Peak Pressure Rate Research Articles

Development of an Efficient Conjugate Heat Transfer Modeling Framework to Optimize Mixing-Limited Combustion of Ethanol in a Diesel Engine

Abstract Mixing controlled combustion of alcohol fuels has been identified as a promising technology based on their low propensity for particulate and NOx production, but the higher heats of vaporization and auto-ignition temperatures of these fuels make their direct use in diesel engine architectures a challenge. To realize the potential of alcohol-fueled combustion, a computational fluid dynamics (CFD) modeling framework is developed, validated, and exercised to identify designs that maximize engine thermal efficiency. To evaluate the use of thermal barrier coatings (TBCs), a simplified one-dimensional (1D) conjugate heat transfer (CHT) modeling framework is employed. The addition of the 1D CHT model only increases the computational expense by 15% relative to traditional approaches, yet offers more accurate heat transfer predictions over constant temperature boundary conditions. The validated model is then used to explore a range of injector orientations and piston bowl geometries. Using a design of experiments (DoE) approach, several designs were identified that improved fuel–air mixing, shortened the combustion duration, and increased thermal efficiency. The most promising design was fabricated and tested in a Caterpillar 1Y3700 single-cylinder oil test engine (SCOTE). Engine testing confirmed the findings from the CFD simulations and found that the co-optimized injector and piston bowl design yielded over 2-percentage point increase in thermal efficiency at the same equivalence ratio (0.96) and over 6-percentage point increase at the same engine load (10.1 bar indicated mean effective pressure (IMEP)), while satisfying design constraints for peak pressure and maximum pressure rise rate.

Potential of reactivity-controlled compression ignition with reverse reactivity stratification (R-RCCI) fueled with gasoline and polyoxymethylene dimethyl ethers (PODEn)

To improve the trade-off between thermal efficiency and peak heat release rate (HRR) of partially premixed combustion (PPC) and the combustion efficiency of reactivity-controlled compression ignition (RCCI), the combustion mode with premixed high-reactivity fuel and direct-injection (DI) low-reactivity fuel, called RCCI with reverse reactivity stratification (R-RCCI), was explored at low loads in a light-duty diesel engine in this study. Compared with diesel, polyoxymethylene dimethyl ethers (PODEn) has better volatility, which is beneficial for the formation of premixed charge, so it was used as the premixed high-reactivity fuel for R-RCCI in this work. The gasoline and P20G80 (PODEn/gasoline blends with the volume fraction of 20%/80%) were respectively applied as the DI low-reactivity fuel. By investigating the combustion characteristics of R-RCCI, it is found that R-RCCI can break the trade-off between combustion efficiency and nitrogen oxides (NOx) emissions. This is because the combustion efficiency of R-RCCI is dominated by the spray location of the DI fuel rather than the 50% burn point (CA50). As the start of injection (SOI) timing is retarded, the fuel injected within the piston bowl increases, and combustion efficiency, as well as indicated thermal efficiency (ITE), is considerably promoted. Meanwhile, CA50 progressively retards with delayed SOI timing, which effectively reduces NOx emissions. The soot emissions of R-RCCI are also extremely low. The maximum ITE of PODEn/P20G80 R-RCCI is significantly higher than that of PODEn/gasoline R-RCCI. This occurs because the higher reactivity of P20G80 can reduce the sensitivity of CA50 to SOI timing and improve combustion stability, so a more delayed SOI timing is allowed to improve ITE. With the same engine configurations, R-RCCI can reduce peak pressure rise rate and improve combustion stability, while enhancing combustion efficiency and ITE compared with RCCI at the low-load conditions tested in this study.

Impact of Active Control Turbocharging on the Fuel Economy and Emissions of a Light-Duty Reactivity Controlled Compression Ignition Engine: A Simulation Study

While forced induction strategies such as turbocharging can increase the power output and extend the load limit of engines operating on low temperature combustion strategies such as reactivity controlled compression ignition, the low exhaust enthalpy prevalent in these strategies requires the use of high backpressures to attain high turbocharger efficiencies, leading to high pumping losses and in turn poor fuel economy. Hence, there is a need to improve the exhaust energy utilization by the turbocharger such that the negative effects of the high backpressure requirements are offset. One turbocharger operating strategy that has the potential to enhance exhaust enthalpy conversion by the turbine is active control turbocharging (ACT), in which the rack position of a variable geometry turbocharger (VGT) is actuated using a continuously varying sinusoidal signal whose frequency is proportional to engine speed. In this study, the impact of ACT on turbocharger performance and fuel economy of a light-duty reactivity controlled compression ignition engine equipped with a VGT is investigated through coupled GT-POWER/KIVA-3V simulations at a medium-load cruise operating condition. A design of experiments study was executed in which the rack position amplitude and phase angle were independently varied, and the turbine efficiency, compressor efficiency, crankshaft torque, and brake specific fuel consumption were tracked for each run. The results show that ACT operation significantly increased the torque output while improving fuel economy over baseline VGT operation, but the range of actuation signal amplitude ratio was limited to 40% of the maximum amplitude possible due to peak cylinder pressure and peak pressure rise rate constraints. It is also shown that the impact of signal phase angle on turbocharger efficiency and overall system performance is not as significant as the amplitude ratio. The best fuel economy improvement over the baseline VGT operation at cruise conditions was observed at 40% amplitude ratio and 0° phase angle, and this value was 2.8%.

Safety and feasibility of dopamine-atropine stress echocardiography.

Dobutamine-atropine stress echocardiography (DSE) has lower sensitivity in patients with advanced liver disease (ALD) due to vasodilation. Dopamine-atropine stress echocardiography (DopSE) may be an alternative to DSE in ALD patients by improving the blood pressure response to stress. The safety and tolerability of DSE and DopSE were compared in 10 volunteers. The safety, adverse effects, and efficacy of DopSE were then assessed in 105 patients, 98 of whom had ALD. Dopamine was infused in stepwise fashion from 5µg/kg/min to a peak dose of 40µg/kg/min. Atropine was given before and in early stages of dopamine infusion up to cumulative dose of 1.5mg. The hemodynamic responses of 98 ALD patients were compared with 102 patients with ALD who underwent standard DSE. In normal volunteers, systolic BP increased more with DopSE compared to DSE (61±19mmHg vs 39±15mmHg, P=.008). In 105 patients who underwent DopSE, none had adverse effects that required early stress termination. In the groups with ALD, the systolic BP increase (38±28mmHg vs 12±27mmHg, P<.001) and peak rate pressure product (RPP) (22861±5289 vs 17211±3848, P=<.001) were both higher in those undergoing DopSE versus DSE. The sensitivity and specificity of DopSE were 45% and 88%, respectively for coronary disease (≥70% stenosis) in 37 patients who had angiography. Dopamine-atropine stress echocardiography appears to be a safe stress modality and provides greater increases in RPP in patients with ALD compared to DSE.

Experimental study on spray characteristics, combustion stability, and emission performance of a CRDI diesel engine operated with biodiesel–ethanol blends

Biodiesel is a promising alternative fuel for diesel engines, but its high viscosity and low volatility have limitations in decreasing emissions. As a renewable alternative fuel with a high oxygen content, ethanol blended with biodiesel can decrease kinematic viscosity and improve fuel evaporation. In this study, the effects of the ethanol addition ratio on the spray, combustion, and emission performances of a diesel engine fuelled with biodiesel were investigated. The spray characteristics were measured using a high-speed camera and Malvern laser analysis, whereas the combustion and emission performances were tested on a turbocharged common rail direct injection (CRDI) diesel engine. The results show that adding ethanol to biodiesel enlarges the spray cone angle (SCA) and shortens spray tip penetration (STP). In addition, the curves of the size–volume distribution (SVD) of the atomized fuel droplets move toward a smaller diameter, and the Sauter mean diameter (SMD) of the biodiesel–ethanol (BE) blends gradually decreases with increasing ethanol proportion. At low loads, the fuel injection strategy is multi-injection, and the peak cylinder pressures (PCPs) of BE blends are 0.77–1.96% higher than that of diesel at different ethanol blending ratios. However, the peak heat release rates (PHRRs) of BE blends are 9.3–11.5% higher than that of diesel owing to a faster combustion rate, longer main-injection duration, and more hydroxyl radicals generated in the pilot-injection stage. At medium–high loads, the injection strategy changes to single injection, the PCPs of BE blends are roughly equivalent to that of diesel, and the PHRRs of BE blends for different ethanol blending ratios are 9.76–11.91% lower than that of diesel. This is because of the lower diffusion combustion ratio, lower heat value, and change of injection duration corresponding to the variation in fuel properties. In addition, the results of the peak pressure rise rate and the cyclic variation indicate that the higher ethanol addition ratio increases the combustion noise and decreases the combustion stability. In terms of exhaust emissions, compared with biodiesel, with increasing ethanol blending ratio, the soot emissions for different BE blends decrease by 11.28–47.23%, the NOx emissions increase by 2.68–7.04%, and the HC emissions increase by 9.99–21.47%. Considering the engine performance comprehensively, a 20% ethanol blending ratio in biodiesel is recommended.

Combustion, performance, and emission characteristics of diesel engine with nanocera added water emulsified Mahua biodiesel blend

AbstractThe present study was conducted to investigate the combustion, performance, and emission characteristics of a 10 kW, single cylinder, direct injection diesel engine using cerium oxide nanoparticles (nanocera) added water emulsified Mahua biodiesel blend (NWEB) vis‐à‐vis water emulsified Mahua biodiesel blend (WEB), B20, and diesel. NWEB was prepared with 69.7 ppm of cerium oxide nanoparticles, 1% surfactants, 10% water, and 2,500 rpm of stirrer. After measuring the fuel properties of test fuels, these were used to run the diesel engine at different engine loads and combustion, performance, and emission parameters were measured. The peak pressure rise rate significantly reduced with NWEB replacing diesel. CA10 and C50 points were observed earlier for NWEB as compared to base fuels. The rapid combustion, controlled combustion, and total combustion duration reduced by more than 5.0, 4.0, and 4.6%, respectively, in engine operation with NWEB over diesel and B20. The maximum brake thermal efficiency of 30.41% was recorded for NWEB as compared to 28.25% for diesel. The mean brake‐specific fuel consumption was 3.76 and 3.93% lesser with NWEB as compared to B20 and WEB, respectively. The mean EGT, BSCO, BSHC, and BSNOxwere reduced by 5.4, 30.8, 43.7, and 26.9%, respectively, with NWEB over diesel.

Physical Therapist Management of COVID-19 in the Intensive Care Unit: The West China Hospital Experience.

ObjectiveCoronavirus disease 2019 (COVID-19) has dominated the attention of health care systems globally since January 2020. Various health disciplines including physical therapists are still exploring the best way to manage this new disease. The role and involvement of physical therapists in the management of COVID-19 are not yet well defined and are limited in many hospitals. This article reports a physical therapy service specially commissioned by the Health Commission of Sichuan Province to manage COVID-19 during patients’ stay in the intensive care unit (ICU) at the Public Health Clinical Center of Chengdu in China.MethodsPatients diagnosed with COVID-19 were classified into 4 categories under a directive from the National Health Commission of the People’s Republic of China. Patients in the “severe” and “critical” categories were admitted to the ICU irrespective whether mechanical ventilation was required. Between January 31, 2020, and March 8, 2020, a cohort of 16 patients was admitted to the ICU at the Public Health Clinical Center of Chengdu. The median (minimum to maximum) hospital and ICU stays for these patients were 27 (11–46) and 15 (6–38) days, respectively. Medical management included antiviral, immunoregulation and supportive treatment of associated comorbidities. Physical therapist interventions included body positioning, airway clearance techniques, oscillatory positive end-expiratory pressure, inspiratory muscle training, and mobility exercises. All patients had at least 1 comorbidity. Three of the 16 patients required mechanical ventilation and were excluded for outcome measures that required understanding of verbal instructions. In the remaining 13 patients, respiratory outcomes—including the Borg Dyspnea Scale, peak expiratory flow rate, Pao2/Fio2 ratio, maximal inspiratory pressure, strength outcomes, Medical Research Council Sum Score, and functional outcomes (including the Physical Function in Intensive Care Test score, De Morton Mobility Index, and Modified Barthel Index)—were measured on the first day the patient received the physical therapist intervention and at discharge.ResultsAt discharge from the ICU, while most outcome measures were near normal for the majority of the patients, 61% and 31% of these patients had peak expiratory flow rate and maximal inspiratory pressure below 80% of the predicted value and 46% had De Morton Mobility Index values below the normative value.ConclusionThe respiratory and physical functions of some patients remained poor at ICU discharge, suggesting that long-term rehabilitation may be required for these patients.ImpactOur experience in the management of patients with COVID-19 has revealed that physical therapist intervention is safe and appears to be associated with an improvement in respiratory and physical function in patients with COVID-19 in the ICU.

On the Variation of the Effect of Natural Gas Fraction on Dual-Fuel Combustion of Diesel Engine Under Low-to-High Load Conditions

Natural gas-diesel dual fuel (NDDF) engine has the potential to significantly reduce carbon dioxide (CO2) and particulate matter (PM) emissions, while retaining diesel engine’s high efficiency and reliability. The operation and performance of NDDF engine depend on natural gas energy fraction (%NG), which ranges from low %NG, where diesel fuel provides most of the combustion energy, to high %NG where diesel fuel is used only to initiate combustion. Although pertaining published studies demonstrated that the effect of %NG on the combustion performance and emissions of NDDF engine depend upon the engine load, none of these studies discussed the reasons behind this dependence. The present study attempts to shed light on this issue by experimentally and numerically investigating the effect of different %NGs on NDDF engine under different load conditions. Both experimental and numerical results revealed that the peak pressure rise rate (PPRR) first increases and then drops with increasing %NG under all load conditions. The calculated local equivalence ratio and charge temperature contours showed that increasing %NG to a certain limit increases local equivalence ratio inside the ignition kernel which implies that more premixed natural gas – air mixture participates in reactions during the premixed combustion stage. This results in an increased flame temperature and higher PPRR right after ignition. However, increasing %NG beyond this range decreases local equivalence ratio inside the ignition kernel which leads to lower PPRR. Increasing %NG retards the combustion phasing at low to medium load conditions. However, increasing %NG generally advances the combustion phasing under medium to high load conditions due to the fact that the flame propagation speed of natural gas – air mixture increases with %NG at medium to high load conditions. Methane emissions grow with increasing %NG under all examined engine load conditions. However, this growth becomes much smaller under medium to high engine load conditions. Increasing %NG significantly increases GHG emissions under lower load conditions. However, using advanced diesel injection timing decreases GHG emissions of NDDF engine under lower load conditions. Increasing %NG decreases GHG emissions by 6 to 11% under medium to high load conditions.

Normative Values for Cardiopulmonary Exercise Stress Testing Using Ramp Cycle Ergometry in Children and Adolescents

To provide sex, age, and race specific reference values for ramp cycle ergometer cardiopulmonary exercise test (CPET) in children in the US. Retrospective review was conducted of all cardiopulmonary CPET data from our Exercise Physiology Laboratory on healthy children and adolescents (6-18years) with body mass index between the 5th and 95th percentiles and structurally normal hearts who performed a ramp cycle ergometry stress test between 1999 and 2015. Twenty-eight exercise variables were included: peak oxygen consumption, oxygen consumption at ventilatory anaerobic threshold, peak work rate, resting and peak heart rate and blood pressure, resting pulmonary function testing, and ventilatory responses to progressive exercise using breath-by-breath gas exchange. Owing to the nonlinear association between CPET results and age, fractional polynomials were used in the mixed-effects regression models to describe the sex- and age-specific normative values with 95% CIs, after adjusting for race and body mass index. We analyzed data on 1829 children (average age, 13.6±2.6years; 52% male). After 12years of age, males generally had higher peak values for aerobic capacity and work rate. There were progressive increases with age for both sexes in resting pulmonary function and ventilatory response to exercise, peak aerobic and work rate, and oxygen pulse. Notably, there was an age-related decrease in ventilatory equivalents of oxygen and carbon dioxide at the ventilatory anaerobic threshold. Future research using prospective, inclusive, and statistically planned cohorts with standardized laboratory approaches and confirmed interoperability should be considered as a focus for validating normative pediatric CPET values in the future.

Glycolaldehyde-Derived High-Molecular-Weight Advanced Glycation End-Products Induce Cardiac Dysfunction through Structural and Functional Remodeling of Cardiomyocytes.

High-molecular-weight advanced glycation end-products (HMW-AGEs) are abundantly present in our Western diet. There is growing evidence reporting that HMW-AGEs contribute to the development of cardiovascular dysfunction in vivo, next to the well-known low-molecular-weight AGEs. The goal of our study is to assess the ultrastructure and function of cardiomyocytes after chronic exposure to HMW-AGEs. A better understanding of underlying mechanisms is essential to create new opportunities for further research on the specific role of HMW-AGEs in the development and progression of cardiovascular diseases. Adult male rats were randomly assigned to daily intraperitoneal injection for six weeks with either HMW-AGEs (20 mg/kg/day) or a control solution. Hemodynamic measurements were performed at sacrifice. Single cardiomyocytes from the left ventricle were obtained by enzymatic dissociation through retrograde perfusion of the aorta. Unloaded cell shortening, time to peak and time to 50% relaxation were measured during field stimulation and normalized to diastolic length. L-type Ca2+ current density (ICaL) and steady-state inactivation of ICaL were measured during whole-cell ruptured patch clamp. Myofilament functional properties were measured in membrane-permeabilized cardiomyocytes. Ultrastructural examination of cardiac tissue was performed using electron microscopy. Rats injected with HMW-AGEs displayed in vivo cardiac dysfunction, characterized by significant changes in left ventricular peak rate pressure rise and decline accompanied with an increased heart mass. Single cardiomyocytes isolated from the left ventricle revealed concentric hypertrophy, indicated by the increase in cellular width. Unloaded fractional cell shortening was significantly reduced in cells derived from the HMW-AGEs group and was associated with slower kinetics. Peak L-type Ca2+ current density was significantly decreased in the HMW-AGEs group. L-type Ca2+ channel availability was significantly shifted towards more negative potentials after HMW-AGEs injection. The impact of HMW-AGEs on myofilament function was measured in membrane-permeabilized cardiomyocytes showing a reduction in passive force, maximal Ca2+ activated force and rate of force development. Ultrastructural examination of cardiac tissue demonstrated adverse structural remodeling in HMW-AGEs group characterized by a disruption of the cyto-architecture, a decreased mitochondrial density and altered mitochondrial function. Our data indicate that HMW-AGEs induce structural and functional cellular remodeling via a different working mechanism as the well-known LMW-AGEs. Results of our research open the door for new strategies targeting HMW-AGEs to improve cardiac outcome.

Effects of injection timing and rail pressure on combustion characteristics and cyclic variations of a common rail DI engine fuelled with F-T diesel synthesized from coal

The use of Fischer-Tropsch (F-T) diesel synthesized from coal in automobiles can alleviate the shortage of petroleum and promote clean utilization of coal. In this study, the effects of injection timing (IT) and rail pressure (RP) on the brake thermal efficiency (BTE), combustion characteristics, and cyclic variations of F-T diesel were investigated on a turbocharged, 6-cylinder, common rail direct injection (CRDI) diesel engine. The results indicate that increasing RP results in higher BTE, whereas advancing IT results in an initial BTE increase and a subsequent BTE decrease. In comparison with petroleum diesel, the BTE of F-T diesel increased by 0.54% on average and by a maximum of 1% under different conditions. When the IT was advanced from 2 °CA to 18 °CA BTDC, the ignition delay periods (IDP) first decreased and then increased, whereas the combustion durations (CD) first lengthened and then shortened; peak cylinder pressure (PCP), peak pressure rise rate (PPRR), and peak combustion temperature (PCT) gradually increased; peak heat release rate (PHRR) first decreased and then increased at the low loads, whereas it always increased at medium and high loads. In comparison with petroleum diesel, the IDP of F-T diesel decreased by 22–31% at various conditions, and the CD was slightly longer than that of petroleum diesel at most conditions. Additionally, increasing RP resulted in a decrease in the IDP and CD, and a significant increase in PCP, PPRR, PHRR, and PCT. At low loads, the PPRR and PHRR of F-T diesel were 32.72% and 32.13% lower than that of diesel owing to the shorter ignition delay. This implies that using F-T diesel can help in attaining smoother engine running and has lower combustion noise. Advancing the injection timing or increasing the engine loads can decrease the cyclic variations, whereas increasing rail pressure results in the increment of COVpmax at low loads and the significant decrement of COVpmax at medium and high loads. In comparison with petroleum diesel, F-T diesel exhibits higher combustion stability owing to the better volatility and higher fuel reactivity.

Therapeutic effects of KANK2 in myocardial infarction rats might be associated with the NF-κB p65 inhibition

ObjectiveKN motif and ankyrin repeat domains 2 (KANK2) may inhibit the activation of (NF-kappaB) p65, which plays a role in myocardial injury. Thus, our study aims to discover the effect of KANK2 on myocardial infarction (MI) induced by ligating the left anterior descending coronary artery (LAD) through regulating NF-κB p65 in vivo. MethodsMI rats underwent LAD ligation were administered with intramyocardial injections of KANK2/Control activation plasmids. Six weeks after MI, pressure-volume (P/V) loops was used to investigate the cardiac function of rats, then the following detections were performed, including TTC staining, HE staining, immunofluorescence, Masson’ s trichrome staining, ELISA assay, TUNEL staining, immunohistochemistry, qRT-PCR and Western blotting. ResultsMI rats decreased in maximum pressure (pmax), ejection fraction (EF%), peak rate of pressure rise (dpdtmax) and decline (-dpdtmax) with increased end diastolic pressure (EDP), which was partially reversed by KANK2 overexpression. Besides, KANK2 CRISPR activation plasmids reduced infarct size with less collagen fiber proliferation and neutrophil infiltration in infarct tissues, as well as suppressed pro-inflammatory factors expressions in MI rats. Moreover, injection of KANK2 activation plasmid decreased collagen deposition, aggravated cardiomyocyte apoptosis, enhanced the capillary density, and increased the expressions of VEGF and bFGF in the infarct and peri-infarct regions of MI rats. KANK2 lowered myocardial NF-κB p65 expression in MI rats. ConclusionKANK2 may play its therapeutic role in MI through improving cardiac function, decreasing myocardial collagen deposition, reducing cardiomyocyte apoptosis, and increasing angiogenesis, which might be associated with the reduction of NF-κB p65 expression.

Effect of hydrogen addition on the operating characteristics of a free piston linear engine

A free piston linear engine (FPLE) with glow plug ignition was designed and manufactured. This paper investigated effects of hydrogen addition on the FPLE performance and emission characteristics. Experimental results showed that the FPLE can be started manually and then steady FPLE operating state is achieved. Compared with the crankshaft model engine, the FPLE has a greater speed around the top dead centre. The peak acceleration of the FPLE (4100 m/s2) is more than three times greater than that of the crankshaft model engine. Results also showed that the FPLE performance including the indicated power, indicated thermal efficiency and indicated mean effective pressure improves remarkably with hydrogen addition. The optimal FPLE performance is achieved when the hydrogen volume fraction is 4%. However, the engine performance cannot be further improved when the hydrogen volume fraction continues to increase due to the occurrence of over-advanced combustion phasing. Moreover, the FPLE operating range is significantly broaden and the operating stability is improved with hydrogen addition since the fast burning speed and wide flammability of hydrogen. Besides, the heat release rate, in-cylinder peak pressure and pressure rise rate are also obviously enhanced. The high-speed flame images showed the flame color becomes lighter and the yellow area is smaller compared with that of pure methane condition, indicating that the hydrogen addition to the fuel contributes to burn completely and reduce the soot formation.

Experimental study on knocking combustion in compressionignition engines under high-altitude conditions

Diesel engine combustion becomes very rough or even detonation under high altitude conditions, which is harmful to components durability. In this study, combustion characteristics were experimentally investigated on a V6 heavy-duty diesel engine using by a plateau simulation test bench to simulate altitude conditions of 1000 m, 3000 m and 4500 m. Results show that extremely high peak pressure rise rates of above 50bar/°CA exist at low speeds under the altitude of 4500 m. This indicates that not only does knocking combustion exist in spark-ignition (SI) engines, but also can be found in compression-ignition (CI) engines. Knock intensity (KI) is calculated by the pressure oscillation with high-pass filtering (HPF). Approach of cycle to cycle variation was adopted to study combustion characteristics on the comparisons of knock and non-knock states. Also, the correlation between KI and peak pressure rise rate was revealed through the linear regression method.

Quantifying Contributions of Cellular Mechanical Myocardial Properties on Left Ventricular Contractile Function in Aortic Banded Rats

Left ventricular (LV) contractile dysfunction is known to be associated with altered cellular myocardial properties. Quantitative translation from cellular mechanical properties to whole-organ cardiomyopathy phenotype, however, is an ongoing challenge. To quantitatively map cell-level pathophysiology to whole-organ contractile function in aortic banded (AB) 6-weeks post-surgery rats (Røe et al. 2017), we consider an in silicomodel of LV hypertrophy which combines mathematical models of cellular electrophysiology and calcium dynamics, sarcomere contraction and whole-organ mechanics solved over geometries derived from control and AB rat hearts. The resulting multi-scale computationally expensive model is regulated by >100 parameters. To assess parameters impact on the model outputs we developed a computationally effective approach for global sensitivity analysis (GSA) of rat cardiac mechanics based on Gaussian process (GP) emulation. We identified eight key parameters regulating ventricular mechanics such as myofilament calcium sensitivity (Ca50), and described the LV contractile function using eleven measurements including ejection fraction (EF) and pressure-volume loop. We found Ca50 to be the most significant parameter in explaining the total variance in both the control and AB rat (56%, 53%, 56%, 57% of the total variance of EF, isovolumetric relaxation time, peak pressure and maximum pressure rise rate, respectively, in control, and 65%, 47%, 58%, 56%, respectively, in AB rat). Calcium unbinding rate from Troponin C and maximal cellular tension yielded, respectively, the second and the third highest impact on the above LV features' total variances. Tissue stiffness and cross-bridge cycling rate impacted EF, ejection time, diastolic time and peak and end-systolic pressure features in the AB rat only. Our GP-based GSA approach enables computationally efficient identification of key components in 3D ventricular mechanics models, a potential path towards discovering new targets for heart failure treatment.

EFFECTS OF WATER EMULSIFIED B5-DIESEL AND BIOGAS ON THE COMBUSTION AND EMISSIONS OF RCCI ENGINE AT LOW LOAD

An experiment was conducted to investigate the effects of water in biodiesel emulsions (WiBE) and biogas on the reactivity-controlled compression ignition combustion for improved performance and reduced emissions. 13% WiBE, 15% WiBE and regular B5 were, directly, injected with the port injection of biogas at the intake valve, as a modified fueling approach. An advanced injection timing of 21o CA BTDC and energy fraction of 50% each of the fuels, were maintained at a speed of 2000 rpm and vary the load from 4.5 to 6.5 bar IMEP. The combustion of WiBE and biogas had been found disadvantageous to the rise in the cylinder pressure and heat released at high load but highly beneficial in reducing peak pressure rise rate besides lowering the in-cylinder temperature as a useful tool for low-temperature combustion technique. The use of WiBE and biogas resulted in a retarded combustion phase while B5 demonstrated more delayed combustion. Both 13% and 15% water emulsions exhibited similar carbon dioxide emission attributes but remained higher compared to the regular B5 at all the engine capacity except 6.5 bar IMEP. The fuels reactivity lowers significantly, the in-cylinder temperature causing elevated carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions, by 41.09% and 19.61% respectively, along with the reduced nitrogen oxides emission by 50.85%. Use of strategies to raise the in-cylinder temperature may cut down the challenging emissions

Numerical Studies on Combustion Characterization of Four Stroke Diesel Engine

Combustion simulation helps us to predict the pollutant formation and allows us to understand various coupling phenomena of physical and chemical processes. Diesel engine combustion simulation requires models of the spray dynamics, chemistry and heat transfer. The interaction between the chemistry and turbulence is one of the major parameters which had been modelled. Combustion simulation has been carried out by using Computational Fluid Dynamics (CFD). CFD model solves three-dimensional Naiver-Stokes equations with k-ε turbulence model. Combustion simulation has been carried out for one cycle by considering the two strokes compression and expansion with no load conditions. Fuel injection begins at 725 CA ends at 748 CA. Charge motion within the cylinder, turbulent kinetic energy, peak pressure rise, penetration length, and apparent heat release rate were analysed with respect to crank angle.

Sex-differences in aortic stenosis: Effect on functional capacity and prognosis

BackgroundThe patterns of left ventricular (LV) remodeling in aortic stenosis (AS) are different in men and women. We aimed to assess whether there were also sex differences in measurements obtained on exercise testing. MethodsEchocardiography and ETT (modified Bruce) were performed at presentation in 316 patients with moderate or severe AS. An early rapid rise in heart rate (RR-HR) during ETT was defined as achieving at least 85% of target heart rate or ≥50% increase from baseline within the first 6 min. ResultsMean age was 66 ± 12 years in men (n = 212) and 65 ± 12 years in women (n = 104) (p = NS). Men walked longer than women on the treadmill (10.4 ± 4.3 vs. 8.2 ± 4.2 min, p < 0.001) and achieved higher METs (9.2 ± 4.5 vs. 7.6 ± 4.3, p < 0.001), but both sexes achieved similar levels of peak heart rate and blood pressure. During a mean follow up of 34.9 ± 34.6 months, 29 deaths occurred (20 in men and 9 in women, p = 0.821). Age and body mass index were strong determinants of lower METs in men, but not in women, while Zva was a determinant in women but not in men. RR-HR was a strong determinant of lower METs in both sexes. Event-free survival was significantly lower in men with RR-HR but not in women. ConclusionExercise capacity was lower in women than men, and the determinants of exercise capacity differed. An RR-HR was a strong determinant of lower METs in both sexes, but predicted all-cause mortality only in men.

Improved combustion and emission characteristics of ethylene glycol/diesel dual-fuel engine by port injection timing and direct injection timing

In this study, the performance of a diesel–ethylene glycol (DEG) dual-fuel engine with four low EG energy ratios (named EG0, EG5, EG10 and EG15 respectively) is tried to improve by port injection timing (PIT) and direct injection timing (DIT). The combustion results show that combustion process is even highly affected by DIT than by PIT. Peak cylinder pressure, peak heat release rates (PHRRs) and pressure rise rate increase with the augmentation of EG energy ratios and advanced DIT. Combustion duration decreases with the increase of EG energy ratios and advanced DIT. Brake thermal efficiency (BTE) can be improved 19.45% by raising EG energy ratios and advancing DIT. In consideration of emission, the emissions of NOx, THC, CO2 and soot decrease followed by the rise of EG energy ratio at the same time, while CO emission increases. The emission is more obviously affected by DIT than PIT. The emission of soot and THC decreases with advanced DIT, while the emission of CO2 and NOx increases. Advanced DIT can reduce PM, and EG can decrease the average diameter of PM. Overall, the advanced DIT, suitable EG energy ratio and proper PIT are expected to achieve optimization on DEG dual-fuel engine in the aspect of performance and emissions.

Effects of direct-injection fuel types and proportion on late-injection reactivity controlled compression ignition

The late-injection strategy can decrease peak pressure rise rate (PRR) in reactivity controlled compression ignition (RCCI) and enables RCCI operation to high engine load. However, excessive soot emission is a limiting factor in this high engine load extension. Recently, polyoxymethylene dimethyl ethers (PODE) emerges as a promising direct-injection fuel for RCCI load extension due to the properties of high reactivity and high oxygen content. The late-injection RCCI strategy features a two-stage high-temperature heat release (HTHR) that has not been well understood. In this study, we investigated the effects of direct-injection fuel properties types and proportion on late-injection RCCI strategy on a light-duty optical engine using multiple optical diagnostic techniques. Iso-octane served as the premixed fuel and the in-cylinder direct-injection timing was set at the crank angle of −10° after the top dead center. Firstly, the combustion characteristics of RCCI with direct-injection fuels of n-heptane, PODE and cetane were compared. The NFL images prove that the PODE case shows less tendency of soot formation. The OH planar laser-induced fluorescence (PLIF) imaging indicates that the OH radical is widely distributed in the combustion chamber after the HTHR including the central part of the combustion chamber near the injector nozzle for all three cases. Secondly, the effects of direct-injection fuel proportion on the combustion characteristics of the late-injection RCCI strategy was evaluated using PODE as the direct-injection fuel. The NFL images show that the combustion regime in the low reactivity region of RCCI tends to change from auto-ignition to flame front propagation with the decreasing of the direct-injection fuel proportion from 30% to 6%. The introduction of the flame front propagation in the second-stage HTHR reduces the peak pressure rise rate of RCCI. We conclude that the peak PRR of RCCI at high engine load can be controlled by modulating the ratio between the auto-ignition and flame front propagation through tuning the proportion of the high-reactivity fuel in the direct injection.