Late Yuan Dynasty: I am the true emperor

Chapter 523 Dual-use nature

After arranging a position for Ye Chen in the Ministry of Industry and Commerce, Lu Jin told him to go back first. Then, he had the guards take away all the experimental equipment made in the glass workshop, and then took Tao Guangyi to a nearby firework workshop.

This pyrography workshop was originally intended to support the machining workshop, mainly responsible for forging iron parts or heat treating machined parts.

Of course, this pyrotechnic workshop also had another important task: to develop the steam engine.

When Lu Jin arrived, he saw a three-roll plate rolling machine weighing tens of thousands of kilograms, which was rolling the rolled steel plate into a cylindrical shape. After being rolled into a cylinder, it was sent to a drilling machine next to it, where dense holes were drilled along the edge of the steel plate. These holes were to be used to install rivets.

However, because there are no alloy steel cutting tools, drilling machines and various machine tools use high-carbon steel cutting tools made by carburizing. Although cutting ordinary cast iron and brass is not a problem, the wear of the cutting tools is too fast.

Take the twist drill used on this drilling machine, for example. It can only drill a dozen holes before the drill bit has to be replaced. Then the used drill bit is given to other craftsmen to be sharpened and reused. These tools are used as consumables. But there's nothing that can be done about it now.

Lu Jin immediately asked Tao Guangyi beside him, "How's the steam engine project going?"

Tao Guangyi immediately explained, “Your Majesty, we redesigned the official blueprints based on the model Your Majesty taught us. Then we made a scale model out of wood. After perfecting the design, we gradually replaced all the parts with metal parts one by one.”

"We have completed the cylinder and piston. The cylinder is made from a cast iron blank and then precision machined. Because the hydraulic boring machine technology used for making cannons is already mature, we did not encounter any difficulties in making this cylinder. It's just that the diameter is a bit larger. Oh, by the way, we are using a 350 mm cylinder diameter."

"The cylinder heads at both ends are bolted to the cylinder heads, and the joints are sealed with felt gaskets soaked in coal tar. The sealing effect is very good. We have done a sealing test, and at least there is no leakage."

"The piston plate is also made from a cast blank and then precision machined. The piston rod is forged and precision machined. There are no problems with these. The only difficulty is the piston ring made of ductile iron material that Your Majesty mentioned. We have been unable to figure it out. The piston rings we make have almost no elasticity. Even if we manage to fit them in, the wear and noise are also very high."

"Therefore, I made the final decision to have them replace the sealing ring with a brass one, and the effect is quite good. Ah, this is the sample. Would Your Majesty like to take it out and take a look?"

"No need to take it out, just let it spin a bit and see," Lu Jin said, looking at the huge piston connecting rod and the flywheel that weighed a thousand pounds.

"Yes."

Tao Guangyi agreed and immediately waved his hand. Several craftsmen came over and laboriously started turning the flywheel.

The massive cast iron flywheel, 1.6 meters in diameter, gradually accelerated under the rotation of several craftsmen and began to slowly rotate. The piston rod connected to the flywheel also began to reciprocate under the drive of the flywheel, which was equivalent to doing the work of the steam engine in reverse.

Lu Jin listened carefully for a while and found that the sound of the piston rubbing against the cylinder wall was not loud, and it sounded quite smooth. He nodded in satisfaction and asked, "Was lubricating oil added inside?"

"Yes, I added castor oil. His Majesty said that castor oil can be used as a high-temperature lubricant. This is the oil can. As long as the machine is running, the oil can will continuously drip oil onto the connecting rod through a cotton thread to lubricate the internal parts and reduce friction. Moreover, the piston was already coated with a lot of lubricant when it was installed." Tao Guangyi immediately pointed to an oil can next to the cylinder and introduced it.

Lu Jin leaned closer to take a look and then said with satisfaction, "Not bad, I can tell you've put a lot of effort into it. The cylinder and piston, these two most important parts, are all fine. How's the boiler's progress?"

Tao Guangyi immediately pointed to an iron barrel placed in a corner not far away. The barrel was as big as a modern gasoline drum, dark and heavy, like a large water tank. It had lids at both ends, and six rows of small rivets were densely packed at the seams. At first glance, it had the feel of a 'multi-rivet steamed steel'.

"This is a prototype we made in advance, mainly used to test whether the riveting process meets the sealing requirements."

"The small boiler in front of us is made of five-millimeter-thick rolled wrought iron plate. All the seams are perforated. It is lined with five-millimeter-thick perforated iron strips. After the seams are joined with the lining plate, three rows of eight-millimeter-diameter rivets are used to rivet it in an alternating hot riveting process."

"According to the principle of thermal expansion and contraction, the rivet will naturally shrink after cooling, clamping the two iron plates tightly together to achieve an airtight effect. However, I was still not satisfied with this, so I asked a craftsman who was skilled in brazing to braze the joint with a lead-tin alloy, melting the lead-tin into the joint to increase the sealing effect. The final product looks like this."

Lu Jin nodded to himself upon hearing this. In fact, before unlocking the welding technology tree, riveting was the easiest sealing 'welding' process to achieve. Early ironclad warships, battleships, and other large iron ships were also manufactured using riveting technology. To achieve a watertight effect, all you had to do was use more rivets, make them closer together, and then arrange several rows of rivets in an alternating pattern, filling in any gaps. As long as you used enough rivets, it would be enough to achieve a certain sealing effect.

Of course, this technology doesn't mean that there's absolutely no water leakage. However, early steel ships were generally equipped with water pumps. As long as the seawater that leaked into the cabin was pumped out in time, the ship could continue to float and sail.

Steam boilers made using this technology, while unable to withstand high pressure, are perfectly adequate for low-pressure steam engines, comparable to those used by Watt. As for high-pressure steam engines, we can wait until we find rubber, manufacture gas hoses, and develop acetylene welding technology before making them.

Lu Jin then asked again, "Has this experimental subject undergone a pressure test?"

Tao Guangyi nodded immediately, then pointed to a wooden watchtower in the yard outside the workshop.

"We did it. We conducted the experiment under that wooden tower. Following His Majesty's previous lectures on hydraulic experiments, we built a watchtower here, placed the boiler underneath, connected it to bamboo pipes, and poured water into it from the top of the tower. We used the water pressure to test the boiler's sealing. Even after adding ten meters of height, we didn't see any leaks from the boiler itself. However, there was a lot of water leaking out at the connection between the bamboo pipes and the boiler."

"But I believe that, according to Your Majesty's requirements, a boiler of this size should be ready for use."

Lu Jin nodded again upon hearing this. This was an imitation of Pascal's barrel experiment. In order to prove the existence of water pressure, Pascal once conducted a similar experiment, in which he connected a water pipe to a wooden barrel and continuously poured water into it from a height, eventually causing the barrel to burst due to the water pressure.

Tao Guangyi and his colleagues adopted this method to test the pressure resistance of boilers, which was a reasonable, makeshift testing method in the absence of professional equipment.

Lu Jin then said, "Do you remember the technology generations I explained to you?"

"I remember His Majesty said in class that science and technology will grow and develop like people. Just like people of different ages, their knowledge and style of doing things will be very different. Science and technology are similar. At the beginning, they are like a toddler learning to walk. As they grow stronger, they will become more and more mature, until finally they are like a master butcher carving up an ox, doing it with ease."

"Therefore, based on the similarity of technologies at different stages, technologies using the same methods can be classified into one generation. When a new technology completely overwhelms the old technology, it can be regarded as the next generation of technology. This is called technological progress or technological iteration. The different development paths of the same technology can also be regarded as a technology tree."

Lu Jin nodded immediately and praised, "That's right, the steam engine in front of us is the same. What you've made now is just a first-generation steam engine that can barely function. If you were to make improvements to this steam engine and iterate its technology, do you know which direction you should strive for?"

"In my opinion, it should be that after mastering the welding technique Your Majesty mentioned, we can create a seamless boiler that will not leak at all, which will greatly increase efficiency." After saying this, Tao Guangyi looked at Lu Jin nervously, unsure if he was right.

Upon hearing this, Lu Jin shook his head. "Changing riveting to welding is merely an improvement in the process. You haven't grasped the fundamental aspect of improving airtightness, which is the real direction for progress."

Tao Guangyi was taken aback for a moment upon hearing this, but immediately realized, "Your Majesty means to increase the steam pressure?"

"That's right. The technological development direction of steam engines is to continuously increase steam pressure. But this is also an application of the three laws of physics and thermodynamics. Only by thoroughly understanding thermodynamics can you understand that it's simply a conversion of heat. And the improvement of steam engines is just to continuously improve the efficiency of heat conversion. "It's too early to talk about these things now. Let's talk about the steam engine in front of us. The development of steam engines should actually be divided into two lines: the working machine and the boiler. The purpose of the boiler is to improve the conversion of heat, while the purpose of the working machine is to better use the energy provided by the boiler to do work."

“Take boilers for example. They can be roughly divided into four generations. The first generation is like the one in front of us. A stove is built with bricks, and a steam boiler for boiling water is placed on top. Based on its structure, it can be seen as a simple ‘water on top and fire below’. However, only the bottom of the pot can be heated. Most of the heat generated by the coal is lost, so the utilization efficiency is obviously not high.”

Tao Guangyi nodded immediately upon hearing this.

"Therefore, the second-generation boiler should integrate the stove and the pot together, using a large cylinder as the pot and a small cylinder inside as the stove, and then filling the space between the inner and outer cylinders with water to form a 'water-encased fire' structure. In this way, almost all the heat emitted from the furnace can be absorbed by the water and heated into steam, thus improving the heat conversion efficiency."

"That's a great idea!" Tao Guangyi's eyes lit up immediately upon hearing this, but then he realized, "However, while this method is ingenious, it also places higher demands on the sealing process. If the internal fire tube is not sealed tightly enough, and the water from the outer layer seeps into the furnace, wouldn't that extinguish the furnace inside?"

"That's right. Otherwise, if I knew that the fire-tube boiler was more efficient, why would I have you make this kind of inefficient first-generation boiler? Isn't it because our current welding technology is not good enough?"

"I see!" Tao Guangyi exclaimed in sudden realization.

Lu Jin continued, "Once you are able to make the second-generation fire-tube boiler in the future, you can continue to develop it. It's just a matter of putting a fire tube inside a pot, turning it into two or three, increasing the number of fire tubes to improve the efficiency of steam generation. But such a boiler structure still has its drawbacks, because the flue gas after coal combustion also contains a lot of heat, but it is directly lost from the chimney."

"Therefore, the third-generation boiler, namely the flue-tube boiler, has the chimney also coiled into a winding tube and stuffed into the boiler, so that the last trace of heat remaining in the flue gas is also absorbed by water, and then the soot is sprayed out, thereby maximizing the efficiency of heat utilization."

"But this requires even higher processing technology. Not only must we be able to make seamless steel pipes that can withstand high pressure, but we also need to learn pipe expansion and welding techniques to prevent the chimney from leaking."

Upon hearing this, Tao Guangyi's eyes lit up, as if he had thought of something, and he said, "So the development of steam engine technology is actually in line with the development of firearms and cannons? If we can make seamless steel pipes that can withstand high pressure, wouldn't we be able to make cannons with a longer range, greater power, and lighter weight?"
"And the technology for casting cylinders is actually similar to that for casting cannons. The boring machine used for boring cylinders can also be used to produce large-caliber cannons?"

“That’s right. You’re very clever and can already apply what you’ve learned to other situations. In fact, it’s not just the steam engine; many technologies that seem to be for civilian use can be converted into military applications,” Lu Jin immediately praised.

"Actually, this is only the third generation of boilers. By the time the fourth generation of boilers is built, the guns and cannons of the same period will have developed to an unbelievable level."

Tao Guangyi, a firearms enthusiast, became even more excited upon hearing this and quickly asked, "Then what does Your Majesty think the fourth-generation boiler should have? If it has squeezed out the last bit of heat from the flue gas, how can it still improve the efficiency of heat utilization?"

“Of course.” Lu Jin nodded.

"By the fourth generation, the water-encased-fire structure was no longer sufficient. At this point, we should find a way to increase the contact area between water and flame. So we should reverse the process and use a 'fire-encased-water' structure. First, we would build a huge furnace, then we would coil out winding water pipes, and then place these water pipes in the furnace. We would then use fire to directly burn the water pipes, increasing the contact area between water and fire, thereby improving the steam generation efficiency. Therefore, the fourth generation should be called a 'water-tube boiler'."

"At the same time, the steam pressure generated by these four generations of boilers has gradually increased. The first generation can be called a low-pressure boiler, which can be used to drive working machines and serve as a power source for factories."
"Fire tube boilers are medium-pressure boilers, while smoke tube boilers are high-pressure boilers. These second and third generation boilers can already drive heavy vehicles weighing thousands of tons to speed across land, and can also drive warships like the Yuanwang, which can sail at sea without sails, relying only on steam engines."

"Water-tube boilers are ultra-high pressure boilers. With this fourth-generation boiler, only seven or eight units are needed to drive a steel warship that is twenty times larger than the Yuanwang, a hundred feet long, and weighs sixty to seventy thousand tons. It can travel at sea at twice the speed of the Yuanwang without wind power, like a mobile steel city on the sea."

Tao Guangyi was stunned and couldn't help but admire Lu Jin's imagination. However, he asked in confusion, "But Your Majesty, what does this fourth-generation boiler have to do with the development of guns and cannons?"

Lu Jin turned to look at him before saying, "I only talked about the generation and research and development direction of boilers, but didn't I say that working machines and boilers are two separate things? Your boilers have been developing, but haven't you been developing steam engines?"

"I see. But how should we classify the steam engine?" Tao Guangyi asked again.

"Whether it's a steam engine or a boiler, the ultimate goal is to improve the efficiency of heat energy utilization."

"When you develop medium and high pressure boilers, you will find a problem: even if the steam exhaust gas has already pushed the piston to do work once, it still contains a lot of heat. However, the heat in this steam has not been fully utilized and it is directly discharged, resulting in a waste of heat. So how should you improve it at this time?"

Inspired by the boiler, Tao Guangyi frowned slightly and thought for a moment before immediately saying, "Add another cylinder, and introduce the exhaust gas from the first cylinder into the second cylinder to continue working, squeezing out the last bit of heat from the steam?"

Lu Jin nodded. "That's right. This type of steam engine is called a double-expansion steam engine. It can use two cylinders or three cylinders, but this type of steam engine still has its limits. Generally, it reaches its limit when it develops to a triple-expansion steam engine. This type of steam engine is sufficient to match the second and third generation medium and high pressure boilers, but it is not enough for the fourth generation ultra-high pressure boilers. It cannot fully utilize ultra-high pressure steam. At this time, the structure of the steam engine must be changed. The combination of cylinder and piston is not enough."

"But if we don't use cylinders and pistons, what kind of structure should we use?" Tao Guangyi was a little confused for a moment, unable to think of any other structure that could be used to drive the machine to work.

Lu Jin then prompted, "Have you ever seen a revolving lantern?"

“I have seen it. In peaceful times, sometimes during the Lantern Festival, people would make revolving lanterns,” Tao Guangyi said immediately.

"Do you know how a carousel works?"

Tao Guangyi frowned and recalled for a moment, then his eyes lit up. "The hot air from the lamp rises and blows the impeller up to rotate? Your Majesty means to build a steam engine with this structure, using ultra-high pressure steam to drive the impeller?"

"That's right. This type of steam engine is the standard for ultra-high pressure steam. According to its structure, it should be called a steam turbine. Only in this way can the heat of ultra-high pressure steam be utilized as efficiently as possible."

"However, it is not easy to build such a steam turbine because ultra-high pressure steam is corrosive to ordinary steel, especially parts such as blades that are directly subjected to steam blowing. It is definitely not possible to make them with ordinary carbon steel, so corrosion-resistant stainless steel blades must be used."

"And when you can refine stainless steel, muskets made from the same steel will be able to withstand even more severe wear and tear, higher chamber pressure, and higher rate of fire. Just imagine, if each soldier's musket could fire dozens of bullets in a single breath, or hundreds or thousands of bullets per minute, then one person would have the firepower of a whole battalion. Wouldn't that be incredible?"

Tao Guangyi's mouth dropped open. This was truly unbelievable. He simply couldn't imagine how a musket could achieve a rate of fire of over a thousand rounds per minute. Even if the musket could handle it, loading still required human intervention. The most skilled musketeers in the army could only fire four or five rounds per minute.

So he immediately asked, "But Your Majesty, even if such a musket can withstand it, it still takes time to reload, how could a person possibly reload it that quickly?"

"This is what you'll be researching in the future. You're the Minister of the General Armaments Department, but don't be impatient. Technology is all interconnected. If you don't lay a solid foundation, you won't be able to climb very high, no matter how hard you try. For now, just follow the steps and get the things you can do done first."

"Yes! I understand."

(End of this chapter)