Fluid-Dynamics Analysis and Structural Optimization of a 300 kW MicroGas Turbine Recuperator

Computational Fluid Dynamics(CFD)is used here to reduce pressure loss and improve heat exchange efficiency in the recuperator associated with a gas turbine.First,numerical simulations of the high-temperature and lowtemperature channels are performed and,the calculated results are compared with experimental data(to verify the reliability of the numerical method).Second,the flow field structure of the low-temperature side channel is critically analyzed,leading to the conclusion that the flow velocity distribution in the low-temperature side channel is uneven,and its resistance is significantly higher than that in the high-temperature side.Therefore,five alternate structural schemes are proposed for the optimization of the low-temperature side.In particular,to reduce the flow velocity in the upper channel,the rib length of each channel at the inlet of the low-temperature side region is adjusted.The performances of the 5 schemes are compared,leading to the identification of the configuration able to guarantee a uniform flow rate and minimize the pressure drop.Finally,the heat transfer performance of the optimized recuperator structure is evaluated,and it is shown that the effectiveness of the recuperator is increased by 1.5%.

Research on Modeling and Control of a 100 kW Micro Bio-Gas Turbine

In order to know about the influences of disturbance on the operating performance, the present work developed the overall dynamic simulation model of the micro gas turbine and investigated the control system under the disturbances of environmental temperature and unit load. The response processes of main parameters have been obtained. It found that the compressor pressure ratio and the fuel flow rate increase in the case of natural gas being replaced by pine gas. When the system reaches a new steady state, the main parameters change to different values. The output power decreases with the declining of the air mass flow when the ambient temperature rises, the biomass gas mass flow rate increases under the regulation of the control system to maintain the output power and rotating speed in which the thermal efficiency reduces by 1.40%. The thermal efficiency enhances with the increase of output load. The control system can quickly and effectively act to maintain the key parameters at desired value.

Experimental Tests on a Pre-Heated Combustion Chamber for Ultra Micro Gas Turbine Device: Air/Fuel Ratio Evaluation

Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.

Performance analysis of cogeneration systems based on micro gas turbine(MGT),organic Rankine cycle and ejector refrigeration cycle

In this paper,the operation perfonnance of three novel kinds of cogeneration systems under design and off-design condition was investigated.The systems are MGT(micro gas turbine)+ORC(organic Rankine cycle)for electricity demand,MGT+ERC(ejector refrigeration cycle)for electricity and cooling demand,and MGT+ORC+ERC for electricity and cooling demand.The effect of 5 different working fluids on cogeneration systems was studied.The results show that under the design condition,when using R600 in the bottoming cycle,the MGT+ORC system has the lowest total output of 117.1 kW with a thermal efficiency of 0.334,and the MGT+ERC system has the largest total output of 142.6 kW with a thermal efficiency of 0.408.For the MGT+ORC+ERC system,the total output is between the other two systems,which is 129.3 kW with a thermal efficiency of 0.370.For the effect of different working fluids,R123 is the most suitable working fluid for MGT+ORC with the maximum electricity output power and R600 is the most suitable working fluid for MGT+ERC with the maximum cooling capacity,while both R600 and R123 can make MGT+ORC+ERC achieve a good comprehensive performance of refrigeration and electricity.The thermal efficiency of three cogeneration systems can be effectively improved under oredesign condition because the bottoming cycle can compensate for the power decrease of MGT.The results obtained in this paper can provide a reference for the design and operation of the cogeneration system for distributed energy systems(DES).

SOFC/MGT混合发电系统变工况控制模式及性能分析

以220kW的SOFC/MGT混合发电系统为研究对象,建立了相应的数学模型,分析了不同控制模式对混合发电系统变工况性能的影响.结果表明:对于220kW的SOFC/MGT混合发电系统,在单独SOFC燃料控制模式(Case 1)下,系统的稳定负荷必须大于70%;在变转速控制模式(Case 2)下,系统的稳定负荷必须大于77%;而在定转速恒定电池温度的控制模式(Case3)下,系统最低负荷可以低到59%.在相同负荷条件下,Case 2对应的系统效率最高,Case 1对应的系统效率最低.为保证混合发电系统的高效率,并扩大混合发电系统的运行范围,提出了一种新的控制模式,可以使得混合发电系统最低负荷达到45%,而系统效率始终保持在56.4%以上.

潜用双模式SOFC-MGT联合发电系统的设计与仿真

[目的]固体氧化物燃料电池—微型燃气轮机(SOFC-MGT)联合发电系统有利于提高常规动力潜艇的续航力和隐蔽性,为分析该系统在不同运行模式下的性能特性,[方法]利用Matlab/Simulink软件对燃料电池AIP动力装置加以改进,并与微型燃气轮机(MGT)组成顶层循环联合发电系统。根据潜艇的航行状态,提出动力装置的双工作模式。建立SOFC-MGT联合发电系统和尾气处理系统的仿真模型,分析其在设计点工况下的性能指标,以及电流、水碳比、甲烷(CH_4)流量、空气组分等因素对系统性能的影响。[结果]仿真结果验证了模型的有效性和可行性,2种工作模式下系统的发电效率分别为59.48%和61.61%,最大功率分别为217 kW和223 kW,其中模式2状态下的系统净功率更高。该联合发电系统在潜艇不同工况下均可保持稳定的输出功率和较高的发电效率,其性能明显优于其他AIP装置。[结论]研究成果可为SOFC-MGT联合发电系统在常规动力潜艇上的应用提供理论支撑。

MCFC/MGT联合发电系统的exergy分析

该文基于exergy分析的理论,在IPSEpro仿真环境下建立了顶层熔融碳酸盐燃料电池/微型燃气轮机联合发电系统稳态性能仿真模型。利用该模型对顶层系统在额定工况和变工况下的稳态性能进行了仿真研究。仿真结果表明,顶层熔融碳酸盐燃料电池/微型燃气轮机联合发电系统具有较高的效率,额定工况下的exergy效率为57.4%。并具有良好的变负荷特性,变负荷时exergy效率始终维持在56%以上,适用于分布式供能系统。

基于燃气轮机的MCFC/MGT混合动力系统特性

针对增压型熔融碳酸盐燃料电池/微型燃气轮机(MCFC/MGT)混合动力系统进行了系统设计、部分负荷特性和系统启动特性的分析.为实现系统的商业化,采用了基于现有微型燃气轮机进行系统设计的方法,对不同控制方式下系统的部分负荷运行特性进行了比较,提出了系统启动方案并对启动过程中可能出现的问题及系统特性进行了分析.结果表明,基于燃气轮机所设计系统性能要比基于MCFC的性能稍差,在系统部分负荷运行时保持MCFC的工作温度有助于系统性能的改善,由于MCFC自身的特点这种系统不适合频繁的启动.

增压型MCFC/MGT混合动力系统中燃料电池的特性分析

针对增压型熔融碳酸盐燃料电池(MCFC)与现有微型燃气轮机(MGT)设计的混合动力系统,分析了在部分负荷运行时MCFC的特性;在MCFC建模过程中,考虑了电流密度和电池工作温度等参数的影响,并将模拟结果与其实验数据进行对比;应用压气机和透平的特性曲线建立了MGT在非设计工况下的分析模型;提出了4种不同的控制方式,以控制系统的部分负荷运行,并应用所建模型分析了系统中MCFC在不同控制方式下的特性.结果表明:通过有效的控制手段以保持较高的MCFC工作温度,可使MCFC在部分负荷运行时的效率高于设计点值;MCFC的性能对混合动力系统影响很大;在部分负荷运行时需要维持较高的电池工作温度以提高系统性能.

Reliability Assessment of Microgrid Using Sequential Monte Carlo Simulation

Sequential Monte Carlo simulation method is introduced to the reliability assessment of microgrid,and a Weibull distribution wind speed model is built to simulate the hourly wind speed of a specific site.Wind turbine generator model combined with a two-state reliability model is applied to Monte Carlo simulation method,and results show that the wind turbine reliability model works well with sequential Monte Carlo simulation.A two-state reliability model of micro gas turbine and a load model from IEEE reliability test system （IEEE RTS） are also introduced to the reliability evaluation of microgrid.Case studies show that Monte Carlo simulation method is flexible and efficient dealing with microgrid consisting of renewable resources with fluctuation characteristics.

Micro gas turbine:Developments,applications,and key technologies on components

Owing to their precedent characteristics,micro gas turbines(MGTs)have been favored as popular power machinery in plenty of energy systems such as distributed energy systems,range extenders,solar power generations,fuel cell systems and individual power supplies.Their specific features essentially include but are not limited to strong fuel adaptability,low emissions,flexible structure,and easy maintenance.Over the past 20 years,various types of MGTs have been developed.Classical and forward-looking technologies have been employed in the design and production of MGTs and their components.Among them,fully radial flow structures,gas lubricated bearings and efficient recuperators are typical approaches to enhance the overall performance and compactness,however,the exploitation of ceramic based materials and intelligent algorithms in component design can also assist in improving the performance.The applications of MGTs have been expanded to many fields,and the research on related components has also made new progress.Due to the time frame,there is no systematic summary of the latest relevant research,so it is essential to have a comprehensive understanding of the applications of MGTs and their pertinent components.This paper aims to present a comprehensive review on MGTs,covering the development status,applications,factors of performance and representative explorations of their components.Some investigations regarding the characteristics of commercial MGTs are also conducted.Applications in distributed energy,range extenders,solar generations,and fuel cell systems are distinctly introduced.Recent research work on compressors,turbines,combustors,recuperators,and rotor systems are reviewed and analyzed.The technologies and methods associated with materials,manufacturing,and cycles beneficial to the future development of MGTs are also explained and discussed in some detail.

An Integrated Approach for Optimal Design of Micro Gas Turbine Combustors

The present work presents an approach for the optimized design of small gas turbine combustors, that integrates a0-D code, CFD analyses and an advanced game theory multi-objective optimization algorithm. The output of the0-D code is a baseline design of the combustor, given the required fuel characteristics, the basic geometry (tubularor annular) and the combustion concept (i.e. lean premixed primary zone or diffusive processes). For the optimizationof the baseline design a simplified parametric CAD/mesher model is then defined and submitted to a CFDcode. Free parameters of the optimization process are position and size of the liner hole arrays, their total area andthe shape of the exit duct, while different objectives are the minimization of NOx emissions, pressure losses andcombustor exit Pattern Factor. A 3D simulation of the optimized geometry completes the design procedure. As afirst demonstrative example, the integrated design process was applied to a tubular combustion chamber with alean premixed primary zone for a recuperative methane-fuelled small gas turbine of the 100 kW class.

Feasibility of Pulse Combustion in Micro Gas Turbines

In gas turbines, a fast decrease of efficiency appears when the output decreases; the efficiency of a large gas tur-bine （20...30 MW） is in the order of 40 %, the efficiency of a 30 kW gas turbine with a recuperator is in the order of 25 %, but the efficiency of a very small gas turbine （2...6 kW） in the order of 4...6 % （or 8... 12 % with an op- timal recuperator）. This is mainly a result of the efficiency decrease in kinetic compressors, due to the Reynolds number effect. Losses in decelerating flow in a flow passage are sensitive to the Reynolds number effects. In con- trary to the compression, the efficiency of expansion in turbines is not so sensitive to the Reynolds number; very small turbines are made with rather good efficiency because the flow acceleration stabilizes the boundary layer. This study presents a system where the kinetic compressor of a gas turbine is replaced with a pulse combustor. The combustor is filled with a combustible gas mixture, ignited, and the generated high pressure gas is expanded in the turbine. The process is repeated frequently, thus producing a pulsating flow to the turbine; or almost a uni- form flow, if several parallel combustors are used and triggered a/ternately in a proper way. Almost all the com- pression work is made by the temperature increase from the combustion. This gas turbine type is investigated theoretically and its combustor also experimentally with the conclusion that in a 2 kW power size, the pulse flow gas turbine is not as attractive as expected due to the big size and weight of parallel combustors and due to the ef- ficiency being in the order of 8 % to 10 %. However, in special applications having a very low power demand, below 1000 W, this solution has better properties when compared to the conventional gas turbine and it could be worth of a more detailed investigation.

Development of Compressor for Ultra Micro Gas Turbine

The major problems for the development of an ultra micro gas turbine system were discussed briefly from the stand point of the internal flow and the performance characteristics. Following to these, the development of ultra micro centrifugal compression systems for the ultra micro gas turbine is explained with the design and the manufacturing processes. The measured results of ultra micro centrifugal compressors are shown.

A data-driven approach for predicting long-term degradation of a fleet of micro gas turbines

Predictive health monitoring of micro gas turbines can significantly increase the availability and reduce the operating and maintenance costs.Methods for predictive health monitoring are typically developed for large-scale gas turbines and have often focused on single systems.In an effort to enable fleet-level health monitoring of micro gas turbines,this work presents a novel data-driven approach for predicting system degradation over time.The approach utilises operational data from real installations and is not dependent on data from a reference system.The problem was solved in two steps by:1)estimating the degradation from time-dependent variables and 2)forecasting into the future using only running hours.Linear regression technique is employed both for the estimation and forecasting of degradation.The method was evaluated on five different systems and it is shown that the result is consistent(r>0.8)with an existing method that computes corrected values based on data from a reference system,and the forecasting had a similar performance as the estimation model using only running hours as an input.

底层MCFC/MGT混合装置分析

基于分析的理论,在IPSEpro仿真环境下建立了底层熔融碳酸盐燃料电池/微型燃气轮机混合装置稳态性能仿真模型。利用该模型对底层系统在额定工况和变工况下的稳态性能进行了仿真研究。仿真结果表明,底层熔融碳酸盐燃料电池/微型燃气轮混合装置系统具有较高的效率,额定工况下的效率为55%,并具有良好的变负荷特性,适用于分布式供能系统。

Numerical analyses and experiment investigations of an annular micro gas turbine power system using fuels with low heating values

This study investigates the effects of using fuels with low heating values on the performance of an annular micro gas turbine(MGT)experimentally and numerically.The MGT used in this study is MW-54, whose original fuel is liquid(Jet A1).Its fuel supply system is re-designed to use biogas fuel with low heating value(LHV).The purpose is to reduce the size of a biogas distributed power supply system and to enhance its popularization.This study assesses the practicability of using fuels with LHVs by using various mixing ratios of methane(CH4)and carbon dioxide(CO2).Prior to experiments,the corresponding simulations,aided by the commercial code CFD-ACE+,were carried out to investigate the cooling effect in a perforated combustion chamber and combustion behavior in an annular MGT when LHV gas was used.The main purposes are to confirm that there are no hot spots occurring in the liners and the exhaust temperatures of combustor are lower than 700°C when MGT is operated under different conditions.In experiments,fuel pressure and mass flow rate,turbine rotational speed,generator power output,and temperature distribution were measured to analyze MGT performance.Experimental results indicate that the presented MGT system operates successfully under each tested condition when the minimum heating value of the simulated fuel is approximately 50%of pure methane.The power output is around 170 W at 85000 r/min as 90%CH4 with 10%CO2 is used and 70 W at 60000 r/min as 70%CH4 with 30%CO2 is used.When a critical limit of 60%CH4 is used,the power output is extremely low. Furthermore,the best theoretical Brayton cycle efficiency for such MGT is calculated as 23%according to the experimental data while LHV fuel is used.Finally,the numerical results and experiment results reveal that MGT performance can be improved further and the possible solutions for performance im- provement are suggested for the future studies.

Micro Gas Turbine Range Extender Performance Analysis Using Varying Intake Temperature

A micro gas turbine(MGT)can potentially be an alternative power source to the conventional internal combustion engine as a range extender in hybrid electric vehicles.The integration of the MGT into a hybrid vehicle needs a new approach for technical validation requirements compared to the testing of an internal combustion engine.Several attributes of the MGT are predicted to cause concerns for vehicle sub-system requirements such as high ambient temperature and start-stop behaviour.This paper describes the results from specially developed experimental techniques for testing the MGT in a typical automo-tive environment.A black box MGT was used in this study for performance investigation during hot and cold starts.The MGT was instrumented and fitted with automotive standard components to replicate typical vehicle operational conditions.The intake air temperature was varied between 10 and 24°C.A significant reduction in the power output of the MGT was observed as the intake temperature was increased.The proposed case scenario caused a reduction in nitrogen oxide emis-sions in the range of 0.02−0.04 g/km because of the lower combustion temperature at high intake temperature.However,hydrocarbon and carbon monoxide emissions have not shown a noticeable reduction during the power output degradation.The experimental results have highlighted the potential issues of using the MGT at higher intake temperatures and suggest design change to take the effect of higher engine bay temperature into account.

微燃机-冷热电联供机组的Hammerstein模型及非线性广义预测控制

为研究微燃机-冷热电(MGT-CCHP)联供机组动态运行特性及控制策略,采用Hammerstein模型结构快速辨识其非线性动态特性,并将非线性动态特性以串联的非线性静态模型和线性动态模型表示.采用逐步回归法确定动态模型阶次并采用粒子群算法辨识模型参数,得到易于复现的块结构化模型.基于Hammerstein预测模型,设计了MGT-CCHR冷负荷跟踪非线性广义预测控制器.利用Hammerstein模型分块描述对象静态与动态特性的结构特点,将非线性广义预测控制转化为线性广义预测控制与非线性静态函数求根问题,使控制量求解简化.通过与最优参数PID控制器的仿真结果比较表明,所设计的非线性广义预测控制器具有改善冷负荷跟踪性能和节能控制的效果.

超微型燃气轮机系统中离心叶轮的数值模拟

千瓦级超微型燃气轮机(UMGT)可用于移动电源、小型飞机推进系统及分布式发电系统,具有广阔的应用前景。本文以3kW级超微型燃气轮机作为研究对象,对用于燃机系统中的高速小尺寸离心叶轮进行了设计和数值分析。同时,本文对不同壁面温度下离心叶轮的性能进行了数值模拟,初步研究了传热对离心叶轮性能的影响及其作用机理。