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体或气态碳氢化合物燃料，燃料中只有约35%的能量转化为有用的功。燃烧的副产物包括烟尘和氮氧化物，这两种物质都对健康有害。目前，零尾气排放电动汽车正受到极大关注。然而，最近的生命周期分析表明，就相当于一辆家用乘用车的现代柴油发动机的二氧化碳当量而言，可能需要长达10年的时间才能实现收支平衡(与电池生产相关的大量二氧化碳)。内燃机发动机的成本大约是这种乘用车电动动力总成的10%。卡车的前景令人震惊，特斯拉Semi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。我们提出了一种全新的解决方案，其中包括使用一种新型的内燃机燃烧系统，该系统以氢为燃料，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燃室。当燃用快速燃烧的氢气时(即使在超稀薄的条件下也是快速的)，该系统在所有条件下都可以导致NOx和烟尘的零排放。给出了燃烧系统的图解。反应射流能够增加火焰面积，从而在超稀薄燃料条件下快速燃烧。氢可以直接储存在船上，也可以通过富含氢的载体(如液化合成燃料或氨)进行重整，并将液化燃料的冷能回收，以进一步提高发动机循环热效率。与燃料电池电动汽车相比，该系统可以在更多的瞬时驾驶条件下运行(这是燃料电池的剩余绊脚石之一)。一级方程式赛车目前使用更简单的预燃室，在预燃室中没有单独的燃油喷射器(这意味着预燃室和主燃室中的燃油率不能独立优化，这是超瘦和高效率运行的关键)。当与废热回收相结合时，我们相信总体动力总成效率达到55%-60%是可行的，这与燃料电池的效率具有竞争力，因为成本显著降低。

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.