Evaluation Of Nozzle Geometry On High Pressure Gasoline Direct Injection Spray Atomization

This research presents a critical study of injector nozzle geometry on high-pressure Gasoline Direct Injection, GDi, injector spray morphology. The study was conducted with the aid of multi-fluid Volume-of-Fluid, Large-Eddy-Simulation, VOF-LES, method. Alternative nozzle geometries, that are the subject of current interest including varying nozzle hole length to diameter ratio, counter-bore presence and nozzle-hole skew-angle geometry, are studied in detail in order to provide insight into their specific influence on spray plume targeting and jet primary breakup characteristics. A comparison of the simulation results with near-field shadowgraph and Mie scatter imaging as well as phase-contrast x-ray imaging is provided. When near-field experimental imaging validated the simulation results further investigation of the fundamental flow mechanism internal to the injector was studied using VOF-LES to gain insight to the cause of spray morphology changes within the injector valve group. The complementary analysis of Computational Fluid Dynamics method and empirical data supported definitive conclusions on nozzle design parameter effects for l/d, skew angle, counterbore for varying injection pressure as well as provided an understanding of the underlying physical mechanisms involved to engender the resulting spray plume characteristics

Inguinal hernia – epidemiology, risk factors, treatment methods (literature review)

Inguinal hernias (IH) are widespread in the human population and occur in 27–43 % of men and 3–6 % of women. Many risk factors for IH have been overestimated in the last decade: male gender is considered the leading factor (the ratio between men and women is approximately 1:7), less significant factors are heredity (most significant for women), physical activity (more significant for men), age (peak prevalence of IH occurs at 5 years and 70–80 years), congenital or acquired connective tissue dysplasia, history of prostatectomy, low body mass index.Hernioplasty with the use of synthetic mesh prostheses remains the most popular technique for surgical correction of IH. Performing non-prosthetic hernioplasty is only recommended if mesh prostheses are not available, for example in poor countries. In open hernioplasty using mesh prostheses, different methods are used today: Plug & Patch, Prolene Hernia System, Parietene Progrip, sutureless plastic according to Trabucco, Stoppa, preperitoneal techniques TIPP (trans-inguinal pre-peritoneal), TREPP (transrectus pre-peritoneal), TEP (total extraperitoneal), however, none of them showed significant advantages over the gold standard of open hernioplasty – tensionfree repair according to Liechtenstein.Laparoscopic IH correction is represented by the TAPP (transabdominal preperitoneal) technique, performed through the abdominal cavity, and TEP (total extraperitoneal) – extraperitoneal prosthetic hernioplasty. None of them has a significant advantage in the treatment of IH; therefore, when choosing a treatment method, the surgeon should be guided by the cost of the operation and the level of proficiency in one or another hernioplasty technique

Tetrachloroethylene (PCE, Perc) Levels in Residential Dry Cleaner Buildings in Diverse Communities in New York City

Fugitive tetrachloroethylene (PCE, perc) emissions from dry cleaners operating in apartment buildings can contaminate residential indoor air. In 1997, New York State and New York City adopted regulations to reduce and contain perc emissions from dry cleaners located in residential and other buildings. As part of a New York State Department of Health (NYSDOH) study, indoor air perc levels were determined in 65 apartments located in 24 buildings in New York City where dry cleaners used perc on site. Sampling occurred during 2001–2003, and sampled buildings were dispersed across minority and nonminority as well as low-income and higher income neighborhoods. For the entire study area, the mean apartment perc level was 34 μg/m(3), 10-fold lower than mean apartment levels of 340–360 μg/m(3) documented before 1997. The maximum detected perc level was 5,000 μg/m(3), 5-fold lower than the maximum of 25,000 μg/m(3) documented before 1997. Despite these accomplishments, perc levels in 17 sampled apartments still exceeded the NYSDOH residential air guideline of 100 μg/m(3), and perc levels in 4 sampled apartments exceeded 1,000 μg/m(3). Moreover, mean indoor air perc levels in minority neighborhoods (75 μg/m(3)) were four times higher than in nonminority households (19 μg/m(3)) and were > 10 times higher in low-income neighborhoods (256 μg/m(3)) than in higher income neighborhoods (23 μg/m(3)). Logistic regression suitable for clustered data (apartments within buildings) indicated that perc levels on floors 1–4 were significantly more likely to exceed 100 μg/m(3) in buildings located in minority neighborhoods (odds ratio = 6.7; 95% confidence interval, 1.5–30.5) than in nonminority neighborhoods. Factors that may be contributing to the elevated perc levels detected, especially in minority and low-income neighborhoods, are being explored

Regeneration of Cu/SAPO-34(MO) with H2O only: Too good to be true?

The performance failure of Cu/SAPO-34 material used as an NH3-SCR catalyst at low temperature in the presence of water has caused a gradual withdrawal of its usage from the market. There is an urgent need to clearly understand its deactivation mechanism and to find a way to regenerate the Cu/SAPO-34 catalyst material. Interestingly and surprisingly, we have discovered that, under certain conditions, 10% H2O can regenerate a previously deactivated Cu/SAPO-34(MO), as long as its zeolite structure is maintained. By using experimental observations of NH3-SCR reaction, solid state NMR, NO-DRIFTS, and in situ H2-TPR, a mechanism is proposed which can explain both the deactivation and regeneration of Cu/SAPO-34(MO). We propose that the transformation of Si(4OAl) and Si(3OAl) to (2Al)Si(2OH) and (3Al)Si(OH) and the Si condensation in the pores of the framework, which result from H2O exposure, are responsible for the deactivation of Cu/SAPO-34(MO). We suggest that the formation of condensed Si which results in Si clusters, hinders the mobility of the linear complex, [Cu-(NH3)2]+, which is the active species during the low temperature NH3-SCR reaction. Moreover, we propose a regeneration mechanism when Cu/SAPO-34(MO) is exposed to 10% H2O, where the Si clusters are transformed back to Si-O-H bonds, and thereafter transferred back to the framework. This can explain the regeneration of deactivated Cu/SAPO-34(MO)

Regeneration of water-deactivated Cu/SAPO-34(MO) with acids

The Cu/SAPO-34 catalysts, used for NH3 selective catalytic reduction (SCR), are systemically studied with various characterization techniques before and after low temperature water deactivation and regeneration using techniques such as XRD, BET, ICP-SFMS, 27Al MAS NMR, 29Si MAS NMR, and H2-TPR. Analysis of results suggests that, during low-temperature water deactivation, hydrolysis of Si-O-Al occurs resulting in Si condensation and formation of Si clusters. It is proposed that these formed Si clusters are mainly responsible for the deactivation of Cu/SAPO-34 catalysts since they suppress the mobility of [Cu-(NH3)]+ and hinder the formation of the transient [CuI(NH3)2]+-O2-[CuI(NH3)2]+ intermediate, which is considered to be the rate-limiting step for NH3-SCR reaction. The regeneration of the deactivated Cu/SAPO-34 catalysts with acid can be explained by the ability of the acid to convert the Si clusters back to Si-O-H, which is able to revert to the SAPO-34 framework via reverse hydrolysis as the temperature increases

Understanding the mechanism of low temperature deactivation of Cu/SAPO-34 exposed to various amounts of water vapor in the NH3-SCR reaction

The low temperature hydrothermal stability of Cu/SAPO-34 catalysts for the NH3-SCR reaction, prepared by three different structure directing agents (SDAs), i.e., morpholine (MO), triethylamine (TEA), and tetraethylammonium hydroxide (TEAOH), was investigated by exposing them to various amounts of water vapor. XRD and BET studies indicate that there was no sign of Cu/SAPO-34 catalyst\u27s chabazite (CHA) structural collapse due to water vapor exposure up to 55 h regardless of SDA choice. However, a multinuclear solid-state magic angle spinning (SS-MAS) NMR study of Cu/SAPO-34(MO, TEA, TEAOH) suggests that the water vapor exposure had significantly altered the coordination environment of Al, P, and Si, the extent of which depends on the choice of SDA along with water vapor exposure time. NO-DRIFTS and H-2-TPR studies suggest different mobility for Cu ions between the 6MR and 8MR of the CHA structure in Cu/SAPO-34(MO, TEA, TEAOH) as the result of water vapor exposure and during the NH3-SCR reaction. The mechanisms for low temperature deactivation of Cu/SAPO-34 were proposed as follows: 1) irreversible Si condensation in the support and 2) Cu migration to less accessible sites and/or formation of CuOx clusters depending on Cu mobility

Effect of various structure directing agents (SDAs) on low-temperature deactivation of Cu/SAPO-34 during NH3-SCR reaction

Cu/SAPO-34 and Cu/SSZ-13 having chabazite structure (CHA) have attracted significant attention because of their high activity and N2selectivity during SCR reaction as well as superior resistance to hydrocarbon poisoning. Cu/SAPO-34 has shown better hydrothermal durability than Cu/SSZ-13 at high temperature. However, we have observed earlier that Cu/SAPO-34 prepared using morpholine as a structure directing agent (SDA) deteriorated under water exposure at low temperature, where the NOxconversion activity decreased from 87% to 6% after 9 h of low temperature exposure. In this study, Cu/SAPO-34 catalysts prepared using three different SDAs, i.e., morpholine (MO), triethylamine (TEA), and tetraethylammonium hydroxide (TEAOH), were prepared by the incipient wetness impregnation (IWI) method. A commercially purchased SAPO-34 (SAPO-34(ACS)) was also used for comparison purposes. After low temperature water deactivation, Cu/SAPO-34(TEA) and (TEAOH) mostly recovered their activities while Cu/SAPO-34(MO) and (ACS) only regained part of their activities after regeneration tests under a series of experimental conditions for the NH3-SCR reaction. Solid-state MAS NMR was employed to study the impact of SDAs on the coordination of Al, P, and Si in the SAPO-34 supports and Cu/SAPO-34 catalysts. CO-DRIFTS, NO-DRIFTS, and H2-TPR employed in this study collectively propose the presence of two different Cu locations in Cu/SAPO-34(MO, TEA, TEAOH, and ACS). It is suggested that the concentrations of Cu in two distinct locations within Cu/SAPO-34 catalysts characterized by CO-DRIFTS, NO-DRIFTS, and H2-TPR studies are significantly influenced by the choice of SDA, which will be important for understanding the deactivation mechanism of Cu/SAPO-34 catalysts during low temperature NH3-SCR reaction

Impact of Different Synthesis Methods on the Low-Temperature Deactivation of Cu/SAPO-34 for NH3-SCR Reaction

SAPO-34 were synthesized using three structure-directing agents (SDAs), i.e., tetraethylammonium hydroxide (TEAOH), triethylamine (TEA), and morpholine (MO). These SAPO-34 supports were used to prepare Cu/SAPO-34 catalysts via two different Cu-exchange methods: incipient wetness impregnation (IWI) and solid-state ion exchange (SSIE). The catalytic performance of Cu/SAPO-34(TEAOH, TEA, MO) catalysts prepared with IWI and SSIE before and after exposure to water vapor at 70\ua0\ub0C was systemically examined, and their deactivation behavior during low-temperature NH3-SCR reaction was studied. These catalysts were characterized by XRD, BET, ICP-SFMS, SEM/EDX, solid-state NMR, CO-DRIFTS, NO-DRIFTS, and H2-TPR. The various characterization findings for the Cu/SAPO-34 catalysts suggest that the distribution of different Cu2+ species and the mobility of Cu2+ in chabazite (CHA) structure are important for the low-temperature deactivation and regeneration behaviors of the Cu/SAPO-34(TEAOH, TEA, MO)-IWI and -SSIE during the NH3-SCR reaction. Thus, it has been determined that the choice of SDA and Cu-exchange method is vital to design of an efficient Cu/SAPO-34 catalyst that is highly active during a NH3-SCR reaction and has a high tolerance for the low-temperature deactivation caused by exposure to water vapor

Ammonia sensor for closed-loop SCR control

Selective Catalytic Reduction (SCR) is the dominant solution for meeting future NOx reduction regulations for heavy-duty diesel powertrains. SCR systems benefit from closed-loop control if an appropriate exhaust gas sensor were available. An ammonia sensor has recently been developed for use as a feedback element in closed-loop control of urea dosing in a diesel SCR aftertreatment system. Closed-loop control of SCR dosing enables the SCR system to be robust against disturbances and to meet conformity of production (COP) and in-use compliance norms. The ammonia sensor is based on a non-equilibrium electrochemical principle and outputs emf signals. The sensor performs well when tested in a diesel engine exhaust environment and has minimum cross interference with CO, HC, NO, NO2, SO2, H2O and O2. Previous work, done in a simulation environment, demonstrated that an ammonia sensor provides the optimal feedback for urea dosing control algorithms in closed-loop SCR systems. A model-based SCR control strategy deploying an ammonia feedback sensor demonstrated high NOx conversion, low NH3 slip and good robustness against disturbances. In this paper, FTP, ETC and ESC test data will be presented confirming these results. NOx conversions as high as 91% are measured in combination with 30% urea injection error and a 25 ppm NH3 slip constraint. Test results using the Delphi ammonia sensor for control are compared with test results utilizing a commercially available NOx sensor for control