Ignition and combustion development for high speed direct injection diesel engines under low temperature cold start conditions

Diesel engine cold start is an important issue for current technology at low (below 0 °C) temperatures and for future applications. The aim of this work is to develop a description of how, when and where does fuel spray ignition occur in a glow-plug assisted engine under simulated low temperature cold start conditions. In-cylinder pressure analysis is combined with high speed visualization in an optical engine. A pilot plus main injection strategy is used. Visualization results show that pilot ignition occurs in the vicinity of the glow plug, and strongly influences main combustion initiation. Main combustion starts from the pilot flame, and propagates to the rest of the combustion chamber showing a strong visible reaction zone. After end of main injection, the rapid leaning of the mixture suppresses the strong radiation, and OH radiation is observed to progress to the rest of the combustion chamber. The combustion process shows a strong scattering, which has been quantified by combustion parameters. At higher rail pressures scattering increases, which eventually inhibits combustion initiation. However, if ignition occurs at higher rail pressures, cycle performance is better.Authors thank the Spanish Ministry of Innovation and Science for the financial support through the project OPTICOMB (reference code: TRA2007-67961-C03-C01). Authors also thank Daniel Lerida Sanchez de las Heras for his outstanding work in the facility set-up and adaptation and for his support during the tests.Pastor Soriano, JV.; García Oliver, JM.; Pastor Enguídanos, JM.; Ramírez Hernández, JG. (2011). Ignition and combustion development for high speed direct injection diesel engines under low temperature cold start conditions. Fuel. 90(4):1556-1566. https://doi.org/10.1016/j.fuel.2011.01.008S1556156690

Partial Regularity of solutions to the Four-dimensional Navier-Stokes equations at the first blow-up time

The solutions of incompressible Navier-Stokes equations in four spatial dimensions are considered. We prove that the two-dimensional Hausdorff measure of the set of singular points at the first blow-up time is equal to zero.Comment: 19 pages, a comment regarding five or higher dimensional case is added in Remark 1.3. accepted by Comm. Math. Phy

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

On the steady transport equation

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