Combustion model of tetra-ol glycidyl azide polymer

Tetra-ol glycidyl azide polymer (GAP) is one of the best candidates for the solid fuel of gas hybrid rocket system because of self-combustibility, better mechanical property and high heat of formation, and comprehensive understanding of combustion phenomena is indispensable for such an application. Combustion model of GAP, which is one-dimensional three-phase mode combustion model, was developed by Beckstead et al. and they applied it to tri-ol GAP successfully. We have applied this model to tetra-ol GAP as an initial attempt, and numerical simulation showed that maximum temperatures in the gas phase exceeded those of experimental results significantly, and calculated burning rates were much higher than strand burner data, thus, modification of the model taking account of combustion incompleteness was found to be necessary. Combustion residues of GAP were investigated, and those were found to be composed of soot (black color), and high viscosity residue (HVR), and yellow powder which was only observed at high pressures. These residues were analyzed by means of SEM and FTIR, and mass balance was also measured. Modifications of combustion model were made taking the residue analysis results into account as Blow Off Mechanism. Simulated final temperature in the gas phase and burning rate are lowered effectively and coincide well with experimental data adjusting kinetic parameters.     

Performance enhancement of a pulse detonation rocket engine

Utilizing liquid kerosene as the fuel, oxygen as oxidizer and nitrogen as purge gas, a series of multi-cycle detonation experiments was conducted to improve the performance of pulse detonation rocket engine (PDRE). In order to improve the performance of the engine, it is crucial to develop an effective DDT enhancement device with less flow loss and higher survival in hostile detonation tube; therefore, three spiraling internal grooves were tested. The three spiraling internal grooves were semicircle, square and inversed-triangle grooves, respectively. The results showed that the spiraling internal groove can effectively enhance DDT and prolong the operation time of PDRE. The effect of groove shape on thrust enhancement of PDRE and the optimum length of spiraling groove were then investigated. To improve the detonability of liquid kerosene and prolong the durability of PDRE, experiments on the kerosene preheating based on active cooling were conducted. The results demonstrated that with the aid of fuel preheating, the detonation initiation time for liquid kerosene was noticeably reduced and a fully-developed detonation wave was achieved in the position away from igniter 4.67 times the diameter of the detonation tube. By adding the additive to liquid kerosene, the detonation initiation time from 0.75 ms decreased to 0.34 ms and the detonability of fuel was dramatically improved. Finally, experiments were conducted to investigate the effects of the operating frequency on the detonation parameters, the fill fraction and PDRE performance. The results indicated that detonation pressure and temperature vary with the operating frequency of PDRE, and the fill fraction has a significant influence on the specific impulse of PDRE. With the strategy of partial filling in detonation tube, the specific impulse can be remarkably enhanced.     

A DYNAMIC MODEL FOR ROCKET LAUNCHER WITH COUPLED RIGID AND FLEXIBLW MOTION

The dynamics of a coupled rigid-flexible rocket launcher is reported. The coupled rigid-flexible rocket launcher is divided into two subsystems, one is a system of rigid bodies,the other a flexible launch tube which can undergo large overall motions spatially. First, the mathematical models for these two subsystems were established respectively. Then the dynamic model for the whole system was obtained by considering the coupling effect between these two subsystems. The approach, which divides a complex system into several simple subsystems first and then obtains the dynamic model for the whole system via combining the existing dynamic models for simple subsystems, can make the modeling procedure efficient and convenient.     

Analysis of deformation of nozzleless rocket propellent

Based on the Total Lagrangian approach and the integral constitutive relation, the viscoelastic large deformation incremental variational equation is derived, and the finite element program of axisymmetric problems is written. By using this program the bore change of propellent of nozzleless rocket under the action of both the internal pressure and burning is dealt with in detail.     

Procedure for retrieval of atmospheric aerosol backscatter coefficient profiles from results of multi-wavelength lidar sounding

A measurement procedure is proposed to retrieve the profiles of atmospheric aerosol backscatter coefficients (β_a) from the results of multi-wavelength sounding of the atmosphere by a laser location system based on a Nd: YAG-laser. The procedure uses a regression dependence between spectral values of β_a (background aerosol model) and involves the determination of coefficients which characterize the relative spectral behavior of aerosol extinction. The stability of the procedure to spatial variations of the above coefficients, a deviation of β_a from the dependence used, and calibration and measurement errors is examined. This procedure is compared with the widely used Fernald method by means of a numeric experiment. This procedure is demonstrated to be effective for retrieving vertical profiles of β _a in the troposphere, especially in the short-wavelength region. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 347–353, May–June, 2008.     

Measurement Data-Based Link-Level and System-Level Simulations for Single Carrier SC/MMSE MIMO Turbo Equalization Technique

Current advances in multi-dimensional channel sounding techniques make it possible to evaluate performances of signal processing algorithms in realistic conditions. By using channel impulse response measurement data collected in the real fields, link-level performances of signal transmission techniques in the fields such as bit error rate (BER) and frame error rate (FER) performances can be evaluated. This technique is called link-level simulation. Through statistical analysis of link-level simulation results, system-level performances of the techniques such as geographical distribution of BER and FER in the area of interest can also be evaluated. This technique is called system-level simulation. This paper focuses on link- and system-level performances of a multiple-input multiple-output (MIMO) Turbo Equalizer in real fields. Methodologies for the link- and system-level simulations using field measurement data are first presented. Results of link- and system-level simulations using two-dimensional channel sounding field measurement data collected in Tokyo are then presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

瞬时气压记忆型水箭的制作

利用塑料饮料瓶,胶塞,自行车气嘴及一次性注射器等材料制作一个装置,实现了水箭发射瞬时的内气压记忆,为安全发射和定量研究变质量问题提供一简便的实验演示。     

基于自旋回波探测的地面磁共振T2谱正反演策略

作为新兴地球物理方法之一,地面磁共振技术具有直接探测优势.但由于其发展时间较短,相关建模及反演方法介绍较少,传统的自由感应衰减探测方法不仅精度有限,且适应性较差.近年来,应用自旋回波信号直接探测横向弛豫时间是地面磁共振领域的研究热点.本文推导了其灵敏度核函数及正演公式,引入线性空间反演方案,即通过奇异值分解将含噪自旋回波信号由时间域变换至空间域.为避免矩阵病态问题,采用奇异值滤波法抑制分解病态程度,并联合同时迭代重建技术进一步提升空间域矩阵求解精度.结合非线性拟合对空间域矩阵参数进行提取,实现含水层对应含水量、横向弛豫时间的有效估计.通过模拟野外实验并进行数据解释,证实了该方案能够有效降低浅层含水量至1.5%,横向弛豫时间估测误差至0.02 s.本文的研究成果,将为地面横向弛豫时间探测及相关理论发展及方法在水文地质调查方面的推广应用提供有力支撑.