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Photodynamic therapy (PDT) has emerged as a promising strategy with higher selectivity and spatiotemporal control than conventional therapies. However, deep hypoxia in tumours has hampered the clinical use of PDT. In this study, a novel multifunctional cluster nanotheranostic agent (AuPd-BSA CN) was fabricated to generate a high amount of reactive oxygen species, regardless of oxygen dependence under 660 nm laser irradiation. The structure and properties of the AuPd-BSA CN were characterised using various technologies. The synthesised AuPd-BSA CN with high biocompatibility served as a superior photodynamic agent, showing prominent antitumour properties under laser irradiation. Additionally, the glucose oxidase-like activity of the AuPd-BSA CN synergistically enhanced the therapeutic performance. Notably, the intrinsic characteristics of the AuPd-BSA CN include dual-modal second near-infrared window fluorescence/photoacoustic imaging capabilities for monitoring and tracking the

Activatable fluorescence imaging in the second near-infrared window (NIR-II FL, 1000-1700 nm) is of great significance for accurate tumor diagnosis and targeting therapy. However, the clinical translation of most stimulus-activated nanoprobes is severely restricted by insufficient tumor response and out-of-synchronization theranostic process. Herein, an intelligent nanofactory AUC-GOx/Cel that possesses the "external supply, internal promotion" dual H

Compared with the near-infrared-I spectral window (NIR-I, 650–950 nm), a newly developed imaging and treatment window with a 1000–1700 nm range (defined as the NIR-II bio-window) has attracted much attention owing to its higher spatiotemporal resolution, increased tissue penetration depth and therapeutic efficacy. Herein, we designed a nanotheranostic platform (HC-AB NPs) via loading ammonia borane (AB) into hollow carbon nanoparticles (HCs) for NIR-II photoacoustic (PA) imaging-guided NIR-II hydrogenothermal therapy. Importantly, by exploiting the characteristics of beta zeolite as a hard template and a template-carbonization-corrosion process, the prepared HCs have excellent NIR-II absorption performance and AB loading capacity. With the high biocompatibility of HC-AB NPs, an efficient synergistic anti-tumor strategy has been achieved via high intratumoural accumulation and acid-stimulated H2 release as well as PA-guided precise NIR-II photothermal therapy. The HC-AB NPs as a promising nanotheranostic platform opens a new avenue for high-efficacy NIR-II hydrogenothermal therapy.

Stimuli-responsive silica nanoparticles are an attractive therapeutic agent for effective tumor ablation, but the responsiveness of silica nanoagents is limited by intrastimulation level and silica framework structure. Herein, a biodegradable hollow SiO2-based nanosystem (Ag2S-GOx@BHS NYs) is developed by a novel one-step dual-template (bovine serum albumin (BSA) and cetyltrimethylammonium bromide (CTAB)) synthetic strategy for image-guided therapy. The Ag2S-GOx@BHS NYs can be specifically activated in the tumor microenvironment via a self-feedback mechanism to achieve reactive oxygen species (ROS)-induced multistep therapy. In response to the inherent acidity and H2O2 at the tumor sites, Ag2S-GOx@BHS would accelerate the structural degradation while releasing glucose oxidase (GOx), which could efficiently deplete intratumoral glucose to copious amounts of gluconic acid and H2O2. More importantly, the sufficient H2O2 not only acts as a reactant to generate Ag+ from Ag2S for metal-ion therapy and improves the oxidative stress but also combines with gluconic acid results in the self-accelerating degradation process. Moreover, the released Ag2S nanoparticles can help the Ag2S-GOx@BHS NYs realize the second near-infrared window fluorescence (NIR-II FL) and photoacoustic (PA) imaging-guided precise photothermal therapy (PTT). Taken together, the development of a self-feedback nanosystem may open up a new dimension for a highly effective multistep tumor therapy.

Background Molecular imaging is of great benefit to early disease diagnosis and timely treatment. One of the most striking innovations is the development of multimodal molecular imaging technology, which integrates two or more imaging modalities, largely in view of making the best of the advantages of each modality while overcoming their respective shortcomings. Hence, engineering a versatile and easily prepared nanomaterial with integrating multimodal molecular imaging function holds great promise, but is still a great challenge. Materials and methods We firstly designed and synthesized a BDT-DPP conjugated polymer and then noncovalent self-assembly with phospholipid-polyethylene glycol endowed BDT-DPP with water solubility and biocompatibility. Followed by [Cu] labeling, the acquired multifunctional nanoparticles (NPs) were studied in detail for the photophysical property. The cytotoxicity and biocompatibility of DPP-BDT NPs were examined through MTT assay and H&E stained analysis. In addition, we investigated the accumulation of the NPs in HepG2 tumor models by positron emission tomography (PET) and photoacoustic (PA) dual-mode imaging. Results and discussion The DPP-BDT NPs exhibited excellent optical stability, strong near-infrared (NIR) light absorption as well as fine biocompatibility. After tail vein injection into the living mice, the PA signals in the neoplastic tissues were gradually increased and reached to the maximum at the 4-h post-injection, which was consistent with the PET analysis. Such strong PA and PET signals were attributed to the efficient NPs accumulation resulting from the enhanced permeability and retention (EPR) effect. Conclusion The biocompatible DPP-BDT NPs demonstrated to be strong NIR absorption property and PAI sensitivity. Besides, these novel DPP-BDT NPs can act not only as a PA imaging contrast agent but also as an imaging agent for PET.

To enhance the catalytic performance of catalysts for the ethanol steam reforming (ESR) reaction, a facile reverse micelle strategy was adopted to prepare a core@shell Ni–Cu@Ca–SiO2 (Ni–Cu@CS) nanoreactor composed of an ultra-small Ni–Cu alloy (∼2.8 nm) encapsulated in Ca-functionalized SiO2 nanoparticles. Benefiting from its core@shell structural features and unique components, the Ni–Cu@CS nanoreactor exhibited superior activity (69.91% H2 selectivity and 99.99% ethanol conversion) and stability compared to reference samples. The regenerated Ni–Cu@CS nanoreactor showed high stability, maintaining 98.14% ethanol conversion and only 1.98 mg gcat−1 h−1 in carbon deposition. The high catalytic performance of Ni–Cu@CS is attributed to not only its encapsulated structure, which effectively prevented the sintering of neighboring Ni–Cu alloy nanoparticles, but also to its Ca-functionalized porous SiO2 shell, suppressing the carbon deposition. Moreover, its porous thin shell facilitated the mass transfer and diffusion of reactants and products. Thus, the Ni–Cu@CS nanoreactor is expected to become a new type of high-efficiency nanoreactor for the ESR reaction.

Nanosystems responsive to a tumor microenvironment (TME) have recently attracted great attention due to their potential in precision cancer theranostics. However, theranostic nanosystems with a TME-activated consecutive cascade for the accurate diagnosis and treatment of cancer have rarely been exploited. Herein, an activatable theranostic nanosystem (Bi2S3-Ag2S-DATS@BSA-N3 NYs) is designed and constructed on the basis of a one-pot biomineralization method and surface functional modification to improve second near-infrared (NIR-II) fluorescence/photoacoustic (PA) imaging-guided photothermal therapy (PTT)/gas therapy (GT). Based on enhanced penetration and retention (EPR) effect-mediated tumor accumulation, the tumor-overexpressed glutathione (GSH) can accelerate hydrogen sulfide (H2S) generation from the nanoparticles by reacting with the encapsulated diallyl trisulfide (DATS). Meanwhile, the in situ released H2S can be used not only for gas therapy, but also to start the reduction of -N3(-) to -NH2(+), thereby enhancing the tumor-specific aggregation of NYs. As a result, the activatable nanosystems with excellent tumor accumulation and biodistribution could achieve an accurate NIR-II/PA dual-modality imaging for guiding the synergistic anticancer efficacy (PTT/GT). Thus, this work provides a promising TME-mediated continuously responsive strategy for efficient anticancer therapy.

Although nanomedicines have shown high performance in tumor theranostics, their anticancer activity is still limited by the drug delivery capacity, especially lack of targeting capability, poor tumor accumulation, and insufficient tumor deep-penetration. To address this challenge, a high biocompatibility nano-truck (BMP NT) with a two-stage delivery mechanism is designed and developed to achieve the precision therapeutic efficacy of cancer. In view of the enhanced permeability retention (EPR) effect, the surface cleavable layer of BMP NTs can be selectively removed by the overexpressed MMP-2 in a tumor-microenvironment to expose the hydrophobic segments for an induced "braking effect" strategy, resulting in a significant increase in tumor accumulation. Once internalized into cancer cells with the overproduced glutathione (GSH) and H2O2, the BMP NTs undergo the second-stage "unloading process" to release Mn2+ ions and ultrasmall Bi2S3@BSA nanoparticles, and the obtained Mn2+ ions can act as a Fenton-like catalyst for continuously catalyzing the endogenous H2O2 into highly toxic hydroxyl radicals (˙OH) for CDT. The GSH depletion will in turn improve the Mn2+-H2O2 reaction, further enhancing CDT efficiency. Meanwhile, the ultrasmall Bi2S3@BSA endows BMP NTs with excellent photothermal conversion ability to generate local hyperthermia and accelerate the intratumoral Fenton process, thus leading to an effective tumor therapeutic outcome in the synergistic function of CDT/photothermal therapy (PTT). Moreover, the BMP NTs can be used for in situ self-generation magnetic resonance imaging (MRI) and photoacoustic (PA) imaging to guide precision cancer therapy.

Developing new strategies to enhance drug accumulation in the tumor and therapeutic efficacy is of great importance in the field of tumor therapy. Herein, a peanut-like multifunctional nanomedicine (CuS-PGH NMs) made of CuS nanoparticles encapsulated in poly(l-lysine)(PLL)/glucose oxidase (GOx)-hyaluronic acid (HA) shells has been constructed via layer-by-layer (LbL) assembly, and shows good biocompatibility and effective multi-gradient therapy. Because of the enhanced permeability and retention (EPR) effect, the CuS-PGH NMs could significantly enhance the cellular uptake by tumors overexpressing CD44 receptors, which respond to hyaluronidase (HAase)-triggered surface charge conversion. Once internalized by the tumor, GOx was the first to be exposed and could effectively deplete endogenous glucose for starvation therapy, and the excess H2O2 was then converted into highly toxic hydroxyl radicals (˙OH) via a Cu+-mediated Fenton-like reaction for chemodynamic therapy (CDT). Meanwhile, the as-obtained Cu+ ions accompanied the regenerated less-active Cu2+ ions. Interestingly, the high content of H2O2 could, in turn, accelerate Cu2+/Cu+ conversion to promote the Cu+-H2O2 reaction for enhanced chemodynamic therapy (CDT), thereby achieving efficient tumor growth suppression via synergistic starvation/CDT therapy. Subsequently, owing to the strong NIR-II absorption capability of CuS-PGH NMs, effective photothermal tumor ablation of the weakened tumor cells could be realized with the precise guidance of NIR-II PAI. This multi-gradient therapeutic strategy has been demonstrated to have excellent antitumor activity with minimal nonspecific damages, and offers a new avenue to precise tumor therapy.

GIS is an important power equipment in power system, which is the basis of ensuring power supply reliability. Although the reliability of GIS operation is very high, there are inevitable defects in GIS, such as partial discharge, insulation deterioration and equipment failure. A defect model is designed to simulate the suspended potential discharge in GIS, which can be used to simulate the common suspended potential discharge defects in GIS. It can be used to measure the partial discharge by combining the pulse current, UHF and decomposition component analysis methods, so as to promote the development of GIS partial discharge detection technology. The defect model consists of high voltage electrode, suspended potential body, ground electrode, fixture and SF6 gas. The results of partial discharge test show that the defect model can well simulate the suspended potential discharge in GIS equipment.

Fibroblast activation protein-α (FAP) is a type II integral serine protease that is specifically expressed by activated fibroblasts. Cancer-associated fibroblasts (CAFs) in the tumor stroma have an abundant and stable expression of FAP, which plays an important role in promoting tumor growth, invasion, metastasis, and immunosuppression. For example, in females with a high incidence of breast cancer, CAFs account for 50–70% of the cells in the tumor’s microenvironment. CAF overexpression of FAP promotes tumor development and metastasis by influencing extracellular matrix remodeling, intracellular signaling, angiogenesis, epithelial-to-mesenchymal transition, and immunosuppression. This review discusses the basic biological characteristics of FAP and its applications in the diagnosis and treatment of various cancers. We review the emerging basic and clinical research data regarding the use of nanomaterials that target FAP.

Stimuli-responsive silica nanoparticles are an attractive therapeutic agent for effective tumor ablation, but the responsiveness of silica nanoagents is limited by intrastimulation level and silica framework structure. Herein, a biodegradable hollow SiO

Multi-modality cancer diagnosis techniques based on the second near-infrared window fluorescence (NIR-II FL, 1000-1700 nm) imaging have become the focus of research attention. For such multimodality probes, how to take advantage of the tumor microenvironments (TME) characteristics to better image diseases and combine efficient therapeutics to achieve theranostics is still a big challenge. Herein, a novel TME-activated nanosystem (FMSN-MnO2 -BCQ) employing degradable silica-based nanoplatform is designed, adjusting the ratio of intratumoral hydrogen peroxide (H2 O2 )/glutathione (GSH) for magnetic resonance imaging (MRI)/NIR-II FL imaging and self-reinforcing chemodynamic therapy (CDT). Innovative bovine serum albumin (BSA)-modified fusiform-like mesoporous silica nanoparticles (FMSN) is fabricated as a carrier for NIR-II small molecule (CQ4T) and MRI reporter MnO2 . Remarkably, the BSA modification helped to achieve the dual-functions of high biocompatibility and enhance NIR-II fluorescence. The FMSN-MnO2 -BCQ with FMSN framework featuring a stepwise degradability in tumor interior released MnO2 and BCQ nanoparticles. Through the specific degradation of MnO2 by the TME, the produced Mn2+ ions are effectively exerted Fenton-like activity to generate hydroxyl radical (•OH) from endogenous H2 O2 to eradicate tumor cells. More importantly, the GSH depletion due to the synergistic effect of tetrasulfide bond and MnO2 in turn induced the oxidative cytotoxicity for self-reinforcing CDT.

A group of BEA@MFI core–shell zeolite catalysts were successfully constructed with Cu-, Ni-modified Beta core and Co-based Silicalite-1 shell by combining seed induction secondary growth technique and incipient wetness impregnation method. The resulting micro-composite possess a well-defined core–shell structure with high surface area and abundant mesopore in the outer shell, and a relative large truncated bi-pyramidal shape core of Beta. It was further used to correlate their performance in ethanol steam reforming. The obtained xNiyCu-Beta@Co-Silicalite-1 catalysts exhibited excellent catalytic performance compared with the conventional zeolite catalysts. Particularly, the 2.5Ni2.5Cu-Beta@CoSilicalite-1 catalyst exhibited the highest selectivity of hydrogen, the lowest selectivity of by-products, the long-term stability and coking-resistance capability. This is mainly attributed to the excellent textural properties. And the Ni, Cu nanoparticles which incorporated into the core–shell micro-composites protected the properties of active phases effectively. Moreover, the “purification effect” of the Co-base shell is conducive to obtaining high-purity hydrogen through a multiple reaction system.

Montmorillonite (Mt) plays a very important role in controlling drug delivery. In this paper, the hydrochloric acid (HCl) treated Mt. was exploited to obtain composites, which were able to enhance dexibuprofen (IBU) loading and achieve to sustain release drug. The textural properties of the Mt. were strongly dependent on the treatment of HCl. The drug loading of pristine Mt. was 190 mg/g, while it was increased to 298 mg/g for Acid-Mt. In vitro release showed that the IBU was released about 92% from IBU/Acid-Mt within 12 h, while the pure IBU was released all within 4 h in simulated intestinal fluid, which meant that the IBU/Acid-Mt were able to retard the drug release with a controlled manner. The release profiles of IBU from composites were fitted by Higuchi and Korsmeyer-Peppas equations, which manifested that diffusion sustained release dominated the main mechanism. Meanwhile, in vivo pharmacokinetics studies in rats displayed that the IBU/Acid-Mt exhibited better gradual drug release than the commercial IBU suspension. For the IBU/Acid-Mt composites, the area under the plasma concentration-time curve from 0 to 24 h (AUC0–24) and mean residence time (MRT0–24) were 644.49 ± 73.26 μg/h/mL and 7.65 ± 0.48 h, both of which were significantly larger than commercial IBU suspension (AUC0–24 of 439.88 ± 84.41 μg/h/mL and MRT0–24 of 3.10 ± 0.38 h), respectively (P

A novel Pt-CeO 2 @Ni-SiO 2 yolk-shell catalyst was fabricated through modified Stober method and was applied to the ethanol steam reforming reaction. The catalyst structure was characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, nitrogen adsorption-desorption and X-ray photoelectron spectroscopy. Compared with the mechanically mixed catalyst, the yolk-shell catalyst exhibited excellent catalytic performance and stability in ethanol steam reforming. The selection of hydrogen reached as high as 66%, and the conversion reached nearly 100% at 400 °C for 28 h.

High dispersion of Pt nanoparticles encapsulated in hollow Pt@HBZ microreactor has been successfully fabricated through the function of resorcinol-formaldehyde layer during the synthesis process. The low-temperature ethanol steam reforming (LT-ESR) on the Pt@HBZ was studied using various techniques with a focus on the structural characterization of the catalysts, reaction mechanism, and understanding of the structure-activity relationship. The results of steady-state-activity testing, comparisons with those from Pt-beta and Pt-SiO2 catalysts showed that the Pt@HBZ exhibited superior activity, stability and low by-products with negligible deactivation phenomena for 15 h during LT-ESR. The hindering effect of zeolite shell could effectively improve the concentration of relatively large molecules (i.e., ethanol and acetaldehyde) in the hollow micro-environment and promote the molecules reacted with Pt active sites to achieve a complete catalytic conversion. Moreover, due to the “purification effect” for the undesired products (CO, CH4, acetaldehyde and unreacted ethanol), the existence of a large number of microreactors in the reaction system can obtain high-purity hydrogen production.

In the second near-infrared (NIR-II) biowindow, multimodal optical imaging-guided precise antitumor therapy is a novel strategy for high-efficiency tumor theranostics, however, the all-in-one dual NIR-II photoacoustic (NIR-II PA) and NIR-II fluorescence (NIR-II FL) nanoprobes have been rarely reported mainly due to the short of a simple and universal design approach. Herein, a NIR-II PA/NIR-II FL imaging-adjustable nanozyme (HSC-2) is designed and developed to guide precise photothermal-catalytic synergistic therapy. Based on the ionic liquids adsorption capacity, the electronic structure of zeolite nano-Beta (three dimensional 12-ring pore system and large surface area) can be turned from the indirect band gap to direct band gap via doping carbon in the framework, resulting in outstanding NIR-II FL emission characteristics. As the silicon etching reaction proceeds, HSC-2 shows superior dual-modal NIR-II PA/NIR-II FL imaging performance facilitated by the optimal silicon-to-carbon ratio, simultaneously ensuring efficient tumor photothermal therapy (PTT) in the NIR-II window. Impressively, the peroxidase-mimic activity of HSC-2 in the tumor microenvironment could be further remarkably enhanced by its photothermal effect, leading to excellent synergistic PTT/catalytic therapy. Moreover, the HSC-2 exhibits dual-enzyme activity, and its catalase-like property could effectively eliminate excessive ROS for protection of the normal cells.

Ethanol steam reforming (ESR) has drawn great attention for sustainable H2 production. Design active and sinter resistant nanocatalysts are critical issues for ESR reaction. Herein, a core–shell structured Pt-Cu@Ni-SiO2 nanocomposite for ESR reaction has been synthesized via a one-pot facile encapsulation strategy, which is featured by highly active and sintering resistance for ESR reaction. Structural and morphological characterizations revealed that each Pt-Cu@Ni-SiO2 nanocomposite contained a 3 nm Pt-Cu core and multiple Ni nanoparticles with diameters of around 3 nm anchored on the SiO2 shell. The Pt-Cu@Ni-SiO2 nanoreactor exhibited higher ethanol conversion (99.99%) and H2 selectivity (70.32%) and an excellent stability with no loss of activity after 50 h of reaction at 450 °C. The advantages were originated from the ultra-small size of metal nanoparticles and the unique core–shell structure provides a great opportunity to give full play to the catalytic activity of active sites thus guaranteed excellent catalytic activity. Compared with the supported Pt-Cu@Ni-SiO2 catalyst, the Pt-Cu@Ni-SiO2 nanoreactor exhibit good stability and sintering resistance due to the encapsulation of the metal nanoparticles and the enhanced metal-support interaction. Thus, it is supposed that this type of catalyst opens a new strategy for the design of the ESR catalyst.

Bismuth-rich Bi4O5I2 nanosheets were prepared through progressive hydrolysis of urea in a facile solvothermal route, which is different from the conventional strategies of pH adjusting or calcination. To promote the hydrolysis of urea for the formation of Bi4O5I2 nanosheets, the type of solvents and urea concentration were the distinctive roles. Especially, urea concentration over 1.0 g but less than 3.0 g in the solvent of ethylene glycol could boost the formation of Bi4O5I2 nanosheets. Furthermore, the resulted Bi4O5I2 nanosheets possessing more negative conductive band level of −1.02 eV showed superior visible-light photoreduction activity of Cr (VI) due to the efficient separation of charge carriers.

Sasol isomerized paraffinic kerosene (IPK) is a coal-derived synthetic fuel under consideration as a blending stock with jet propellant 8 (JP-8) for use in military equipment. However, Sasol IPK is a low ignition quality fuel with derived cetane number (DCN) of 31. The proper use of such alternative fuels in internal combustion engines (ICEs) requires the modification in control strategies to operate engines efficiently. With computational cycle simulation coupled with surrogate fuel mechanism, the engine development process is proved to be very effective. Therefore, a methodology to formulate Sasol IPK surrogate fuels for diesel engine application using ignition quality tester (IQT) is developed. An in-house developed matlab code is used to formulate the appropriate mixture blends, also known as surrogate fuel. And aspen hysys is used to emulate the distillation curve of the surrogate fuels. The properties of the surrogate fuels are compared to those of the target Sasol IPK fuel. The DCNs of surrogate fuels are measured in the IQT and compared with the target Sasol IPK fuel at the standard condition. Furthermore, the ignition delay, combustion gas pressure, and rate of heat release (RHR) of Sasol IPK and its formulated surrogate fuels are analyzed and compared at five different charge temperatures. In addition, the apparent activation energies derived from chemical ignition delay of the surrogate fuel and Sasol IPK are determined and compared.

The critical problem facing catalysts for the LT-ESR is deactivation owing to sintering of the active metal and carbon deposition. To solve this problem, a dragon fruit-like Pt-Cu@mSiO2 catalyst for LT-ESR reaction has been successfully fabricated by a facile encapsulation strategy. Structural and morphological analysis shows that the Pt-Cu@mSiO2 nanocomposite (approximately 400 nm) has a uniform dragon fruit-like structure, with well crystallized Pt-Cu alloy nanoparticles (about 50 nm) embedded in the mSiO2. Benefiting from the unique components and architectural features, the dragon fruit-like Pt-Cu@mSiO2 nanocomposite with optimal Pt/Cu ratio present superior performance than that of Pt@mSiO2, Cu@mSiO2 and supported Pt-Cu/mSiO2 catalysts in terms of activity, H2 selectivity, and stability in the LT-ESR reaction. Moreover, the synergistic effect of platinum and copper can substantially decrease the CO concentration. It is crucial that the mesoporous SiO2 shell not only make the embedded Pt-Cu alloy nanoparticles easily accessible but also effectively prevent leaching and aggregation of active sites as well as spatially suppress the carbon deposition on the active surface, thus maintain a good catalytic activity during the 150 h stability test at 400 °C.

Experimental Validation: At the test conditions analyzed, the two-component S2 surrogate fairly reproduced the following characteristics of the target JP-8: -Ignition delays -Pressure, RHR, mass-averaged gas temperature -Engine-out emissions (CO, HC, NOX), with an exception of the absolute PM values. 3D CFD Simulation: -The simulation results were in fairly good agreement with the experimental data for the surrogate. The two-component S2 surrogate could be a reasonable choice for its use in further investigations on the target JP-8.

Surrogates for JP­8 have been developed in the high temperature gas phase environment of gas turbines. In diesel engines, the fuel is introduced in the liquid phase where volatility plays a major role in the formation of the combustible mixture and autoignition reactions that occur at relatively lower temperatures. In this paper, the role of volatility on the combustion of JP­8 and five different surrogate fuels was investigated in the constant volume combustion chamber of the Ignition Quality Tester (IQT). IQT is used to determine the derived cetane number (DCN) of diesel engine fuels according to ASTM D6890. The surrogate fuels were formulated such that their DCNs matched that of JP­8, but with different volatilities. Tests were conducted to investigate the effect of volatility on the autoignition and combustion characteristics of the surrogates using a detailed analysis of the rate of heat release immediately after the start of injection. In addition, the effect of volatility on the spray dynamics was investigated by Schlieren imaging in an optically accessible rapid compression machine (RCM). The images supported the conclusions made in the IQT tests. Furthermore, apparent activation energies of JP­8 and surrogate fuels were determined based on the chemical delay periods, which could be considered as a new parameter for developing surrogate fuel. Sector: Automotive

This paper presents an approach to develop Sasol IPK (Iso-Paraffinic Kerosene) surrogate fuels for diesel engine application using Ignition Quality Tester (IQT). The methodology includes: 1) in-house developed MATLAB code to formulate the appropriate mixture blends, 2) Aspen HYSYS to develop the distillation curve and compares it to the target Sasol IPK fuel, 3) IQT to measure the derived cetane number (DCN) of surrogate fuels and compare it with the target Sasol IPK fuel, 4) analysis of autoignition and combustion characteristics for Sasol IPK surrogate fuels. The ignition delay, combustion gas pressure, and rate of heat release of Sasol IPK and its formulated surrogate fuel are analyzed and compared at five different charge temperatures. Furthermore, the apparent activation energies derived from chemical ignition delay of the surrogate fuel and Sasol IPK are determined and compared.

Sasol isomerized paraffinic kerosene (IPK) is a coal-derived synthetic fuel under consideration as a blending stock with JP-8 for use in military ground vehicles. Since Sasol IPK is a low ignition quality fuel with derived cetane number (DCN) of 31, there is a need to improve its ignition quality. This paper investigates the effect of adding different amounts of Lubrizol 8090 cetane improver to Sasol IPK on increasing its DCN. The experimental investigation was conducted in a single cylinder research type diesel engine. The engine is equipped with a common rail injection system and an open engine control unit. Experiments covered different injection pressures and intake air temperatures. Analysis of test results was made to determine the effect of cetane improver percentage in the coal-derived Sasol IPK blend on auto-ignition, combustion and emissions of carbon monoxide (CO), total unburned hydrocarbon (HC), oxides of nitrogen (NOx), and particulate matter (PM). In addition, the effect of cetane improver on the apparent activation energy of the global auto-ignition reactions was determined.

Sasol IPK is a coal-derived synthetic fuel under consideration as a blending stock with JP-8 for use in military ground vehicles. Since Sasol IPK is a low ignition quality fuel with Derived Cetane Number (DCN) of 31, there is a need to improve its ignition quality. This paper investigates the effect of adding different amounts of Lubrizol 8090 cetane improver to Sasol IPK on increasing its DCN. The experimental investigation was conducted in a single-cylinder research type diesel engine. The engine is equipped with a common rail injection system and an open Engine Control Unit (ECU). Experiments covered different injection pressures and intake air temperatures. Analysis of test results was made to determine the effect of cetane improver percentage in the coal-derived Sasol IPK blend on autoignition, combustion and emissions of carbon monoxide (CO), total unburned hydrocarbon (HC), oxides of nitrogen (NOx), and particulate matter (PM). In addition, the effect of cetane improver on the apparent activation energy of the global autoignition reactions was determined.Copyright © 2014 by ASME

The auto-ignition process plays a major role in the combustion, performance, fuel economy, and emission in diesel engines. The auto-ignition quality of different fuels has been rated by its cetane number (CN) determined in the cooperative fuel research engine, according to ASTM D613. More recently, the ignition quality tester (IQT), a constant volume vessel, has been used to determine the derived cetane number (DCN) to avoid the elaborate, time consuming, and costly engine tests, according to ASTM D6890. The ignition delay (ID) period in these two standard tests and many investigations has been considered to be the time period between start of injection (SOI) and start of combustion (SOC). The ID values determined in different investigations can vary due to differences in instrumentation and definitions. This paper examines the different definitions and the parameters that effect ID period. In addition, the activation energy dependence on the ID definition is investigated. Furthermore, results of an experimental investigation in a single-cylinder research diesel engine will be presented, while the charge density is kept constant during the ID period. The global activation energy is determined and its sensitivity to the charge temperature is examined.

This paper investigates the effect of a cetane improver on the autoignition characteristics of Sasol IPK in the combustion chamber of the Ignition Quality Tester (IQT). The fuel tested was Sasol IPK with a Derived Cetane Number (DCN) of 31, treated with different percentages of Lubrizol 8090 cetane improver ranging from 0.1% to 0.4%. Tests were conducted under steady state conditions at a constant charging pressure of 21 bar. The charge air temperature before fuel injection varied from 778 to 848 K. Accordingly, all the tests were conducted under a constant charge density. The rate of heat release was calculated and analyzed in details, particularly during the autoignition period.In addition, the physical and chemical delay periods were determined by comparing the results of two tests. The first was conducted with fuel injection into air according to ASTM standards where combustion occurred. In the second test, the fuel was injected into the chamber charged with nitrogen. The physical delay is defined as the period of time from start of injection (SOI) to point of inflection (POI), and the chemical delay is defined as the period of time from POI to start of combustion (SOC). Both the physical and chemical delay periods were determined under different charge temperatures. The cetane improver was found to have an effect only on the chemical ID period. In addition, the effect of the cetane improver on the apparent activation energy of the global combustion reactions was determined. The results showed a linear drop in the apparent activation energy with the increase in the percentage of the cetane improver. Moreover, the low temperature (LT) regimes were investigated and found to be presented in base fuel, as well as cetane improver treated fuels.Copyright © 2013 by ASME

Injection rate shaping is a method used to control the instantaneous mass flow rate of the fuel during an injection event. The rate at which the fuel is delivered affects the composition of the combustible mixture and its distribution in the combustion chamber, thereby has an impact on the combustion process in the diesel engine. This paper investigates the effects of five different types of injection rate shapes on diesel engine autoignition, combustion, and engine-out emission trends using a three-dimensional computational simulation approach. For this purpose, an n-heptane fuel model is utilized. Initially, a tophat rate-shape, characterized by the constant mass flow rate of the fuel, is assumed to represent the actual injection profile of an actual engine. Then, in order to develop sufficient confidence in the simulation predictions, this assumption together with the calibrated CFD models are validated by reproducing the cylinder gas pressure, the rate of heat release, and engine-out emissions trends for two sets of engine operating conditions. Later, using all the rate shapes the investigation is conducted for one test point considering two different cases of fuel injection: Case 1 - same SOI and duration of injection (DOI), and Case 2 - same combustion phasing and DOI. The results obtained from the computational analysis show that the injection rate shape affects the autoignition, combustion, and emissions of a diesel engine. It is observed that the rate shapes, characterized by high injection rates at the beginning of the injection event, enhance the formation of negative temperature coefficient (NTC) regime. Therefore, the mole fractions of different species are determined during the NTC regime in order to examine the processes relevant to the formation of the NTC regimes for these rate shapes. Further, for the same SOI and DOI case, significant differences in the ignition delays between each rate shapes are observed. The maximum deviation of the ignition delay from the reference tophat is found to be 37%. Furthermore, the paper highlights the differences in the cylinder gas pressure, gas temperature, and rate of heat release due to different fuel delivery rates of different rate shapes. Finally, the comparison of the engine-out emissions for different rate shapes for both the cases of injection are presented and discussed in detail.

This paper investigates the effect of a cetane improver on the autoignition characteristics of Sasol IPK in the combustion chamber of the Ignition Quality Tester (IQT). The fuel tested was Sasol IPK with a Derived Cetane Number (DCN) of 31, treated with different percentages of Lubrizol 8090 cetane improver ranging from 0.1% to 0.4%. Tests were conducted under steady state conditions at a constant charging pressure of 21 bar. The charge air temperature before fuel injection varied from 778 to 848 K. Accordingly, all the tests were conducted under a constant charge density. The rate of heat release was calculated and analyzed in details, particularly during the autoignition period. In addition, the physical and chemical delay periods were determined by comparing the results of two tests. The first was conducted with fuel injection into air according to ASTM standards where combustion occurred. In the second test, the fuel was injected into the chamber charged with nitrogen. The physical delay is defined as the period of time from start of injection (SOI) to point of inflection (POI), and the chemical delay is defined as the period of time from POI to start of combustion (SOC). Both the physical and chemical delay periods were determined under different charge temperatures. The cetane improver was found to have an effect only on the chemical ID period. In addition, the effect of the cetane improver on the apparent activation energy of the global combustion reactions was determined. The results showed a linear drop in the apparent activation energy with the increase in the percentage of the cetane improver. Moreover, the low temperature (LT) regimes were investigated and found to be presented in base fuel, as well as cetane improver treated fuels.

This paper investigates the physical and chemical ignition delay (ID) periods in the constant volume combustion chamber of the Ignition Quality Tester (IQT). IQT was used to determine the derived cetane number (DCN) according to ASTM D6890-10a standards. The fuels tested were ultra low sulfur diesel (ULSD), jet propellant-8 (JP-8), and two synthetic fuels of Sasol IPK and F-T SPK (S-8). A comparison was made between the DCN and cetane number (CN) determined according to ASTM-D613 standards. Tests were conducted under steady state conditions at a constant pressure of 21 bars and various air temperatures ranging from 778 K to 848 K. The rate of heat release (RHR) was calculated from the measured pressure trace, and a detailed analysis of the RHR trace was made particularly for the auto-ignition process. Tests were conducted to determine the physical and chemical delay periods by comparing results obtained from two tests. In the first test, the fuel was injected into air according to ASTM standards. In the second test, the fuel was injected into nitrogen. The point at which the two resultant pressure traces separated was considered to be the end of the physical delay period. The effects of the charge temperature on the total ID as defined in ASTM D6890-10a standards, as well as on the physical and chemical delays, were determined. It was noticed that the physical delay represented a significant part of the total ID over all the air temperatures covered in this investigation. Arrhenius plots were developed to determine the apparent activation energy for each fuel using different IDs. The first was based on the total ID measured according to ASTM standards. The second was the chemical delay determined in this investigation. The activation energy calculated from the total ID showed higher values for lower CN fuels except Sasol IPK. The activation energy calculated from the chemical delay period showed consistency in the increase of the activation energy with the drop in CN including Sasol IPK. The difference between the two findings could be explained by examining the sensitivity of the physical delay period of different fuels to the change in air temperature.

This paper investigates the effect of air inlet temperature on the auto-ignition of fuels that have different CN and volatility in a single cylinder diesel engine. The inlet air temperature is varied over a range of 30°C to 110°C. The fuels used are ultra-low-sulfur-diesel (ULSD), JP-8 (two blends with CN 44.1 & 31) and F-T SPK. Detailed analysis is made of the rate of heat release during the ignition delay period, to determine the effect of fuel volatility and CN on the auto-ignition process. A STAR-CD CFD model is applied to simulate the spray behavior and gain more insight into the processes that immediately follow the fuel injection including evaporation, start of exothermic reactions and the early stages of combustion. The mole fractions of different species are determined during the ignition delay period and their contribution in the auto-ignition process is examined. Arrhenius plots are developed to calculate the global activation energy for the auto-ignition reactions of these fuels. Correlations are developed for the ID and the mean air temperature and pressure.Copyright © 2011 by ASME