Combustion Process In Engine Research Articles

Mixture formation and combustion process of a biodiesel fueled direct injection rotary engine (DIRE) considering injection timing, spark timing and equivalence ratio – CFD study

Rotary engine has a flat combustion chamber that results in high unburned fuel leading to fuel inefficiency and emissions. Biodiesel regarded as a clean source of energy is an alternative fuel due to its ability to minimize environmental pollution resulting from unwanted emissions. In this regard, the improvement of combustion efficiency of a direct injection rotary engine fueled with biodiesel was numerically investigated. Experimental data was used in validating the established three-dimensional computational fluid dynamics (3D-CFD) model. On this basis, investigation of various biodiesel injection timing (IT) (100, 80, 60) °CA before top dead center (BTDC), spark timing (ST) (35, 30, 25, 20) °CA BTDC and equivalence ratios (∅) (0.6, 0.8, 1.0, 1.2) on mixture formation and combustion process was carried out. Results revealed that when IT retarded fuel distribution narrows and the mixture formed is concentrated. Conversely when ST retarded there is broad and dispersed fuel distribution. For lean condition the mixture formed is less concentrated compared to rich condition. For combustion process, when biodiesel was concentrated at the middle of in-cylinder at 30 mm (X-axis) and 15 mm (Z-axis) from the centerline in opposing directions it was better for spark-on. Also, the in-cylinder pressure and temperature reduced with advanced IT, retarded ST and decreased ∅. When ∅ leaned, flame development and propagation periods decreased. The suitable rate for combustion considering emissions was obtained when IT was 80°CA (BTDC) and ST 35°CA (BTDC) at a ∅ of 0.8 because when compared to the original scheme (case B4), maximum combustion pressure increased by 28.57% and increase of CO2, CO, soot and NO emissions were reasonable due to increase in temperature and fuel evaporation.

Characterizing Two-Stage Combustion Process in a Natural Gas Spark Ignition Engine Based on Multi-Wiebe Function Model

Abstract The Wiebe function is a simple and cost-effective analytical approach to approximate the burn rates in internal combustion (IC) engines. Previous studies indicated that a double-Wiebe function model can better describe the two-stage combustion process inside diesel engines retrofitted to natural gas (NG) spark ignition (SI) compared with a single-Wiebe function. Specifically, the two Wiebe functions are associated with the bowl burn and the squish burn. However, the long tail in the energy release at the end of combustion produces some differences between experiment and model, which can be attributed to the complexity of the late oxidation process inside the post-flame zone and the incomplete combustion of the unburned mixture flowing out from engine crevices. To improve the matching between the model and experimental data, this paper investigated the effect of adding a third Wiebe function just to describe the long tail in the energy release at the end of combustion. The results indicated that such a methodology greatly improved the fitting accuracy in terms of phasing and magnitude of the heat release rate in each combustion stage.

Indicators of the diesel engine combustion process when working on methanol with DST depending on the load changes in different operating modes

In the Vyatka state agricultural Academy, on the basis of the Department of heat engines, cars and tractors, the development of a 2CH 10.5/12.0 diesel engine for working on methanol using a dual fuel supply system was carried out. The paper presents an analysis of the parameters of the 2CH 10.5/12.0 diesel combustion process depending on the load change at the nominal speed and at the crankshaft rotation speed at maximum torque when working on diesel fuel and methanol with a dual fuel supply system.

The Effect of Heating of B20 Fuel to Combustion Characteristic on the Diesel Engine Based on Experiment

A ccording to Bank Indonesia, the current account deficit of Indonesia. In the second quarter of 2018 increased to USD 8.0 billion. One of the government's programs to reduce the current account deficit is by implementing a B20 biodiesel policy. The increasing percentage of biodiesel in fuel blends tends to decrease the quality of spray atomization, where it indicated by longer droplet breakup, spray penetration, droplet lifetime, and bigger droplet diameter. Higher viscosity causes a decrease in the quality of the spray from the injector. Previous research shows that the inlet temperature of the fuel can make the performance of small diesel engines slightly better. The research was conducted using petrodiesel and biodiesel fuel by varying inlet temperature of 50 o C and 70 o C. Based on that this research is conducted to understand the effect of fuel heating diesel engine combustion process. The result shows that generally maximum pressure is increased for every increase in fuel temperature. The heat release shows a decreasing trend for every increase in fuel temperature. Knock detection shows that generally when the fuel temperature increased the knocking is also increased. The increasing fuel temperature shows little effect on ignition delay except for the higher temperature of 60 o C and 70 o C where the ignition delay is the lowest and closest to that of a dexlite fuel.

Simulation Study on the Impact of Uneven Fuel Injection of Each Hole of the Diesel Engine Injector on the Combustion Process

The spray impulse and injection pressure of each hole of the 4-hole injector of F186 engine were tested by using the transient test system for flow coefficient and injection rate of each hole of the injector, and the injection rate, fuel injection quantity and flow coefficient of each hole were obtained. According to the measured injection rate of each hole and cycle fuel injection quantity, a 3D model of the diesel engine was established with the FIRE software, and the uniform injection rate and uneven injection rate of each hole were made as the injection setting for the combustion simulation to comparatively analyze the influence of the uneven injection rate of each hole on the combustion process of diesel engine. As the injection of each hole is uneven, some holes with high injection rate have long fuel spray penetration distance and the fuel spray is fully mixed with the air, and the ignition starting point is moved ahead. When compared with the case of uniform injection rate, the phase corresponding to the heat release rate in the case of uneven injection rate is moved forwards, the maximum cylinder pressure and temperature rise fast, the maximum cylinder pressure and maximum average temperature in cylinder are higher, the NO generation is larger, and the Soot generation is slightly larger. In the case of uneven injection rate from four holes, as the utilization of air in the hole-located cylinder space by the fuel spray is uneven, the hole with a large quantity of injection makes the oxygen in the hole-located cylinder space relatively low, the wall collision of the hole with high injection rate is more, and the diffusion combustion is incomplete and insufficient.

Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine

It is difficult to decompose the in-cylinder pressure of combustion of the direct injection (DI) diesel engine, a transient process associated with complicated oscillation components, because of its steep property. An adaptive cyclic average method based on time varying filter based empirical mode decomposition (TVF-EMD) is proposed to decompose the in-cylinder pressure signal, and the cyclic number is determined adaptively with protruding ratio of high-frequency oscillation. The proposed method is used to compare with the ensemble empirical mode decomposition and original TVF-EMD. The results indicate that the proposed method can overcome the drawbacks of these methods and extract high-frequency oscillations accurately and effectively. Three evaluation indexes, center frequency, normalized energy, and average center frequency are defined to analyze the frequency and energy characteristics of high-frequency oscillation quantitatively. The influence of speed, load, rail pressure, main injection timing, pilot injection interval, and pilot injection quantity are investigated systematically. The energy of high-frequency oscillation reaches the peak at medium-high speed, and increase with engine load and rail pressure. However, the relationship of high-frequency oscillation with fuel injection parameters are non-monotonic.

Effects of ethanol injection strategies on mixture formation and combustion process in an ethanol direct injection (EDI) plus gasoline port injection (GPI) spark-ignition engine

The mixture formation process is vital for ethanol direct injection (EDI) plus gasoline port injection (GPI) engine, as the mixture preparation quality directly affects the combustion process and emission characteristics, especially for the dual-injection system. In this study, engine tests were first conducted to investigate the effects of ethanol injection timings (430 °CA, 570 °CA, 620 °CA and 670 °CA) and injection pressures (40 bar, 60 bar and 90 bar) on engine performance and combustion process. Then, the numerical simulations were performed with the focus on detailed mixture formation process, including in-cylinder flows, wall wetting and fuel evaporation. The experimental and numerical results indicated that the injection timing has a significant effect on the mixture formation in EDI + GPI engine. Due to the long evaporation time and strong in-cylinder TKE, early injection timing (430 °CA) can lead to a uniform mixture and complete combustion. The effect of ethanol injection pressure on mixture formation was not significant at this ethanol injection timing. As the injection timing was retarded, due to the reduced evaporation time, the formation of the homogeneous mixture became harder, and the effect of injection pressure on the mixture preparation became obvious. At injection timing of 620 °CA, high injection pressure generated high fuel spray momentum, which deformed the original in-cylinder vortex, and more ethanol fuel collided on the piston surface and the wall, resulting in uneven distribution of the mixture and poor combustion. When the injection timing was retarded to 670 °CA, the injection pressure of 60 bar could obtain a good balance among the fuel evaporate rate, the amount fuel impinging on the wall and the fuel evaporation time, resulting more complete combustion.

Combustion and Emission Characteristics of a Biodiesel-Hydrogen Dual-Fuel Engine

The paper presents the results of co-combustion of biodiesel with hydrogen in a compression-ignition internal combustion engine. The tests were carried out on a stationary engine with constant settings. The paper presents the results of the assessment of the combustion process, combustion stability and exhaust emissions in a dual-fuel diesel engine fueled with biodiesel and hydrogen. It was found that it is possible to replace biodiesel with hydrogen to its energetic share of 38%. The share of hydrogen in the co-combustion process causes a change in combustion phases and reducing the duration of combustion. The increase of the engine thermal efficiency was obtained with the increase of the H2 share. A different character of heat release rate was obtained compared to a conventional engine. The reduction in the diffusion combustion phase has contributed to a significant reduction in soot emissions. The maximum 38% of hydrogen energy share acceptable by the engine, resulted in a more than 25-times reduction in soot emissions. The combustion stability assessed on the basis of the unrepeatability of the indicated mean effective pressure (COVIMEP) index and also on the basis of the indicated mean effective pressure (IMEP) normal distribution was also analyzed.

Study on combustion and emission of Biodiesel Engine with different angle of oil beam

In order to reduce the excess pollutants caused by environmental factors, on the basis of the installation of post-treatment device, through the use of converse software, the simulation research on the combustion process of non road diesel engines in the cylinder was carried out in the cold environment, and the combustion processed and emission reduction of diesel engine were optimized under the condition of only changing the angle of oil beam. The results show that the temperature in cylinders is the highest, and the pressure in the cylinder is larger, the equivalence ratio and eddy current intensity in cylinder are stronger, the emissions are lower, and the emissions of NOx and soot are the lowest under the angle of 164° fuel beam.

Sind Kraftfahrzeuge mit Dieselmotoren noch tolerabel?

Are vehicles with diesel engines still acceptable? Emissions from diesel engines are made up of hundreds of components, some in the form of particles and some gaseous. In 2002, the IARC classed diesel engine exhaust as carcinogenic to humans. Research in the workplace and studies on test persons showed inflammatory responses in the lungs, asthmatic responses and cardiovascular effects. The health implications of emissions have been in the public spotlight since the diesel scandal of 2015 and have called into question the acceptance of diesel engine technology. The optimisation of combustion processes in engines and exhaust gas treatment systems have nevertheless made it possible to reduce substantially the substances in exhaust over the last 20 years. In addition, the new test cycles are a practical way of monitoring emissions. The EURO 6 standard means that there is now virtually no difference between the emissions from diesel and petrol engines in newly registered vehicles, although diesel engines consume 15-20% less fuel than petrol engines. Keywords: diesel engines – emissions – carcinogenicity – diesel scandal

Combustion and Performance Study of Low-Displacement Compression Ignition Engines Operating with Diesel–Biodiesel Blends

This study investigated the influence of different biodiesel blends produced from residual sunflower oil and palm oil from agroindustry liquid waste on the characteristics of the combustion process, performance, and emissions in a single-cylinder diesel engine. For the analysis of the combustion process, a diagnostic model was developed based on the cylinder pressure signal, which allows the calculation of the heat release rate, the accumulated heat rate, and the temperature in the combustion chamber. This is to assess the influence of these parameters on engine emissions. The experiments on the diesel engine were carried out using five types of fuel: conventional diesel, two biodiesel blends of residual palm oil (PB5 and PB10), and two biodiesel blends formed with palm oil and sunflower oil residues (PB5SB5 and PB10SB5). The engine was running in four different modes, which covered its entire operating area. Experimental results show that the in-cylinder pressure curves decrease as the percentage of biodiesel in the fuel increases. Similarly, the results showed a decrease in the heat release rate for biodiesel blends. The diagrams of the accumulated heat release curves were larger for fuels with higher biodiesel content. This effect is reflected in the thermal efficiency of biodiesel blends since the maximum thermal efficiencies were 29.4%, 30%, 30.6%, 31.2%, and 31.8% for PB10SB5, PB5SB5, PB10, PB5, and diesel, respectively. The emission analysis showed that the blends of biodiesel PB5SB5 and PB10SB allowed a greater reduction in the emissions of CO, CO2, HC, and opacity of smoke in all the modes of operation tested, in comparison with the blends of biodiesel PB5 and PB10. However, NOx emissions increased. In general, biodiesel with the percentage of residual sunflower oil does not cause a significant change in the combustion process and engine performance, when compared to biodiesel that includes only residual palm oil.

Large-eddy simulation study on cycle-to-cycle variation of knocking combustion in a spark-ignition engine

The cycle-to-cycle variation in the knock intensity is commonly encountered under abnormal combustion conditions. The severity of these abnormal combustion events can vary significantly, and the efficiency of engines at high loads is limited in practice by heavy knocking phenomena. Since, a thorough analysis of such recurrent but non-cyclic phenomena via experiments alone becomes highly cumbersome, in the present work, a multi-cycle large-eddy simulation study was performed to quantitatively predict cyclic variability in the combustion process and cyclic knock intensity variability in a direct injection spark-ignition engine. To account for the turbulence-chemistry interaction effects on flame propagation, the G-equation combustion model was used. Detailed chemistry was solved outside the flame front with a toluene primary reference fuel skeletal kinetic mechanism. For both the mild knock and heavy knock conditions, the numerical results were validated against experimental measurements. Based on the simulation results, a correlation analysis was performed considering combustion phasing, peak cylinder pressure and maximum amplitude of pressure oscillation. Furthermore, a detailed three-dimensional spatial analysis illustrated the evolution of auto-ignition kernel development and propagation of pressure waves during knocking combustion for three typical cycles with different knock intensities. It was found that an early occurrence of auto-ignition in the end gas was prone to high knock intensity. Although multiple auto-ignition kernels were observed in different cycles, the degree of coupling between chemical heat release and pressure waves varied, thereby leading to different maximum amplitude of pressure oscillation values.

Effects of boiling heat transfer on the performance enhancement of a medium speed diesel engine fueled with diesel and rapeseed methyl ester

In order to better evaluate the nucleate boiling heat transfer, a new heat transfer model is developed in the AVL-Boost environment. The improved heat transfer model considers the influence of boiling heat transfer in the cylinder-jacket of diesel engine. The combustion process of diesel engine fueled with diesel and rapeseed methyl ester is calculated by an improved chemical kinetics mechanism, which consists of 475 reactions and 134 species. In addition, the effects of boiling heat transfer in cylinder-jacket on performance and emission characteristics of diesel engine are investigated. The result shows that the improved model with considering the boiling heat transfer in the cylinder-jacket agrees better with the experimental result compared with the model without considering the boiling heat transfer. In addition, the perturbation sensitivity analysis of each parameter such as fuel injection pressure, exhaust gas recirculation, injection quantity, injection timing, fuel injection duration, compression ratio, inlet air pressure and inlet air temperature on diesel engine characteristic is investigated by a perturbation method. Finally, the most influential parameter of diesel engine on outputs of diesel engine is investigated and obtained.

Modeling heavy-duty diesel engines using tabulated kinetics in a wide range of operating conditions

Fast and high-fidelity combustion models including detailed kinetics and turbulence chemistry interaction are necessary to support design and development of heavy-duty diesel engines. In this work, the authors intend to present and validate tabulated flamelet progress variable model based on tabulation of laminar diffusion flamelets for different scalar dissipation rate, whose predictability highly depends on the description of fuel–air mixing process in which engine mesh layout plays an important role. To this end, two grids were compared and assessed: in both grids, cells were aligned on the spray direction with such region being enlarged in the second one, where the near-nozzle and near-wall mesh resolution were also improved, which is expected to better account for both spray dynamics and flame–wall interaction dominating the combustion process in diesel engines. Flame structure, in-cylinder pressure, apparent heat release rate, and emissions for different relevant operating points were compared and analyzed to identify the most suitable mesh. Afterwards, simulations were carried out in a heavy-duty engine considering 20 operating points, allowing to comprehensively verify the validity of tabulated flamelet progress variable model. The results demonstrated that the proposed approach was capable to accurately predict in-cylinder pressure evolution and NO x formation across a wide engine map.

Visualization Research and Optimization Strategy for Combustion Process and Emission Characteristics of Internal Exhaust Gas Recirculation Small Non-Road Diesel Engine

Based on a small non-road diesel engine, internal exhaust gas recirculation (IEGR) was realized by the exhaust valve re-opening (2EVO). The influences of IEGR on combustion and emission performance were analyzed. The results showed that in-cylinder pressure peak decreased, the start of heat release was delayed by 0.5 oCA and the heat release rate peak was reduced after the introduction of IEGR. Furthermore, the average temperature of combustion flame was reduced, centering between 1900 and 2100 K. That was beneficial to curbed nitrogen oxides (NOX) emissions. The average value for KL factor was obviously increased within the entire range of combustion, which resulting in an increase in soot emission. In terms of emission characteristics, NOX emission was significantly reduced under the original injection timing but soot emission was increased slightly. Subsequently, the start of injection (SOI) were adjusted based on IEGR and two fuel injection control strategies were formulated from the perspective of reducing pollutant emissions and fuel consumption: Strategy 1 keeping BSFC consistent with the original engine, the NOX+HC weighted emission was reduced by 17.6 %; Strategy 2 keeping NOX+HC emissions consistent with the original engine, BSFC and CO were reduced by 10 % and 20 % respectively and Soot emission was slightly increased.

Ion Sensor-Based Measurement Systems: Application to Combustion Monitoring in Gas Turbines

Ionic density measurement in the burning gases is one of the techniques used to obtain information about the combustion process in automotive engines. In this article, the possibility of using a similar approach for the combustion monitoring of gas turbine combustors is considered. In particular, the potentiality of this measurement technique is investigated by modeling the problem, and analyzing the data obtained in a preliminary set of measurements with different operative conditions.

Experimental research on effects of biodiesel fuel combustion flame temperature on NOX formation based on endoscope high-speed photography

Biodiesel has the potential to be used as an alternative to diesel fuel, while NOX emissions from biodiesel engine are higher than those of diesel engine. According to the Zeldovich mechanism, thermal NO is the main pathway for NOX formation. Therefore, studying the temperature of biodiesel combustion flame is of great significance for understanding the formation mechanism of NOX. Hence, this paper is devoted to the investigation of effects of biodiesel combustion flame temperature on NOX formation by using Endoscope high-speed photography. The experimental work has been carried out on a diesel engine fueled with three different blending-ratios of biodiesel/diesel fuel (B0, B50, B100). The image of the engine combustion process was captured by high-speed endoscopic photography, and the flame temperature field distribution was calculated based on the brightness of the in-cylinder combustion flame image. The parameters of in-cylinder flame temperature and their changing laws with engine speed and blending-ratios were also analyzed by using six indicators, such as NOX formation flame area (SNO), flame area change velocity (VNO), mean flame area change velocity (VNOM), flame area duration (ϕNO), flame appearance efficiency (ηNO) and adiabatic flame temperature (TP). Results showed that with the increase of biodiesel fuel proportion, the positions of SNOappearance and disappearance were advanced, the peak values of SNO,VNOVNOM, ηNObecame greater, andϕNObecame shorter, which indicated that more beneficial environment to NOX formation occurs as biodiesel fuel proportion increases.

Exhaust toxicity evaluation in a gas turbine engine fueled by aviation fuel containing synthesized hydrocarbons

PurposeThe purpose of this paper is to examine the toxicological impacts of exhaust generated during the combustion process of aviation fuel containing synthesized hydrocarbons.Design/methodology/approachTests on aircraft turbine engines in full scale are complex and expensive. Therefore, a miniature turbojet engine was used in this paper as a source of exhaust gases. Toxicity was tested using innovative BAT–CELL Bio–Ambient Cell method, which consists of determination of real toxic impact of the exhaust gases on the human lung A549 and mouse L929 cells. The research was of a comparative nature. The engine was powered by a conventional jet fuel and a blend of conventional jet fuel with synthesized hydrocarbons.FindingsThe results show that the BAT–CELL method allows determination of the real exhaust toxicity during the combustion process in a turbine engine. The addition of a synthetic component to conventional jet fuel affected the reduction of toxicity of exhaust gases. It was confirmed for both tested cell lines.Originality/valueIn the literature related to the area of aviation, numerous publications in the field of testing the emission of exhaust gaseous components, particulates or volatile organic compounds can be found. However, there is a lack of research related to the evaluation of the real exhaust toxicity. In addition, it appears that the data given in aviation sector, mainly related to the emission levels of gaseous exhaust components (CO, Nox and HC) and particulate matters, might be insufficient. To fully describe the engine exhaust emissions, they should be supplemented with additional tests, i.e. in terms of toxicity.

The use of ionization sensors to study the combustion process in spark ignition engines

The article discusses the use of ionization sensors to study the combustion process in spark ignition engines. The results of an experimental study of the combustion process when operating both on gasoline and gas fuel are presented. Correlating dependences are obtained, which show the possibility of diagnosing the combustion process by the ion current of chemionization. The relationship between the amplitude of the ion current and the composition of the mixture, the speed of flame propagation, and the maximum pressure in the cylinder of the engine is revealed.

The determination of the rate of heat release in the diesel cylinder taking into account the change in the composition of the working substance

The thermodynamic efficiency of the cycle of the internal combustion engine and its efficiency are related to the law of supply of heat to the working fluid. The characteristics of heat release allow us to evaluate and improve the combustion process from the point of view of the thermodynamic efficiency of the cycle, from thermodynamic positions. To optimize the combustion process in compression-ignition engines, including when working on unconventional fuels, it is necessary to develop an algorithm for determining the rate of heat release, taking into account the current composition of the working fluid, since when working on fuels with a changed chemical composition, the ratio of gases in the combustion products can significantly change. The type of heat dissipation characteristic is determined by the regularities of the combustion of fuel in the cylinder e and the law of displacement of the piston and depends, inter alia, on the composition of the working fluid, which continuously changes during combustion of diesel fuel, increasing volume and mass. Existing methods for calculating the heat dissipation characteristics consider a working body consisting of two components - a fresh charge and combustion products. Such an approach reduces the accuracy of calculations when determining the heat input from the diesel fuel indicator chart operating on fuels with modified chemical composition or on non-traditional fuels, since it does not take into account the change in the heat capacity and internal energy of the combustion products. In this article, a mathematical model to compute the heat dissipation in the cylinder of a diesel engine when operating on diesel fuel for the changes in the working fluid composition. The presented results of calculations for a diesel engine of 2CH10.5/12.0 when operating on diesel fuel at the nominal operating mode correspond to the results of the determination of the integral and differential heat dissipation rate obtained by the well known CNIDI method.