Effect of Cyclohexane on the Combustion Characteristics of Multi-Component Gasoline Surrogate Fuels.

It has been discovered that there is a dynamic coupling between cycloalkanes and aromatics, which affects the number and types of radicals, thereby controlling the ignition and combustion of fuels. Therefore, it is necessary to analyze the effects of cyclohexane production in multicomponent gasoline surrogate fuels containing cyclohexane. In this study, a five-component gasoline surrogate fuel kinetic model containing cyclohexane was first verified. Then, the effect of cyclohexane addition on the ignition and combustion performance of the surrogate fuel was analyzed. This study shows that the five-component model exhibits good predictive performance for some real gasoline. Meanwhile, the addition of cyclohexane decreases the ignition-delay time of the fuel in the low and high temperature bands, which is caused by the early oxidation and decomposition of cyclohexane molecules, generating more OH radicals; in the medium temperature band, the isomerization and decomposition reactions of cyclohexane oxide cC6H12O2 dominate the temperature sensitivity of the ignition delay, affecting the small molecule reactions that promote the generation of reactive radicals such as OH, thus inhibiting the negative temperature coefficient behavior of the surrogate fuel. The laminar flame speed of the surrogate fuels increased with the increase in the proportion of cyclohexane. This is due to the fact that the laminar flame speed of cyclohexane is higher than that of chain and aromatic hydrocarbons, and the addition of cyclohexane dilutes the ratio of chain and aromatic hydrocarbons in the mixture. In addition, engine simulation studies have shown that at higher engine speeds, the five-component surrogate fuel containing cyclohexane requires lower intake-gas temperatures to achieve positive ignition and are closer to the in-cylinder ignition of real gasoline.

Construction of a Chemical Kinetic Model of Five-Component Gasoline Surrogates under Lean Conditions.

The requirements for improving the efficiency of internal combustion engines and reducing emissions have promoted the development of new combustion technologies under extreme operating conditions (e.g., lean combustion), and the ignition and combustion characteristics of fuels are increasingly becoming important. A chemical kinetic reduced mechanism consisting of 115 species and 414 elementary reactions is developed for the prediction of ignition and combustion behaviors of gasoline surrogate fuels composed of five components, namely, isooctane, n-heptane, toluene, diisobutylene, and cyclohexane (CHX). The CHX sub-mechanism is obtained by simplifying the JetSurF2.0 mechanism using direct relationship graph error propagating, rate of production analysis, and temperature sensitivity analysis and CHX is mainly consumed through ring-opening reactions, continuous dehydrogenation, and oxygenation reactions. In addition, kinetic parameter corrections were made for key reactions R14 and R391 based on the accuracy of the ignition delay time and laminar flame velocity predictions. Under a wide range of conditions, the mechanism's ignition delay time, laminar flame speed, and the experimental and calculated results of multi-component gasoline surrogate fuel and real gasoline are compared. The proposed mechanism can accurately reproduce the combustion and oxidation of each component of the gasoline-surrogate fuel mixture and real gasoline.

Chemical Kinetic Model of Multicomponent Gasoline Surrogate Fuel with Nitric Oxide in HCCI Combustion.

This study presents a simplified mechanism of a five-component gasoline surrogate fuel (TDRF-NO) that includes n-heptane, isooctane, toluene, diisobutylene (DIB) and nitric oxide (NO). The mechanism consists of 119 species and 266 reactions and involves TDRF and NO submechanisms. Satisfactory results were obtained in simulating HCCI combustion in engines. The TDRF submechanism is based on the simplified mechanism of toluene reference fuel (TRF) and adds DIB to form quaternary surrogate fuel for gasoline. A simplified NO submechanism containing 33 reactions was added to the simplified mechanism of TDRF, considering the effect of active molecular NO on the combustion of gasoline fuel. The ignition delay data of the shock tube under different pressure and temperature conditions verified the validity of the model. Model verification results showed that the ignition delay time predicted by the simplified mechanism and its submechanics were consistent with the experimental data. The addition of NO caused the ignition delay time of the mechanism simulation to advance with increasing concentration of NO added. The established simplified mechanism effectively predicted the actual combustion and ignition of gasoline.

TREATMENT OF COMATOSE SURVIVORS OF IN-HOSPITAL CARDIAC ARREST WITH EXTENDED ENDOVASCULAR COOLING METHOD FOR 72 H: A PROPENSITY SCORE-MATCHED ANALYSIS.

ABSTRACT: Aims: Targeted temperature management is recommended for at least 24 h in comatose survivors of in-hospital cardiac arrest (IHCA) after the return of spontaneous circulation; however, whether an extension for 72 h leads to better neurological outcomes is uncertain. Methods: We included data from the Qilu Hospital of Shandong University between July 20, 2019, and June 30, 2022. Unconscious patients who had return of spontaneous circulation lasting >20 consecutive min and received endovascular cooling (72 h) or normothermia treatment were compared in terms of survival-to-discharge and favorable neurological survival. Propensity score matching was used to formulate balanced 1:3 matched patients. Results: In total, 2,084 patients were included. Sixteen patients received extended endovascular cooling and 48 matched controls received normothermia therapy. Compared with the normothermia group, patients who received prolonged endovascular cooling had a higher survival-to-discharge rate. However, good neurological outcomes did not differ significantly. Before matching, Cox regression analysis, using mortality as the event, showed that extended endovascular cooling independently affected the survival of IHCA patients. Conclusions: Among comatose patients who had been resuscitated from IHCA, the use of endovascular cooling for 72 h might confer a benefit on survival-to-discharge.

Effects of Syngas Addition on Combustion Characteristics of Gasoline Surrogate Fuel.

Syngas has the potential to become an alternative fuel for internal combustion engines. In this work, a detailed mechanism containing 1389 species and 5942 reactions was developed to examine the combustion of syngas/gasoline blends. The influence of syngas addition on the ignition delay time (IDT) and laminar flame speed of gasoline fuel was studied. Two influencing factors were considered: the mixing ratio of syngas and the H2/CO ratio in syngas. The changes in heat release, free radical concentrations, and emissions were also studied. Syngas can boost the system's reaction activity and promote ignition in the high-temperature area over 1000 K. However, the diluting effect is visible at low temperatures below 1000 K, leading to an IDT lag. The effect of the H2/CO ratio on the IDT was not as pronounced as expected. The addition of syngas can inhibit the knock combustion of the engine to a certain extent, but it will also lead to a violent exothermic process and a decrease in the total release of heat. Syngas addition increases the concentration of small molecule radicals and promotes the laminar flame speed. At higher temperatures and pressure levels, the trend of syngas/gasoline laminar flame speed is more dependent on changes in OH radical concentrations. The addition of syngas favors the promotion of complete combustion and the reduction of HC emissions but also results in an additional increase in CO. Combustion at lower temperatures has lower CO and HC emissions.

Incidence, process of care, and outcomes of out-of-hospital cardiac arrest in China: a prospective study of the BASIC-OHCA registry.

BACKGROUND: Out-of-hospital cardiac arrest (OHCA) is an important global public health issue, but its epidemiology and outcomes in low-income and middle-income countries remain largely unknown. We aim to comprehensively describe the incidence, process of care, and outcomes of OHCA in China. METHODS: In the prospective, multicentre, population-based Baseline Investigation of Out-of-hospital Cardiac Arrest (BASIC-OHCA) registry study, participating sites were selected from both urban and rural areas in all seven geographical regions across China. All patients with OHCA assessed by emergency medical service (EMS) staff were consecutively enrolled from Aug 1, 2019, to Dec 31, 2020. Patients with suspected cardiac arrest assessed by bystanders whose return of spontaneous circulation was achieved without the need for defibrillation or EMS personnel cardiopulmonary resuscitation were excluded. Patients with all key variables missing were excluded, including resuscitation attempt, age, sex, witnessed status, cause, all process of care indicators, and all outcome measures. In this analysis, we included data for EMS agencies serving 25 monitoring sites (20 urban and five rural) that included the entire serving population, data for the whole of 2020, and at least 50 OHCA patients in 2020. Data were collected and reported using the Utstein template. We calculated the crude incidence of EMS-assessed OHCA in 2020. We also report data on baseline characteristics (including sex, cause, location of OHCA, and presence of shockable rhythm), process of care (including EMS response time, cardiopulmonary resuscitation, defibrillation, and advanced life support), and outcomes of non-traumatic OHCA between Aug 1, 2019, and Dec 31, 2020, including survival and survival with favourable neurological outcomes at discharge or 30 days, and at 6 and 12 months. FINDINGS: Of 115·1 million people served by the 25 participating sites, 132 262 EMS-assessed patients with OHCA were enrolled, and resuscitation was attempted for 42 054 (31·8%) patients between Aug 1, 2019, and Dec 31, 2020. The crude incidence of EMS-assessed OHCA was 95·7 per 100 000 population (95% CI 95·6-95·8) in 2020. Among 38 227 individuals with non-traumatic OHCA, 25 958 (67·9%) were male, 30 282 (79·2%) had a cardiac arrest at home, 32 523 (85·1%) had a presumed cardiac cause, and 2297 (6·0%) presented with an initial shockable rhythm. 4049 (11·5%) of 35 090 patients with an unwitnessed or bystander-witnessed OHCA received dispatcher-assisted cardiopulmonary resuscitation and 7121 (20·3%) received bystander cardiopulmonary resuscitation; only 14 (<0·1%) patients were assessed by bystanders with an automated external defibrillator. The median EMS response time was 12 min (IQR 9-16). At hospital discharge or 30 days, 441 (1·2%) of 38 227 survived, 304 (0·8%) survived up to 6 months, and 269 (0·7%) up to 12 months. At hospital discharge or 30 days, 309 (0·8%) survived with favourable neurological outcomes, 257 (0·7%) had favourable neurological outcomes at 6 months, and 236 (0·6%) at 12 months. INTERPRETATION: Our findings revealed a high burden of EMS-assessed OHCA with a low proportion of resuscitation attempts. The suboptimal implementation of chain of survival and unsatisfactory prognosis call for national efforts to improve the care and outcomes of patients with OHCA in China. FUNDING: The National Science & Technology Fundamental Resources Investigation Program of China, the State Key Program of the National Natural Science Foundation of China, Taishan Pandeng Scholar Program of Shandong Province, the Key Research & Development Program of Shandong Province, the Interdisciplinary Young Researcher Groups Program of Shandong University, the Clinical Research Center of Shandong University, the ECCM Program of Clinical Research Center of Shandong University, and the Natural Science Foundation of Shandong Province.

Combustion and Emission Characteristics of Gasoline Engine Blended Combustion Syngas.

It is an effective way to introduce syngas fuel into gasoline engine for blending combustion to improve combustion and reduce emissions. In this paper, the combustion and emission characteristics of the direct injection engine under the condition of mixed combustion of syngas were analyzed by a numerical simulation method. The engine ran at 2000 rpm, and the mass fraction of syngas was from 0 to 20%. The results showed that with the increase in the mass ratio of syngas in the dual fuel, the average pressure and temperature in the cylinder increased first and then decreased. The maximum in-cylinder pressure and in-cylinder temperature increased by 27.5 and 2.97%, respectively. The instantaneous heat release rate also showed a law of first increasing and then decreasing, in which the peak value of the instantaneous heat release rate increased by 32.1% at the highest. In addition, with the increase in the ratio of syngas, the emission of nitrogen oxides in the cylinder gradually decreased, with a maximum reduction of 27.4%. The unburned hydrocarbons first decreased and then increased, with a maximum reduction of 7.6%. Meanwhile, the emission of carbon dioxide was negatively correlated with the ratio of syngas in the dual fuel. With the increase in hydrogen ratio in syngas, the carbon monoxide was gradually reduced, with a maximum reduction of 65%. The carbon dioxide increased first and then decreased, with a maximum addition of 4.8%. The ratio of hydrogen and carbon monoxide in syngas had little effect on the emission of unburned hydrocarbons.

Research on the Effect of Water Injection Pressure on Knocking Combustion of a Direct Injection Gasoline Engine.

In this study, the research method of numerical simulation is used to explore the inhibition of different water injection pressures on knock combustion of turbocharged direct injection gasoline (GDI) engines by coupling computational fluid dynamics with a chemical-kinetics model. First, the ignition advance angle and compression ratio are increased to induce the GDI engine to knock, and then the influence of the water injection pressure on the in-cylinder, evaporation of water, and the knock of the gasoline engine are analyzed. The simulation results show that, compared with no water injection, the direct injection of water in the cylinder can significantly reduce the knock intensity. When the water injection pressure is greater than 40 bar, the knock intensity is less than 2 and the knocking is completely suppressed. In this work, the effects of different water injection pressures on knocking are explored by analyzing the effects of water injection pressure on water atomization, in-cylinder combustion, and the knocking mechanism. On the one hand, the evaporation rate of water increases with increasing water injection pressure and the quality of the liquid film generally improves. On the other hand, direct water injection can significantly reduce the distribution of CH2O in the end mixture, thereby reducing the generation of H2O2 and further suppressing the spontaneous combustion of the end mixture. At the moment of knock, when the water injection pressure is greater than 40 bar, the detonation mechanism of the no. 7 monitoring point does not produce a sudden change in HCO radicals. The water spray can effectively reduce the NO x emission, and the NO x emission under the water spray pressure of 120 bar is the lowest. However, after spraying water, it will increase CO emissions.

Effects of Piston Shape on the Performance of a Gasoline Direct Injection Engine.

In this study, two different piston structures (bowl-shaped pit and trapezoidal pit) are constructed; the mixture formation, combustion, and emissions of a gasoline direct injection engine with the two piston types are compared and analyzed by computational fluid dynamics simulation. The results show that piston A (bowl-shaped) can form a combustible mixture near the spark plug at the ignition time and has higher pressure peaks and accumulated heat release than piston B (trapezoidal), which helps improve the combustion efficiency of the internal combustion engine. Furthermore, three pistons with different bowl-shaped pit depths (pistons A1, A2, and A3) are designed based on piston A. The results show that piston A2 (7.7 mm) has advantages in terms of strengthening the turbulence in the cylinders, promoting fuel evaporation, increasing the in-cylinder turbulent kinetic energy and the velocity of the airflow near the spark plug at the ignition time, and accelerating the rapid diffusion of combustion and the rapid increase in in-cylinder temperature and pressure. Also, piston A2 can reduce the CO and soot emissions.

A Simulation Study of Water Injection Position and Pressure on the Knock, Combustion, and Emissions of a Direct Injection Gasoline Engine.

A turbocharged downsizing spark ignition (SI) engine combined with direct injection technology has the potential to improve the power and fuel economy and reduce emissions. However, gasoline engines are prone to knocking under low-speed and high-load conditions, which limits the application and development of downsizing SI engines. In this study, numerical simulation methods are used to explore the feasibility of water injection in the intake port to reduce the knock tendency of gasoline direct injection (GDI) engines and to explore the effects of different water injection pressures on combustion and emissions. First, the GDI engine is induced to knock by increasing the compression ratio and advancing the spark timing. Then, the influences of low position and no angle (LPNA) and high position and angled water injector arrangements on engine combustion are explored. When the water injector arrangement is LPNA, the turbulent kinetic energy near the spark plug is higher, the equivalence ratio is more evenly distributed, and the engine knock intensity is smaller. Finally, when the arrangement of the water injector is LPNA, the effects of water injection pressure on the knock, combustion, and emissions of the GDI engine are explored. The results show that when the water injection pressure is 5 bar, the knock intensity of the engine is the smallest, the cycle work is the highest, and the emissions of NO x and unburned hydrocarbon are the lowest.

Epidemic character and environmental factors in epidemic areas of severe fever with thrombocytopenia syndrome in Shandong Province.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging lethal tick-borne disease that has been widely prevalent in East Asia in recent years, and raised an important public health problem in China. However, a comprehensive and thorough understanding of the current SFTS epidemic areas in Shandong Province is not available. Accordingly, a descriptive analysis was applied to explore the demographic and spatio-temporal features of SFTS cases in Shandong Province from 2010 to 2015. The division between epidemic areas and non-epidemic areas was given by maximum entropy niche model (MaxEnt) based on environmental factors such as temperature and precipitation. There were 1,786 SFTS cases between 2010 and 2015 in Shandong, mainly involving middle-aged and elderly individuals (age:40-80) and farmers (84.6 %). May-October was the high-incidence period and the SFTS cases were mostly clustered in the central and eastern regions of Shandong Province. In light of MaxEnt, 3 specific environmental features between dichotomous areas were identified, including 1) most epidemic areas are covered by acidic soils (Constituent ratio: 63.8 %) while 29.1 % coverage appears in non-epidemic areas, 2) compared with non-epidemic areas, the identical kinds of agricultural areas accounted for a higher constituent ratio (64.9 % vs. 42.7 %), and 3) lower level of annual temperature in epidemic areas compared to non-epidemic areas [Median: 13.2℃ vs. 14.2℃; (25th IQR, 75th IQR): (12.5, 13.7) vs. (13.6, 14.9)]. Our study suggests middle-aged and elderly farmers are high-risk population to be focused on in future prevention and acidic soils, agricultural activities as well lower temperature that may be related to increased SFTS incidence.

The characteristics of current natural foci of hemorrhagic fever with renal syndrome in Shandong Province, China, 2012-2015.

BACKGROUND: Hemorrhagic fever with renal syndrome (HFRS), an infectious disease caused by hantaviruses, is endemic in China and remains a serious public health problem. Historically, Shandong Province has had the largest HFRS burden in China. However, we do not have a comprehensive and clear understanding of the current epidemic foci of HFRS in Shandong Province. METHODOLOGY/PRINCIPAL FINDINGS: The incidence and mortality rates were calculated, and a phylogenetic analysis was performed after laboratory testing of the virus in rodents. Spatial epidemiology analysis was applied to investigate the epidemic foci, including their sources. A total of 6,206 HFRS cases and 59 related deaths were reported in Shandong Province. The virus carriage rates of the rodents Rattus norvegicus, Apodemus agrarius and Mus musculus were 10.24%, 6.31% and 0.27%, respectively. The phylogenetic analysis indicated that two novel viruses obtained from R. norvegicus in Anqiu City and Qingzhou City were dissimilar to the other strains, but closely related to strains previously isolated in northeastern China. Three epidemic foci were defined, two of which were derived from the Jining and Linyi epidemic foci, respectively, while the other was the residue of the Jining epidemic focus. CONCLUSIONS/SIGNIFICANCE: The southeastern and central Shandong Province are current key HFRS epidemic foci dominated by A. agrarius and R. norvegicus, respectively. Our study could help local departments to strengthen prevention and control measures in key areas to reduce the hazards of HFRS.

The relationship between meteorological factors and mumps based on Boosted regression tree model.

BACKGROUND: Mumps remains a major global public health problem. Many studies have explored the relationship between meteorological factors and mumps, few have comprehensively explored such associations considering nonlinear relationship, delayed effects and collinearity in order to more accurately estimate them. This study aims to explore the relationship between meteorological factors and mumps in consideration of nonlinearity, delayed effects and collinearity. METHODS: We collected daily reported mumps cases and meteorological data for Jining City, Shandong Province, China from 1 January 2007 to 31 December 2016. By building a Boosted regression tree model (BRT) for each day from lag 0days to the maximum lag time, the optimal lag time was selected and the relationship between meteorological factors and mumps was explored for this lag time. RESULTS: From 2007 to 2016, a total of 15,064 cases of mumps were reported in Jining, with a sex ratio of 2.11:1. Cases were most prevalent in 5-9-year-olds (42.15%) followed by 10-14-year-olds (24.72%). The optimal lag time identified was 10days and the three meteorological factors that contributed the most to the risk of mumps were daily mean temperature, daily mean relative humidity and daily mean sunshine duration. Their relative contribution rates were 24.4%, 19.9% and 18.3%, respectively. The mean temperature and sunshine duration relationships approximated a U-shaped effect on the risk of mumps, with estimated thresholds of 5.5°C and 9.5h, respectively. The effect of relative humidity on mumps increased slightly and then decreased rapidly, with a threshold of 64%. CONCLUSIONS: Our study indicates that daily mean temperature, relative humidity and sunshine duration were three significant meteorological factors associated with the incidence of mumps in Jining, China. Understanding the shape of relationships and their thresholds are critical for establishing early warning systems which are important tools in the prevention and control of mumps.