Incineration of diesel particulate matter using induction heating technique

Incineration of diesel particulate matter for the regeneration of a mesh-type particulate-filter is achieved using induction heating technique. Heating of the diesel particulates deposited on the mesh-type particulate-filter at around 600 °C is investigated. In the case of the particulate filter, stainless-steel mesh-type filters are considered and the influence on filtering efficiency, the engine performance due to back-pressure generation is studied. Theoretical estimation shows that induction heating approach for the regeneration via exhaust gas heating requires high power (>3 kW). On the other hand, regeneration of mesh-type particulate-filter using induction heating technique requires a low input power of around 0.5 kW in the off-line condition. The proposed mesh-type particulate-filter allowed a filtration efficiency of around 30–40% at lower engine speeds and part loads. Particulate combustion through induction heating at static condition is studied and power required for mesh-type filter and sintered metal filter regeneration during engine operation is estimated theoretically.     

Development of a highly efficient low-emission diesel engine-powered co-generation system and its optimization using Taguchi method

A highly efficient low-emission co-generation system using a 2000-cc common-rail direct-injection (CRDI) diesel engine with an after-treatment device (re-combustor) is developed. The co-generation concept is utilized to produce electric power by a generator as well as to recover waste heat from the exhaust gases. A re-combustor is installed at the exhaust gas outlet to perform secondary burning of the exhaust gases, resulting in an improvement of the system's thermal efficiency as well as a reduction of exhaust gas emissions. The main components of the re-combustor are coiled Pyromax wires installed in a ceramic housing, diesel oxidation catalyst (DOC), and diesel particulate filter (DPF). The tests are conducted at four water flow rates (10, 15, 20, and 25 LPM) and four electric power outputs (5, 15, 25, and 35 kW). In general, a great deal of time and expense are required to determine the optimum experimental conditions for the maximum efficiency of a co-generation system. However, in the present study, the optimum experimental conditions for the present system are found using the Taguchi method and analysis of variance (ANOVA), resulting in significant savings of time and expense. The results show that the present co-generation system achieves a maximum total efficiency of 85.7%, and a significant reduction of CO, NO_x, and PM by 73.3%, 34.3%, and 94%, respectively.     

Investigation of a hydrogen-assisted combustion system for a light-duty diesel vehicle

Two sets of experiments were conducted to investigate the effects of adding gaseous hydrogen to the intake of compression–ignition (CI) engines fueled with 20% bio-derived/80% petroleum-derived diesel fuel (B20). A 1.3 L, 53 kW CI engine coupled to an eddy-current engine dynamometer was tested first. Data were collected on engine operating parameters, fuel consumption, concentration of total oxides of nitrogen (NO_x) in the exhaust, and exhaust temperature. Eight steady-state operating points were tested with hydrogen flow rates equivalent to 0%, 5%, and 10% of the total fuel energy. In a second set of experiments, the stock gasoline engine of a 2005 Chevrolet Equinox was replaced with a 1.3 L, 66 kW CI engine, and urban drive cycles were run on a chassis dynamometer. The drive cycles were repeated with 0%, 5% and 10% of the fuel energy coming from the fumigated hydrogen. In both experiments, the addition of hydrogen did not result in discernable differences in engine efficiency. In the vehicle testing, there were no noticeable differences in drivability. There were modest reductions in NO_x emissions and increases in exhaust temperature with hydrogen addition. This investigation demonstrates that fumigating relatively small amounts of hydrogen into the intake of a modern diesel engine results in only modest changes in combustion efficiency and emissions with no detrimental effects on vehicle performance or drivability. This strategy can be used to partially offset the use of petroleum-based fuels in light-duty transportation vehicles.     

Effect of heat exchanger material and fouling on thermoelectric exhaust heat recovery

Thermoelectric devices are being investigated as a means of improving fuel economy for diesel and gasoline vehicles through the conversion of wasted fuel energy, in the form of heat, to useable electricity. By capturing a small portion of the energy that is available with thermoelectric devices can reduce engine loads thus decreasing pollutant emissions, fuel consumption, and CO₂ to further reduce green house gas emissions. This study is conducted in an effort to better understand and improve the performance of thermoelectric heat recovery systems for automotive use. For this purpose an experimental investigation of thermoelectrics in contact with clean and fouled heat exchangers of different materials is performed. The thermoelectric devices are tested on a bench-scale thermoelectric heat recovery apparatus that simulates automotive exhaust. It is observed that for higher exhaust gas flowrates, thermoelectric power output increases from 2 to 3.8 W while overall system efficiency decreases from 0.95% to 0.6%. Degradation of the effectiveness of the EGR-type heat exchangers over a period of driving is also simulated by exposing the heat exchangers to diesel engine exhaust under thermophoretic conditions to form a deposit layer. For the fouled EGR-type heat exchangers, power output and system efficiency is observed to be 5-10% lower for all conditions tested.     

乙醇掺混燃烧对柴油机油耗影响的实验研究

乙醇吸热后部分热解可产生多种气体的混合物,为了研究气体混合物掺混燃烧在柴油机上的节油效果,对柴油机系统进行了改造:乙醇通过安装在柴油机排气管上的小型高效换热器吸收烟气余热,部分热解后混合气体由进气道通入柴油机燃烧室改善燃烧.在该系统上进行了定功率-不同转速以及额定转速-不同功率下的节油试验,表明:该系统在高低功率条件下均有较好的节油和节能效果.柴油机转速为1 500 r/min时,节油率最高可达40％,节能率最高可达13.5％;在柴油机额定转速2 000 r/min时,节油率最高可达24％,节能率最高可达5.7％.结合乙醇热解的气体混合物的测量数据,得出了低功率下主要依靠乙醇蒸气,高功率下主要依靠小分子气体的节油原理.     

Thermal performance of a meso-scale liquid-fuel combustor

Combustion in small scale devices poses significant challenges due to the quenching of reactions from wall heat losses as well as the significantly reduced time available for mixing and combustion. In the case of liquid fuels there are additional challenges related to atomization, vaporization and mixing with the oxidant in the very short time-scale liquid-fuel combustor. The liquid fuel employed here is methanol with air as the oxidizer. The combustor was designed based on the heat recirculating concept wherein the incoming reactants are preheated by the combustion products through heat exchange occurring via combustor walls. The combustor was fabricated from Zirconium phosphate, a ceramic with very low thermal conductivity (0.8 W m⁻¹ K⁻¹). The combustor had rectangular shaped double spiral geometry with combustion chamber in the center of the spiral formed by inlet and exhaust channels. Methanol and air were introduced immediately upstream at inlet of the combustor. The preheated walls of the inlet channel also act as a pre-vaporizer for liquid fuel which vaporizes the liquid fuel and then mixes with air prior to the fuel–air mixture reaching the combustion chamber. Rapid pre-vaporization of the liquid fuel by the hot narrow channel walls eliminated the necessity for a fuel atomizer. Self-sustained combustion of methanol–air was achieved in a chamber volume as small as 32.6 mm³. The results showed stable combustion under fuel-rich conditions. High reactant preheat temperatures (675 K–825 K) were obtained; however, the product temperatures measured at the exhaust were on the lower side (475 K–615 K). The estimated combustor heat load was in the range 50 W–280 W and maximum power density of about 8.5 GW/m³. This is very high when compared to macro-scale combustors. Overall energy efficiency of the combustor was estimated to be in the range of 12–20%. This suggests further scope of improvements in fuel–air mixing and mixture preparation.     

Combustion characteristics of a charcoal slurry in a direct injection diesel engine and the impact on the injection system performance

The paper presents the research results pertaining to the renewable biomass charcoal-diesel slurries and their use as alternative fuels for combustion in diesel generating plants. The utilization of charcoal slurry fuel aims to reduce diesel oil consumption and would decrease fossil green house emissions into the atmosphere. The paper investigates the formulation, emulsification, sprays, combustion, injection system operation, and subsequent wear with charcoal-diesel slurries. In the research, cedar wood chips were used for the production of charcoal to be emulsified with diesel oil. The slurry’s viscosity of 27 cP achieved the target (<100 cP) and gave prospects of good spray atomization and while maintaining a high calorific value. Thermal analysis studies found that cedar wood will oxidize about 75% of its original mass by 450 °C. Charcoal slurry displayed a high vaporization rate of 75% by wt. at 300 °C. Engine investigations showed that the top combustion pressure at 1200 rpm and 100% load (7.8 brake mean effective pressure (bmep)) was 79 bar for diesel fuel and 78 bar for the charcoal slurry fuel. From the injection and heat release history was found an ignition delay of 1.7 ms for diesel that increased to 2.1 ms for the slurry fuel. A higher net heat release for charcoal slurry was observed, up to 180 J/crank angle degrees (CAD) compared with the diesel at 145 J/CAD The maximum combustion temperature reached 2300 K for diesel and 2330 K for slurry. The heat fluxes for both fuels have similar values and trends during the entire cycle showing the good compatibility of charcoal slurry with a diesel type combustion and low soot radiation. The exhaust temperatures were about 40-50 °C higher for charcoal slurry at 19° before top dead center (BTDC) injection timing. The engine’s bsfc increased as expected due to the lower heating value of the slurry fuel. The smoke Bosch no. was lower for the slurry fuel at any load, and is believed that the oxygen from the charcoal had a beneficial effect. The measured emissions of slurry fuel were better at 13° BTDC than those of diesel fuel with the original engine settings and the remaining 6-10% oxygen content in the charcoal is thought to have a paramount role in helping the diffusion type combustion and diminishing the particulate matter formation. As the load was increased, the amount of time it took to notice a decline in engine efficiency decreased. This was due to the injector sticking open which was seen by a sharp increase in the exhaust temperature. The internal flow into the injector had the tendency to form deposits on the injector’s seat that were critical to the functionality of the injector. In order to alleviate this problem, a reduced charcoal particle size together with a new injector design were produced resulting in stable engine efficiency at 50% load for a period of 90 min without injector sticking. Even with improvements, the needle’s seat into the injector body showed an accelerated wear 4-8 times faster than that in normal operation with diesel fuel and this cannot be sustained for long operational cycles. The investigations have proven that the new charcoal-diesel slurry can produce adequate sprays and burn with very good results in a direct injection diesel engine. The critical aspect of operation is the internal flow into the injector with the tendency to form deposits and wear in the injector.     

Experimental heat release analysis and emissions of a HSDI diesel engine fueled with ethanol–diesel fuel blends

An experimental study is conducted to evaluate the effects of using blends of ethanol with conventional diesel fuel, with 5%, 10% and 15% (by vol.) ethanol, on the combustion and emissions of a standard, fully instrumented, four-stroke, high-speed, direct injection (HSDI), ‘Hydra’ diesel engine located at the authors’ laboratory. The tests are conducted using each of the above fuel blends or neat diesel fuel, with the engine working at a speed of 2000 rpm and at four different loads. In each test, combustion chamber and fuel injection pressure diagrams are obtained using a specially developed, high-speed, data acquisition and processing system. A heat release analysis of the experimentally obtained cylinder pressure diagrams is developed and used, with the pertinent application of the energy and state equations. From the analysis results, plots of the history in the combustion chamber of the gross heat release rate and other related parameters reveal some very interesting features, which shed light on the combustion mechanism when using these blends. Moreover, for each test, volumetric fuel consumption, exhaust smokiness and exhaust regulated gas emissions are measured. The differences in the performance and exhaust emission parameters from the baseline operation of the diesel engine, i.e., when working with neat diesel fuel, are determined and compared. The heat release analysis results for the relevant combustion mechanism, combined with the widely differing physical and chemical properties of the ethanol against those for the diesel fuel, are used to aid the correct interpretation of the observed engine behavior.     

The effect of EGR and hydrogen addition to natural gas on performance and exhaust emissions in a diesel engine by AVL fire multi-domain simulation,GPR model,and multi-objective genetic algorithm

In this study, the effect of adding hydrogen to natural gas and EGR ratio was conducted on a diesel engine to investigate the engine performance and exhaust gases by AVL Fire multi-domain simulation software.For this investigation, a mixture of hydrogen fuel and natural gas replaced diesel fuel. The percentage of hydrogen in blend fuel changed from 0% to 40%. The compression ratio converted from 17:1 to 15:1. The EGR ratios were in three steps of 5%, 10%, and 15%, with different engine speeds from 1000 to 1800 RPM. The Gaussian process regression (GPR) was developed to model engine performance and exhaust emissions. The optimal values of EGR and the percentage of hydrogen in the blend of HCNG were extracted using a multi-objective genetic algorithm (MOGA).The results showed that by increasing EGR, thermal efficiency, the engine power, and specific fuel consumption decreased due to prolongation of combustion length while cumulative heat release increased but, its effect on cylinder pressure is insignificant. Adding hydrogen to natural gas increased the combustion temperature and, consequently NOx. While the amount of CO and HC decreased. The results of GPR and MOGA illustrated that at different engine speeds, the optimum values of EGR and HCNG were 6.35% and 31%, respectively.     

On the capabilities and limitations of predictive,multi-zone combustion models for hydrogen-diesel dual fuel operation

Compared with traditional hydrocarbon fuels, hydrogen provides a high-energy content and carbon-free source of energy rendering it an attractive option for internal combustion engines. Co-combusting hydrogen with other fuels offers significant advantages with respect to thermal efficiency and carbon emissions.This study seeks to investigate the potential and limitations of multi-zone combustion models implemented in the GT-Power software package to predict dual fuel operation of a hydrogen-diesel common rail compression ignition engine. Numerical results for in-cylinder pressure and heat release rate were compared with experimental data. A single cylinder dual-fuel model was used with hydrogen being injected upstream of the intake manifold. During the simulations low (20 kW), medium (40 kW) and high (60 kW) load conditions were tested with and without exhaust gas recirculation (EGR) and at a constant engine speed of 1500 rpm. Both single and double diesel injection strategies were examined with hydrogen energy share ratio being varied from 0 to 57% and 0–42 respectively. This corresponds to a range in hydrogen air-equivalence ratios of approximately 0–0.29.The results show that for the single-injection strategy, the model captures in-cylinder pressure and heat release rate with good accuracy across the entire load and hydrogen share ratio range. However, it appears that for high hydrogen content in the charge mixture and equivalence ratios beyond the lean flammability limit, the model struggles to accurately predict hydrogen entrainment leading to underestimated peak cylinder pressures and heat release rates. For double-injection cases the model shows good agreement for hydrogen share ratios up to 26%. However, for higher energy share ratios the issue of erroneous hydrogen entrainment into the spray becomes more accentuated leading to significant under-prediction of heat release rate and in-cylinder pressure.     

Hydrogen impacts on performance and CO2 emissions from a diesel power generator

This work investigates the performance and carbon dioxide (CO₂) emissions from a stationary diesel engine fueled with diesel oil (B5) and hydrogen (H₂). The performance parameters investigated were specific fuel consumption, effective engine efficiency and volumetric efficiency. The engine was operated varying the nominal load from 0 kW to 40 kW, with diesel oil being directly injected in the combustion chamber. Hydrogen was injected in the intake manifold, substituting diesel oil in concentrations of 5%, 10%, 15% and 20% on energy basis, keeping the original settings of diesel oil injection. The results show that partial substitution of diesel oil by hydrogen at the test conditions does not affect significantly specific fuel consumption and effective engine efficiency, and decreases the volumetric efficiency by up to 6%. On the other hand the use of hydrogen reduced CO₂ emissions by up to 12%, indicating that it can be applied to engines to reduce global warming effects.     

Synergistic integration of a gas turbine and solid oxide fuel cell for improved transient capability

A theoretical solid oxide fuel cell–gas turbine hybrid system has been designed using a Capstone 60 kW micro-gas turbine. Through simulation it is demonstrated that the hybrid system can be controlled to achieve transient capability greater than the Capstone 60 kW recuperated gas turbine alone. The Capstone 60 kW gas turbine transient capability is limited because in order to maintain combustor, turbine and heat exchangers temperatures within operating requirements, the Capstone combustor fuel-to-air ratio must be maintained. Potentially fast fuel flow rate changes, must be limited to the slower, inertia limited, turbo machinery air response. This limits a 60 kW recuperated gas turbine to transient response rates of approximately 1 kW s⁻¹. However, in the SOFC/GT hybrid system, the combustor temperature can be controlled, by manipulating the fuel cell current, to regulate the amount of fuel sent to the combustor. By using such control pairing, the fuel flow rate does not have to be constrained by the air flow in SOFC/GT hybrid systems. This makes it possible to use the rotational inertia of the gas turbine, to buffer the fuel cell power response, during fuel cell fuel flow transients that otherwise limit fuel cell system transient capability. Such synergistic integration improves the transient response capability of the integrated SOFC gas turbine hybrid system. Through simulation it has been demonstrated that SOFC/GT hybrid system can be developed to have excellent transient capability.     

Waste heat recovery from a landfill gas-fired power plant

Waste treatment and management is a certain challenge especially in areas with high population density. One of the options for waste treatment is landfilling, where the amount of municipal waste also produces landfill gas through anaerobic digestion. The heating value of the landfill gas is high enough to use it as a fuel in combustion processes, e.g. in internal combustion engines (ICEs) to produce electric power.In Ano Liosia, Athens (Greece) up to 6000 tons of waste are landfilled every day and the landfill gas is used in an ICE power station directly at the site of the landfill. The power station consists of 15 ICEs and has an installed capacity of 23.5 MW. The major advantages of using ICE for power generation are the high electrical efficiency of ICEs and their fast load response. However, more than 50% of the landfill gas energy content is still released to the atmosphere as engine waste heat (exhaust gas and engine cooling water).The aim of this paper is to study the possibilities of using this large amount of heat in order to increase the electricity production and efficiency of the Ano Liosia power station. Therefore, a thermodynamic and economic analysis of two different waste heat recovery (WHR) systems is conducted. The water/steam cycle and the Organic Rankine Cycle (ORC) are examined and evaluated by means of thermodynamic cycle simulation and by calculating their specific costs of power generation. Their advantages and disadvantages considering their application in landfillgas-fired ICE power stations are discussed under the consideration of maximal thermodynamic efficiency and minimal costs of power generation.     

车用柴油机节能潜力的能质分析方法与试验研究

在热平衡分析基础上建立了柴油机能质分析的平衡计算模型,并以WD615(162kW)型车用柴油机为对象进行了试验研究,对比分析柴油机工作过程中的能质分布规律和节能潜力。结果表明:在冷却水及排气能量利用之前,柴油机的热平衡规律和有效能利用率一致。在柴油机最大扭矩点(约1 600r/min),系统有效功占总热量的百分比达到最大值,效率、冷却水和排气的可用能比例也达到最大,约有17%的可用能还未得到利用。不可逆燃烧、有限温差传热和摩擦损耗等因素降低了系统能量的能级,减少柴油机系统的损同时梯级利用排气及冷却水能量,是车用柴油机节能的可行手段。分析方法也为柴油机的效率评价提供了一种新的参考方案。     

Performance of a single nutating disk engine in the 2 to 500 kW power range

A new type of internal combustion engine with distinct advantages over conventional piston-engines and gas turbines in small power ranges is presented. The engine has analogies with piston engine operation, but like gas turbines it has dedicated spaces and devices for compression, burning and expansion. The engine operates on a modified limited-pressure thermodynamic cycle. The core of the engine is a nutating non-rotating disk, with the center of its hub mounted in the middle of a Z-shaped shaft. The two ends of the shaft rotate, while the disk nutates. The motion of the disk circumference prescribes a portion of a sphere. In the single-disk configuration a portion of the surface area of the disk is used for intake and compression, a portion is used to seal against a center casing, and the remaining portion is used for expansion and exhaust. The compressed air is admitted to an external accumulator, and then into an external combustion chamber before it is admitted to the power side of the disk. The external combustion chamber enables the engine to operate on a variable compression ratio cycle. Variations in cycle temperature ratio and compression ratio during normal operation enable the engine to effectively become a variable-cycle engine, allowing significant flexibility for optimizing efficiency or power output. The thermal efficiency is similar to that of medium sized diesel engines. For the same engine volume and weight this engine produces approximately twice the power of a two-stroke engine and four times the power of a four-stroke engine. The computed sea-level engine performance at design and off-design conditions in the 2 to 500 kW power range is presented.     

A highly efficient six-stroke internal combustion engine cycle with water injection for in-cylinder exhaust heat recovery

A concept adding two strokes to the Otto or Diesel engine cycle to increase fuel efficiency is presented here. It can be thought of as a four-stroke Otto or Diesel cycle followed by a two-stroke heat recovery steam cycle. A partial exhaust event coupled with water injection adds an additional power stroke. Waste heat from two sources is effectively converted into usable work: engine coolant and exhaust gas. An ideal thermodynamics model of the exhaust gas compression, water injection and expansion was used to investigate this modification. By changing the exhaust valve closing timing during the exhaust stroke, the optimum amount of exhaust can be recompressed, maximizing the net mean effective pressure of the steam expansion stroke (MEP_steam). The valve closing timing for maximum MEP_steam is limited by either 1 bar or the dew point temperature of the expansion gas/moisture mixture when the exhaust valve opens. The range of MEP_steam calculated for the geometry of a conventional gasoline engine and is from 0.75 to 2.5 bars. Typical combustion mean effective pressures (MEP_combustion) of naturally aspirated gasoline engines are up to 10 bar, thus this concept has the potential to significantly increase the engine efficiency and fuel economy.     

Efficiency of hydrogen internal combustion engine combined with open steam Rankine cycle recovering water and waste heat

A hydrogen internal combustion engine (HICE) wastes more heat, and producing nearly three times more water than a conventional engine. This paper describes the principle behind a novel waste heat recovery sub-system that exploits the water produced by an HICE as the working fluid for an open-cycle power generation system based on the Rankine cycle. Water from the HICE exhaust is superheated by the waste heat from the HICE and used to produce power in a steam expander. A fundamental thermodynamic model shows the contribution of the sub-system to the overall thermal efficiency of the HICE at various engine speeds, with and without a condenser. The results show that the condenser is not cost-effective and that the overall thermal efficiency with the proposed sub-system is 27.2% to 33.6%, representing improvements of 2.9% to 3.7%, at engine speeds of 1500 to 4500 rpm.     

Biodiesel fuel in diesel micro-turbine engines: Modelling and experimental evaluation

Many performance and emission tests have been carried out in reciprocating diesel engines that use biodiesel fuel over the past years and very few in gas turbine engines. This work aims at assessing the thermal performance and emissions at full and partial loads of a 30 kW diesel micro-turbine engine fed with diesel, biodiesel and their blends as fuel. A cycle simulation was performed using the Gate Cycle GE Enter software to evaluate the thermal performance of the 30 kW micro-turbine engine. Performance and emission tests were carried out on a 30 kW diesel micro-turbine engine installed in the NEST laboratories of the Federal University of Itajubá, and the performance results were compared with those of the simulation. There was a good agreement between the simulations and the experimental results from the full load down to about 50% of the load for diesel, biodiesel and their blends. The biodiesel and its blends used as fuel in micro-turbines led to no significant changes in the engine performance and behaviour compared to diesel fuel. The exhaust emissions were evaluated for pure biodiesel and its blends and conventional diesel. The results revealed that the use of biodiesel resulted in a slightly higher CO, lower NO_x and no SO₂ emissions.     

Performance analysis of a trigeneration system based on a micro gas turbine and an air-cooled,indirect fired,ammonia–water absorption chiller

The objective of this paper is to experimentally determine the efficiency and viability of the performance of an advanced trigeneration system that consists of a micro gas turbine in which the exhaust gases heat hot thermal oil to produce cooling with an air cooled absorption chiller and hot water for heating and DHW. The micro gas turbine with a net power of 28 kW produces around 60 kW of heat to drive an ammonia/water air-cooled absorption chiller with a rated capacity of 17 kW. The trigeneration system was tested in different operating conditions by varying the output power of the micro gas turbine, the ambient temperature for the absorption unit, the chilled water outlet temperature and the thermal oil inlet temperature. The modelling performance of the trigeneration system and the electrical modelling of the micro gas turbine are presented and compared with experimental results. Finally, the primary energy saving and the economic analysis show the advantages and drawbacks of this trigeneration configuration.     

未着火循环废气改善柴油机冷起动的燃烧

采用柴油的替代研究燃料正庚烷和压燃式燃烧模型,计算研究了起动阶段引入未着火循环的燃烧产物对下一循环燃烧的影响.未着火循环的燃烧产物与完全燃烧循环有明显不同,其中含有许多未燃燃油和中间活性物质,将其以EGR的方式重新引入气缸中能有效改善下一循环的燃烧,计算结果表明,中间活性物质起到了关键作用.进行了EGR影响柴油机起动性能的试验研究,结果表明,起动初期的循环中,引入EGR可以改善燃烧,试验结果验证了计算分析的合理性,为改善柴油机冷起动性能提供了一种新思路.根据正庚烷燃烧的化学动力学理论,结合计算过程中各物质浓度的变化,研究了EGR改善燃烧的机理.