Study of performance and emission characteristics of IC engines by using diesel–water emulsion

Due to the shortage of petroleum products and its increasing cost, efforts are on to develop alternate fuels, especially diesel oil, for partial or full replacement. Also, internal combustion engines generate undesirable emissions during combustion process. The emissions exhausted in to the surroundings pollute the atmosphere and causes several problems. The emissions of concern are: unburnt hydrocarbons, oxides of carbon, and oxides of nitrogen (NO_X). Advanced diesel fuel formulations offer significant emission reductions to new and older in-use engines every time the fuel tank is filled. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation. The incorporation of water also reduces NO_X emissions by lowering the peak combustion temperatures through high heat of vaporization. When using water blend diesel, the engine fuel system recognizes the liquid as diesel fuel because the water droplet is encapsulated within a diesel fuel. In this experiment, we have used single cylinder four-stroke engine and the water-blend diesel emulsion is used and the diesel emission test, emulsion emission test, and various gases has been analyzed; smoke meter test is also conducted for various rate of loads. The test results from the engine fuelled with water-blend diesel showed reduction in emissions as compared to that of engine fuelled with conventional diesel. The better emissions in the CI engine using water-blend diesel is due to the incorporation of water which reduces NO_X emissions by lowering the peak combustion temperatures. Water-blend fuel enhances fuel atomization by micro-explosion. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation     

Feasibility and performance study of turpentine fueled DI diesel engine operated under HCCI combustion mode

In the present investigation a volatile fraction of Pinus resin called Turpentine has been experimented in a direct injection diesel engine under HCCI combustion mode. The engine chosen to experiment is a single cylinder DI diesel engine and modified in such a way to ignite Turpentine in a diesel engine under HCCI mode. As the Turpentine has a higher self ignition temperature the ignition of Turpentine in regular diesel engines with auto-ignition is not possible. Hence, suitable modification is made in the engine to ignite Turpentine in a diesel engine like diesel fuel. The modified engine has ECM controlled fuel spray and an air preheater in the suction side of the engine. The combined effort of adiabatic compression and supply of preheated air ignites turpentine by auto-ignition and its timing of ignition is precisely controlled by changing intake air temperature. This investigation revealed that the engine operated with turpentine performed well with little loss of brake thermal efficiency. And, emitted comparatively lower emissions such as NO_x and smoke and proved that the turpentine is a best suited fuel for HCCI operation.     

Reduced Quasi-Dimensional Combustion Model of the Direct Injection Diesel Engine for Performance and Emissions Predictions

A new concept of reduced quasi-dimensional combustion model for a direct injection diesel engine is developed based on the previously developed quasi-dimensional multi-zone model to improve the computational efficiency. In the reduced model, spray penetration and air entrainment are calculated for a number of zones within the spray while three zones with aggregated spray zone concept are used for the calculation of spray combustion and emission formation processes. It is also assumed that liquid phase fuel appears only near the nozzle exit during the breakup period and that spray vaporization is immediate in order to reduce the computational time. Validation of the reduced model with experimental data demonstrated that the new model can predict engine performance and NO and soot emissions reasonably well compared to the original model. With the new concept of reduced model, computational efficiency is significantly improved as much as 200 times compared to the original model.     

Numerical investigation on NOX formation in oxygen-CH4 MILD combustion with air leakage

In this paper, we focus on formation of NO_X under oxy-fuel MILD combustion using JHC (jet-in hot co-flow) burner. The effect of the different oxygen dilution ratio in the co-flow is analyzed for MILD combustion formation and also for characterizing NO_X emission. RANS (Reynolds averaged Navier Stokes) with the modified k-ε equation and EDC (eddy dissipation concept) model were applied for 2D-axisymmetric computational domain using the Ansys Fluent. It is found that the effect of the oxygen concentration rather than the composition of dilution gas is more significant for the formation of the MILD combustion and as the oxygen concentration of the dilution gas increases under MILD combustion conditions, the region with D_a < 1 expressed as MILD regime tends to be decreased. The effect of a diluted oxygen concentration in the oxy-fuel combustion on NO_x emission under MILD condition is found to be much greater than the amount of air leakage into co-flow, and NO emissions are almost unaffected by the increase of N₂ concentration in case of MILD combustion condition within practical air leak ranges.

     

Influence of injection rate shaping on combustion and emissions for a medium duty diesel engine

This paper describes the effects of injection rate shaping on the combustion, fuel consumption and emission of NO_X and soot of a medium duty diesel engine. The focus is on the influence of four different injection rate shapes; square type 1, square type 2, boot and ramp, with a variation of maximum injection pressure and start of injection (SOI). The experiments were carried out on a 1 liter single cylinder research diesel engine equipped with an amplifier-piston common rail injection system, allowing the adjustment of the injection pressure during the injection event and thus injection rate as desired. Two strategies to maintain the injected fuel mass constant were followed. One where rate shaping is applied at constant injection duration with different peak injection pressure and one strategy where rate shaping is applied at a constant peak injection pressure, but with variable injection duration. Injection rate shaping was found to have a large effect on the premixed and diffusion combustion, a significant influence on NO_x emissions and depending on the followed strategy, moderate or no influence on soot emission. Only small effects on indicated fuel consumption were found.     

An experimental study on combustion processes and nox emission characteristics of the air-staged burner

The combustion processes and emission characteristics in air-staged burner have been experimentally studied. The light fuel oil doped with pyridine(C₅H₅N) is used to investigate the fuel NO_X emission characteristics. Experiments are carried out for a wide range of operating conditions of single-staged and multi-staged burner. The detailed discussions are made for the flame structure of the air-staged burner as well as effects of excess air ratios, staged air flow percentage, and spray conditions on flame pattern and NO_X emission characteristics.     

PSR-based microstructural modeling for turbulent combustion processes and pollutant formation in double swirler combustors

The present study numerically investigates the fuel-air mixing characteristics, flame structure, and pollutant emission inside a double-swirler combustor. A PSR (Perfectly Stirred Reactor) based microstructural model is employed to account for the effects of finite rate chemistry on the flame structure and NO formation. The turbulent combustion model is extended to nonadiabatic flame condition with radiation by introducing an enthalpy variable, and the radiative heat loss is calculated by a local, geometry-independent model. The effects of turbulent fluctuation are taken into account by the joint assumed PDFs. Numerical model is based on the non-orthogonal body-fitted coordinate system and the pressure/velocity coupling is handled by PISO algorithm in context with the finite volume formulation. The present PSR-based turbulent combustion model has been applied to analyze the highly intense turbulent nonpremixed flame field in the double swirler combustor. The detailed discussions were made for the flow structure, combustion effects on flow structure, flame structure, and emmission characteristics in the highly intense turbulent swirling flame of the double swirler burner.     

A study on the characteristics of soot formation and oxidation in free fuel droplet array

In this study, it was attempted to obtain the fundamental data for the formation and oxidation of soot from a diesel engine. Combustion of spray injected into a cylinder is complex phenomenon having physical and chemical processes, and these processes affect each other. There are many factors in the mechanism of the formation and oxidization of soot and it is necessary to observe spray combustion microscopically. In order to observe with that view, free fuel droplet array was used as an experimental object and the droplet array was injected into an atmospheric combustion chamber with high temperature. Ambient temperature of the combustion chamber, interdroplet spacing, and droplet diameter were selected as parameters, which affect the formation and oxidation of soot. In this study, it was found that the parameters also affect ignition delay of droplet. The ambient temperature especially affected the ignition delay of droplet as well as the flame temperature after self-ignition. As the interdroplet spacing that means the local equivalence ratio in a combustion chamber was narrow, formation of soot was increased. As diameter of droplet was large, surface area of the droplet was also broad, and hence evaporation of the droplet was more active than that of a droplet with relative small diameter.     

直喷式柴油发动机缸内三维温度场的计算与试验

为计算直喷式柴油发动机缸内燃烧温度,提出利用理想混合比质量分数空间来计算缸内温度场.通过引入混合比质量分数基本概念,推导出各种组分与混合比质量分数的关系.通过引入小火焰的假设,分析典型非预混合小火焰结构,推导出绝热状况下缸内温度与混合比质量分数的关系.在理想混合比质量分数空间坐标系下建立新的温度输运方程,提供一种将湍流化学反应场和湍流运动场分离开的方法.经过一系列参数的输入,计算出缸内温度与扩散尺度速率关系,缸内温度与混合比质量分数关系以及缸内火焰温度分布,试验验证了计算结果.为计算直喷式柴油发动机缸内燃烧温度以及污染物成分提供新的计算方法.     

Investigation of combustion and emission characteristics of n-hexane and n-hexadecane additives in diesel fuel

One of the most important basic requirements of diesel-powered vehicles that they have lower pollutant emissions and fuel consumption. In diesel engines, combustion and engine performance are influenced by the physical and chemical properties of the used fuel. Engine design studies are not enough to increase engine performance and reduce exhaust emissions alone. By adding fuel additives in diesel fuel, the physical and chemical properties of the fuel can be improved. Fuel additives affect engine performance, combustion and emissions positively by exerting catalyst effect during combustion. In this study, n-hexane and n-hexadecane were added in diesel fuel (D0) by volume of 4, 12 % and 20 %. With respect to D0 fuel, in DHD20 and DHX20 fuels engine torque increased by 1.60 % and 1.32 %, respectively, while the brake specific fuel consumption decreased by 3.12 % and 1.98 %, respectively. Maximum cylinder pressures and heat release rate values of the ingredient added fuels increased. It was seen that NO_x emissions increased while HC, CO and soot emissions decreased with increasing contribution ratio.

     

Investigation of soot formation in a D.I. diesel engine by using laser induced scattering and laser induced incandescence

Soot has a great effect on the formation of PM (Paniculate Matter) in D.I. (Direct Injection) Diesel engines. Soot in diesel flame is formed by incomplete combustion when the fuel atomization and mixture formation were poor. Therefore, the understanding of soot formation in a D.I. diesel engine is mandatory to reduce PM in exhaust gas. To investigate soot formation in diesel combustion, various measurements have been performed with laser diagnostics. In this study, the relative soot diameter and the relative number density in a D.I. engine was measured by using LIS (Laser Induced Scattering) and LII (Laser Induced Incandescence) methods simultaneously which are planar imaging techniques. And a visualization D.I. diesel engine was used to introduce a laser beam into the combustion chamber and investigate the diffusion flame characteristics. To find the optimal condition that reduces soot formation in diesel combustion, various injection timing and the swirl flow in the cylinder using the SCV (Swirl Control Valve) were applied. From this experiment, the effects of injection timing and swirl on soot formation were established. Effective reduction of soot formation is possible through the control of these two factors.     

Numerical modeling for the H2/CO bluff-body stabilized flames

This study investigates the nonpreximed H₂/CO-air turbulent flames numerically. The turbulent combustion process is represented by a reaction progress variables model coupled with the presumed joint probability function. In the present study, the turbulent combustion model is applied to analyze the nonadiabatic flames by introducing additional variable in the transport equation of enthalpy and the radiative heat loss is calculated using a local, geometry independent model. Calculation are compared with experimental data in terms of temperature, and mass fraction of major species, radical, and NO. Numerical results indicate that the lower and higher fuel-jet velocity flames have the distinctly different flame structures and NO formation characteristics in the proximity of the outer core vortex zone. The present model correctly predicts the essential features of flame structure and the characteristics of NO formation in the bluff-body stabilized flames. The effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.     

Effect of spark plug protrusion on the performance and emission characteristics of an engine fueled by hydrogen-natural gas blends

Mixtures of hydrogen and natural gas are promising for improving efficiency and reducing harmful emissions in spark ignition engines, since limits of flammability can be extended while stable combustion is secured. In this research, the combustion characteristics of long electrode spark plugs were evaluated in a hydrogen blended with natural gas (HCNG) engine. Decreases in the flame propagation distance through the use of spark plugs can lead to increased burning rates and further improvement of fuel economy in HCNG engines. An 11-liter heavy duty lean burn engine was employed and performance characteristics including emissions were assessed according to the spark timing of the minimum advance for best torque (MBT) for each operating condition. Retarded MBT spark advance timing with long electrode spark plugs due to increased burning speed supported increases in engine efficiency and reductions of nitrogen oxide (NO_x) emissions. The lower positions of initial flame kernels due to the use of long electrode spark plugs were preferable to improvements of cyclic variability due to reduced flame front quenching, and carbon monoxide (CO) emissions at the flammability limit were also improved.     

Analysis on possibility of expanding low-load operation area for homogeneous charge compression ignition in CI engine with variable exhaust valve actuation

Various technologies are being studied for the advancement of diesel passenger cars and associated environmental regulations. Effective compression ignition combustion in diesel engines is highly dependent on the cylinder charging temperature, composition, and cylinder pressure during valve train operation. The application of variable valve control in diesel engines has several potential advantages. In this study, we applied the variable valve actuation system to a single-cylinder engine model using a GT-POWER simulation and analyzed the effects of the recompression and rebreathing valve profiles, and fuel-injection pressure on the combustion characteristics of a compression ignition engine. As a result, NOx emissions were reduced by more than 90 %, while those of indicated mean effective pressure were reduced by up to 35 %. The benefits of recompression strategies in terms of NOx emissions reduction were confirmed.

     

一种研究柴油甲醇双燃料的定容燃烧弹试验装置

设计并研制了一种定容燃烧弹试验装置,用于对柴油在甲醇/空气预混均质混合气中燃烧特性的基础研究。介绍了该试验装置的各子系统的原理、结构及特点。定容燃烧弹试验结果表明:甲醇抑制了柴油的着火燃烧,随着甲醇/空气混合气浓度的增大,燃烧火焰变暗,碳烟生成受到抑制。与空气热氛围相比,甲醇/空气混合气氛围延长了柴油的滞燃期,加长了火焰的浮起长度。火焰稳定后,甲醇氛围中火焰的浮起长度随时间的变化比在纯空气氛围中大。     

The influence of engine oil on diesel exhaust emissions

Increasingly stringent emission legislation, together with the requirements for improved diesel engine performance, such as fuel economy, friction reduction, and extended drain intervals, have led to attention being focused on engine oil quality. The use of low‐friction engine oils can improve engine fuel efficiency and lead to a significant reduction of gaseous emissions. Therefore, engine oil is of importance when considering engine design parameters. This paper describes a study of the contribution of engine oil to diesel exhaust emissions. The investigations have shown that diesel engine particulate emissions as well as hydrocarbons and NO_X emissions depend on the lubricant oil properties, in particular on the sulphur content, volatility, and metal content.     

基奇LabVIEW高压共轨柴油机燃烧过程的建模及仿真

通过对柴油机工作过程中燃烧阶段的分析,应用 LabVIEW 软件建立了高压共轨柴油机稳态建模仿真的燃烧模型。出于快速响应的目的,采用了零维单区燃烧模型。考虑到滞燃期,并且需与双韦伯模型搭配,通过调整模型参数,使其对某型号高压共轨柴油机进行仿真。比较试验和仿真数据表明,燃烧模型满足速度和精度要求,为柴油机稳态建模仿真系统的进一步开发奠定了基础。     

Effects of turbulent mixing on spray ignition in spray system

When a column of droplets freely falling from an ultrasonic atomizer was ignited behind a reflected shock, no ignition occurred at a temperature below 1100 K, even if the pressure was as high as IMPa. Although, a higher temperature condition ensured ignition, no luminous flame was observable by high-speed photography, and even if a luminous flame lump appeared at an extremely high temperature, it disappeared without spreading over the entire column of droplets in this case. It is known however that, if a fuel is injected into a diesel cylinder or an electric furnace, ignition occurs even at a temperature as low as 650 K with a luminous flame spreading over the entire spray. These differences could be caused by the effects of turbulent mixing between fuel droplets and hot air, in fact, turbulence-generating rods were placed on the upstream side of the spray column. Experimental results indicates that the ignition limit was lowered to 840 K, and the ignition delay period was decreased by increasing the intensity of turbulence. Furthermore, the light emission of the flame was intensified, and normal spray combustion was maintained in the low-temperature atmosphere after the shock tube ceased its operation.     

Performance and emission characteristics of a low heat rejection spark ignited engine fuelled with E20

In internal combustion engines, the concept of low heat rejection (LHR) using thermal barrier coating on the surface of combustion chamber is gaining attention. Thermal barrier coating reduces the heat transfer to the cooling system, protects engine components from peak heat flux and fluctuating temperature produced during combustion and improves the performance of the engine. Information in the literature is plentiful for LHR diesel engine and only few studies exist on LHR spark ignited engine. The application of thermal barrier coating in spark ignited engine is limited by pre-ignition and knocking due to elevated combustion chamber temperature. A spark ignited engine with moderate insulation on the combustion chamber and higher octane fuel can overcome this difficulty. The objective of the present experimental study is to quantify the changes in performance and emission characteristics brought by partial thermal insulation on the combustion chamber of a four stroke spark ignited engine fueled with E20 blend. Partial thermal insulation was created by coating 0.3 mm thick Alumina (Al₂O₃) on the cylinder head, inlet and exhaust valves. The changes are quantified with respect to unmodified engine fueled with gasoline. The combustion parameters such as flame development and rapid burn duration are also estimated and compared. The results indicate that partially insulated SI engine when fueled with E20 improves performance and reduces emission. A maximum of 48% reduction in THC and 50% reduction in CO emission at part load was achieved.

     

Numerical investigation of NOx reduction in a sudden-expansion combustor with inclined turbulent air jet

Axisymmetric sudden-expansion geometry of a co-flowing methane-air diffusion flame is considered to investigate the effect of air inlet conditions on NO_x formation, flow field and temperature distribution using the k-? turbulence and β-PDF combustion model. The predicted results are in acceptable agreement with the published experimental and numerical data. The obtained results show that increasing air turbulence intensity results in considerable decrease in NO formation. Increasing the inlet angle of the air causes the NO formation to decrease due to raising vorticity strength. As a new index, the mass-averaged integral of vorticity magnitude is introduced to investigate the effect of altering inlet angle of the air on the flow field.