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Typical belt-driven Mobile Air-Conditioning (MAC) compressors require durable seals between a rotating driveshaft and stationary casing in addition to casing and hose connection O-ring seals. This paper explores the experiential and theoretical relationships of HFC134a seal design and materials and also suggests possible improvements. Testing revealed that shaft and O-ring permeation comprised a large part of the total leak rate of HFC134a MAC compressors during static-state leak-rate measurements. Furthermore, testing and Taguchi statistical analysis methods clarified equations concerning permeation area, distance and leak rate. Resulting design and material improvements reduced compressor HFC134a Leak Flow Rates (LFR) by approximately fifty percent.

A two-channel LDV system is used to obtain accurate airflow measurements around scale models of passenger cars in wind tunnel tests at the Nissan Research Center. A 2-watt argon-ion laser is employed as the light source. The main optical unit and probe head are connected by optical fibers. The probe head consists of a compact LDV probe with a beam expander and focusing lens with a long focal length can be easily traversed. A new type of signal processor, performing a digital autocorrelation function, is employed to process the Doppler signals. Mean airflow velocities and turbulence intensities are calculated by a micro computer to evaluate the flow fields. The results of preliminary experiments conducted with this system indicate that the system is not only capable of measuring the mean velocity components, including reverse flow, it can also provide accurate estimation of turbulence components.

For both notchback-type and fastback-type models, it has been found that critical geometries which increase the aerodynamic drag exist, and the time-averaged wake patterns basically consist of an arch vortex behind the rear window and trailing vortices in the wake. The unsteady characteristics of the wake seem to be directly related to aerodynamic drag. However, the unsteady characteristics of these wake patterns for notchback and fastback cars were not clear. The purpose of present paper is to clarify these phenomena. We try to analyze experimentally the unsteady characteristics by measuring the velocity fluctuations in the wake, the pressure fluctuations on the trunk deck and the drag-force fluctuations acting on the model. At the same time, the analysis of the numerical simulation was made by using the same numerical model as the experimental model. The computed flow visualization behind the rear window showed a fluctuating arch vortex.

Notchback models generally have more complicated flow patterns than box models. This leads to intricate infuluence of rear geometry of Notchback on aerodynamic drag. Therefore, based on understanding of wake structure, flow phenomena for reducing the drag can be analyzed. This paper analyzes the influence of geometry of rear portion on the drag by means of 1/5 scale notchback models. For fastback models, at certain critical angle of the rear window the drag shows a sharp peak. For notchback models, it is found that some combination of the angle of rear window and the height of trunk deck shows simillar maximum in the drag. Moreover, the flow visualization and the detailed measurements of velocity fluctuation clarify typical vortex patterns of wake, which are an arch-type vortex behind the rear window and the trailing vortex behind the trunk deck.

The wind-noise-level in the cabin of a vehicle depends on the magnitude of the aerodynamically generated noise and noise isolation characteristics. Therefore, one good way to reduce the wind-noise-level in the cabin is to minimise the acoustic noise itself generated by the turbulent air flow around the vehicle at high speed cruising. This paper describes the relation between the turbulent flow and the aerodynamic noise as well as how to estimate the magnitude of aerodynamic noise, especially around A-pillar of a production vehicle. First, the flow visualization and the detailed measurements of flow clarify the vortex structure generated around A-pillar and side window. Secondly, sound pressure fluctuations measured on the side window surface are discussed in relation to the vortex structure. Lastly, in order to estimate the order of the magnitude of aerodynamic noise we, propose physical parameters given by approximating the solution of Lighthill's equation.

Making use of spark-plug-washer type cylinder pressure sensors and a high-performance 16-bit microprocessor, the authors have developed a new control system (Nissan ECCS) of ignition timing for gasoline engine. Use of this system results in effective control, enabling each engine to deliver maximum torque and minimum fuel consumption at all conditions, regardless of changes in environmental conditions, etc.