Axial cooling fans are commonly used in electric vehicles to cool batteries with high heating load. One drawback of the cooling fans is the high aeroacoustic noise level resulting from the fan blades and the obstacles facing the airflow. To create a comfortable cabin environment in the vehicle, and to reduce exterior noise emission, a low-noise installation design of the axial fan is required. The purpose of the project is to develop an efficient computational aeroacoustics (CAA) simulation process to assist the cooling-fan installation design. This paper reports the current progress of the development, where the narrow-band components of the fan noise is focused on. Two methods are used to compute the noise source. In the first method the source is computed from the flow field obtained using the unsteady Reynolds-averaged Navier-Stokes equations (unsteady RANS, or URANS) model. In the second method, the azimuthal modes of the flow field obtained using the steady RANS with the moving reference frame model are treated as the sound source. While the first method is able to resolve any…

Increasing demand for simulation accuracy often leads to increased model complexity, which in turn, results in higher computational costs. As a provision, Component Mode Synthesis approaches are employed to approximate the system response by using dynamic substructuring and model reduction techniques in linear systems. However, the use of available model reduction techniques in nonlinear problems has not been completely addressed. In this paper, the application of a Component Mode Synthesis method in squeak and rattle nonlinear simulation has been investigated. Critical regions for squeak and rattle of the side door model of a passenger car were modelled by nonlinear contact interfaces in finite element solution. Craig-Bampton model reduction method was employed to substructure the finite element model, while keeping the nonlinear contacts in the model. Model response was evaluated using Modal Assurance Criterion, frequency response analysis and contact force magnitude in comparison with the baseline model. Results showed that a great reduction in computational time (about 97%) can be achieved while the accuracy of the system response was maintained at an acceptable range for the…

This paper presents a feedback control strategy aimed to reduce noise and wear during gearshifts in conventional and hybrid Dual Clutch Transmissions (DCT and DCTH) and Automated Manual Transmissions (AMT). The control strategy is based on a new dog teeth position sensor developed by China Euro Vehicle Technology AB and existing speed sensors in the transmission. During gear shifting, noise is generated by impacts between the sleeve teeth and the idler gear dog teeth after speed synchronization. Besides noise, these impacts are also responsible for delaying the completion of shift and contribute to wear in the dog teeth, hence reducing the lifespan of the transmission. The presented control strategy controls speed synchronization such that the impact between sleeve and idler gear dog teeth, before the start of torque ramp up, is avoided. Since drag torque is an important factor in speed synchronization, this paper also contains an algorithm to identify friction torque coefficient in the transmission. The identification method ensures that the controller adapts to varying conditions without the need for offline calibration. The control…

Automotive industry makes extensive use of virtual models to increase the efficiency during the development stage. The complexity of such virtual models increases as the complexity of the process that they describe, and for this reason new methods for their development are constantly evaluated. Among many others, data-driven techniques and machine learning offer promising results, creating deep neural networks that map input-output relations. This works aims at evaluating the performance of different neural network architectures for the estimation of engine status and gas emissions. More specifically, Convolutional Neural Network (CNN) and Long-Short Term Memory (LSTM) will be evaluated in terms of performance, using different techniques to increase the model generalization. During the learning stage data from different engine cycles are fed to the neural network. To evaluate model generalization the network is then tested over new, previously unseen, engine cycles. Results show that our model over-performs a state of the art models, the best performance was found from the LSTM model with 2.40%, 2.80% and 18.19% error for flow fuel, NOx and soot sensor respectively.

Homogeneous lean combustion (HLC) can be utilized to substantially improve SI ICE efficiency which is vital in the process of enabling clean, efficient and affordable propulsion for the next generation light duty vehicles. More research is however necessary to ensure robustness, fuel efficiency/ NOx trade-off and utilization of HLC. Utilization can be improved by expanding the HLC operating window to higher engine torque domains which increases impact on real driving. The authors have earlier assessed dedicated HLC boosting in a downsized 2lt engine but it was found that HLC operation could not be achieved above 15 bar IMEP due to instability and knock. The observation led to the conclusion that there exists a lean load limit. Therefore, further experiments have been conducted in a single cylinder research SI GDI engine to increase understanding of high load lean operation. HLC is known to suppress end-gas autoignition (knock) by decreasing reactivity and temperatures, but during the experiments knock was observed to be prominent and increasing in severity when engine load was increased despite operating ultra-lean close to…

The potential of 48V Mild Hybrid is promising in meeting the present and future CO2 legislations. There are various system layouts for 48V hybrid system including P0, P1, P2. In this paper, P2 architecture is used to investigate the effects of water injection benefits in a mild hybrid system. Electrification of the conventional powertrain uses the benefits of an electric drive in the low load-low speed region where the conventional SI engine is least efficient and as the load demand increases the IC Engine is used in its more efficient operating region.Engine downsizing and forced induction trend is popular in the hybrid system architecture. However, the engine efficiency is limited by combustion knocking at higher loads thus ignition retard is used to avoid knocking and fuel enrichment becomes must to operate the engine at MBT (Maximum Brake Torque) timing; in turn neutralizing the benefits of fuel savings by electrification. Water injection suppresses engine knocking and enables operating at stoichiometric air-fuel ratio. In addition to that, the injection of water reduces flame temperature, giving room to…

Water injection can be applied to spark ignited (SI) gasoline engines to increase the Knock Limit Spark Advance (KLSA) and improve the thermal efficiency. The KLSA potential of 6°CA to 11°CA is shown by many research groups for EN228 gasoline fuel using numerical tools and experimental methods. The influence of water is multi-layered since it reduces the in-cylinder temperature by vaporization and higher heat capacity of the fresh gas, it changes the chemical equilibrium in the end gas and prolongs the ignition delay and laminar flame speed. The aim of this work is to extend the investigation of water injection to different octane number fuels (RON0, RON20, RON50, RON80, RON90 and RON100). The investigation is performed for high load operating conditions at three different engine speeds at 1500rpm, 2000rpm and 2500rpm. The numerical toolbox used for the analysis consists of a detailed reaction scheme for gasoline fuels that was previously used to evaluate the water effect on thermodynamics and chemistry, the quasi-dimensional Stochastic Reactor Model and the Detonation Diagram. The detailed reaction scheme is used…

The various factors that affect ride comfort have been in focus in many research studies due to an increasing demand in ride comfort in the automotive industry. Noise, vibration and harshness (NVH) and the human response to NVH has been highlighted as an important contribution to assess and predict overall ride comfort. The purpose of this paper is to present an approach to explain ride comfort with respect to vibration for the seated occupant based on a systematic literature review of previous fundamental research and to relate these results to the application in the contemporary automotive industry. The results from the literature study show that numerous research studies have determined how vibration frequency, magnitude, direction, duration affect human response to vibration. Also, the studies have highlighted how body posture, age, gender and anthropometry affect the human perception of comfort. An analysis was made of the consistency and inconsistency of the results obtained in the different studies. The deviations of the research results from real-world ride comfort in automotive vehicles were analyzed and divided into three…

The automotive trends of vehicles with lower aerodynamic drag and more powerful drivetrains have increased the concern of stability issues at high speeds, since more streamlined bodies show greater sensitivity to crosswinds. This is especially important for high vehicles, such as sports utility vehicles. In addition, the competitiveness in the automotive industry requires faster development times and, thus, a need to evaluate the high speed stability performance in an early design phase, preferable using simulation tools. The accuracy of these simulation tools partly relies on realistic boundary conditions for the wind and quantitative measures for assessing stability without the subjective evaluation of experienced drivers. Hence, this study employed an on-road experimental measurements setup to define relevant wind conditions and to find an objective methodology to evaluate high speed stability. The paper is focusing in detail on the events in proximity to the drivers' subjective triggers of instability. Wind direction and magnitude, vehicle motion response, driver steering input along with the subjective event triggering were measured for several aerodynamic configurations during different conditions of the natural…

A method for measuring apparent soot particle size and concentration in turbulent combusting diesel jets with elevated and inhomogeneous optical density is presented and discussed. The method is based on the combination of quasi-simultaneous Laser Induced Incandescence (LII), Elastic Scattering (ELS) and Light Extinction (LE) measurements exhibiting a high potential for spatially resolved measurements of carbonaceous particles in flames and residual gases at a given instant. The method evaluates the LII signal by calculating the laser fluence across the flame and compensating for signal trapping, allowing measurements where laser extinction between the flame borders reaches values up to 90 %. The method was implemented by measuring particle size and concentration in the middle sagittal axis of optically dense, combusting diesel jets at a certain time after the start of combustion. Experiments were carried out in the Chalmers High Pressure, High Temperature spray rig under conditions similar to those prevailing in direct injected compression ignition engines. Measurements of apparent particle size and concentration together with volume fraction conferring an instantaneous single-shot case and an average measurement…