Injection Strategy in Natural Gas–Diesel Dual-Fuel Premixed Charge Compression Ignition Combustion under Low Load Conditions

Dual-fuel premixed charge compression ignition (DF-PCCI) combustion has been proven to be a viable alternative to conventional diesel combustion in heavy-duty compression ignition engines due to its low nitrogen oxides (NO_x) and particulate matter (PM) emissions. When natural gas (NG) is applied to a DF-PCCI engine, its low reactivity reduces the maximum pressure rise rate under high loads. However, the NG–diesel DF-PCCI engine suffers from low combustion efficiency under low loads. In this study, an injection strategy of fuel supply (NG and diesel) in a DF-PCCI engine was investigated in order to reduce both the fuel consumption and hydrocarbon (HC) and carbon monoxide (CO) emissions under low load conditions. A variation in the NG substitution and diesel start of energizing (SOE) was found to effectively control the formation of the fuel–air mixture. A double injection strategy of diesel was implemented to adjust the local reactivity of the mixture. Retardation of the diesel pilot SOE and a low fraction of the diesel pilot injection quantity were favorable for reducing the combustion loss. The introduction of exhaust gas recirculation (EGR) improved the fuel economy and reduced the NO_x and PM emissions below Euro VI regulations by retarding the combustion phasing. The combination of an NG substitution of 40%, the double injection strategy of diesel, and a moderate EGR rate effectively improved the combustion efficiency and indicated efficiency, and reduced the HC and CO emissions under low load conditions.     

The operation of a turbulence chamber diesel engine with LPG fumigation for exhaust emissions control

An experimental study is conducted to evaluate the use of liquefied petroleum gas (LPG) as a secondary fuel for a Ricardo E-6, naturally aspirated, four-stroke diesel engine having a turbulence combustion chamber (indirect injection). The gaseous LPG is introduced together with the aspirated air (fumigation) at various proportions with respect to the diesel fuel which constitutes the main part. The influence of fuel feed ratios (LPG/diesel), in a vast range of loads, on fuel consumption, pressure diagrams, exhaust smokiness and exhaust gas emissions (nitrogen oxides, hydrocarbons and carbon monoxide) is investigated, the baseline being the single diesel fuel operation. The study for this type of engine, which has not being reported in the literature, shows a promise of the present method and reveals that above 60 per cent of maximum load the whole effect is beneficial concerning specific fuel consumption and smoke reduction. The examination of gaseous pollutant levels shows an involved relation with respect to load and fuel proportions. The best results (coupled to acceptable cylinder pressure levels) is obtained at a diesel fuel substitution value of 75% of maximum load, with an LPG mass fraction in the range 10 to 15%.     

Controlling automotive exhaust emissions: successes and underlying science

Photochemical reactions of vehicle exhaust pollutants were responsible for photochemical smog in many cities during the 1960s and 1970s. Engine improvements helped, but additional measures were needed to achieve legislated emissions levels. First oxidation catalysts lowered hydrocarbon and carbon monoxide, and later nitrogen oxides were reduced to nitrogen in a two-stage process. By the 1980s, exhaust gas could be kept stoichiometric and hydrocarbons, carbon monoxide and nitrogen oxides were simultaneously converted over a single 'three-way catalyst'. Today, advanced three-way catalyst systems emissions are exceptionally low. NOx control from lean-burn engines demands an additional approach because NO cannot be dissociated under lean conditions. Current lean-burn gasoline engine NOx control involves forming a nitrate phase and periodically enriching the exhaust to reduce it to nitrogen, and this is being modified for use on diesel engines. Selective catalytic reduction with ammonia is an alternative that can be very efficient, but it requires ammonia or a compound from which it can be obtained. Diesel engines produce particulate matter, and, because of health concerns, filtration processes are being introduced to control these emissions. On heavy duty diesel engines the exhaust gas temperature is high enough for NO in the exhaust to be oxidised over a catalyst to NO2 that smoothly oxidises particulate material (PM) in the filter. Passenger cars operate at lower temperatures, and it is necessary to periodically burn the PM in air at high temperatures.     

Study on the effect of exhaust gas-based fuel preheating device on ethanol–diesel blends operation in a compression ignition engine

Rapid depletion of fossil fuels and stringent emission regulations compel the scientific community to search for alternative energy sources for the internal combustion engines. Among many alternative biofuels, ethanol is getting worldwide attention for compression ignition engine either in the form of partial substitute or complete replacement for diesel fuel. Ethanol fuel has certain undesirable properties like poor flammability limit which results in cold starting issues and higher hydrocarbon emission which restricts their use in compression ignition engine. This issue can be easily overcome by preheating of ethanol fuel before it gets admitted inside the engine cylinder. In the present study, a standard preheating device is designed and fabricated in accordance with engine specifications and simulations were carried out under various operating conditions to evaluate its performance. Furthermore, experimental investigations were carried out in a compression ignition engine fueled with ethanol blends of 20 and 30% with diesel by volume and the fuel blends were preheated using burned exhaust gases. In addition, a comparative study has been carried out for preheated and non-preheated blends of E20 (20% of ethanol and 80% of diesel) and E30 with baseline diesel. The experimental results show that the preheated E20 (20% of ethanol and 80% of diesel) blend has higher brake thermal efficiency of 36.28% with a significant reduction in brake specific fuel consumption when compared with all the other blends. Moreover, the preheated E20 blend reduces the carbon monoxide, unburned hydrocarbon and smoke emissions by 49, 48 and 10%, respectively. However, the NOx emission is increased by 6% as compared to the non-preheating effect. It is also noted that the preheating of ethanol blends produced better combustion results with a significant reduction in the ignition delay period. Hence, it can be concluded that the ethanol fuel can be effectively used in a diesel engine by means of preheating using exhaust gases and could be a viable option for diesel engine applications.     

Influence of ethanol-diesel blended fuels on diesel exhaust emissions and mutagenic and genotoxic activities of particulate extracts

This study was aimed at evaluating the influence of ethanol addition on diesel exhaust emissions and the toxicity of particulate extracts. The experiments were conducted on a heavy-duty diesel engine and five fuels were used, namely: E0 (base diesel fuel), E5 (5%), E10 (10%), E15 (15%) and E20 (20%), respectively. The regulated emissions (THC, CO, NOx, PM) and polycyclic aromatic hydrocarbon (PAH) emissions were measured, and Ames test and Comet assay, respectively, were used to investigate the mutagenicity and genotoxicity of particulate extracts. From the point of exhaust emissions, the introduction of ethanol to diesel fuel could result in higher brake specific THC (BSTHC) and CO (BSCO) emissions and lower smoke emissions, while the effects on the brake specific NOx (BSNOx) and particulate matters (BSPM) were not obvious. The PAH emissions showed an increasing trend with a growth of ethanol content in the ethanol-diesel blends. As to the biotoxicity, E20 always had the highest brake specific revertants (BSR) in both TA98 and TA100 with or without metabolizing enzymes (S9), while the lowest BSR were found in E5 except that of TA98-S9. DNA damage data showed a lower genotoxic potency of E10 and E15 as a whole.     

Experimental investigation of doped mwcnts on biodiesel for enhancement of the performance and exhaust emissions in a diesel engine

This article deals with an experimental work that aims to examine the effects of MWCNTs dispersed into diesel fuels. Nano diesel fuels were prepared by dispersing multi-walled carbon nanotubes into base liquid. The MWCNT nanomaterial was mixed in the fuel blend along with a surfactant by means of an ultrasonicator, to attain stable dispersion. Physicochemical properties of nano-additive based diesel were measured and compared with pure diesel fuel. Physicochemical properties of nano-additive based diesel were measured and compared with pure diesel fuel. An experimental investigation was performed at a constant speed of 1500 revolution per minutes at different engine load conditions. The engine performance and exhaust emissions of a diesel engine burning MWCNTs were compared with pure diesel fuel. MWCNTs to diesel oil is effectively enhancing the performance and decreasing exhaust emissions in a diesel engine. The properties of N80?+?JB20 with MWCNT fuel blend are changed owing to the mixing of biodiesel and the combination of the MWCNT nanomaterials.     

An experimental investigation on the performance,combustion and emission characteristics of a variable compression ratio diesel engine using diesel and palm stearin methyl ester

An attempt has been made to use biodiesel prepared from non-edible portion of palm oil as fuel of a conventional mono-cylinder compression ignition engine. The present experimental investigation takes into account the combined effect of using blends of diesel–palm stearin biodiesel as fuels and the compression ratio on different performance, combustion and emission characteristics of the said engine. The experiments have been carried out on a single-cylinder, direct injection diesel engine at varying compression ratio of 16:1–18:1 in four steps. It is observed that the brake thermal efficiency reduces by 7.9% when neat biodiesel is used instead of diesel. But, it increases with the increase in compression ratio for all the blends. Brake specific fuel consumption and exhaust gas temperature increase with the addition of biodiesel to diesel and also with the increase in compression ratio. Heat release rate decreases with biodiesel, and it is minimum at the rated compression ratio of 17.5:1 for all the fuels considered here. On the other hand, ignition delay is found to be more with neat diesel, and it increases with the decrease in compression ratio. Significant reductions in emissions of carbon monoxide (CO), hydrocarbon (HC) and smoke are observed with biodiesel, while the emissions of oxides of nitrogen (NO_x) and carbon dioxide (CO₂) increase. The decrease in compression ratio increases the emissions of CO, HC and smoke, but the emissions of NO_x and CO₂ decrease with the decrease in compression ratio.     

Simultaneous reduction of NO–smoke–CO<Subscript>2</Subscript> emission in a biodiesel engine using low-carbon biofuel and exhaust after-treatment system

The present work focuses on the simultaneous reduction of NO–smoke–CO₂ emission in a Karanja oil methyl ester (KOME)-fueled single-cylinder compression ignition engine by using low-carbon biofuel with exhaust after-treatment system. Replacement of KOME for diesel reduced smoke emission by 3% but resulted in increase of NO emission and CO₂ emission by 13 and 35% at 100% load condition. In order to reduce CO₂ emission, tests were conducted with a blend of KOME and orange seed oil (OSO), a low-carbon fuel on equal volume basis (50–50). At the same operating conditions, compared to KOME, 27% reduction in CO₂ emission and 5% reduction in smoke emission were observed. However, a slight increase in NO emission was observed. To achieve simultaneous reduction of NO–smoke–CO₂ emissions, three catalysts, namely monoethanolamine, zeolite and activated carbon, were selected for exhaust after-treatment system and tested with optimum KOME–OSO blend. KOME–OSO + zeolite showed a great potential in simultaneous reduction of NO–smoke–CO₂ emissions. NO, smoke and CO₂ emissions were simultaneously reduced by about 15% for each emission compared to diesel at 100% load condition. The effect of exhaust after-treatment system with KOME–OSO blend on combustion, performance and other emission parameters is discussed in detail in this study. Fourier transform infrared spectrometry analysis and testing were done to identify the absorbance characteristics of zeolite material.     

A digital simulation of the exhaust nitric oxide and soot formation histories in the combustion chambers of a swirl chamber diesel engine

This work presents a computer simulation of the exhaust nitric oxide and soot emission histories from a four stroke, naturally aspirated, Diesel engine with a swirl prechamber (divided chamber). The simulation is based on a thermodynamic analysis, which was validated successfully concerning the performance of the engine (load, fuel consumption, maximum pressures, etc). The analysis includes the calculation of the heat exchange between gas and walls in both the main chamber and (swirl) prechamber, after computing the relevant characteristic velocities and lengths, while combustion in both the main chamber and the swirl prechamber is attacked by proposing a two-zone combustion model. The concentration of the constituents in the exhaust gases is calculated by incorporating a complete chemical equilibrium scheme for the C−H−O system of the eleven species considered, together with chemical rate equations for the calculation of nitric oxide (NO). A model for the evaluation of soot formation and oxidation rates is also included, in order to compute the net soot concentration. The contribution of each chamber to the formation of NO and soot is given by presenting time (crank angle) diagrams of the net NO and soot formation inside each chamber (histories of formation). To validate the analysis, an extensive experimental investigation is undertaken at the authors’ laboratory on a Diesel engine of this type by evaluating its exhaust emission characteristics in a wide range of operating conditions. The experimental results are found to be in good agreement with the theoretical results obtained from the computer program implementing the analysis, while the detailed NO and soot net formation histories provide insight into the mechanisms involved.     

直喷柴油机两种燃烧方式混合气形成的比较

利用KIVA-3V软件模拟了柴油机两种燃烧方式的混合气形成过程中的浓度场和温度场.模拟计算与实验结果表明,在常规柴油机燃烧方式中,燃油边喷边烧,混合气浓度和温度变化很大,导致预混合燃烧和扩散燃烧并存,NOx和碳烟比较高,CO和HC排放很低;利用早喷可以形成浓度场和温度场分层分布的均质混合气,实现均质充量压燃(HCCI)燃烧,碳烟和NOx很低,但CO和未燃烧的燃油排放很高.     

Determination of Lean Burn Combustion Temperature Using Ultraviolet Emission

Measurements of the ultraviolet emission spectrum emitted from a lean burn premixed natural gas flame were taken over a range of flame temperatures using a fiber-optic/CCD spectrometer. Combustion temperatures were determined by two methods: by measuring the unburned oxygen in the exhaust and by calculating the temperature using the fuel and airflows. These temperatures were correlated to ratios composed of the integrated intensity of the long wavelength region of the OH band between 310 to 340 nm (ratio's numerator) and that between 305 and 310 nm (ratio's denominator). Average local combustor flame temperatures at the end of the combustion zone may then be determined by tracking these ratios during combustor operation. The sensitivity of these ratios yields a 0.8% change in the ratios every 20 degF with a precision of plusmn30 degF or plusmn1% at 3000 degF with 95 % confidence bounds demonstrating the feasibility of this technique for use as a potential control parameter for gas turbine combustors burning natural gas and air mixtures. This method is well suited for the low equivalence ratios (< 1) required to reduce NOx and CO emissions. Other methods using peak ratios of different emission bands exhibit nonlinearity, lower sensitivity and greater uncertainty.     

Test run evaluation of a blend of fuel-grade ethanol and regular commercial gasoline: its effect on engine efficiency and exhaust gas composition

The purpose of this study is to evaluate the performance of a nationally manufactured vehicle on a test run with a blend of fuel-grade ethanol and commercial regular gasoline. The results showed that, when 10% ethanol was added to the gasoline, general engine performance was 5–10% higher, which was due to the increase in octane number of the mixture. Nevertheless, according to the lower heat value of the mixture, fuel consumption was approximately 5% higher than the regular gasoline. Carbon monoxide (CO) and hydrocarbon (HC) emissions were dramatically lower because, when ethanol (an oxygenate) was added to the fuel, it had an influence on combustion reaction improvement. On the other hand, nitrogen oxides (NOx) emissions increased due to the higher temperature in the combustion chamber.     

Advances in biodiesel fuel for application in compression ignition engines

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.     

DOC+DPF在防爆柴油机上的应用研究

在某型防爆柴油机加装DOC+DPF后处理装置上进行台架实验,结果表明,PY03型装置不会增大防爆柴油机系统的排气背压,对CO平均转化效率达96%,对颗粒物有较高的捕集和再生效率,不透光烟度平均转化效率为82.7%;PY02型装置因尺寸较小,热负荷较高,与该排放状况不匹配。为提高装置的利用率和使用寿命,通过对耦合的DOC+DPF孔道进行可燃性气体CO组分输运和颗粒物离散相数值模拟。结果表明:随着废气流速的增大,DOC+DPF出口废气中CO浓度升高,转化效率下降;15 m/s的气流速度是发动机该排放水平下转化效率最高的最大速度;孔道入口速度增大,颗粒物向孔道后端壁面沉积;DOC+DPF装置在防爆柴油机上实用可行。     

A numerical study on the performance,combustion and emission parameters of a compression ignition engine fuelled with diesel,palm stearin biodiesel and alcohol blends

A numerical simulation has been carried out in this study to evaluate the effect of alcohol addition to the blends of diesel and palm stearin biodiesel on the performance, combustion and emission of a diesel engine. The commercial software Diesel-RK has been used in this study to simulate a single-cylinder, naturally aspirated, direct injection, four-stroke diesel engine. The simulated results have been validated against experimental observation for the base fuel diesel. The effects of two alcohols, namely ethanol and methanol have been separately investigated and compared. The results indicate that although the brake-specific fuel consumption is slightly increased, the other performance characteristics and the entire combustion and emission parameters are improved with alcohol addition to diesel–biodiesel blends. The instantaneous heat release rate, ignition delay and oxides of nitrogen emission are found to be more with methanol than with ethanol. The diesel–biodiesel blend also shows better combustion and emission characteristics than that of diesel except oxides of nitrogen emission.     

Effect of advanced injection timing on the performance of natural gas in diesel engines

Concern over the environment and/or the increasing demand for conventional fossil fuel has promoted interest in the development of alternative sources of fuel energy for internal combustion (IC) engines. The effect of advanced injection timing on the performance of natural gas used as primary fuel in dual-fuel combustion has been examined. Satisfactory diesel engine combustion demands self-ignition of the fuel as it is injected near the top dead centre (TDC) into the hot swirling compressed cylinder gas. Longer delays between injection and ignition lead to unacceptable rates of pressure rise (diesel knock) because too much fuel is ready to burn when combustion eventually occurs. Natural gas has been noted to exhibit longer ignition delays and slower burning rates especially at low load levels hence resulting in late combustion in the expansion stroke. Advanced injection timing is expected to compensate for these effects. The engine has standard injection timing of 30° before TDC (BTDC). The injection was first advanced by 5.5° given injection timing of 35.5° BTDC. The engine ran for about 5 minutes at this timing and stopped. The engine failed to start upon subsequent attempts. The injection was then advanced by 3.5° (i.e. 33.5° BTDC). The engine ran smoothly on this timing but seemed to incur penalty on fuel consumption especially at high load levels.     

The performance analysis and design optimization of fuel temperature control for the injection combustion engine

The purpose of the paper is to analyze the performance and design optimization of fuel temperature control in the injection combustion engine. There is a fuel temperature control device designed between the injection and fuel pump to cool down or warm up the fuel. Thermoelectric module (TEC) chips are applied in the device to absorb or dissipate heat from the fuel. There are several results relating exhaust emission and engine output performance to fuel temperature in this paper to display the optimization of fuel temperature for the injection engine. The experimental results indicate that increasing fuel temperature will result in an increase in CO, HC, and in a decrease in NO_x. Increasing the fuel temperature may affect the fuel consumption and engine output for a gasoline engine at different A/F (air to fuel) ratios. With enhanced understanding and analyses, the effects of fuel temperature on engine performance, fuel consumption and emissions can be taken into account in engine design and evaluation.     

Automotive exhaust gas sensing systems

Gas sensors have become an integral component of control systems for internal combustion engines to provide information for feedback control of air-to-fuel ratio (A/F) to achieve improved vehicle performance and fuel economy as well as decreased levels of emission. Increasingly stringent limits on evaporative emissions as well as the requirement of having on-board diagnostics (OBD), which includes catalyst monitoring, necessitate the monitoring of exhaust gas constituents [i.e., carbon monoxide (CO), hydrocarbons (HCs), and oxides of nitrogen (NO_x)]. The different sensing requirements, testing procedures, environmental parameters, and need for microsystem-based realizations are discussed     

Influence of alumina nanoparticles additives into biofuel (water hyacinth)-diesel mixture on diesel engine performance and emissions

The using diesel and biodiesel blends as a fuel has been a recent field of study especially with nanoparticles additives. The addition of alumina nanoparticles to biodiesel was verified to reduce emissions, while engine performance was not given great attention to evaluate the effect of blending alumina nanoparticles with the diesel and biodiesel mixture on the performance characteristics of the diesel engine. Then performance and emission tests were carried out by using different fuel samples in a single cylinder diesel engine. The brake thermal efficiency for the alumina nanoparticles (50 ppm, 100 ppm) and biodiesel blends were lower than that of biofuel (D80B20) blends, it was decreased by 2.5 %, 6.05 % respectively as compared to the blend (D80B20). The rate of carbon monoxide emissions for the two biodiesel and alumina blends were lower than that of the biodiesel blend (D80B20) and the best reduction was for the blend (D80B20N50) and was 76.3 % as compared with the biodiesel blend (D80B20). Also, the nitrogen oxides emissions for all the blends with nanoparticles were lower than that of the blend D80B20 due to shortened ignition delay and less fuel was added during the combustion which lead to reduction in nitrogen oxides emissions.     

Effect of compression ratio on performance,emission and combustion characteristics of diesel–acetylene-fuelled single-cylinder stationary CI engine

The present investigation aims to depict the effect of compression ratio on performance, emission and combustion characteristics of diesel–acetylene-fuelled stationary compression ignition engine. The optimum values for compression ratio, injection timing and injection pressure for diesel were experimentally found, and baseline data were established as 20, 23° before top dead centre and 210 bar, respectively. In order to investigate the effect of acetylene fuelling, acetylene gas was inducted at four different flow rates of 60, 120, 180 and 240 litres per hour at compression ratio 20. It was observed that the flow rate of 120 litres per hour gave the best performance with highest brake thermal efficiency of 25.09%. In order to find the optimum compression ratio for acetylene fuelling at 120 litres per hour, experimentation was done at different compression ratios of 18, 19, 20, 21 and 22. Experimental results showed that highest brake thermal efficiency of 25.72% was achieved at compression ratio 21 for diesel–acetylene fuelling which was much higher than 23.32% for pure diesel. Carbon monoxide, hydrocarbon and smoke emissions were also measured and found to be lower, while the NOx emissions were higher at optimized values in dual-fuel mode as compared to those for pure diesel. Peak cylinder pressure and net heat release rate were also calculated and found to be higher in dual-fuel mode compared to diesel mode.