Besides electrification of the powertrain, new synthetic alternative fuels with the potential to be produced from renewable sources come into focus. Methanol is the most elementary liquid synthetic fuel and no novelty for use in internal combustion engines. This article presents pathways to achieve high efficiency spark-ignition methanol combustion on a direct injection spark-ignition single-cylinder research engine with two different stroke-to-bore ratios (1.2 and 1.5) and a constant bore. In addition, two compression ratios (CRs) were investigated on each setup: CR = 10.8 using RON95 E10 gasoline fuel and a higher CR = 15 using neat methanol. In contrast to previous studies of stroke-to-bore ratio influences on SI combustion, this article aims at demonstrating how the advantages of a high stroke-to-bore ratio can be exploited by combining a long-stroke engine with increased compression ratios and methanol. The increased stroke enhances the tumble motion due to a higher piston speed and a larger compression volume which improves the mixture homogenization and combustion velocity. Moreover, the lower surface/volume ratio results in a reduced heat transfer. When using RON95E10 gasoline fuel and CR = 10.8, an efficiency gain of up to 1.6% could be achieved with the long-stroke compared to the short-stroke especially at lower engine loads. With methanol and CR = 15, an efficiency gain of up to 1.6% could be achieved with the long-stroke setup compared to the short-stroke engine. Subsequently, lean burn conditions were experimentally investigated with methanol and CR = 15. The longer stroke allowed the lean burn limit to be extended from λ = 1.9 to λ = 2.0 with an efficiency gain of up to 2.2%. A maximum indicated efficiency of 47.4% could be achieved at λ = 1.9 with methanol on the long-stroke engine with CR = 15.

除了动力系统的电气化，具有由可再生能源生产的潜力的新型合成替代燃料也成为关注焦点。甲醇是最基本的液体合成燃料，用于内燃机并不新鲜。本文介绍了在具有两种不同冲程缸径比（1.2 和 1.5）和恒定缸径的直喷式火花点火单缸研究发动机上实现高效火花点火甲醇燃烧的途径。此外，对每种设置研究了两种压缩比 (CR)：使用 RON95 E10 汽油燃料时 CR = 10.8，使用纯甲醇时更高的 CR = 15。与之前对冲程缸径比对 SI 燃烧影响的研究相比，本文旨在展示如何通过将长冲程发动机与增加的压缩比和甲醇相结合来利用高冲程缸径比的优势。由于更高的活塞速度和更大的压缩体积，增加的冲程增强了滚流运动，从而改善了混合物的均匀化和燃烧速度。此外，较低的表面积/体积比导致传热减少。当使用 RON95E10 汽油燃料且 CR = 10.8 时，与短行程相比，长行程可实现高达 1.6% 的效率增益，尤其是在较低的发动机负载下。在甲醇和 CR = 15 的情况下，与短冲程发动机相比，长冲程设置可以实现高达 1.6% 的效率增益。随后，使用甲醇和 CR = 15 对稀薄燃烧条件进行了实验研究。更长的冲程允许稀燃极限从 λ = 1.9 扩展到 λ = 2.0，效率增益高达 2.2%。在 λ = 1.9 时，在 CR = 15 的长冲程发动机上使用甲醇可实现 47.4% 的最大指示效率。