Hydrogen Jet Ignition - a pragmatic approach to zero engine out emissions in future heavy duty vehicles

传统的重型内燃机使用液态或气态碳氢化合物燃料，燃料中只有0.35%的能量转化为有用的功。燃烧的副产品包括烟尘和氮氧化物，两者都对健康有害。现在，人们对零尾气排放的电动汽车给予了极大的关注。然而，最近的生命周期分析显示，以家用大小乘用车的现代柴油发动机的二氧化碳当量计算，它可能需要长达10年的时间才能实现收支平衡（其中相当大的二氧化碳与电池生产有关）。集成电路发动机的成本约为此类乘用车电动动力总成的资本成本的10%。卡车的前景令人震惊，特斯拉半挂车的电池成本高达数十万美元。燃料电池提供了另一种选择，但还不能维持所需的瞬时运行程度。我们提出了一个全新的解决方案，使用一种以氢为燃料的新型内燃机燃烧系统，能够将燃料中50%以上的能量转化为有用的功。燃烧系统是基于一个独立的氢气燃料的绝缘湍流预室。当以快速燃烧的氢气为燃料（即使在超稀薄条件下也是快速燃烧）时，该系统在所有条件下都可以实现氮氧化物和烟灰的零尾气排放。给出了燃烧系统的图解。反应射流可以增加火焰面积，从而在超贫燃料条件下快速燃烧。氢气既可以直接储存在船上，也可以从富含氢的载体（如液化合成燃料或氨）中进行转化，同时回收液化燃料的“冷能”，进一步提高发动机循环热效率。与燃料电池电动汽车相比，该系统可以在更短暂的驾驶条件下运行（这是燃料电池仍然存在的障碍之一）。目前在f1中使用的是更简单的预室，预室中没有单独的喷油器（这意味着预室和主室的加油速率不能独立优化，而这是超精益和高效运行的关键）。如果再加上废气热回收，我们相信整体动力系统的效率将达到55-60%，这与燃料电池的效率相比是可行的，而且成本要低得多。

Traditional heavy duty IC engines utilise liquid or gaseous hydrocarbon fuels, with only c.35% of the energy in the fuel converted in to useful work. The by-products of combustion include soot and NOx, both harmful to health. Significant attention is now being paid to zero tailpipe emission electric vehicles. However, recent life cycle analysis has shown it can take up to 10 years to break even in terms of equivalent CO2 to a modern diesel engine in a family sized passenger car (with considerable CO2 associated with battery production). The IC engine costs approximately 10% the capital cost of an electric powertrain for such a passenger car. In trucks the outlook is staggering, with battery costs of several hundreds of thousands of US dollars in the Tesla Semi. Fuel cells provide an alternative but cannot yet sustain the required degree of transient operation. We propose a radical new solution that involves the use of a new type of IC engine combustion system fuelled with hydrogen and capable of converting over 50% of the energy in the fuel in to useful work. The combustion system is based upon an insulated turbulent pre-chamber independently fuelled with hydrogen. When fuelled with fast burning hydrogen (fast even under ultra lean conditions) this system can result in zero tailpipe emissions of NOx and soot under all conditions. An illustration of the combustion system is shown. The reaction jets enable increased flame area and hence rapid combustion under ultra lean fuel conditions. The hydrogen can either be stored directly on-board or reformed from hydrogen-rich carriers, e.g. liquefied synthetic-fuels or ammonia, with the 'cold energy' of the liquefied fuel recaptured to further improve engine cycle thermal efficiency. Compared to fuel cell electric vehicles the system can be operated under more transient driving conditions (one of the remaining stumbling blocks to fuel cells). Simpler pre-chambers are currently used in Formula 1 without a separate fuel injector in the pre-chamber (meaning the fuelling rates in the pre and main chambers cannot be independently optimised, which is key to ultra lean and high efficiency operation). When coupled to exhaust heat recovery we believe an overall powertrain efficiency of 55-60% will be feasible, which is competitive with fuel cell efficiency for significantly lower cost.