天然气发动机驱动制冷系统及发动机余热的利用技术

本文简要介绍天然气发动机驱动的制冷系统的发展及现状；并分析了变工况下发动机余热的综合利用。     

余热制氢发动机的开发研究

余热制氢发动机利用发动机排气余热将甲醇裂解为氢，并将裂解的氢与汽油混合燃烧。本文叙述了余热制氢发动机的结构特点和工作原理，从氢燃料的储存、发动机的新能源和排放污染等方面分析了余热制氢发动机的优势，给出一些余热制氢发动机的排放试验数据，探讨余热制氢发动机的应用可行性。     

油气田大功率燃气发动机烟气余热回收与计算

燃气发动机是油气田生产中大量使用的高耗能动力设备,运行过程中排放的高温烟气为国家标准中规定的1级余热资源。针对大部分油气田现有工艺没有对燃气发动机排放到大气中的余热资源进行回收利用,提出了燃气发动机烟气余热加热导热油方案,给出了方案的余热资源量计算方法。以塔里木油田高压注气压缩机组为例,应用烟气余热加热导热油方案,根据余热资源量计算方法对余热资源量进行评估计算。应用此方案塔里木油田高压注气站每年可以减少消耗天然气262×10~4m~3/a,且投资回收期约为1.4年,节能效果和经济效益好。燃气发动机余热资源的回收方案与源量计算方法,为油气田开展类似节能改造提供理论支持和技术导向。     

119ONT型天然气发动机调速器

１１９ＯＮＴ型天然气发动机调速器牟善祥１前言１１９ＯＮＴ型天然气发动机是以天然气、石油液化气等可燃性气体为燃料的发动机，主要用于驱动抽油机，取代电动机。其调速器为离心式全程机械调速器，能直接感应曲轴转速，反应灵敏。２结构特点１１９ＯＮＴ型天然气发动机...     

天然气发动机用排气催化剂

天然气发动机用排气催化剂作为降低汽车发动机排气中有害物质污染环境的重要措施之一，是研制以天然气为燃料的汽车发动机。在天然气发动机的排气中，除含有碳酸气和水分之外，还有排放法规规定的一氧化碳、碳氢化合物以及氮氧化物。其中的碳氢化合物大部分是甲烷。因为将...     

用快速压缩装置研究直喷式天然气发动机排放特性

使用快速压缩装置进行了直喷式天然气发动机排放特性的研究。测量了三种不同方式下的排放，并与均相混合气燃烧情况进行了对比。实验结果表明，在宽广的当量比范围内，天然气直喷方式的燃烧效率高于0.95。由于混合气的分层燃烧，天然气喷射方式在宽广的当量比范围内保持较低的HC排放量，同等功率下的低CO2排放量，低NOx排放量，其NOx排放在理论当量比处的降低更为明显。直喷天然气发动机既具备柴油机发动机效率高的特点，又具备预混燃烧发动机排放低的特点。     

氢-汽油双燃料发动机性能试验研究

介绍一种氢—汽油双燃料发动机，这种双燃料发动机装有余热制氢装置，可用甲醇制取氢并燃用氢与汽油混合燃料。作者对余热制氢装置及氢—汽油双燃料发动机的各项性能进行试验研究。试验结果表明，装有余热制氢装置的氢—汽油双燃料发动机功率和扭矩有所提高，外特性和负荷特性燃油消耗率下降5．3％一7．5％；怠速排放中CO和HC均有所减少。     

T6120F风冷天然气发动机的研制开发

T6120F风冷天然气发动机是借鉴风冷柴油机而研制开发的我国第一代风冷天然气发动机，它采用强制式空气冷却方式，避免了水冷发动机冷却系统容易出现的各种问题，便于实现无人值守。重点介绍T6120F风冷天然气发动机的结构特点、性能指标和台架试验。     

天然气发动机的研究现状

天然气能降低发动机的有害物排放,是一种比较理想的发动机代用燃料。稀燃天然气发动机具有较高的热效率和较低的NOx排放。均质充量压缩着火(HCCI)燃烧也是提高稀燃天然气发动机热效率的方法之一,并有很低的NOx排放。本文综述了稀燃天然气发动机和HCCI天然气发动机的研究进展,尤其是燃烧室形状、点火系统、充量分层、加氢等对天然气发动机性能的影响及天然气HCCI发动机的燃烧与排放特点。     

天然气发动机掺氢燃烧的探讨

根据氢气、天然气和天然气掺氢燃烧的一些特性，结合世界各国对天然气掺氢燃烧在发动机上应用的研究状况。探讨天然气发动机掺氢燃烧应用的前途和可行性。     

天然气热电冷总能系统应用模式的探讨

我国的天然气储量相对有限，并且远离需求中心；与国际水平相比，中国的天然气价格较高。为了使天然气得到合理有效的利用，应该提高能源的利用率。针对这种情况，提出了天然气热电冷总能系统的应用模式，并对不同模式所用的几种主要动力设备进行了比较，以燃气内燃机加余热型直燃机和燃气机热泵系统为例对联结方式进行了论述。最后对系统的特点以及在国内的发展和应用情况进行了介绍，并指出了在我国的发展前景。     

Brayton refrigeration cycle for gas turbine inlet air cooling

In this paper, a new approach to enhance the performance of gas turbines operating in hot climates is investigated. Cooling the intake air at the compressor bell mouth is achieved by an air Brayton refrigerator (reverse Joule Brayton cycle) driven by the gas turbine and uses air as the working fluid. Fraction of the air is extracted from the compressor at an intermediate pressure, cooled and then expands to obtain a cold air stream, which mixes with the ambient intake. Mass and energy balance analysis of the gas turbine and the coupled Brayton refrigerator are performed. Relationships are derived for a simple open gas turbine coupled to Brayton refrigeration cycle, the heat rejected from the cooling cycle can be utilized by an industrial process such as a desalination plant. The performance improvement in terms of power gain ratio (PGR) and thermal efficiency change (TEC) factor is calculated. The results show that for fixed pressure ratio and ambient conditions, power and efficiency improvements are functions of the extraction pressure ratio and the fraction of mass extracted from the air compressor. The performance improvement is calculated for ambient temperature of 45°C and 43.4% relative humidity. The results indicated that the intake temperature could be lowered below the ISO standard with power increase up to 19.58% and appreciable decrease in the thermal efficiency (5.76% of the site value). Additionally, the present approach improved both power gain and thermal efficiency factors if air is extracted at 2 bar which is unlike all other mechanical chilling methods. Copyright © 2007 John Wiley & Sons, Ltd.     

Modelling and validation of a gas engine heat pump working with R410A for cooling applications

Gas engine heat pumps play an important role in energy saving and environment protection in both cooling and heating applications. In the present work, a thermal modelling of the gas engine driven heat pump in cooling mode is performed and system main parameters such as cooling capacity, gas engine energy consumption and primary energy ratio (PER) are computed. The modelling of the gas engine heat pump includes modelling of the scroll compressor, the plate evaporator and the gas engine. Discharged refrigerant mass flow rate and compressor power represent the main output parameters of the compressor semi-empirical model. Using the discharged refrigerant mass flow rates along with the available evaporation heat transfer correlations, the system cooling capacity is deduced. Based on the present experimental data, a correlation of gas engine energy consumption as function of compressor power, engine speed and ambient air temperature is obtained. Furthermore, the gas engine heat pump model is validated by comparing experimental and simulation data. The model error percentages to predict the cooling capacity, the gas engine energy consumption and the PER are 7%, 5%, 6% respectively.     

转子式压缩机吸气带液时排气状态的变化

滚动转子式压缩机具有较好的抗湿压缩性能,利用少量吸气带液可有效降低压缩机排气温度,且不造成额外的系统成本.对滚动转子式压缩机少量吸气带液时,排气温度、排气比焓的变化趋势进行了实验研究,并对压缩机功耗、吸气比焓和机壳散热量等三个排气比焓的影响因子进行了分析.结果表明:少量吸气带液能有效降低排气温度,且压缩机运行性能良好;当吸气干度x为0.9x1.0时,三个影响因子均趋向定值,且机壳散热所占比例很小(低于1%).     

Behaviour of refrigerant mixtures with gas/liquid injection

In this paper, the impact of gas/liquid injection on the behaviour of new alternative refrigerant mixtures such as; R-410A, R-507, R-407C, and R-404A are discussed, analysed and presented. The test results were obtained using an air–source heat pump set up with enhanced surface tubing heat exchanger under various gas/liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE Standards. The performance data demonstrated that as gas/liquid injection increases compressor head pressure and discharge temperature decrease and this has a positive effect in protecting the compressor. The effect of gas/liquid injection on mixture behaviour varies from mixture to another depending upon the mixture composition. Furthermore, hot gas injection appears to have a significant and positive influence on the COP. The performance of refrigerants R-407C and R-404A has been enhanced with 5% gas injection and mix of gas and liquid 5% injection, respectively. The data presented in these figures also show that other hot gas injection ratios and gas/liquid mix degrade the heat exchanger performance. Copyright © 2003 John Wiley & Sons, Ltd.     

压缩机中间冷却器采用不锈钢波纹管的试验研究

采用新型不锈钢波纹管代替壳管式换热器中的直管,对压缩机中间冷却器进行了改造,并进行了实际运行测试和比较分析。结果表明：波纹管换热器的天然气出口温度能够达到甚至低于压缩机的设计值,换热效率比例管换热器的高61％,压缩机的操作正常平衡,维护工作最大大降低,达到长周期运行的目的。     

热传递对涡轮增压器效率特性影响的研究

在涡轮增压器热试台架上进行涡轮和压气机效率特性测量时,由于高温涡轮与相对温度较低的压气机之间有明显温差,造成热量从涡轮传向压气机,会使测量得到的涡轮和压气机的效率分别高于和低于实际值。本文对增压器的热传递现象进行了分析,并通过一种有效计算方法对涡轮和压气机的效率特性进行了热传递校准。校准后的涡轮和压气机效率特性与增压器冷试台架上测得的数据符合较好,最大误差低于4.7%。     

Performance of a multi-functional direct-expansion solar assisted heat pump system

This paper reports on the long-term performance of a direct-expansion solar assisted heat pump (DX-SAHP) system for domestic use, which can offer space heating in winter, air conditioning in summer and hot water during the whole year. The system employs a bare flat-plate collector array with a surface area of 10.5 m², a variable speed compressor, a storage tank with a total volume of 1 m³ and radiant floor heating unit. The performance under different operation modes is presented and analyzed in detail. For space-heating-only mode, the daily-averaged heat pump COP varied from 2.6 to 3.3, while the system COP ranged from 2.1 to 2.7. For water-heating-only mode, the DX-SAHP system could supply 200 l or 1000 l hot water daily, with the final temperature of about 50 °C, under various weather conditions in Shanghai, China. For space-cooling-only mode, the compressor operates only at night to take advantage of a utility’s off-peak electrical rates by chilling water in the thermal storage tank for the daytime air-conditioning. It shows that, the multi-functional DX-SAHP system could guarantee a long-term operation under very different weather conditions and relatively low running cost for a whole year.     

Exergetic analysis of transcritical CO2 residential air-conditioning system based on experimental data

The experimental system for the transcritical CO₂ residential air-conditioning with an internal heat exchanger was built. The effects of working conditions on system performance were experimentally studied. Based on the experimental dada, the second law analysis on the transcritical CO₂ system was performed. The effects of working conditions on the total exergetic efficiency of the system were investigated. The results show that in the studied parameter ranges, the exergetic efficiency of the system increases with the increases of gas cooler side air inlet temperature, gas cooler side air inlet velocity and evaporating temperature. And it will decrease with the increases of evaporator side air inlet temperature and velocity. Then, a complete exergetic analysis was performed for the entire CO₂ transcritical cycle including compressor, gas cooler, expansion valve, evaporator and internal heat exchanger under different working conditions. The average exergy loss in gas cooler is the highest one under all working conditions which is about 30.7% of the total exergy loss in the system. The second is the average exergy loss in expansion valve which is about 24.9% of the total exergy loss, followed by the exergy losses in evaporator and compressor, which account for 21.9% and 19.5%, respectively. The exergy loss in internal heat exchanger is the lowest one which is only about 3.0%. So in the optimization design of the transcritical CO₂ residential air-conditioning system more attentions should be paid to the gas cooler and expansion valve.     

Defrosting method adopting dual hot gas bypass for an air-to-air heat pump

A novel dual hot gas bypass defrosting (DHBD) method is developed to remove frost from the outside heat exchanger (HEX) of an air-to-air heat pump. The proposed method adopts two bypass lines of hot gas from the compressor: one is connected to the inlet of the outdoor HEX, and the other is connected to the outlet of the exchanger. We compare the dynamic performance and defrosting time of the conventional reverse cycle defrosting (RCD), hot gas bypass cycle defrosting (HGBD), and DHBD methods using a medium air-to-air 16 kW heat pump. The salient feature of the DHBD method is its ability to prevent a sharp decrease in the compressor outlet temperature at the melting frost stage after the HGBD process begins. Due to the additional bypass, the DHBD method sustained a higher compressor outlet pressure and reduced the defrosting time by 36% compared to the HGBD method. Compared to RCD, the defrosting time was comparable (126%); however, the amenity characteristics of the DHBD method were superior than those of the RCD method. The proposed DHBD method can overcome the main disadvantages of the RCD and HGBD methods, and showed excellent performance for an air-to-air heat pump in a defrosting operation.