Search Results

As part of the launch of the refrigerant R-1234yf there were a number of studies done regarding the ignition behavior of this new refrigerant in passenger cars. These tests were conducted by a number of automobile manufacturers, component suppliers, and the refrigerant supplier under laboratory conditions at the component and vehicle level. In November 2009 the international automotive industry concluded that the R-1234yf can be used safely in automotive air conditioning systems. Further tests were conducted by different automobile manufacturers, suppliers, and the refrigerant supplier under various laboratory and vehicle operation conditions means hot surfaces in the engine compartment. A number of vehicle manufactures have conducted full vehicle crash tests.

The interior sound quality of passenger cars has a big impact on the perceived comfort of the vehicle. With today's direct-injection diesel engines this fact gains importance, since the customers are more and more attracted by them due to their low fuel consumption and their good driving performance. In the course of the development of diesel technology, the typical impulsive noise of diesel combustion engines (the so-called “diesel knocking”) is less and less tolerated. Furthermore, the possibilities to tune the combustion with respect to noise are nowadays more limited due to the more stringent targets for CO2 and Euro 5/6 emissions. This possibly leads to a higher risk in not fulfilling exterior and interior sound quality targets like diesel knocking noise. The diesel knocking perceived inside the vehicle is influenced by various parameters.

The description of subjectively perceived acoustical comfort inside vehicle compartments is a complex challenge. On the one hand, it depends on physically measurable events like acoustical stimuli with a defined sound pressure level and frequency distribution. On the other hand, it is also strongly dependent on further factors like the customer's individual expectations, the previously made experiences and other contextual influences. Furthermore, many different driving conditions have to be considered for a customer-related assessment of driving comfort. In this paper, the mechanisms of acoustical comfort inside vehicle compartments are described on basis of various measurements, listening tests and qualitative assessments. The acoustical properties of driving noises at various driving conditions were taken into account as well as room-acoustical parameters of vehicle interiors and factors of speech communication between passengers.

The goal of constructing squeal free brakes is still difficult to achieve for design engineers. There are many measures that are beneficial to avoid or decrease brake squeal, examples are the increase in damping and the introduction of asymmetries in the brake rotor. For an efficient design process these measures have to be quantified. This is difficult due to the high complexity of the system which is caused by the contact conditions and the complicated properties of the pad material which consists of a vast amount of different components. The attempt presented in this paper is to use fundamental models of the excitation mechanism for brake squeal in order to quantify the rate of asymmetry and damping required to get far away from the squeal boundary. The relation can be helpful to generate adequate objective functions for a systematic structural optimization of brake rotors against squeal and can be used as a design guideline.

This paper will compare systematically coaxial and non-coaxial internal heat exchanger types on the component and the system level as applied to R1234yf mobile air conditioning (MAC) systems. Pressure drop, heat transfer rate, effectiveness, and efficiency ratio of the Internal Heat Exchanger (IHX) are compared on the component level for the different heat exchanger types. At the system level, a MAC system optimized for efficiency as well as evaporator cooling capacity is used to assess these different internal heat exchanger types. System level factors that will be discussed include IHX heat transfer rate, pressure drop, compressor efficiency, compressor discharge temperatures, and the impact of these factors on the efficiency and capacity of the MAC system. This paper also describes the test bench used for the system level tests and the testing procedure applied.

A structural-acoustic finite-element model of an automobile trimmed-body is developed and experimentally evaluated for predicting body vibration and interior noise for frequencies up to 200 Hz. The structural-acoustic model is developed by coupling finite element models of trimmed-body structure and the passenger-compartment acoustic cavity. Frequency-response-function measurements of the structural vibration and interior acoustic response for shaker excitation of a trimmed body are used to assess the accuracy of the structural-acoustic model.

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.