井眼方向控制设计的新方法

为了简化井眼方向控制设计的数学公式推导和施工参数求解,采用矢量代数方法对空间圆弧模型进行了再研究,推导出装置角、井眼方向矢量、井眼高边矢量、圆弧内法向矢量之间的矢量关系式。将圆弧井段参数计算中原来用三角函数表示的复杂公式用简单的矢量公式重新进行描述,极大地简化了有关的公式推导过程和计算。使用新的矢量公式对井眼方向控制方案设计参数求解问题进行研究,求出了全部9种已知设计条件下的设计方案的解,并给出判断初始装置角正负符号的新的、简单的判据。使用实际数据对设计方法进行测试,结果完全正确。给出的圆弧模型参数矢量计算公式,具有较强的几何直观性,比其他使用三角函数的相关公式更加简单,不仅可以用于解决井眼方向控制问题的求解,而且在圆弧型井眼轨道设计与计算的其他问题中都有应用价值。     

最小曲率法的再认识及其应用

在使用最小曲率法推导有关公式的过程中,涉及了大量的三角函数变换,过程有时很复杂,极易出现错误。为了解决这个问题,分析了井眼轨迹切线与井斜角和方位角之间的数学关系,利用井眼方向矢量给出了最小曲率法的矢量形式。这种矢量形式深刻地揭示了圆弧井段弯曲角、井眼曲率、坐标增量、井斜角和方位角之间的关系的数学实质,具有形式简洁和几何直观性。使用矢量形式的最小曲率法对井眼轨迹内插、完钻井段设计等问题进行了研究。结果表明,有关公式的推导过程非常简单,完全避免了复杂的三角函数变换,而且最终得到了计算公式更加简单。同时,还用实际算例进行了验算,证实了本文新公式的正确性。本文提出的矢量形式的最小曲率法新公式可以应用于与圆弧井段有关的井眼轨迹设计和计算问题中。     

除氧器暂态计算公式及方法的探讨

该对除氧器暂态计算的公式进行了推导，在献1的基础上探讨并改进了除氧器暂态计算方法，使其使用更加方便，此方法已在工程设计中试用。     

增压器涡轮叶片模态特性研究

基于有限元法，对增压器涡轮吉进行模态特性研究，从理论上探讨了材料参数，离心惯性及工作温度对涡轮叶片模态特性的影响。根据Ｈａｍｉｌｔｏｎ原理，推导了考虑离心惯性力影响的涡轮叶片振动方程。给出了材料参数，工作温度对涡轮叶片模态特性影响的解析式。在涡轮转速不十分高时，引入等效弹性模量的概念，得出涡轮转速对叶片模态特性影响的近似公式。     

LPG发动机蒸发减压器的换热计算

本文分析了澳华液化石油气（LPG）有限公司生产的蒸发减压器的工作过程，对LPG的气化进行了公式推导，给出了LPG与循环水之间的关系，推导出了蒸发减压器换热面积的计算方法，为蒸发减压器的设计制造提供了理论依据。     

氢冷发电机气密性计算方法研究

氢冷发电机气密性试验结果采用由理想气体方程推导出的计算公式,在试验过程中必须严格执行相关标准要求,试验结果计算应考虑各项参数的变化,不宜随意使用简化公式,由此可得出更准确的试验结果.     

启喷压力与针阀落座冲击应力间关系和理论分析

本文作者详细地评述了针阀落座冲击应力的影响因素,以及目前用来计算座面冲击应力的公式对不同类型喷嘴的适用性。通过对启喷压力与针阀落座冲击应力之间关系的分析,根据应力波理论推导了新的针阀座面冲击应力的计算公式。该公式可适用于各种不同类型的喷嘴,从而为喷嘴的设计和选择合适的启喷压力提供了可靠的理论依据。     

一种随机性的推移质输沙率公式研究

基于颗粒受力平衡推导了推移质起动条件,根据近壁水流应力分布特性,提出了水流有效切应力区的概念,结合推移质在平衡输沙情况下的运动规律,得到了理论更为完善的随机性推移质输沙率公式,并对公式进行了起动条件敏感性分析,发现低水流强度下的输沙率计算对起动条件较为敏感,因而合适的推移质起动强度是控制输沙率计算精度的关键。利用经典推移质输沙率实测数据及野外实测资料对公式进行了检验,结果表明,该公式与实测数据吻合良好,验证了公式的合理性和适用性。     

空燃比的计算及测量误差分析

推导了由测量得到的燃烧产物中CO2、CO、O2、NO，和HC的体积分数计算燃料空气混合气空燃比的计算公式．推导的公式考虑了燃料中碳、氢、氧3种组成成分，可用于常见的各种燃料的混合比计算．推导的公式还考虑了空气中氩和水蒸气的含量，因而更适合精确计算混合比的场合．推导的公式还被用于分析空燃比精度的影响参数和点燃式发动机空燃比的计算，结果表明，公式的计算值与其它公式的计算值及仪器指示值的变化趋势是一致的，燃料组成的H／C比、O／C比及空气中水蒸气含量对空燃比的测量结果有较大影响．     

计算机代数在热动力系统建模与仿真中的应用

研究先进的数学工具-计算机代数系统在热力系统建模中的应用基础上，提出了用计算机代数系统辅助进行数值计算的建模方法。利用计算机代数和符号运算功能，可以替代常规数值建模中公式推导，导数和积分计算繁杂，耗时而且容易出错的手工过程，以Mathematica计算机代数系统作为软件平台，以某气化炉对对象进行了化学反应速率推导的建模示范。示范结果表明：新的建模方法有以下优点；公式推导和后期修改工作量大大减少，易于实现高效、快速自动建模；避免了数值推导的误差，模型精度高，收敛性好；可以直接生成仿真程序代码，程序流程简洁，可读性好，随着热动力系统的日益大型化和复杂化，新方法有广阔的应用前景，值得继续深入研究。图3表1参11     

Thermomechanical Interactions in a Generalized Thermo-Microstretch Elastic Half Space

Interactions caused by thermal and mechanical sources in a generalized thermo-microstretch elastic medium are studied by the use of Laplace-Fourier transform techniques. The formulation is applied to the coupled theory as well as to two generalizations, the Lord-Shulman and the Green-Lindsay theories. The integral transforms are inverted using a numerical technique to obtain the solutions field in the physical domain. Stretch effects lead to the existence of a new wave that is called longitudinal microstretch wave. The results of micropolar generalized thermoelasticity and generalized thermoelasticity are deduced as special cases from the present formulation.     

Nonlinear effects of stretch on the flame front propagation

In all experimental configurations, the flames are affected by stretch (curvature and/or strain rate). To obtain the unstretched flame speed, independent of the experimental configuration, the measured flame speed needs to be corrected. Usually, a linear relationship linking the flame speed to stretch is used. However, this linear relation is the result of several assumptions, which may be incorrected. The present study aims at evaluating the error in the laminar burning speed evaluation induced by using the traditional linear methodology. Experiments were performed in a closed vessel at atmospheric pressure for two different mixtures: methane/air and iso-octane/air. The initial temperatures were respectively 300 K and 400 K for methane and iso-octane. Both methodologies (linear and nonlinear) are applied and results in terms of laminar speed and burned gas Markstein length are compared. Methane and iso-octane were chosen because they present opposite evolutions in their Markstein length when the equivalence ratio is increased.The error induced by the linear methodology is evaluated, taking the nonlinear methodology as the reference. It is observed that the use of the linear methodology starts to induce substantial errors after an equivalence ratio of 1.1 for methane/air mixtures and before an equivalence ratio of 1 for iso-octane/air mixtures. One solution to increase the accuracy of the linear methodology for these critical cases consists in reducing the number of points used in the linear methodology by increasing the initial flame radius used.     

Laminar burning velocities of rich near-limiting flames of hydrogen

In the present work, near-limiting hydrogen flames were investigated both experimentally and numerically. Very rich hydrogen + air flames were studied in a constant volume bomb equipped with a pressure sensor and a Schlieren system for optical registration of the flame front movement. The mixtures contained 70% and 75% of hydrogen, the rest being air. The measurements were conducted at pressures from 1 to 4 atm for 70% H₂ + air mixture and from 0.7 to 1.4 atm for 75% H₂ + air mixture. Two methods for determination of the laminar burning velocity were used: from the temporal evolution of the flame front movement and from the pressure records at nearly constant pressure. These methods were compared and discussed in terms of accuracy and implicit assumptions behind them. Markstein lengths were also extracted and compared with the literature by using different extrapolation models. An important role of the critical radius for extraction of the burning velocity and Markstein length is demonstrated. New experimental data are compared with three models for hydrogen combustion to elucidate the need for their further development.     

Premixed edge flame in a counterflow field with a stretch rate gradient

An edge flame was established in a counterflow field with a stretch rate gradient using twin rectangular burners which were misaligned by a few degrees. The stretch rate gradient was quantitatively defined as a function of the angle between the two burners and the distance from the edge of the burner, and thus the effect of stretch rate gradient on the behavior of the edge flame was investigated. The local chemical reaction rate at the edge of a CH₄/air flame was stronger than that at other parts of the flame. On the other hand, the reaction rate at the edge of a C₃H₈/air flame was weaker than that of other parts of the flame. The curvature of the flame edge of the CH₄/air flame was much larger than that of the C₃H₈/air flame. These results are thought to be due to the effect of the Lewis number. The ratios of the local stretch rate at the flame edge to the extinction stretch rate for planar twin flames with the same composition as the edge flame were 0.5 to 0.7 for the CH₄/air flame and 0.6 to 0.8 for the C₃H₈/air flame. These values were midway between those in the numerical simulation by Daou and Linan and those in the experiment by Liu and Ronney. Moreover, it was shown that an increase in the stretch rate gradient resulted in a lower local stretch rate at the flame edge. Behavior of the edge flames did not depend on the Lewis number of the mixture.     

Generation of PDFS for flame curvature and for flame stretch rate in premixed turbulent combustion

Experimentally derived pdfs of turbulent, premixed, flame curvatures from a variety of sources, for a wide range of conditions are surveyed and a suitable expression sought to generalize these. This proves to be one based on the Damköhler number, Da. This is tantamount to normalizing the curvature by multiplying it by the Taylor scale of turbulence. It enables the distribution of flame curvature when normalized by the laminar flame thickness, to be expressed in terms of the Karlovitz stretch factor, K, and the turbulent Reynolds number, R_l. The value of the pdf at zero curvature is linearly related to Da^1/2.The pdf expressions of Yeung et al. [3] obtained from numerical simulations are used for the strain rate distribution and, on the assumption that these and that for flame curvature are statistically independent, values of flame stretch rate pdfs are generated numerically. It is necessary to define an appropriate surface to define the burning velocity, flame stretch rate, and appropriate Markstein numbers. Two surfaces are considered and employed in the computations, one located at the start of the preheat zone, the other at the start of the reaction zone. The latter seems more rational and gives the better generalisation of the pdfs of flame stretch rate.An assumed linearity of laminar burning velocity with flame stretch rate, extending over both positive and negative stretch rates, enables flame stretch rate pdfs to be generated. It is concluded that negative values of burning velocity are unlikely and that burning velocities should tend to zero rather than attain negative values. This modifies the derivation of flame stretch rate pdfs. These depend on the Markstein number, Karlovitz stretch factor and turbulent Reynolds number. Computations suggest that, for values of K above 0.1 and of R_l above 100, the pdf of stretch rate is similar to that of strain rate. At very low values of K and negative values of Markstein number, pronounced flamelet instability might be anticipated.     

Structure, aerodynamics, and geometry of premixed flamelets

Recent advances in the understanding of the structure, dynamics, and geometry of laminar premixed flames under the influence of stretch, as manifested by aerodynamic straining, flame curvature, and flame/flow unsteadiness, are reviewed and presented in a tutorial manner. The discussion first treats the flame as a structureless surface which propagates into the fresh mixture with a constant velocity—the laminar flame speed, and the phenomena of cusp formation and volumetric burning rate augmentation through flame wrinkling are demonstrated. It is then shown that by considering the effects of stretch on the flame structure, and by allowing for mixture nonequidiffusion, the flame responses, especially the flame speed, can be quantitatively as well as qualitatively modified. By using the stretch-affected flame speed, we then describe the phenomena of cusp broadening, of tip opening of the Bunsen flame, and of the intrinsic hydrodynamic, body-force and diffusional—thermal modes of flamefront cellular instabilities. Additional topics covered include forced and intrinsic oscillatory flame dynamics, and quantitative extraction of the global flame parameters represented by the activation energy, the Markstein length, and the Lewis number.     

A theoretical study on Bunsen spray flames

The structure of Bunsen flame tip under the influence of dilute, monodisperse inert (water) or fuel (methanol) sprays is theoretically studied using large activation energy asymptotics. A completely prevaporized mode is identified, in which no liquid droplets exist downstream of the flame. Parameters for open and closed flame tips in the analysis consist of the amount of liquid loading indicating the internal heat loss for the water spray or the internal heat loss and heat gain for the rich and lean methanol-sprays, respectively, and the (negative) stretch coupled with Lewis number (Le) which strengthens the burning intensity of the Le>1 flame but weakens that of the Le<1 flame, respectively. For rich methane-air flames (Le>1) with water sprays (or lean methanol-spray flames with Le>1), closed-tip solutions are obtained. The burning intensity of the flame tip is enhanced with either decreasing liquid-water loading (or increasing liquid-fuel loading) or increasing stretch. Conversely, the negative stretch weakens the burning intensity of a lean methane-air flame (Le<1) with water sprays (or a rich methanol-spray flame with Le<1) and eventually leads to tip opening, i.e., flame extinction. The burning intensity is further reduced with either increasing liquid-water (or liquid-fuel) loading or increasing stretch. Moreover, the open flame tip is further widened when either the liquid-water loading (or liquid-fuel loading) or the upstream flow velocity is increased. It is noteworthy that the gradual increase of liquid-fuel loading strengthens the burning intensity of the lean methanol-spray flame (Le>1) and thus leads to the transition of flame configurations from conventional Bunsen cone through planar flame to inverted flame cone (a convex flame shape with respect to the upstream reactants). The critical value of liquid-fuel loading, at which there exists a planar flame rather than a Bunsen cone flame, is increased with either increasing upstream flow velocity or decreasing equivalence ratio.     

天然气-氢气-空气混合气的层流燃烧速度测定

在定容燃烧弹内研究了常温常压下天然气-氢气-空气混合气的火焰传播规律，得到了不同掺氢比例（氢气在天然气中的体积掺混比例为0％～100％）和燃空当量比（0．6～1．4）下混合气的层流燃烧速率和马克斯坦长度，通过对马克斯坦长度的测量，分析了拉伸对火焰传播的影响。结果表明，随着天然气中掺氢比例的增加，混合气的燃烧速率呈指数规律增加，马克斯坦长度值减小，火焰的稳定性下降。各掺氢比例下，随当量比的增加，马克斯坦长度值增加，火焰的稳定性增强。通过对试验结果的数据拟合，得到了计算天然气-氢气-空气混合气层流燃烧速率的关系式。