Browse Topic: Windows and windshields

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Windshield with Enhanced Infrared Reflectivity Enables Packaging a Driver Monitor System in a Head-Up Display2021-01-01054/6/2021
Integration of a driver monitor system (DMS) in a head-up display (HUD) gives the monitor camera a continuous view of the driver’s face, since the driver always faces the road ahead. However, with both infrared (IR) illuminator and IR camera packaged in the HUD, reflectivity of the windshield is important at IR wavelengths used by the camera. Not only is windshield IR reflectivity important for a clear camera image of the driver’s face, but increasing windshield reflectivity also decreases the effect of ambient sunlight on the camera image of the driver’s face. We describe a method to measure windshield reflectivity, both for the 940 nm band used by a DMS, and for visible light for the HUD. The measurement method uses a fiber-optic spectrometer, two collimating lenses, and a method to compensate for sample tilt. The lenses are mounted on a stage that adjusts the height above the sample. As an example, this method was used to characterize an IR reflecting windshield, prepared for a prototype automotive HUD. At 940 nm, and 45° angle of incidence, the measured reflectivity is > 85% for unpolarized incident light. For visible light at 550 nm, and 62° angle of incidence, the measured reflectivity is 13.9% for both an IR reflecting windshield and for a reference windshield, for unpolarized incident light. The prototype windshield gives a good reflected image for the DMS IR camera and a good HUD image as seen by the driver. The method used to prepare this prototype windshield is suitable for high-volume production.
Lambert, David K., Itsede, Fidelis, Tomura, Kazuhiro, Nohara, Atsushi, Chou, Kinryo, Carty, Dylan
The Life and Mysterious Death of Harold F. Pitcairn: Was it Suicide?F-0076-2020-1626010/5/2020
Harold F. Pitcairn, American aviation and Autogiro pioneer, died from a single gunshot wound to the head in the late evening hours of April 23, 1960 at the age of 62 after a gala evening at which he presided over a celebration attended by more than 450 guests for his brother's Raymond's 75th birthday. Initially labelled a suicide by the press, Pitcairn's widow Clara declared that "she never wanted to hear another word about the tragedy", while friends and friendly local authorities made the argument, duly reported by Frank Kingston Smith in Legacy of Wings, his devotional Pitcairn biography (subsidized by the Pitcairn family), that the death was accidental because "there was no note, no indication of depression or unhappiness" and "the police investigation disclosed that two shots had been fired; one had penetrated the ceiling directly over the desk in the first floor study, another had struck Pitcairn in the eye" and that "the next morning it was discovered the semi-automatic pistol was defective: when cocked, it had a supersensitive "hair trigger," and it had a faulty disconnector so that it would fire more than one shot at a time, a condition known as "doubling."" The Pitcairn families, prominent and powerful, prevailed upon the local authorities to declare the death accidental and Kingston Smith's 1981account became the de facto authoritative story of the death of Harold F. Pitcairn. With the perspective, however, of six decades, it appears far more likely that Pitcairn's death was a suicide for reasons that were not readily evident, minimized, unappreciated or deliberately ignored at the time to craft a result that met the needs of Clara Pitcairn and her surviving family. These included the fact that while the claim was made that Pitcairn was making his nightly rounds to check on the estate’s ground-level windows (and had been doing so since the Lindbergh kidnapping in 1932), he actually died at his desk; that those in the house only reported a single shot; the 1907 Savage pistol had no reputation for a hair-trigger, and had not evidenced such a flaw in almost three decades of Pitcairn's nightly ritual; that even though Pitcairn had been assured that his almost-decade-long lawsuit against the United States government for Patent infringement of his Autogiro patents was going well, he was concerned about the impact this lawsuit was having on his aged associates who had been called to give depositions and he had voiced the sentiment that "if he had known that he would have to sue the government, he would not have gone into the Autogiro business"; that the lawsuit, itself intended as a vindication of Pitcairn's contribution to aviation was dragging on and would reach its first legal conclusion in 1967, and not finally conclude upon appeal until 1977; and most importantly, those who deny suicide and point to Pitcairn’s state-of-mind, have failed to take into account when the death occurred or ready evidence of his 'state of mind' To fail to see the tragic end of Harold F. Pitcairn is to forget that 29 years and one day earlier, he had been recognized for "the greatest achievement in aeronautics or astronautics in America, with respect to improving the performance, efficiency, and safety of air or space vehicles, the value of which has been thoroughly demonstrated by actual use during the preceding year." The memory of that day on the White House back lawn with the President was the high point of his life even as Pitcairn prepared to celebrate his older brother's achievements. The evidence, when marshalled and documented, conclusively points to suicide - a death of an American aviation pioneer before his contributions were vindicated in the largest patent infringement judgement against the United States in history. To fail to see the tragic end of Harold F. Pitcairn is to forget that 29 years earlier, he had been recognized for "the greatest achievement in aeronautics or astronautics in America".
Bruce, Dr.
Cold Weather Testing of the Bell 525 RelentlessF-0076-2020-1636210/5/2020
In the winter months of January-March 2019, two Bell 525 test aircraft completed cold weather testing at Yellowknife Canada, some 1900 nm from Bell’s Flight Research Center in Arlington, TX. Testing was aimed at demonstrating aircraft stability, performance, and flight characteristics at extreme temperatures as required by CFR Part 29. Since regulations only permit limited temperature extrapolation, the cold temperature tests must include the limit of forward speed in a dive (VNE), and assessments of performance, controllability, autorotation, and static stability. This paper describes some of the unique environmental conditions and factors that any rotorcraft development program could experience in cold weather testing. The paper also gives a technical description of the required testing, where arctic conditions reached as low as -40° F or C (the temperature scales are the same at this temperature). Testing exposed the aircraft to overnight cold-soaks that brought fluids, seals, windshields, electronics, and elastomeric bearings to their low temperature specification, all at the same time. For the 525, test results demonstrated that the aircraft was ready for start-up and operation in extreme cold. The criteria necessary for meeting certification requirements in cold weather were also demonstrated in the series of tests and showed that the rotor was free from any adverse effects due to aerodynamic compressibility, had low vibration, acceptable loads and was free from any instability, even at speeds greater than VNE.
Regnier, Bradley, Baden, Joel, Brand, Albert, Lindauer, Patrick, O'Neil, Joshua, Schillings, John
Estimating Handling Qualities Ratings from Slalom Flight Data: A Psychophysical PerspectiveF-0076-2020-1638710/5/2020
This work examines the handling qualities (HQ) rating scale from a psychophysical perspective, characterizing workload as the response to a stimulus composed of input to the pilot and pilot outputs. Previous work by the author examining three different display tracking tasks indicated that pilot workload is effectively a logarithmic function of tracking error rate and control rate. This approach, called the Spare Capacity OPerations Estimator (SCOPE), is extended to flight and Handling Qualities data collected (109 runs) for the slalom Mission Task Element (MTE) using the U.S. Army’s JUH-60A RASCAL aircraft. Attitude and Rate Command response types as well as various forcefeel configurations were tested. Based on flight data observation a novel and intuitive action model is proposed for the slalom MTE whereby the pilot operates on the relative angle between the ground track and the upcoming cone’s location (effectively the cone’s location on the windscreen relative to the aircraft nose, assuming a no-wind environment). Proximity to an approaching cone determines which of two strategies is active: maintaining a constant relative angle or maintaining the relative angular rate constant. A method is proposed for mapping Handling Qualities (HQ) ratings to flight data performance and the workload estimate, offering the possibility for easing the requirement that a pilot trained in HQ evaluation fly test maneuvers. Applying this approach to the slalom maneuver produced good correlation between actual and estimated HQ ratings over the varying aircraft and inceptor feel system dynamics.
Bachelder, Edward, Aponso, Bimal, Lusardi, Jeffrey, Godfroy-Cooper, Martine
Optical Window for Far-IR Instruments Using Thin TOPAS® FilmTBMG-358091/1/2020
Most flight instruments that use cryogenics or non-cryogenics require physical isolation of their internal instruments (sensors, detectors, spectrometers) from the external environment. This isolating window film also needs to be transparent in the operational frequency of the internal instruments to detect electromagnetic waves. As such, the film needs to have the necessary strength to hold the vacuum pull and provide a low transmission loss.
Atomically Thin Heat Shield Protects Electronic DevicesTBMG-3526610/1/2019
Excess heat given off by smartphones, laptops, and other electronic devices contributes to malfunctions and, in extreme cases, can even cause lithium batteries to explode. To guard against issues, engineers often insert glass, plastic, or layers of air as insulation to prevent heat-generating components like microprocessors from causing damage.
Tuning Material Color and Thermal Properties SeparatelyTBMG-348988/1/2019
The color of a material can often tell how it handles heat. With clothing, for example, the darker the pigment, the warmer you're likely to feel on a hot day. Likewise, the more transparent a glass window, the more heat it can let through. A material's responses to visible and infrared radiation are often naturally linked.
A Three-Layer Thermodynamic Model for Ice Crystal Accretion on Warm Surfaces: EMM-C2019-01-19636/10/2019
Ingestion of high altitude atmospheric ice particles can be hazardous to gas turbine engines in flight. Ice accretion may occur in the core compression system, leading to blockage of the core gas path, blade damage and/or flameout. Numerous engine powerloss events since 1990 have been attributed to this mechanism. An expansion in engine certification requirements to incorporate ice crystal conditions has spurred efforts to develop analytical models for phenomenon, as a method of demonstrating safe operation. A necessary component of a complete analytical icing model is a thermodynamic accretion model. Continuity and energy balances are performed using the local flow conditions and the mass fluxes of ice and water that are incident on a surface to predict the accretion growth rate. In this paper, a new thermodynamic model for ice crystal accretion is developed through adaptation of the Extended Messinger Model (EMM) from supercooled water conditions to mixed phase conditions (ice crystal and supercooled water). A novel three-layer accretion structure is proposed and the underlying equations described. The EMM improves upon the original model for airframe icing, the Messinger Model, by permitting a linear temperature gradient through the ice and water layers. This in turn allows prediction of the time over which water exists in isolation on an initially warm surface, before an ice layer forms. This is of particular interest to engine icing, as surfaces may initially be significantly above freezing temperature, before cooling on exposure to ice particles. The method is solved in a multi-step approach, where the overall exposure time is divided into discrete windows, and the calculation performed over each window. This allows the local flow conditions to be updated between windows, permitting the incorporation of a reducing flow enthalpy due to particle evaporation, as well as transient engine operation. Model results are then compared to experimental results. Comparisons are made to solutions generated using the standard Messinger Model.
Bucknell, Alexander, McGilvray, Matthew, Gillespie, David, Jones, Geoffrey, Collier, Benjamin
Simulations of Thin Film Dynamics on a Flat Plate and an Airfoil2019-01-19386/10/2019
The goal of the present study is to investigate the dynamics of a thin water film on a flat plate and an airfoil using direct numerical simulation (DNS). The first case for a wetted flat plate is used to model former experiments and investigate the dynamics of a wind-driven water film. The second case for a thin film on a NACA 0012 airfoil of chord length 0.5 m is used to investigate the dynamics of a wind-driven water film on a curved surface. Particular attention is paid to the interaction between the liquid film and the air shear-layer above the film. As the incoming airflow moves over the thin water film, instability is triggered at the gas-liquid interface. Interfacial waves develop and are advected downstream. The interaction between the air flow and the interfacial waves induces shedding vortices near the interface, which in turn perturb the liquid film farther downstream. Simulations are performed using the open source multiphase flow solvers, Gerris and Basilisk. Both solvers employ a finite-volume approach and the interface is captured using a Volume-of-Fluid (VOF) method. While the long-term goal of this research effort is to investigate glaze ice formation in water films on airfoils, the current simulations focus on liquid film dynamics starting with a constant thickness exposed to a relatively low flight airspeed. The resulting simulations demonstrate the unsteady film dynamics and thickness evolution and natural waviness generated by the liquid-film and free-stream flow interactions.
Sakakeeny, Jordan, McClain, Stephen T., Ling, Yue
A Penalization Method for 2D Ice Accretion Simulations2019-01-19396/10/2019
Numerical tools for 3D in-flight icing simulations are not straightforward to automate when seeking robustness and quality of the results. Difficulties arise from the geometry and mesh updates which need to be treated with care to avoid folding of the geometry, negative volumes or poor mesh quality. This paper aims at solving the mesh update issue by avoiding the re-meshing of the iced geometry. An immersed boundary method (here, penalization) is applied to a 2D ice accretion suite for multi-step icing simulations. The suggested approach starts from a standard body-fitted mesh, thus keeping the same solution for the first icing layer. Then, instead of updating the mesh, a penalization method is applied including: the detection of the immersed boundary, the penalization of the volume solvers to impose the boundary condition and the extraction of the surface data from the field solution. Although the current work is intended for 3D simulations, the content of this paper is limited to 2D applications to show the feasibility of the method. Tests are performed on multi-step rime and glaze ice cases where it is observed that the penalization method is able to produce sensible ice shapes compared to a body-fitted approach. However, accurate results are only achieved if the mesh is a priori refined in the zone where ice accretion is expected. The paper will further discuss the computational time, mesh refinement requirements, accuracy, limitations and recommendations for improvement of the penalization method applied to icing.
Lavoie, Pierre, Blanchard, Ghislain, Radenac, Emmanuel, Laurendeau, Eric, Villedieu, Philippe
Separating-Reattaching Flows Over an Iced Airfoil2019-01-19466/10/2019
Delayed Detached Eddy Simulations (DDES) of separating-reattaching flows on the suction side of an ice-contaminated airfoil were conducted. A single-section straight-wing NACA23012 airfoil with leading-edge ice was studied. The geometry represents a realistic glaze horn-ice contamination obtained during the icing test campaigns described in [1], which has aerodynamic data for comparison. The three-dimensional transient flow behavior was simulated using the open-source flow solver OVERFLOW, version 2.2l [2] developed by NASA Langley Research Center. Configurations at three angles of attack that exhibit unsteady flow behavior starting with the bursting angle were examined at Mach number of 0.18 and Reynolds number of 1.8x106. As the stall angle was approached the aerodynamic performance parameters displayed large-scale unsteadiness where periods of attached and separated flows were observed. The time-averaged results show good agreement with the aerodynamic test data. The calculated Strouhal number for the self-sustained low-frequency oscillations is consistent with the previous experimental research.
Oztekin, Ezgi, Riley, James
Numerical Simulation of Aircraft and Variable-Pitch Propeller Icing with Explicit Coupling2019-01-19546/10/2019
A 3D CFD methodology is presented to simulate ice build-up on propeller blades exposed to known icing conditions in flight, with automatic blade pitch variation at constant RPM to maintain the desired thrust. One blade of a six-blade propeller and a 70-passenger twin-engine turboprop are analyzed as stand-alone components in a multi-shot quasi-steady icing simulation. The thrust that must be generated by the propellers is obtained from the drag computed on the aircraft. The flight conditions are typical for a 70-passenger twin-engine turboprop in a holding pattern in Appendix C icing conditions: 190 kts at an altitude of 6,000 ft. The rotation rate remains constant at 850 rpm, a typical operating condition for this flight envelope. Two icing conditions are simulated: air static temperature -23 °C, LWC 0.2 g/m3 and MVD 20 microns resulting in rime ice, and air static temperature -16 °C, LWC 0.3 g/m3 and MVD 20 microns resulting in mixed ice with rime to glaze transition in the radial direction. The ice shapes in both conditions are assumed to remain intact and attached to the blade, based on a predictive ice shedding calculation carried out a priori. The iced geometries are automatically remeshed at each shot using ANSYS FENSAP-ICE and Fluent Meshing tools. Solutions for the 2-meter blade are computed in a periodic domain to reduce computational costs. The pitch variation is a fully-automated process for each icing shot that uses an iterative Newton search on the blade position to converge the thrust to 0.1% of the target value.
Ozcer, Isik, Baruzzi, Guido S., Desai, Miraj, Yassin, Maged
Numerical Investigation of Wiper Drawback2019-01-06404/2/2019
Windscreen wipers are an integral component of the windscreen cleaning systems of most vehicles, trains, cars, trucks, boats and some planes. Wipers are used to clear rain, snow, and dirt from the windscreen pushing the water from the wiped surface. Under certain conditions however, water which has been driven to the edge of the windscreen by the wiper can be drawn back into the driver’s field of view by aerodynamic forces introduced by the wiper motion. This is wiper drawback, an undesirable phenomenon as the water which is drawn back on to the windscreen can reduce driver’s vision and makes the wiper less effective. The phenomena of wiper drawback can be tested for in climatic tunnels using sprayer systems to wet the windscreen. However, these tests require a bespoke test property or prototype vehicle, which means that the tests are done fairly late in the development of the vehicle. Furthermore, these results do not provide significant insight into the mechanisms driving the wiper drawback. In order to better understand wiper drawback a numerical simulation is presented of a configuration known to exhibit this phenomenon. This requires the inclusion into an aerodynamics solver of: moving wipers, a surface film model, and a representation of airborne spray. Using the results of this simulation, the forces causing the drawback of the water film, along with the mechanism for introducing these forces are studied. Through understanding the driving factors in wiper drawback, it can be avoided earlier in the development cycle.
Jilesen, Jonathan, Gaylard, Adrian, Linden, Tom
Chip Measures Quantities with Quantum PrecisionTBMG-341824/1/2019
Many devices use light to probe the quantum states of atoms in a vapor confined in a small cell. Atoms can be highly sensitive to external conditions, and therefore make superb detectors. Devices based on light interactions with atomic vapors can measure quantities such as time, length, and magnetic fields, and have applications in navigation, communications, medicine, and other fields. Such devices generally must be assembled by hand.
Products of Tomorrow: October 2018TBMG-3309510/1/2018
This column presents technologies that have applications in commercial areas, possibly creating the products of tomorrow. To learn more about each technology, see the contact information provided for that innovation.
Ultra-Light Weight Automotive Door: Design and Validation2018-01-01114/3/2018
An Ultra-Light Door (ULD) has been developed that is 40% lighter than a baseline 2016 mid-size vehicle’s driver side door. The ULD scope encompasses the entire door, including the door-in-white (DIW), interior trim, glazing, hardware, wiring, etc. To achieve such a substantial mass reduction while still meeting the baseline vehicle’s performance metrics (including safety, durability, NVH, appearance, etc.) at a minimal cost increase, the door design relies on a comprehensive full system approach that includes a unique architecture in addition to lightweight materials and components. This paper details the ULD design concept, simulated performance results, the current status of vehicle level validation, and comparisons between component level CAE predicted performance and physical test results.
Reaburn, Timothy, Skszek, Timothy W.
Investigation of Interior Noise from Generic Side- View Mirror Using Incompressible and Compressible Solvers of DES and LES2018-01-07354/3/2018
Exterior turbulent flow is an important source of automobile cabin interior noise. The turbulent flow impacts the windows of the cabins to excite the structural vibration that emits the interior noise. Meanwhile, the exterior noise generated from the turbulent flow can also cause the window vibration and generate the interior noise. Side-view mirrors mounted upstream of the windows are one of the predominant body parts inducing the turbulent flow. In this paper, we investigate the interior noise caused by a generic side-view mirror. The interior noise propagates in a cuboid cavity with a rectangular glass window. The exterior flow and the exterior noise are computed using advanced CFD methods: compressible large eddy simulation, compressible detached eddy simulation (DES), incompressible DES, and incompressible DES coupled with an acoustic wave model. The last method is used to simulate the hydrodynamic and acoustic pressure separately. The pressure fluctuations of the flow and noise are imposed on the window in the computation of the interior noise, but the reversal effect of the window vibration feeding back on the flow is neglected in the flow simulation. The localized flow characteristics are discussed. The energetic surface pressure appears in the regions where the shear layer from the mirror side edge impinges on the window. The contributions of the hydrodynamic and acoustic pressure to the interior noise are quantified. The acoustic component is found to be more efficient in the interior noise generation and to play the dominant role at high frequencies.
Yao, Huadong, Davidson, Lars, Chroneer, Zenitha
Simplifications Applied to Simulation of Turbulence Induced by a Side View Mirror of a Full-Scale Truck Using DES2018-01-07084/3/2018
In this paper, the turbulent flow induced by a production side-view mirror assembled on a full-scale production truck is simulated using a compressible k-ω SST detached eddy simulation (DES) approach -- the improved delayed DES (IDDES). The truck configuration consists of a compartment and a trailer. Due to the large size and geometric complexity of the configuration, some simplifications are applied to the simulation. A purpose of this work is to investigate whether the simplifications are suitable to obtain the reasonable properties of the flow near the side-view mirror. Another objective is to study the aerodynamic performances of the mirror. The configuration is simplified regarding two treatments. The first treatment is to retain the key exterior components of the truck body while removing the small gaps and structures. Furthermore, the trailer is shaped in an apex-truncated square pyramid. This simplification is proposed based on the assumption that the downstream flow near the trailer has limited effect on the flow near the mirror. To assess the influences of the simplifications, the flow fields computed from the original and simplified configurations are compared. The regions on the window that are subjected to significant hydrodynamic impingement are identified. The mirror and A-pillar introduce the impingement. The frequency spectra of the surface pressure fluctuations on the window are studied. The frequencies of the peaks in the spectra are the same as the characteristic frequencies of the free shear layers that develop from the mirror side-edges near the window. The simplifications are found as feasible treatments to reproduce the flow characteristics of the original geometry.
Yao, Huadong, Chroneer, Zenitha, Davidson, Lars
Effects of Rear Slant Angles on the Flow Characteristics of the Ahmed Body by IDDES Simulations2018-01-07204/3/2018
The present study aims to investigate the effects of the several rear slant angles, φ = 25°, 30°, 32°, 33° and 35°, on the wake characteristics downstream of the Ahmed body because the angle of the rear window plays an important role in the flow characteristics. This work presents numerical simulations using ISIS-CFD flow solver which is developed by Centrale Nantes and CNRS. The turbulence model used is an hybrid RANS-LES model: the Improved Delayed Detached Eddy Simulation (IDDES). Detailed discussions of the flow features are provided using time-averaged streamlines, vorticity contours, turbulent kinetic energy contours and an iso-surface of l2. Drag and lift coefficients are also presented. In the symmetry plane, three critical flow points, which correspond to foci of separation and saddle point in the wake of the Ahmed body, and the focus of separation over the slanted surface are presented. When the slant angle increases, these critical points move near the Ahmed body before moving away the model when the slant angle is higher than 33°. For the slant angle φ = 35°, a low drag configuration is predicted while for the other slant angles, a high drag flow configuration is predicted where two C-pillars vortex are present. These vortices move away the model when the slant angle increases.
Guilmineau, Emmanuel
Utilizing spectral analysis to quantify resolution of low frequency behavior in testing commercial vehicles2018-01-07474/3/2018
Despite the recent broadening of acceptable test methods for certifying aerodynamic performance, there has been little attention on how to determine the time averaging window used for providing mean forces. This is of particular relevance to the assessment of commercial vehicles as they are significantly affected by low-frequency patterns that are hard to predict and vary with different geometry configurations. Published guidelines in the industry suggest that good engineering judgement be used and a qualitative assessment of force histories is adequate. These suggested methods leave the accuracy of the time averaging to the experience and judgement of the user and is highly dependent on the specific characteristics of the benchmark case. Furthermore these methods are not able to quantify the error present due to motions slower than length of the sampled data. In order to robustly determine appropriate averaging window a new method is proposed which utilizes spectral analysis of the drag. By investigating changes in the power spectral density for different averaging windows it is possible to determine adequate averaging time as well as to assess the error introduced by selecting a particular averaging window. The method detailed presently is applied to both wind tunnel measurements and computation fluid dynamics simulations.
Landfried, Douglas Tyler, Alex, David, Mosedale, Andrew
Measurements of the Evaporation Behavior of the Film of Fuel Blends2018-01-02904/3/2018
The formation of fuel film in the combustion cylinder affects the mixing process of the air and the fuel, and the process of the combustion propagation in engines. Some models of film evaporation have been developed to predict the evaporation behavior of the film, but rarely experimental results have been produced, especially when the temperature is high. In this study, the evaporation behavior of the film of different species of oil and their blends at different temperature are observed. The 45 μL films of isooctane, 1-propanol, 1-butanol, 1-pentanol, and their blends were placed on a quartz glass substrate in the closed temperature-controlled chamber. The shape change of the film during evaporation was monitored by a high-speed camera through the window of the chamber. First, the binary blends film of isooctane and one of the other three oils were evaporated at 30 °C, 50 °C, 70 °C and 90 °C. Secondly, the pure films of isooctane, 1-propyl alcohol, 1-butanol and 1-pentanol were evaporated at 90 °C. Finally, after the data processing in Matlab, the data of the volume change, average thickness, and maximum thickness were obtained. The results also showed that there would be three evaporation periods according to different volumetric evaporation rates. With the increase of temperature, the first period would have a higher percentage of the whole evaporating volume of film. The evaporation behaviors were similar for Pr50 (50% isooctane and 50% 1-propanol) when the temperatures are 70 °C and 90 °C. Additionally, the evaporation behaviors were similar for Pr50 and B50 (50% isooctane and 50% 1-butanol) when the temperature is at 90 °C. Although there were small differences of the boiling points between 1-propanol and isooctane, the isooctane evaporated faster because of its higher vapor pressure and lower latent heat.
Liang, Zhengxing, Yan, Junhao, Li, Gang, Lee, Timothy, Zhang, Li, Lee, Chia-Fon
Measurement of Soot Concentration in a Prototype Multi-Hole Diesel Injector by High-Speed Color Diffused Back Illumination Technique2017-01-225510/8/2017
A prototype multi-hole diesel injector operating with n-heptane fuel from a high-pressure common rail system is used in a high-pressure and high-temperature test rig capable of reaching 1100 Kelvin and 150 bar under different oxygen concentrations. A novel optical set-up capable of visualizing the soot cloud evolution in the fuel jet from 30 to 85 millimeters from the nozzle exit with the high-speed color diffused back illumination technique is used as a result of the insertion of a high-pressure window in the injector holder opposite to the frontal window of the vessel. The experiments performed in this work used one wavelength provide information about physical of the soot properties, experimental results variating the operational conditions show the reduction of soot formation with an increase in injection pressure, a reduction in ambient temperature, a reduction in oxygen concentration or a reduction in ambient density.
Payri, Raul, Gimeno, Jaime, Cardona, Santiago, Ayyapureddi, Sridhar
Products of Tomorrow: October 2017TBMG-2769210/1/2017
This column presents technologies that have applications in commercial areas, possibly creating the products of tomorrow. To learn more about each technology, see the contact information provided for that innovation.
Plasma-Assisted Catalytic Reverse Water Gas Shift ReactorTBMG-2767810/1/2017
For improving CO2 conversions for a low-temperature CO2 methanation process, a mechanism of using reverse water gas shift (RWGS) reaction as an intermediate step to generate the more reactive CO species for the methanation process was developed. The challenge was to achieve useful conversions of RWGS reaction (CO2 to CO by hydrogenation) at low temperatures (200-300 °C), which is not possible with conventional catalytic reactors. Achieving useful conversions (up to ~50%) is not possible at the desired temperature window of 200-300 °C with a conventional catalytic reactor due to equilibrium limitations of the endothermic RWGS reactor.
Products of Tomorrow: September 2017TBMG-275279/1/2017
This column presents technologies that have applications in commercial areas, possibly creating the products of tomorrow. To learn more about each technology, see the contact information provided for that innovation.
A Modal Study of Damping Treatments to Improve Low Frequency Sound Transmission Loss of a Structure2017-01-18526/5/2017
Most of NVH related issues start from the vibration of structures where often the vibration near resonance frequencies radiates the energy in terms of sound. This phenomenon is more problematic at lower frequencies by structureborne excitation from powertrain or related components. This paper discusses a laboratory based case study where different visco-elastic materials were evaluated on a bench study and then carried on to a system level evaluation. A body panel with a glazing system was used to study both airborne and structureborne noise radiation. System level studies were carried out using experimental modal analysis to shift and tune the mode shapes of the structure using visco-elastic materials with appropriate damping properties to increase the sound transmission loss. This paper discusses the findings of the study where the mode shapes of the panel were shifted and resulted in an increase in sound transmission loss. This eventually resulted in reduced sound level inside the cabin.
Deshpande, Satyajeet P., Saha, Pranab, Cone, Kerry
Two-Component Injection Molding as a Noise Countermeasure for Polycarbonate Glazing2017-01-18176/5/2017
Polycarbonate (PC) glazing as a one-for-one glass replacement offers a 50% weight reduction, but exhibits several dB lower sound transmission loss (STL) in the low frequency range where tire and engine noise are dominant. In the high frequency range where wind noise is dominant, PC glazing offers an STL at least comparable to its glass counterpart, and an STL exceeding glass when this frequency range encompasses the glass coincidence frequency. However, a key value proposition of PC glazing is the opportunity for feature integration afforded by the injection molding process generally used for forming such glazing. Two-component (2K) molding fuses a second shot of plastic material behind, and along the perimeter of, the transparent PC first shot. This second shot can incorporate features and implement functions that require additional components attached or peripheral to a glass version. In effect, a portion of the weight reduction entitlement for PC glazing is transferred to the host vehicle, such that the weight reduction of the glazing itself is less than 50%. Moreover, the second shot tends to stiffen the PC glazing relative to the first shot alone. We show experimentally that these two effects contribute to making the low frequency STL of a 2K PC rear window intermediate between the first shot alone and the comparable glass version. Thus, integration operates as a noise countermeasure for glazing weight reduction. Injection molded PC glazing can also be designed for reduced aerodynamic (high frequency) noise, further improving its noise profile versus glass.
Gasworth, Steven M., Nilajkar, Vasudev, Terragni, Matteo
Using the Modal Response of Window Vibrations to Validate SEA Wind Noise Models2017-01-18076/5/2017
The SEA model of wind noise requires the quantification of both the acoustic as well as the turbulent flow contributions to the exterior pressure. The acoustic pressure is difficult to measure because it is usually much lower in amplitude than the turbulent pressure. However, the coupling of the acoustic pressure to the surface vibration is usually much stronger than the turbulent pressure, especially in the acoustic coincidence frequency range. The coupling is determined by the spatial matching between the pressure and the vibration which can be described by the wavenumber spectra. This paper uses measured vibration modes of a vehicle window to determine the coupling to both acoustic and turbulent pressure fields and compares these to the results from an SEA model. The interior acoustic intensity radiating from the window during road tests is also used to validate the results.
DeJong, Richard, Ebbitt, Gordon
Structural and Flight Test of a Composite Bubble Door for the CHI CH-47DF-0073-2017-121915/9/2017
ABSTRACT Columbia Helicopters, Inc, (CHI) has procured several military-surplus CH-47D helicopters for use in heavy-lift operations, including fire-fighting and other external lift operations. For decades, CHI has successfully utilized Direct Visual Operational Control (DVOC) to precisely control the load at the end of a long line. The key to DVOC is the use of a bubble window at both pilot and co-pilot positions on the aircraft, which allows the pilot flying the aircraft to see the load directly. CHI designed, manufactured, tested, and qualified a replacement cockpit door to hold a bubble window in the CH-47D. The new doorframe is made of carbon-fiber epoxy composite, holds an 18-inch-deep bubble window in the upper section, and holds a sliding ventilation window in the lower section. An abbreviated composite building block test was completed to prove the structure, and flight test was used to determine the optimal flight attitude to evacuate the cockpit of smoke.
Pilkington, Lawrence, Solem, Courtney, Royce, Anna
Simplified Approach for Optimizing Lightening Holes in Truck Frames for Durability Performance2017-01-13453/28/2017
During development of new vehicles, CAE driven optimizations are helpful in achieving the optimal designs. In the early phase of vehicle development there is an opportunity to explore shape changes, gage reduction or alternative materials as enablers to reduce weight. However, in later phases of vehicle development the window of opportunity closes on most of the enablers discussed above. The paper discusses a simplified methodology for reducing the weight in design cycle for truck frames using parametric Design of Experiments (DOE). In body-on-frame vehicles, reducing the weight of the frame in the design cycle without down gaging involves introducing lightening holes or cutouts while still maintaining the fatigue life. It is also known that the lightening holes might cause stress risers and be detrimental to the fatigue life of the component. Thus the ability to identify cutout locations while maintaining the durability performance becomes very critical. This paper describes a method of effectively locating these lightening holes on the truck frame, thereby reducing the weight of the vehicle while preserving the durability performance. The process to incorporate these lightening holes is a multi-step approach beginning with a stress envelope creation. The load paths for each component are identified based on the stress envelops generated in the fatigue code using a complete set of proving ground loading events. A subsequent step includes tuning those lightening holes to meet the durability, strength and stiffness requirements via the automated process of resizing the lightening holes to their optimal sizes. The final verification is carried out with the regular analysis procedure to verify the lightening holes effect on the durability performance of the structure.
bhat, Ramachandra, Sharma, Nitin, Rivard, Clifford, Thomson, Kevin
Investigation of a Dual HVAC MAC System with Three Row Ducts Using 1D Modeling2017-01-01643/28/2017
In an automotive air-conditioning (AC) system, upfront prediction of the cabin cool down rate in the initial design stage will help in reducing the overall product development (PD) time. Vehicle having higher seating capacity will have higher thermal load and providing thermal comfort to all passengers uniformly is a challenging task for the automotive HVAC (Heating Ventilation and Air conditioning) industry. Dual HVAC unit is generally used to provide uniform cooling to a large cabin volume. One dimensional (1D) simulation is being extensively used to predict the HVAC performance during the initial stage of PD. The refrigerant loop with components such as compressor, condenser, TXV and evaporator was modeled. The complicated vehicle cabin including the glazing surfaces and enclosures were modeled as a three row duct system using 1D tool AMESim®. The material type, density, specific heat capacity and thermal conductivity of the material were specified. The actual vehicle driving conditions as per test standard were used to validate the transient 1D HVAC performance simulations. The heat gain values of the panel ducts were adjusted to reduce the deviation from test. The simulated results for average cabin temperature and grill outlet temperature were compared against a surrogate vehicle test data. The detailed comparison of test data and simulation results were plotted and identified the simulation parameter which affects the correlation. Studies were carried out to understand the influence of thermal parameters on the performance of dual HVAC system and optimal values were arrived for the system under study.
Muthusamy, Venkatesan, Sathish Kumar, S., Sambandan, Saravanan
Sensitivity Analysis of Windshield Defrost Characteristics Impact on Occupant Thermal Comfort2017-01-01433/28/2017
During cabin warm-up, effective air distribution by vehicle climate control systems plays a vital role. For adequate visibility to the driver, major portion of the air is required to be delivered through the defrost center ducts to clear the windshield. HVAC unit deliver hot air with help of cabin heater and PTC heater. When hot air interacts with cold windshield it causes thermal losses, and windshield act as sink. This process may causes in delay of cabin warming during consecutive cabin warming process. Thus it becomes essential to predict the effect of different windscreen defrost characteristics. In this paper, sensitivity analysis is carried for different windscreen defrosts characteristics like ambient conditions, modes of operation; change in material properties along with occupant thermal comfort is predicted. An integrated 1D/3D CFD approach is proposed to evaluate these conditions. Detailed thermal boundary conditions are considered in 1D heat transfer method and coupled with 3D convection human comfort model.
Kandasamy, Neelakandan, Whelan, Steve
Practical Design Considerations for Lightweight Windshield Applications2017-01-13063/28/2017
Automotive manufacturers are requiring lightweight materials, including glazing materials to improve vehicle fuel economy mandates. Since windshields are one of the largest glazing surface areas, reducing the thickness of the glass in its construction can significantly provide weight savings opportunities. Automotive glazing design considerations must include overall glass strength, rigidity, acoustical, and solar performance, which are affected by changes of glass thicknesses. This paper will evaluate those design considerations in the lightweighting of windshield glazings. One important design consideration for the windshield position is the impact of debris from the environment. Lightweighting of glazings in this body position affects the way the construction reacts to an impact. Use of asymmetry in glass plies in a laminated construction can have a marked effect on the part’s impact performance and surface damage creation. Various lightweight glazing constructions will be analyzed, and based upon basic strength and stiffness, the probability of failure from stone impact in parts per million is predicted from a statistical model. Further testing and analysis will be done to demonstrate lifetime effects in windshield glazings with respect to stone impacts will be discussed. As a glazing part becomes thinner, the material choices have an impact on light transmission and solar performance. In order to maintain light transmission compliance (70%, with light illuminant “A” in the United States) and solar performance at comparable levels to standard products, enhanced material choices in glass composition, PVB composition, and coating technologies will be evaluated. Additionally, as a glazing part becomes thinner, more exterior sound is transferred through the construction. This effect can be managed with acoustical interlayers at higher frequencies through constrained layer damping. Design considerations for the relative thickness of glass plies in the construction of the windshield will be evaluated and optimal construction options presented.
Walawender, Chester, Ulizio, Michael, Lampman, DeWitt, Rustagi, Mukesh, Skeen, Jason
A Statistical Description of Knock Intensity and Its Prediction2017-01-06593/28/2017
Cycle-to-cycle variation in combustion phasing and combustion rate cause knock to occur differently in every cycle. This is found to be true even if the end gas thermo-chemical time history is the same. Three cycles are shown that have matched combustion phasing, combustion rate, and time of knock onset, but have knock intensity that differs by a factor of six. Thus, the prediction of knock intensity must include a stochastic component. It is shown that there is a relationship between the maximum possible knock intensity and the unburned fuel energy at the time of knock onset. Further, for a small window of unburned energy at knock onset, the probability density function of knock intensity is self similar when scaled by the 95th percentile of the cumulative distribution, and log-normal in shape. A methodology to predict the maximum possible knock intensity based on the volumetric expansion rate of the end gas was developed, and the expansion rate was modeled based on blast wave theory, which is proportional to the energy of the initial explosion. The results showed a comparable level of scatter as the measurements.
Ghandhi, Jaal, Kim, Kenneth Seonguk
Variably Transmittive, Electronically Controlled EyewearTBMG-261791/1/2017
During instrument flight training, the pilot must have his/her view through the aircraft windscreen restricted to simulate low-visibility conditions while permitting the pilot to view the instrument panel. In one current method, a hood is draped across the aircraft windscreen, or a face mask or blackened glasses are worn by the pilot. All such current methods create potentially hazardous disorientation and an unnatural environment for the trainee. In particular, the face mask and blackened glasses restrict the pilot’s peripheral vision, and require uncomfortable and unnatural head positions in order to see the entire instrument panel.
Automatic Drilling, Countersink and Riveting Experience. Aernnova Highlights Based on More Than 20 Million of Fasteners Installed2016-01-20899/27/2016
Aernnova experience on automatic drilling operations started in 1,999. The company signed a new contract with Embraer, to design, manufacture and assembly several structures of the model 170. It was big news for the company. But after that minute of pride, manufacturing engineering people of the company started to think about the process to assemble those big panels of the Horizontal Stabilizer, Vertical Stabilizer and Rear Fuselages in the best Quality and Cost. There were a lot of rows of rivets to install. Some ideas arisen, but the final decision was to forget the available processes at that time and think about to automate the drilling, countersink and riveting of the stringers, doublers and window frames to the panels. There were a lot of doubts, figures to do and obstacles, but the company took the decision of going ahead with that process. That step changed the state of the art at that time in the company. The investment was important, the risks were high, and the beginnings were tough, as usual. During these years, the company has improved the process, reviewing thoroughly every step and every cycle, in order to improve the process and minimize the loss of time, wastes and the stops. Due to those improvements, nowadays, the company has a very smooth process, products with high quality and in the best possible cost. There is no other way of being able to install more than 20 millions of rivets within less than 13 years.
Guerra cEng, Jose, Castillo, Miguel Angel
Safety Release Fasteners Enable New Cabin/Cargo Decompression Concept2016-01-20829/27/2016
In the frame of incremental product improvement, AIRBUS has developed and implemented a new innovative rapid decompression / pressure relieve concept for the cargo compartment area. The core change lays with detaching the complete cargo lining panels from the substructure in case of a rapid decompression in the cargo area instead of using dedicated blow in panels. In that way, pressure equilibrium can be achieved by air flow through the opened areas around the cargo lining panels rather than through specific blow out / blow in venting areas. The key for this is a self-detaching fastener AIRBUS has developed in an outstanding cooperation with ARCONIC Fastening Systems & Rings (former Alcoa Fastening Systems & Rings) in Kelkheim, Germany. These fasteners are installed to keep the cargo lining panels in place and tight against smoke in case of fire which is one of the main purposes for their use. In case of a rapid decompression event in the cargo area, the multi-piece self-detaching fastener fails within a defined timeframe and releases the ceiling and sidewall panels. The main challenge was to develop a fastener that on the one hand fulfils the tightness requirements, characterised by a certain compression level of a drytape seal, as well as mechanical conditions such as hard landings, wheel imbalance, windmilling etc. but on the other hand detaches (releases) at a narrow pressure difference load window in a given timeframe. Also, since the fastener is frequently removed and re-installed in service, a high number of re-use cycles needed to be achieved.
Schomaker, Ralf, Knickrehm, Björn, Langediers, Jürgen
Narrowing of Attention and Functional Field of View for Helicopter Pilots in a Degraded Visual EnvironmentF-0072-2016-115935/17/2016
In an attempt to quantify the change in attentional allocation found during landing in degraded visual environments (DVE) for helicopter pilots, this study imposed a secondary visual task for pilots to complete while landing a simulated CH-53 helicopter. Pilots were tasked to identify visual cues as they appeared on the windscreen while they flew to a landing zone that had varying levels of DVE. It was found that pilots were less sensitive to the secondary visual task and slower to respond when landing in DVE conditions.
Geeseman, Joseph
Deck Motion Interface for MQ-8C Fire Scout Embarked AviationF-0072-2016-115745/17/2016
This paper provides a discussion of the challenges associated with embarking the MQ-8C Fire Scout (converted Bell 407) system onboard ships, focusing on the launch and recovery (L&R) process and equipment. The baseline version of Fire Scout, MQ-8C, along with all its improved derivatives is required to undergo ship suitability assessments in the form of dynamic interface (DI) testing, also known as helicopter-ship qualification analysis, aboard ship. DI testing evaluates all aspects of shipboard helicopter compatibility such as adequacy, effectiveness and safety of shipboard aviation support facilities and procedures for all ship-based helicopter types. To facilitate the upcoming at-sea ship-suitability assessment, a parallel effort was initiated to apply motion simulation defining deck interface experimentation ahead of sea trials. Analysis is made of various system component responses to the encountered motions and forces from a generic mono-hull vessel. Improvements in deck limits are estimated from the motion characterization of a platform in terms of, and as a function of, oleo compression and deflection, torque monitor along with indications of precise weight on wheels. At-sea preliminary validation study results are discussed and compared with simulated scenarios. This computational method employs sufficient performance criteria and correlates well with forecasted quiescent windows of deck motion. Results are presented in relation to deck energy problems normally confronted by a helicopter during recovery in progressively difficult conditions.
Ferrier, Bernard, Ernst, Robert, Sehgal, Ajay, Kim, Saiah
Experimental and Computational Study of Vehicle Surface Contamination on a Generic Bluff Body2016-01-16044/5/2016
This paper focuses on methods used to model vehicle surface contamination arising as a result of rear wake aerodynamics. Besides being unsightly, contamination, such as self-soiling from rear tyre spray, can degrade the performance of lighting, rear view cameras and obstruct visibility through windows. In order to accurately predict likely contamination patterns, it is necessary to consider the aerodynamics and multiphase spray processes together. This paper presents an experimental and numerical (CFD) investigation of the phenomenon. The experimental study investigates contamination with controlled conditions in a wind tunnel using a generic bluff body (the Windsor model.) Contamination is represented by a water spray located beneath the rear of the vehicle. The aim is to investigate the fundamentals of contamination in a case where both flow field and contamination patterns can be measured, and also to provide validation of modelling techniques in a case where flow and spray conditions are known. CFD results were obtained using both steady RANS and unsteady URANS solvers, combined with particle tracking methods. Steady RANS does not capture the wake structures accurately and this affects the contamination prediction. URANS is able to recover the large-scale wake unsteadiness seen in the experimental data, but the difference between the experimental and computational contamination distributions is still notable. The CFD is also able to provide further insight by showing the behaviour of particles of different sizes. Large particles are found to take on a ballistic trajectory and penetrate the wake. In contrast, small particles are shown to be less likely to become entrained into the wake.
Kabanovs, Anton, Varney, Max, Garmory, Andrew, Passmore, Martin, Gaylard, Adrian
Prediction of Aeroacoustical Interior Noise of a Car, Part-1 Prediction of Pressure Fluctuations on External Surfaces of a Car2016-01-16174/5/2016
A wall-resolving Large Eddy Simulation (LES) has been performed by using up to 40 billion grids with a minimum grid resolution of 0.1 mm for predicting the exterior hydrodynamic pressure fluctuations in the turbulent boundary layers of a test car with simplified geometry. At several sampling points on the car surface, which included a point on the side window, the door panel, and the front fender panel, the computed hydrodynamic pressure fluctuations were compared with those measured by microphones installed on the surface of the car in a wind tunnel, and effects of the grid resolution on the accuracy of the predicted frequency spectra were discussed. The power spectra of the pressure fluctuations computed with 5 billion grid LES agreed reasonably well with those measured in the wind tunnel up to around 2 kHz although they had some discrepancy with the measured ones in the low and middle frequencies. The Dynamic Smagorinsky Model (DSM) was adopted for the subgrid-scale turbulence model of LES while the resulting spatially-filtered Navier-Stokes equations of the incompressible fluid flow were solved by a Finite Element Method. In the second paper of this series of studies, the hydrodynamic pressure fluctuations computed on the car surfaces will be used as the unsteady loading for computing the panel vibration of the test car by using Finite Element Method, and finally the interior acoustical fields will be predicted by solving the Helmholtz equation for sound propagation. The contribution from the external acoustical field to the interior noise, which was not simulated by the present incompressible LES-based approach, was estimated based on the acoustic analogy, and was confirmed to be negligibly small compared with those from the hydrodynamic loading in the present case.
Yamade, Yoshinobu, Kato, Chisachi, Yoshimura, Shinobu, Iida, Akiyoshi, Iida, Keiichiro, Onda, Kunizo, Hashizume, Yoshimitsu, Gou, Yang
Surface Flow Visualization on a Full-Scale Passenger Car with Quantitative Tuft Image Processing2016-01-15824/5/2016
Flow visualization techniques are widely used in aerodynamics to investigate the surface trace pattern. In this experimental investigation, the surface flow pattern over the rear end of a full-scale passenger car is studied using tufts. The movement of the tufts is recorded with a DSLR still camera, which continuously takes pictures. A novel and efficient tuft image processing algorithm has been developed to extract the tuft orientations in each image. This allows the extraction of the mean tuft angle and other such statistics. From the extracted tuft angles, streamline plots are created to identify points of interest, such as saddle points as well as separation and reattachment lines. Furthermore, the information about the tuft orientation in each time step allows studying steady and unsteady flow phenomena. Hence, the tuft image processing algorithm provides more detailed information about the surface flow than the traditional tuft method. The main advantages over other flow visualization methods, such as oil paint, is that experimental facilities are not contaminated and statistical data can be extracted. The investigated surface pattern shows a symmetric flow on the entire rear end section of the passenger car. The flow field on the roof, backlight, and upper trunk deck is attached almost everywhere. However, two small regions indicate the presence of two counter-rotating vortices at the lower edge of the backlight (rear window). Those vortices are also detectable in the distribution of the tuft angle standard deviation. A bifurcation line is present at each side of the trunk due to the streamwise vortices originating at the C-pillars. The tuft streamlines created with this novel tuft method are compared to a standard oil paint flow visualization to validate the calculated tuft flow pattern. A critical comparison between the methods confirms that the flow tuft analysis algorithm functions flawlessly as a highly detailed flow analysis tool without the mess of oil paint.
Wieser, Dirk, Bonitz, Sabine, Lofdahl, Lennart, Broniewicz, Alexander, Nayeri, Christian, Paschereit, Christian, Larsson, Lars
Numerical Investigation of Geometry Effects on Flow, Heat Transfer and Defrosting Characteristics of a Simplified Automobile Windshield with a Single Row of Impinging Jets2016-01-02084/5/2016
The effect of jet geometry on flow, heat transfer and defrosting characteristics was numerically investigated for elliptic and rectangular impinging jets on an automobile windshield. Initially, various turbulence models within the commercial computational fluid dynamics (CFD) package FLUENT were employed and validated for a single jet, and the results indicated that the impinging jet heat transfer was more accurately predicted by the SST k -ω turbulence model, which was then utilized for this study. The aspect ratios (AR) of elliptic and rectangular jets were respectively 0.5, 1.0, and 2.0, with jet-to-target spacing h/d=2, 4 and jet-to-jet spacing c/d=4, and all those situations were numerically analyzed with the same air mass flow and jet open area. It was observed that the heat transfer coefficient and defrosting performance of the inclined windshield were significantly affected by the shape of the jet, and the best results were obtained with the elliptic jet arrangements. The average Nusselt number (Nu) of the entire windshield exhibited a considerable increase with the AR changing from 1 to 2 for both the elliptic and rectangular jets, whereas it varied a little with the AR changing from 0.5 to 1. Compared with the jets with lower AR, a substantial improvements (roughly 40% increase) in defrosting area could be achieved by utilizing the elliptic jet with AR=2 due to higher turbulence level and wider velocity spreading. Additionally, the results quantitatively demonstrated that the defrosting performance of the windshield not only depended on the average Nu, but more importantly on the uniformity of the air flow impinging on the whole windshield.
Du, Xuzhi, Yang, Zhigang, Zhou, Hua, Li, Qiliang, Jin, Zheyan
Design and Development of Demisting Device of a Commercial Vehicle and its Numerical as Well as Experimental Validation2016-01-02174/5/2016
Adequate visibility through the vehicle windshield over the entire driving period is of paramount practical significance. Thin water film (fog) that forms on the windshield mainly during the winter season would reduce and disturb the driver’s visibility. This water film originates from condensing water vapor on inside surface of the windshield due to low outside temperatures. Primary source of this vapor is the passenger’s breath, which condenses on the windshield. Hot and dry air which impinges at certain velocity and angle relative to the windshield helps to remove the thin water film (defogging) and hence improves driver’s visibility. Hence a well-designed demisting device will help to eliminate this fog layer within very short span of time and brings an accepted level of visibility. An attempt is made here to design and develop a demisting device for a commercial vehicle with the help of numerical and analytical approach and later on validated with experimental results. System configuration was finalized by analytical method followed by 3D (dimensional) modeling in CATIA. Steady state and transient computational fluid dynamics (CFD) analysis were carried out in CCM+ to predict the striking zone, airflow mapping over the windshield and transient defogging pattern respectively. The predicted transient behavior of windshield defogging was validated with experimental results obtained from prototype sample of demisting device. The numerical results of airflow mapping and transient defogging pattern were in good agreement with that of experimental data. Thus a methodology is developed which is very useful in reducing the number of prototypes, testing cost and the project development timeline by adopting numerical and analytical approach in the early stage of design and development cycle.
Sen, Somnath, Selokar, Mayur, Nisad, Diwakar, Kishore, Kamal
Analysis of Defogging Pattern on Windshield and Ventilation Load Reduction based on Humidity Distribution Control2016-01-02564/5/2016
In the winter, windshield glass fogging must be prevented through the intake of outdoor air into a vehicle. However, the corresponding energy loss via the ventilation system cannot be ignored. In the present study, the defogging pattern on the windshield is evaluated and the water vapor transportation in the flow field in the vehicle is analyzed in order to investigate the ventilation load by means of a numerical simulation. Some examined cases involve new outlet positions. Additionally, a new, energy-saving air supply method for defogging, with so-called “double-layer ventilator”, is proposed. In this method, one air jet layer is obtained via a conventional defogging opening in the vicinity of the windshield, supplying an outdoor air intake. The other jet consists of recirculated air that covers the outdoor air, preventing it from mixing with the surrounding air. The calculation results indicate that the exhaust opening location, from which the internal vehicle air is obtained for recirculation, affects the cabin flow field, the windshield fogging pattern and the ventilation load. The water vapor generated from human occupants did not spread well and that is why there was the humidity gradient in the vehicle. This means that the flow field must be considered in order to achieve efficient defogging, that is done by emitting the water vapor immediately. The double-layer method exhibits the same level of defogging performance as single-layer techniques, even with half the airflow velocity. The energy load can be reduced by approximately 5 % using the appropriate conditions.
Nagano, Hideaki, Tomita, Kenji, Tanoue, Yasuhiro, Kobayashi, Yuji, Kohri, Itsuhei, Kato, Shinsuke
Reliability Evaluation of Thin, Lightweight Laminates for Windshield Applications2016-01-14014/5/2016
The use of lightweight materials to produce automotive glazing is being pursued by vehicle manufacturers in an effort to improve fuel economy. As glazing’s become thinner, reduced rigidity means that the critical flaw size needed to create fracture becomes much smaller due to increased strain under load or impact. This paper documents experiments focused on the impact performance of several alternative thin laminate constructions under consideration for windshield applications (including conventional annealed soda-lime glass as well as laminates utilizing chemically strengthened glass), for the purpose of identifying new and unique failure modes that result from thickness reduction. Regulatory impact tests and experiments that focused on functional performance of laminates were conducted. Given the increased sensitivity to flaw size for thin laminates, controlled surface damage was introduced to parts prior to conducting the functional performance tests. Damage levels were selected based on teardown characterization of real world windshield parts that had been in-service. Regulatory impact testing showed that even very thin (< 2.3 mm total glass thickness) laminates could comply with requirements, as long as parts were properly laminated. Functional performance tests were more discriminating. External ball bearing impact experiments showed that as unstrengthened glass laminates became thinner, a fundamental shift in failure mode occurred, and there was an increased prevalence of fracture of the interior ply due to biaxial flexure. Laminates made with a thin interior ply of chemically strengthened glass did not experience fracturing of the interior ply. Ring-on-ring testing of annealed (unstrengthened) glass showed significant reduction in retained strength when minor use case surface damage was present; whereas compressive stress in chemically strengthened glass made it relatively unaffected by the use case damage. This difference between the two materials is the likely underlying cause of the shift in failure modes observed when impacted by the ball bearing.
Walawender, Chester S., Cleary, Thomas M., Huten, Timothy, Strong, Daniel
Virtual Windows to Supplement Conventional Spacecraft WindowsTBMG-241253/1/2016
Legacy NASA spacecraft windows suffer from specialized costs and operational constraints associated with embedding optically transparent apertures within structures that are designed to maximize strength, safety, and environmental integrity. A new approach to the legacy window solution may lead to a substantial decrease in program costs, while also enhancing crew safety and functional capability. The project includes integration of tiled displays, scene-stitching software, multiple cameras with real-time video imagery, and alternative display configurations and control input methods for scene and perspective change.
Numerical Simulation of Noise Transmission from A-pillar Induced Turbulence into a Simplified Car Cabin2015-01-23226/15/2015
At high cruising speed, the car A-pillars generate turbulent air flow around the vehicle. The resulting aerodynamic pressure applied on the windows significantly contributes to the total cabin noise. In order to predict this particular noise contribution, the physic of both the flow and the cabin needs to be accurately modeled. This paper presents an efficient methodology to predict the turbulent noise transmission through the car windows. The method relies on a two-step approach: the first step is the computation of the exterior aero-dynamic field using an unsteady CFD solver (PowerFLOW); the second step consists in the computation of the acoustic propagation inside the cabin using a finite element vibro-acoustic solver (ACTRAN). The simplified car cabin of Hyundai Motor Company, studied in this paper, involves aluminum skin, windows, sealant, inner air cavity and acoustic treatment inside the passenger compartment (porous material, damping layer). A pure vibro-acoustic model with hammer shock excitation on a window is first built. Acoustic results inside the cabin are then correlated with measurements in order to validate the vibro-acoustic modeling of the cabin, which is deemed as invariant regarding the imposed excitation types. Finally, aerodynamic pressure results from CFD are mapped on the structure mesh of the two lateral windows and the front windshield, causing structure vibration and consequently acoustic response in the cabin. Four flow conditions are studied, involving two cruising speeds (110km/h and 130km/h) and two yaw angles (0° and 10° orientations). The total wind noise level results and the relative contributions of the different windows/windshield are presented and compared to measurements.
Ganty, Bastien, Jacqmot, Jonathan, Zhou, Ze, Jeong, ChanHee
Operational Determination of Car Window Damping2015-01-23016/15/2015
Wind noise can be a significant event for automotive design engineers. The greenhouse glass plays an important role in the wind noise process. Robust estimates of the greenhouse glass damping are necessary for both understanding and modeling the role of the glass in the wind noise process. One unanswered question is whether the aerodynamic loads affect the window glass damping. To make this determination a method to assess the operational damping is required. The civil engineering community uses the random decrement technique to assess operational damping due to wind loads. The random decrement technique has been shown to be a normalized autocorrelation function. In this paper the damping is estimated directly from the autocorrelation function. In the first section the relationship between the damping and autocorrelation function is examined for white noise excitation. A single oscillator is examined as the first case. Extension to higher modal densities is discussed. Finally application to a car window is presented. The window results were limited by signal to noise problems.
Hill, Maxwell, Luo, Dan, Moeller, Mark
Assessment of Broadband Noise Generated by a Vehicle Sunroof at Different Flow Conditions using a Digital Wind Tunnel2015-01-23216/15/2015
For the automotive industry, the quality and level of the wind noise contribution has a growing importance and therefore should be addressed as early as possible in the development process. Each component of the vehicle is designed to meet its individual noise target to ensure the wind noise passenger comfort level inside the vehicle is met. Sunroof broadband noise is generated by the turbulent flow developed over the roof opening. A strong shear layer and vortices impacting on the trailing edge of the sunroof are typical mechanisms related to the noise production. Sunroof designs are tested to meet broadband noise targets. Experimentally testing designs and making changes to meet these design targets typically involves high cost prototypes, expensive wind tunnel sessions and potentially late design changes. To reduce the associated costs as well as development times, there is strong motivation for the use of a reliable numerical prediction capability early in the vehicle design process. Previous investigations have shown the possibility to use transient CFD/CAA simulations based on Lattice Boltzmann Methods to assess the wind noise performance of mirrors, wipers, underbody designs and buffeting performance of sunroofs and open side windows. This paper presents the use of this computational approach on two production vehicles to assess the broadband noise generated by a fully open sunroof. Computational predictions of mesh deflectors as well as yaw effect were validated against wind tunnel measurements. Also, detailed flow analysis was performed to understand the noise generation mechanisms and to explain the effect of the mesh deflector and flow yaw angle on the interior noise. Accurate prediction of the wind noise performance of the sunroof and the insight provided by the flow analysis proves that this computational approach can be used to make design decisions during the vehicle development process.
Oettle, Nicholas, Bissell, Andrew, Senthooran, Sivapalan, Meskine, Mohammed
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