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Plastic automotive lamp assemblies are vented by a variety of methods to reduce the likelihood of condensation forming in the lamp and to prevent water ingress lamp warranty returns. Previously, it has been shown that the humidity in a vented automotive lamp can be described empirically by a decreasing exponential (i.e. decay). It was also shown that this formula by applying Fick’s Law of Diffusion, particularly the exponential constant (k), can be related to basic physical properties of the lamp system. Specifically, the exponential constant is a ratio of the product of a characteristic cross-section area of the vent and the permeability of water vapor over the product of the lamp volume and a characteristic length of the vent. This description was shown to be less accurate at time t greater than 30 minutes and additional details of the vented lamp system were proposed for better fit to the experimental data.

Drawing from previous studies published in SAE, a software program describes physical progress of water intrusion into or released from a lamp assembly. This program, based on test data, calculates condensation quantity and clearing time. It calculates moisture exchange between a lamp assembly and ambient, considering the moisture contained in the air inside of the lamp and moisture stored on the wall surface or in the materials. This program is applicable to different scenarios, such as initial humidity conditions of a lamp assembly, lamp size, type, venting type and test performance specifications. The significance of the program application in guiding test performance will also be addressed.

In the automotive lighting industry, car manufacturers (OEMs) require that lamps pass vibration resonance test. Failure to pass this test means that the lamp cannot be delivered to the customer. Resonant frequency is a direct cause of lamp failure due to large deformations of lamp components at a specific frequency. Resonance tests can be estimated experimentally using a vibration machine or numerically utilizing finite element analysis software. These methods estimate the resonance of the lamp after the lamp is fabricated or the complete lamp model is created on the CAD software. The objective of this paper is to teach the development of a prediction tool to estimate the resonant frequency of lamps before fabricating the lamp or creating the model on the CAD system. Design of computer experimentation (DOCE) methodology has been utilized to identify the significance level of the parameters involved to estimate the resonant frequency of a lighting system.

CAE tools are utilized within the automotive lighting industry to develop thermal models and thus predict temperature distributions for various lamp components. The ultimate goal of developing CAE models is to accurately predict temperatures for lamp systems at early stages in the design process. A major factor in developing a reliable CAE model is the accurate estimation of thermal parameters such as the convection coefficient. This study investigates the effects of six thermal parameters on automotive lamp temperature. A 2-level design of experimentations (DOE) methodology is utilized to determine the significance level of each parameter on the temperature change of the lens and the housing. A first-order linear response function is generated, using the most significant factors with a confidence level of 95%. It is found that a small alteration in the convection coefficient can change the hot spot temperature prediction of the lens and the reflector by 32% and 25%, respectively.

Certain conditions promote water vapor to condense on available surfaces within an automotive lighting assembly. Certain surfaces are more susceptible to water condensation than others. This is due partially to temperature gradients in the lamp and possibly water vapor concentration gradients. This study demonstrates that humidity gradients exist in an automotive lamp. How humidity gradients affect the likelihood of surface condensation for a particular interior surface of a lamp will also be addressed.

The effect of water vapor transfer from plastic materials commonly used in automotive lighting assemblies can be experimentally measured. This is accomplished by isolating this phenomenon from other mechanisms effecting water vapor concentration in the lamp. Quantifying this effect helps to address design considerations for liquid water and water vapor egress in the lighting assembly. The relevance of the current moisture clearing type test required in the industry is discussed in light of the empirical results for this effect.

Evaluating thermal concerns is often addressed during the automotive lamp design process. The thermocouple device is used frequently for temperature measurements to locate and quantify hotspots that arise in the automotive lamp assembly. This study seeks to review the techniques used for thermocouple temperature measurement. Common techniques are described in detail and evaluated. An experiment coupled with computer simulation is introduced and performed that tests accuracy and compares the methodology and results of the different thermocouple measurement techniques. The technique that most directly measures both inside (exposed to light source) and outside (away from light source) surface temperature is demonstrated to have advantages. Correlation to heat deflection temperature and thermal damage such as warp and metalization blemish (haze) is described.

The FMVSS humidity test, as described in 571.108 S8.7, for forward automotive lamps permits environmental conditions to vary within a given tolerance. Pre-soak conditions of the lamp for the test may vary. The tolerances during the soak portion of the test allow for a +4°C variation (from the initial 38°C environment) and a +10% variation from the initial 90% environment relative humidity. Tolerances during the wind portion of the test allow for a +4°C variation (from the initial 23°C environment), a +10% variation from the initial 30% environment relative humidity, and a -0.153 m/s (-30 ft/min) variation from the initial 1.68 m/s (330 ft/min) airspeed setting. Utilizing a climate control wind tunnel, this study demonstrates that the tolerances on the environmental test conditions will produce substantial test result variation. The discussion emphasizes the best environmental condition to minimize time to clear condensation for a particular automotive lamp.

Automotive lamps are vented to the environment to reduce pressure differentials and provide a pathway to reduce lamp moisture vapor and eliminate condensation. Many venting products are available for use in any lighting application. Price and performance are major considerations in choosing the best vent system. This paper will present the methodology to characterize the moisture vapor diffusion performance of automotive vents. After performance characterization is known, application of the optimal venting product can be identified and design possibilities simplified for the lighting designer.

Thermal performance of automotive lighting must be considered early in the design phase of any lighting program. Several techniques are used to determine if a new design will pass thermal requirements. Many automotive lamps are design from experience, where historical information is used to qualify a design. Quantitative methods for determining lamp thermal performance allow optimization of parameters, which can affect lighting cost. This paper will present a comparison between experimental based modeling and computational fluid dynamics (CFD) approaches for determining the viability of an automotive lamp design.

An eight-channel fiber-optic combustion pressure system is described intended for continuous monitoring and control applications in diesel- and natural gas-engines. The portable control/monitoring unit of the system offers capabilities of real-time data acquisition and triggering from a shaft position or TDC sensors. Several processing functions are offered including calculations of peak pressure (PP), Indicative Mean Pressure (IMEP), and location of peak pressure (LPP). The system allows for 50 kHz, burst mode transfer of multi-sensor data to a PC. OPTRAND's commercially available combustion sensors for 1000 and 3000 psi maximum pressure ranges can interface to the unit with optical patch cables available up to 100 meters in length. The system offers 0.1Hz to 15 kHz frequency response, 1% accuracy at constant temperature, and maximum uncooled sensor housing temperature of 300°C.