Detection and Identification of Detonation Sounds in an Internal Combustion Engine Using Wavelet and Regression Analysis

Improving efficiency and power in an internal combustion engine is always impeded by detonation (knock) problems. This detonation problem has not been explained fully yet. Quick and accurate detection of detonation is also in the development stage. This research used a new method of detonation sound detection which uses microphone sensors, analysis of discrete wavelet transform (DWT), and analysis of the regression function envelope to identify the occurrence of detonation. The engine sound was captured by the microphone; it was recorded on a computer; it was proceeded using a DWT decomposition filtering technique; it was then subjected to normalization and regression function envelope to get the shape of the wave pattern for the vibration. Vibrational wave patterns were then compared to a reference using the Euclidean distance calculation method, in order to identify and provide an assessment decision as to whether or not detonation had occurred. The new method was applied using Matlab and it has yielded results which are quite effective for the detection and identification of detonation and it is also capable of producing an assessment decision about the occurrance of detonation

Detection and Identification of Detonation Sounds in an Internal Combustion Engine using Wavelet and Regression Analysis

Improving efficiency and power in an internal combustion engine is always impeded by detonation (knock) problems. This detonation problem has not been explained fully yet. Quick and accurate detection of detonation is also in the development stage. This research used a new method of detonation sound detection which uses microphone sensors, analysis of discrete wavelet transform (DWT), and analysis of the regression function envelope to identify the occurrence of detonation. The engine sound was captured by the microphone; it was recorded on a computer; it was proceeded using a DWT decomposition filtering technique; it was then subjected to normalization and regression function envelope to get the shape of the wave pattern for the vibration. Vibrational wave patterns were then compared to a reference using the Euclidean distance calculation method, in order to identify and provide an assessment decision as to whether or not detonation had occurred. The new method was applied using Matlab and it has yielded results which are quite effective for the detection and identification of detonation and it is also capable of producing an assessment decision about the occurrance of detonation

The Scaling of Loss Pathways and Heat Transfer in Small Scale Internal Combustion Engines

Prior literature indicates fuel conversion efficiency and normalized power deteriorate increasingly rapidly with decreasing displacement, but does not fully reveal the driving losses. The literature also suggested that increasing losses relax the required fuel anti-knock index (AKI), but offered conflicting conclusions on the performance impact. This comprehensive experimental study of three, 28 cm3 to 85 cm3 displacement, commercial-off-the-shelf (COTS), two-stroke ICEs identified short-circuiting as having the most deleterious impact on COTS engine performance in this size range. Heat transfer losses were comparable to larger engines for displaced volumes greater than 10 cm3. An engine friction model was developed that uses the surface area to volume ratio, speed, and throttle to predict friction losses; a heat transfer model was also validated. The impact of reducing fuel AKI on performance was systematically investigated. The results showed a dependence on engine size; the fuel AKI requirement decreased 20 octane number between 85 cm3 and 28 cm3 displacement. Switching from 98 ON (manufacturer recommended) to 20 ON (JP-8, diesel equivalent) fuel increased power 2 -3 and fuel conversion efficiency by 0.5 -1 at non knock-limited conditions

L'optimisation des positions de capteurs pour la détection du cliquetis dans les moteurs à explosion

In this study, we consider the problem of finding optimum sensor positions in a group of vibration sensors for knock detection. We propose a method that is less complex than holografic techniques because only signal processing and statistical tests are used . Our method is based on the linear prediction of an arbitrary sensor output from the remaining outputs in the sensor group. The relevancy of the sensor is thus characterized by the closeness to zero of the multiple coherence of its output with the remaining sensor outputs at some frequencies of interest . We choose a suitable statistic, approximate its distribution, and construct the generalized sequentially rejective Benferroni test. We have found in an experiment that the sensor position proposed by the engine manufacturer is not optimum . Experiments with a digital signal processor-based system emphasize the usefulness of this procedure . Through this procedure, we show that the performance of knock detectors strongly depends on the position of the sensor in use and can be improved significantly with moderate effort .Cette étude présente une approche permettant de déterminer les positions optimales de capteurs dans un groupe d'accéléromètres pour la détection du cliquetis dans un moteur à explosion. cette approche est moins complexe que les méthodes holographiques car nous utilisons uniquement le traitement du signal et des tests statistiques. La méthode proposée est basée sur la prédiction linéaire du signal à la sortie d'un capteur à partir des signaux obtenus aux sorties des autres capteurs du groupe. Ainsi, l'emplacement optimal d'un capteur est caractérisé par la proximité de zéro de la cohérence multiple aux fréquences intéressantes. Nous avons choisis une statistique appropriée, approximé sa loi de répartition et appliqué le test multiple à rejet séquentiel de Bonferron

Hydrogen-fueled internal combustion engines

The threat posed by climate change and the striving for security of energy supply are issues high on the political agenda these days. Governments are putting strate-gic plans in motion to decrease primary energy use, take carbon out of fuels and facilitate modal shifts. Taking a prominent place in these strategic plans is hydrogen as a future en-ergy carrier. A number of manufacturers are now leasing demonstration vehi-cles to consumers using hydrogen-fueled internal combustion engines (H2ICEs) as well as fuel cell vehicles. Developing countries in particular are pushing for H2ICEs (powering two- and three-wheelers as well as passenger cars and buses) to decrease local pollution at an affordable cost. This article offers a comprehensive overview of H2ICEs. Topics that are dis-cussed include fundamentals of the combustion of hydrogen, details on the differ-ent mixture formation strategies and their emissions characteristics, measures to convert existing vehicles, dedicated hydrogen engine features, a state of the art on increasing power output and efficiency while controlling emissions and modeling

ADAPTIVE MODEL BASED COMBUSTION PHASING CONTROL FOR MULTI FUEL SPARK IGNITION ENGINES

This research describes a physics-based control-oriented feed-forward model, combined with cylinder pressure feedback, to regulate combustion phasing in a spark-ignition engine operating on an unknown mix of fuels. This research may help enable internal combustion engines that are capable of on-the-fly adaptation to a wide range of fuels. These engines could; (1) facilitate a reduction in bio-fuel processing, (2) encourage locally-appropriate bio-fuels to reduce transportation, (3) allow new fuel formulations to enter the market with minimal infrastructure, and (4) enable engine adaptation to pump-to-pump fuel variations. These outcomes will help make bio-fuels cost-competitive with other transportation fuels, lessen dependence on traditional sources of energy, and reduce greenhouse gas emissions from automobiles; all of which are pivotal societal issues. Spark-ignition engines are equipped with a large number of control actuators to satisfy fuel economy targets and maintain regulated emissions compliance. The increased control flexibility also allows for adaptability to a wide range of fuel compositions, while maintaining efficient operation when input fuel is altered. Ignition timing control is of particular interest because it is the last control parameter prior to the combustion event, and significantly influences engine efficiency and emissions. Although Map-based ignition timing control and calibration routines are state of art, they become cumbersome when the number of control degrees of freedom increases are used in the engine. The increased system complexity motivates the use of model-based methods to minimize product development time and ensure calibration flexibility when the engine is altered during the design process. A closed loop model based ignition timing control algorithm is formulated with: 1) a feed forward fuel type sensitive combustion model to predict combustion duration from spark to 50% mass burned; 2) two virtual fuel property observers for octane number and laminar flame speed feedback; 3) an adaptive combustion phasing target model that is able to self-calibrate for wide range of fuel sources input. The proposed closed loop algorithm is experimentally validated in real time on the dynamometer. Satisfactory results are observed and conclusions are made that the closed loop approach is able to regulate combustion phasing for multi fuel adaptive SI engines

New signal processing techniques for enhanced knock detection in SI engines

Standard knock sensor signal processing typically consists of band-pass filtering followed by integration over a specified time/angular window. The resulting knock intensity serves as input to knock detection & correction part of an engine management system (ECU). While this treatment was initially performed by dedicated ICs, it has recently been implemented by ECU software, leading to a digital signal processing approach. In spite of some evident advantages of this approach, the processing method itself had not changed significantly. In this paper, the possibilities of taking better advantage of digital signal processing techniques are discussed and investigations on some possibilities for improving the overall knock detection performance by means of enhancing the signal processing techniques are presented

Numerical simulation for parametric study of a two -stroke compression ignition direct injection linear engine

A time based numerical simulation program was built at West Virginia University to simulate the operation of a two-stroke compression ignition direct injection linear engine. The two-stroke linear engine consists of two pistons connected together with a yoke and allowed to move freely according to the frequent combustion that takes place in response to fueling and load applied along the full stroke of the internal combustion engine. The simulating program used a series of dynamic and thermodynamic equations that were solved simultaneously to predict the performance and analyze the different factors affecting the operation of the two-stroke compression ignition linear engine coupled with linear alternator. This dissertation presents a dimensionless analysis parametric study to explore this novel type of internal combustion engine. It was found that these types of engines have a nature to build up compression ratio, and this was the reason behind recommending to operate such engines with high air to fuel ratios. Indicated efficiency was found to have an average of 42%. For stationary power generation a bore to effective stroke ratio equal to 1, or 1.3 would result in an efficient power generation unit whereas a bore to effective stroke length equal to three or four would result in a high-indicated power per cylinder volume, which may be suitable for automotive application. It was also found that a bore to effective stroke length of 2.2 would result in excessive compression ratio. This makes such a design limited to special applications where high indicated power per generator mass is needed. Advancing fuel injection close to the cylinder head during the compression stroke and burning the fuel with premixed to diffusive combustion ratio of 20% to 80% would enhance indicated efficiency and indicated power generated relative to injecting the fuel far from the cylinder head during the compression stroke and burning the fuel with premixed to diffusive combustion ratio of 40% to 60%

Characterization and Scaling Study of Energy Pathways in Small Four-Stroke Internal Combustion Engines

A study of the efficiency and energy losses of a selection of five small (40 - 200 cm3 displacement) single cylinder, four-stroke engines was accomplished. The study was performed as part of a larger effort to improve the range and endurance of small internal combustion engines (ICE) that power Group II Unmanned Aerial Vehicles (UAVs). Little is known about the performance, efficiency, and allocation of energy losses for four-stroke ICEs in this size range. The goal of the study was to characterize these parameters for use in future research efforts. Three research objectives were developed to guide the study contained herein. The first objective was to reliably measure the brake power output of each engine and compare the measurements to the manufacturers advertised power ratings. The second objective was to perform an energy balance, experimentally measuring the fuel energy entering the system (engine), and all of the energy exiting the system. Energy exiting the system was categorized as useable energy (brake power), or energy losses due to exhaust sensible enthalpy, thermal losses, or incomplete combustion. The third objective (which encompassed the first two) was to perform as series of parametric sweeps on the engines, examining the effect of varying engine speed, equivalence ratio, combustion phasing, cylinder head temperature, and throttle position. The characterization data from the five engines was then used to develop a set of correlations that could be used to predict brake mean effective pressure (BMEP), fuel conversion efficiency (nf), exhaust sensible enthalpy losses, thermal (cooling load) losses, and incomplete combustion losses as a percentage of fuel energy for small four-stroke engines with displacement volumes of 40 - 200 cm3. Accurate correlations for this size class currently do not exist in the literature