Numerical study on the characteristics of HCCIcombustion process of primary reference fuels

The combustion process of HCCI engine fueled by primary reference fuels is simulated using the CHEMKIN software, and the results are compared with a combustion experiment of a HCCI engine. The cluthors study the influence of various factors, including fuel composition, compression ratio, equivalence ratio, initial temperature and initial pressure, on HCCI engine fueled with PRF. The results indicate that the ignition delay increases along with the increase of the octane number. The initial temperature, initial pressure, compression ratio, equivalence ratio have significant effects on the ignition timing. The operating range of the combustion on HCCI engine is limited.     

Kinetic characteristics of ignition process of diesel surrogate fuel

The purpose of this paper is to identify the effects of toluene and the toluene content which is at different initial temperatures on the ignition delay time of diesel surrogate fuel under homogeneous charge compression ignition (HCCI) engine condition. The CHEMKIN4.1 module (closed homogeneous batch reactor) is used with the constructed diesel surrogate fuel chemical kinetics model to simulate the constant volume. The results show that the ignition property is mainly characterized by n-heptane. The presence of the slowly oxidizing toluene in the surrogate fuel does not affect the auto-ignition time considerably. In addition,the influence of toluene content on the ignition delay time is significant only at low initial temperature. More ignition delayed combustion processes have been found when toluene content is increasing.     

PAHs formation mechanism during Combustion Process of Diesel Engines

Based on the diesel surrogate fuel (n-heptane and toluene), we develop a new kinetic mechanism of diesel surrogate fuel included polycyclic aromatic hydrocarbon (PAHs) formation and growth of up to five aromatic rings. The new mechanism included 153 species and 697 reactions. We compare it with various experimental data available in the literature including shock tube, n-heptane premixed flames and homogeneous charge compression ignition(HCCI) engine, and the results show the good performance for HCCI combustion prediction by this new mechanism. The presented mechanism can be used as the basis for further reductions and applied the combustion and emission simulation by coupling chemical reaction kinetics model with computational fluid dynamics model in internal combustion engines.     

Influence numerical analysis of combustion chamber thermal boundary conditions on unsteady combustion characteristics in micro ICE

To research the influence of combustion chamber thermal boundary conditions on micro combustion characteristics in micro ICE, the laminar flow finite rate model is adopted to simulate the micro combustion process. Firstly, the influence of grid scale, the time step length and the maximum iterations per time step on accuracy of simulation results are explored. The results show that simulation results agree well with experimental results. And then, the influences of heat transfer coefficient, wall thickness and material on combustion characteristics are discussed. The results indicate that heat transfer coefficient has obvious influence on combustion characteristics. The pressure rise rate decreases, the ignition delays and the highest pressure value drops 2 atmospheres as heat transfer coefficient increases from 0 to 55 W/(m 2·K). The wall thickness and material have a little effect on combustion characteristics. This is because that the main heat transfer resistance in the heat flow path from cylinder to external environment lies between the outer wall and environment.     

Effect of Mischmetal Additions on the Ignition Temperature ofMolten ZM5 Magnesium Alloy

Magnesium alloy is prone to burning during its melting and casting in air, which is a major factor in obstructing its application. Fluxes and cover gases are currently used for the melting and production processes, and semi solid thixocasting is also used to lower the operation temperature, but there still remain many problems. Alloying is a promising method of preventing Mg from burning. The effect of mischmetal additions on the ignition temperature of ZM5 Mg alloy was investigated and compared with that of pure rare earths. It is shown that an addition of 0.12 % mischmetal can greatly heighten the ignition point and such an alloy can be widely applied.     

Influence analysis of fuel quality on engine emission performance

Quality, composition, and characteristics of fuel from 7 areas of P. R. China were analyzed. Fuel quality factors influencing engine emission performance were studied. Using fuel from the HuaZhong and XiNan areas, engine COx, HC, and NOx emissions were tested by adjusting the excess air coefficient and the advanced ignition angle. In light of the characteristics of aromatic hydrocarbon and alkenes of fuel from different areas in P. R. China, we have shown engines can operate smoothly and engine emissions can be decreased when the excess air coefficient and the advanced ignition angle are properly adjusted.     

Effects of fuel injection and intake parameters on low temperature combustion

The effects of fuel injection and intake parameters on low temperature combustion are investigated using CFD modeling in the present study. With the increase of injection pressure or decrease of nozzle hole diameter:the maximum in-cylinder pressure and temperature increase. Heat release from premixed combustion increases at the same oxygen concentration and oxygen concentration that obvious premixed combustion appears increases. As to emissions, soot emission decreases because of the improvement of mixing of fuel and air and NOx emission increases because the increase of local temperature in the cylinder. With the increase of intake pressure:the maximum cylinder pressure increases but the maximum cylinder temperature decreases. The ignition timing advances at the same oxygen concentration. The combustion efficiency increases. As to emissions, both soot and NOx emissions decrease.     

运行参数对微型内燃机微燃烧特性影响机理分析

微型内燃机微燃烧过程对当量比和转速变化非常敏感,采用层流有限速率模型和甲醇氧化反应机理对其预混层流微燃烧过程开展仿真研究,探讨当量比和转速对微燃烧特性的影响规律及临界运行参数。在此基础上,提出采用热着火理论和化学反应动力学理论探索当量比对微燃烧特性的影响机理。结果表明仿真与实验比较吻合。当量比从0.6增加到1.1时,燃烧速率增加,压力和温度增加,压力最高值增加约1.5E+6 Pa,温度最大值增加约1 300 K,此后随当量比增加,燃烧速率减小,压力和温度减小。研究还进一步揭示了当量比影响微燃烧特性的机理: 稀燃区当量比主要通过温度变化来影响微燃烧特性,随当量比增加,燃料浓度增加,燃烧释放的总热量增加,所以温度和压力增加,燃烧速率增加;浓燃区当量比主要通过氧气量变化来影响微燃烧特性,当量比越大,氧气量越不足,基元反应速率越小,所以燃烧速率越小,温度和压力越低。转速越高,燃烧时间越短,燃烧越不充分,所以温度、压力越低。受微燃烧相对热损大、驻留时间短的特征影响,微型发动机实现完全燃烧的运行区域较窄,其实现完全燃烧的稀燃极限约0.9,最高转速约6 000 r/min。这在设计微型内燃机时值得关注。     

Carbonyl Emission Influenced by Combustion Process of Diesel Engine

The bench test of diesel engine is conducted fueled with biodiesel, diesel and blending fuel, the changes of cylinder pressure with crank angle is also measured, combined with the measurement results of carbonyl emissions, the theoretical relationship between combustion process and carbonyl formation is analyzed. The results show that, combustion intermediates such as C7, C5, CO and C2H2 are produced in the fuel oxidation process during the premixed combustion phase. The diffusion combustion period extend with the increase of load, and it is the main stage of re-oxidation and decomposition for the intermediate products, the cylinder temperature and pressure increase with the increase of load, while the ignition delay period is shortened, the probability of oxidation and conversion for carbonyl pollutants improve because of the extended residence time in the high-temperature and high pressure region, the high exhaust temperature in high load is conducive to the re-oxidation of carbonyl emissions.     

The study on EMI principle and suppression method of vehicle ignition system

Vehicle ignition system is the main electromagnetic interference source. Electromagnetic radiation produced by ignition system will produce the interference to electromagnetic environment around. It is necessary to study the electromagnetic interference (EMI) principle, noise paths and suppression method. We analyze the electromagnetic interference principle of ignition system, and harness trouble-shooting related to electromagnetic interference is also tested. Results show that the spark discharge between spark plug electrodes is the main interference source in ignition system. Then, the paths of conducted interference and the reason of radiated emission are discussed in detail. Finally, two kinds of power supply cord EMI filters are designed and implemented on the basis of analysis results. Experimental results indicate that the filter can reduce the noise of power-wire in broadband range. Simultaneously, the radiation emission performance from power wire is also reduced observably. The proposed mixing filter has been demonstrated in this paper to perform satisfactorily with excellent effectiveness in suppression of conducted EMI from 10 MHz to 110 MHz, and the object car can also pass the EMC standard tests.     

The optical isolation method of suppressing electromagnetic interference of automotive ignition system

Electromagnetic radiation, which is caused by the engine ignition system, is the most powerful electromagnetic interference (EMI) source in the vehicles, as well as the main reason of most electronic control unit (ECU) malfunction. In order to reduce interference from ignition noise on ECU, we use optical isolation technology to isolate electrical connections between the interference source and the control circuit. The formation mechanism of the ignition system EMI is analyzed. The possibility of suppressing ignition system EMI with optical isolation technology is discussed. Then, as a result we design an experimental platform of suppressing ignition system EMI. The experimental results show that the effect of suppressing ignition noise, in 20~100 MHz frequency band, is obvious after applying optical isolation circuit. It can address the issue of automotive EMC.     

Effects of Seeding Date and Topping Date on Yield and Fiber Quality of Short-Season Cotton Field-Seeded after Barley(Rape)/Wheat Harvest

[Objective] The aim of this study was to evaluate the effects of seeding date and topping date on yield, yield characteristics and fiber quality of short-season cotton (CCRI 50) field-seeded after barley(rape)/wheat harvest. [Method] A split-plot design with three replicates was used for the study in Nanjing, Jiangsu province of China in 2014-2015. The main plots comprised two seeding dates (S₁: 25th May and S₂: 10th June), while topping dates (T₁: 30th July, T₂: 7th August and T₃: 15th August) constituted the subplots. [Result] The lint yield, the ratio of yield before frost, boll number, boll weight and lint percent of S₂ were lower than those of S₁. The number of fruit branches and fruit nodes of S₂ were less than those of S₁ while it was the opposite for the boll setting ratio. The lint yield and the ratio of yield before frost decreased with the delay of topping date. The number of fruit branches and fruit nodes, the ratio of them increased with the delay of topping date while the boll setting ratio decreased. The interaction of sowing date × topping date showed that the treatment of S₁T₁ achieved higher value in lint yield and the ratio of yield before frost. The higher number of fruit branches and fruit nodes were found at the treatment of S₁T₁, S₁T₂ and S1T3 and higher boll setting ratio were found at the treatment of S₂T₁ and S₁T₁. Correlation analysis showed that the lint yield positively and significantly correlated with the number of fruit branches and fruit nodes and boll number, but did not significantly correlate withboll setting ratio and the ratio of fruit branches number to nodes number. In addition, the boll distribution ratios of middle and low fruit branches of S₂ were more than those of S₁ while it was the opposite for that of up fruit branches. The boll distribution ratios of middle and low fruit branches decreased with the delay of topping date while it was the opposite for that of up-fruit branches. The treatment of S₁T₁ could be better to improve fiber length and fiber strength of different fruit branches and the micronaire value of middle fruit branches. [Conclusion] The treatment of S₁T₁ is conducive to high yield and fiber quality of short-season cotton field-seeded after barley(rape)/wheat harvest in lower reaches of the Yangtze River.     

1961—2018年吉林省水稻低温冷害时空变化特征

为了研究吉林省水稻低温冷害时空演变规律,采用水稻生长发育和产量形成气象影响模式,判定吉林省1961—2018年水稻障碍型和延迟型冷害,利用数理统计方法分析水稻低温冷害时空变化特征。结果表明:1961—2018年吉林省水稻障碍型和延迟型低温冷害发生站数比呈降低趋势,障碍型低温冷害主要以轻度冷害为主,中度次之,重度最少。重度延迟型冷害发生站数比高于轻度和中度冷害。障碍型冷害发生站数比在1981—1990年最高,延迟型冷害发生站数比在1971—1980年最高。吉林省水稻障碍型低温冷害发生频率呈由西向东逐渐升高的趋势,20世纪90年代之后,冷害主要分布在东部。延迟型冷害发生频率也由西向东逐渐上升,但轻度和中度冷害主要集中分布在中西部,重度冷害主要集中在东部。研究成果可为吉林省合理搭配不同熟性的水稻品种,充分利用热量资源,抵御低温冷害提供保障。     

黑龙江省季节性冻土的气候特征分析

为进一步研究高纬度地区冻土的气候特征,本研究采用统计分析方法和IDW方法分析了黑龙江省1961—2016 年季节性冻土区冻土要素的时空分布特征。结果表明：（1）黑龙江省最大冻土深度的多年平均值约为171.6 cm,呈显著减小趋势。各地区（除了通河）的最大冻土深度均呈显著减小的趋势。（2）冻土初日平均在10 月23 日,呈显著推迟的趋势。全省绝大部分地区的冻土初日推迟,省西部地区的推迟速率要大于省东部地区。（3）冻土终日平均在5 月29 日,呈显著提前的趋势。全省大多数地区的冻土终日均显著提前,尤其是克山、海伦、安达和伊春,提前速率在6.3~9.8 d/10 a 之间。（4）冻土期平均约为218 天,呈显著减少的趋势。各地区冻土期纬向分布比较明显,且均呈不同程度的减少趋势,省西部地区的减少速率要大于东部地区。研究结果可为应对气候变化、工程气象以及短期气候预测、生态气候领域的进一步研究做基础。     

Investigation on the reaction characteristics of methane catalytic partial oxidation in a micro-channel

The reaction characteristics of fuel-lean CH4 catalytic partial oxidation over Rh are investigated numerically in a micro-channel, by using detailed elementary mechanism, focusing on the effects of inlet temperature, equivalence ratio of CH4/O2 and added H2O on catalytic partial oxidation of CH4. The results show that over Rh surface reaction of CH4 is kinetically controlled, while that of O2 is controlled by mass transport. Duo to the high reactivity of O2, CH4 is firstly oxidized and both complete and partial oxidation products are generated. After O2 is consumed, steam reforming begins, however, CO2 reforming does not appear. Increase of the equivalence ratio of C/O leads to increase of carbon deposition at reforming zoon, as thus both conversion of CH4 and production of syngas decrease, even the reforming process is stopped. The added H2O could dramatically inhibit carbon deposition, and promote the formation of H2 and CO2.     

不同播期对糜子不同品种生长发育及产量的影响

为探讨不同播期对糜子不同品种生长发育及产量的影响,以6个糜子品种为试验材料,在山西晋中榆次设5个播期试验,研究了播期对糜子品种发育及产量的影响。结果表明：晋中当地播期B5（7月15日）糜子不能安全成熟。其余4个播期糜子均能正常成熟,且随着播期的推迟,各品种生育期都缩短,各品种株高、主茎节数、有效分蘖等形态特性及单穗长、单穗粒重、千粒重等经济性状整体上随着播期的推迟呈减小趋势。从产量来看,晋黍9号、汾黍6号适宜早播,在5月底播种,汾黍6号产量最高可达5 913.63kg/hm ²;伊糜5号、固糜21号、榆糜2号及保黍1号则宜晚播,6月初播种,榆糜2号产量最高可达6 306.96kg/hm ²。     

人工模拟盐、碱环境对向日葵种子萌发及幼苗生长的影响

以向日葵品种白葵杂6号为试验材料, 中性盐NaCl和Na₂SO₄混合模拟盐胁迫、碱性盐NaHCO₃和Na₂CO₃混合模拟碱胁迫(两者摩尔比均为9∶1), 设计各6种处理。研究盐、碱胁迫下种子萌发及幼苗形成的相关生理表现。结果表明, 种子能够萌发并成苗的最高盐胁迫强度是pH 6.98, 电导率为1.311 dS m^-1(培养介质的pH和电导率); 碱胁迫强度是pH 9.71, 电导率为0.360 dS m^-1。在能够成苗的盐碱条件下, 随着盐胁迫强度的增强出苗率、成苗率下降, 出苗时间明显延迟; 而随着碱胁迫强度的增加, 成苗率下降, 出苗时间并不延迟。同时随着盐碱胁迫强度的增强, 幼苗的各项生理指标均下降, 下降幅度以碱胁迫明显大于盐胁迫。试验结果证明, 盐胁迫和碱胁迫对白葵杂6号种子萌发及幼苗形成的影响机制不同, 向日葵在这两个阶段对盐碱两种胁迫的耐受能力及响应特点也不同。这一结论进一步证实了盐、碱胁迫是两种性质不同的胁迫。     

春玉米叶面积系数动态特征的密度效应

为进一步明确春玉米不同密度群体叶面积系数(LAI)特征参数的密度效应,以吉单209和郑单958为材料,于2005年和2006年在东北春玉米区(吉林)分别设置4.5~10.5万株 hm^-2 5个密度和3.0~12.0万株 hm^-2 7个密度处理试验,应用作物高产群体相对LAI动态普适模型方程y= (a+bx)/(1+cx+dx²)模拟分析不同密度对LAI动态特征参数的影响。结果表明,春玉米群体最大LAI在3.0~12.0万株hm^-2范围内随密度增加呈近似直线增大趋势,而最大LAI出现的时间随密度增加而提早;将LAI数据相对化处理后,不同密度群体的LAI差异在最大LAI之后较之前表现明显,高密度群体较低密群体LAI衰减迅速。全生育期平均LAI随密度增加呈显著线性增大趋势,而平均LAI与最大LAI的比率则随密度增加呈显著线性减小趋势。密度对模拟方程各参数均有不同程度的影响,相邻密度差异不明显,间隔3.0万株 hm^-2的差异显著;不同参数变化趋势不同,其中参数a接近“0”,受密度影响不大;b、c均随密度的增加而减小,d随密度的增加而增大。全生育期群体LAI变化速率呈“N”形变化趋势,且与群体LAI变化及生育期对应,高密度群体LAI增加及衰减的速率均大于低密度群体,拔节期和大喇叭口期为密度响应敏感期。由此可见,密度对春玉米全生育群体LAI动态具有调节作用,尤其群体LAI变化速率、最大LAI及其到达的时间、平均LAI及其与最大LAI的比率等重要特征参数对密度响应较为敏感,可作为对春玉米群体密度调控的参考指标。     

春玉米叶面积系数动态特征的密度效应

为进一步明确春玉米不同密度群体叶面积系数(LAI)特征参数的密度效应,以吉单209和郑单958为材料,于2005年和2006年在东北春玉米区(吉林)分别设置4.5~10.5万株 hm^-2 5个密度和3.0~12.0万株 hm^-2 7个密度处理试验,应用作物高产群体相对LAI动态普适模型方程y= (a+bx)/(1+cx+dx²)模拟分析不同密度对LAI动态特征参数的影响。结果表明,春玉米群体最大LAI在3.0~12.0万株hm^-2范围内随密度增加呈近似直线增大趋势,而最大LAI出现的时间随密度增加而提早;将LAI数据相对化处理后,不同密度群体的LAI差异在最大LAI之后较之前表现明显,高密度群体较低密群体LAI衰减迅速。全生育期平均LAI随密度增加呈显著线性增大趋势,而平均LAI与最大LAI的比率则随密度增加呈显著线性减小趋势。密度对模拟方程各参数均有不同程度的影响,相邻密度差异不明显,间隔3.0万株 hm^-2的差异显著;不同参数变化趋势不同,其中参数a接近“0”,受密度影响不大;b、c均随密度的增加而减小,d随密度的增加而增大。全生育期群体LAI变化速率呈“N”形变化趋势,且与群体LAI变化及生育期对应,高密度群体LAI增加及衰减的速率均大于低密度群体,拔节期和大喇叭口期为密度响应敏感期。由此可见,密度对春玉米全生育群体LAI动态具有调节作用,尤其群体LAI变化速率、最大LAI及其到达的时间、平均LAI及其与最大LAI的比率等重要特征参数对密度响应较为敏感,可作为对春玉米群体密度调控的参考指标。     

Application of the pumping coal gangue cemented filling materials in roadside

To take full advantage of gangue for roadside supporting in coal mines physical properties of coal gangue are tested. The collapsed slump uniaxial compression strength and initial setting time of gangue binder backfill material with different water-cement ratios and admixture contents are researched. Experimental studies show that the best ratio of water cement coarse aggregate fine aggregate and admixtures is 1:2:5.6:1.6:0.02 for site pumping of roadside packing support. The collapsed slump 28 d uniaxial compression strength and initial setting time of gangue binder backfill material are 210 mm 20.8 MPa 224 min respectively under such ratio. It could satisfy the requirement of site supporting and the initial setting time of binder backfill material under such ratio is about 50 min shorter in site than indoor.