Car Cabin Research Articles

Investigation of performance and energy cost of automobile air-conditioner using alternative refrigerants based on thermal comfort using various cooling seats

During hot summer days, the rapid rise in temperature inside a vehicle and the direct transmission of radiant energy cause significant discomfort to drivers, and the driving distance of an electric vehicle is greatly reduced due to the operation of the air-conditioner. Therefore, it is essential to provide a thermally comfortable environment to the driver and reduce the energy consumption of air-conditioners in the EV. This study investigated the thermal comfort of the driver according to the use of a basic seat (BSS), ventilation seat (VLS), and cold-water seat (CWS) in the car cabin under summer condition. Also, based on thermal comfort, the system performance and energy cost of an automobile air-conditioner using various alternative refrigerants were analyzed and compared. As a result, when the CWS was used, the stress index of subjects was the lowest in the PPG, and the relative β/α of the subjects decreased in the EEG. In addition, the results of the subjective questionnaires and bio-signal measurement showed the most thermally comfortable when using the CWS. The COPs of the air-conditioner using R134a, R1234yf, R1234ze(E), and R152a increased by 19.3 %, 18.9 %, 19.0 %, and 19.3 %, respectively, and annual energy consumption of the air-conditioner decreased. In addition, in the five European countries, the annual electric charging costs and annual eq-CO2 emissions for using the CWS showed the most significant reduction in Germany. Therefore, it was confirmed that using CWS can provide a thermally comfortable environment for drivers inside the vehicle during summer and effectively reduce power consumption used for air conditioning in EVs.

A Study of Passenger Car Cabin Pre-Ventilation under the Sun

With the increasing intelligence of automobiles, vehicle pre-ventilation can be better controlled. In summer, cars parked in the open air are directly exposed to sunlight; thus, a high-temperature environment is formed in the occupant cabin, which seriously affects the passengers and driver’s riding and driving experience. Meanwhile, lowering the temperature of the passenger compartment from a very high temperature to a comfortable temperature consumes a lot of energy. Therefore, it is increasingly important to study the pre-ventilation of the cabin in order to improve the thermal comfort of the occupant cabin and reduce energy consumption. In this paper, a new theoretical model of a cabin temperature control system is proposed. To support the theoretical model, an outdoor parking temperature rise test was carried out. Environmental parameters were obtained and used as the boundary conditions of the subsequent simulation. Based on the mechanism of the cabin temperature rise, the convective heat transfer coefficient on the body surface, the equivalent heat transfer model of the cabin, the solar radiation model and the physical properties of the air, a computational simulation of the temperature rise in the occupant cabin was carried out, and a simulation of the temperature rise in the occupant cabin exposure was studied. The simulation results were compared with the experimental findings to verify the accuracy of the simulation, which provided a reference for the design of the pre-cooling function of the occupant cabin. This study revealed that the pre-ventilation model developed reduces the vehicle cabin temperature through optimal control of air supply volumes and air supply angles. Furthermore, the developed pre-ventilation model is capable of reducing energy consumption, thereby reducing greenhouse gas emissions.

A Diffusion-Inertia Model for the simulation of particulate pollutants dynamics inside a car cabin

Simulations of particle pollutants dynamics inside a car cabin were performed using the Diffusion-Inertia Model (DIM) coupled to the RANS (Reynolds-averaged Navier–Stokes equations) k−ω SST turbulence model for single-phase flow. The DIM model has been implemented in a commercial CFD solver and then validated on some reference flow configurations. The validation included particle dispersion in ventilated chambers of one and two compartments, particle deposition in circular 90°bends, and particle-laden jet flow. The DIM model has shown interesting capabilities in taking into account various transport mechanisms such as the transport by the mean flow, gravitational settling, centrifugal effect due to flow streamline curvatures, molecular and turbulent diffusion, and also turbophoresis transport mechanism due to turbulent energy gradients. Moreover, the application of the DIM model to the simulation of solid particles, characterizing particulate pollutants, has revealed characteristic dynamics that is mainly determined by the airflow topology, particularly for ultrafine and fine particles (0.1, 1 and 2.5μm). Inertial effects were found to become significant only for coarse particles (5 and 10μm), as the impact of gravitational and centrifugal effects gradually becomes more noticeable. Furthermore, the risk of exposure to high levels of particulate pollutants has been clearly established when considering the presence of occupants inside the vehicle cabin. These concentration levels are linked in particular to the complex interaction between occupants’ heads and the internal flow, as well as to the tendency of particles to accumulate in the upper part of the cabin and to the rapid homogenization observed throughout the whole interior volume.

Local active control of road noise with door loudspeakers in a car cabin

Active control of road noise in car cabins has received much attention in recent years and it has been well known that local quiet zones can be created with headrest loudspeakers. The local control performance achieved with door loudspeakers is investigated in this manuscript based on the measurements in a car cabin, and it is compared with that achieved with two headrest speakers. The noise reduction performance at error microphones, the upper limit frequency of effective control, as well as the size of the quiet zone are investigated in detail. The difficulties and challenges of using the door loudspeakers for local control are discussed.

Improving the acoustic contrast control performance in car cabins

The car cabin is an enclosure where personal audio is very important because different occupants may have individual listening requirements. Potential approaches to improve the acoustic contrast control performance in enclosures are discussed in this paper, including the configuration of loudspeakers and the sound absorption of sidewalls. The effect of the number of loudspeakers on the acoustic contrast control performance is first investigated, and the locations of a fixed number of loudspeakers are then optimized to maximize the acoustic contrast achieved with the system. The sound absorption of sidewalls also has an effect on the acoustic contrast control performance and it is discussed in detail. The simulations are based on the acoustic transfer functions obtained with a finite element model of a car cabin. The findings in this paper may serve as a guide to future designs of personal audio systems in car cabins.

A novel design of heating system using phase change material for passenger car cabin in cold starting conditions

In this paper, the use of exhaust waste heat energy stored in a latent heat thermal energy storage (LHTES) system for cabin heating of a passenger car at cold climate conditions was investigated by experimental and computational fluid dynamics (CFD). A liquid circulation system was installed for this purpose, consisting of two heat exchangers, one in the passenger car's rear compartment and the other in which the phase change material (PCM) in the LHTES system was stored. Commercial RT55 paraffin wax was used as PCM, and tap water was used as heat transfer fluid (HTF). Experimental and CFD analysis studies, which started at 283 K cabin interior temperature, were continued for 1500 sec (25 min). Before the experiments, the cabin interior of the passenger car was cooled up to 283 K with the air conditioning system, and the air conditioning system was kept on at a setting where the cabin interior temperature would remain constant at 283 K during the experiments. Thus, real cold climate conditions were provided for the experimental study. As a result, it has been observed that with the new cabin heating system, thermal comfort conditions for people are provided after the first five minutes, and this temperature can be maintained throughout the experiment. So much so that the cabin temperature increased from 283 K to 295 K in five minutes and reached approximately 297 K at the end of the experiment with a slow rate of increase. Furthermore, the difference in RT55 temperatures between the experimental and CFD analysis results is less than 3% during the cabin interior heating period.

Reverberation time control by acoustic metamaterials in a small room

In recent years, metamaterials have gained considerable attention as a promising material technology due to their unique properties and customizable design, distinguishing them from traditional materials. This article delves into the value of acoustic metamaterials in room acoustics, particularly in small room acoustics that poses specific challenges due to their significant cavity resonant nature. Small rooms usually exhibit an inhomogeneous frequency response spectrum, requiring higher wall absorption with specific spectrum to achieve a uniform acoustic environment, i.e., a constant reverberation time over a wide audible frequency band. To tackle this issue, we developed a design that simultaneously incorporates numerous subwavelength acoustic resonators at different frequencies to achieve customized broadband absorption for the walls of a specific example room. The on-site experimental measurements agree well with the numerical predictions, attesting to the robustness of the design and method. The proposed method of reverse-engineering metamaterials by targeting specific acoustic requirements has broad applicability and unique advantages in small confined spaces with high acoustic requirements, such as recording studios, listening rooms, and car cabins.

An experimental study on the upper limit frequency of global active noise control in car cabins

In this case study, the upper limit frequency for global noise control in car cabins is investigated with numerical simulations, and experimental results of global control are presented for the first time. To simulate the complicated noise field in a running car, a 1.90 m × 1.50 m × 1.10 m rectangular enclosure, which is approximately the size of a typical car is used with point monopoles evenly distributed near the boundaries generating the primary sound field. Besides verifying the fact that the upper limit frequency of effective control increases with the number of secondary sources, a formula is proposed in this paper to estimate the number of secondary sources required to achieve global control up to a certain frequency. The simulations are carried out in the time domain based on the transfer functions measured between the secondary loudspeakers and 40 evaluation points evenly distributed in a typical car, which show that the upper limit frequency of 3 dB global control is about 200 Hz while using 4 secondary sources and it can be improved to 315 Hz with 7 secondary sources. An active noise control system is realized with 16 accelerometers picking up vibration reference signals and 4 or 7 loudspeakers as secondary sources, and the real time test results in the car running at 50 km/h on a typical asphalt road demonstrated the validity of the findings in numerical simulations.

Experimental Study of the TVOC Distribution in a Car Cabin

The vehicle in-cabin is subject to several types of pollutants infiltrating from the outdoors or emitted directly inside it, such as Volatile Organic Compounds (VOCs). The concentration of TVOC (total volatile organic compounds) is the result of the emission from different equipment surfaces that compose the car cabin. In the present study, the experimental characterization of TVOC emission from the interior surfaces of a car cabin is discussed by considering the influence of two parameters: the temperature and ventilation modes. A measurement location grid was used to measure TVOC’s emissions from 267 points on all surfaces of the car’s interior equipment. Three different temperatures and two ventilation modes (recirculation and outdoor air) were investigated. The results indicate that the concentration of TVOC increases with the temperature inside the cabin with a contribution that varies with the type of cabin equipment including the dashboard, center console, seats, and carpets. On the other hand, the concentration distributions of TVOC showed relative differences of 10–13% and 2–5% for surface and volumetric measurements, respectively. This implies no preferential positioning of the in-cabin probe for TVOC volumetric concentration measurements. In addition, the recirculation ventilation mode results in a higher accumulation of TVOC; therefore, higher concentrations are measured.

Risk assessment of the asthma-induction potential of substances in spray products for car cabin detailing – based on EU’s Chemical Agents Directive, using harmonised classifications and quantitative structure-activity relationship (QSAR)

Exposure to spray-formulated products for car cabin detailing is a potential risk for asthma induction. With a focus on the asthma-related endpoints sensitisation and irritation of the lungs, we performed an occupational risk assessment based on requirements in the EU Chemical Agents Directive. We identified 71 such spray products available in Denmark. We identified ingredient substances in safety data sheets and screened for harmonised classifications of respiratory sensitisation and airway irritation. For respiratory sensitisation, we also applied quantitative structure-activity relationship (QSAR). We modelled the exposure during 15 min of work inside a car cabin, and determined the risk ratio of the products by further applying occupational exposure limits – mainly derived no-effect levels (DNELs) from the European Chemicals Agency (ECHA) set on respiratory irritation. Four substances had a harmonised classification for respiratory irritation (bronopol, 2-phenoxyethanol, 2-methoxypropanol, and butan-1-ol). Seven substances were positive in the QSAR model for respiratory sensitisation (monoethanolamine, bronopol, glycerol, methyl salicylate, benzoic acid, ammonium benzoate, and sodium benzoate). Two vinyl treatment products had a risk ratio > 1 based on the level of sodium benzoate and its DNEL set on respiratory irritation. Two products had risk ratios of 0.69 and 0.73, respectively, based on 2-methyl-2 H-isothiazol-3-one and its acute DNEL set on respiratory irritation. In conclusion, 10 substances that may pose a risk for asthma induction were identified in the products. Two of the 71 products had a risk ratio > 1, meaning they may pose an asthma-induction risk in the modelled exposure scenario and using respiratory irritation DNELs from ECHA.

Active vibration control for reduction of interior noise caused by R-MDPS of electric power steering in electric vehicle

This paper presents a novel active vibration control (AVC) system for a motor driven power steering (MDPS) system to reduce interior noise in an electric vehicle. The novel control algorithm used for the AVC system is developed based on selection of two reference signals. One is the frequency modulation signal using the rotation speed of motor shaft of MDPS the other one is the band passed signal of acceleration measured on the major path structure identified by the blocked transfer path (BF-TPA). In addition, the piezo stack actuator is used for generation of control force of the AVC system in the frequency over 400 Hz. An MDPS system uses electronic power steering. An MDPS system attached to the rack gear of power steering system is called an R-MDPS. The vibration generated by the R-MDPS is transmitted to the car body through mounts attached onto the car subframe. Panel vibrations of car body are sources of vibroacoustic noise generated inside the car cabin. This vibracoustic noise is a structure-borne noise and causes passenger annoyance. The frequencies of the structure-borne noise measured inside the car cabin are 460 Hz and 920 Hz, which are the rotating frequency of the R-MDPS motor shaft and the second-order harmonic of the rotating speed of the motor shaft. To directly reduce the interior noise inside the car cabin, active noise control (ANC) has been used for the active cancellation of noises with frequencies less than 400 Hz. However, because the frequency of interior noise generated by the operation of the R-MDPS is higher than 400 Hz, AVC was employed in this study for the active cancellation of vibrations transmitted to the car body through the subframe mounts of the car. For application of AVC to the test car, the control force should be known. Therefore, the actuator for generating the control force should be inserted in the mount between the subframe and R-MDPS system. Installing the actuator in the test car is challenging because of the geometry limit of commercial cars. Hence, a test jig composed of an R-MDPS system and the subframe of the test car was developed and set up in the laboratory to study the applicability of AVC to R-MDPS. All investigations of AVC were performed using the test jig in the laboratory. The proposed method was successfully applied to the active cancellation of vibration at a target point on the subframe.

Noise Metrics and Subjective Assessment of Automotive HVAC Systems

HVAC systems are of critical importance in ensuring passengers' thermal comfort inside the car cabin as well as safety requirements for defogging functions. These systems involve various components and subcomponents such as blowers, thermal exchangers or actuators, with a wide range of well-known technologies and also new ones on recently introduced innovative products. Currently, within established electrification trends worldwide, the HVAC system is becoming the most important embedded system that can induce major contribution of noise and vibration. These NVH issues can emerge through different transfer paths inside the car cabin possibly causing significant discomfort to passengers. During developments, the NVH issues are mastered and contained by both suppliers according to internal requirements and OEMs according to specifications. However, OEM specifications are mainly defined by overall noise levels and improvements over the years are generally consisting of reducing these specified levels. Furthermore, some HVAC NVH issues may not be well detected when using regular NVH metrics. This raises concerns about the limitations of the regularly used metrics in ensuring specification compliance and, above all, in depicting a subjective assessment at component level. Throughout a statistical analysis of HVAC systems population, this paper first focuses on the discrepancies between the data provided by traditional NVH metrics and subjective evaluations. Then, a deeper analysis involving psychoacoustic metrics provides a relevance overview of the applied metrics depending on the encountered issues and compared to a subjective assessment. Finally, from a responsibility perspective, these findings raise questions about the relevance of regular metrics used by OEMs and the right way to handle HVAC NVH topics nowadays.

Impact of different ventilation conditions on tobacco smoke-associated particulate matter emissions in a car cabin using the TAPaC platform

Despite antagonizing attempts from the tobacco industry, passive inhalation of tobacco smoke is known to be cancerogenic and toxic to human health for decades. Nonetheless, millions of non-smoking adults and children are still victims of second-hand smoke. Accumulation of particulate matter (PM) in confined spaces such as the car are particularly harmful due to high concentrations. We here aimed to analyze the specific effects of ventilation conditions in the setting of a car. By the use of the measuring platform TAPaC (tobacco-associated particulate matter emissions inside a car cabin), 3R4F reference cigarettes, Marlboro red, and Marlboro gold were smoked in a car interior with a volume of 3.709 m3. Seven different ventilation conditions (C1–C7) were analyzed. Under C1, all windows were closed. Under C2–C7, the car ventilation was turned on power level 2/4 with the air directed towards the windshield. Only the passenger side window was opened, where an outer placed fan could create an airstream speed of 15.9–17.4 km/h at one meter distance to simulate a driving car. C2: Window 10 cm opened. C3: Window 10 cm opened with the fan turned on. C4: Window half-opened. C5: Window half-opened with the fan turned on. C6: Window fully opened. C7: Window fully opened with the fan turned on. Cigarettes were remotely smoked by an automatic environmental tobacco smoke emitter and a cigarette smoking device. Depending on the ventilation condition the cigarettes emitted different mean PM concentrations after 10 min under condition C1 (PM10: 1272–1697 µg/m3, PM2.5: 1253–1659 µg/m3, PM1: 964–1263 µg/m3) under C2, C4, and C6 (PM10: 68.7–196.2 µg/m3, PM2.5: 68.2–194.7 µg/m3, PM1: 66.1–183.8 µg/m3) C3, C5, and C7 (PM10: 73.7–139 µg/m3, PM2.5: 72–137.9 µg/m3, PM1:68.9–131.9 µg/m3). Vehicle ventilation is insufficient to protect passengers from toxic second-hand smoke completely. Brand-specific variations of tobacco ingredients and mixtures markedly influence PM emissions under ventilation conditions. The most efficient ventilation mode to reduce PM exposure was achieved by opening the passenger´s window 10 cm and turning the onboard ventilation on power level 2/4. In-vehicle smoking should be banned to preserve innocent risk groups (e.g., children) from harm.

Experimental Characterization of the Airflow within a Car Cabin

The ventilation flow in a car cabin has been experimentally investigated. The study has been carried out in a car commercially available, by testing one ventilation mode (panel-vent mode) at one fan strength (level 3 of the 4 available) with fresh air intake (without any re-circulation). The flow velocity at the exit of the vents has been measured using a 5-hole pressure probe. The flow velocity fields inside the car cabin have been measured by particle image velocimetry (PIV) in three longitudinal sections: (i) the car centre plane, including both the front and rear area; (ii) the driver’s seat centre plane, only in the front area; (iii) the passenger’s seat centre plane, only in the front area. At these longitudinal planes, the time-average flow velocity is presented and discussed. The experimental results provide new insights in the ventilation flow in a car cabin.

Effect of a Parked Car Orientation on a Temperature Distribution and Cooling Load Calculation: Experimental Study

When a vehicle is left parked in the sun for an extended period, the gathered heat causes damage to several interiors within the cabin and causes discomfort for people and animals left inside the car. In the present work, the effect of the orientation of a parked white minibus on temperature distribution and cooling load calculation is studied experimentally in an open environment. Two different cases were studied facing south and facing east. For several hours, the temperature inside the car cabin had been monitored and measured at five separate locations. The cooling load calculations are carried out based on the experimental measurements. The results show that the overheating of parked cars always happens as a result of the radiation load especially when a car has a large surface glass area. Also, the ambient load is directly proportional to the ambient temperature, and the total load related directly to radiation load reaches the maximum value of 2358.1 W at 3:00 pm for 1st case and 2118.3 W at 11:00 am for 2nd case which shows an increase of 11.32 %. Thus, these results emphasized the fact that the orientation of the parked car may considerably affect the temperature distribution and the cooling load of the car cabin. Also, the study may be considered an essential step in designing any assisted ventilation or auxiliary air conditioning system that may enhance the car cabin conditions even while the car’s engine was off (parked automobile).

Automotive cabin vent: Comparison of RANS and LES approaches with analytical-empirical equations and their validation with experiments using Hot-Wire Anemometry

The velocity field downstream of an automotive vent is one of the key parameters of passenger comfort. Two theoretical approaches (using analytical-empirical equations, and based on computational fluid dynamics) were applied to calculate the velocity of a jet emerging from a real rectangular benchmark ventilation outlet with adjustable blades. The computational simulations were performed by solving the Reynolds-averaged Navier–Stokes equations (RANS) with the realizable k-ε turbulence model and by Large Eddy Simulation (LES). The results were validated by experimental data acquired by constant temperature anemometry (CTA). The validation comprised a comparison of axial velocity decay, scalar velocity field, angles of jet inclination, and profiles of velocity and turbulence intensity.The study was performed for the isothermal free jet and attached jet, where surrounding walls simulated confinement in a car cabin. The analytical empirical equation by Rajaratnam can be successfully used also to determine the throw of the jet, which is favourable, especially in light of the fact that both computational methods were not very accurate in velocity decay predictions. Root mean square errors for the free jet, and attached jet (expressed for calculations made according to Rajaratnam, and by LES and RANS with respect to the experimentally measured values) were 0.50, 0.85, 0.87 m s−1, and 0.52, 0.30, 0.65 m s−1, respectively. The LES method was more accurate than RANS in predicting the velocity profiles. The average percentage error of LES, and RANS is 6.3%, and 17.4%, respectively however, the calculation time was almost 27 times higher for LES.

Assessment of Bioaerosols and Metal Contaminants in Car Cabin Filters Dust of Lahore, Pakistan

Assessment of Bioaerosols and Metal Contaminants in Car Cabin Filters Dust of Lahore, Pakistan

On-board measurements using two successive vehicles to assess in-cabin concentrations of on-road pollutants

Gaseous and particulate pollutants are produced in large quantities from road vehicles. These traffic-related air pollutants can infiltrate the car-cabins exposing drivers and passengers to toxic substances with serious adverse health effects. The infiltration process depends on many parameters, those from outside of the vehicle (e.g. traffic intensity, meteorology, road type) and those depending on the vehicle itself such as the ventilation and/or the vehicle speed/age. In the present study, we undertook on-road measurements to assess the impact of ventilation and vehicles spacing (proximity effect) on in-cabin to on-road (I/O) concentration ratios of nitrogen oxides (NOx) and ultrafine particles (UFP). The novelty of the present work is that two successive vehicles have been used to circumvent the influence of the emissions of the upstream vehicle on the downstream test vehicle. We show that the distance to the upstream vehicle influences significantly the (I/O) ratios. Overall, the results show that car cabin is less polluted when the ventilation is set to recirculation mode and keeping a distance to the upstream car corresponding to twice its height in non-idle conditions.

Engine Order Cancelation in a super sports car cabin

Active noise control (ANC) has been used in several systems to improve acoustic performance while avoiding increases in the size and weight required by passive noise control solutions. This paper considers an ANC application aimed at controlling the sound field in the cabin of a supersports car with a naturally aspirated engine. This work studies the performance of a system that employs microphones and loudspeakers in the car cabin and uses a reference signal obtained from CANbus data. The controller exploits a multichannel, multi-order Fx-LMS algorithm to control the sound only in the region surrounding the driver's ears. Due to the nature of the car, this ANC application provides an interesting and challenging case study due to the rapidly changing acoustic excitation provided by the engine. The paper therefore describes a system for noise reduction, focusing on engine order reduction, aiming at achieving control during the most representative manoeuvre known as the "Wide-Open Throttle" (WOT). The investigated controller - acting locally and only on some orders simultaneously - shows good sound attenuation over the entire spectrum, with peaks of reduction exceeding 10 dB, and achieving a 5% overall decrease in the loudness, which is calculated according to ISO 532-1.

On the application of statistical turbulence models to the simulation of airflow inside a car cabin

Computational fluid dynamics simulations of airflow inside a full-scale passenger car cabin are performed using the Reynolds averaged Navier–Stokes equations. The performance of a range of turbulence models is examined by reference to experimental results of the streamwise mean velocity and turbulence intensity profiles, obtained using the hot-wire anemometry technique at different locations inside the car cabin. The models include three linear eddy-viscosity-based variants, namely, the realizable k–ε, the renormalization group k–ε, and the shear-stress transport k–ω models. The baseline Reynolds stress model (BSL-RSM), a second-moment-closure variant, and an Explicit Algebraic Reynolds Stress Model (BSL-EARSM) are also investigated. Visualization of velocity vectors and streamlines in different longitudinal planes shows a similar airflow pattern. The flow topology is mainly characterized by jet flows developing from the dashboard air vents and extending to the back-seats compartment resulting in a large vortex structure. Additionally, a comparison between numerical and experimental results shows a relatively good agreement of the mean velocity profiles. However, all models exhibit some limitations in predicting the correct level of turbulence intensity. Moreover, the realizability of the modeled Reynolds stresses and the structure of turbulence are analyzed based on the anisotropy invariant mapping approach. All models reveal a few amounts of non-realizable solutions. The linear eddy-viscosity-based models return a prevailing isotropic turbulence state, while the BSL-RSM and the BSL-EARSM models display pronounced anisotropic turbulence states.