汽油机爆震强度的分析

分析了汽油机缸内气体爆震燃烧压力的频率特性并推导了爆震压力共振频率计算公式。研究表明：在爆震工况下，缸内压力在高频域中有几个共振峰，峰的大小表明了汽油机爆震强度。汽油机的表面振动在这些共振频率峰处也出现相应振动峰。表面振动峰与缸力压内峰值近似成正比。汽油机表面振动峰值可作为爆震强度的评价指标，该结论在ＣＡ１１０２汽油机上得到了证实。     

Stirling cycle cooling engine with two-phase,two-component working fluid

A Stirling cycle cooling engine operates on a closed regenerative thermodynamic cycle with compression and expansion of the working fluid at different temperature levels. Conventional engines use a gaseous working fluid but a significant improvement in refrigerating capacity may be gained with a two-phase, two-component working fluid. This consists of a gaseous carrier and a component which is liquid in the cold region and gaseous in the ambient temperature spaces with the phase change occurring during the regenerative process. This causes an increase in the range of the pressure excursion of the working fluid and consequently increases the refrigerating capacity with no penalties in terms of size, weight, or cost. The degree of improvement depends on the particular design and operating conditions of the engine. The effects of variation of some of these parameters are explored.     

Influence of the preheating of a working medium on the thermodynamic efficiency of pulse-detonation-engine propulsion modules

A theoretical substantiation of calculation of the thermodynamic cycle of engines with detonation fuel combustion, which is realized in propulsion modules of pulse detonation engines, has been given. A system of equations for calculation of the parameters of detonation combustion waves under different conditions of their excitation has been obtained. On their basis, investigations of the influence of different factors on the parameters of detonation combustion waves and accordingly on the cycle work, thermal efficiency, and specific parameters of pulse detonation engines have been performed. It has been established that the loss due to the irreversibility of the process of heat supply in detonation combustion waves is much lower when propulsion modules are installed in the heated-gas flow. It has been shown that the temperature of the working medium fed to propulsion modules is the determining factor influencing the thermodynamic efficiency of the detonation-fuel-combustion cycle. Generalized characteristics in the form of one-parameter dependences of the specific parameters of propulsion modules of pulse detonation engines on the temperature of the working medium fed to them have been obtained.     

微乳化乙醇柴油热物性计算与分析

车用清洁型微乳化油是内燃机的理想代用燃料之一．微乳化油热物性参数难以计算,从而影响在内燃机上对它的定量计算研究．以微乳化乙醇柴油为例,用经验公式计算其蒸发焓、生成焓、液体比热容、导热率和微乳化油蒸气的扩散系数,分析了温度和压力以及不同溶醇量对热物性参数的影响规律,为微乳化油热物性参数的计算提供一种工程方法．结果表明：随着温度的增加,微乳化乙醇柴油蒸发焓、导热率降低,定压比热容和微乳化油蒸气扩散系数增加;随着压力增加,微乳化油蒸气扩散系数降低;随着混合燃料中乙醇含量的增加,定压比热容和混合气扩散系数均增大,蒸发焓减小;乙醇含量对混合燃料导热率的影响与燃料温度有关,在一定温度下乙醇含量效应发生逆转;微乳化乙醇柴油中乙醇含量增加有利于燃料蒸发．     

空气源热泵自然冷源过冷制热性能实验研究

冬季我国北方室外环境蕴含大量天然冷源,热力学分析表明热泵工质过冷释放的热量可以在蒸发器的等温吸热过程中获得补偿。为了研究大气自然冷源对热泵制热性能的影响,增设室外过冷器,搭建利用自然冷源过冷的空气源热泵实验装置。实验结果表明：当室外环境温度大于0 ℃,冷凝温度小于45 ℃的条件下,自然冷源过冷对热泵制热量与制热COP影响均较小,系统制热量维持在6.22 ~ 6.70 kW,制热COP维持在3.03,压缩机排气温度维持在103 ℃以下;当室外环境温度小于 -10 ℃,冷凝温度大于50 ℃时,随过冷度的增加,压缩机功率增加、排气温度显著增高,系统制热量呈先缓慢增加后减小趋势,制热COP降至2.3。基于上述研究提出一种空气源热泵过冷融霜新型除霜方式,融霜同时不停止制热。     

小型汽油机进气系统声学性能优化设计

随着车辆舒适性要求的不断提高,对发动机进气系统的声学性能要求也越来越高.以声学理论为基础,建立小型汽油机滤清器的参数化数值模型.首先,通过小型汽油机直管管口噪声模拟,获得进气系统插入损失的目标值;其次,结合插入损失的目标值确定小型汽油机进气系统传递损失的目标值,应用滤清器的数值模型优化滤清器的结构参数.小型汽油机进气系统声学性能优化设计方法具有很高的工程应用价值,并为滤清器的参数化设计提供了理论依据.     

Knock characteristics of dual-fuel combustion in diesel engines using natural gas as primary fuel

This paper investigates the combustion knock characteristics of diesel engines running on natural gas using pilot injection as means of initiating combustion. The diesel engines knock under normal operating conditions but the knock referred to in this paper is an objectionable one. In the dual-fuel combustion process we have the ignition stage followed by the combustion stage. There are three types of knock: diesel knock, spark knock and knock due to secondary ignition delay of the primary fuel (erratic knock). Several factors have been noted to feature in defining knock characteristics of dual-fuel engines that include ignition delay, pilot quantity, engine load and speed, turbulence and gas flow rate     

闭式跨临界CO2热泵烘干系统最优工况研究

目的 对跨临界CO2热泵驱动的闭式干燥系统展开理论研究,得到CO2闭式热泵中最优工况的计算方法和原理。方法 通过建立CO2循环与空气循环热力学耦合的数学模型,计算干燥循环中空气的温度、焓值、相对湿度、含湿量,以及跨临界CO2热泵系统中工质的温度、压力、焓值等参数。通过调整冷凝干燥后空气温度,以热泵烘干系统的COP为评价依据,探究空气循环与CO2热泵循环的耦合机理。结果 获得了CO2循环系统最优排气压力随闭式空气循环系统在不同工况下的变化规律,并基于所建立的计算程序,获得了典型工艺参数下的热泵系统的热力学参数,为关键设备(风机、换热器、压缩机等)选型及系统控制方法提供了理论依据。结论 研究表明,在CO2热泵冷却器出口状态为临界状态时,系统的COP达到最优。     

汽油机控制参数的电控与测试研究

以MCS－8098单片机作为中央控制器,设计了一种电控发动机基本控制参数测试装置,利用该装置对汽油机的空燃比和点火提前角等控制参数进行了实际测试。应用测试获得的数据对发动机进行实际控制时,取得了比较满意的效果。     

A High-Efficiency Two-Stroke Engine Concept: The Boosted Uniflow Scavenged Direct-Injection Gasoline (BUSDIG) Engine with Air Hybrid Operation

A novel two-stroke boosted uniflow scavenged direct-injection gasoline (BUSDIG) engine has been proposed and designed in order to achieve aggressive engine downsizing and down-speeding for higher engine performance and efficiency. In this paper, the design and development of the BUSDIG engine are outlined discussed and the key findings are summarized to highlight the progress of the development of the proposed two-stroke BUSDIG engine. In order to maximize the scavenging performance and produce sufficient in-cylinder flow motions for the fuel/air mixing process in the two-stroke BUSDIG engine, the engine bore/stroke ratio, intake scavenge port angles, and intake plenum design were optimized by three-dimensional (3D) computational fluid dynamics (CFD) simulations. The effects of the opening profiles of the scavenge ports and exhaust valves on controlling the scavenging process were also investigated. In order to achieve optimal in-cylinder fuel stratification, the mixture-formation processes by different injection strategies were studied by using CFD simulations with a calibrated Reitz–Diwakar breakup model. Based on the optimal design of the BUSDIG engine, one-dimensional (1D) engine simulations were performed in Ricardo WAVE. The results showed that a maximum brake thermal efficiency of 47.2% can be achieved for the two-stroke BUSDIG engine with lean combustion and water injection. A peak brake toque of 379 N·m and a peak brake power density of 112 kW·L⁻¹ were achieved at 1600 and 4000 r·min⁻¹, respectively, in the BUSDIG engine with the stoichiometric condition.     

Simultaneous temperature and exhaust-gas recirculation-measurements in a homogeneous charge-compression ignition engine by use of pure rotational coherent anti-Stokes Raman spectroscopy

Pure rotational coherent anti-Stokes Raman spectroscopy was used for the simultaneous determination of temperature and exhaust-gas recirculation in a homogeneous charge-compression ignition engine. Measurements were performed in a production-line four-cylinder gasoline engine operated with standard gasoline fuel through small optical line-of-sight accesses. The homogenization process of fresh intake air with recirculated exhaust gas was observed during the compression stroke, and the effect of charge temperature on combustion timing is shown. Single-pulse coherent anti-Stokes Raman spectroscopy spectra could not only be taken in the compression stroke but also during the gas-exchange cycle and after combustion. Consequently, the used method has been shown to be suitable for the investigation of two of the key parameters for self-ignition, namely temperature and charge composition.     

交变流动热机的介观热力循环理论--第一部分 制冷机回热器的介观热力循环模型及分析

提出了交变流动热机的介观热力循环理论,系统地分析交变流动热机中关键部件的热力过程.本部分将基于物理上直观的拉格朗日法,首先分析回热器内具有代表性微团的热力过程,进而阐述回热器整体在整机中的热力工作过程和功能.分析表明,回热器中的不同气体微团及相应的固体工作介质更像一个个配合精巧、工作在不同温度水平、功能完整的微型热机.对于制冷机来说,回热器内的微团通过接力作用,一步步将低温热源的热量向高温泵送,并最终排向环境温度热源.     

变温热源不可逆布雷顿制冷循环制冷率和制冷系数优化

用有限时间热力学方法分析变温热源不可逆简单布雷顿制冷循环的特性,分别以制冷率和制冷系数为优化目标,优化了循环中换热器的热导分配以及工质和热源间的热容率匹配,并采用数值计算分析了压比、换热器总热导、压缩机和膨胀机效率、工质热容率等参数对最优制冷率和制冷系数的影响特点.所得结果对工程制冷系统设计有一定的指导意义.     

Experimental investigation of solar driven desiccant air conditioning system based on silica gel coated heat exchanger

A silica gel coated heat exchanger based air conditioning system driven by the evacuated tube solar water heater has been experimentally investigated. The system has been operated for two different modes namely cooling with dehumidification mode and heating with humidification mode in summer and winter season respectively. The system performance is analyzed in terms of regeneration rate, dehumidification rate and thermal coefficient of performance (COP_th). Experimental results demonstrated that, for cooling and dehumidification mode, the process air is cooled by an average temperature of 8.5 °C. A better dehumidification rate can be achieved by using pre-cooling before dehumidification process. Post-cooling after dehumidification process is found to be advantageous for cooling capacity and COP_th. For heating with humidification mode, the process air is heated by an average temperature of 13.3 °C with an average increment in humidity ratio of 1.9 g/kg. It is found that the average COP_th of the system is 0.45 and 0.87 for cooling and heating mode respectively.     

Knocking Detection of a Gasoline Engine by Utilizing an Optical Fiber with Specific Refractive-index Composition

Abnormal combustion of a gasoline engine is often accompanied by a sharp metallic noise called knocking. A recently proposed method of in-cylinder pressure measurement is applied to detect the knocking, where the bending power loss of a single-mode fiber with specific refractive-index composition is utilized. The high-frequency response of a prototype sensor is obtained with a small structure to utilize the bending mechanism that is installed into an engine head gasket. Knocking signals are detected in a wide range of trace- to heavy-knock conditions.     

Advances in biodiesel fuel for application in compression ignition engines

The importance of biodiesel as a renewable and economically viable alternative to fossil diesel for applications in compression ignition (CI) engines has led to intense research in the field over the last two decades. This is predominantly due to the depletion of petroleum resources, and increasing awareness of environmental and health impacts from the combustion of fossil diesel. Biodiesel is favoured over other biofuels because of its compatibility with present day CI engines, with no further adjustments required to the core engine configurations when used in either neat or blended forms. Studies conducted to date on various CI engines fuelled with varying biodiesel types and blends under numerous test cycles have shown that key tailpipe pollutants, such as carbon monoxide, aromatics, sulphur oxides, unburnt hydrocarbons and particulate matters are potentially reduced. The effects of biodiesel on nitrogen oxides emission require further tests and validations. The improvement in most of the diesel emission species comes with a trade-off in a reduction of brake power and an increase in fuel consumption. Biodiesel’s lubricating properties are generally better than those of its fossil diesel counterpart, which result in an increased engine life. These substantial differences in engine-out responses between biodiesel and fossil diesel combustion are mainly attributed to the physical properties and chemical composition of the fuels. Despite the purported benefits, widespread adoption of biodiesel usage in CI engines is hindered by outstanding technical challenges, such as low temperature inoperability, storage instabilities, in-cylinder carbon deposition and fuel line corrosion. It is imperative that these issues are addressed appropriately to ensure that long-term biodiesel usage in CI engines does not negatively affect the overall engine durability. Possible solutions range from biodiesel fuel reformulation through feedstock choice and production technique, to the simple addition of fuel additives. This calls for a more strategic and comprehensive research effort internationally, with an overarching approach for co-ordinating sustainable exploitation and utilisation of biodiesel. This review examines the combustion quality, exhaust emissions and tribological impacts of biodiesel on CI engines, with specific focus on the influence of biodiesel’s physico-chemical properties. Ongoing efforts in mitigating problems related to engine operations due to biodiesel usage are addressed. Present day biodiesel production methods and emerging trends are also identified, with specific focus on the conventional transesterification process wherein factors affecting its yield are discussed.     

分离式热管蓄冷空调释冷性能实验研究

本文设计了基于分离式热管换热的蓄冷空调系统,针对其释冷性能进行了因素实验和响应曲面实验研究。结果表明:分离式热管蓄冷空调释冷性能稳定,实验条件下最大制冷量可达5. 09 k W;制冷量随循环风量的增加而增加,而除湿量存在最佳除湿循环风量,最佳除湿循环风量约为620 m3/h,除湿量约为4. 32 kg/h;制冷量随环境温湿度的升高而增加;得到了不同工况下制冷量的回归方程,分析了不同影响因子对制冷量的影响规律,在循环风量较低的工况下,热管阀门对制冷量影响较弱,随着循环风量的增加,对制冷量影响增加。     

The effects of coating materials in spark ignition engine design

Ceramic coatings provide good thermal barrier properties for designers. In the design of adiabatic engines, reducing in-cylinder heat rejection requires very special thermal barrier coatings on the engine combustion chamber. Partially, thermal barrier coating (TBC) on the top surface of the piston in the annulus form is considered as a solution for unburned HC emission produced by incomplete combustion with respect to crevice volume after SI engines start (the three-way catalytic converter is not yet activated in the period of first 120 s). Because TBC on the top piston surface decreases the thermal conductivity and increases the unburned charge oxidation by increasing the temperature in the flame quenching area near the entrance of the crevice volume between the piston and liner during the compression and the early part of the expansion strokes.In this study, a steady-state thermal analysis was performed to evaluate the temperature gradients in the standard and two different partially stabilized ceramic coated pistons by using Abaqus© finite element (FE) software. A sharp increase in the temperature of the coated area of the piston was observed as a result of FE simulations. It is concluded that the annulus Y-PSZ coating may contribute better, as compared to Mg-PSZ, to decrease the cold start and steady state HC emissions without auto ignition, since the temperature in the area shows a local sharp increase.     

Thermal modeling of gas engine driven air to water heat pump systems in heating mode using genetic algorithm and Artificial Neural Network methods

The gas-engine driven air-to-water heat pump, type air conditioning system, is composed of two major thermodynamic cycles (including the vapor compression refrigeration cycle and the internal combustion gas engine cycle) as well as a refrigerant-water plate heat exchanger. The thermal modeling of gas engine driven air-to-water heat pump system with engine heat recovery heat exchangers was performed here for the heating mode of operation (in which it was required to model engine heat recovery heat exchanger). The modeling was performed using typical thermodynamic characteristics of system components, Artificial Neural Network and the multi-objective genetic algorithm optimization method. The comparison of modeling results with experimental ones showed average differences of 5.08%, 5.93%, 5.21%, 2.88% and 6.2% which shows acceptable agreement for operating pressure, gas engine fuel consumption, outlet water temperature, engine rotational speed, and system primary energy ratio.     

高效热致声发动机的新方案探索及其热力分析

讨论了热声发动机在驻波和行波两种不同工作状态下, 其声功率产生的临界温度梯度与流道尺寸和工作介质的关系, 提出了基于行波工作模式的热声发动机新方案。