Internal Combustion Engine Noise Research Articles

Simulating Noise, Vibration, and Harshness Advances in Electric Vehicle Powertrains: Strategies and Challenges

This study examines the management of noise, vibration, and harshness (NVH) in electric vehicle (EV) powertrains, considering the challenges of the automotive industry’s transition to electric drivetrains. The growing popularity of electric vehicles brings new NVH challenges as the lack of internal combustion engine noise makes drivetrain noise more prominent. The key to managing NVH in electric vehicle powertrains is understanding the noise from electric motors, inverters, and gear systems. Noise from electric motors, mainly resulting from electromagnetic forces and high-frequency noise generated by inverters, significantly impacts overall NVH performance. This article details sources of mechanical noise and vibration, including gear defects in gear systems and shaft imbalances. The methods presented in the publication include simulation and modeling techniques that help identify and solve NVH difficulties. Tools like multi-body dynamics, the finite element method, and multi-domain simulation are crucial for understanding the dynamic behavior of complex systems. With the support of simulations, engineers can predict noise and vibration challenges and develop effective solutions during the design phase. This study emphasizes the importance of a system-level approach in NVH management, where the entire drivetrain is modeled and analyzed together, not just individual components.

Numerical Analysis to Investigate the Impact of Skirt Geometric Parameters on Secondary Piston Movement in a Single-cylinder Diesel Engine

Currently, modern internal combustion engines are receiving great attention due to their efficiency, particularly in response to the increasing limits imposed by environmental and emission legislation. Sound emissions of internal combustion engines are mainly caused by three sources of noise: combustion, mechanical and aerodynamic flow. The secondary motion of the piston plays a crucial role in the analysis of performance, noise, vibration and reliability of internal combustion engine (ICE). In the presented article, a mathematical simulation model has been developed by using of the GT-Suite software to study the rotational and lateral motion of the piston (called secondary motion) as well as the piston slap in ICE. This model takes into account the effect of variation in the major geometric parameters of the skirt design, such as the piston pin offset (P.P.O) and the length of the skirt. Furthermore, a combined model that accounts for the interplay between the secondary dynamics of the piston and the dynamic fluid lubrication has been developed. This model utilizes a mixed lubrication approach for the purpose of simulation. The results of this simulation have demonstrated that the variations in length of the skirt and the P.P.O have a considerable effect on piston secondary motion and tribological performances, and that the lateral motion of the piston is significantly influenced by the piston side force, which plays a crucial role in this behavior.

Case study: Noise attenuating performance of perforated corrugated lined straight-through perforated pipe-resistant muffler

Noise of internal combustion engine is the main source of noise pollution, and mufflers are the main means to reduce exhaust noise of internal combustion engine. In the process of improving the acoustic performance of the exhaust muffler based on the three-dimensional numerical method, the influence of the high speed and high temperature airflow discharged by the engine in the actual working process on the acoustic performance of the exhaust muffler is often ignored, which leads to the obvious deviation between the predicted results and the actual situation. In this paper, based on the structural optimization design of the straight-through perforated pipe resistance muffler, the noise characteristics of the straight-through perforated pipe resistance muffler with perforated corrugated lining was analyzed considering the airflow velocity and temperature inside the muffler. The influence of temperature and velocity fields on the acoustic performance of muffler was studied by using numerical simulation method, which takes the solution results inside muffler as boundary conditions of sound field analysis. The influence of changing the internal structure of muffler on the aerodynamic performance of muffler was discussed, and the pressure loss is analyzed. The research has shown that adding perforated corrugated lining inside muffler could effectively improve the transmission loss of muffler and the noise reduction performance of prototype straight-through perforated pipe-resistant muffler.

Localization of car engine noise sources

The engine of a vehicle, particularly a passenger car, is one of the main sources of noise radiated into the environment and creates a noise load in residential areas, which has a negative impact on people. Experts in the field of acoustics perform computational and experimental acoustic studies both at the design stage, and at the stage of putting into production and directly operating the engine as part of the car to reduce engine noise. An important stage of acoustic research is the localization of the most intensely radiating noise of systems, mechanisms, nodes and engine parts. The article presents the results of experimental studies on localization of internal combustion engine noise sources of a LADA car.

Minimizing transmission error with neural networks and genetic algorithm with quadratic mutation rates

Transmission error quantifies the rotation delay between driving and driven gear, caused by the disturbances of inevitable factors such as elastic deformation, manufacturing error, and mesh misalignment in assembly. A major consequence of high transmission error is the distinguishable whining noise, which indicates wear and efficiency loss. The transmission error (TE) becomes a further serious concern in case of electric vehicles where there is no background noise of internal combustion engine to diminish the gear noise and thus, gears trains become a major, if not only, source of noise in electric vehicles. Hence minimizing TE is a major concern for modern powertrain systems. This research work puts forth a novel approach for finding the optimal mutually independent microgeometry parameters which contribute to minimal transmission error. A neural network learns from the model specific generated data and gives out an approximating function which is then fed to a genetic algorithm which finds the global minima of the output function and therefore the values of the corresponding microgeometry parameters. The neural network and genetic algorithm were programmed from scratch in Python 3.7. The genetic algorithm was further tested with uniform mutation rates and variable mutation rates to find the degree of possibility of premature convergence. The former was found more vulnerable to premature convergence.

Influence of steering vibration on vehicle speed recognition and comfortableness in cabin.

In recent years, electric vehicles are becoming more popular. This transition makes interior noise and vibration smaller according to the engine rest and makes interior more comfortable. On the other hand, this reduction has a possibility to decrease important information for drivers. In this study, we focused on the steering vibration as the vehicle speed information and investigated the influence on the comfortableness in cabin for the compatibility through subjective evaluation test using a simple driving simulator. In the test, vehicle speed controlling task was given to the participants without speed meter at acceleration conditions. In addition, subjective evaluation about the comfortability to the presented sound and vibration was conducted after the speed recognition test. As the presented steering vibration, the following four patterns were prepared. 1: internal combustion engine noise and vibration with road and wind noise (background noise), 2: electric-powered vehicle noise without vibration (background noise without vibration), 3: tire vibration with background noise, 4: motor vibration with background noise. As the result, the steering vibration of internal combustion engine or motor was found to be suitable stimuli for compatibility between the speed recognition performance and the comfortability in cabin.

Acoustic characteristics of aero internal combustion engines

This paper provides a brief overview of internal combustion engines’ noise generating mechanisms. Spectral, energy, and spatial characteristics of the sound field of internal combustion engines used in aviation as part of power plants of light aircraft and unmanned aerial vehicles are considered. The influence of load and flight conditions on the engine noise is considered. An example of the calculated noise estimation of a single-cylinder four-stroke engine is presented. The main methods of reducing internal combustion engine noise are formulated.

Investigation of the effects of turbulence modeling on the prediction of compression-ignition combustion unsteadiness

Adverse effects of global warming due to the greenhouse gas emissions is changing the actual paradigm for the use energy resources. In the absence of a mid-term solution for reducing these emissions in transportation, internal combustion (IC) engines are going to coexist in the social spheres in the foreseeable future. Therefore, the study of other IC engine-related problems remains relevant to ensuring the health of the society. In this investigation, a numerical methodology for comprehensive understanding of Noise, Vibration and Harshness in internal combustion engines is proposed. Due to its inherent complexity and lack of awareness, the main objective is to evaluate the impact of the turbulence modeling framework on the in-cylinder acoustic field recreation. Modal decomposition methods have been applied to isolate the coherent flow structures and to analyze how they change with the turbulence approach. Results demonstrate that the choice of the turbulence model is a critical aspect for noise modeling. Unsteady Reynolds-Averaged Navier-Stokes schemes predict a raw estimation of the internal acoustic field with the added value of being computationally less expensive. However, the use of more complex turbulence approaches such us large eddy simulation offers an accurate prediction of the acoustic structures and their cyclic dispersion.

Calculation of the required noise reduction of a engine exhaust system

The problem of reduction of internal combustion engine (ICE) noise is most urgent at present when the fleet of vehicles has significantly expanded and their power has increased. Reactive mufflers are often used to solve it. The initial stage in the design of mufflers is a theoretical assessment of the frequency spectrum of sound power level (SPL) of an unmuffled ICE noise source, comparing it with the calculated maximum permissible spectrum and determining the required amount of its reduction in standard frequency bands. The paper presents a method for calculating the required noise reduction of a transport engine exhaust using the example of a two-stroke ICE of the class of 125 cm3. Thus, the designer has the opportunity to develop mufflers, the acoustic efficiency of which meets the calculated required noise reduction values, already at an early stage of the vehicle design.

SOFTWARE DEVELOPMENT FOR ESTIMATION OF LOW FREQUENCY SOUND PROPAGATION IN GAS GUIDES OF POWER PLANTS TAKING TO ACCOUNT ACTIVE SOUND SOURCES

This paper is devoted to the problems of modelling and calculation of propagation of low frequency sound in gas guides of power plants taking to account active sound sources. The structure of software for prediction and calculation of low-frequency sound propagation in gas guides have described. Software uses four-pole method and takes to account radiation from additional (active) sound course. By using software it is possible to estimate sound source parameters to provide efficient sound attenuation. Examples of software application to calculation of intake and exhaust noise of internal combustion engine are described. The results of calculations show the possibilities of four-pole method software using to design acoustically the parameters of gas guides and mufflers for the different fields of applications.

Noise Source Separation of an Internal Combustion Engine Based on a Single‐Channel Algorithm

The separation and identification technology of noise sources is the focus and hot spot in the field of internal combustion engine noise research. Combustion noise and piston slap noise are the main noise sources of an internal combustion engine. However, both combustion noise and piston slap noise occur almost at the top dead center. They mix in the time domain and frequency domain. It is difficult to accurately and effectively separate them. A single‐channel algorithm which combines time‐varying filtering‐based empirical mode decomposition (TVF‐EMD) and robust independent component analysis (RobustICA) methods is proposed to separate them. Firstly, the TVF‐EMD method is utilized to decompose the single‐channel noise signal into several intrinsic mode functions (IMFs). Then, the RobustICA method is applied to extract the independent components. Finally, related prior knowledge and time‐frequency analysis are employed to identify noise sources. Furthermore, the spectral filtering method and the calculation method of piston slap noise based on the dynamic model are further carried out to verify separation results. The simulation and experimental research results show the effectiveness of the proposed method.

Automatic Evaluation of Internal Combustion Engine Noise Based on an Auditory Model

To improve the accuracy and efficiency of the objective evaluation of noise quality from internal combustion engines, an automatic noise quality classification model was constructed by introducing an auditory model‐based acoustic spectrum analysis method and a convolutional neural network (CNN) model. A band‐pass filter was also designed in the model to automatically extract the features of the noise samples, which were later used as input data. The adaptive moment estimation (Adam) algorithm was used to optimize the weights of each layer in the network, and the model was used to evaluate sound quality. To evaluate the predictive performance of the CNN model based on the auditory input, a back propagation (BP) sound quality evaluation model based on psychoacoustic parameters was constructed and used as a control. When processing the label values of the samples, the correlation between the psychoacoustic parameters of the objective evaluation and evaluation scores was analyzed. Four psychoacoustic parameters with the greatest correlation with subjective evaluation results were selected as the input values of the BP model. The results showed that the sound quality evaluation model based on the CNN could predict the sound quality of internal combustion engines more accurately, and the input evaluation score based on the auditory spectrum in the CNN classification model was more accurate than the short‐time average energy input evaluation score based on the time domain.

Design Optimization Study of a Nonlinear Energy Absorber for Internal Combustion Engine Pistons

Piston impacts against the cylinder liner are the most significant sources of mechanical noise in internal combustion (IC) engines. Traditionally, the severity of impacts is reduced through the modification of physical and geometrical characteristics of components in the piston assembly. These methods effectively reduce power losses at certain engine operating conditions. Frictional losses and piston impact noise are inversely proportional. Hence, the reduction in power loss leads to louder piston impact noise. An alternative method that is robust to fluctuations in the engine operating conditions is anticipated to improve the engine's noise, vibration and harshness (NVH) performance, while exacerbation in power loss remains within the limits of conventional methods. The concept of targeted energy transfer (TET) through the use of nonlinear energy sink (NES) is relatively new and its application in automotive powertrains has not been demonstrated yet. In this paper, a TET device is conceptually designed and optimized through a series of parametric studies. The dynamic response and power loss of a piston model equipped with this nonlinear energy sink is investigated. Numerical studies have shown a potential in reducing the severity of impact dynamics by controlling the piston's secondary motion.

Experimental and Stochastic Reactor Modeling Results of an HCCI Engine Fueled with Primary Reference Fuel

In recent years, much research has been performed in order to decrease fuel consumption, noise, and exhaust emission levels in internal combustion engines. In this study, the effects of excess air coefficient on performance and exhaust emissions (CO, CO2) of an HCCI engine fueled with primary reference fuel (PRF) were investigated for different intake air pressure and temperature values. The simulation studies were performed by using SRM Suite software. The chemical kinetic mechanism, which contains 138 species and 633 reactions that are embedded into the program, was used to simulate the combustion of the PRF fuel during the combustion simulations. The analysis covers the full cycle and provides data about induction, compression, combustion, expansion, and exhaust. The exhaust emissions, cylinder pressure, and heat release rate results were compared with the experimental data. The zero-dimensional software (SRM Suite) gives quite reasonable results compared with the experimental data, and it has advantag...

Research on Experimental Method for Obtaining Independent Combustion Noise of Internal Combustion Engine

Internal combustion engine noise sources are complex and changeable. Combustion noise is usually drowned out by mechanical noise and aerodynamic noise. Traditional noise source identification methods can only qualitatively identify combustion noise. In order to quantitatively obtain the independent pure combustion noise of an internal combustion engine, it is necessary to design and build a separate noise source simulation test bench. In this paper, the combustion noise separation test bench based on transfer function method is designed and implemented. In the test, a pressure pulse device is installed in the combustion chamber. When the piston is at top dead center (TDC), pulse pressure is generated to excite the internal combustion engine to radiate noise. The pressure signal and noise signal are utilized to obtain the transfer function of combustion pressure and noise. Then, according to the cylinder pressure and transfer function, the combustion noise can be directly calculated. The test was carried out on 4120SG diesel engine. Experimental results show that when the internal combustion engine is under 1500 rpm and no‐load condition and 800 rpm and no‐load condition, the frequency components of independent pure combustion noise are both mainly concentrated at 1100 Hz, 1400 Hz, and 3000 Hz. Furthermore, the internal combustion engine vibration test method and the combustion noise empirical formula calculation method are both carried out to show accuracy and effectiveness of the obtained independent combustion noise through the combustion noise separation test based on transfer function method.

Utilisation of the Coherence Analysis in Acoustic Diagnostics of Internal Combustion Engines

AbstractThe leading thought of the present text is that the internal combustion engine noise - regardless of all possible inconveniences - is a good information carrier that allows for the explicit diagnostics of such subtle defect as the valve face decrement which is so small that it is in practice ‘unnoticeable’ by the standard diagnostic-controlling system of a passenger car. However, such defect at its further propagation can be much more dangerous. Thus, diagnosing its initial state is worth trying. This study is a continuation of investigations where efforts were undertaken to perform the efficient diagnostics on the bases of observations and analyses of mechanical vibrations of the engine head.

Radiation Noise Separation of Internal Combustion Engine Based on Gammatone-RobustICA Method

In the internal combustion engine noise source separation process, the combustion noise and the piston slap noise are found to be seriously aliased in time-frequency domain. It is difficult to accurately separate them. Therefore, the noise source separation method which is based on Gammatone filter bank and robust independent component analysis (RobustICA) is proposed. The 6-cylinder internal combustion engine vibration and noise test are carried out in a semianechoic chamber. The lead covering method is adopted to isolate the interference noise from numbers 1 to 5 cylinder parts, with only the number 6 cylinder parts left bare. Firstly, many mode components of the measured near-field radiated noise signals are extracted through the designed Gammatone filter bank. Then, the RobustICA algorithm is utilised to extract the independent components. Finally, the spectrum analysis, the continuous wavelet time-frequency analysis, the correlation function method, and the drag test are employed to further identify the separation results. The research results show that the frequency of the combustion noise and the piston slap noise are, respectively, concentrated at 4025 Hz and 1725 Hz. Compared with the EWT-RobustICA method, the separation results obtained by the Gammatone-RobustICA method have very fewer interference components.

Numerical prediction and analysis of electromagnetic vibration and noise of claw pole alternator

With the improvement of internal combustion engine noise, the noise of claw pole alternator which is universally used on modern automobiles is becoming more distinct. Extensive experimental results show that the noise of claw pole alternator is annoying at low to middle speed and mainly originates from the electromagnetic noise. In this paper, a complete methodology for electromagnetic vibration and noise prediction of claw pole alternator is presented. It is a three-step multiphysics simulation. The first step is to calculate the magnetic force exerted on the inner surface of the stator using 3D FEM. The second step is the structural analysis, which is to investigate the natural resonant frequencies and modal shapes of the alternator system taking into account the real mechanical boundary conditions. The third is the electromagnetic vibration and noise calculation by using modal superposition method and boundary-element method, respectively. Simulation results agree well with those measured by experiments. Furthermore, the mechanisms of electromagnetic vibration and noise are analyzed by using the electromagnetic theory. The method can be used in the initial design stage of claw pole alternator and is also suitable for other types of motor.

歯車衝突を考慮したエンジン振動騒音解析法の研究

歯車衝突を考慮したエンジン振動騒音解析法の研究

On the identification of piston slap events in internal combustion engines using tribodynamic analysis

Piston slap is a major source of vibration and noise in internal combustion engines. Therefore, better understanding of the conditions favouring piston slap can be beneficial for the reduction of engine Noise, Vibration and Harshness (NVH). Past research has attempted to determine the exact position of piston slap events during the engine cycle and correlate them to the engine block vibration response. Validated numerical/analytical models of the piston assembly can be very useful towards this aim, since extracting the relevant information from experimental measurements can be a tedious and complicated process.In the present work, a coupled simulation of piston dynamics and engine tribology (tribodynamics) has been performed using quasi-static and transient numerical codes. Thus, the inertia and reaction forces developed in the piston are calculated. The occurrence of piston slap events in the engine cycle is monitored by introducing six alternative concepts: (i) the quasi-static lateral force, (ii) the transient lateral force, (iii) the minimum film thickness occurrence, (iv) the maximum energy transfer, (v) the lubricant squeeze velocity and (vi) the piston-impact angular duration.The validation of the proposed methods is achieved using experimental measurements taken from a single cylinder petrol engine in laboratory conditions. The surface acceleration of the engine block is measured at the thrust- and anti-thrust side locations. The correlation between the theoretically predicted events and the measured acceleration signals has been satisfactory in determining piston slap incidents, using the aforementioned concepts. The results also exhibit good repeatability throughout the set of measurements obtained in terms of the number of events occurring and their locations during the engine cycle.