The advantage the constant-volume combustion type gas turbine engine

In summary, the conversation discusses the constant volume combustion engine and its advantages compared to the constant pressure combustion engine. The speaker hopes to utilize and develop the advantages of the constant volume combustion engine, such as easy ignition, quick burning, and high gas pressure, in order to increase the efficiency of gas turbine engines. They propose a new motion and structure for the constant volume combustion gas turbine engine and explain the potential for closed or semi-closed combustion in a certain space. The speaker also mentions the use of a compressor and fuel mixing to further increase efficiency. They hope to compare the efficiency of the new engine with the current one and welcome any comments or feedback.
  • #1
qumf
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We all know the constant volume combustion engine acts as a kind of internal combustion engine that is used in the car and truck extremely widely. The cycle is called Otto cycle. I also heard the constant volume combustion gas turbine engine was proposed many years ago and developed a few ones, and soon replaced by constant pressure combustion type. The reason is work frequency and the energy efficiency is low; the engine is rather heavy. But the type of gas turbine engine was made many years ago, so it was restricted by the process and technology at that time.

Right now I hope to utilize or develop the advantage the constant-volume combustion type: easy to ignite and easy to get the higher gas pressure.furthly inovate its the motion and structure, at last not only on the aspect of energy efficiency, but also the weight to compete the current gas turbine engine.
Here I start the topic that we discuss to design a new motion and structure for the constant volume combustion gas turbine engine that can avoid the weakness I just mentioned.
 
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  • #2
To increase the efficiency of engine(including gas turbine engine ) is a genaral trend, as well as engineers' dream. I hope to apply the constant volume combustion type to gas turbine engine again, totally change the old structure and work courses on this type of combustion gas turbine to get higher efficiency than current gas turbine engine.
 
  • #3
This section I explain the advantage of this type of combustion and how to realize briefly.I hope readers to comment it.
-- easy to ignite : The gas under this combustion is static or the flow speed is very low.by this character the gas is easy to ignite. In current jet engine, people do a lot of work to maintain the combustion because the gas flow too quickly in that section.
-- burning quickly: I did not mention it in the previous post because this advantage need a few condition. If the gas before combustion is already mixed with fuel at proper concentration, the gas can finish combustion extremely quickly, just cost a few milliseconds. The concentration and the pressure of gas before combustion is related to the work performance and safety. The character is very useful to keep high frequency work cycle and smooth work,.
-- easy to get the high gas pressure: If the gas burns in a closed space, the gas presure will be high definately; If the combustion can finish very quickly, the space is not closed but semi-closed, we still can get high pressure gas after combustion. Normally high presure means high energy efficiency if anything else is same.Though by this way the pressure will be lower a little , the energy efficiency does not change much. We can utilize the solution.
 
  • #4
I listed the advantages of the constant-volume combustion type for turbine engine, then I will explain how to realize them.
in order to realize the closed combution or semi-closed space combustion in a certain space,in order to the gas can flow into and out the space in other time. the space need have two doors for input and output for the space at both ends.for high frequency the two doors must adopt rotation to open and close the space.
One door is at the opening of input of the space(chamber), another is at the opening of output.We can choose the angle between of them to control input and output, including closed or semi-closed combustion .for example the combustion course in completely closed space, the combustion is the closed combustion, if the front door is closed, the back door is opening but the combution has not finished, the combustion is the semi-closed combustion.
in order to ensure high frequency and reduce the energy loss, I hope each time the old gas after combustion runs out off the chamber by the negative pressure functions. it can suck the fresh gas into the chamber from other end subsequently. The negative pressure is caused by the inertia of the burned gas run out off the chamber .It is possible if we choose the right occasion to open the front door and design proper structure for the burned gas out off the chamber to cause a desired pressure inside the chamber.
 
  • #5
in order that the engine can work steady and outlet energy can be stable,in order that the two doors for the chamber can rotate continuously and steady,I design several chambers arranged in a circle,at least 6 pairs. thus they cooperate each other, such as the gas in one pair rushs out off the chambers, other pairs are in other courses, such as inlet gas or combustion.The chambers in symmetrical position is in the same course. Though the engine has a energy efficency only by the closed combustion in chambers, in order to increase the efficiency, in front of the chambers, I set the compressor to press the air.(later I will prove the point by the theory formula of the Thermal cycling.)in order to the gas can burn immeidately, before it enters the chambers, I have to make it mixed with fuel uniform. The fuel shall be added into air in the rear section of compressor, or a specific place only for fuel mixed into air before chambers.Two main factors are concerns for the course: the level and uniform of diffuse and the time spent from diffuse to enter the chambers for the mixed gas.
 
  • #6
I ever said,
Though the engine has a energy efficency only by the closed combustion in chambers, in order to increase the efficiency, in front of the chambers, I set the compressor to press the air.(later I will prove the point by the theory formula of the Thermal cycling.)

please read the attached to prove the point. your any comment will be welcome.
 

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  • #7
I can also compare the efficiency on two types of turbine engine by formula .
One is the new one I propose, the other one is the current one.
Pls read the attached figureEstimate the theoretic efficiency; compare the two types of engines: the current engine and I proposed.
Firstly I state some premises:
1. Because the efficiency of the current compressor and turbine in current turbo-generator is very high, the below calculation ignore the energy loss in them.
2. In below analyses I assume that the portion's efficiencies are same if they have the similar function component. Meanwhile I ignore some small loss during courses.

I set a sample example with data to explain, I assume the pressures are same before combustion in the two type engines.
for the current jet: efficiency=1-1/{W^[(k-1)/k]} ( ^N means the Nth power)
W: the pressure rise rate in compressor or blower; I set: W=10, k=1.4, the theoretical efficiency of the current jet is 48.2%.
As to the new jet: efficiency=1-k*[u^(1/k)-1]/(u-1)/{w^[(k-1)/k]}
W is increase rate of gas pressure by blower. W=10; here U is the increase rate of pressure by combustion, here U=4.5;I input the data, you can see the theoretical efficiency of this closed combustion jet engine is 60%
The efficiency of the new type engine is higher than the current one by 25%.
I try to explain why the new type of engine has more efficiency from another aspect, compared with current jet engine, the new engine uses up the same amount mechanical work and chemical energy but gets higher-pressure gas. The gas can make more work if its pressure is higher. So the new type engine has more efficiency.
The new engine can get higher-pressure gas because the gas pressure can increase further by the closed combustion course besides by the compressor that also is used in current jet engine.

b the way, pay attention, my contant-volume type turbine engine is different from the other contant-volume type engines.their thermal cycles are different basically.
 

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  • #8
I have introduced the courses of the chambers, you can find the gas is intermittent to flow into one certain chamber.intermitent flow has many disadvantages. such as on energy loss, safety aspect and force load.in order to gas can flow stably and continously in front of chambers as possible as I can,I have to make the flow rotate, Thus I setthe branch pipes in front of the chambers, it is a pairs of the branch pipes(or a space has similar function) that are corresponding to the chambers while the gas enter. The branch pipes rotate with the front door. The branch pipes are short in order to reduce the energy loss.
the branch pipes do not cost much energy. The mixure gas before chambers always flows in high speed, Thus the gas is hard to burn, even though it has the trend, it has entered the chambers when it burns actually.
before the inlet brach pipes, there is big pipe after compresser.

so we encounter similar issue for gas out off the chambers, for a certain chamber, outflow is intetmitent; for whole chambers, outflow is alternately, I hope the final gas current become stable on speed and pressure comparatively. It is beneficial to work for gas by mechanism way, we can get higher efficiency and reliability. So I install one branch pipe corresponding to one chambers, the back door is set between branch pipes and chambers. the door does rotate. the branch pipes are fixed. on their other end the branch pipes converge into one pipe.By the branch pipes and a short period of time the gases expand, pass branch pipes and converge later, as well as a space works as a buffer storage which is after the branch pipes conjunction point , we get the target.
By this structure,the gas in very high speed in the branch pipes can cause negative pressure inside other branch pipes, so it has suck function to cause gas exchange (fresh gas enter and burnt gas flow out the chambers)in the other chambers.
 
  • #9
firstly, I correct two sentences in the last post in order to explain more accurate.
"So I install one branch pipe corresponding to one chambers, the back door is set between branch pipes and chambers. the door does rotate. the branch pipes are fixed" ---corrected to "So I install one branch pipe corresponding to each chambers, the back door is set between branch pipes and chambers. the door does rotate. the branch pipes are static and mounted"

I have stated the principle of gas flow in side the engine , so i can draw the figue of gas condition in each process ,( including at each position in the engine).
The figure 3 shows the gas pressure at different courses (in different places), it is rough, and the exact details will is rather complicated. the figure just shows main portion of the flow. Please pay attention, there is a red horizontal line inside the figure, it shows that the pressure at two places have some relation. against the relation much, the engine can't work orderly.
 

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  • #10
You assume that the benefits from the constant volume combustion offset the extra mechanical complexity required. That may be questionable.
Just the rotating branch pipes and combustion chambers with front and back doors robust enough to resist deflagration of an air fuel mixture represent major engineering challenges, not to mention the likely resonance issues arising from an intermittent blast of hot gas to spin the turbine.
There is need for novel designs to push the gas turbine closer to the 100:1 compression engine and this concept may be a possible path towards that goal. However, a conventional axisymmetric compressor, combustor, turbine design such as laid out here may not be the solution.
 
  • #11
Thank your reply,etudiant
of course some of what you said are right , any new device has advantage and disadvantage. it usually depends on the position you stand on.
you said the branch pipes rotating, it is not accurate, the input branch pipe is very short and simple though it rotate; the outlet branch pipes are long and they are mounted.
I can not undertand your last sentence "push the gas turbine closer to the 100:1 compression engine ", can you explain the sentence more detailed?
 
  • #12
I have to compensate a little for the upper post.

the outlet branch pipes are mounted and static.

because each time the combustion last a very short time, so the combustion type can be the constant volume combustion type though the back door is open during most time of combustion. It is beneficial for the back door to bear the force.
for the front door , it could be strong because it is assembled with other things, such as input branch pipes. because it does rotate, the main force it bears is comparable stable. That is good.
 
  • #13
qumf said:
Thank your reply,etudiant
of course some of what you said are right , any new device has advantage and disadvantage. it usually depends on the position you stand on.
you said the branch pipes rotating, it is not accurate, the input branch pipe is very short and simple though it rotate; the outlet branch pipes are long and they are mounted.
I can not undertand your last sentence "push the gas turbine closer to the 100:1 compression engine ", can you explain the sentence more detailed?

Current technology turbines have pressure ratios of 20-30 to 1, they compress the air that much before the combustor. A higher pressure ratio such as 100 to 1 would allow a smaller and more efficient unit, but it also becomes more difficult to design an effective turbine to turn a 100x larger compressor.
A sketch of your concept would be helpful, as the word pictures are not as easily grasped.
 
  • #14
though i have mentioned key portion for the function when I introduce the main work courses. I still need to state the whole stucture of the engine.
pls study the figure 1.

The left one is the section view per axial, it show almost all main parts.
Another two pictures show the main parts: the front door and back door of the combustion chambers. two doors control and regulate works to complete combustion one by one. Anyone of combustion chambers sometimes sucks mixture gas; sometimes it the combustion happens inside it; sometimes gas exhausts from it. So the chamber sometimes is sealed by the two doors; sometimes it is open on both ends; sometimes it is open on one end. So the door has openings(slots) in it. The two doors rotate at same speed and co-operate each other.
At any time there is at least a pair of chambers in the same work course that are in the in symmetrical position.
As to the amount of chambers, I draw 4 couples here, actually it will be more. at least 6 pairs. It depends on the utilization rate of space; their strength; stable work and other factors.
There is a transmission( gas box) from turbine to the two doors, I set it because the two speeds do not match, I need to reduce speed a lot from turbine to the doors. the transmission unit will not ocuppy much space.
There is blower or compressor in front of the chambers. There will be also branch pipes in front of the chambers to input gas but they are very short so that they do not appear in the figure.
The branch pipe, turbine install behind the chambers. after a certain length of branch pipes, these branch pipes merges into one pipe. the turbine should be intalled within the converged pipe.

Later I will repeat or summarize the work courses of the engine.
 

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  • #15
Now I state the work procedure.

Let me introduce the new type of engine's work procedure: The first step of procedure is that the blower/compressor suck air and increase the pressure to a proper level; spray fuel into air afterwards or at the latter half of the compression; then through a certain length of pipe and a rotary short passage the gas enter the combustion chambers, the rotary short passage is eequivalent to the front door of the chambers. Meanwhile the burnt gas run out off the chambers. When the fresh gas occupies the nearly whole space of the chambers, the front door and back door begin to close. After the doors almost close, the inside mixture gas get ignited, the internal pressure increase rapidly, the combustion last only a few milliseconds and finished, then the back door open; the gas rushes out of chambers and into the branch pipes. thus the chambers begin to suck fresh gas and start the next cycle.
The chambers are arranged in a circle. There are at least a couple of chambers under a same course. This couple is on the symmetric position. Each chamber works per the sequence I describe upper. Because the front door and back door rotate, the courses change in turn on each chamber corresponding to the rotation.
The branch pipes are arranged in a circle. The gas flow into the branch pipes which position are symmetric. Later the currents merge and flow inside the general pipe. A turbine is placed afterwards, thus the gas strikes and drives the turbine which gets motion for the front blower/compressor, the rest kinetic energy of the gas is used to push the engine itself forward.
Inside the pipe/passage in front of the chambers, the flow is continuous.
The gas spouts out off chambers alternatively, (the spout is intermittent for a certain chamber), but the gases merge in one pipe and flow continuously at last. All the actions repeat with a very high frequency. It provides a consistent push force on the whole engine.

For each time of exchange gas inside chambers, the gases flow inside chambers are mainly driven by the negative pressure caused by high-speed current in outlet branch pipes.

Because the combustion in each time can finish within tiny little time, it is not necessary that chambers are closed completely at both sides, then we start ignition as far as the volume of combustion is almost constant.
If we analyze the principle of each course carefully, we can know how much time each course spends, we can distribute the proper percentage of space on the two doors corresponding to each course in a cycle in order to the engine can get very high work frequency. So the flow in the new engine will not be smaller than it in the current engine.even bigger than it. The flow is a important performance index for jet engine.
 
  • #16
I set the compressor/blower before the combustion potion for this kind of jet engine, besides its advantage I have said, such as high efficiency, It has other advantages, by the compressor/blower the engine can work under different work condition as current turbojet , so it has the obvious advantage compare with some other new type jet, such as Ramjet engine
 
  • #17
Hi gumf,
I still have trouble understanding how this translates into better performance.
We have rotating combustion chambers, but you also say the doors don't need to be closed completely at both sides. I envision sort of a six shooter like set of combustion chambers, spinning around their common axis, with an area blanked off by the doors and then as the chamber turns it released the trapped combustion gas into the exhaust stream.
One challenge I see are that the combustion chamber gets a real pressure surge as the fuel burns in a confined space, so it gets heavy. Another is that the chamber does not get much cooling, it takes in very hot compressed air and that is then further heated by the internal combustion. The cooling will be complicated on a moving chamber.
The more efficient combustion cycle you propose will have to more than offset the headwinds these and other engineering issues it creates. It is not a slam dunk, imho.
 
  • #18
That combustion at constant volume is more efficient should be clear, but the whole question is how to achieve this in a turbine, since nobody got convincing results.

Your design with doors front and aft is the first option people think of. More refined attempts were made without success. In particular, you could have a look at the throughput possible with doors. Because is means stopping the flow, people had arrived to let it oscilate instead, and use air's inertia to achieve the constant volume during a detonation.
 
  • #19
to etudiant
thank for your reply.
I correct you a little. the chambers do not rotate. the doors at the both sides do rotate.
you can not say " the doors don't need to be closed completely at both sides". It need or not depands on expriment. But i think at the beginning of combustion, the space can not completedly closed.
you also express you worry about something: heavy and heat. You can get result by search the topic to get my articles in other website. the chambers are arranged in a circle is relative to solve the issues. I also will explain my solution here later.
 
  • #20
to Enthalpy:

though I will explain the feasibility of this kind of engine later in this web, now you also can search the topic to get my composition on other website.
Here i say a few words.
the chambers exhausts gas in turn , and afterwads through a special pipes system to get a steady output at last.

I know for a certain chamber, the input gas is intermittent. so I set the input pipe rotating (with front door), the input gas flow continuously. thus throughput can be bigger than you thought.
 
  • #21
to etudiant and Enthalpy:
for example, you can find my article in website http://forum.keypublishing.com/ , then choose section: Modern Military Aviation ,then search " The jet propulsion with closed combustion type" ( Last post 10th October 2012 by qumf )

I also heard there are a few institutes developed the new jet engine to utilize the advantage of the constant volume combustion type in their laboratory. So far there are still some limits to launch in market.

One of the big differences between mine to theirs that I didn’t mention before: I set two doors at the ends of the combustion portion to realize the exchange of gas. The main function is to separate the gases (fresh and burnt gas) easily, then lead to series of benefit, such as increase the gas pressure higher, easy to control the flow and regulate the process, adjust the combustion condition
I learn the point from the internal combustion engines
 
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  • #22


I have to admit that the idea of a constant volume combustion gas turbine is an intriguing one. And it's one I have thought of on several occasions myself. Unlike this particular design utilizing a rotary valve, my idea was basically the same as the one mentioned with a rotating combustion chamber similar to the chamber on a six shooter (which slides by ports that allow gasses to enter and leave). However, although this sort of engine would seem to hold promise in terms of improving the efficiency of the standard Brayton Cycle turbine, it's not without its downfalls.

One of the WONDERFUL things about gas turbines is the inherent reliability of current designs. They are a wonderfully simple engine with few moving parts. Size and weight are low for the power produced. And flow is steady. So vibrations that could possibly cause cyclic fatigue are minimal. All of these factors lead to a engine that is rugged, reliable, and just plain works. When you add things like rotating chambers and/or rotary valves, you increase size and weight, and suddenly increase the failure points manyfold. In the case of a rotating chamber, you need a way to both seal the chamber against flat surfaces and keep it cool. With rotating valves, you need a design that will seal as well. And you will need to use materials as well as a design that will be able to withstand REALLY high temperatures without deformation. Furthermore, in ANY constant volume turbine, airflow through the engine will inevitably be unsteady to a greater or lesser degree. This will require an overall more robust compressor and turbine design which can handle cyclic loads without suffering from fatigue damage. And finally, with unsteady flow, noise could be a concern.

Of course, if these issues could be dealt with, then a constant volume combustor has the potential to increase turbine efficiency (and reduce fuel consumption). But it might also be helpful to look at other ways the efficiency of a gas turbine could be improved without such drastic changes that could lead to lower reliability and increased mechanical complexity. Such improvements as finding materials for turbine blades that can withstand higher temperatures (although not easy in itself) might ultimately be more practical in the end.
 
  • #23


to StorminMatt:

I know the constant-volume combustion type is very easy to cause some problem. my target is avoid these weakness. I hope you study the structure of my engine again. I also hope search my feasibility report from internet. I have mentioned the website before and you can find it easily. I would like to send you the report from my E-mail [Personal e-mail address removed by moderator] if you need.
I also anaylise the feasiblity here later.
I have considered many years all what you are concerned. I can not throw the idea away easily since it has a big advatage.
 
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  • #24


then I reply to some of your concerns. The detailed can be searched by E-mail.
Firstly (many years ago) I ever thought of rotating chambers. at last I gave up the idea.
It seems it need only one outlet pipe. Really the pressure of the gas out off the chamber is variable. so one outlet pipe is not enough. The structure is still very complicated.
the mass of chamber is much bigger than two doors; rotating the chambers cost more energy.
Then I gave up the idea.
 
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  • #25


You ever mentioned, the size and weight is bigger on the new type than the constant pressure combustion type. You should agree, only for chamber, the size and weight is bigger, the new chamber can increase the pressure. in the current engine this part of pressure will be produced by the the part of compressor. We all know the compressor is very heavy because it has many blades and strong hubs. comparatively the chambers only need to bear the pressure.
of course, if the working frequence is low, the new design is not proper, the jet engine is heavy than the current engine definitely.
if the jet engine can work on the very high frequency, each course can be allocated well, I think the size and weight have not big difference. After all the the type of combustion can finish in tiny little time.
 
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  • #26


As you mentioned "fatigue damage". I also noticed it and try to decrease the risk. I adopt proper structure to improve their force condition.
for example, I arrange these chambers on a circle position. thus the force on one chamber can be borne by all chambers. the deformation will become uniform, the part is not easy to destroied.
I adopt double wall for some import parts and input high pressure gas between the walls. Thus the condition of the force the part bear change. The parts are not easy to be damaged.
 
  • #27


As to the seal on the flat surface, I know it is difficult. I make the seal a little flexible and with proper contact surface so that it can adjust itself with chambers deformation.
Even though there is a little gas leak, as long as the composition is not serious, this part of gas will not canuse bad effect and will not influrence the efficiency.
 
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  • #28


StorminMatt, you also mentioned the heat and cool solution, here I just explain a little of the solutions.
In this engine the flow is more easy to control precise than the current engine because of the doule walls and branch pipes system. We can release a little air from the front door to form a layer of air on it to separate from the gas can be burnt, thus it can avoid contact the very high temprature and protect itself. the idea can be used on the others parts if necessary.
 
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  • #29
Qumf,
Have you taken a look at the wave rotor engine concepts?
 
  • #30
Hi,oatlids
when I published the idea including the structure of the engine on other website. Somebody ever reminded me it is like wave rotor engine. I search the wave rotor engine from internet. I think they are different.
the structure are similar, part of principle are same. but the input and outlet systems are different totally. in my memory the structure of combustion portion inside the wave rotor engine is more complicated; the original input gas to chambers is not the mixed gas can be burnt immediately.
please point out if i have something understood wrong.
 
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  • #31
Qumf,
I do not deal directly with wave rotor engines, but I do have my hand in constant-volume combustion type concepts. Constant-volume combustion is always the goal but is quite difficult to achieve. You will realize this as you move from theoretical to experimental work. I would look more towards isolating whether your ideas on achieving constant volume combustion is feasible. Constant volume combustion is very well-defined.

As far as the wave rotor engine, you may be able to find more research regarding it if you have a subscription to a journal or are affiliated with a university with access to such. AIAA is a common on in our industry. There are quite a few Chinese Universities that do propulsion research and have publication archives as well. The wave rotor engine if you read the descriptions online is more of a "pressure-gain" combustor. Constant-volume combustion is that hard to achieve. Pulse detonations engines are a more common approach to achieving constant-volume combustion.

Notes:
How do you plan on injecting the fuel and air in the rotating chambers? Moreover how do you plan to make it so that it can be considered pre-mixed?
Since you say that the flow is relatively stagnant at the time of combustion, how do you plan on ejecting the gas to the turbines for work extraction? If you were planning on relying pressure expansion to purge gases, the turbines now see a lower pressure than you estimated at time of combustion, does this combustion process still provide a benefit?
Since you don't have flame holding in your design, how do you plan on initiating the combustible mixture?
 
  • #32
Thank you for the concerns. I try to answer your questions:

“How do you plan on injecting the fuel and air in the rotating chambers? Moreover how do you plan to make it so that it can be considered pre-mixed?”-----Do you know the old type internal combustion engine on gasline? I plan to use same principle to mix fuel to air.It uses carburettor. Of course I need to improve the structure to get much better effection. The fuel will be injected at many points.
"Since you say that the flow is relatively stagnant at the time of combustion, how do you plan on ejecting the gas to the turbines for work extraction? If you were planning on relying pressure expansion to purge gases, the turbines now see a lower pressure than you estimated at time of combustion, does this combustion process still provide a benefit?"----I can not understand the sentences well. I can say, the gas pressure just after combustion and it at the turbine can be much different because there is branch pipe system the two places. There are many times of combustion happen in turn, not at the same time. they support each other to push turbine. I suggest you read my article again.

"Since you don't have flame holding in your design, how do you plan on initiating the combustible mixture?"------because the front door is rotating, and it is thick comparatively, while working orderly, the flame is led from one chamber to the one neighborhood through a path inside the front door. To choose the proper position(occasion) in the front door can get the proper temperature of the flame.(it is not the most hot, but can initiate gas)
 
  • #33
Continue to discuss the feasibillity,
Now I discuss the the structure and function of exhaust system, that including the branch pipes, general pipe and turbine.

The branch pipe, general pipe,the turbine install behind the chambers.

The function of branch pipes behind the chambers:

because I need energy to drive the compressor(blower) in front of the chambers, the common way is to install a turbine to receive the energy of the exhaust gas from the chambers. So I set a turbine.
When the burnt gas will go through the turbine, we need to keep the speed and pressure stable. It’s good to utilize the kinetic energy efficiently from the gas and is benificial for turbine to bear the load.
for a certain exhaust branch pipe, the gas spout intermittently, so the condition of gas inside a branch pipe is changable. I have to arrange these flows to cooperate to get a comparable stable current.
So I set a group of output branch pipes after the chambers. each branch pipe is corresponding to a chamber. then these branch pipes merge one general pipe. the turbine wheel is installed within the general pipe.
several pairs of chambers spout gas alternately and cooperate, we also can add a space behind branch pipes as buffer storage and to regulate gases before turbine, when the gases encounters the turbine, the condition is relatively stable.
These branch pipes have a certain volume space. when the gas rush out off the chambers, A certain volume of buffer storage can reduce the fluctuation.depending on the branch pipes, at last in the general pipe the flow can become comparable stable.
When the working course turns to exchange tha gas ,(ie,the fresh gas enters the chambers),the speed of gases in the corresponding branch pipes is the highest and the pressure is lowest at the end of the spouting course, the Momentum of the burnt gas cause the negative pressure inside the corresponding chambers, it can suck the fresh gas into chambers afterward.
Without the branch pipes, when gas spouts out, the current will influence the gas flow in the other branch pipes, such as the course of exchange gas . Installing the branch pipes; the course will help each other by the effect of suction.
The quantity, the shape and the size of the branch pipes should be studied carefully, They are relative to the functions I state upper. it is nessesary to do some experiments to while building the engine.
The shape of the branch pipe to genaral pipe should be designed carefully in order that the flows can cooperate well, the energy loss and flow resistance should be as possible as small.
 
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  • #34
I try to calculate the temperature before the turbine:
Pls see below figure 4: the figure show how I find their relationship of the main parameters in different course. (Sometimes I call constant-volume combustion type as closed combustion type)

Normally the pressure after compression is pretty high, if other things do not change, we make the pressure by combustion lower , the efficiency reduce a little, meanwhile the temperature before turbine reduce much,
I make a example: Set the temperature of outside air: 300K, k=1.4, set the pressure after compression/before compression α=7, the pressure after combustion/before combustion β=7.5, thus the temperature turbine 2206K; theory efficiency: η=60.2%; k=1.4, α=7, β=7, the temperature turbine 2100K, η=59.6%; k=1.4, α=7, β=6.5, the temperature turbine 1992K, η=58.9%; k=1.4, α=7, β=6, the temperature turbine1881K, η=58.2%;
Actually changing β is by change the volume proportion of fresh gas in each time or the concentration of fuel a little. In this example, η is reduced by 3%, the temperature before turbine decrease by 400K.

α and β all contribute to η. usually we expect the temperature before turbine not very high because of reliabity and life, thus in order to ensure a certain η, we need to increase α.
High temperature normally means high efficiency,but if it is too high, it will cause a series problem, it will influence the life and reliabity of the engine. Because the restriction, sometimes we have to make concession on efficiency.
This example just reminds the relation. The data to some parameters may not be so precise; Some modulus will change a little from in normal case to a very high temperature. Here I assume them unvaried for convenient study . Anyway it is a good enough reference for us.
The method also is used to calculate the temperature of each work course.
 

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  • #35
I have to compensate a little.
There is a sentence in the upper derivation "I set the pressure before turbine same as it after compressor. You can the same description appear in #9 floor. You can refer to it.
 
<h2>1. What is a constant-volume combustion type gas turbine engine?</h2><p>A constant-volume combustion type gas turbine engine is a type of internal combustion engine that uses a continuous combustion process to convert fuel into mechanical energy. Unlike traditional piston engines, the combustion process in a constant-volume engine occurs at a constant volume, resulting in more efficient and consistent power output.</p><h2>2. What are the advantages of a constant-volume combustion type gas turbine engine?</h2><p>The main advantage of a constant-volume combustion type gas turbine engine is its high power-to-weight ratio. This means that it can produce a lot of power in a relatively small and lightweight package. Additionally, these engines are more fuel-efficient and have lower emissions compared to other internal combustion engines.</p><h2>3. How does a constant-volume combustion type gas turbine engine work?</h2><p>In a constant-volume combustion type gas turbine engine, air is compressed and mixed with fuel in a combustion chamber. The mixture is then ignited, causing a rapid expansion of gases. This expansion drives a turbine, which in turn powers the engine. The combustion process is continuous, resulting in a constant power output.</p><h2>4. What are the applications of a constant-volume combustion type gas turbine engine?</h2><p>Constant-volume combustion type gas turbine engines are commonly used in aircraft, power generation, and industrial applications. They are also being developed for use in hybrid and electric vehicles as a more efficient and environmentally-friendly alternative to traditional engines.</p><h2>5. What are the potential challenges or limitations of a constant-volume combustion type gas turbine engine?</h2><p>One potential challenge of constant-volume combustion type gas turbine engines is their high cost and complexity compared to other types of engines. They also require a significant amount of maintenance and may have limited durability in certain applications. Additionally, the use of fossil fuels in these engines contributes to carbon emissions and climate change.</p>

1. What is a constant-volume combustion type gas turbine engine?

A constant-volume combustion type gas turbine engine is a type of internal combustion engine that uses a continuous combustion process to convert fuel into mechanical energy. Unlike traditional piston engines, the combustion process in a constant-volume engine occurs at a constant volume, resulting in more efficient and consistent power output.

2. What are the advantages of a constant-volume combustion type gas turbine engine?

The main advantage of a constant-volume combustion type gas turbine engine is its high power-to-weight ratio. This means that it can produce a lot of power in a relatively small and lightweight package. Additionally, these engines are more fuel-efficient and have lower emissions compared to other internal combustion engines.

3. How does a constant-volume combustion type gas turbine engine work?

In a constant-volume combustion type gas turbine engine, air is compressed and mixed with fuel in a combustion chamber. The mixture is then ignited, causing a rapid expansion of gases. This expansion drives a turbine, which in turn powers the engine. The combustion process is continuous, resulting in a constant power output.

4. What are the applications of a constant-volume combustion type gas turbine engine?

Constant-volume combustion type gas turbine engines are commonly used in aircraft, power generation, and industrial applications. They are also being developed for use in hybrid and electric vehicles as a more efficient and environmentally-friendly alternative to traditional engines.

5. What are the potential challenges or limitations of a constant-volume combustion type gas turbine engine?

One potential challenge of constant-volume combustion type gas turbine engines is their high cost and complexity compared to other types of engines. They also require a significant amount of maintenance and may have limited durability in certain applications. Additionally, the use of fossil fuels in these engines contributes to carbon emissions and climate change.

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