Bradford A. Bruno

Fuel Injection Pressure Effects on the Cold Start Performance of a GDI Engine

The effects of reduced fuel injection pressure on the cold start performance of a GDI engine have been studied in a single-cylinder, optically-accessible research engine. Two Delphi Automotive Systems DI-G injectors, with included spray cone angles of 60° and 80° respectively, were studied. Both injectors are designed to operate at a nominal fuel line pressure of 10 MPa. For the study they were operated at several fuel feed pressures between 10 MPa and 2 MPa. Two start of injection timings (50° and 100° ATDC) were examined. Cold start performance was characterized by measurements of the GIMEP, COV of GIMEP, and total engine out UHCs. Simultaneous Planar Laser Induced Fluorescence (PLIF) and Mie Scattering images of the fuel spray were used to observe spray penetration, mixing, and in-cylinder fuel distribution throughout the intake and compression strokes. Ultimately these images were used to explain observed performance differences. Significant cold start performance changes are not observed until the injection pressure is reduced to below 5 MPa. The PLIF imaging shows that piston crown wetting and cylinder wall wetting have a dominant effect on engine cold start performance. This suggests that spray penetration and trajectory are at least as important to engine cold start performance as mean drop size. This indicates the desirability of developing an injector technology which can decouple injection pressure, drop size, and spray penetration.

Using Objective-Driven Heat Transfer Lab Experiences to Simultaneously Teach Critical Thinking Skills and Technical Content

The heat transfer course at Union College has been redesigned to improve critical thinking and problem solving skills, provide an understanding of the origin of the data and parameters used in heat transfer analysis, and familiarize students with modern experimental and computer analysis tools. The course is taught in the junior year and combines a 4-hr/wk lecture with a 3-hr/wk integrated lab component during a 10 week term. The lecture covers the traditional conduction, convection and radiation heat transfer material whereas in the lab students combine hands on experimental measurements with the use of sophisticated design tools. Our method for achieving the course goals is to use objective-driven lab exercises. Students are asked directed questions about a concrete problem involving heat transfer and are required to develop an experimental/numerical plan to answer the questions. Initial labs are more directed and are designed to introduce experimental / numerical analysis techniques which students may then use in the end of term design project which is more open ended. We have focused on the use of small scale inexpensive equipment which allows us to use multiple set-ups and have students work in small (2-3 person) groups. In this paper we present the weekly lab exercises and discuss how they contribute to the pedagogical goals for the lab, course, and curriculum.Copyright

A Preliminary PIV and Analytical Investigation of Wall Shear in Micro Channel Slug Flow

This paper describes the methods and initial results of an investigation aimed at answering questions of engineering significance pertaining to slug flow. The authors use two approaches to study slug flow. First, the analytical solution of Gaskell et al and Gurcan [5,6] is examined in detail, with special attention being paid to its predictions pertaining to the special case of slug flow. The numerical behavior of this solution and the measures needed to enhance its convergence are also commented upon. Second, micro-PIV data of water/oil slug flow in a micro-channel is reported and examined in light of the predictions of the Gaskell model. Quantitative results showing the details of the re-circulating internal flow fields in the slugs are presented. Results for wall shear stress distributions and evolution of the velocity profiles from the centerline to the rear interface are also presented. Significant increases in the wall shear stress (compared to a fully developed Poiseuille flow) are observed in the regions near the fluid interfaces.Copyright

Shear Stress Measurement in Microfluidic Systems: Liquid Crystal Technique

Preliminary work towards developing a liquid crystal based technique for direct shear stress measurements over solid surfaces in microfluidic systems is presented. The microfluidic slug flow study which motivated the development of this technique is presented, as is general background on microfluidics. The theory of shear sensitive liquid crystals is reviewed and then expanded upon in regards to the specific type of flow considered in this study; slug flow. A prototype apparatus is described which is capable of generating slugs, and has appropriate optical access to test the liquid crystal shear stress measurement technique. The microchannel (150μm × 250μm laser etched glass), auxiliary flow (Cole-Parmer Infusion 100 Syringe Pump), and optical data collection (Olympus BX51 microscope) subsystems are all described in detail. Procedures for applying the cholesteric liquid crystal mixtures obtained through Pressure Chemicals Ltd. to the microchannel and for collecting liquid crystal data are described as well. Finally, preliminary results are presented, the current status of the technique is stated along with proposed directions for future research work.Copyright

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (<6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Preparation and characterization of copper-containing alumina and silica aerogels for catalytic applications

Catalytic, copper-impregnated alumina and silica aerogels were prepared. Alumina gels were prepared from a solution of aluminum chloride via an epoxide-assisted synthesis. Silica gels were fabricated from tetramethyl orthosilicate using a base-catalyzed approach to the hydrolysis and polycondensation reactions. Copper was introduced into the alumina and silica gels through exposure of the wet gel to a solution of copper(II) nitrate during a solvent-exchange step prior to aerogel formation via rapid supercritical extraction. Undoped silica and alumina aerogels were fabricated for comparison. A barrage of physical characterization methods were employed to analyze the aerogels as-prepared, following heat-treatment and following catalytic testing. These include bulk density, Brunauer-Emmett-Teller surface area, Barrett-Joyner-Halenda pore distribution, infrared spectroscopy, X-ray diffraction, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. As-prepared copper-silica aerogels have density 0.11 g/cm3, surface area 780 m2/g, and 9-nm average pore diameter. As-prepared copper-alumina aerogels have density 0.09–0.11 g/cm3, surface area 430 m2/g, and 23-nm average pore diameter. Calcining to 800 °C results in 10% lower surface area and average pore size 22 nm for copper-silica aerogels, 70% lower surface area for copper–alumina aerogels and, in both types of materials, yields microcrystalline CuO. A catalytic testbed was employed to assess the suitability of the copper–alumina and copper–silica aerogels as three-way catalysts for eventual application in automotive pollution mitigation. Both copper–silica and copper–alumina aerogels performed as three-way catalysts.Graphical Abstract