Optical Studies of Spray Development in a Quiescent Chamber and in a Direct-Injection Spark-Ignition Engine

The effects of fuel type and in-cylinder flow on spray formation from a multi-hole injector were studied by high-speed imaging techniques in a quiescent injection chamber and in a single-cylinder Direct-Injection Spark-Ignition (DISI) engine. To examine the effect of fuel volatility on spray formation, the injector was heated from 20 °C to 120 °C in the chamber for iso-octane and gasoline. The injection chamber was operated at 0.5 and 1.0 bar to mimic in-cylinder pressures for early injection strategies. Droplet sizing was also employed in the chamber using Phase Doppler Anemometry (PDA). Fuel-type and temperature effects were studied in-cylinder by operating the engine at 20 °C and 90 °C head temperature at 1500 RPM. For both sets of experiments, the study was carried out for two orthogonal views, relating to the tumble and swirl planes of in-cylinder flow motion. Spray formation was observed to be different for the two fuels, especially at high injector temperatures. Wetted footprint spray areas were calculated for both experimental setups. © IMechE 2007

Cavitation, primary break-up and flash boiling of gasoline, iso-octane and n-pentane with a real-size optical direct-injection nozzle

Improvements to the direct-injection spark-ignition combustion system are necessary if the potential reductions in fuel consumption and emissions are to be fully realized in the near future. One critical link in the optimization process is the design and performance of the injectors used for fuel atomization. Multi-hole injectors have become the state-of-the-art choice for gasoline direct-injection engines due to their flexibility in fuel targeting by selection of the number and angle of the nozzle holes, as well as due to their demonstrated stability of performance under a wide range of operating conditions. Recently there has been increased attention devoted to the study of the flow through the internal passages of injectors because of the presence of particular fluid phenomena, such as large-scale vortical motion and cavitation patterns, which have been shown to influence the characteristics of primary break-up. Understanding how cavitation can be used to improve spray atomisation is essential for optimizing mixture preparation quality under early injection and stratified engine operating conditions but currently no data exist for injector-body temperatures representative of real engine operation, particularly at low-load conditions that can also lead to phase change due to fuel flash boiling. This paper outlines results from an experimental imaging investigation into the effects of fuel properties, temperature and pressure conditions on the extent of cavitation, flash boiling and, subsequently, primary break-up. This was achieved by the use of a real-size transparent nozzle of a gasoline injector from a modern direct-injection combustion system. Gasoline, iso-octane and n-pentane fuels were used at 20 and 90 °C injector-body temperatures for ambient pressures of 0.5 and 1.0 bar in order to simulate early homogeneous injection strategies for part-load and wide-open-throttle engine operation. © 2010 Elsevier Ltd. All rights reserved

Prevalence and Severity of Diabetic Retinopathy in Patients with Macular Telangiectasia Type 2

PURPOSE: To study the prevalence and severity of diabetic retinopathy (DR) in patients with macular telangiectasia type 2 (MacTel 2). DESIGN: Retrospective case series. PARTICIPANTS: Patients with a diagnosis of MacTel 2 treated at the Rotterdam Eye Hospital or Erasmus Medical Center between 2014 and 2018 were included. METHODS: The following information was retrieved from patient files: demographics, history of diabetes mellitus and hypertension, presence of DR, and severity of DR, that is, mild, moderate, severe, or proliferative. Presence of diabetic macular edema (DME) was assessed using OCT. MAIN OUTCOME MEASURES: Presence and severity of DR. RESULTS: Two hundred six eyes of 103 patients were included. At the onset of MacTel 2, the mean age was 61 years (standard deviation [SD], 9.8 years) and 64 (62%) were women. Mean follow-up was 71 months (SD, 60 months). Diabetes mellitus type 2 was present in 50 patients (49%) and hypertension was present in 47 patients (46%). Mild DR was present in 22 eyes (11%), of which 14 eyes (7%) showed signs at baseline and 8 eyes (4%) showed signs at a later time during follow-up. Ten eyes (5%) demonstrated remission of mild DR during follow-up. Both eyes (1%) in 1 patient progressed to moderate DR. Severe DR, proliferative DR, and DME did not occur. CONCLUSIONS: Although diabetes mellitus was highly prevalent among MacTel 2 patients, no patients showed severe or proliferative DR or DME. These findings suggest that MacTel 2 could have a protective effect on the progression of DR. We hypothesize that our results may be explained by the role of Müller cells in the development of MacTel 2 and DR, and therefore a link between both diseases warrants additional studies

Impingement characteristics of an early injection gasoline direct injection engine: A numerical study

This paper describes the use of a Lagrangian discrete droplet model to evaluate the liquid fuel impingement characteristics on the internal surfaces of an early injection gasoline direct injection (GDI) engine. The study focuses on fuel impingement on the intake valve and cylinder liner between start of injection (SOI) and 20° after SOI using both a single- and multi-component fuel. The single-component fuel used was iso-octane and the multi-component fuel contained fractions of iso-pentane, iso-octane and n-decane to represent the light, medium and heavy fuel fractions of gasoline, respectively. A detailed description of the impingement and liquid film modelling approach is also provided Fuel properties, wall surface temperature and droplet Weber number and Laplace number were used to quantify the impingement regime for different fuel fractions and correlated well with the predicted onset of liquid film formation. Evidence of film stripping was seen from the liquid film formed on the side of the intake valve head with subsequent ejected droplets being a likely source of unburned hydrocarbons and particulate matter emissions. Differences in impingement location and subsequent location of liquid film formation were also observed between single- and multi-component fuels. A qualitative comparison with experimental cylinder liner impingement data showed the model to well predict the timing and positioning of the liner fuel impingement