切片厚度对苦瓜片热风干燥特性及相关品质的影响研究

以新鲜苦瓜为原料,研究切片厚度分别为2,4,6 mm的苦瓜片在65℃热风干燥后,其热风干燥特性及理化品质的变化。结果表明,切片厚度对苦瓜片干燥特性和理化品质具有重要影响。在65℃热风干燥下,切片厚度从6 mm减至2 mm,干基含水量和水分比下降增快,干燥速率增快,有效扩散速率减小。同时,随着切片厚度减小,干制苦瓜片复水比越大,收缩比越小,干制品色泽越好。因此,结合苦瓜片热风干燥特性及品质变化,切片厚度为4 mm是进行苦瓜片热风干燥的适宜厚度。     

不同储藏条件下糙米中过氧化氢酶活动度的变化规律

在不同储藏条件下,对糙米中过氧化氢酶活性变化规律进行研究。采用储藏条件为:氧气浓度分别是2%、5%、21%,温度分别为15℃、20℃、30℃,水分分别为13.5%、14.5%、15.5%。以此来进行糙米模拟储藏实验。首先采用单因素实验研究方法,研究了氧气浓度、储藏温度、糙米水分对糙米过氧化氢酶活性的影响规律。研究表明:在3种不同氧气浓度的气调方式中,2%和5%的氧气浓度可使水分在13.5%～14.5%之间、温度范围为15℃～20℃的糙米在5个月的储藏期内过氧化氢酶活性下降控制在25%以内,而在21%氧气浓度的自然储藏条件下,其过氧化氢酶活性下降超过了35%。另外通过比较21%氧气含量、水分13.5%不同温度条件下糙米的过氧化氢酶的活性变化情况,可以看出高温下(30℃)的糙米其过氧化氢酶活性比15℃和20℃的糙米变化要快。在150d的储藏期内下降了37%。且后者在60d出现一个转折点,过氧化氢酶活性变化速率开始明显减小。其中高于15.5%的高水分糙米不宜储藏,实验验证了低氧可以延长高水分糙米的储藏期。通过单因素实验和多因素综合实验,并使用Design一Expert软件进行多因素分析,可以得出各因素之间具有交互作用,其中温度和氧气浓度和水分的交互作用对糙米中过氧化氢酶活性的影响显著。水分和温度越低,糙米品质劣变速度越慢。     

基于OH-PLIF技术的合成气燃烧速度

为了解合成气燃烧特性,采用高精度光学测量技术PLIF,研究了不同生物质气化合成气在不同当量比下的燃烧火焰结构、OH基浓度以及火焰传播速度。采用CHEMKIN软件模拟计算了相同工况下合成气火焰传播速度,对引起温度变化和OH基浓度变化的原因进行了化学动力学分析。研究结果表明,合成气中CO含量的增加会使火焰整体结构变小,但对内焰影响程度不大,而H₂含量的增加会增大火焰的传播速度。合成气燃烧过程中主要影响OH基生成的是R36：CO+OH=CO₂+H、R43：H+O₂+M=HO₂+M和R45：H+HO₂=2OH这3个基元反应。     

低温胁迫对棉花幼苗生长的影响

为了探究低温胁迫对棉花幼苗生长特性的影响,本试验以新陆中85号为材料,采用砂培方式,将棉花幼苗放于不同低温及同一温度不同时间下进行胁迫处理。结果表明,温度越低、持续时间越长对棉花幼苗的生长影响越大;同一温度下,随着胁迫时间的增加,棉花幼苗叶面积减小,干物重下降,细胞膜透性增加。在相同的处理时间下,随着处理温度的降低,细胞膜透性降低,其他指标均变小。由此可见,苗期低温对棉花幼苗生长能力影响很大。     

发动机燃烧室内壁材料热环境的气动热试验模拟技术研究

利用超声速矩形湍流导管和等离子电弧加热器模拟了发动机燃烧室内流和高超声速飞行器外壁面外流热环境,进行了平板表面冷壁热流测量和燃烧室内壁材料考核试验。结果表明:由于辐射换热的影响,在选取的两个典型来流条件下,发动机燃烧室内流热环境下的冷壁热流比外流热环境下的高出21%和40%,但是冷壁热流的增量基本相当,约为0.70~0.80MW/m²。随着冷壁热流的增加,辐射换热产生的热流增量的影响力会逐渐减小。材料考核时,相同配方的C/SiC复合材料在内流热环境下的表面温度高出约400℃,背面温度高出约90℃,这种差异对于发动机燃烧室内壁面材料考核至关重要,必须在材料考核试验中加以考虑。      

水稻种子加温干燥的研究

(一)水稻种子在加温干燥过程中的失水速率随温度和原始水分上升而增加。当温度达60℃以上时,失水速率显著增快。总的看来,温度每上升10℃,失水速率约增加2.0%/小时。(二)水稻种子对高温的忍受能力和它的原始水分有关,原始水分越高,越不耐高温,水稻种子的安全干燥温度为50℃。若品种较耐高温或原始水分较低的情况下,可考虑用60℃。(三)水稻种子在60℃以下的温度进行干燥,发芽力可以维持与对照相同的水平。在自然条件下贮藏大多数品种的耐藏性可以保持与对照相同水平或略有提高。(四)水稻种子加温干燥对淀粉酶、过氧化氢酶和脱氢酶活性产生促进或抑制作用,随温度和水分而转移。淀粉酶和过氧化氢酶活性变化和发芽率基本一致,其相关系数均达极显著水平。(五)水稻种子在60℃以下进行干燥,淀粉酶和过氧化氢酶活性比对照有所提高或保持相同水平。(六)数据的统计分析结果表明:凡经干燥处理后淀粉酶或过氧化氢酶活性比对照有明显下降时,表明种子已经遭受高温灼伤的影响。在贮藏过程中或迟或早会从发芽率上显示出来。     

氮素营养对美丽异木棉等4个树种幼苗生长及光合特性的影响

为了探索不同氮素供应水平对美丽异木棉等4个树种的苗期生长以及光合生理特性的影响,采用指数施肥法对4个树种幼苗进行施肥试验。结果表明：（1）不同氮素处理间幼苗生长差异显著,各生长指标受氮素影响较大的是生物量和苗高,地径的变化幅度最小;（2）不同氮素处理间幼苗光合生理指标有显著差异,随着氮素施用量的增加,美丽异木棉的净光合速率呈现出先增加后减小的趋势,气孔导度和胞间CO2浓度呈现出“减小-增加-减小”的趋势,蒸腾速率呈现2次先增加后减小的趋势;杜鹃红山茶、红花荷和火焰木的净光合速率、气孔导度及蒸腾速率呈现出2次先增加后减小的趋势。     

不同纬度和播期对苏麦6号淀粉糊化特性的影响

以苏麦6号为材料,在江苏3个不同纬度点(31.3°N-33.4°N),设置了7个播期,利用快速粘度分析仪(RVA)分析了纬度和播期对籽粒淀粉糊化特性的影响.结果表明:纬度和播期对小麦淀粉糊化特性均有显著或极显著的影响,且纬度的影响比播期的影响大;随纬度的升高,峰值粘度和稀懈值均呈增加的趋势,其他指标值变化不一;随播期的推迟,峰值粘度、低谷粘度、稀懈值、最终粘度和回复值均呈显著或极显著的增加趋势;不同纬度的小麦RVA特征值在播期间的变化强度不一.     

秋季大棚黄瓜主要光合作用特性研究

研究了秋季大棚黄瓜的部分光合作用特性。不同基因型黄瓜的光合作用速率不同，一般杂交品种的净光合速率比常规品种高，适合秋季大棚栽培的黄瓜品种净光合速率比不适合的高。不同叶位间净光合速率也明显不同，幼叶和老叶的光合能力较低，健壮叶片净光合速率最高。净光合速率日变化表现为双峰曲线，有明显的“午休”现象。中午空气湿度低，叶表蒸气压亏缺急剧升高造成气孔导度下降是造成光合“午休”的主要原因。温度明显影响光合作用,黄瓜的最适温度为21～33℃.     

不同播种方式对耕层土壤温度及冬小麦产量的影响

研究了不同播种方式对耕层土壤温度及小麦产量的影响,结果表明,无论春季还是冬季地表温度变化均是沟播升温快、降温也快,影响根系生长发育;冬季地表温度变化影响以下各层,越接近地表,温度变幅越大,越远离地表,越趋于一致;沟播产量大于平播,增产约8.4%。     

Numerical simulation of hydrogen air combustion in meso scale IC engine

The burning rate of hydrogen air pre mixture on meso scale is mainly determined by its chemical reaction rate. So a Laminar Finite Rate Model, the gas phase reaction mechanism for the combustion of hydrogen air mixture which consists of 19 reversible elementary reactions and the dynamic mesh method are adopted to simulate the combustion of hydrogen air mixture in a meso scale IC engine which operates a quasi gas power cycle under ultrahigh combustion load. The combustion of hydrogen air mixture on meso scale in the micro combustion chamber with moving boundary can be stable. The complete thermodynamic process of heat addition, internal energy increasing, and a boundary work output producing during expansion can be perfectly achieved in the closed combustion system of the meso scaled IC engine igniting the hydrogen air mixture by wire surface of high temperature. However, running parameters such as cycle period, initial pressure and fuel/air ratio have complex effects on the hydrogen air combustion of micro closed container with moving boundary.     

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.     

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.     

Key Techniques for Design and Manufacture of Micro Gas Turbine Engine

The characteristics of flow and combustion in micro gas turbine engine with the low Reynolds number and the high Mach number, the high Couette number and the low Biot number, as well as the ultra high duty ratio of combustion in very small space are analyzed, which are remarkably distinguished from those on macro scale. At the meantime, the limitation of traditional dynamic lubrication theory at ultra high speed on micro scale is presented, and the possibility of making the gas bearing to be able to work at ultra high speed by utilizing boundary slip is investigated. Due to the applied prospect of silicon carbide in the field of MEMS especially under high temperature and high strength conditions, the technical process of combining silicon etching with reactive sintering and grinding machining of silicon carbide is put forward so that the miniature machining of silicon carbide for micro gas turbine engine becomes possible.     

Analysis of the characteristic on HCCI autoignition and combustion process of diisobutylene

The homogeneous charge compression ignition (HCCI) characteristics of diisobutylene are studied numerically. Numerical results are in accord with the corresponding experimental data. The influence of some key parameters such as initial pressure, equivalence ratio and constituent on autoignition characteristics is discussed and combustion characteristics of diisobutylene in HCCI engine are analyzed. The results indicate that the ignition delay decreases with the increase of pressure and equivalence ratio. The maximum temperature increases with the rise of equivalence ratio, but it does not change with the variation of initial pressure. The 1 pentene isomer ignites significantly faster than the 2 pentene isomer and the ignition delay for the blend directly depends on the proportions of each isomer. It can be found that diisobutylene shows the single stage autoignition. The maximum heat production rate of the 2 pentene is lower than that of 1 pentene, but the 2 pentene still provides good power performance.     

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.     

Experimental Study on Enhancing Dynamic Performance of NGV Engine by Using Oxygen-rich Air

NGV engine adopts the fuel supply method of premixing natural gas and air in the premixing chamber out of cylinder, which results in the engine dynamic performances decline. It is an obstacle to popularizing and applying NGV. Using air rich in oxygen to support combustion can decrease ignition point of the fuel, enhance combustion efficiency and make much more heat available. The dynamic perfonnances and fuel consumption rate of a NGV engine with different oxygen concentration are researched in detail. The results show that the increase of oxygen concentration has remarkable influence on the dynamic performances of NGV engine. Power and Torque performances increase and fuel consumption rate decreases when oxygen concentration of premixed gas increases. The results of theory analysis and experiment research indicate that combustion-supporting using oxygen-rich air can enhance the dynamic performances of NGV engine.     

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.     

不同自燃性煤氧化阶段的表征差异

对3种不同自燃倾向性煤样进行低温氧化实验,利用CO体积分数与煤体温度间变化的计算模型,求解出活化能和煤氧化过程发生转变的特征温度,同时结合热重-差示扫描量热（TG-DSC,theremogravimetric analysis-differential scanning calorimetry）实验结果,分析了不同自燃性煤氧化特性和活化能的低温表征规律。结果表明：1）低温氧化阶段,CO生成量、耗氧量和耗氧速率随着煤自燃倾向性增强而增大;不同煤样在实验过程中出现同样的CO生成量和耗氧速率急剧上升的温度拐点,且煤的自燃性越强,该拐点温度越低,同时CO体积分数的变化具有明显的阶段性。2）不同自燃性煤氧化阶段活化能变化规律存在显著差异,当各煤样的温度到达活性温度时,活化能快速减少,且活化能变化点对应于煤氧化过程发生转变的特征温度点。3）根据煤特征温度和活化能的变化规律,把煤低温氧化进程分为4个阶段,分别为表面氧化、氧化自热、加速氧化和深度氧化。     

Experiments of the EFI engine fueled with blends of high proportion aquiferous ethanol and gasoline

Engine power performance of fuel economy and emission characteristics with a JL368Q engine run on ethanol/ gasoline blends was experimentally investigated. The results show that with the same structure and parameter of the engine, at the low speed, the power output or torque of blended fuels are almost similar to that of 93 # gasoline. But with the speed increasing, the E15W and E50W power outputs are lower than that of 93# gasoline while E30W remains the same. The brake specific fuel consumption of E15W is lower than that of gasoline about 0.35%. With the increase of ethanol volume fraction in the blended fuel, the specific fuel consumption increases gradually. When fueled with ethanol/ gasoline blends, the engine NOx emission increases and CO emission decreases. E30W gives the lowest CO emission in this test. With the increase of ethanol volume fraction, HC can be improved gradually.