车辆装备发动机冷却系电偶腐蚀行为研究

铸铁、铸铝和黄铜是车辆装备发动机冷却系常用的3种金属材料，在冷却水中对其进行极化曲线测试。得出各自自腐蚀电位并进行比较可知，铜正于铸铁和铸铝，表明冷却系中电偶腐蚀存在的可能性，再进行电偶电流测试，以研究冷却系电偶金属材料在冷却液中的腐蚀行为。探讨电偶腐蚀的特点与规律，为冷却系的腐蚀防护提供理论依据。

风扇在汽车发动机冷却系中的匹配与优选方法

通过将现有的风扇性能数据编程建库，应用相似理论和计算机程序，探讨了风扇在汽车发动机冷却系中的匹配与优选方法，并给出了应用实例。

任务驱动教学法在“汽车发动机冷却系故障诊断与排除”教学中的实践

汽车发动机的构造和维修这门课程具有较高的技能操作要求,其中较难的操作项目是发动机故障诊断和排除,本文论述了汽车发动机冷却系故障诊断与排除教学过程中利用任务驱动教学法,总结教学经验,提高汽车发动机冷却系故障诊断与排除教学的质量。

发动机冷却系常见故障的分析与处置

冷却系的功用是对发动机进行适当冷却,强制地将受热零件吸收的部分热量及时散发出去,保证发动机在最适宜的温度(一般为80~95℃)状态下工作,不致因过热而导致柴油机功率下降或机件损坏。如果冷却系统工作出现了异常,不能对高温零件进行及时的降温,这些零件可能因受热膨胀而破坏正常的配合间隙,或因润滑油高温失效而发生卡死、擦伤损坏等。因此,在发动机使用过程中,我们要注意观察冷却系统的工作是否正常,发现异常现象要及时查找原因,排除故障,以确保发动机正常工作。

捷达、高尔夫乘用车发动机冷却系的维修

冷却系对发动机的正常工作和延长发动机的使用寿命有重要作用。捷达、高尔夫等有代表性的乘用车其发动机均采用强制循环式水冷系,且采用自动补偿封闭式散热器。与早期的水冷系比较,其结构比较复杂,但是,这种水冷系不需要经常添加冷却液(冷却液的蒸发损失少),并且具有较高的散热效果(冷却液的沸点较高)。

汽车防冻液

汽车发动机冷却系采用水作为热交换介质。冬季我国北方大多采用防冻液作为热交换介质。近年来,生产防冻液的厂家不少,但性能单一,很难适应汽车工业发展的需要。

A New Unsteady Fluid Network Approach to Simulate the Characteristics of the Air System of a Gas Turbine System

In this paper, a novel unsteady fluid network simulation method to compute the air system of jet engine was coded to predict the characteristics of pressure, temperature and mass flow rate of the flow and the temperature of the solid in the gas turbine engine. The fluid and solid areas are divided into the network comprised of branches and nodes, and the method solves transient mass, energy conservation equations at each node and momentum conservation equation at each branch by a newly deduced numerical method. With this method, to simulate complicated fluid and solid system in short time becomes possible. To verify the code developed, it has been applied to simulate a gas turbine model against the widely used commercial software Flowmaster. And the comparisons show that the two are in good agreement. Then the verified program is applied to the prediction of the characteristics of a designed turbine disk and air-cooling system associated to it, and useful information is obtained.

Numerical investigation of radial inflow in the impeller rear cavity with and without baffle

In typical small engines, the cooling air for high pressure turbine （HPT） in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn radially inwards through the impeller rear cavity. The centripetal air flow creates a strong vortex because of high inlet tangential velocity, which results in significant pressure losses. This not only restricts the mass flow rate, but also reduces the cooling air pressure for down-stream hot com- ponents. The present study is devoted to the numerical modeling of flow in an impeller rear cavity. The simulations are can＇ied out with axisymmetric and 3-D sector models for various inlet swirl ratio ,80 （0-0.6）, turbulent flow parameter 2-r （0.028-0,280） with and without baffle. The baffle is a thin plate attached to the stationary wall of the cavity, and is proved to be useful in re- ducing the pressure loss of centripetal flow in the impeller rear cavity in the current paper. Further flow details in impeller rear cavity with and without baffle are displayed using CFD techniques. The CFD results show that for any specified geometry, the outlet pressure coefficient of impeller rear cavity with or without baffle depends only on the inlet swirl ratio and turbulent flow parameter. Meanwhile, the outlet pressure coefficient of the cavity with baffle is indeed smaller than that of cavity without baffle, especially for the cases with high inlet swirl ratio. The suppression of the effect of centrifugal pumping and the mixing beween the main air which is downstream of the baffle and the recirculating flow of the vortex in the stationary cavity, which are caused by the use of baffle, are the underlying reasons that lead to the reduction of outlet pressure loss.

Regenerative Cooling for Liquid Rocket Engines

Heat transfer in the thrust chamber is of great importance in the design of liquid propellant rocketengines. Regenerative cooling is an advanced method which can ensure not only the proper runningbut also higher performance of a rocket engine. The theoretical model is complicated, it relates to fluiddynamics, heat transfer, combustion, etc... In this papers a regenerative cooling model is presented.Effects such as radiation, heat transfer to environment, variable thermal properties and coking areincluded in the model. This model can be applied to all kinds of liquid propellant rocket engines aswell as similar constructions. The modularized computer code is completed in the work.

Analysis of an electricity-cooling cogeneration system for waste heat recovery of gaseous fuel engines

Waste heat recovery(WHR)is one of the most useful ways to improve the efficiency of internal combustion engines,and an electricity-cooling cogeneration system(ECCS)based on Rankin-absorption refrigeration combined cycle for the WHR of gaseous fuel engines is proposed in the paper.This system can avoid wasting the heat in condenser so that the efficiency of the whole WHR system improves,but the condensing temperature of Rankin cycle(RC)must increase in order to use absorption refrigeration system,which leads to the decrease of RC output power.Therefore,the relationship between the profit of absorption refrigeration system and the loss of RC in this combined system is the mainly studied content in the paper.Because the energy quality of cooling and electricity are different,cooling power in absorption refrigeration is converted to corresponding electrical power consumed by electric cooling system,which is defined as equivalent electrical power.With this method,the effects of some important operation parameters on the performance of the ECCS are researched,and the equivalent efficiency,exergy efficiency and primary energy rate are compared in the paper.

Overall optimization of Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines considering the cooling power consumption

The Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines has been regarded as a promising tech- nique to reduce fuel consumption. Its heat dissipation in the condensation process, however, should be take：l away in time, which is an energy-consuming process. A fan-assisted auxiliary water-cooling system is employed in this paper. Results at 1300 r/min and 50% load indicate that the cooling pump and cooling fan together consume 7.66% of the recovered power. What＇s worse for the heavy load, cooling accessories may deplete of all the recovered power of the Rankine cycle system. Af- terwards, effects of the condensing pressure and water feeding temperature are investigated, based on which a cooling power consumption model is established. Finally, an overall efficiency optimization is conducted to balance the electric power gener- ation and cooling power consumption, taking condensing pressure, pressure ratio and exhaust bypass valve as major variables. The research suggests that the priority is to increase condensing pressure and open exhaust bypass valve appropriately at high speed and heavy load to reduce the cooling power consumption, while at low speed and light load, a lower condensing pressure is favored and the exhaust bypass valve should be closed making the waste heat recovered as much as possible. Within the sub-critical region, a larger pressure ratio yields higher overall efficiency improvement at medium-low speed and load. But the effects taper off at high speed and heavy load. For a given vehicular heavy-duty diesel engine, the overall e：＇ficiency can be improved by 3.37% at 1300 r/min and 25% load using a Rankine cycle system to recover exhaust energy. The improvement becomes smaller as engine speed and load become higher.

System Design and Analysis of Hydrocarbon Scramjet with Regeneration Cooling and Expansion Cycle

A new expansion cycle scheme of the scramjet engine system including a hydrocarbon-fuel-based(kerosene)regenerative cooling system and supercritical/cracking kerosene-based turbo-pump was proposed in this paper.In this cycle scbeme,the supercritical/cracking kerosene with high pressure and high temperature is formed through the cooling channel.And then,in order to make better use of the high energy of the supercritical/cracking fuel,the supercritical/cracking kerosene fuel was used to drive the turbo-pump to obtain a high pressure of the cold kerosene fuel at the entrance of the cooling channel.In the end,the supercritical/cracking kerosene from the turbine exit is injected into the scramjet combustor.Such supercritical/cracking kerosene fuel can decrease the fuel-air mixing length and increase the combustion efficiency,due to the gas state and low molecular weight of the cracking fuel.In order to ignite the cold kerosene in the start-up stage,the ethylene-assisted ignition subsystem was applied.In the present paper,operating modes and characteristics of the expansion cycle system are first described.And then,the overall design of the system and the characterisitics of the start-up process are analyzed numerically to investigate effects of the system parameters on the scramjet start-up performance.The results show that the expansion cycle system proposed in this paper can work well under typical conditions.The research work in this paper can help to make a solid foundation for the research on the coupling characteristics between the dynamics and thermodynamics of the scramjet expansion cycle system.