-mounted on the cylinder head (with aggressive hot gasses and high pressure) with direct benefits for its durability and ease of installation. To assess the model capabilities, experimental tests have been carried out on a single-cylinder, 4-stroke engine and on a 2-stroke engine at the laboratory of internal combustion engines of the Universita degli Studi di Firenze. The results reported in the study show the direct comparison of the in-cylinder pressure, as a function of the crankshaft angular position, measured directly with a dynamic pressure sensor and indirectly by means of the strain washer. Sound agreement was found between the two, proving the effectiveness of the proposed methodology

Performance and results of the high-resolution biogeochemical model PELAGOS025 v1.0 within NEMO v3.4

Abstract. The present work aims at evaluating the scalability performance of a high-resolution global ocean biogeochemistry model (PELAGOS025) on massive parallel architectures and the benefits in terms of the time-to-solution reduction. PELAGOS025 is an on-line coupling between the Nucleus for the European Modelling of the Ocean (NEMO) physical ocean model and the Biogeochemical Flux Model (BFM) biogeochemical model. Both the models use a parallel domain decomposition along the horizontal dimension. The parallelisation is based on the message passing paradigm. The performance analysis has been done on two parallel architectures, an IBM BlueGene/Q at ALCF (Argonne Leadership Computing Facilities) and an IBM iDataPlex with Sandy Bridge processors at the CMCC (Euro Mediterranean Center on Climate Change). The outcome of the analysis demonstrated that the lack of scalability is due to several factors such as the I/O operations, the memory contention, the load unbalancing due to the memory structure of the BFM component and, for the BlueGene/Q, the absence of a hybrid parallelisation approach

Growing old with antiretroviral therapy or elderly people in antiretroviral therapy: two different profiles of comorbidity?

Background In persons living with HIV (PLWH), the burden of non-communicable chronic diseases increased over time, because of aging associated with chronic inflammation, systemic immune activation, and long-term exposure to the combination antiretroviral therapy (ART). Methods To explore the association of chronological age, age at first ART, and exposure to ART with non-communicable chronic diseases, we performed a cross-sectional analysis to evaluate the prevalence of comorbidities in patients enrolled in the SCOLTA Project, stratified by groups of chronological age (50-59 and 60-69 years) and by years of antiretroviral treatment (ART, <= 3 or > 3 years). Results In 1394 subjects (23.8% women), mean age at enrollment was 57.4 (SD 6.5) years, and at first ART 45.3 (SD 10.7). Men were older than women both at enrollment (57.6 vs 56.8, p = 0.06) and at first ART (45.8 vs 43.6, p = 0.0009). ART duration was longer in women (13.1 vs 11.7 years, p = 0.01). The age- and sex-adjusted rate ratios (aRRs, and 95% confidence interval, CI) showed that longer ART exposure was associated with dyslipidemia (aRR 1.35, 95% CI 1.20-1.52), hypertension (aRR 1.52, 95% CI 1.22-1.89), liver disease (aRR 1.78, 95% CI 1.32-2.41), osteopenia/osteoporosis (aRR 2.88, 95% CI 1.65-5.03) and multimorbidity (aRR 1.36, 95% CI 1.21-1.54). These findings were confirmed in strata of age, adjusting for sex. Conclusions Our data suggest that longer ART exposure was associated with increased risk of dyslipidemia, hypertension, and osteopenia/osteoporosis, hence the presence of multimorbidity, possibly due to the exposition to more toxic antiretrovirals. We observed different comorbidities, according to ART exposure and age

Clusterization of co-morbidities and multi-morbidities among persons living with HIV: a cross-sectional study

Background: Among people living with HIV (PLWH), the prevalence of non-HIV related co-morbidities is increasing. Aim of the present study is to describe co-morbidity and multi-morbidity, their clustering mode and the potential disease-disease interactions in a cohort of Italian HIV patients. Methods: Cross-sectional analysis conducted by the Coordinamento Italiano per lo Studio di Allergia e Infezioni da HIV (CISAI) on adult subjects attending HIV-outpatient facilities. Non-HIV co-morbidities included: cardiovascular disease, diabetes mellitus, hypertension, oncologic diseases, osteoporosis, probable case of chronic obstructive pulmonary disease (COPD), hepatitis C virus (HCV) infection, psychiatric illness, kidney disease. Multi-morbidity was defined as the presence of two or more co-morbidities. Results: One thousand and eighty-seven patients were enrolled in the study (mean age 47.9 \ub1 10.8). One hundred-ninety patients (17.5%) had no co-morbidity, whereas 285 (26.2%) had one condition and 612 (56.3%) were multi-morbid. The most recurrent associations were: 1) dyslipidemia + hypertension (237, 21.8%); 2) dyslipidemia + COPD (188, 17.3%); 3) COPD + HCV-Ab+ (141, 12.9%). Multi-morbidity was associated with older age, higher body mass index, current and former smoking, CDC stage C and longer ART duration. Conclusions: More than 50% of PLHW were multi-morbid and about 30% had three or more concurrent comorbidities. The identification of common patterns of comorbidities address the combined risks of multiple drug and disease-disease interactions

Prevalence of HDV infection in people living with HIV: Data from a multicenter Italian cohort

ObjectivesThe development of novel antiviral agents active against Hepatitis Delta Virus (HDV) might change the natural history of chronic infection, reducing the risk for end-stage liver disease. People living with HIV (PWH) are at risk for bloodborne pathogens infection, but limited data on epidemiology of HDV infection is available in this setting. The aim of this study was to investigate HDV prevalence and attitude toward HDV testing and treatment in infectious diseases centers.MethodsA cross sectional survey was performed among centers participating in the CISAI (Coordinamento Italiano per lo Studio dell’Allergia in Infezione da HIV) Group. The survey addressed anti-HDV prevalence and HDV-RNA detectability rates in PWH as well as perceived obstacles to treatment.ResultsOverall, responses from ten sites were collected. Among participating centers, 316 PWH with HBV chronic infection are currently followed. Of them, 15.2% had positive anti-HDV antibodies, while 13.9% were not tested yet. Overall, 17% of anti-HDV positive PWH tested at least once for HDV-RNA had active HDV infection, and 71% of them had advanced liver disease. Most infectious diseases centers intend to treat locally HDV infection with upcoming anti-HDV drugs, but some concerns exist regarding treatment schedule.DiscussionHDV testing needs to be implemented in PWH. At present, few patients followed in the CISAI centers seem to be candidate to receive new direct active anti-HDV agents, but repeated HDV-RNA measures could change this proportion