Modelling and Cavitation Discrepancy Analysis of Multi-Cylinder Engine Based on Variational Mode Decomposition (VMD)

Reduction of engine development time and cost is of primary interest for combustion engine manufacturers. This reduction is complicated by the fact that it has to be realized simultaneously with the fulfilling of ever more stringent legislative demands regarding emissions of NOx and Particulate Matter (PM) and demand from the (transportation) market to reduce fuel consumption. Meeting these demands has resulted in the addition of new technologies with their own degrees of freedom. Furthermore new advanced combustion concepts, such as low-temperature high-EGR combustion are being developed. These new concepts put great demands on in-cylinder charge condition (composition, temperature, pressure) and combustion control. This has led to complex and non-transparent engine control systems which increase development time and costs. The main contribution of this work is the development of a physically-based control oriented in-cylinder CI engine combustion model which predicts the interaction between a) the fuel injection rate and rate of heat release and b) the fuel injection process and the emission of NO (main component of NOx) and soot (main component of PM) emission for both conventional and advanced, high-EGR, CI combustion. Although the model is developed to be generally applicable, the validation process has been limited to only include Heavy Duty DI diesel engines. The NO, soot and heat release rate model combine (existing) zero and one-dimensional phenomenological models. These models describe the essential combustion physics and kinetics following the latest insights on the primarily mixing-controlled diesel spray-combustion process. This physical basis distinguishes the combustion model from the majority of combustion models for control applications found in literature that have a more empirical nature. It increases the predictive capabilities of the model and makes it more generic. As a result the amount of measurement data required for model identification will be lower and will reduce development time and costs. The soot and heat release rate model are based on existing state-of-the art models from literature. They are adapted to obtain a more accurate physical basis and to allow the prediction of advanced, high-EGR, combustion. For complete model identification and validation, this thesis presents a complete chain of measurements, comprising dedicated measurement set-ups. This chain starts with the characterization of the fuel injection equipment performing mass flow rate and momentum flow rate measurements, which allows reconstructing accurately the fuel injection rate corresponding to a performed engine test. Thereafter, the fuel spray behaviour is characterized, mainly by tuning existing spray-correlations on the basis of dedicated measurement data from an optically accessible high pressure chamber (The Eindhoven High Pressure Cell). Main emission model identification and validation is performed on the basis of measured heat release rates (i.e. as derived from measured in-cylinder pressure curves) from a research-type single-cylinder Heavy Duty diesel engine. The resulting identified and validated model is directly applied to a multi-cylinder Heavy Duty diesel engine. Results show that the heat release rate and emission formation models of NO and soot show satisfactory qualitative agreement with measurements for changes in fuelling (injection timing, pressure and quantity), EGR rate and engine speed, for both conventional and high-EGR combustion with conventional timing. These results validate the use of the model as predictive tool in the control development process. For NO, quantitative accuracy is in-line with or better than comparable state-of-the-art models with a more profound empirical nature. However, the obtained accuracy is currently not sufficient to use the model as virtual NO sensor in control applications. For accurate NO prediction a high accuracy is required on the prediction of the NO formation temperature evolution. The most important phenomena that influence this evolution have been examined and implemented by physically-based models that are supported by detailed computations on laminar flamelets and homogeneous reactor models. Simulation results show that the primary NO reducing phenomena are dissociation and flame straining by turbulence. Fuel evaporative cooling and hot soot particle radiative cooling are of secondary importance. The reduction in NO formation caused by hot gas radiative cooling only has a marginal influence. Entrainment of fresh, cold, oxidizer into the hot combustion products, in which the NO formation occurs, has to be accounted for to allow accurate NO formation. Equivalent reductions cannot be obtained by aforementioned NO reducing phenomena. The prediction of NO and soot emissions from a multi-cylinder engine is significantly more accurate when the emission formation of each individual cylinders are evaluated instead of using data from only one cylinder. This requires additional sensors, which is not desirable for cost reduction. Finally, the emission formation prediction accuracy when using predicted heat release rate profiles instead of ‘measured’ curves is examined. This shows that especially a very high accuracy on the instantaneous heat release rate is required while this is of much lesser importance for accurate NO formation prediction.

Diesel engines are useful for commercial vehicles because of low fuel consumption and CO<SUB>2</SUB> emissions that cause the greenhouse effect. However, it is necessary for environmental conservation to develop clean combustion. For thirty years, the combustion phenomena of diesel engines using combustion chamber visualization techniques have been widely studied by many researchers. Since in-cylinder flame temperature affects directly on NOx characteristics in engines, this phenomena has been studied in detail in multi-cylinder diesel engines using a new method to measure the in-cylinder temperature distribution by a two color method. Typical two color methods for two dimensional temperature distribution have used negative color films as recording media. So it took several days to analyze the flame temperature. However since the new system consists of a CCD camera and computer, the analyzing time is reduced to about 10 minutes. Parametric studies on injection timings, engine loads, intake valve layouts, and EGR rates using multi-cylinder commercial engines were carried out to investigate the effect of the flame temperature on NOx concentration. Each parameter study showed that the maximum temperature which occurred in a local stoichiometric combustion area of flame is correlative with NOx emissions rather than mean temperature.

Properties and use of Moringa oleifera biodiesel and diesel fuel blends in a multi-cylinder diesel engine

In consideration of its vast resources in Malaysia, the potential use of a nonedible biodiesel source from rubber seed oil (RSO) is explored. However, a mixture with a high saturation content feedstock is required to increase its oxidation stability, which is caused by its 78.93% unsaturation content. Two blends of 20% and 50% v/v rubber seed biodiesel (RB) or palm biodiesel (PB) and varying percentage mixtures of these two feedstock oils biodiesel (RPB) were evaluated on combustion performance in a 55 kW multi-cylinder diesel engine at full load conditions. The results showed that feedstock blending offered benefits in terms of fuel properties enhancement, improved engine performance, and reduced emissions. In comparison to RB, RPB showed higher brake power (BP) of 1.18–2.97% and lower brake specific fuel consumption (BSFC) of 0.85–3.69%, smoke opacity (11.89–14.19%), carbon monoxide (CO) of 2.48–6.93%, hydrocarbon (HC) of 2.36–9.34%, and Nitrogen oxide (NO) emissions of 2.34–5.93%. The cylinder pressures and heat release rates (HRR) of RPB blends were 8.47–11.43% and 36.02–46.61% higher than diesel, respectively. The start of combustion angles (SOC) of RB and RPB blends were from −13 to −15 °C and from −13.2 to −15.6 crank angle degree (°CA) before top dead center (BTDC), but the combustion delays were 6–8 °C and 5.4–7.8 °C shorter when compared to diesel fuel which were −10 °C BTDC and 11 °C, respectively. It can be concluded that RPB blends showed better performance and emissions over the individual rubber seed and palm biodiesel blends and can replace diesel fuel in unmodified engines.

Diesel engines are widely used in railway systems, particularly in freight trains. Despite their high efficiency in energy conversion, they usually generate high levels of acoustics pollution during operation. In order to mitigate this problem, a series of active/passive acoustics control methods are used to reduce noise. Most of these methods are only effective if the prior knowledge of sources is given. In other words, it is essential to recognize the acoustics source. Variational mode decomposition (VMD) is a signal processing method that enhances the signal corrupted by background noise. However, the decomposed results of VMD depend on their mode parameter and penalty parameter. Therefore, an evaluation method based on system modal parameters (natural frequency and damping ratio) is proposed to select the mode parameter, and the penalty parameter can be selected from the power spectra of signals. In order to increase the accuracy of decomposition for diesel engines and find out the sources of acoustics, a method combining VMD, fast independent component analysis, and Hilbert transformation (VMD‐FastICA‐HT) is proposed for the separation and identification of different sources for diesel engines. The optimization results indicate that when the penalty parameter value is 1.5 to 16 times the maximum signal amplitude, better decomposition results can be achieved. Therefore, the separated independent acoustics are more accurate in source identification. Furthermore, both simulation data and in situ operational data of diesel engines for vehicles are used to validate the effectiveness of the proposed method.

As a motive power in heavy construction machineries including mining and various construction works, a multi-cylinders type of diesel engine is very often used because of its high cost performance. Steady maintaining of diesel engine's operation is substantial in view of economic demands and environmental concerns. To realize this, a practice of early diagnosis and early repair are essential.In our previous study using a V-12 type of diesel engine installed on a bench, we demonstrated that a misfiring cylinder could be detected by statistical analysis method using rms value of the acceleration waveforms measured on a single point of the engine block.In this paper, the same experimentation and analyses as in the previous study were conducted for two practical machineries that loaded the same type engine of the previous study. Even though the engine was loaded on a practical machinery, it was found that a misfiring cylinder could be detected by the same way as in the previous study. In addition to the analyzing method in the previous study, in this study, we employed a wavelet transform method with the Gabor function as a window, and analyzed the acceleration waveforms. The results of wavelet analysis revealed that a misfiring cylinder could be detected visually from time-frequency charts. With the aid of statistical analysis using rms value, a misfiring cylinder in a multi-cylinder diesel engine can be doubly checked by wavelet analysis.

The dynamics and vibrations of camshaft excited by multi-follower elements are modeled and analyzed. A pushrod valve train system from a four-cylinder diesel engine is selected as the case study. The camshaft is modeled to analyze the interactions of multi-follower elements. Both the camshaft angular vibration and bending vibration are taken into consideration. Each follower element is simplified as a multi-mass system. The lumped masses are connected by the spring elements and the damping elements. The contact force model at the cam–tappet interfaces was developed based on the elasto-hydrodynamic lubrication theory of finite line conjunction. From the analysis results, it can be seen that the bending vibration of camshaft is mainly in the normal direction at the cam–tappet interfaces. Moreover, the bending vibration is mainly influenced by the overlapping of inlet cam function and exhaust cam function of each cylinder. The angular vibration of camshaft mainly focuses at the fundamental frequency and the harmonic frequency corresponding to the cylinder number.

Cooled exhaust gas recirculation (EGR) is used to control engine out NOx (oxides of nitrogen) emissions from modern diesel engines by re-circulating a portion of the exhaust gases into the intake manifold of an engine after cooling it through a heat exchanger commonly referred to as an EGR cooler. However, EGR cooler fouling due to presence of soot particles and hydrocarbons (HC) in engine exhaust leads to a decrease in cooler efficiency and increased pressure drop across the cooler. This can adversely affect the combustion process, engine durability, and emissions. In this study, a multicylinder diesel engine was used to produce a range of engine out HC and soot concentrations to investigate soot deposition and particle nucleation in an EGR cooler. A portion of the engine exhaust was passed through an EGR cooler, while particle size and HC concentration measurements were made at the cooler inlet and outlet. Tests were conducted over a range of EGR cooler coolant temperatures and engine out soot and HC concentrations to determine the impact on the nucleation and accumulation modes of the exhaust particle size distributions. A reduction in the accumulation mode particle concentration at the EGR cooler outlet was observed for high soot concentrations indicating soot deposition within the EGR cooler. As the EGR coolant temperature was reduced, the outlet accumulation mode particle concentration was reduced further, indicating increased soot deposition in the cooler due to increased thermophoresis. There were no signs of diffusiophoresis due to HC diffusion within the cooler over the range of conditions used in the study. A significant increase in outlet nucleation mode particle concentration was observed for the low soot concentrations. This mode increased with either increasing HC concentration or decreasing coolant temperature, indicating the saturation ratio (SR) dependence of the nucleation mode formation. However, as the soot concentration was increased, the nucleation mode disappeared because of HC adsorption onto the increased soot surface area. Copyright 2012 American Association for Aerosol Research

The impact of methanol injecting position on cylinder-to-cylinder variation in a diesel methanol dual fuel engine

Performance and emission analysis of Jatropha curcas and Moringa oleifera methyl ester fuel blends in a multi-cylinder diesel engine

The safe operation of diesel engines performs a vital function in industrial production and life. Because diesel engines often work in harsh environmental conditions, they are prone to failure. Therefore, this paper proposes a fault analysis method based on a combination of optimized variational mode decomposition (VMD) and improved convolutional neural networks (CNN) to address the necessary need for preventive maintenance of diesel engines. The authentic vibration sign is first decomposed by using the (VMD) algorithm, then the greatest range of decomposition layers is decided by using scattering entropy and the useful components are preferentially chosen for reconstruction. The continuous wavelet transform (CWT) records preprocessing method is then delivered to radically change the noise-reduced vibration sign into a time-frequency map, which is fed into the CNN for model coaching and extraction of fault features. Finally, fault classification is realized by support vector machine (SVM) with excellent classification performance. Through preset fault experiments on diesel engines, it is established that the technique proposed in this paper can successfully identify fault states, and the classification accuracy is higher than alternative methods.

Diesel engines, as power equipment, are widely used in the fields of the automobile industry, ship industry, and power equipment. Due to wear or faulty adjustment, the valve train clearance abnormal fault is a typical failure of diesel engines, which may result in the performance degradation, even valve fracture and cylinder hit fault. However, the failure mechanism features mainly in the time domain and angular domain, on which the current diagnosis methods are based, are easily affected by working conditions or are hard to extract accurate enough from, as the diesel engine keeps running in transient and non-stationary processes. This work aimed at diagnosing this fault mainly based on frequency band features, which would change when the valve clearance fault occurs. For the purpose of extracting a series of frequency band features adaptively, a decomposition technique based on improved variational mode decomposition was investigated in this work. As the connection between the features and the fault was fuzzy, the random forest algorithm was used to analyze the correspondence between features and faults. In addition, the feature dimension was reduced to improve the operation efficiency according to importance score. The experimental results under variable speed condition showed that the method based on variational mode decomposition and random forest was capable to detect the valve clearance fault effectively.

&lt;div class="htmlview paragraph"&gt;Lube oil contamination is a primary-reason for engine wear. The wear processes promoted by oil contamination lead to diminished fuel efficiency, shorter useful oil service life, reduced component life, and loss of engine performance. Contaminant particles responsible for this damage are in the size range of the dynamic lubricant films separating moving engine component surfaces: 10 microns and smaller. By making simultaneous contact with opposing surfaces these harmful particles focus the load onto a small area, degrading the surface. This paper reviews the nature of lubricant contamination, the modes of lubrication, and the primary mechanisms of engine wear. The correlation between contamination and wear of engine components, as well as several important studies quantifying the effect of contamination on engine wear and performance, are discussed. It is concluded that operating with clean lube oil, maintained by 10 micron filtration (b&lt;sub&gt;10&lt;/sub&gt; ≥75), results in a diesel engine having better fuel economy, longer oil change intervals, superior performance, and greater durability.&lt;/div&gt;

Abstract. It is a great challenge to apply a diagnostic system for sensor fault detection to engine test beds. The main problem is that such test beds involve frequent configuration changes or a change in the entire test engine. Therefore, the diagnostic system must be highly adaptable to different types of test engines. This paper presents a diagnostic method consisting of the following steps: residual generation, fault detection and fault isolation. As adaptability can be achieved with residual generation, the focus is on this step. The modular toolbox-based approach combines physics-based and data-driven modeling concepts and, thus, enables highly flexible application to various types of engine test beds. Adaptability and fault detection quality are validated using measurement data from a single-cylinder research engine and a multicylinder diesel engine.

Three injectors with different nozzle geometries were tested in a multicylinder diesel engine with a high-pressure common-rail injection system. Various injection pressures were tested along with exhaust gas recirculation to achieve low NOx and soot emissions. The injectors used in the study included a six-hole nozzle, a ten-hole nozzle, and a six-hole convergent nozzle with a K-factor of 3. All three injectors had the same flow numbers. All three injectors tested were effective in reducing NOx and soot emissions at appropriate conditions. It was found that low temperature combustion can be achieved by using high levels of exhaust gas recirculation with late injection timings. High injection pressures significantly reduced soot emissions at conventional injection timings. The effect of injection pressure was not significant at retarded injection timings, i.e., 5 ATDC. The convergent nozzle was found to produce higher soot emissions compared with the straight-hole nozzle under the same injection conditions. Effects of the convergent nozzle on NOx emissions and fuel consumption were not significant. The small nozzle size in the ten-hole injector can generate smaller fuel drops and lead to better atomization. The ten-hole injector appeared to have better air utilization and resulted in significant reductions in NOx and soot emissions over a wide range of operating conditions.