An Outline Design of Zhou Engine & Its Comparisons

（Updated on 2020-11-19)

We are planning to design and manufacture a prototype of a turbocharged Zhou Engine. Its parameters and proofs are in the following.

This article is for widely discussion. Welcome comments. Welcomes send your opinions to [email protected] .

The catalog of this invention is in "About Zhou Engine".

§1. Overall Solution

For easily understanding the following, please first see “Turbocharged Zhou Engine” (https://www.dhirubhai.net/pulse/turbocharged-zhou-engine-jing-yuan-zhou ).

This turbocharged Zhou Engine, its fuel can be natural gas, liquefied petroleum gas (LPG) or gasoline. Its thermal efficiency will exceed 60%. Its power will be 165 kW.

In which, this Zhou Engine, the whole flow of its intake and exhaust has no pulsation. Its suction stroke length equals its exhaust stroke length. The air flows through compressor, cooling, and then flows inside its cylinders. Its uses spark plug for ignition.

For easy description, we use the following symbols in table 1, in the following expressions.

After calculation, we drew the pV diagram as fig.1, we drew the enthalpy flow diagram as fig.2, to realize the best matching among the turbine, the turbocharger and this Zhou Engine.

In fig.1 — Point A, suction the air, which is the working substance, the ambient temperature is 300K. Process A-B, the air is adiabatic compressed by the turbocharger. Process B-C, the air is cooling, the temperature down to 320K. Process C-F, is the compression stroke of this Zhou Engine inside its cylinders, is adiabatic compression. Process F-G, is the combustion process inside its cylinders, is constant volume combustion. Process G-I, is adiabatic expansion, is the expansion stroke, working. Process I-L-H, is adiabatic expansion, discharges the exhaust of this Zhou Engine, drives the turbine and the turbocharger. Point H, the exhaust flows into the atmosphere.

Note, point F, at the end of the compression stroke, the temperature of the working substance T=735.17K, which needs spark plug for ignition.

According to fig.1, this turbocharged Zhou Engine, its ideal thermal efficiency is 71%.

According to our experience, we choose, the mechanical efficiency of the turbine system (including the turbine and the turbocharger) equals 0.8, and the mechanical efficiency of the piston system (including this Zhou Engine) equals 0.9. According to fig.2, the volume flow rate of suction air F1=0.00310m^3*(1500 r/min)/0.4267=0.181(m^3/s)=0.214 kg/s, the estimated real thermal efficiency is 0.61. The output power of this Zhou Engine Wk=0.5826*F1*.9=0.0950MW=95.0kW, the output power of the turbine Wj= 0.4825*F1*.8=0.0700MW=70.0kW, the total output power 95.0+70.0=165 kW.

Here, this Zhou Engine, we select, barrel type, rated speed 1500 r/min, compression ratio 8, 6 pairs of pistons, bore 70 mm, suction stroke length 67 mm = exhaust stroke length 67 mm, displacement 3.10 L, the overall size is diameter 330 mm and length 720 mm. 

 While we start this turbocharged Zhou Engine, the turbine and the turbocharger is stopped. We start this Zhou Engine by a starter, just like start an Otto engine with 41.6 kW. After we have started this Zhou Engine, its exhaust then drive the turbine and the turbocharger, then this turbocharged Zhou Engine goes into the state of fig.2.

If this Zhou Engine works lonely (without turbine and turbocharger), seeing §5, its power is only 41.6 kW, its estimated real thermal efficiency is 0.35.

§2. The Exhaust Pressure Matching

The exhaust of this Zhou Engine passes through the catalytic exhaust purifier, drives the turbine, and then drives the turbocharger, seeing fig.2. There are 2 stages of adjustable vanes.

We use the adjustable vanes stage 1 to control and steady the pressure of the exhaust pipe of this Zhou Engine, to avoid the pulsation in the whole flow of the exhaust. We set a pressure sensor at point M, inside the exhaust pipe, near this Zhou Engine and before the catalytic exhaust purifier. According to the pressure waveform detected by the pressure sensor, we adjust the adjustable vanes stage 1 to keep the pressure equals that of the end of the expansion stroke.

Seeing fig.3, the pressure waveform has 3 types — a. no wave, this shows that the adjustable vanes stage 1 is at the optimal opening; b. up spike waveform, this shows that we ought to reduce the opening of the adjustable vanes stage 1, to raise the pressure of the exhaust pipe,till the spike small enough; c. down spike waveform, this shows that we ought to turn up the opening of the adjustable vanes stage 1, to decrease the pressure of the exhaust pipe,till the spike small enough.

We will create a circuit kit to fit the pressure sensor, to detect the pressure waveform inside the exhaust pipe, to drive a servo motor, to adjust the adjustable vanes stage 1.

The adjustable vane stage 2 is used to control and steady the turbocharger, to fit the working condition. Many variable geometry turbochargers (VGT) have adjustable vanes; we can choose one for this turbocharged Zhou Engine.

Question: who are willing to provide the turbine shown in fig.2? Design or customize.

§3. The intake and exhaust of this Zhou Engine

Each cylinder of a conventional IC engine has a clearance volume and contains residual gas, and the intake valve open period overlaps a part of the exhaust valve open period. If the last pressure of the exhaust stroke higher than the pressure of the intake gas, the intake gas will be limited, even be obstructed and then stop the engine running.

Whereas, each cylinder of a Zhou Engine has little clearance volume and contains few residual gas, and the intake valve open period does not overlap the exhaust valve open period. This Zhou Engine, its exhaust pressure does not affect its intake gas, thus, the turbine of fig.2 can make full use of its exhaust pressure to do work. Therefore, its intake p=0.2532 and no pulsation, its exhaust p=0.8612 and no pulsation, its exhaust does not affect its intake.

§4. The Feasibility of this Turbocharged Zhou Engine

Current, the researching on IC engines and gas turbines, are almost focusing on the extreme parameters of high pressure, high temperature and high speed, they have no big change on the principles and structures. Because the extreme parameters are too complicated and hard to understand, they usually cost a lot of funds and time. The researching usually looks like to fall into the quagmire of burning money and time-consuming. Whereas, the researching of Zhou Engine will avoid the quagmire, we will not join the competition of extreme parameters.

But, this researching on this turbocharged Zhou Engine, is based our discovery — the exhaust process of a conventional IC engine has an isenthalpic expansion, which consumes a lot of mechanical energy, please see “A Common Mistake in the Thermodynamics of IC Engines” (https://www.dhirubhai.net/pulse/common-mistake-thermodynamics-ic-engines-jing-yuan-zhou ). We need not to join the competition of extreme parameters above. This turbocharged Zhou Engine avoids the isenthalpic expansion, saves the mechanical energy, and huge increases the thermal efficiency, please compare the fig.4 with the fig.6, the fig.5 with the fig.7.

In this design, we only use conventional value of all parameters. This design is low cost, easier to realize, and has no technical barrier. As long as we pass the prototype test, we will have enough competitiveness in the market. In addition, a patent will protect this invention.

The following lists the key parameters of increasing thermal efficiency and power density.

1)Maximum working medium temperature or maximum combustion temperature of this Zhou Engine, is 2500 K (point G of fig.1). Currently, the maximum combustion temperature of an Otto engine reaches 2800 K. This shows that we can easily use the current technique to achieve the temperature of this Zhou Engine.

2)Maximum working pressure or peak cylinder pressure of this Zhou Engine, is 15.828MPa (point G of fig.1). Currently, the turbocharged diesel engine MTU1163-03, its peak cylinder pressure is 18MPa; the turbocharged diesel engine N55B30, its peak cylinder pressure is 20MPa. This shows that we can easily use the current technique to achieve the peak cylinder pressure of this Zhou Engine.

3)This Zhou Engine eliminates the pulsation of its whole exhaust flow, and its exhaust temperature is 1088.2 K (point I of fig.1), to drive the turbines. Currently, the inlet temperature of the hot end of a gas turbine usually is 1400 K. Therefore, we are easy to purchase or customize the turbine from the market for this turbocharged Zhou Engine.

4)Theoretically, a Zhou Engine breaks through the speed limits of a conventional IC engine, see “Zhou Engine vs. a conventional four-stroke engine” (https://www.dhirubhai.net/pulse/zhou-engine-vs-conventional-four-stroke-jing-yuan-zhou ). Here, we select that the speed of this Zhou Engine is same as the common speed of a conventional IC engine, 1500 r/min, to reduce the difficulty and avoid the risk.

§5. When this Zhou Engine is working Alone

When this Zhou Engine is working alone, or this Zhou Engine is working without the turbine and the turbocharger, its pV diagram shows in fig.4, and its enthalpy flow diagram shows in fig.5.

In fig.4 — Point C, suction the air, which is the working substance, the ambient temperature is 300K. Process C-F, is adiabatic compression, is the compression stroke of this Zhou Engine, inside its cylinders. Process F-G, is the combustion process inside its cylinders, is constant volume combustion. Process G-I, is adiabatic expansion, is the expansion stroke of this Zhou Engine, working. Process I-H, the exhaust of this Zhou Engine isenthalpic expands inside its exhaust pipe. Point H, the exhaust flows into the atmosphere.

According to fig.4, we have its ideal thermal efficiency is 0.39. We estimate that, its real thermal efficiency would be 0.35, and is close to the real thermal efficiency of a conventional Otto engine.

This Zhou Engine, its displacement is 3.10L, rated speed is 1500 r/min, and compression ratio is 8. Its air flow rate F1= 0.00310 m^3*(1500 r/min)=0.07739 m^3/s . We think its mechanical efficiency is 0.9, then its output power Wk=0.5977*F1*0.9=0.0416 MW=41.6 kW .

Note, the fig.4 is the same as the pV diagram of an Otto engine. However, the pV diagram of an Otto engine is commonly wrong of carelessly neglect the transport work, please see “A common mistake in textbook of physics” (https://www.dhirubhai.net/pulse/common-mistake-textbook-physics-jihua-zhou ). The fig.1 and fig.6, they have considered the transport work, which has completely been counteracted and not been shown.

§6. When this Zhou Engine Only Matching a Turbine

When this Engine only matching a turbine, their pV diagram shows in fig.6, their enthalpy flow diagram shows in fig.7.

In fig.6 — Point C, this Zhou Engine suction the air, which is the working substance, the ambient temperature is 300K. Process C-F, is adiabatic compression, is the compression stroke of this Zhou Engine, inside its cylinders. Process F-G, is the combustion process inside its cylinders, is constant volume combustion. Process G-I, is adiabatic expansion, is the expansion stroke, working. Process I-H, this Zhou Engine discharges its exhaust from its cylinder and drives a turbine, which continues the adiabatic expansion and works. Point H, the exhaust flows into the atmosphere.

According to fig.6, we have their ideal thermal efficiency is 0.65. We estimate that its real thermal efficiency is 0.56.

Seeing fig.7, according to the signal of the pressure sensor at the point M, we adjust the adjustable vanes inside the turbine, to realize the best matching.

This Zhou Engine, its displacement is 3.10L, rated speed is 1500 r/min, and compression ratio is 8. Their air flow rate F1= 0.00310 m^3*(1500 r/min)=0.07739 m^3/s . Their estimate total output power 0.5977*F1*0.9+0.3963*F1*.8= 0.06616 MW=66.2 kW.

Comparing fig.5 and fig.7, it is obvious that, that optimal matching this Zhou Engine with a turbine is very important and we can achieve. Because, the Zhou Engine has no pulsation in its whole exhaust flow, and the reasons are in §3.

In other words, Fig.7 shows, the residual pressure of the exhaust of this Zhou Engine being recycled by a turbine.

§7. The Further Thinking

If we pass the test of this turbocharged Zhou Engine, it will be a great technological advance, also a great progress in science. We will have confirmed and corrected the mistake, “A Common Mistake in the Thermodynamics of Otto Engines”. We will have further perfected the theory of engines.

Comparing the fig.2, fig.5 and fig.7, obviously, the turbocharging of a Zhou Engine is very important, and that raises the thermal efficiency and power density very much.

If we do finer design and manufacture of a Zhou Engine, its rated speed may excess 10000 r/min, and then its power density will be much higher.

If, raising the pressure ratio of the turbocharger, or adding cooling inter-stage, a turbocharged Zhou Engine will have far higher thermal efficiency and power density.

Purposely adjusting the “adjustable vanes stage 2” of the turbocharger in fig.2, to change the pressure ratio of the turbocharger, then we can change the compression ratio of this turbocharged Zhou Engine. This is the simplest way to realize variable compression ratio (VCR). Thus, this turbocharged Zhou Engine can work with high thermal efficiency in a wide range of the power.

Thanks Kenny Tao for discussion on this issue.

For more about this invention, please see "About Zhou Engine", especially the §2 of which.

Welcome comments and share. Welcomes send your opinion to me to [email protected].