What is it about?

The painted goose-and-fish lamp, a national treasure in China, is one representative bronze oil lamp in the Han dynasty that demonstrates both artistic and technological beauty. It has been claimed to be the earliest eco-friendly lamp that can mitigate indoor air pollution. The complete lamp is assembled from four dismountable components: the lamp tray, the lamp shade, the hollow body of the goose, and the head of the goose with a long neck on one side and a fish on the other side that are hollow as well. It is widely believed that when the lamp was used for lighting 2000 years ago, the goose belly was half-filled with water and the long neck served as a duct for the smoke generated by burning oil. Rather than polluting the indoor air, the smoke flowed into the belly through the neck and could be absorbed by the water. This claim together with the explanation can be identified in numerous reports on newspapers and museum websites, which sounds reasonable and has been taken for granted by most people. However, no one has ever scientifically clarified the mechanisms and further quantified the effectiveness of the design, specifically providing answers to two critical questions: (a) how can smoke flow into the goose belly that is below the flame? and (b) how effective this eco-design is? We, as chemical engineers with expertise in multi-physics modeling and simulation, decided to decode the riddle in this ancient lamp by resorting to in silico experiments and theories of transport phenomena. It was found that the secret for the downward flow of smoke in the lamp lies in the ingenious ventilation design of the lamp. More than 2000 years ago, the designer creatively took advantage of an unnoticeable gap between the lamp tray and the goose belly as a 2nd opening to harness natural ventilation in the lamp. This gap, although very small, allows the inflow air from the opening of the shade together with smoke particles flow downward into the goose belly through the long neck, then flow over the water surface and further get out of the lamp from the gap. The establishment of this route allows smoke particles to be absorbed by the water. Under the conditions we investigated, a lamp with a larger gap and a smaller opening offers a better protection. The maximum protection efficiency can reach around 20%.

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Why is it important?

Disclosing mechanisms. This work developed a generic multi-physics model and associated analysis methods for the investigation of protection efficiency of almost all anti-pollution bronze lamps in the Han Dynasty, including ox-shaped, phoenix-shaped, and stove-shaped lamps and the lamp of Changxin Palace. We revealed the anti-pollution mechanisms shared by all those lamps. Motivating sustainable designs. The lamp is a cleverly-designed natural ventilation system, whose ventilation rate can be adjusted as needed. It may inspire the design of optimized natural ventilation systems with many applications, including sustainable buildings, health-care settings. In addition to harnessing natural ventilation for air flow control and hence particle trajectory control, the lamp takes advantage of water for smoke particle absorption to mitigate indoor air pollution. This synergistic strategy to use both wind and water for air pollution control may inspire rational design of cost-effective removal technologies for particulate matter emissions that can be used in homes, restaurants, party rooms, and smoking rooms, etc. Moreover, the design concept imparted by ancient Chinese craftsmen to this 2000-year-old artifact will motivate designers today to practice sustainable design of multifunctional products featuring both artistic and technological beauty.

Perspectives

We are excited to discover the underlying mechanism for the environmental protection function of this ancient bronze lamp, which has never been scientifically explained before. A fine millimeter-scale gap between the lamp tray and the goose body can boost the protection efficiency by more than 200 times. What a surprising and exciting finding! Furthermore, after realizing that the gap should be an intrinsic feature of the multi-component design, we are amazed by the ancient Chinese craftsmen who are capable of harnessing natural ventilation for air pollution control with an ingenious design 2000 years ago. 20% protection efficiency is not high, implementing environmental protection features in lamp design, however, represents a breakthrough innovation (going from zero to one). We, thus, are pleased and eager to share with the world our findings. We, as chemical engineers, are excited to be able to contribute to the study of cultural heritage. Thanks to the curiosity of Prof. Xiao Dong Chen, whose museum visit years ago led to the initiation of this project. Curiosity is indeed the forerunner of discovery. One unique outcome of this work is the cultivation of a middle school student’s interests in Science and Engineering through participation in this interesting project. Flora Lanxin Xiao at Overseas Chinese Academy of Chiway Suzhou contributed to this work by creating a color painting of the lamp in her spare time. She earns an image credit in PNAS. Really hope she can actively take part in scientific research in the near future. Moreover, I am expecting this work to be a good example to demonstrate what can chemical engineers do and attract motivated secondary school students to choose chemical engineering as their future career. Based on this work, Flora and I together produced a 5-min short video to explain vividly how can the lamp mitigate indoor air pollution. We tried hard to tell the story at a level understandable to even primary and middle school students. Hope you will find it interesting and would like to share our video with your kids : ) I have posted the science communication video on my research website (see resources) or you can directly click the link below. Please enjoy watching the video http://web.suda.edu.cn/_upload/article/videos/9f/4e/ac406b284c04acd1ea43626af83d/c7de090d-2b08-4c27-b70f-7b9e8e67769a.mp4

Dr. Jie Xiao
Soochow University

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This page is a summary of: Uncovering eco-friendly design in the ancient bronze goose-and-fish lamp: an unnoticeable gap boosts ventilation, Proceedings of the National Academy of Sciences, August 2022, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2202037119.
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