To understand the potential role that the diameter of a burner plays in flame structure and flame instability, the influence of burner diameter on the turbulent premixed flame structure was investigated in two Bunsen-type burners. The nozzle inner diameters were 8 and 10 mm, Reynolds numbers were 2200, 3300, and 4400, equivalence ratios ranged from 0.8 to 1.2, and velocity fluctuations were varied by using two turbulence generation systems. The normalized flame edge length, local curvature of flame, and skewness of the flame curvatures were derived from Mie scatter images. Results showed that when the Reynolds number was small, the flames were smooth and the skewness of the flame curvatures was close to 0. When the Reynolds number was increasing to a turning point, the flames became wrinkled, and the skewness of the flame curvatures continued to decrease to negative. The turning point in the experiment with burner diameter of 10 mm was smaller than that in the other experiments. To measure the influence of burner diameter, a wavelet analysis was applied. An index was proposed to quantify the boundary conditions from the wavelet energy distribution. The index was observed to be negatively correlated with the skewness of the flame curvatures. In summary, the flame wrinkled easily with increasing burner diameter, and the wavelet energy distribution of inflow velocity may provide a way to judge the influence of the diameter.

Operational rules and control strategies of the chemically recuperated gas turbine (CRGT) in the marine propulsion are investigated in this paper. The Minimization of Gibbs free energy method is used to calculate the diesel-steam reforming reaction which products synthetic hydrogen rich fuels, and a universal model of the chemical regenerator which is easily applied to different application environments is created. The hydrogen production and hydrogen molar fraction are investigated to verify that the CRGT improve the combustion performances under low working conditions. Off-design calculations are performed to derive proper operational rules, and transient calculations are performed to investigate the best control strategies for the systems. The modelling approach of the chemical regenerator can be generally used in the chemically recuperated gas turbine. The elaborate operational rules can greatly improve the thermal efficiencies under every working condition. The system using synchronous control strategies have better regulation speed and operation stability than that using asynchronous control strategies.

Thermodynamic design methods and performance calculation models for chemical reformers that can be used to recuperate exhaust heat and to improve combustion quality are investigated in this paper. The basic structure of the chemical reformer is defined as series-wound reforming units that consist of heat exchangers and cracking reactors. The CH4-steam reforming reaction is used in the chemical reformers and a universal model of this reaction is built based on the minimization of Gibbs free energy method. Comparative analyzes between the results of the calculation and a plasma-catalyzed CH4-steam reforming reaction experiment verify that this universal model is applicable and has high precision. Algorithms for simulation of series-wound reforming units are constructed and the complexity of the chemical reformers is studied. A design principle that shows the influence of structural complexity on the quantity of recovered heat and the composites of the reformed fuel can be followed for different application scenarios of chemical reformers.

In ethanol/diesel dual-fuel engines, premixed ethanol/air atmosphere could affect the ignition delay of diesel spray as well as the following soot formation. In this paper, a reduced mechanism describing the chemistry of ethanol and n-heptane was composed and validated with various experimental data. Based on this mechanism, simulations were conducted to investigate the combustion characteristics of n-heptane spray under premixed ethanol/air atmosphere in a combustion vessel. The effects of equivalence ratio of premixed ethanol/air atmosphere, ambient temperature and charge cooling effect of ethanol vaporization were investigated. Under premixed ethanol/air atmosphere, the results showed that high temperature ignition first occurred in the regions with mixture near stoichiometric ratio, rather than regions with largest n-heptane content (i.e. highest fuel reactivity). This is mainly because the vaporization of direct injected n-heptane decreased the gas temperature and consequently restricted the low temperature reaction. While the equivalence ratio of premixed ethanol/air atmosphere was further increased, the mixture near stoichiometric ratio exhibited lower fuel reactivity, which consequently resulted in prolonged ignition delay. It was also found that premixed ethanol could inhibit the soot formation of n-heptane spray under low ambient temperatures while contributed to significantly increased soot emission under high ambient temperatures. Moreover, the simulated results showed that the cooling effect of ethanol vaporization also played an important role in soot reduction of dual-fuel combustion.

采用Visual C++编程计算了所设计的蒸汽发生系统热力参数,分析其变工况性能,获得调控规律.基于该蒸汽发生系统,计算了化学回热循环燃气轮机的设计点和变工况性能.随着供人蒸汽发生系统的能量增加,蒸汽产量逐渐升高并维持在一个最大值,该最大值由高压闪蒸的压力决定.以蒸汽产量为蒸汽系统的设计目标时,补给水流量的最优值是设计点的值.化学回热循环系统较原型机效率提高,NOx排放减少,环境热污染减小.

The chemically recuperated gas turbine (CRGT) is a promising engine on ship because of its high thermal efficiency and low pollutant emission. This paper is aimed at determining an applicable configuration of the CRGT for marine applications. Diesel is the selected fuel, and the minimization of Gibbs free energy method (MGFE) is applied to model the diesel-steam reforming reaction. A chemical regenerator (CR) is designed based on the reforming reaction, and a steam generator (SG) is set on the foundation of thermodynamics. Some feasible configurations of the CRGT are proposed based on a marine gas turbine with two spool shaft and a free power turbine and the best one is determined by performance calculation. The best configuration has a 44.51% thermal efficiency at rated 25MW output power of the prototype, and good stability in operation. Additionally, the selected configuration has lower combustion temperature at the same output power with the other configurations, and it can yield less NOX emissions. These works form the foundation of the CRGT being applied in the marine propulsion and provide a research thought for the CRGT in other applications.

Aiming at forming the foundation of the chemically recuperated gas turbine (CRGT) being ap?plied in the marine propulsion, the minimization of Gibbs free energy method was applied to calculate diesel-steam reforming and thermodynamic performance of the CRGT was evaluated based on this method. The minimiza?tion of Gibbs free energy method was used to calculate methane-steam reforming and the highest differences was 3.44%contrast to experiment,which proves the accuracy of this method. Then,the diesel-steam reforming was calculated by this method and the heat value of the reformed fuel was 38.9%higher, indicating that the CRGT has a higher thermal efficiency. And the outlet temperature of combustor in the CRGT based on some gas turbine was 1375.3K,167.5K lower than 1542.8K of the simple cycle,which leads to low NOx emission. It is also illus?trated that the energy of exhaust gas out of the reformer can produce enough steam for the CRGT.

In this paper, characteristics in all working conditions of some selected turbine are acquired based on the information of several given operating points and an improved ISO temperature is proposed to calculate expander power of some turbine. An object-oriented approach is used to code the turbine calculation program. Firstly, characteristics in the same rotational speeds with given variable operating points are calculated by Stodola-Flügel equation and PSO based neural networks are used to predict more characteristics. Then, the turbine thermodynamic process is divided into blending of gas and cooling air and gas expansion. The blending process is calculated by improved ISO temperature method which adopts PSO method to calculate the optimal value of recovery coefficient of gas pressure and efficiency coefficient of the cooling air enthalpy. Finally, the above calculation procedure of the turbine is coded by an object-oriented approach and it is approved to be of high accuracy. Such a calculation process proposed in this article meets the requirement of turbine performance calculation with cooling air.

A characteristic prediction method was proposed and variable specific heat calculation was applied to the performance analysis and programming of compressor based on object-oriented theory. Also, a method named particle swarm optimization (PSO) based on back propagation (BP) neural network was presented by combining the global optimization ability of the PSO with the local optimization ability of the BP neural network, and the prediction error and fitting error were analyzed. The fitting error is mostly within 0.5% while the highest prediction error is within 0.8%; and both the fitting accuracy and prediction accuracy could meet the requirements. Variable specific heat calculation method was applied to the compressor performance calculation, and object-oriented method was used to build the compressor performance computing program. Compared with several working condition points of the compressor, the output parameter errors are less than 1.12%. Therefore, the characteristic prediction method and performance mathematical model are suitable for compressor performance calculation, and the compressor calculation procedure is also suitable for gas turbine performance calculation.

This paper describes the design and performance analysis of a chemically recuperated gas turbine powering a ship. The system studied consisted of an efficient steam-generating system, a reforming regenerator, and a gas turbine. Mathematical models were built for the performance analyses. An efficient steam-generating system was designed and the effects of various parameters on the steam generation were studied. The calculations indicate that the steam-generating system can meet the steam requirements for reforming and fresh water needs of the ship. The diesel steam-reforming reaction was adopted for heat recuperation, and the reaction degrees were analyzed under different conditions. It was found that the reforming regenerator recovered heat from the waste gas to reform the fuel leading to improved combustion. The performance analysis shows that the chemically recuperated gas turbine has a higher thermal efficiency and consequently delivers more power. The steam reforming cycle has a low reaction degree and needs to be improved through additional research.

先进循环是燃气轮机发展的重要方向,1套通用先进循环工质热物性计算方法对先进循环研究具有重要意义.以工质最为复杂的化学回热循环为例,建立了1套通用的工质热物性计算方法,并论证了该方法也适用于其他先进循环.基于面向对象方法建立了1套计算系统并采用C++语言编制其计算程序,验证了空气和水蒸气的热物性计算精度,最大误差为0.00852％.采用该热物性计算方法计算了1个化学回热循环的热力过程;在给定的条件下其效率比简单循环效率提升32％,达到47.32％.结果表明:所提出的热物性计算方法计算准确,通用性强,为先进循环研究提供了基础.

Plasma is proposed as a prospective tool for chemical heat recovery process without restriction from reaction temperature. The author designed DBD catalytic reactors and carried out extensive experiments to investigate methane conversion and products yield and analyze the effect laws of steam to methane ratio, resident time and reaction temperature on methane steam reforming (MSR). Based on extensive experimental studies of steam reforming, a detailed reaction mechanism for the plasma-assisted MSR was developed and evaluated by comparison of experimentally derived and numerically predicted conversion and products yield. The comparisons showed the kinetic model well predicted methane conversion and products yield in different operating conditions. By employing the kinetic model and path flux analysis module the kinetic effects of low temperature non-equilibrium plasma assisted CH4 steam reforming on the methane conversion was studied without catalyst. The results showed that CH3 recombination was the limiting reaction for CO production; meantime O was the critical species for CO production. By adding Ni catalyst can reduce methyl recombination and promote hydroxyl into oxygen, which is beneficial to heat recovery. The proposed research ensures the effect laws and characters of MSR by plasma, and contribute to improve the objective products concentration and furthermore the energy efficiency.