Attention from the media and general public has recently soared with regard to forensic chemistry. This rising awareness can be attributed to television shows such as CSI and Forensic Files that have made chemical analysis exciting. By utilizing a forensic-based experiment in an instrumental methods course, student interest in the laboratory can be stimulated. In addition, students will gain valuable experience with an analytical technique(s) that is used in real situations by forensic laboratories.The oldest method of personal identification for forensic purposes is latent fingerprint analysis. The ability to identify suspects from fingerprints left at a crime scene is a result of the arrangement of ridges on the finger pads being unique and permanent to each person (1). Recently, with advances in modern technology, scientists have begun to examine whether information in addition to ridge patterns can be gained from fingerprints. For example, researchers have discovered that they can obtain a suspect's DNA profile by applying the polymerase chain reaction to skin debris present in fingerprints left on forensic evidence (2, 3). In parallel to this advancement, progress has been made in determining the chemical composition of a latent fingerprint using infrared (IR) microspectroscopy and gas chromatography-mass spectrometry (GC-MS) (4-8).Fingerprints primarily consist of material secreted by the eccrine glands located in the palms and fingertips and the sebaceous glands that are located most abundantly on the scalp and face (6). These chemical components include inorganic salts such as iron and sodium, amino acids, and lipids such as fatty acids, wax esters, squalene, and cholesterol (9). IR (7,8) and GC-MS (4-6) studies have examined whether differences in the chemical composition of fingerprints can be used to establish age, gender, and so forth. This information could allow a suspect pool to be reduced even if the fingerprints obtained from a crime scene were smudged or patterns were not matched after being processed in the Integrated Automated Fingerprint Identification System (10).We have adapted a procedure described by Asano et al. (5) and Archer et al. (4) for fingerprint extraction and analysis by GC-MS for use in an undergraduate instrumental analysis course. In the experiment, students collect fingerprint residue samples on glass beads or glass slides, extract the chemical constituents from the residue using chloroform, convert the fatty acids and other components into trimethylsilyl derivatives, and finally, analyze the products using GC-MS. By converting the constituents into less polar, thermally stable materials through silylation, students gain experience in a technique that is frequently required to make samples amenable to GC analysis (11). Furthermore, students can perform a MS library search to identify the components present in their fingerprint residue and then compare their results to demonstrate that more information than just ridge pattern might be obtained from fingerprints found at crime...

Torque converters are key components in automatic and hydrodynamic transmissions. Power is transmitted through the reaction force of fluid on cascades; thus, the geometry of the blade is essential to torque converter performance. The traditional one-dimensional blade design approach becomes inefficient for modern torque converter design because torque converters are highly coupled turbomachines and the flow is three-dimensional. In the present research, a novel six-parameter blade camberline design was developed to describe the overall shape of the blade. A full two-level factorial design was conducted with computational fluid dynamics (CFD) simulations on each component to determine the sensitivity of design variables and investigate the relationship between design parameters and hydrodynamic performance. The design variables were reduced from 18 to nine after the screening design. A quarter-fractional factorial design was performed on the selected primary design variables to explore the first-order interaction effects between different wheels. Then a response surface was generated for each component to provide a substitution model for further optimization. A series of torque converters with various design parameters were fabricated and tested to validate the important effects determined in the design of experiments (DOE) process. It is found that CFD in combination with DOE is able to precisely capture the correlation between design variables and hydrodynamic performance. A base torque converter was optimized based on the DOE studies and the result was tested. Pronounced improvement in powertrain performance and fuel economy were observed.

Full three-dimensional (3D) computational fluid dynamics (CFD) simulations are carried out using ANSYS cfx to obtain the detailed flow field and to estimate the rotordynamic coefficients of a labyrinth seal for various inlet swirl ratios. Flow fields in the labyrinth seal with the eccentricity of the rotor are observed in detail and the detailed mechanisms that increase the destabilizing forces at high inlet swirl ratios are discussed based on the fluid governing equations associated with the flow fields. By evaluating the contributions from each term of the governing equation to cross-coupled force, it is found that circumferential velocity and circumferential distribution of axial mass flow rate play key roles in generating cross-coupled forces. In the case that circumferential velocity is high and decreases along the axial direction, all contributions from each term are positive cross-coupled force. On the other hand, in the case that circumferential velocity is low and increases along the axial direction, one contribution is positive but the other is negative. Therefore, cross-coupled force can be negative in the local chamber depending on the balance even if circumferential velocity is positive. CFD predictions of cross-coupled stiffness coefficients and direct damping coefficients show better agreement with experimental results than a bulk flow model does by considering the force on the rotor in the inlet region. Cross-coupled stiffness coefficients derived from the force on the rotor in the seal section agree well with those of the bulk flow model.

Grove configuration has a direct influence on the performance of the labyrinth seal. In this study, the geometry of the groove cavities in a water balance drum labyrinth seal was varied to investigate the effects on fluid leakage. A design of experiments (DOEs) study varied the groove cavity cross section through various trapezoidal shapes with one or both internal base angles obtuse. The grooves are parameterized by the groove width connected to the jet-flow region, the internal entrance and exit angles, the flat width inside the groove, and the depth. The corners inside the groove cavity are filleted with equal radii. As with the baseline model, the grooves are evenly spaced along the seal length and identical copies of each other. The flow path starting at the rear of the pump impeller and proceeding through the seal was created as a 5-deg sector computational fluid dynamics (CFD) model in ansys cfx. Three five-level factorial designs were selected for the cases where the entrance angle is obtuse and the exit angle is acute, the exit angle obtuse and entrance angle acute, and both angles were obtuse. The feasible geometries from each factorial design were selected based on the nonlinear geometric constraints, and CFD simulation experiments were performed in ansys cfx. The leakage results from these simulation experiments were then analyzed by multifactor linear regression to create prediction equations relating the geometric design variables to leakage and enable geometric optimization for minimum leakage. Streamline plots along the seal cross section were then used to visualize the flow and understand regression trends. This study investigates the effect of groove cavities with obtuse internal entrance and exit angles on vortex size and position and subsequent seal leakage.

Annular labyrinth seals often have a destabilizing effect on pump rotordynamics due to the large cross-coupled forces generated when the fluid is squeezed by an oscillating rotor. In this study, several novel groove geometries are investigated for their effect on the rotordynamic coefficients of the labyrinth seal. The groove cavity geometry of a baseline 267 mm balance drum labyrinth seal with a clearance of 0.305 mm and 20 equally spaced groove cavities was optimized for minimum leakage. From the pool of possible groove designs analyzed, nine test cases were selected for maximum or minimum leakage and for a variety of groove cavity shapes. The rotordynamic coefficients were calculated for these cases using a hybrid computational fluid dynamics (CFD) bulk-flow method. The rotordynamic coefficients obtained by this method were then used with a rotordynamic model of the entire pump to determine the overall stability. Results show that labyrinth seal’s groove shape can be optimized to generate lower leakage rates, while the effects on dynamic properties are only minimally changed. If the seal dynamic response needs to be modified in addition to targeting a lower leakage rate, for instance, to exhibit increased damping values, then the leakage rate and the damping coefficient need to be set as objective functions in the optimization loop.