双螺杆水蒸气压缩机喷水冷却特性研究

水蒸气压缩机在机械蒸汽压缩、海水淡化、高温热泵等工业领域具有良好的节能潜力与应用前景。喷水可以有效解决排气温度过高的问题,提高水蒸气压缩机的性能。为了获得最佳喷水量的变化规律,建立了双螺杆水蒸气压缩机喷水冷却实际工作过程的传热传质模型,考虑喷入水的汽化、泄漏、闪蒸、输送等对实际压缩过程的影响。与试验结果对比,计算结果误差在±5%以内,表明模型能够较好地预测喷水螺杆水蒸气压缩机的工作过程与性能。利用此模型,研究了喷水量、转速和吸气压力对压缩机性能的影响。研究结果表明,喷水可以有效提升压缩机性能,相比不喷水而言,喷水在部分工况下可将压缩机容积效率提高11.9%,绝热效率提高17.2%,且存在最佳喷水量,使得喷水螺杆水蒸气压缩机的性能最佳,最佳喷水量随着转速、吸气压力的增加而增加;最佳喷水比主要受转速的影响,随着转速的增大而增大,其最佳喷水比在8.9%～10.4%之间;随着吸气压力降低,压差增大,喷水螺杆水蒸气压缩机的性能降低较快,表明泄漏对喷水螺杆水蒸气压缩机性能影响较大,尚需进一步研究。     

螺杆蒸汽压缩机工作过程喷水冷却特性研究

喷水能够提高螺杆蒸汽压缩机的压比和饱和温升,扩展蒸汽压缩机的应用范围。为研究螺杆蒸汽压缩机的喷水冷却特性,建立喷水螺杆蒸汽压缩机的数学模型,考虑喷入水与压缩蒸汽的换热蒸发及其泄漏闪蒸,并试验验证了模型的准确性。利用所建数学模型,分析与讨论压缩机压比、喷水量、喷水温度及转速对压缩机工作过程的影响。研究结果表明,喷水不仅可以降低排汽温度、使蒸汽压缩机稳定运行,还可以使压缩过程更接近等温过程;压缩机实际运行时喷入水主要集中在压缩过程后期及排汽过程蒸发;压缩机欠压缩运行时,排汽腔内蒸汽对压缩过程影响不大;若压缩蒸汽任一转角都能被冷却至饱和,则喷水温度对压缩过程及运行效率基本没有影响;为了有效控制排汽温度,喷水孔口水流量需要随压缩机转速做相应的调节。     

卸荷工况下喷油螺杆空压机性能特性研究

通过试验研究分析了在卸荷工况下的螺杆压缩机轴承供油量、排气量、轴承温度、比功率、油气比等性能参数的变化情况。研究发现：在同一排气压力下，排气量随着转速上升而下降；在同一转速下，排气量随排气压力上升急剧下降；随着转速和排气的上升，比功率增长率上升；在排气温度与喷油温度保持稳定的情况下，随着排气压力上升，轴承供油量、轴承温度上升；油气体积比随着排气压力上升而上升，最高时达到了20％，严重背离了合理的工况要求。     

Effect of surface etching on condensing heat transfer

This study conducted experiments on humid air condensation during heat transfer in an air preheating exchanger attached to a home condensing boiler to improve thermal efficiency. An etchant composed of sulfuric acid and sodium nitrate was used to create roughness on the heat exchanger surface made from STS430J1L. A counter flow heat exchanger was fabricated to test the performance of heat transfer. Results showed that the overall heat transfer coefficients of all specimens treated with etchant improved with respect to the original specimens (not treated with etchant), and the overall heat transfer coefficient of the 60 s etching specimen increased by up to 15%. However, the increasing rate of the heat transfer coefficient was disproportional to the etching time. When the etching time specifically increased above 60 s, the heat transfer coefficient decreased. This effect was assumed to be caused by surface characteristics such as contact angle. Furthermore, a smaller contact angle or higher hydrophilicity leads to higher heat transfer coefficient.

     

热传导在机械节能上的应用

对热传导涂料应用在单级往复式压缩机上改善等热效率进行了初步研究，对压缩机不同散热措施的测试发现，强制热对流的效率只有轻微改善，但对于用增加热传导涂料的实验中，发现空气质量流量增加15％，等热效率从62．7％提高至68．1％，增加热传导涂料的方法可应用于已安装的设备上而不需添加附件或额外的维修保养费用，此方法亦可推广至其它热机上。     

Experimental investigation on the effect of charge temperature on ethanol fueled HCCI combustion engine

In this investigation, an attempt has been made to study by varying the charge temperature on the ethanol fueled Homogeneous charge compression ignition (HCCI) combustion engine. Ethanol was injected into the intake manifold by using port fuel injection technique while the intake air was heated for achieving stable HCCI operation. The effect of intake air temperature on the combustion, performance, and emissions of the ethanol HCCI operation was compared with the standard diesel operation and presented. The results indicate that the intake air temperature has a significant impact on in-cylinder pressure, ringing intensity, combustion efficiency, thermal efficiency and emissions. At 170°C, the maximum value of combustion efficiency and brake thermal efficiency of ethanol are found to be 98.2% and 43%, respectively. The NO emission is found to be below 11 ppm while the smoke emission is negligible. However, the UHC and CO emissions are higher for the HCCI operation.

     

压缩空气中水分的来源、危害与对策

压缩空气中的水分主要来源于空压机工作时从进气口吸入的大气中所含的水分。单位时间内进入压缩空气系统的水量与空压机排量、进气环境温度、湿空气的相对湿度有关。压缩空气管路中冷凝水的多少，与压缩空气压力和管道中压缩空气的温度有关。随着压力升高、温度降低、饱和湿空气中含水量减少，析出的冷凝水增加。通过计算给出了不同温度、不同压力下压缩空气中含水量的计算方法和典型数据以及具体系统中冷凝水量的计算方法。结合某大型露天矿设备压缩空气系统应用实例，分析了压缩空气中水分危害的具体形式，不同除水方法的应用及效果，提出了不同工况下选取空气后处理设备的原则，可以为类似应用环境的气路设计和维护提供参考。     

Performance test and component characteristics evaluation of a micro gas turbine

This study aims to analyze engine performance and component characteristics of a micro gas turbine based on detailed measurement of various parameters. A test facility to measure performance of a micro gas turbine was set up and performance parameters such as turbine exit temperature, exhaust gas temperature, engine inlet temperature, compressor discharge pressure and temperature, and fuel and air flow rates were measured. The net gas turbine performance (power and efficiency based on the gas turbine shaft end) was isolated and analyzed. With the aid of measurement based simulation, component characteristic parameters such as turbine inlet temperature, compressor efficiency, turbine efficiency and recuperator effectiveness were estimated. Behaviors of the estimated characteristic parameters with operating condition change were examined and sensitivities of estimated parameters to the measured parameters were analyzed.     

R427a应用于空气源热泵热水器的性能研究

对制冷剂R427a在空气源热泵热水器上的应用做了研究,并与常用制冷剂R22和R134a在典型工况下做了对比分析,分析了3种制冷剂的吸排气压力、吸排气温度、压缩机功率、制热量、性能系数随环境工况变化的关系,得出了各特性参数的变化规律;另外在5℃进出水温差条件下,热水进水温度每上升5℃(如50℃进水,55℃进水,60℃进水)时,制热量下降2%～3%;COP下降10%～11%;功率上升11%～13%;吸排气压力分别上升3%～4%、10%～15%;吸排气温度分别上升5%、10%左右;这些为热泵热水器的设计使用及工质选用提供了参考。     

Thermodynamic and aerodynamic meanline analysis of wet compression in a centrifugal compressor

Wet compression means the injection of water droplets into the compressor of gas turbines. This method decreases the compression work and increases the turbine output by decreasing the compressor exit temperature through the evaporation of water droplets inside the compressor. Researches on wet compression, up to now, have been focused on the thermodynamic analysis of wet compression where the decrease in exit flow temperature and compression work is demonstrated. This paper provides thermodynamic and aerodynamic analysis on wet compression in a centrifugal compressor for a microturbine. The meanline dry compression performance analysis of centrifugal compressor is coupled with the thermodynamic equation of wet compression to get the meanline performance of wet compression. The most influencing parameter in the analysis is the evaporative rate of water droplets. It is found that the impeller exit flow temperature and compression work decreases as the evaporative rate increases. And the exit flow angle decreases as the evaporative rate increases.     

直流变频跨临界CO2热泵热水器的性能试验研究

在应对全球变暖,高效环保工质的替代研究中,跨临界CO2循环得到了重视.本文搭建了直流变频空气源CO2热泵热水系统实验装置;在最佳充注量0.880kg工况下,分别通过改变压缩机频率、电子膨胀阀开度、水流量来研究了该机组的性能.结果表明:该机组能产生65℃以上高温热水;其相应高压压力达9.5MPa以上,机组处于跨临界运行.在合理匹配压缩机频率、气冷器进水流量和电子膨胀阀开度等参数的基础上,可使机组高效运行,实现节能减排的目标.     

Parametric simulation and performance analysis of a solar gas turbine power plant from thermodynamic and exergy perspectives

Using solar energy in gas turbine cycles is a new method that can improves the efficiency of gas turbines. Placing a solar receiver before a combustion chamber can raise the temperature of the air coming into the chamber and reduce the consumption of fuel in the chamber. The system that combines a solar energy receiver with a gas turbine cycle is technically called a “solar gas turbine”. The goal of this paper is the parametric simulation and performance analysis of a gas turbine cycle equipped with a solar receiver from thermodynamic and exergy aspects of view. The selected parameters in this study, include the pressure ratio of compressor, the temperature of gases at the turbine inlet and the direct normal irradiance. The obtained results indicate that the fuel consumption of this combined system is reduced by using a solar receiver and the temperature of gases entering the combustion chamber increased. The reduction of consumed fuel, in turn, reduces the rate of exergy destruction in the combustion chamber. Another important point is that the solar receiver itself has the least amount of exergy destruction. The net power generated by a solar gas turbine cycle is 10 % higher than that produced by a simple gas turbine cycle. Also, the studies show that the electrical efficiency of a solar gas turbine cycle is about 41 % higher than the simple gas turbine cycle.

     

用于压缩空气储能的微米级水雾冷却等温压缩实验研究

压缩空气储能(CAES)是一种大规模储能技术,可以用于调节城市电力供需,缓解用电高峰电力短缺,减少电网容量建设。目前,储能技术逐渐开始应用于城市,当电价下降时,采用电池储存电力,价格上升时,释放电力,利用峰谷电价差实现盈利。与电池相比,CAES容量大(100 MWh,电池小于10 MWh)、环保(无重金属污染),使用寿命长。但由于储能效率过低,通过电价差盈利空间小,投资回收期长是限制其商业应用的重要因素之一。目前,多数压缩空气储能系统都基于绝热压缩,大约有一半的电力被转化成了热量并耗散。由于压缩时空气的温度上升,导致压缩功增加,并转化得到更多的热。许多研究聚焦在增强压缩空气的散热来达到等温压缩。本研究提出将微米级(10~100 μm)水雾喷入压缩空气与之混合,吸收压缩热,降低压缩空气温度,以实现等温。通过实验对压缩空气压力,体积和温度的变化特性进行了分析。对于总体积为0.94 L的压缩腔,当压缩比为2时,水雾冷却后,压缩功从177.9 J/循环(绝热)下降到121.2 J/循环,且效率达到88.7%(绝热61.6%)。     

采用微通道蒸发器的分离式热管空调传热性能的试验研究

设计了一套采用微通道换热器作为蒸发器的分离式热管空调,并试验研究了充液率、室内外温差和风机风量等因素对其传热性能的影响。试验结果表明:充液率过大过小均会影响系统的传热性能,其最佳充液率为120%左右;室内外温差越大分离式热管空调传热效果越好,空调传热量在室内外温差为20℃时比室内外温差为8℃时增加了228%;当风机风量低于2000m3/h时,传热量和EER随着风量的增加而增大,当风机风量超过2000m3/h时,增加风量对传热量的影响减小,而EER开始呈现下降趋势。     

自循环机匣处理喷气位置对压气机性能的影响

为了揭示自循环机匣处理对Stage 37气动性能的影响机理，利用数值模拟方法研究了不同喷气位置对压气机气动性能的影响。在设计转速时，分析了不同喷气位置的自循环机匣处理装置的叶尖流场，探讨了自循环机匣处理的扩稳机理。数值模拟结果显示：不同喷气位置的自循环机匣处理在略微降低压气机效率的情况下，能够分别扩大2.96%，2.72%，2.83%，2.6%的失速裕度；设计转速时，Stage 37中转子叶尖区激波/叶尖泄漏涡相互干涉以及泄漏涡破裂后产生的阻塞区，是影响Stage 37压气机内部流动失稳的关键因素。自循环机匣处理的扩稳机制主要在于利用高速喷气抑制叶尖泄漏涡的破碎程度，减小叶尖阻塞区面积，进而提高压气机的失速裕度。     

A new method for field test of the heating capacity of air source heat pumps

The operation performance measurement of the air source heat pumps in the field, in which conditions are complicated and the accuracy could not be ensured, is very crucial for its performance evaluation and improvement. In this investigation, a novel method for measuring the heating capacity of the air source heat pump is established. An auxiliary electric heater is installed along the pipeline between the compressor and the condenser, and the refrigerant temperature difference caused by the heater is gathered to calculate the refrigerant mass flow rate based on the energy conservation. The heating capacity is calculated with the measured data of the refrigerant enthalpy at the inlet and outlet of the condenser and the refrigerant mass flow rate of the compressor discharge pipe. The validation results in laboratory tests show that the measured heating capacity accuracy is within 9.2%. It is also found that the impact of the novel test method on the heating capacity of the air source heat pumps is below 1.7%, and the power consumption of the tested units is increasing of within 1.8% compared with it when the electric heater is off. The refrigerant enthalpy difference method with an electric heater presented in this research can be applied to measure the heating capacity of different air source heat pump air heaters accurately in the field, which will be much helpful to improve the performance for cleaning heating in northern China.     

钢管控制冷却物理模拟平台的建立及传热边界条件的确定

目前关于钢管控制冷却的研究没有专门针对其关键问题传热边界条件进行深入分析。为此基于钢管热机械控制工艺实际,建立钢管控制冷却全尺寸物理模拟平台,测定28CrMoVNiRE油井管在水量11.4 L/min、气压0.2 MPa,水量11.4 L/min、气压0.3 MPa和水量18.0 L/min、气压0.3 MPa三种不同气雾控制冷却条件下的冷却曲线,通过反传热法计算钢管表面的热流密度和换热系数,分析钢管在气雾控制冷却条件下的传热边界条件。结果表明,影响钢管气雾控制冷却传热的关键因素是气水混合比,其最佳值为6～7;换热系数随温差ΔT的下降依次经历高温慢速增加阶段、中温稳定阶段和低温快速增加阶段。采用有限元正算法,验证了反传热计算结果的可靠性。钢管控制冷却后细化的微观组织验证了气雾控制冷却物理模拟技术的可行性。钢管控制冷却传热边界条件的确定对于实现钢管在线气雾控制冷却工艺具有重要的指导意义。     

Effects of saturation temperature variation due to pressure drop of working fluid in heat exchanger on heat transfer performance

The effect of the saturation temperature drop on the heat transfer performance of a heat exchanger was analyzed under air-conditioner condensing condition, air-conditioner evaporating condition, and refrigerator evaporating condition. The thermodynamic analysis results show that the heat transfer capacity due to the pressure drop of the saturated refrigerant was at least 2.3 % and at most 91.1 % compared to the evaluated heat transfer capacity assuming no pressure loss. The rate of change of heat transfer capacity was the largest in the order of R600a, R1234yf, R134a, R410A, and R32. Heat exchanger performance simulation under practical air-conditioner operating conditions showed that the heat transfer capacity was reduced by 0.72 % due to refrigerant pressure drop under the condensing condition. On the other hand, the heat transfer capacity was increased by 26.55 % under the evaporating condition.

     

等温容器放气过程中对流换热模型的研究

为了提高等温容器的性能,对等温容器放气过程中的对流换热模型进行了研究。用4个已知流量特性的电磁阀分别对4种等温容器进行了放气实验,采集放气过程中的压力曲线,并采用“停止法”得到放气过程中的温度曲线。基于等温容器放气过程的热力学模型,结合放气过程中的压力曲线和温度曲线,确定了放气过程中的对流换热系数,最后利用相似原理拟合得到了放气过程中声速阶段和亚声速阶段的对流换热经验关系式。声速阶段和亚声速阶段的经验关系式不仅体现了放气速度对对流换热的影响,还反映了铜丝填充密度,也就是孔隙率对换热的影响;声速阶段的经验关系式中还引入了空气压缩比,体现了空气在高压缩状态下压缩性对对流换热的影响。     

新型两级压缩热泵中高温工况循环性能分析

中高温热泵系统中在工业领域有广泛的应用,但其排气温度偏高。本文从降低压缩机排气温度角度,设计一种双级压缩新型热泵系统。系统由高低级压缩机、分凝器、两个节流机构等组成。以循环性能较好的两种工质R134a和R152a为系统循环工质,理论分析结果表明:在中高温工况下,新系统工质R152a循环性能系数COP优于R134a,在相同工况下工质R152a循环性能COP比R134a高7%⁸%;高温级压缩机排气温度均随中间压比的升高而降低;排气温度与传统单级压缩系统相比有38%;高温级压缩机排气温度均随中间压比的升高而降低;排气温度与传统单级压缩系统相比有3¹2℃的降幅。