Ceramic Material for Thermal Barrier Coatings in Compression Ignition Engine for its Performance Evaluation with Biodiesel

The compression ignition and small displacement spark-ignition engines play an important role in the urban air pollution. In particular, vehicles equipped with compression ignition engines are widely used because of their higher performance and fuel efficiency with respect to the spark-ignition ones. Nevertheless, spark-ignition engines with low displacements are even more wide-spreading because of the lower fuel consumption and emissions. They are also used for two-wheeled vehicles, whose easier navigation makes them widely used in heavily congested areas. Their contribution on urban pollution is worsened by the fact that these vehicles have to comply with the Euro 3 standard; light vehicles have, instead, to fulfill the more restrictive Euro 6, which for the compression ignition and gasoline direct injection engines indicates for particle emissions also a number-based regulation. This article aims to characterize the effects of biofuels on engine emissions and performance of compression ignition and spark-ignition engines. The investigation was carried out on different class of engines. Direct injection and a port fuel injection spark-ignition engines fueled with ethanol and its blends, 10 v/v%, 50 v/v% and 85 v/v% of ethanol in gasoline. The compression ignition engine was equipped with a common rail injection system and was fueled with pure rapeseed methyl ester, representative of fatty acid methyl ester, and its blends in diesel, 20 v/v% and 50 v/v%. The gaseous emissions and the particle concentration were measured at the exhaust by means of conventional instruments. Particle size distribution function was measured in the range from 5.6 to 560 nm by means of an engine exhaust particle sizer. A comprehensive characterization of the particulate carbon was performed by means of optical diagnostics in the combustion chamber. In particular, two-dimensional images of flame evolution were detected and processed by two-color pyrometry technique to assess the in-cylinder soot formation and oxidation processes. For both the investigated spark-ignition and compression ignition engines, the use of biofuels shows a partial increase in the specific fuel consumption and a reduction of the soot particles emission. Nevertheless, a further effort on engine technology should be paid to balance the mass with the size and number of the particles.

ABSTRACTAchieving the new emission norms is a difficult task to today’s compression ignition (CI) engine without any exhaust gas after-treatment technologies. It is necessary to find the practical method which reduces the unsafe emission, with minor modifications of the CI engine. Dual fuel homogeneous charge compression ignition (HCCI) engine has been recognised as one of the solutions to minimise the emissions and achieve higher performance. In the present study the dual fuel HCCI engine mode of operation carried out by supply of ethanol fuel-air mixture to the engine cylinder through the carburetor and diesel fuel is directly injected at the end of compression for the initiation of ignition. Dual fuel HCCI engine is one of the most promising engines suitable for alternative fuels and lower NOX emissions. An experimental investigation is carried out on dual fuel HCCI engine. Fuel consumption and exhaust emissions such as NOX, CO2, CO, HC are measured and compared with conventional CI engine. The results show that NOX emission tends to decrease at low and moderate loads of the engine, but at full load condition it is slightly higher. Further, thermal efficiency is calculated and compared in CI engine; it is observed that there is a slight improvement in thermal efficiency at high load operation. In the dual fuel HCCI engine mode, there is a provision to use of ethanol or any other alternate fuel for better energy efficiencies and low NOX emission.

<div class="section abstract"><div class="htmlview paragraph">In the last six decades, due to the continuous improvement in environmental legislations and depletion of fossil fuels in the world, IC engine researchers have been vigorously exploring various possibilities of reducing petroleum fuel dependency and emissions of internal combustion (IC) engines. Operating IC engines in low heat rejection (LHR) mode by providing thermal barrier coating (TBC) to some of the engine components is one of the methods to improve thermal efficiency and reduce some of the tailpipe emissions. Yttria stabilized zirconia (YSZ) is a commonly used TBC material in IC engines due to its thermal characteristics. On the other hand, running an engine in a dual-fuel operation by a gaseous fuel gives better and more efficient combustion. In this research work, an attempt was made to study the combined effects of running a compression ignition (CI) engine in dual-fuel operation with LHR mode on its performance, and emissions were investigated. For this purpose, a 4.4 kW, four-stroke, naturally aspirated, single-cylinder, direct injection (DI) diesel engine was converted to run in dual-fuel mode. Two pistons were used in this study; one is uncoated and the other one was coated. The second piston was coated by 300μm thickness with a ceramic composition of ZrO<sub>2</sub> and 6-8 wt% Y<sub>2</sub>O<sub>3</sub> ceramic material called as YSZ. A blend of Jatropha methyl ester (JME) with diesel in the respective proportion of 20% and 80% was prepared (JME20) and was used as pilot fuel, and the oxy-hydrogen (HHO) gas was used as inducted fuel for dual-fuel operation. The HHO gas is a carbon-free, hydrogen-based renewable fuel that is produced by the process of water electrolysis in a fabricated wet cell electrolyzer. The results indicated that the YSZ coated piston engine in both the dual-fuel operations (i.e) D100+HHO, and Opt.JME20+HHO showed thermal efficiency higher by about 5.5% and 5.9% compared to that of D100 operation at full load. The same dual-fuel operations also showed a reduction of HC, CO, and smoke irrespective of the engine load. The maximum HC, CO, and smoke emissions were reduced by about 38.2%, 40%, and 20.4% respectively for Opt.JME20+HHO with the YSZ coated piston engine compared to baseline data at full load.</div></div>

The importance of biodiesel as a renewable and economically viable alternative to fossil diesel for applications in compression ignition (CI) engines has led to intense research in the field over the last two decades. This is predominantly due to the depletion of petroleum resources, and increasing awareness of environmental and health impacts from the combustion of fossil diesel. Biodiesel is favoured over other biofuels because of its compatibility with present day CI engines, with no further adjustments required to the core engine configurations when used in either neat or blended forms. Studies conducted to date on various CI engines fuelled with varying biodiesel types and blends under numerous test cycles have shown that key tailpipe pollutants, such as carbon monoxide, aromatics, sulphur oxides, unburnt hydrocarbons and particulate matters are potentially reduced. The effects of biodiesel on nitrogen oxides emission require further tests and validations. The improvement in most of the diesel emission species comes with a trade-off in a reduction of brake power and an increase in fuel consumption. Biodiesel’s lubricating properties are generally better than those of its fossil diesel counterpart, which result in an increased engine life. These substantial differences in engine-out responses between biodiesel and fossil diesel combustion are mainly attributed to the physical properties and chemical composition of the fuels. Despite the purported benefits, widespread adoption of biodiesel usage in CI engines is hindered by outstanding technical challenges, such as low temperature inoperability, storage instabilities, in-cylinder carbon deposition and fuel line corrosion. It is imperative that these issues are addressed appropriately to ensure that long-term biodiesel usage in CI engines does not negatively affect the overall engine durability. Possible solutions range from biodiesel fuel reformulation through feedstock choice and production technique, to the simple addition of fuel additives. This calls for a more strategic and comprehensive research effort internationally, with an overarching approach for co-ordinating sustainable exploitation and utilisation of biodiesel. This review examines the combustion quality, exhaust emissions and tribological impacts of biodiesel on CI engines, with specific focus on the influence of biodiesel’s physico-chemical properties. Ongoing efforts in mitigating problems related to engine operations due to biodiesel usage are addressed. Present day biodiesel production methods and emerging trends are also identified, with specific focus on the conventional transesterification process wherein factors affecting its yield are discussed.

High-temperature materials for thermal barrier coatings (TBC) have important prospects for application in the aircraft engine industry. To increase the service life and reliability of superalloy parts, the bond coat (BC) in the structure of the TBC is of great importance. In this study, the architecture of the BC material between the superalloy and the external ceramics is proposed. It is shown that the BC layer can consist of a sublayer of intermetallic NiAl (VKNA) and a mixture of VKNA with 15 or 30 wt.% zirconium dioxide (8YSZ). This architecture allows us to form by spark plasma sintering (SPS) technique. In the work, samples of a gradient BC VKNA/VKNA+(15% or 30%)YSZ/YSZ were obtained using SPS at 1070 oC, a pressure of 30 MPa and an isothermal exposure of 5 min. In all sintered compositions the porosity did not exceed 2%. The structure of the BC material is characterized by scanning electron microscopy, energy-dispersion spectroscopy, and micro-durometry. It is shown that the SPS provides an adhesive connection of the sublayers in the BC layer and with the external ceramics. The microhardness increases li nearly during the transition from the VKNA layer to the YSZ layer through a BC with different YSZ content in the sublayer. The BC samples demonstrated a thermal conductivity gradient from the Inconel 625 substrate to YSZ and the influence of the YSZ content in the sublayers on the decrease in the coefficient of linear thermal expansion in the temperature range of 800–1000 oC was also determined. Damage to the ceramic surface during thermal cycling in air at 1100 oC, i.e. the appearance and development of cracks, is not more than 10% at 45 cycles.This research was carried out under Basic Scientific Research Assignment No. FSNM-2020-0026 of the Ministry of Education and Science of Russia and was funded by the Russian Foundation for Basic Research, Grant No. 19-48-590007.

Air plasma sprayed thermal barrier coatings (APS-TBCs) deposited on the TiAl intermetallic compounds was heat exposed in air at different temperatures and times to evaluate the microstructural change and delamination behavior. The thermal barrier coating (TBC) layer, bond coat (BC) layer and substrate were composed of 4 mol% Y2O3 stabilized ZrO2, CoNiCrAlY alloy (Co-32Ni-21Cr-8Al-0.5Y (mol%)) and TiAl intermetallic compound (Ti-46Al-7Nb-0.7Cr-0.2Ni-0.1 Si (mol%)), respectively. Due to the heat exposure, diffusion of the elements occurred between the BC layer and the substrate, and diffusion layers were formed on both the BC layer and the substrate. A thermally grown oxide (TGO) layer was formed between the TBC layer and the BC layer. The thickness of the TGO layer and the diffusion layer increased with increasing exposure temperature and time. In the TBCs heat exposed at 1273 K for 200 h, a composite oxide of Al2O3 and TiO2 was formed in the BC layer. Regarding the TBCs which were as-deposited and heat exposed at 1073, 1173 K up to 200 h and at 1273 K for 10 h, delamination occurred in the TBC layer near the BC layer. In the TBCs exposed at 1273 K for 50 h or more, delamination occurred at the vicinity of the interface between diffusion layer on the substrate side and the unreacted side of the substrate too. In case that the TBCs were heat exposed at 1073 and 1173 K, the shear strength decreases after reaching the maximum value of the shear strength at 10 h heat exposure. When the TBCs were exposed to heat at 1273 K, the shear strength indicated a constant value after the shear strength increased up to 50 h. This change may be due to the change in crack path after exposure for 50 h at 1273 K.

Spark assisted premixed charge compression ignition engine prototype development

The thermochemical conversion of biomass into producer gas presents an attractive alternative fuel option for compression ignition (CI) engines, making biomass gasification a critical driver for achieving sustainable development goals. Considering the application of producer gas (PG) in CI engine, the most potential gases include H2 and CO as main fuel compounds and it is crucial to comprehensively understand the impact of these two gas components on the engine behaviour. Nowadays, artificial intelligence-powered models are frequently applied for simulating engines that run on a single type of fuel. However, their usage is not as common when it comes to modeling dual-fuel CI engines run on synthetic producer gas or syngas. The present study explores the feasibility of optimizing operational parameters, such as engine load and syngas composition, in improving the efficiency and lowering the levels of pollutants emitted by a 3.5 kW CI engine operated under dual fuel (DF) mode using syngas as primary fuel and diesel as pilot fuel. The performance and emission characteristics of syngas (H2:CO) is examined by studying its behaviour in four different combinations. The compositions of syngas are prepared based on the volumetric percentage of the H2 and CO and is inducted into the combustion chamber using a novel venturi-type air-gas mixer. In the present study, an intelligent metaheuristics-based optimization algorithm i.e., Teaching–Learning Based Optimization (TLBO) is developed and introduced, to develop a predictive model within constrained range of engine operating conditions. Further, the algorithm is used to estimate multiple engine performance characteristics simultaneously viz., brake thermal efficiency (BTE), unburned hydrocarbons (HC), and carbon monoxide (CO). The resultant findings identify the optimal engine load of 68.87% and the ideal syngas composition of 63.9% H2 and 49.5% CO as key parameters for maximizing engine efficiency while minimizing exhaust emission. At these optimized operating condition, 19.49% BTE is observed, while HC and CO emission was found to be 384.6 ppm and 445.33 ppm respectively. This shows the effective and efficiency of the proposed algorithm.

The fundamental difference between spark ignition (SI) and compression ignition (CI) engines lies in the type of combustion that occurs, and not in whether the process is idealised as an Otto cycle or a Diesel cycle. The combustion process occurs at neither constant volume (Otto cycle), nor constant pressure (Diesel cycle). The difference between the two combustion processes is that spark ignition engines usually have pre-mixed flames while compression ignition engines have diffusion flames. With pre-mixed combustion the fuel/air mixture must always be close to stoichiometric (chemically correct) for reliable ignition and combustion. To control the power output a spark ignition engine is throttled, thus reducing the mass of fuel and air in the combustion chamber; this reduces the cycle efficiency. In contrast, for compression ignition engines with fuel injection the mixture is close to stoichiometric only at the flame front. The output of compression ignition engines can thus be varied by controlling the amount of fuel injected; this accounts for their superior part load fuel economy.

Mechanical properties and thermal cycling behavior of Ta2O5 doped La2Ce2O7 thermal barrier coatings prepared by atmospheric plasma spraying

The growth behavior of thermally grown oxide (TGO) on the bond coats of thermal barrier coatings (TBCs) has a significant impact on the TBCs lifetime. The splashed particles on the thermally sprayed MCrAlY bond coat surface have weak bonding with the underlying bulk coating, which will lead to the formation of mixed oxides and promote the failure of TBCs. In this study, the interface between the splashed particles and underlying bond coating was healed by vacuum pre-treatment (pre-diffusion). The bond coats were divided into three groups by the ways of pre-treatments before deposition of the ceramic top coating. Two groups of bond coats were subjected to two different pre-treatments (pre-diffusion-oxidation and pre-oxidation) prior to cyclic oxidation tests. The third bond coats were directly subjected to the same cyclic oxidation tests. Results show that the different TBCs present different cyclic oxidation behavior. The TBCs with pre-diffusion-oxidation exhibited the best cyclic oxidation resistance, and the ones without pre-treatment had the worst cyclic oxidation resistance. It is revealed that the healing of interface between the splashed particles and underlying bulk coating can effectively improve the cyclic oxidation resistance. This study will benefit the development of advanced TBCs with long lifetime and high reliability.

Alternative fuels can be produced from both non-edible feedstocks and edible crops. The higher production costs and contaminating nature of vegetable biofuels, which cause engine component failure, make it conceivable to encourage the synthesis of biodiesel from non-edible sources. One of the most widely utilized alternative fuels is Jatropha biofuel, which has performance levels comparable to diesel fuels and can be used with CI (Compression Ignition) engines without any modifications. However when it comes to oxidative stability properties that impact shelf life and commercialization, the majority of biodiesels—including Jatropha—are lacking. Therefore, the objective of this study was to enhance the oxidative stability and other physicochemical parameters, such performance and emission characteristics, of Jatropha biodiesel with diesel blends by adding additives like DEE (diethyl ether) and MA (moringa oleifera antioxidant). The seeds of jatropha and moringa were harvested by hand and then mechanically extracted with a screw press. A conical flask containing the precisely weighed amount of oil is filled with 50 mL of neutral alcohol. The combination is then heated for an hour using a water condenser over a bath. Using phenolphthalein indicator, the contents are titrated with KOH solution after cooling. Weight of oil taken (w)/volume of KOH used (mL) × normality of KOH is the formula used to determine the acidity value of jatropha oil. It is therefore below the minimum level set by ASTM D 675, which is 2.5 mg KOH/g. Methanol was used in the transesterification process to produce biodiesel, and potassium hydroxide (KOH) was used as a catalyst. Then, using 5 % DEE and 10 % MA additives, the physicochemical properties of jatropha biodiesel—such as density, kinematics viscosity, calorific value, and oxidative stability—were characterized. The percentage of improvement of the biodiesel's mentioned properties with these additives was 0.68 %, 2.8 %, 0.73 %, and 33.8 %, respectively. The brake thermal efficiency (BTE) of B40MA10DEE05D45 increased by 8.52 % whereas the brake specific fuel consumption (BSFC) of B50MA10DEE05D35, which is Made up of 44 % diesel, 50 % jatropha biodiesel, 5 % DEE, and 10 % MA fuels, declined by 5.14 %. As a result of these additions, the blended fuel's CO, HC, and NOx emissions were reduced by 3.51 %, 2.25 %, and 8.64 %, respectively. Therefore, a 20 % blend of Jatropha biodiesel and diesel containing antioxidants from Moringa can be used in compression ignition engines without the need for engine modifications and with high oxidation stability.

In the internal combustion engine types, the gasoline compression ignition engine (GCI engine) presents the potential and effective method to improve engine thermal efficiency and lower pollution emissions when compared to the spark-ignition engine (SI) and the compression ignition engine (CI engine), respectively. To improve those advantages of the GCI engine, new engine technologies are being developed to help the engine efficiently work with higher compression ratios or lower octane gasoline fuel at part load conditions. However, high smoke, soot, HC and CO formations, the part-load stability of the combustion phase, or autoignition at high load conditions are still challenging with the GCI engine. This chapter will introduce some technologies that help solve the GCI engine's challenges, these technologies are such as: injection strategy, exhaust residual gas strategy, biodiesel addition, and oxygen content. After the aforementioned technological implementations, a detailed investigation will be carried out to lay the scope on the GCI engine performance and its emission characteristics. Multiple injections may help improve combustion stability and engine efficiency when compared to a single injection strategy. The HC and CO emissions can be decreased when the engine applies a multiple injection strategy and GB05 as fuel. The increase in EGR helps to reduce autoignition for both single and numerous ignition strategies. The oxygen concentration has a sensitive effect on the delay of the ignition process. The reduced amount of oxygen concentration induces an increase in the ignition delay, which helps to reduce the auto-ignition.KeywordsGCI engineInjection strategyEGRGB blendsOxygen concentrate

To reduce the amount of carbon dioxide released from transportation the EU has implemented legislation to mandate the renewable content of petrol and diesel fuels. However, due to the complexity of the combustion process the addition of renewable content, such as biodiesel and ethanol, can have a detrimental effect on other engine emissions. In particular the engine load can have a significant impact on the emissions. Most research that have studied this issue are based on steady state tests that are unrealistic of real world driving and will not capture the difference between full and part loads. This study aims to address this by investigating the effect of renewable fuel blends of diesel, biodiesel and ethanol on the emissions of a compression ignition engine tested over the World Harmonised Light Vehicle Test Procedure (WLTP). Diesel, biodiesel and ethanol were blended to form binary and ternary blends, the ratios were determined by Design of Experiments (DoE). The total amount of emissions for CO, CO2 and NOx as well as the fuel consumption, were measured from a 2.4 L compression ignition (CI) engine running over the WLTP drive cycle. The results depicted that percentages smaller than 10% of ethanol in the fuel blend can reduce CO emissions, CO2 emissions as well as NOx emissions, but increases fuel consumption with increasing percentage of ethanol in the fuel blend. Blends with biodiesel resulted in minor increases in CO emissions due to the engine being operated in the low and medium load regions over the WLTP. CO2 emissions as well as NOx emissions increased as a result of the high oxygen content in biodiesel which promoted better combustion. Fuel consumption increased for blends with biodiesel as a result from biodiesel’s lower heating value. All the statistical models describing the engine responses were significant and this demonstrated that a mixture DoE is suitable to quantify the effect of fuel blends on an engine’s emissions response. An optimised ternary blend of B2E9 was found to be suitable as a ’drop in’ fuel that will reduce harmful emissions of CO emissions by approximately 34%, NOx emissions by 10% and CO2 emissions by 21% for transient engine operating scenarios such as the WLTP drive cycle.

Performance and emission characteristics of a Kirloskar HA394 diesel engine operated on fish oil methyl esters