Dilution Tolerance Research Articles

Ag+-Induced Supramolecular Polymers of Folic Acid: Reinforced by External Kosmotropic Anions Exhibiting Salting Out.

Introducing kosmotropic salts enhances protein stability and reduces solubility by withdrawing water from the protein surface, leading to 'salting out', a phenomenon we have mimicked in supramolecular polymers (SPs). Under the guidance of Ag+, folic acid (FA) self-assembled in water through slipped-stacking and hydrophobic interactions into elongated, robust one-dimensional SPs, resulting in thermo-stable supergels. The SPs exhibited temperature and dilution tolerance, attributed to the stability of the FA-Ag+ complex and its hydrophobic stacking. Importantly, FA-Ag+ SP's stability has been augmented by the kosmotropic anions, such as SO42-, strengthening hydrophobic interactions in the SP, evident from the enhanced J-band, causing improvement of gel's mechanical property. Interestingly, higher kosmotrope concentrations caused a significant decrease in SP's solubility, leading to precipitation of the reinforced SPs─a 'salting out' effect. Conversely, chaotropes like ClO4- slightly destabilized hydrophobic stacking and promoted an extended conformation of individual SP chain with enhanced solubility, resembling a 'salting in' effect.

Piston geometry and stroke optimization for high efficiency propane spark ignition engines

Propane has unique properties and offers interesting characteristics for high-efficiency spark ignition engines. Its high volatility reduces or completely eliminates fuel-wall wetting and facilitates fuel air mixing. Furthermore, propane has a research octane number of 112 and a high octane sensitivity of 15. Finally, its laminar flame speed is on the same order as that of conventional gasoline, and it exhibits high dilution tolerance. Modern spark ignition internal combustion engines rely on fast combustion rates and high dilution to achieve high brake thermal efficiencies. To accomplish this, high stroke-to-bore ratios and high geometric compression ratios have been used in new engine designs. Therefore, propane’s relatively high laminar flame speeds, high knock resistance, and dilution tolerance make it an excellent candidate fuel for modern spark ignition engines. The objective of this work is to co-optimize the piston geometry and the engine stroke to maximize the efficiency of a spark-ignition engine fueled with propane. 3D computational fluid dynamics (CFD) simulations employing the extended coherent flamelet model were used to study the parametric effects of piston shape and stroke length. A piston geometry based on high performing pistons was parameterized using four controlling parameters. The piston geometry and engine stroke design space was explored using deterministic and quasi-random sampling techniques. A Gaussian process regression model was built using the simulation data to explain the results observed.

Influence of Passive Pre-Chamber Nozzle Diameter on Jet Ignition in a Constant-Volume Optical Engine under Varying Load and Dilution Conditions

<div>Despite the growing prominence of electrified vehicles, internal combustion engines remain essential in future transportation. This study delves into passive pre-chamber jet ignition, a leading-edge combustion technology, offering a comprehensive visualization of its operation under varying load and dilution conditions in light-duty GDI engines. Our primary objectives are to gain fundamental insights into passive pre-chamber jet ignition and subsequent main combustion processes and evaluate their response to different load and dilution conditions. We conducted experimental investigations using a light-duty, optical, single-cylinder engine equipped with three passive pre-chamber designs featuring varying nozzle diameters. Optical diagnostic imaging and heat release analysis provided critical insights. Findings reveal that as load decreases, fuel availability and flow conditions deteriorate, leading to delayed and suboptimal jet characteristics impacting main chamber ignition and combustion. Notably, at high and medium loads without dilution, the 1.2 mm-PC (smallest nozzle diameter) excels, exhibiting superior jet ignition and main combustion. This is attributed to earlier jet ejection, improved penetration, and intensified jets, all enabled by the smaller nozzle diameter. Conversely, under low load conditions, the 1.6 mm-PC (largest nozzle diameter) performs better due to enhanced scavenging and reduced pre-chamber residuals, resulting in more balanced pre-chamber combustion and jet characteristics. Furthermore, nozzle diameter significantly influences cycle-to-cycle variations, with smaller diameters enhancing jet ignition but intensifying variability. The impact of external residuals (dilution) on jet ignition performance varies with nozzle diameter, with the 1.6 mm-PC displaying less degradation and demonstrating earlier jet ejection and CA50 timing under higher dilution conditions. In summary, this research underscores the importance of scavenging and residual levels in pre-chamber design, influencing dilution tolerance, and extending possibilities for high-efficiency engines. It contributes essential insights into the behavior of passive pre-chamber jet ignition systems, facilitating their optimization for future internal combustion engines.</div>

Low-carbon fuels for spark-ignited engines: A comparative study of compressed natural gas and liquefied petroleum gas on a CFR engine with exhaust gas recirculation

Decades of work on low-carbon fuels have established their potential for substantial emissions reductions; however, their adoption is still limited by infrastructure concerns and engine efficiency deficits. As infrastructures have begun to evolve, research on strategies that maximize engine efficiency through interactions with fuel properties must also now take center place. This paper compares the performance, emissions, and combustion characteristics of two forefront low-carbon fuels: compressed natural gas (CNG) and liquefied petroleum gas (LPG) in a cooperative fuel research (CFR) engine over a range of compression ratios and engine loads. The effects of exhaust gas recirculation (EGR), end-gas auto-ignition, and a novel combustion control tool, the combustion intensity metric (CIM), were also evaluated at different stoichiometric engine operating conditions. In comparison to LPG, CNG operation demonstrated an extended knock-free regime, allowing engine operation at higher engine loads and compression ratios, but LPG operation exhibited enhanced combustion characteristics with higher peak pressures and faster apparent heat release rates (AHRR). LPG operation achieved higher brake thermal efficiencies and lower equivalent CO2 emissions compared to CNG operation at the tested engine loads and compression ratios. LPG demonstrated significantly higher EGR tolerance limits compared to CNG, with a maximum of 28% EGR rate, compared to 23% for CNG. This improved EGR dilution tolerance was responsible for a 90% reduction in NOx emissions for LPG compared to a maximum of 70% with CNG. EGR dilution also exhibited more effective knock mitigation potential with LPG, suppressing knock intensity values by up to 98% and transitioning the engine operation towards normal combustion from heavy knocking conditions. The CIM was found to decrease burn durations and improve the quality of combustion by controlling the desired fraction of end-gas auto-ignition.

Estimation of transient intake burned gas and reformate mass fractions in a dedicated EGR engine

An engine with a cylinder dedicated to providing enriched EGR (D-EGR) has been demonstrated by Southwest Research Institute (SwRI). A vehicle equipped with the D-EGR engine showed more than 10% of fuel economy improvement over various driving cycles. Despite a much higher level of EGR than a conventional engine, combustion in the engine is maintained stable since reformates such as H2 and CO from rich combustion increase dilution tolerance. Thus, it is deemed that precise real-time information of the level of reformates in the engine is critical to maintain stable combustion especially during transients. In this paper, a method to estimate intake burned gas and reformate mass fractions of the D-EGR engine is developed and validated through simulations. The estimated fractions can be used to control spark timing in real-time to prevent knocking or misfire during transients in the D-EGR engine.

Impact of Passive Pre-Chamber Nozzle Diameter on Jet Formation Patterns and Dilution Tolerance in a Constant-Volume Optical Engine

<div>Pre-chamber jet ignition technologies have been garnering significant interest in the internal combustion engine field, given their potential to deliver shorter burn durations, increased combustion stability, and improved dilution tolerance. However, a clear understanding of the relationship between pre-chamber geometry, operating condition, jet formation, and engine performance in light-duty gasoline injection engines remains under-explored. Moreover, research specifically focusing on high dilution levels and passive pre-chambers with optical accessibility is notably scarce. This study serves to bridge these knowledge gaps by examining the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance. Utilizing a modified constant-volume gasoline direct injection engine with an optically accessible piston, we tested three passive pre-chambers with nozzle diameters of 1.2, 1.4, and 1.6 mm, while nitrogen dilution varied from 0 to 20%. With the help of high-speed imaging, we captured pre-chamber jet formations and subsequent flame propagation within the main chamber. Our novel findings reveal that asymmetric temporal and spatial jet formation patterns arising from pre-chambers significantly impact engine performance. The larger-nozzle-diameter pre-chambers exhibited the least variation in jet formation due to their improved scavenging and main mixture filling processes, but had the slowest jet velocity and lowest jet penetration depth. At no dilution condition, the 1.2 mm-PC demonstrated superior performance attributed to higher pressure build-up in the pre-chamber, resulting in accelerated jet velocity and increased jet penetration depth. However, at high dilution condition, the 1.6 mm-PC performed better, highlighting the importance of scavenging and symmetry jet formation. This study emphasizes the importance of carefully selecting the pre-chamber nozzle diameter, based on the engine’s operating conditions, to achieve an optimal and balanced configuration that can improve both jet formation and jet characteristics, as well as scavenging.</div>

A Design Approach of a Dedicated Exhaust-Gas Recirculation-System for a Naturally Aspirated Gas Engine—From One-Dimensional Engine Process Simulation and Design of Experiments Up to the Experimental Validation

Abstract This work presents a systematic approach proceeding from the engine process simulation (one-dimensional (1D)-computational fluid dynamics (CFD)) and design of experiments (DoE) up to the experimental validation to build a dedicated exhaust-gas recirculation (EGR) system for a stationary four-cylinder naturally aspirated gas engine. This system should ensure an equal distribution of the recirculated exhaust gas, coming entirely from the rich-operated dedicated cylinder. The rich combustion enables an in-cylinder production of highly reactive species (mainly H2 and CO), resulting in increased EGR reactivity, which improves the dilution tolerance, leading to reduced wall heat losses and lower knock tendency in the EGR receiving cylinders. However, the EGR system design represents a challenge due to the pulsating exhaust gas flow from the dedicated cylinder, which leads to a considerable EGR maldistribution in the receiving cylinders. A numerical analysis of this effect demonstrated that the EGR distribution uniformity depends on the design and dimensions of the EGR path. Considering the numerous design parameters and taking into account that the optimum design of the EGR path is not necessarily the sum of optima from the one-factor-at-a-time variations, efficient DoE methodologies were applied. They enabled identifying the optimum set of the EGR path design-parameters, with an EGR rate maldistribution of about 1% points. To evaluate the quality of the numerical results, the dedicated EGR path with the optimum parameters set was built on the engine test bench. The experimental results confirm the simulative prediction accuracy, demonstrating the reliability of the pursued approach.

A direct numerical simulation study of the dilution tolerance of propane combustion under spark-ignition engine conditions

Modern spark ignition internal combustion (IC) engines rely on highly diluted fuel-air mixtures to achieve high brake thermal efficiencies. To support this, new engine designs have introduced high stroke-to-bore ratios and cylinder head designs that promote high tumble flow and turbulence intensities. However, mixture dilution through exhaust gas recirculation (EGR) is limited by combustion instabilities manifested in the form of cycle-to-cycle variability. Propane has been observed to have superior EGR dilution tolerance than gasoline, which makes it a very competitive low-carbon fuel for the new IC engines without sacrificing efficiency. Two-dimensional direct numerical simulations (DNS) are performed with detailed chemistry to study and contrast the effect of turbulence intensity and dilution on propane and iso-octane premixed flames at high pressure conditions similar to those in-cylinder. A new reduced mechanism for propane consisting of 53 transported species and 17 quasi-steady state species is developed based on a previously published mechanism and used in these simulations. Three levels of turbulence intensity and two levels of exhaust gas dilution are chosen based on conditions relevant to IC engine operation. The DNS results are analyzed based on the evolution of the flame surface area and the statistics of its driving terms, which are found to be similar for both fuels when there is no dilution but considerably different under high dilution. The analysis of the DNS data provides fundamental insights into the underlying mechanisms for improved stability under dilution.

Effect of pre-chamber scavenging strategy on EGR tolerance and thermal efficiency of pre-chamber turbulent jet ignition systems

Dual Mode, Turbulent Jet Ignition (DM-TJI) is an engine combustion technology that incorporates an auxiliary air supply apart from the auxiliary fuel injection inside the pre-chamber of a divided chamber ignition concept. Compared to other active (auxiliary fueled) and passive pre-chamber ignition technologies, the DM-TJI system has the distinct capability to operate with very high level (up to ∼50%) of recirculated exhaust gas (EGR). Thus, unlike typical lean (excess air dilution) operated pre-chamber ignition technologies, the DM-TJI system enables the use of widely utilized low cost three-way-catalyst (TWC) while still running at high level of dilution (with EGR). The supplementary air supply to the pre-chamber enables effective purging and ignitable mixture formation inside the pre-chamber even with very high external EGR rate. The current work presents the results of experimental investigation conducted on a Prototype III Dual Mode, Turbulent Jet Ignition (DM-TJI) (or Jetfire ignition) single cylinder metal engine. Different pre-chamber scavenging/fueling strategies (active vs passive) were investigated in order to compare the EGR dilution tolerances between different scavenging configurations under identical pre-chamber design parameters (pre-chamber volume and nozzle configuration). Tests were conducted at two regularly encountered operating conditions (6 and 10 bar IMEPg at 1500 rpm) in typical drive cycles. Results are also compared with the conventional SI (spark ignition) configuration on the same engine. The results indicate that to maintain very high EGR diluted (up to ∼50%) operation the auxiliary air supply to the pre-chamber is of paramount importance. The analysis found that DM-TJI/Jetfire ignition system is more effective in terms of thermal efficiency at high load knock limited situation due to its considerably higher external EGR dilution tolerance. Higher EGR rate offered better combustion phasing and improved thermal efficiency considerably. It was found that with the elevated 13.3:1 compression ratio and 10 bar load, SI could not maintain knock free stable operation and DM-TJI/Jetfire delivered 7%–9% improvement in thermal efficiency compared to TJI mode of operation with no air delivery to the pre-chamber.

A study of the influence of orifice diameter on a Dual Mode, Turbulent Jet Ignition engine through variable engine speed

The increasingly strict worldwide emission regulations for internal combustion engines force car manufacturers to exploit innovative combustion technologies. One expects a change from pure thermal engines to more advanced internal combustion engine. A high engine compression ratio with high EGR dilution has an impact on increasing engine efficiency. A compelling concept to burn diluted combustion can be a DM-TJI combustion system, which consists of a pre-chamber and main chamber connected with one or more small orifices. This technology effectively achieves diluted combustion by improving engine dilution tolerance and knock performance. This paper focused on the impact of engine speed with variation in pre-chamber nozzle orifice diameter. Experiments were conducted with three different pre-chamber nozzle orifice diameters of 1.25, 1.5, and 1.75 mm with an engine speed range from 1500 to 2300 rpm. A numerical analysis was conducted to investigate the nozzle orifice diameter effect on the engine speed beyond 2500 rpm. Engine speed variation affects the performance of each orifice’s diameters. Small orifice diameter performs better for lower engine speed, and large orifice diameter performs better for higher engine speed. The 1.25 mm orifice diameter provided fast combustion. However, when the engine speed increases, the combustion stability suffers. Orifice diameter of 1.5 mm has better combustion stability in all tested speed ranges and higher efficiency in the speed range of 1500–2000 rpm, with a maximum indicated efficiency of 44.18%. The 1.75 mm orifice diameter performs better in the high engine speed ranges between 2100 and 2300 rpm, with a maximum indicated efficiency of 44.56% at an engine speed of 2300 rpm. This study has demonstrated the capability of the DM-TJI system to work with a high level of EGR dilution (up to 45%) and delivered a better indicated efficiency than the conventional spark ignition engines.

Exploring the part load lean limit of a direct injection spark ignition engine fueled with ethanol

Stringent environmental legislation demands development of internal combustion engines seeking higher thermal efficiency to reduce greenhouse gas emissions. Brazilian governmental programs like ROTA 2030 and RenovaBio drive the research and development of highly efficient engines fueled with biofuels, like sugarcane bioethanol, that has a near to zero carbon footprint. Some technologies such as gasoline direct injection, variable valve train, and turbocharging were implemented in downsized Spark Ignition (SI) engines in order to reach higher thermal efficiencies and decrease CO2 emissions. Homogeneous lean combustion in SI operation can improve fuel consumption and reduce exhaust gas emissions. However, it is limited by combustion instability and the three-way-catalyst (TWC) inability to work properly converting nitrogen oxides (NOx). With lean combustion the NOx emissions could be significantly reduced, enabling the use of lean NOx trap (LNT) as an effective lower cost after treatment system. To explore the limits of homogeneous lean combustion in SI engines, experimental tests were performed to investigate performance, efficiency, combustion, and emission parameters of a multi-cylinder Ford 1.0l Ti-VCT EcoBoost engine fueled with hydrous ethanol. Hydrous ethanol is a commercial Brazilian fuel which has greater laminar flame speed and higher dilution tolerance than gasoline, and thus can increase combustion stability. Different fuel direct injection strategies were explored at part load (below 8.0 bar IMEP) at engine speed of 1500 rpm. Air-to-fuel ratio was varied from stoichiometric (lambda 1.0) to lambda 1.5. The limit of stable homogeneous lean combustion (COVIMEP ≤ 3.0%) was achieved in lambda 1.4. The lowest indicated load of 2.1 bar IMEP was limited by combustion stability at lambda 1.3. The maximum indicated efficiency was 36.9% at indicated load of 8.0 bar IMEP and lambda 1.4. The NOx emissions dropped below 1.4 g/kWh at 4.0 bar IMEP and lambda 1.4.

Investigations into EGR dilution tolerance in a pre-chamber ignited GDI engine

EGR is a useful means to improve fuel economy in spark-ignited gasoline engines, especially under part-load conditions by means of reducing throttling losses. There is also a significant reduction in NOx emissions due to the reduced peak cylinder temperatures. However, the ability of conventional spark ignition systems to reliably ignite dilute mixtures limits the dilution tolerance due to the onset of combustion instability. In this study, an active pre-chamber system was evaluated at part load condition with various EGR rates using a regular grade full boiling range gasoline. A premixed air-fuel mixture was supplied to the pre-chamber, which assists in scavenging the residual mass fractions to enable reliable ignition of EGR dilute mixtures in the main combustion chamber. A range of pre-chamber injection, air-fuel mixture formulation, and ignition timing strategies were evaluated during the EGR sweeps. In addition, 0-D and 1-D simulations were conducted in GT-Power to assess the thermodynamic state and composition in the pre-chamber, as well as estimate the jet momentum at the various dilution rates. The active pre-chamber extended the EGR dilution limit from 20% for conventional SI to above 30%, with a higher pre-chamber flow rate (more scavenging) resulting in increased combustion stability. A tradeoff between the jet momentum and spark timing was observed when analyzing the GT-Power simulations and the pre-chamber jet momentum was found to decrease with increasing EGR rate. At unstable high EGR operation, no relation could be found between the pre-chamber indicated data and main chamber combustion stability.

Integrated machine learning-quantitative structure property relationship (ML-QSPR) and chemical kinetics for high throughput fuel screening toward internal combustion engine

This work proposes a high throughput fuel screening approach to identify molecules with desired properties for internal combustion engine at the early stage of property-oriented fuel design. The virtual screening is a funnel-like approach containing Tier 1 fuel physicochemical property screening and Tier 2 chemical screening. Tier 1 screening is based on the machine learning quantitative structure property relationship (ML-QSPR) models for 15 properties of melting point, boiling point, vapor pressure, enthalpy of vaporization, cetane number, research octane number, motor octane number, ignition temperature, flash point, yield sooting index, liquid density, lower heating value, surface tension, lower/upper flammability limit. The key is to identify the target values for the selected properties for a given engine architecture and combustion strategy. Tier 2 screening inspects the ignition delay time, ϕ-sensitivity and laminar flame speed to evaluate the fuel reactivity, the potential of ϕ stratification combustion, combustion rate and dilution tolerance. Merit function provides a simple tool to assess the potential benefit of fuel-engine interaction based on the properties computed in Tier 1 and Tier 2 screenings. A case study for boosted spark ignition engine is performed to showcase the fuel screening workflow. The virtual screening can accelerate the property-oriented fuel design in a time, resource, labor, cost-effective way and identify the promising candidates for the experimental test as ultimate validation. This paradigm aims at inspiring the new ideas of data-driven fuel screening and promoting the application in the energy sector.

EGR Dilution and Fuel Property Effects on High-Efficiency Spark-Ignition Flames

<div class="section abstract"><div class="htmlview paragraph">Modern spark ignition internal combustion engines rely on fast combustion rates and high dilution to achieve high brake thermal efficiencies. To accomplish this, new engine designs have moved towards increased tumble ratios and stroke-to-bore ratios. Increased tumble ratios correlate positively with increases in turbulent kinetic energy and improved fuel and residual gas mixing, all of which favor faster and more efficient combustion. Longer stroke-to-bore ratios allow higher geometric compression ratios and use of late intake valve closing to control peak compression pressures and temperatures. The addition of dilution to improve efficiency is limited by the resulting increase in combustion instabilities manifested by cycle-to-cycle variability. A number of effects - preferential diffusion, turbulence-combustion interactions, stochastic flow patterns, laminar-turbulent flame kernel transitions, and relative length and velocity scales between flame and turbulence - are believed to be responsible for the increase in cycle-to-cycle variations, where their contributions are likely interlinked. Several studies have shown the influence of stochastic flow characteristics on the nature of combustion instabilities, such as velocity patterns on flame kernel formation and cycle-to-cycle variations in residual gas. However, few have focused on the specific effects of fuel properties. The objective of this work is to contrast the effects of dilution on propane stoichiometric combustion against gasoline. Dilution tolerance experiments were conducted in a purpose-built high stroke-to-bore ratio single cylinder engine with both gasoline and LPG. Three-dimensional full cycle computational fluid dynamics (CFD) simulations employing a level-set combustion approach and Reynolds averaged Navier-Stokes (RANS) turbulence modeling was used to qualitatively assess the changes in length and velocity scales for turbulence and the flame. The experimental results showed that LPG can tolerate higher exhaust gas recirculation (EGR) dilution under a variety of conditions. Analysis of CFD simulations showed that propane flames are likely less sensitive to influences from the flow field due to less thickening of the flame and higher effective flame speeds.</div></div>

Comparison of Excess Air (Lean) vs EGR Diluted Operation in a Pre-Chamber Air/Fuel Scavenged Dual Mode, Turbulent Jet Ignition Engine at High Dilution Rate (~40%)

<div class="section abstract"><div class="htmlview paragraph">Charge dilution is widely considered as one of the leading strategies to realize further improvement in thermal efficiency from current generation spark ignition engines. While dilution with excess air (lean burn operation) provides substantial thermal efficiency benefits, drastically diminished NOx conversion efficiency of the widely used three-way-catalyst (TWC) during off-stoichiometric/lean burn operation makes the lean combustion rather impractical, especially for automotive applications. A more viable alternative to lean operation is the dilution with EGR. The problem with EGR dilution has been the substantially lower dilution tolerance limit with EGR and a consequent drop in thermal efficiency compared to excess air/lean operation. This is particularly applicable to the pre-chamber jet ignition technologies with considerably higher lean burn capabilities but much lower EGR tolerance due to the presence of a high fraction of residuals inside the pre-chamber. Dual Mode, Turbulent Jet Ignition (DM-TJI) technology with its unique ability to work with high external EGR dilution (up to 40% wet/mass basis) due to its additional air delivery to the prechamber offers a viable alternative to the lean burn strategy. DM-TJI could be the technology pathway to realize high EGR diluted combustion with comparable dilution limits to those of the lean burn strategy while still enabling effective use of TWC technology. Present study compares the excess air versus EGR dilution strategy under identical level of dilution (up to 40 %) in a DM-TJI equipped single cylinder engine operating on a high (13.3: 1) compression ratio. The results show that compared to the lean burn operation, EGR dilution provides marginally lower but still comparable thermal efficiency benefits with a marked improvement in NOx reduction, especially in a high compression, knock limited situation. This study showcases that high EGR dilution rates comparable to lean burn operation can be maintained with the DM-TJI system to achieve high thermal efficiency while still operating at stoichiometric air-fuel ratio.</div></div>

Encapsulating Halofuginone Hydrobromide in TPGS Polymeric Micelles Enhances Efficacy Against Triple-Negative Breast Cancer Cells.

BackgroundHalofuginone hydrobromide (HF) is a synthetic analogue of the naturally occurring quinazolinone alkaloid febrifugine, which has potential therapeutic effects against breast cancer, however, its poor water solubility greatly limits its pharmaceutical application. D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) is a water-soluble derivative of vitamin E, which can self-assemble to form polymeric micelles (PMs) for encapsulating insoluble anti-tumor drugs, thereby effectively enhancing their anti-cancer effects.MethodsHF-loaded TPGS PMs (HTPMs) were manufactured using a thin-film hydration technique, followed by a series of characterizations, including the hydrodynamic diameter (HD), zeta potential (ZP), stability, drug loading (DL), encapsulation efficiency (EE), and in vitro drug release. The anti-cancer effects and potential mechanism of HTPMs were investigated in the breast cell lines MDA-MB-231 and MCF-7, and normal breast epithelial cell line Eph-ev. The breast cancer-bearing BALB/c nude mouse model was successfully established by subcutaneous injection of MDA-MB-231 cells and used to evaluate the in vivo therapeutic effect and safety of the HTPMs.ResultsThe optimized HTPMs had an HD of 17.8±0.5 nm and ZP of 14.40±0.1 mV. These PMs exhibited DL of 12.94 ± 0.46% and EE of 90.6 ± 0.85%, along with excellent storage stability, dilution tolerance and sustained drug release in pH-dependent manner within 24 h compared to free HF. Additionally, the HTPMs had stronger inhibitory effects than free HF and paclitaxel against MDA-MB-231 triple-negative breast cancer cells, and little toxicity in normal breast epithelial Eph-ev cells. The HTPMs induced cell cycle arrest and apoptosis of MDA-MB-231 by disrupting the mitochondrial membrane potential and enhancing reactive oxygen species formation. Evaluation of in vivo anti-tumor efficacy demonstrated that HTPMs exerted a stronger tumor inhibition rate (68.17%) than free HF, and exhibited excellent biocompatibility.ConclusionThe findings from this study indicate that HTPMs holds great clinical potential for treating triple-negative breast cancer.

Effect of octane number and thermodynamic conditions on combustion process of spark ignition to compression ignition through a rapid compression machine

Spark assistance in homogeneous charge compression ignition (HCCI) is a promising method to improve combustion stability. Fundamental experiments were carried out in a rapid compression machine along with chemical kinetics analysis to investigate the complete combustion process of spark ignition to compression ignition (SICI) using ethanol-blended fuels. Five fuels, consisting of n-heptane, iso-octane and ethanol with different fractions, are divided into two groups. The fuels with different research octane number (RON) and motor octane number (MON) but identical octane sensitivity (S) are in the same group. The equivalence ratio is fixed at 0.5, and the experimental pressure covers the engine-relevant conditions (10–35 bar) while the target temperature ranges from 735 K to 860 K, overlapping most regions with negative temperature coefficient (NTC) of n-heptane and iso-octane. Results show that octane sensitivity with low RON has poor ability to evaluate fuel reactivity especially in the vicinity of “beyond MON” area due to low-temperature oxidation acceleration of ethanol. The influence of fuel reactivity, auto-ignition heat release amount and flame compression effect on knock intensity enhancement decreases in turn. The lower transition temperature and pressure at the time of auto-ignition is observed in the fuel with lower RON regardless of S, resulted from stronger LTHR and greater temperature rise from cool flame. The fuel with medium RON and S based on ethanol blending is more suitable for SICI combustion since it can make a better balance among knock intensity, dilution tolerance and control authority from flame in the conditions studied, which gives an insight into the effect of ethanol blends on combustion process and provides a reference for fuel design aimed at lean SICI combustion.

Impact of octane sensitivity and thermodynamic conditions on combustion process of spark-ignition to compression-ignition through an optical rapid compression machine

Spark assistance is an effective method to improve combustion stability of homogeneous charge compression ignition (HCCI) with lean mixture. Ethanol, a renewable energy, blended with commercial fuels is a promising method to deal with problems of energy safety and greenhouse gas (GHG) emission. However, the influence of ethanol blends on spark ignition to compression ignition is not clear. To this end, this study presents experimentally fundamental investigation on the compression ignition (with and without spark assistance) of ethanol-blended gasoline surrogate fuel in an optical rapid compression machine at the equivalence ratio of 0.5. Three fuels with different octane sensitivities (S) comprising n-heptane/iso-octane/ethanol were formulated and S is the difference between research octane number (RON) and motor octane number (MON). Effective temperature of experiments ranges from 730 K to 860 K, overlapping most of the temperature region with negative temperature coefficient (NTC) of iso-octane at the corresponding equivalence ratio, and the pressure is consistence with engine-relevant operating conditions. The results show that more fuel reactivity of ethanol than iso-octane at 860 K is not attributed to the NTC behavior of iso-octane but to the reactive species generation in ethanol oxidation. There is always a positive correlation between effective pressure and knock intensity (KI). At lower temperature (<785 K), higher S results in the lower KI, while at higher temperature (860 K), the heat amount released by auto-ignition instead of S has a dominant impact on KI. Moreover, buffer gas dilution tolerance is not merely affected by laminar speed itself but determined by the intensity of heat release ahead of auto-ignition. The intensity of these heat release is proportional to flame speed and lower heating value (LHV). High S fuel is more sensitive to extra dilution at a fixed thermodynamic condition due to lower energy content, while the overall ignition delay (OID) requirement of no auto-ignition in the end gas is similar reflecting certain independence of fuel type. Medium S fuel has the better relationship between the timescale of flame propagation and auto-ignition, which is more suitable for spark-ignition to compression-ignition (SICI). This investigation provides a reference to fuel design for real engine applications.

High Load Expansion of Catalytic EGR-Loop Reforming under Stoichiometric Conditions for Increased Efficiency in Spark Ignition Engines

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The use of fuel reformate from catalytic processes is known to have beneficial effects on the spark-ignited (SI) combustion process through enhanced dilution tolerance and decreased combustion duration, but in many cases reformate generation can incur a significant fuel penalty. In a previous investigation, the researchers showed that, by controlling the boundary conditions of the reforming catalyst, it was possible to minimize the thermodynamic expense of the reforming process, and in some cases, realize thermochemical recuperation (TCR), a form of waste heat recovery where exhaust heat is converted to usable chemical energy. The previous work, however, focused on a relatively light-load engine operating condition of 2000 rpm, 4 bar brake mean effective pressure (BMEP). The present investigation demonstrates that this operating strategy is applicable to higher engine loads, including boosted operation up to 10 bar BMEP. By controlling the reforming catalyst boundary conditions, it is possible to achieve fuel reforming without experiencing high temperature exotherms that could be damaging to the catalyst. Additionally, the thermodynamic air handling consequences of operating a highly dilute strategy at high loads is quantified. The results confirm that this operating strategy provides an efficiency benefit at all conditions investigated, with relative efficiency increases of 3-6%, and is therefore applicable over wider regions of the engine operating map.&lt;/div&gt;&lt;/div&gt;

Kinetically Stable Bicelles with Dilution Tolerance, Size Tunability, and Thermoresponsiveness for Drug Delivery Applications.

Mixtures of a phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine, DPPC) and a sodium-cholate-derived surfactant (SC-C5 ) at room temperature formed phospholipid bilayer fragments that were edge-stabilized by SC-C5 : so-called "bicelles". Because the bilayer melting point of DPPC (41 °C) is above room temperature and because SC-C5 has an exceptionally low critical micelle concentration (<0.5 mm), the bicelles are kinetically frozen at room temperature. Consequently, they exist even when the mixture is diluted to a concentration of 0.04 wt %. In addition, the lateral size of the bicelles can be fine-tuned by altering the molar ratio of DPPC to SC-C5 . On heating to ≈37 °C, the bicelles transformed into micelles composed of DPPC and SC-C5 . By taking advantage of the dilution tolerance, size tunability, and thermoresponsiveness, we demonstrated in vitro drug delivery based on use of the bicelles as carriers, which suggests their potential utility in transdermal drug delivery.