发动机测试

位于密歇根州的马斯基根工厂

对发动机中的零部件进行测试是发动机研发中不可缺少的一部分。 内部发动机测试可提供产品功能和质量方面的真实情况。

马勒集团拥有13个技术中心、8个发动机测试基地共92个试验台。 这些技术中心以及发动机测试实验室邻近汽车工业最重要的开发中心,可与当地客户进行密切合作。

发动机及其组件的开发和测试越来越分散化。 因此,各个发动机测试地点之间的透明度和交流必不可少。

马勒发动机测试地点通过全球数据库和工作平台进行联网。 这意味着可随时在本地使用技术数据,而且保证了信息和技术的定期交流。 在定期会议中对发动机测试、测量和分析方法的战略以及测试方案进行讨论和比较。

马勒发动机测试包括各种任务,这些任务基本上可分为六个领域。

  • 开发测量方法
    新的测量、测试和分析方法可提供新产品开发方面的重要信息。 在进行全球协调和本地开发之后,马勒集团将新方法在全球范围内推广。 这意味着这些新方法可在所有地点实施,为马勒和客户提供有价值的数据和事实。
  • 基础研究
    这包括编制并验证与特殊问题和主题领域相关的普遍适用措施的目录。
  • 新产品的发动机测试
    在将新产品推向客户应用前,它们必须满足高度的技术成熟度和功能性。 因此,我们在发动机测试中对新产品进行内部测试和验证。
  • 产品的发动机测试到系列产品发布
    在产品开发过程中,对现有产品进行修改,使其适合客户的规格,并在具体客户的发动机测试中进行测试。 功率单元部件(PCU,包括活塞、活塞环和气缸套)的整体测试对于评估各个部件之间的相互作用及彼此协调而言必不可少。
  • 故障排除
    系列生产产品的复杂性需要迅速的反应。 若出现现场故障,必须在发动机测试设施用适当的测试进行再现,从而可对潜在的补救措施进行测试。
  • 开发服务
    发动机测试能够基于经验和专业技术为客户提供各种支持,提供各种发动机测试作为开发服务。

发动机测试是开发任何产品的最终步骤之一。 必须在发动机实际运行状态下才能验证零部件的实际工作性能以及与其它零部件之间的潜在相互作用。 在进行发动机测试前,无法实施旨在获得下文所列主要开发目标的详细优化测量,也无法证明其有效性。

  • 功能性和零部件强度的验证
  • 油耗和油分离的优化
  • 防止油碳集聚和各种残留物的沉积
  • 零部件冷却和温度分布的优化
  • 声学和振动性能的优化
  • 流动系统的优化
  • 最大限度减少摩擦损失和零件磨损
  • 热力学和排放性质的分析
  • 运行图应用和数据库。

马勒发动机试验台可运行各种装置,包括小型两冲程发动机、汽油和柴油乘用车发动机到重型商用车发动机。 试验台的功率输出范围高达1200kW。

现代试验台自动化系统是目前最先进的技术,可全天候进行无监控的发动机运行。 用于规划测试顺序和快速更换系统的复杂物流工具缩短了试验台上的发动机准备时间,大幅提高了其利用率并避免了不必要的空载时间。

除了大量机械开发和功能试验台以及用于热力学和排放量分析的试验台,马勒还运行各种专业试验台,在这些测试台上可进行其它重要开发领域(如摩擦损失、声学和冷启动)。

机械开发和功能性试验台

所有发动机操作介质都通过试验台调节,在长期测试中进行机械开发、功能验证和组件强度测试。 主动试验台制动器允许带动发动机运转,因此也可对商用车发动机制动系统进行测试。

除了进行具体的马勒测试方案,可进行所有具体客户的测试(如热冲击试验)。

热力学试验台

除了用于机械开发和功能试验台的试验台调节系统,热力学试验台还配备了进气调节系统。 提供高压和低压转位系统和相应的分析工具进行热力学测试。 为了分析废气组件,除了典型的五组件分析外,还提供了FTIR(傅立叶变换红外光谱仪)系统。 此外,还使用大量测量仪器分析废气中的颗粒质量或颗粒数量。

Cold test bench

Cold test benches

The cold test bench allows the cold start behavior of the engine to be evaluated and diverse surface coatings to be tested with respect to damage due to cold start scuffing. The entire test bench, including the coolant, oil, and intake air temperatures, can be cooled down to –28°C.

Acoustic test bench

Acoustic test benches

Low-reflection test benches are used for extensive NVH (Noise, Vibration, Harshness) tests for optimizing the acoustic behavior of components, such as pistons, bearings, valve train components, and intake modules. Both structure-borne and airborne noise measurements can be taken. Defined test runs can precisely reproduce noise excitation on the test bench, allowing the objective comparison of potential remedial measures.

Friction power test bench for complete engines

Friction power test benches

An important contributing factor for reducing CO2 is the minimization of frictional losses in the engine. In addition to simulation and determining frictional coefficients outside of the engine, MAHLE uses several engine measurement methods for determining and minimizing frictional losses.

The friction forces of the pistons, piston rings, and cylinder group can be determined as a function of degrees of crank angle in a single-cylinder floating-liner engine, by measuring the axial forces acting on the cylinder liner.

With the friction power test bench for complete engines, MAHLE uses a tool that determines mean friction pressure operating maps using the indication method on a driven, live complete engine. A wide range of design parameter variations thus allows measures to be compared over the entire operating map. Using the mean friction pressure operating map, suitable simulation tools can be used to calculate CO2 emissions in customer-relevant driving cycles.

Customer engines can thus be optimized individually with respect to CO2 emissions in legally relevant driving cycles as well.

被穴蚀损坏的缸套冷却液表面

穴蚀

穴蚀,尤其对于潮湿环境下的大型商用车发动机的缸套,会形成缸套表面的蚀损,在长时间运转后会引起发动机失效。补救措施的效果通常需要通过耗时长久、代价高昂的耐久性测试来体现。

Micrograph of a cylinder liner damaged by cavitation

MAHLE has developed a complex measurement method and an analysis methodology that allow cavitation propensity to be diagnosed and analyzed.
The effectiveness of remedial measures can thus be demonstrated at a low cost and in a short time.

Stationary oil consumption characterization map

Oil consumption

In addition to conventional gravimetric methods, such as the weighing method or the volumetric method, or measuring the oil level in the pan to determine oil consumption, MAHLE also uses analytical chemical methods. Methods using tracers such as sulfur or tritium are also used, as are tracer-free analytical chemical methods.

Oil consumption in a dynamic test run

The use of mass spectrometry to determine oil consumption is such a tracer-free analytical chemical method that is gaining in significance. The method provides a great deal of information within a very short time. Static oil consumption characterization maps can thus be created within a few hours. Thanks to continuous measurement of oil concentration in the exhaust gas, it is possible to determine oil consumption in transient operating conditions. The responsiveness of the measurement system is fast enough to evaluate even highly dynamic oil consumption effects, such as rapid cycling of loads and speeds. Extracting the exhaust gas directly after the combustion chamber allows selective measurements to be made for each cylinder.

Extensive studies have produced catalogs of measures that can be used for targeted oil consumption optimization.

Piston temperature

For reliable piston service life calculations, it is absolutely necessary to determine the piston component temperature. Depending on the requirements, various measurement methods are used to assess component temperatures.

One fast, simple measurement method is the use of a templug (steel screws made of a defined alloy) to determine the piston temperature at a steady-state operating point. The residual hardness and application time of the templug can be used to calculate the maximum temperature of a component.

Passenger car piston subjected to NTC metrology

The measurement method known as NTC is used for higher requirements. Semiconductors known as NTCs are used as measuring sensors. Data is transferred contact-free, using inductive coupling, to an external data acquisition and analysis unit. A maximum of three measurement points can be applied to each piston.

For the highest requirements—i.e., for extensive measurements over the entire operating map, parameter variations, and transient measurements in customer-specific test runs—the system known as RTM (Real-time Telemetry Piston Temperature Measurement System) is used. In this case, component temperatures are measured by means of NiCr-Ni thermocouples. The analog voltage signal from the measurement sensors is modulated into a digital signal by a sensor signal amplifier mounted on the piston. Telemetry is used to transmit the modulated signal wirelessly to an external data acquisition and analysis unit. Up to seven measurement points can be attached to one piston.

Customers can use this real-time measurement method on site at MAHLE to design the combustion application so that the maximum permissible thermal loads for the component are not exceeded.

Passenger car piston with knock damage

Knocking

Knocking combustion faults in gasoline engines can lead to damage on the piston, or even to engine failure. Using a measurement and analysis method developed at MAHLE, each individual knocking event can be detected and quantified, while the knocking intensity is determined in real time. Comparing knock amplitudes and ignition angle allows conclusions to be drawn about knock controls, thus enabling optimization and verification of knock control systems.