The subject of this diploma thesis is the creation of a spark ignition thermodynamics model using pressure data measured on the actual engine. The model made in Matlab programming language combines Wiebe function for fuel energy release and Woschni correlation for heat transfer between in-cylinder gasses and cylinder walls. The created model contains compression and expansion stroke only, that's why are conditions at the start of compression and total heat addition calculated by measured pressure data from Skoda 1.0 MPI engine. Creation of transparent model by Matlab scripts enables other users to understand the basics of „zero-dimensional“ thermodynamics models properly, which are used by number of commercial solvers such as GT-Power simulation software. First part of this thesis deals with fundamental laws of heat addition and heat transfer, description of equations for its modelling and application. The major section is devoted to Matlab model, where defined input parameters are mentioned, description of model operation and model parameters influence study. Next parts develops issues of combustion pressure measurement and creation of engine simulation by GT-Power software used for comparison with Matlab model. In the thesis conclusion are simulations and actual engine data differences discussed.

This paper deals with the problem of two-stroke engine pre-ignition controller with the use of microcontroller for single-cylinder engine and double-cylinder engine. The mechanical design is drawn for motorcycles JAWA and ČZ and for engines of the same mechanical type. The establishment uses non-contact status analysis of engine with non-electric sensor. The very important thing for the design is the simplicity of the establishment. The other important thing is the minimisation of mechanical arrangement of engine and the vehicle as a whole. The importance of this establishment is non-contact switching and the possibility of changing pre-ignition maps depending on the number of rotations per minute, the temperature and the load of the engine.

L'objectif de la thèse est d'étudier les mécanismes d'allumage d'un noyau de flamme en écoulements laminaires et turbulents. Dans un premier temps, une étude préliminaire est consacrée à l'analyse du dispositif d'allumage par étincelle induite par laser et à l'étude de l'initiation du noyau de flamme en écoulement laminaire prémélangé. Dans un second temps, l'étude de l'allumage est réalisée en écoulement turbulent prémélangé, afin de mettre en évidence l'effet des fluctuations turbulentes de vitesse sur l'initiation de noyau de flamme. Enfin, dans le cas d'un écoulement turbulent nonprémélangé, l'influence du champ local et instantané de fraction de mélange sur l'allumage et le développement du noyau de flamme est analysée. / The aim of the Ph-D thesis is to study ignition mechanisms of a flame kernel in laminar and turbulent flows. First, a preliminary study is devoted to the analysis of the laser-induced spark ignition system and to the study of the flame kernel initiation in premixed laminar flow. Then, the study of the ignition is performed in turbulent premixed flow, to highlight the influence of velocity turbulent fluctuations on the flame kernel initiation. Finally, in turbulent non-premixed flows, the effect of the local and instantaneous mixture fraction on the flame kernel initiation and development is analyzed.

<p>A variety of methods have been developed to enhance solid propellant burning rates, including adjusting oxidizer particle size, modifying metal additives, tailoring the propellant core geometry, and adding catalysts or wires. Fully consumable reactive wires embedded in propellant have been used to increase the burning rate by increasing the surface area; however, the manufacture of propellant grains and the observation of geometric effects with reactive components has been restricted by traditional manufacturing and viewing methods. In this work, a printable reactive filament was developed that is tailorable to a number of use cases spanning reactive fibers to photosensitive igniters. The filament employs aluminum fuel within a printable polyvinylidene fluoride matrix that can be tailored to a desired burning rate through stoichiometry or aluminum fuel configuration such as particle size and modified aluminum composites. The material is printable with fused filament fabrication, enabling access to more complex geometries such as spirals and branches that are inaccessible to traditionally cast reactive materials. However, additively manufacturing the reactive fluoropolymer and propellant together comes attendant with many challenges given the significantly different physical properties, particularly regarding adhesion. To circumvent the challenges posed by multiple printing techniques required for such dissimilar materials, the reactive fluoropolymer was included within a solid propellant carrier matrix as small fibers. The fibers were varied in aspect ratio (AR) and orientation, with aspect ratios greater than one exhibiting a self-alignment behavior in concordance with the prescribed extrusion direction. The effective burning rate of the propellant was improved nearly twofold with 10 wt.% reactive fibers with an AR of 7 and vertical orientation. </p> <p>The reactive wires and fibers in propellant proved difficult to image in realistic sample designs, given that traditional visible imaging techniques restrict the location and dimensions of the reactive wire due to the necessity of an intrusive window next to the wire, a single-view dynamic X-ray imaging technique was employed to analyze the evolution of the internal burning profile of propellant cast with embedded additively manufacture reactive components. To image complex branching geometries and propellant with multiple reactive components stacked within the same line of sight, the dynamic X-ray imaging technique was expanded to two views. Topographic reconstructions of propellants with multiple reactive fibers showed the evolution of the burning surface enhanced by the geometric effects caused by the faster burning fibers. These dual-view reconstructions provide a method for accurate quantitative analysis of volumetric burning rates that can improve the accessibility and viability of novel propellant grain designs.</p>

<p>In Chapter 2, an experiment has been developed to investigate the passive pre-chamber jet ignition process in gasoline engine configurations and low-load operating conditions. The apparatus adopted a modified 4-cylinder 2.0L gasoline engine to enable single-cylinder operation. To reduce the complexity, the piston position was fixed at a predefined position relative to the top dead center (TDC) to simulate thermodynamic conditions at ignition and injection timings. High-speed Infrared (IR) imaging was applied to visualize the jet penetration and ignition process inside the main cylinder and to investigate the cyclic spatial variability. Two passive pre-chambers with different total nozzle areas and numbers of nozzles were used. In addition, the pre-chamber volume and pressure at ignition timing were varied to examine their effect on jet ignition performance. Misfire behavior was observed in the main chamber of all test cases, and the results suggested that the main cause is a high Residual Mass Fraction (RMF) in the pre-chamber affecting the subsequent cycle. A larger total nozzle area, smaller volume, higher pressure, and fuel-lean operation tended to mitigate the misfire behavior. For a test case with a spark pressure of 6 bar, a reduced cyclic variability in terms of coefficient of variation peak cylinder pressure (COVPmax) from 10.03% to 7.38% and combustion phasing variation from 81 crank angle degree (CAD) to 12 CAD were observed with increasing pre-chamber volume-to-area (V/A) ratio from 59.37 m to 103.11 m, but slightly higher misfire frequency was observed, from 46.67% to 50.00%, suggesting an accurate combination of pre-chamber design parameters is needed to improve overall performance at low-load operation.</p> <p>In Chapter 3, it examines the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance. Utilizing a modified constant-volume gasoline direct injection engine with an optically-accessible piston, we tested three passive pre-chambers with nozzle diameters of 1.2, 1.4, and 1.6 mm, while nitrogen dilution varied from 0 to 20%. With the help of high-speed imaging, we captured pre-chamber jet formations and subsequent flame propagation within the main chamber. Our novel findings reveal that asymmetric temporal and spatial jet formation patterns arising from pre-chambers significantly impact engine performance. The larger nozzle diameter pre-chambers exhibited the least variation in jet formation due to their improved scavenging and main mixture filling processes, but had the slowest jet velocity and lowest jet penetration depth. At no dilution condition, the 1.2 mm-PC demonstrated superior performance attributed to higher pressure build-up in the pre-chamber, resulting in accelerated jet velocity and increased jet penetration depth. However, at high dilution condition, the 1.6 mm-PC performed better, highlighting the importance of scavenging and symmetry jet formation. This study emphasizes the importance of carefully selecting the pre-chamber nozzle diameter, based on the engine's operating conditions, to achieve an optimal and balanced configuration that can improve both jet formation and jet characteristics, as well as scavenging.</p> <p>In Chapter 4, it investigates the influence of passive pre-chamber nozzle diameter on jet ignition and subsequent main chamber combustion under varying load conditions and dilution levels using a constant-volume optical gasoline direct injection engine. The results reveal that as the load decreases, both fuel availability and flow conditions deteriorate, leading to delayed and inferior jet characteristics that affect main chamber ignition and combustion processes. In high and medium load conditions without dilution, the smallest nozzle diameter pre-chamber (1.2mm-PC) shows improved jet ignition and main combustion due to earlier jet ejection, enhanced penetration, and intensified jet. This is facilitated by the smaller nozzle diameter enabling faster and higher pre-chamber pressurization. Conversely, under low load conditions, the largest nozzle diameter pre-chamber (1.6mm-PC) performs better, likely due to improved scavenging and reduced residual levels, resulting in less compromised pre-chamber combustion and subsequent jet characteristics. The nozzle diameter also has a significant impact on cycle-to-cycle variations, with smaller diameters enhancing jet ignition performance but increasing variability. The effect of external residuals (dilution) on jet ignition performance varies depending on the nozzle diameter, with the 1.6mm-PC exhibiting less degradation and demonstrating earlier jet ejection and CA50 timing compared to smaller nozzle diameter pre-chambers at higher dilution conditions. The improved scavenging and relatively lower residual levels in the larger nozzle diameter pre-chamber contribute to its increased resistance to dilution and potential extension of dilution tolerance.</p> <p>In Chapter 5, it presents an analysis of the effects of pre-chamber nozzle orientation on dilution tolerance in a constant-volume optical engine. Using a combination of experimental and numerical methodologies, we provide novel insights into how variations in nozzle number, orientation, and size influence combustion performance under different dilution conditions. The findings reveal that an increase in the number of nozzles, for a fixed A/V ratio, tends to enhance ignition performance and stability across a range of dilution scenarios, primarily due to an increase in ignition points and a larger ignition surface area. Meanwhile, swirling pre-chambers, despite their potential to boost initial combustion performance at no dilution condition, may limit dilution tolerance due to the complexity of their internal flow dynamics and increased heat loss through nozzle surfaces. Furthermore, pre-chambers combining swirling and straight nozzle orientations fail to synergize the benefits of each type, and instead, exacerbate challenges such as heat loss, flame quenching, and unfavorable flow dynamics. These findings emphasize the complexity and nuanced trade-offs involved in optimizing pre-chamber design for improved dilution tolerance and suggest potential directions for future research in this area.</p> <p>In Chapter 6, it investigates the behavior of pre-chamber knock in comparison to traditional spark ignition engine knock, using a modified constant-volume gasoline engine with an optically-accessible piston. The aim is to provide a deeper understanding of pre-chamber knock combustion and its potential for mitigating knock. Five passive pre-chambers with different nozzle diameters, volumes, and nozzle numbers were tested, and nitrogen dilution was varied from 0 to 10%. The stochastic nature of knock behavior necessitates the use of statistical methods, leading to the proposal of a high-frequency band-pass filter (37-43 kHz) as an alternative pre-chamber knock metric. Pre-chamber knock combustion was found to exhibit fewer strong knock cycles compared to SI engines, indicating its potential for mitigating knock intensity. High-speed images revealed pre-chamber knock primarily occurs near the liner, where end-gas knock is typically exhibited. The study identified that increasing pre-chamber nozzle diameter resulted in a larger dispersion of knock cycles and more severe knock intensity, likely due to shorter jet penetration depth requiring more time for end-gas consumption. Strategies for mitigating knock in pre-chamber combustion systems include reducing the pre-chamber volume for a fixed A/V ratio and increasing dilution level. The results of this study offer valuable insights for developing effective knock mitigation approaches in pre-chamber combustion systems, contributing to the advancement of more efficient and reliable engines.</p> <p>In Chapter 7, a numerical investigation of different premixed gaseous injection strategies was performed to understand their impact on the scavenging and mixture formation of an air-fuel premixed pre-chamber with high exhaust gas recirculation (EGR) operations. EGR dilution is effective for reducing coolant heat loss, pumping work at throttled conditions, and mitigates knock at high-load conditions, thus increasing engine efficiency. To further extend the EGR limit of an air-fuel premixed pre-chamber engine, the effects of different injection strategies (including timing, duration, pressure, pre-chamber volume, and hardware) on the EGR level, trap efficiency, and parasitic loss were determined. Regardless of injection duration and upstream pressure, injecting too early not only increased the amount of the injected premixed gas leaking into the main chamber but also was inefficient in reducing the EGR level in the pre-chamber. To reduce the EGR level in the pre-chamber to a level where successful ignition and combustion of the pre-chamber mixture is possible, the injection timing should be delayed to be close to the ignition timing. A premixed air-fuel injection is thus proposed to reduce the time required for air-fuel mixing in the pre-chamber. With a delayed end of injection (EOI), both leakage amount and EGR level were reduced compared to the cases with earlier injection timings. The results show that an injection with 15 bar upstream pressure, 20 CA duration, EOI of −20 CAD aTDC (ignition timing), and with guided injection hardware for the base pre-chamber volume resulted in about 0.17% air compression parasitic loss, over a 94% trap efficiency, at the same time maintaining the mean EGR level in the pre-chamber below 20%, ensuring good pre-chamber combustion. With a 50% increase in pre-chamber volume from the base case, the parasitic loss increased by 65% (from 0.17% to 0.28% loss), indicating a problem with a larger pre-chamber with a separate air valve and injector.</p>

No description available.

<div>The commercial vehicle sector is an important enabler of the economy and is heavily dependent on fossil fuels. In the fight against climate change, reduction of emissions by improving fuel economy is a key step for the commercial vehicle sector. Improving fuel economy deals with reducing energy losses from fuel to the wheels. This study aims to analyze efficiency improvements for two systems that are important in reducing CO2 emissions - hybrid powertrains and natural gas engines. At first, a prototype series hybrid powertrain was analyzed based on on-highway data collected from its powertrain components. Work done per mile by the electrical components of the powertrain showed inefficient battery operation. The net energy delivery of the battery was close to zero at the end of the runs. This indicated battery was majorly used as an energy storage device. Roughly 15% of losses were observed in the power electronics to supply power from battery and generator to the motor. Ability of the hybrid system to capture regenerative energy and utilize it to propel the vehicle is a primary cause for fuel savings. The ability of this system to capture the regenerative energy was studied by modeling the system. The vehicle model demonstrated that the system was capturing most of the theoretically available regenerative energy. The thesis also demonstrates the possibility of reduction of vehicular level losses for the prototype truck. Drag and rolling resistance coefficients were estimated based on two coast down tests conducted. The ratio of captured regenerative to the drive energy energy for estimated drag and rolling resistant coefficients showed that the current system utilizes 4%-9% of its drive energy from the captured regenerative energy. Whereas a low mileage Peterbilt 579 truck could increase the energy capture ratio to 8%-18% for the same drive profile and route. Decrease in the truck’s aerodynamic drag and rolling resistance can potentially improve the fuel benefits.</div><div>The second study aimed to reduce the engine level pumping losses for a natural gas spark ignition engine by cylinder deactivation (CDA). Spark ignited stoichiometric engines with an intake throttle valve encounter pumping/throttling losses at low speed, low loads due to the restriction of intake air by the throttle body. A simulation study for CDA on a six cylinder natural gas engine model was performed in GT- Power. The simulations were ran for steady state operating points with a torque range 25-560 ftlbs and 1600 rpm. Two , three and four cylinders were deactivated in the simulation study. CDA showed significant fuel benefits with increase in brake thermal efficiency and reduction in brake specific fuel consumption depending on the number of deactivated cylinders. The fuel benefits tend to decrease with increase in torque. Engine cycle efficiencies were analyzed to investigate the efficiency improvements. The open cycle efficiency is the main contributor to the overall increase in the brake thermal efficiency. The work done by the engine to overcome the gas exchange during the intake and exhaust stroke is referred to the pumping losses. The reduction in pumping losses cause an improvement in the open cycle efficiency. By deactivating cylinders, the engine meets its low torque requirements by increase in the intake manifold pressure. Increased intake manifold pressure also resulted in reduction of the pumping loop indicating reduced pumping losses. A major limitation of the CDA strategy was ability to meet EGR fraction requirements. The increase in intake manifold pressure also caused a reduction in the delta pressure across the EGR valve. At higher torques with high EGR requirements CDA strategy was unable to meet the required EGR fraction targets. This limited the benefits of CDA to a specific torque range based on the number of deactivated cylinders. Some variable valve actuation strategies were suggested to overcome this challenge and extend the benefits of CDA for a greater torque range.</div><div><br></div>

[pt] O desempenho de veículos automotivos é um importante atributo a ser avaliado quando motores de combustão interna e novos combustíveis estão sendo desenvolvidos. A previsão desse parâmetro também é de suma importância, uma vez que os testes de desempenho de automóveis em pista requerem prazos de realização e altos custos com equipamentos, aluguel da pista, contratação de pessoas e deslocamento de veículos e combustíveis. Além disso, seus resultados são diretamente afetados por irregularidades na superfície da pista e variações nas condições climáticas, como pressão ambiente, temperatura, umidade do ar e velocidade do vento. Assim, este trabalho tem como objetivo utilizar os dados coletados em testes de bancada com um motor de combustão interna com a finalidade de modelar os testes de retomada de velocidade de um automóvel convencional leve. A metodologia proposta simula a força de tração nas rodas a partir do torque medido no dinamômetro do motor ou a partir das curvas de pressão no interior da câmara de combustão com o auxílio de modelos de atrito para motores de ignição por centelha. Para validar o modelo proposto, foi necessário realizar testes de retomada de velocidade com o carro em um dinamômetro de chassi. Além disso, foram utilizadas sete misturas diferentes de etanol e gasolina, e concluiu-se que o etanol anidro puro promoveu maior capacidade de aceleração na maioria dos experimentos, mas apresentou maior consumo de combustível. Os combustíveis hidratados reduziram o desempenho, mas melhoraram a eficiência global. As simulações demonstraram alta precisão em relação ao experimento, com média da diferença do tempo de recuperação da velocidade de 0,51 segundos e desvio padrão de 0,078. Além disso, as simulações de desempenho de aceleração tiveram erros menores que 5,25 por cento. Além disso, a realização desses testes em laboratório tem a vantagem de um maior controle das condições ambientais da sala e dos parâmetros de operação do motor. / [en] Vehicle performance is an important feature to be evaluated when internal combustion engines and new fuels are being developed. Predicting this parameter is also of great significance, once track testing requires long periods of time to be done and high costs with equipment, rental of the track, hiring people and displacement of vehicles and fuels. In addition, their results are directly affected by track surface irregularities and variations in weather conditions such as ambient pressure, temperature, air humidity and wind speed. Thus, this work aims to use collected data in bench tests with an internal combustion engine in order to modeling an automobile speed recovery time. The proposed methodology simulates the traction force on the wheels based on the measured torque in engine dynamometer or from the pressure curves inside the combustion chamber with the aid of friction models for spark ignition engines. In order to validate the proposed model, it became necessary to perform speed recovery tests with the car on a chassis dynamometer. Also, seven different mixtures of ethanol and gasoline were used, and it was concluded that pure anhydrous ethanol promoted a higher acceleration capacity in most of the experiments but it had higher fuel consumption. Hydrated fuels reduced performance but improved global efficiency. The simulations demonstrated a high precision in relation to the experiment, with a speed recovery time diference average of 0.51 seconds and standard deviation of 0.078. Also, the acceleration performance simulations had errors smaller than 5.25 percent. In addition, doing these tests in laboratory has the advantage of a greater control of the room ambient conditions and the engine operating parameters.

In this thesis, exergy based SI engine model optimisation (EBSIEMO) is studied and evaluated. A four-stroke bi-fuel spark ignition (SI) engine is modelled for optimisation of engine performance based upon exergy analysis. An artificial neural network (ANN) is used as an emulator to speed up the optimisation processes. Constrained particle swarm optimisation (CPSO) is employed to identify parameters such as equivalence ratio and ignition time for optimising of the engine performance, based upon maximising ¿total availability¿. In the optimisation process, the engine exhaust gases standard emission were applied including brake specific CO (BSCO) and brake specific NOx (BSNOx) as the constraints. The engine model is developed in a two-zone model, while considering the chemical synthesis of fuel, including 10 chemical species. A computer code is developed in MATLAB software to solve the equations for the prediction of temperature and pressure of the mixture in each stage (compression stroke, combustion process and expansion stroke). In addition, Intake and exhaust processes are calculated using an approximation method. This model has the ability to simulate turbulent combustion and compared to computational fluid dynamic (CFD) models it is computationally faster and efficient. The selective outputs are cylinder temperature and pressure, heat transfer, brake work, brake thermal and volumetric efficiency, brake torque, brake power (BP), brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). In this model, the effect of engine speed, equivalence ratio and ignition time on performance parameters using gasoline and CNG fuels are analysed. In addition, the model is validated by experimental data using the results obtained from bi-fuel engine tests. Therefore, this engine model was capable to predict, analyse and useful for optimisation of the engine performance parameters. The exergy based four-stroke bi-fuel (CNG and gasoline) spark ignition (SI) engine model (EBSIEM) here is used for analysis of bi-fuel SI engines. Since, the first law of thermodynamic (the FLT), alone is not able to afford an appropriate comprehension into engine operations. Therefore, this thesis concentrates on the SI engine operation investigation using the developed engine model by the second law of thermodynamic (the SLT) or exergy analysis outlook (exergy based SI engine model (EBSIEM)) In this thesis, an efficient approach is presented for the prediction of total availability, brake specific CO (BSCO), brake specific NOx (BSNOx) and brake torque for bi-fuel engine (CNG and gasoline) using an artificial neural network (ANN) model based on exergy based SI engine (EBSIEM) (ANN-EBSIEM) as an emulator to speed up the optimisation processes. In the other words, the use of a well trained an ANN is ordinarily much faster than mathematical models or conventional simulation programs for prediction. The constrained particle swarm optimisation (CPSO)-EBSIEM (EBSIEMO) was capable of optimising the model parameters for the engine performance. The optimisation results based upon availability analysis (the SLT) due to analysing availability terms, specifically availability destruction (that measured engine irreversibilties) are more regarded with higher priority compared to the FLT analysis. In this thesis, exergy based SI engine model optimisation (EBSIEMO) is studied and evaluated. A four-stroke bi-fuel spark ignition (SI) engine is modelled for optimisation of engine performance based upon exergy analysis. An artificial neural network (ANN) is used as an emulator to speed up the optimisation processes. Constrained particle swarm optimisation (CPSO) is employed to identify parameters such as equivalence ratio and ignition time for optimising of the engine performance, based upon maximising ¿total availability¿. In the optimisation process, the engine exhaust gases standard emission were applied including brake specific CO (BSCO) and brake specific NOx (BSNOx) as the constraints. The engine model is developed in a two-zone model, while considering the chemical synthesis of fuel, including 10 chemical species. A computer code is developed in MATLAB software to solve the equations for the prediction of temperature and pressure of the mixture in each stage (compression stroke, combustion process and expansion stroke). In addition, Intake and exhaust processes are calculated using an approximation method. This model has the ability to simulate turbulent combustion and compared to computational fluid dynamic (CFD) models it is computationally faster and efficient. The selective outputs are cylinder temperature and pressure, heat transfer, brake work, brake thermal and volumetric efficiency, brake torque, brake power (BP), brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). In this model, the effect of engine speed, equivalence ratio and ignition time on performance parameters using gasoline and CNG fuels are analysed. In addition, the model is validated by experimental data using the results obtained from bi-fuel engine tests. Therefore, this engine model was capable to predict, analyse and useful for optimisation of the engine performance parameters. The exergy based four-stroke bi-fuel (CNG and gasoline) spark ignition (SI) engine model (EBSIEM) here is used for analysis of bi-fuel SI engines. Since, the first law of thermodynamic (the FLT), alone is not able to afford an appropriate comprehension into engine operations. Therefore, this thesis concentrates on the SI engine operation investigation using the developed engine model by the second law of thermodynamic (the SLT) or exergy analysis outlook (exergy based SI engine model (EBSIEM)) In this thesis, an efficient approach is presented for the prediction of total availability, brake specific CO (BSCO), brake specific NOx (BSNOx) and brake torque for bi-fuel engine (CNG and gasoline) using an artificial neural network (ANN) model based on exergy based SI engine (EBSIEM) (ANN-EBSIEM) as an emulator to speed up the optimisation processes. In the other words, the use of a well trained an ANN is ordinarily much faster than mathematical models or conventional simulation programs for prediction. The constrained particle swarm optimisation (CPSO)-EBSIEM (EBSIEMO) was capable of optimising the model parameters for the engine performance. The optimisation results based upon availability analysis (the SLT) due to analysing availability terms, specifically availability destruction (that measured engine irreversibilties) are more regarded with higher priority compared to the FLT analysis.

No description available.