Advances in biodiesel fuel for application in compression ignition engines

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.

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.

Improving performance and emissions characteristics of compression ignition engine: Effect of ferrocene nanoparticles to diesel-biodiesel blend

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.

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.

This study investigates the potential of green-synthesized nanoparticles (NPs) doped with a 20% biodiesel blend to enhance the performance and emissions characteristics of a compression ignition (CI) engine. The green synthesis of NPs offers an environmentally friendly alternative to conventional methods, while the addition of biodiesel provides a renewable fuel source. Experimental trials were conducted using various concentrations of NP-doped biodiesel blends in a CI engine. Performance parameters such as brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), and exhaust gas temperature (EGT) were measured. Additionally, emissions profiles, including smoke intensity, carbon monoxide (CO), oxides of nitrogen (NOx), and unburned hydrocarbons (HC), were analyzed. The results demonstrated that the incorporation of NP-doped biodiesel blends led to significant improvements in engine performance. A reduction in BSFC and an increase in BTE were observed, indicating enhanced fuel efficiency. Furthermore, the NP-doped blends contributed to a substantial decrease in smoke, NOx and other harmful emissions, suggesting a positive environmental impact. This research highlights the promising potential of green-synthesized NPs and biodiesel blends as a sustainable and efficient fuel alternative for CI engines.

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

This paper analyses the effect of exhaust gas recirculation (EGR) on the engine performance and emissions of a compression ignition (CI) engine operating on diesel-biodiesel (rubber seed oil methyl ester) blends. Biodiesel operated engines generally produce less unburned hydrocarbon, carbon monoxide and smoke compared to diesel fuel but more NOx emissions. NOx formation is a temperature dependent phenomenon and takes place when the combustion temperature is more than 2000K. EGR is an effective method for reducing NOx emissions in CI engines because it reduces the flame temperature and the oxygen concentration in the combustion chamber. In this study both hot EGR and cold EGR (5%, 10% and 15%) are used. It was found that NOx emission decreases substantially with both hot and cold EGR but smoke and carbon monoxide emissions are increasing with higher EGR rates. Brake thermal efficiency (BTE) increases with hot egr but cold EGR gives lower thermal efficiency than hot egr. Hot EGR emits less smoke and less NOx at higher loads compared to cold EGR. It was observed that exhaust gas between 10% and 15% can be recirculated for getting better results. The use of EGR is thus considered to be one of the most effective in reducing NOx emissions.

Spark assisted premixed charge compression ignition engine prototype development

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.

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.

<div class="section abstract"><div class="htmlview paragraph">Many promising technologies are under research for providing alternate solutions to conventional spark and compression ignition engines in order to meet stringent emission norms. One among them is Reactivity Controlled Compression Ignition (RCCI) engines. It uses a port injected fuel similar to SI engines and the charge (air + fuel) is ignited similar to CI engines. Generally, two fuels of different reactivities are chosen for this technique. RCCI can be achieved either by injecting one fuel through port and one fuel through in cylinder or both the fuels through the intake port. In this research work, a simple and cost effective electronic fuel injection technique was established to handle both the single and dual port injection systems. The developed electronic circuit was tested on a CI engine with RCCI mode using gasoline open valve port injection and diesel in cylinder injection for a constant proportion of diesel/ gasoline (60:40) at different loads. It was found that, the use of port injected gasoline showed a similar efficiency to conventional diesel at high loads, along with reduction in NOx emissions. However, other emissions were increased due to open valve injection. An engine with a cost effective electronic fuel injection system, working under RCCI mode of operation was tested for ensuring effective operation of the developed control system.</div></div>

Homogeneous charge compression ignition (HCCI) engine combines the combustion characteristics of a compression ignition engine and a spark ignition engine. HCCI engines take advantage of the high compression ratio and heat release rate and thus exhibit high efficiency found in compression ignition engines. In modern research, simulation has be come a powerful tool as it saves time and also economical when compared to experimental study. Engine simulation has been developed to predict the performance of a homogeneous charge compression ignition engine. The effects of compression ratio, cylinder pressure, rate of pressure rise, flame temperature, rate of heat release, and mass fraction burned were simulated. The simulation and analysis show several meaningful results. The objective of the present study is to develop a combustion characteristics model for a homogeneous charge compression ignition engine running with isooctane as a fuel and effect of compression ratio.

Prior to the emergence of petrol-based fuels, ethanol was regarded as a potentially viable option for powering internal combustion engines (ICEs). In 1826, Samuel Morey developed an engine powered by ethanol, yet it was not until 1908, with the introduction of the Ford Model T and Henry Ford’s conviction in ethanol as a feasible automotive fuel, that it garnered substantial attention. Despite this early recognition, the high cost of ethanol and the rapid expansion of petroleum production led to its decline, only to be revived much later due to growing concerns about global warming and the need to reduce greenhouse gas emissions. Subsequently, ethanol has resurfaced as a possible “green” fuel due to its renewable, plant-based origins. However, since 1908, significant changes have occurred, and modern engines are largely designed for gasoline and diesel, rather than ethanol. A significant challenge associated with the use of ethanol is its low cetane number (CN), which renders it incompatible with compression ignition engines. In addition to this, its high auto-ignition temperature, low CN, and high latent heat of vaporization present further challenges. This study explores a potential solution to these issues by testing a Combustion Enhancer based on Nitrates (CEN) to improve ethanol’s ignition and combustion performance in compression ignition engines. Widely used in transport and industrial sectors, such as Heavy Duty, Mine, Rail, Agriculture, Power Generation, the development of ethanol engines is seen as one of the ways for the road & off-road decarbonation. The impact of CEN on the combustion of ethanol was studied using several research methods, including a Rapid Compression Machine (RCM), a New One-Shot Engine, (NOSE) and a Direct Injection Compression Ignition (DICI) Engine. RCM experiments at compression pressures of 40 bar and varying temperatures (720–880 K) demonstrated an increase in ethanol’s fuel reactivity for different equivalence ratios (0.5, 1, and 1.5) with only a 5000 ppm addition of CEN. The study on the NOSE showed impacts, with up to 5% CEN, on the characteristics of the spray such as liquid and vapor penetration, spray angles and evaporation process. To further evaluate the potential of the CEN on ethanol, additional tests were conducted on a single-cylinder DICI engine using pure ethanol and ethanol-CEN blends. Key parameters such as combustion stability (CoVIMEP), apparent heat release rate (AHRR), and indicated thermal efficiency (ITE) were measured. The findings demonstrated that the addition of CEN enhanced combustion stability, particularly at low load conditions, and made it possible the use of ethanol as a single fuel in a DICI engine. This study exposes multiple findings related to the use of a Combustion Enhancer (CEN) for ethanol. Through a Rapid Compression Machine (RCM), the use of CEN made it possible to decrease the Ignition Delay Time (IDT) of ethanol under different air-fuel equivalence ratios. The study of the ethanol’s spray on a High Pressure – High Temperature vessel exposes that the use of CEN can change the evaporation process of the fuel, even with only 5% of additization. Finally, this study exposed that stable combustion can be achieved with CEN-blended ethanol at low intake temperatures (<50°C) and low loads (3 bar IMEP) in a DICI engine, while combustion stability is lost at higher temperatures (>100°C) for pure ethanol.

The objectives for this project are as follows: Develop detailed chemical kinetic models for fuel components used in surrogate fuels for compression ignition (CI), homogeneous charge compression ignition (HCCI) and reactivity-controlled compression-ignition (RCCI) engines; and Combine component models into surrogate fuel models to represent real transportation fuels. Use them to model low-temperature combustion strategies in HCCI, RCCI, and CI engines that lead to low emissions and high efficiency.