柴油发电机环境低频噪声影响防治初探

以设在民用住宅里的柴油发电机环境低频噪声对环境的影响为研究对象,就柴油发电机环境低频噪声对环境敏感点的影响进行监测,了解民用住宅里的柴油发电机环境噪声对环境的影响水平,参照我国的国家标准作环境影响评价,探讨民用住宅里的柴油发电机环境低频噪声对环境的污染防治对策.     

Comparison of jatropha and karanja biofuels on their combustion characteristics

Biofuel blends produced from Jatropha (Jatropha curcas) and Karanja (Pongamia pinnata) oil were evaluated for their combustion properties. Two kinds of blends (regular diesel with Jatropha and Karanja oil) were prepared at 20% volume to the diesel and tested as alternative fuels in single cylinder (vertical), water-cooled, direct injection diesel engine at the rated speed of 1500 rpm. The performance of the engine in terms of thermal efficiency at full load for diesel was 30%. For Jatropha and Karanja biodiesel blends, the thermal efficiencies were 29.0% and 28.6%, respectively. The maximum cylinder pressure and ignition delay for biodiesel fuel blends are very close to that of regular diesel. Prolonged combustion was observed for Karanja oil blend in comparison to Jatropha oil blend. The combustion pattern also reveals the slow burning characteristics of vegetable oils and this study indicates that the blended biofuels have combustion characteristics that are similar to regular diesel fuels.     

Performance analysis of bioethanol (Water Hyacinth) on diesel engine

The increasing consumption and excessive extraction of conventional fuels is the matter of serious concern. Nowadays, world is looking for alternative sources of fuel which can partially replace conventional fuel dependence. The current investigation intends to provide evaluation of bio-ethanol preparation from Water Hyacinth (WH) and its influence on diesel engine performance under various operating conditions. This study explores the extraction of glucose from WH (Eichhornia crassipes) pretreated with sulfuric acid (H₂SO₄) for production of bio-ethanol. For the production of bio-ethanol different concentrations of H₂SO₄ acid hydrolysate (1%, 2%, 4%, 6%, 8%, and 10%) were prepared which was then followed by fermentation with cellulose fermenting yeasts. From results, it was observed that 4% H₂SO₄ acid hydrolysis produces higher concentrations of ethanol than other concentrations. Bio-ethanol extracted from WH was blended with diesel in different proportions (5%, 10%, 15%, 20%, and 25%) v/v and performance and emissions were experimentally investigated on single cylinder diesel engine under various load conditions. Experimental results show that 5 BED [5% bio-ethanol (WH + 95%diesel v/v) and 10BED (10% bio-ethanol (WH + 90%diesel v/v)] produces higher brake power, brake thermal efficiency and brake mean effective pressure with improved exhaust emission profiles than any other blend.     

纳米氧化铈对汽油发动机尾气污染物排放的影响

通过非水微乳液法制备了纳米氧化铈,并将之添加到90^#汽油中,研究了纳米氧化铈对汽油动力性能、尾气污染物CO、HC、PM、NOx排放的影响。结果表明：非水微乳液法制备的纳米氧化铈粒径在30～50nm之间,粒径分布较窄;添加浓度为100mg／L时,不会对汽油的动力性能产生明显影响,但可以明显降低90。汽油尾气中的CO、HC、PM、NOx排放。其中,800r／min的正常怠速下可以降低CO排放19．39％、HE排放19．92％、NOx排放51．19％、PM排放25％;在2000r／min的高怠速下可降低CO排放16．17％、NOx排放46．92％、PM排放16．67％。     

An investigation of engine and fuel system performance in a diesel engine operating on waste cooking oil

Waste cooking oil (WCO) was experimentally examined to determine whether it can be used as an alternative fuel in a 3-cylinder, 4-stroke, direct injection, 48 kW power tractor engine. The test engine was operated under full load conditions using diesel fuel and waste vegetable oil from the 2400 to 1100 rpm and performance values were recorded. Tests were performed in two stages to evaluate the effect of the waste oils on the engine life cycle. When the test engine was operated with diesel fuel and waste cooking oil; engine torque decreased between at ratio of 0.09 % and 3% according to the engine speed. While no significant difference occurs in the diesel fuel tests at the end of 100 hours of operation, an important reduction was observed in the engine torque of the WCO engine between 4.21% and 14.48% according to the engine speed, and an increase in average smoke opacity ratio was also observed. In accordance with the results obtained from the studies, it was determined that the engine performance values of waste cooking oil show similar properties with diesel fuel, but in long-term usage, performance losses increased. In the SEM analysis performed on the fuel system, there were dark deposits at the nozzle tip and stem. According to an EDX analysis at the nozzle tips, the detected elements point to engine oil ash in the combustion chamber and show coking products (C and O). The other elements (Na, S, Ca, P, Cl, and K) point to used WCO.     

Effects of fuel reactivity and injection timing on diesel engine combustion and emissions

Recent strategies for simultaneously reducing NOx and soot emissions have focused on achieving nearly premixed, low-temperature combustion (LTC) in diesel engines. A promising approach in this regard is to vary fuel reactivity in order to control the ignition delay and optimize the level of premixing and reduce emissions. The present study examines such a strategy by performing 3-D simulations in a single-cylinder of a diesel engine. Simulations employ the state-of-the-art two-phase models and a validated semi-detailed reaction mechanism. The fuel reactivity is varied by using a blend of n-heptane and iso-octane, which represent surrogates for gasoline and diesel fuels, respectively. Results indicate that the fuel reactivity strongly influences ignition delay and combustion phasing, whereas the start of injection (SOI) affects combustion phasing. As fuel reactivity is reduced, the ignition delay is increased and the combustion phasing is retarded. The longer ignition delay provides additional time for mixing, and reduces equivalence ratio stratification. Consequently, the premixed combustion is enhanced relative to diffusion combustion, and thus the soot emission is reduced. NO_x emission is also reduced due to reduced diffusion combustion and lower peak temperatures caused by delayed combustion phasing. An operability range is observed in terms of fuel reactivity and SOI, beyond which the mixture may not be sufficiently well mixed, or compression ignited. The study demonstrates the possibility of finding an optimum range of fuel reactivity, SOI, and EGR for significantly reducing engine out emissions for a given load and speed.     

PPS滤布对柴油机排放PM的过滤效率

基于柴油机实验台架和颗粒捕集装置,采用聚苯硫醚(PPS)针刺毡滤布过滤柴油机排放的颗粒物(PM)。利用称重法,以Whatman玻璃纤维滤纸为对比滤纸,间接测试了3种PPS滤布的过滤效率;同时实验探索了表面涂覆聚四氟乙烯的PPS滤布的深床过滤时间。实验结果表明,3种滤布在180℃的加热条件下将出现颜色和形态的变化;3种滤布在深床过滤期对PM的平均过滤效率分别为78.8%、76.9%和83.7%;表面涂覆聚四氟乙烯的PPS滤布的深床过滤时间为15~20 min,此后其过滤效率可接近100%。     

资源型催化剂净化柴油机尾气

本文使用含有稀土金属和过渡金属元素以及只含有过渡金属元素的矿石制备了多种资源型催化剂,并在柴油机台架上进行筛选和活性评价.结果表明,含有稀土金属和过渡金属复合氧化物的ZC-1号催化剂和只含有过渡金属氧化物,但添加助催化剂的ZC-4号催化剂具有较好的温度特性、空速特性、热稳定性和抗积碳性能,其中ZC-1号催化剂的性能最优.对ZC-1号催化剂进行了700h的使用寿命考察,未见其活性降低。     

Thermal barrier coated diesel engine running on biodiesel: a review

Thermal barrier coated diesel engine, also known as low heat rejection (LHR) engine have offered the promise of reducing heat rejection to the engine coolant and increase the combustion temperature which results in increase of thermal efficiency, decrease of fuel consumption and emission rate of the engine. Biodiesel derived from the vegetable oils are a promising alternative fuel for diesel fuel. The viscosity of vegetable oil after transestrification is still higher than that of diesel fuel. The various researchers have reported that the energy of the biodiesel could be released more efficiently with the concept of LHR engine. In the case of LHR engine running on different biodiesel blends, almost all experimental studies has predicted improved performance. This paper analyses and discussed the operating conditions under which the experimental studies are carried out and the factors which affect thermal efficiency and exhaust emissions in LHR engine.     

Dynamic simulation and performance prediction of free displacer Stirling engines

ABSTRACT

In this study, a Stirling engine with a free-displacer and a kinematically controlled power piston was proposed and analyzed from thermodynamic and dynamic points of view. The analysis intended to reveal the dynamic behaviors of moving components of the engine as well as predicting global thermal performance of it. A dynamic-thermodynamic mathematical model of the engine involving the isothermal gas pressure equation and motion equations of the displacer, power piston and crankshaft was developed. For the solution of the dynamic-thermodynamic model equations, and simulation of the engine’s running, a computer program was prepared in FORTRAN language. By considering a hot-end temperature of 1,000 K and a cold-end temperature of 350 K, dimensions of mechanic, volumetric and thermal components of the engine were quantified interactively. Variations of engine speed, engine power, displacer stroke, and engine torque were examined with respect to the spring constant, displacer mass, displacer damping constant and external load and, results were graphically presented. In comparison with engines having free-piston and kinematically driven displacer, the thermodynamic performance of the free-displacer engine was found to be lower. The engine was found to be able to work at constant speed and power. The values of the displacer mass and spring constant were optimized as 1,500 g and 1,30,000 N/s, respectively and the global speed of the engine was determined to be 47.75 Hz for these values. The effective and the indicated work of the engine were determined to be 113 and 126 J, respectively.