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今用一种数学模型预测燃烧室,经部分隔热的涡轮增压柴油机的性能。本文阐述了该模型,着重于它的热传递图景和燃烧室表面温度的预测。首先,探讨隔热所致性能效率改善程度,燃烧室表面温度和排气能量之间的相互关系。显然,隔热所致气缸表面的高温引起容积效率下降。然而,由于增大了排气能量,这种下降依靠提高涡轮增压器增压压力而得到了补偿。本文论述了减少气缸盖、活塞和气缸套等总热损失的意义及其对发动机效率的影响。我们探讨了多种涡轮-复合系统以后发现:在很宽的车用转速和载荷范围内,大多数系统都不能匹配,除非使用变几何的涡轮或者是变速比的齿轮箱(它在部分载荷时保持复合系统运行)。再者,明显的总性能效益仅能用很高效率的涡轮机才能获得。低载荷下朗肯尾循环比不变几何涡轮-复合机更为有效,但是它们的正常效率受到高冷凝器温度的限制,并且它们要装在紧凑的欧洲卡车内是困难的。结论是:涡轮复合式绝热发动机在燃油消耗率方面的最大改善是20%(不包括风扇和水泵的节省量)。然而,如果发动机制造接近于这种隔热程度,必须有极其新的设计构思。而重新设计常规型式发动机,可显著降低冷却系统的要求,且热效率收益尚可。
A mathematical model is used to predict the performance of a combustion chamber, partially insulated turbocharged diesel engine. This article describes the model, focusing on its heat transfer map and the prediction of the combustion chamber surface temperature. First, the relationship between the improvement in performance efficiency due to insulation and the combustion chamber surface temperature and the exhaust energy is explored. Obviously, the high temperature on the cylinder surface caused by insulation causes the volumetric efficiency to drop. However, due to increased exhaust energy, this drop is compensated by increasing turbocharger boost pressure. This article discusses the implications of reducing overall heat losses such as cylinder heads, pistons and cylinder liners and their impact on engine efficiency. We explored a variety of turbo-compound systems and later discovered that most systems can not be matched over a wide range of vehicle speeds and loads unless a variable-geometry turbine or variable speed gearbox is used (it is partially loaded Keep compound system up and running). Again, the obvious overall performance benefit can only be achieved with highly efficient turbines. Low-load Rankine tail cycles are more efficient than invariable geometry turbine-laminators, but their normal efficiency is limited by the high condenser temperatures and they are difficult to pack in compact European trucks. The conclusion is that the biggest improvement in fuel consumption for turbo compound adiabatic engines is 20% (not including fan and pump savings). However, if engine construction approaches this level of insulation, there must be extremely new design concepts. The redesign of the conventional type of engine, can significantly reduce the cooling system requirements, and thermal efficiency benefits are acceptable.