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Technical Paper

1D Modeling of AC Refrigerant Loop and Vehicle Cabin to Simulate Soak and Cool Down

Simulation has become an integral part in the design and development of an automotive air-conditioning (AC) system. Simulation is widely used for both system level and component level analyses and are carried out with one-dimensional (1D) and Computational Fluid Dynamics (CFD) tools. This paper describes a 1D approach to model refrigerant loop and vehicle cabin to simulate the soak and cool down analysis. Soak and cool down is one of the important tests that is carried out to test the performance of a heating, ventilation and air-conditioning (HVAC) system of a vehicle. Ability to simulate this cool down cycle is thus very useful. 1D modeling is done for the two-phase flow through the refrigerant loop and air flow across the heat exchangers and cabin with the commercial software AMESim. The model is able to predict refrigerant pressure and temperature inside the loop at different points in the cycle.
Technical Paper


A mathematical simulation of the operation of a compressed-gas airbag system is developed. A system was built and tested, and the analysis is evaluated on the basis of these tests. Included in the study are nonideal gas effects, manifold and diffuser effects, bag stretch, bag leakage, and overpressurization of the passenger compartment. Interaction between a single rigid object and the bag is also considered. A correlation between bag pressure and the force it generates is obtained. This allows the development of an analytic model for determining the motion of a single rigid mass interacting with a dynamically inflating airbag mounted in a moving vehicle. An application of the model to study rebound of the occupant from the airbag is presented.
Technical Paper

A BE Model for the Analysis of the Effects of Seats in the Passenger Compartment Acoustic Behaviour

The aim of this work is to validate a BE numerical methodology to calculate how the acoustic properties of seats can affect the acoustic behaviour of the passenger compartment of a vehicle. An analytical model, based on the Delany and Bazley approach, was implemented in order to simulate the acoustic impedance of the foam-fabric system. This model has been validated with absorption coefficient measurements on a certain number of foam-fabric combinations. The calculated impedance was used as input for a BEM analysis of the interior cavity of a trimmed vehicle. The measured impedance of trimming components as floor carpet, door panels and parcel shelf were included into the cavity model. The acoustic field due to a known source with and without seats was calculated, in the frequency range 20-400 Hz: the calculated FRFs are in good agreement with the measured ones.
Technical Paper

A Basic Study of “Energy-Absorbing” Vehicle Structure and Occupant Restraints by Mathematical Model

Simplified mathematical modeling has been employed to investigate the relationship between automobile forestructure energy absorption and the restraint loads applied to passengers during a 30 mph barrier collision. A two-massmodel was developed and validated to compute restraint loading from a given passenger compartment deceleration. The effect of various deceleration curves, representing forestructure modifications, is reported. A “constant force” restraint system is also evaluated.

A Combined 0D/3D Approach for Comparing Bus Passenger�s Thermal Comfort

In Great Britain (GB) the average person living in urban environments can spend up to 55 minutes per day commuting to work, with one of the most popular methods being by bus. Therefore, it is imperative that the bus operators provide a safe and comfortable indoor environment during transit, ensuring passenger health and for encouraging customers to use their service. A common approach to ensure a thermally comfortable environment is by specifying an internal temperature setpoint that the cabin air must maintain. However, there is a lack of consensus between operators as to which temperature is the most appropriate with setpoints typically ranging from 17-21 �C. Further, there has been minimal research into using thermal comfort metrics to assess whether or not these temperatures will provide thermal satisfaction. This research aims to use a combined 0D/3D approach to compare the thermal comfort level of a seated bus passenger using Fanger�s PMV model.
Technical Paper

A Computational Aeroacoustic Study of Windshield Wiper Influence on Passenger Vehicle Greenhouse Windnoise

This paper presents an approach to numerically simulate greenhouse windnoise. The term “greenhouse windnoise” here describes the sound transferred to the interior through the glass panels of a series vehicle. Different panels, e.g. the windshield or sideglass, are contributing to the overall noise level. Attached parts as mirrors or wipers are affecting the flow around the vehicle and thus the pressure fluctuations which are acting as loads onto the panels. Especially the wiper influence and the effect of different wiper positions onto the windshield contribution is examined and set in context with the overall noise levels and other contributors. In addition, the effect of different flow yaw angles on the windnoise level in general and the wiper contributions in particular are demonstrated. As computational aeroacoustics requires accurate, highly resolved simulation of transient and compressible flow, a Lattice-Boltzmann approach is used.
Technical Paper

A Computational Model to Simulate the Thermal Behaviour of the Passengers Compartment of Vehicles

In this paper a computational model developed with the objective of simulating the thermal behaviour of the passengers' compartment of vehicles is presented. The model is based on the space-integral energy balance equations for the air inside the compartment and for the main vehicle bodies and surfaces. It can solve two kinds of problems. In the first one, calculates the heat stress that the air conditioning or heating system must equilibrate, in order to satisfy predefined permanent regimen project specifications. In the second one, once imposed a particular air conditioning system and given the ambient conditions, it computes the different temperatures and heat fluxes either in transient or steady regimens. The validation of this model was done with a railway car, in a summer situation, when it was immobilized and running. The model reproduced well the experimentally determined temperature and heat fluxes evolutions.
Technical Paper

A Consideration of Vehicle's Door Shutting Performance

Many papers have mentioned, in passing, a phenomena that is known as “airtightness”, which is one factor that hinders automobile doors from closing. It also causes the eardrums of any passengers in the vehicle to be temporarily pressurized when the door is closed. However, few documents have considered this phenomena in detail. In this paper, we investigate the magnitude of “airtightness” as it affects ear pressure and examine its relationship to such factors as the volume of the passenger compartment, door's opening area and its inertial moment. Finally, we utilized estimation methods to predict its influence on the force required to close the door and the amount of the resultant air draft.
Technical Paper

A Control System for Maintaining Passenger Cabin Air Quality

This paper presents a control methodology to maintain vehicle cabin air quality within desirable levels, giving particular attention to gaseous contaminants carbon dioxide (CO2) and carbon monoxide (CO). The CO2 is generated by the occupant exhalation while the CO is assumed to be ingested with the incoming outside air. The system is able to detect and improve cabin air quality by controlling the recirculation flap of the ventilation system to control the amount of outside air intake. The methodology is demonstrated in the laboratory using controlled experiments with a production level automotive HVAC module. The results indicated that the designed control system can work automatically and control the CO and CO2 gas concentrations within acceptable levels when operating in an environment of near zero ppm CO and 600 ppm CO2 concentrations, respectively.
Technical Paper

A DFSS Approach Study on the Effects of Vehicle Cabin Properties on HVAC System’s Cool Down Performance Using 1D Simulation

Due to the increase in heat wave across the globe, maintaining the thermal comfort of passengers in a vehicle is becoming a challenge. Considering global warming, there is a need to shift towards greener refrigerants which in itself causes a marginal degradation in the Heating Ventilation and Air Conditioning (HVAC) system performance. Also the emission norms and regulations demanding for a smaller engine if not for a hybrid or electric vehicle, there is a need for optimally designing the HVAC system since it is directly related with the efficiency of the vehicle and also plays a vital role in the customer comfort. Hence maintaining the comfort level of the passengers needs further exploration and challenging rather than optimizing the HVAC system alone in the competitive market. Conventionally for given system where we need sufficient cooling, the capacity of the components can be increased in order to meet the customer comfort.
Technical Paper

A Desktop Procedure for Measuring the Transmission Loss of Automotive Door Seals

Due the increasing concern with the acoustic environment within automotive vehicles, there is an interest in measuring the acoustical properties of automotive door seals. These systems play an important role in blocking external noise sources, such as aerodynamic noise and tire noise, from entering the passenger compartment. Thus, it is important to be able to conveniently measure their acoustic performance. Previous methods of measuring the ability of seals to block sound required the use of either a reverberation chamber, or a wind tunnel with a special purpose chamber attached to it. That is, these methods required the use of large and expensive facilities. A simpler and more economical desktop procedure is thus needed to allow easy and fast acoustic measurement of automotive door seals.
Technical Paper

A Dynamic Computer-Aided Engineering Model for Automobile Climate Control System Simulation and Application Part II: Passenger Compartment Simulation and Applications

A Computer-Aided Engineering (CAE) model for automobile climate control system is presented to provide engineers with an cost effective analysis tool for designing, developing, and optimizing the vehicle interior climate. It is the objective of this paper to develop a mathematical model which predicts the lumped temperature and lumped humidity variations inside the passenger compartment under design and operating conditions. The transient nature of the passenger cabin temperature, average interior mass temperature, and humidity are modeled using three coupled non-linear ordinary differential equations based on mass and energy balances. These equations are then solved by a fourth-order Runge-Kutta method with adaptive step size control.
Technical Paper

A Free-Flight Headform Impact Device for Evaluating the Energy- Absorption Characteristics of Vehicle Interiors

This paper reports on the design, development, and use of a test rig that enables the analysis of the aggressivity of vehicle interiors to the heads of occupants. The equipment comprises a pneumatically controlled free-flight headform device. It can be positioned inside the passenger compartment of any passenger car via any normal window or door aperture. The device fires a simulated headform prescribed in SAE J984 at speeds for 10 to 30 mph. The enormous degree of flexibility in positioning enables impacts to be conducted on almost any part of the vehicle interior. Currently, energy-absorbing characteristics of the interior of passenger cars are assessed using drop rigs or pendulums, which necessitate the dismantling of the vehicle body. This has implications for representativeness in terms of the validity of the stiffness characteristics of the section of the vehicle being tested. The results of testing standard specimens, using all three test devices, are presented and discussed.
Technical Paper

A Front Rail Design for Efficient Crush Energy Absorption

Although there was a safety awareness from the earliest days of the automobile, systematic approaches to designing for safety became more widespread after 1950 when large numbers of vehicles came into use in both the United States and Europe, and governments in both continents undertook a widespread highway development. Industry response to safety objectives and also to government regulation has produced a large number of safety enhancing engineering developments, including radial tires, disc brakes, anti-lock brakes, improved vehicle lighting systems, better highway sign support poles, padded instrument panels, better windshield retention systems, collapsible hood structures, accident sensitive fuel pump shut-off valves, and other items. A significant development was the design of the energy absorbing front structures.
Technical Paper

A General Discussion of Flammability as Related to the Automotive Industry and MVSS 302

The Motor Vehicle Safety Standard 302 becomes effective September 1, 1972, establishing a 4 ipm horizontal burn rate for materials used in the passenger compartment of motor vehicles. Limitations of the standard are touched upon. Conventional approaches to impart fire retardance to vinyls,polyolefins, urethane foams, ABS, polyester, and carpeting are reviewed. Potential problems associated with each of the approaches include fogging, dripping, staining, low-temperature flexibility, durability, effect on physical properties, and cost.
Technical Paper

A Mathematical Model of the Chrysler Hyge Impact Simulator

The Chrysler Hyge impact simulator permits full-scale laboratory simulation of the deceleration experienced by an automobile passenger compartment during impact. The need to duplicate a great variety of deceleration pulse shapes necessitates a large number of operating parameters. Unfortunately, this large number of parameters precludes easy determination of the relationships between parameter selections and desired pulse shapes. This paper describes the development of a mathematical model and digital computer program used by the Chrysler Engineering Office to predict the response of the impact simulator for a given set of parameters. The principle elements of the model deal with unsteady compressible gas flow and the effect of the resulting forces on the sled motion. The modeling of the metering pin is of particular importance, since the characteristic shape of the acceleration pulse is limited by the pin contour.
Technical Paper

A Method To Evaluate Passenger Thermal Comfort In Automobile Air Conditioning Systems

In present day passenger cars, Mobile Air Conditioning (MAC) system is one of the essential features due to rise in overall ambient temperatures and comfort expectation of customers. During the development of MAC system, the focus is on cooling capacity of system for maintaining in-cabin temperatures. However, parameters like solar radiation, air velocities at occupant, relative humidity, metabolic rate and clothing of occupants also influence occupant’s thermal comfort and normally not considered in design of the MAC system. Subjective method is used to evaluate thermal comfort inside vehicle cabin which depends mainly on human psychology. To better understand the effect and minimize the human psychological factors a large sample of people are required. That process of evaluating the comfort inside the vehicle cabin is not only time consuming but also impractical.
Technical Paper

A Methodology for Developing Interior Trim Panels to Comply with the New FMVSS No. 201 Legislation

During driving, automobile and light truck occupants interface with almost all the components in the passenger compartment. These components are expected to provide not only ease of access to controls and comfort to the occupants, but also the necessary protection to decrease the likelihood of injuries during accidents. The passing of the revised Federal Motor Vehicle Safety Standard (FMVSS) No 201 is aimed at improving the overall safety of vehicle occupants during impact situations Amendments are specifically focused at improving the protection provided by the upper compartment components, i e, header, rail, pillar and roof trim panels, to the occupants' heads impacting at high velocities. The present paper reviews the requirements established by the revised federal legislation and the design and material options to meet the requirements, and describes a systematic approach for designing and engineering trim panels for head impact protection
Technical Paper

A Mobile System to Measure Toxicity Levels in Crew Compartments from Live Fire Missions

As part of the Army Test and Evaluation Command (ATEC) the Metrology and Simulation Division at the U.S. Army Yuma Proving Ground (USAYPG) has the mission to measure and record the detrimental effects of firing conventional and experimental munitions on gun crews under live fire testing. In order to provide a safer environment for soldiers and to comply with national and international military specifications, the Measurements and Simulation Branch of the Metrology and Simulation Division at The U.S. Army Yuma Proving Ground has developed a mobile system to quantitatively analyze and record the level of toxicity present in the crew compartment of a variety of military vehicles. The system is housed in a medium sized van that is self-contained with the exception of its power source.