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Tour Engine has Prototype II split-cycle engine running

Tour-proto-ii
Prototype II Tour Engine—a novel split-cycle engine—on the bench. The hot side is on the right. Click to enlarge.

Tour Engine, the developer of a novel split-cycle engine (earlier post), has its Prototype II engine running and will present details on its operation at the upcoming SAE 2012 World Congress in Detroit.

In early bench-testing of the new prototype, Tour found samples of a similar work gain value to that from a conventional control engine (129 kJ for the control and 124 kJ for the Tour engine in the example depicted below), with both operated at about half throttle and using a symmetrical Tour engine with a compression ratio similar to the expansion ratio (8:1). Other examples show similar trends, according to Tour.

However, notes Oded Tour, the Tour engine can be greatly improved by having an expansion ratio of up to 3 times larger than the compression ratio and by further differential engineering of the compressor cylinder and the combustor cylinder. Thus, the company plans in the near future to modify prototype II to have an expansion ratio of 16:1 with compression ratio of 8:1.

At first cut, roughly, we have not done any worse than the baseline engine. The way forward for the Tour engine is clear substantial improvement.

—Oded Tour

Tourrecordings1
Recordings from Prototype II. Top: Five cycles showing in-cylinder pressure as a function of time. Middle: A set of readings relating to a specific cycle. Bottom left: Pressure as a function of volume for the same specific cycle (p-V): The area within the blue and red curves represents the compression work invested and the resulting combustion work extracted, respectively. Bottom Right: 1) At power piston TDC the crossover valve opens and the pressures in the two cylinders are almost equalized. 2) Timing of the spark. 3) Combustion initiation is timed to compound the maximum pressure achieved during compression (with an open crossover valve). 4) Closing of the crossover valve. 5) Power stroke is being executed in the Hot-Cylinder. Click to enlarge.


Tourcontrol
Readings from control engine. Click to enlarge.

The premise of a split-cycle engine is that segregating the intake and compression strokes in one cylinder, and the combustion and expansion strokes in another, coupled cylinder, provides a thermodynamic advantage enabling a more efficient engine. Most current split-cycle designs use a gas crossover passage or intermediate chamber to connect discrete cylinder pairs. By contrast, the Tour engine configuration directly couples the two opposing cylinders, with a single crossover valve controlling the charge flow between the two cylinders.

Tour2
Tour3
SolidWorks Design of Prototype II, partial transparent front view. The vertical purple part located between the two engine sides is the custom designed connecting plate that hosts the crossover valve. The hydraulic pump that is connected via a timing belt to the engine and is used to load the engine is depicted on the top. Click to enlarge.   SolidWorks Design of Prototype II, back view. The four gearwheels have the following functions: At the 9 o’clock position is the gearwheel connected to the compressor cylinder. The crossover valve mechanical cam is at 12 o’clock (since the valve actuation is both precise and fast – it opens and closes within about 45 degrees so that a large cam is required). At the 3 o’clock position is the combustion cylinder gearwheel, and at 6 o’clock is the hydraulic pump gearwheel. Click to enlarge.

The crossover valve enables the execution of an integrated cycle: the inducted working fluid is compressed and combusted as part of a single cycle, thereby avoiding piston runaway. The Prototype II Tour engine, based on two 190 cc Briggs & Stratton engines, uses a mechanically actuated crossover valve.

The Tour engine is designed to operate using conventional realistic compression ratios (8:1 to 20:1 depending upon fuel type and the use of SI or CI cycle), and is designed to fire at the end of the compression process (before any decompression occurs)—while the crossover valve remains open—very similarly to conventional engines but retaining the split-cycle thermodynamic advantages.

Firing with an open crossover valve allows the TourEngine to follow the conventional 4-stroke cycle thermodynamics, but on a split-cycle platform. (The disadvantage is a small efficiency penalty associated with a larger surface area acting as a heat sink at combustion initiation.) With complete charge transfer, the crossover valve closes; combustion continues in the hot cylinder.

The crossover valve is key to the success of the engine; it must be able to open to allow the compressed charge transfer and then immediately close (on the order of 30–50 crankshaft degrees) and transfer the charge with minimal resistance. In other words, the valve needs to be large enough in cross-section not to be a bottleneck, but also thin enough in profile to ensure minimal dead volume.

Dead volume on the compression side prevents full transfer of the compressed working fluid, while dead volume on the expansion side reduces volumetric efficiency and decreases the phase lag for a given compression ratio, which will require even faster valve actuation and therefore will be more challenging

Crossover-valve-render
Crossover valve and cylinder connecting plate. The engine is designed in a modular fashion such that several different connecting plates housing different crossover valves could be tested on the same engine. Click to enlarge.

The alpha prototype used a spring-loaded crossover valve. In addition to the current mechanically actuated crossover valve used in Prototype II, Tour is also developing several other crossover valve concepts including an electromagnetic crossover valve that is actuated by compression (open) and combustion (close) while the electromagnetic force is used to fine tune (hinge) the valve to close and open at the precise timing.

According to Oded Tour, Tour Engine is in discussions with several OEMs on establishing a joint development aiming on taking the concept to the next level by building an advanced Tour engine.

GM Vice President of Global Research and Development Dr. Alan Taub noted in his talk at the 2011 DEER conference that split-cycle engine technology looks promising and that GM was pushing in its R&D laboratory to see if it can get split-cycle technology “moving”. (Earlier post.)

...we may finally be entering the era where the demand for fuel efficiency will be allowing us to break away from what has become the standard architecture of our engines, and in particular the idea of separating the compression and the combustion (expansion) cylinders, into a dual stage engine. People have talked about it, a lot of people are starting to build prototypes in this, and the driving force is clear: we can see very dramatic improvements in efficiency by going to the DCDE [Discrete Compression Discrete Expansion] architecture. It takes mass, it takes cost, it takes complexity, but giving those kind of efficiency improvements, it is definitely something we need to explore further.

—Alan Taub at DEER 2011

Dr. Chris Atkinson, Professor, Mechanical and Aerospace Engineering at West Virginia University and an advisor to Tour Engine, concurs that over the last three to four years, “a remarkable openness to contemplating such new engine architectures” has emerged among the major OEMs. As for Tour Engine, he added, leaving aside the commercialization aspects:

They have done remarkably well from a technical point of view. To have a [new] engine running legitimately with comparable efficiency to a conventional engine is very much a remarkable feat. Normally, you take several steps back and then you try to work out what you’ve done wrong, whereas here, they are close to conventional already. On a shoestring budget with a minimum of people they have done remarkable things; the quality is very good—approaching OEM quality.

The Prototype II Tour Engine was built with the aid of the Israel Ministry of Energy and Water Resources.

Comments

SimonDM

"You must realize that an increase in compression ratio by two units, e.g. from 8:1 to 10:1 has a decisive impact on fuel consumption in this case."

Now I better understand the source of your claims. Thermodynamically speaking, if you keep things like compression and expansion ratio and maximum temperature the same but if you cool in between expansion, you have a lower temperature after compression and hence a lower average temperature of heat addition, which thermodynamically speaking reduces efficiency as E-P rightly claims. If you however modify other things like expansion ratio, maximum temperature or in your example compression ratio, of course it is possible then that even thermodynamic efficiency increases (as average temperature of heat addition can even increase if you raise compression ratio enough) but then it is comparing apples to pears with regards to thermodynamic cycles. E-P is right in that intercooling would detract to the efficiency of the (Carnot) engine keeping the rest of the cycle the same, but you are right in that by changing the parameters of the cycle (you changed the cold source temperature in the Carnot cycle or the compression ratio in the diesel/otto cycle) as allowed by intercooling you could increase thermodynamic efficiency.

Peter_XX

@SimonDM
Absolutely nothing Engineer-Poet says is true. He does not have a clue about what he is talking about. Why do you not read my comments? I already explained the impact of an intercooler and listed a number of parameters. Intercooling increases the thermodynamic efficiency. Period! Look at the diagrams I provided! Are you completely blind? Using the Carnot cycle as an example, I could show that efficiency increases if the temperature before the engine is lower. Why can you not accept that? I have cited two examples. You should not mix them. I will separate them below.

The Scania intercooled Scania engine had actually somewhat lower compression ratio (15.2:1) compared to the non-intercooled engine (16:1). This has nothing to do with intercooling per se but was simply a measure to increase engine power for the intercooled engine even more that the intercooling alone would provide. With the same compression ratio in both cases, the difference in efficiency would have been even greater. If the comparison would be made at the same maximum cylinder pressure and engine power, the compression ratio could be even higher (I can provide a calculation on that later…) for the intercooled engine with additional gain. One fact you seem to have so difficult to understand is that compression work decreases when intercooling is used. You will get a hint about that below but I will give you one example here. When natural gas is compressed for refueling, it is normally done in several stages with intercooling in between the stages. One reason for this (besides temperature problems) is to reduce the compression work (this was related to my original comment about the Tour engine but I will not elaborate further on that here). The most efficient way would be to use isothermal compression. However, no such (practical) device exists, so multi-stage compression with intercooling is the only option. Manufacturers of natural gas compressors are not stupid as the Engineer-Poet.

The other example I gave concerned gasoline engines. It should be obvious to anyone that a higher compression ratio improves thermodynamic efficiency. Somehow, I sense that you also realize that. If we make an idealized calculation the otto cycle efficiency becomes: =1-1/V1/V2^(p-1), where (V1/V2) is the compression ratio and p is the polytropic exponent. I use a value for p at 1.34 in this example. I presume that the air mass flow for both engines should be the same. With 8:1 in compression ratio for the non-intercooled engine and 10:1 for the intercooled engine, we get the corresponding ideal efficiencies as 50.7% and 54.3%. The relative difference is roughly 7%: This is due to the thermodynamic advantage from a higher compression ratio alone. All the other positive impacts from intercooling would also apply in this case but I will limit these examples. In a practical situation we find that the temperature at the engine top dead center actually will be higher for the non-intercooled engine in spite of the lower compression ratio. Thus, spark advance would have to be reduced for the non-intercooled engine with additional losses. There are two reasons for this outcome. First, the charge pressure has to be increased for the non-intercooled engine to compensate for the lower air density. Second, we do not have an intercooler. Although the compression ratio is lower, this does not compensate for the two other factors mentioned. If we have a charge pressure of 2 bar (abs, 1 bar overpressure) and a pressure drop of 70 mbar over the intercooler for the intercooled engine, the non-intercooled engine must have a charge pressure of 2.5 bar to get the same air mass flow. You must now realize that the compression work of the compressor is lower for the intercooled engine (air mass flow is the same but the pressure is different). This is something we might utilize on a split-cycle engine to a much greater extent.

Do you need more free lectures?

Peter_XX

@SimonDM
I saw some font problems in the equation above that occured during cut&paste. The first sign before the "=" should be the Greek letter for efficiency and the other two should be parenthesis.

BTW, have you noted how quiet Engineer-Poet has become on this topic? Maybe he has realized how wrong he was. Of course, I will never get this recognition from him, or an apology.

Engineer-Poet

I'm of mixed feelings about this now.  Sad, because I was busy with other things for two days and didn't get back as soon as I said I would.  Amused, because it has given Peter XX ample opportunity to make a fool of himself at length.

Case in point:

The following is a very simplified calculation: We can use 1000 K as maximum temperature in both cases and 150°C (423 K) for the engine without intercooler and 50°C (323 K) for the engine with intercooler. The latter temperatures will be the inlet temperatures for this imaginary engine. The idealized efficiency for the engine without intercooler will be 57.7% (1-1000/423.15) and 67.7% (1-1000/323.15) for the engine with intercooler.
It's not simplified, it's faulty.  He listed the intake-manifold temperature, not the heat-rejection (exhaust) temperature.  It's the temperature of heat rejection that's relevant to Carnot efficiency; even in the simplest possible analysis, what he posted is pure nonsense.  What's that memorable phrase... "not even wrong"?

It's similar to what he said here on April 22:

split cycle engines is that they allow cooling the charge after compression so that combustion can be accomplished at much lower temperature than in conventional ICEs.
Supercharging with intercooling allows combustion to take place at similar pressure and higher density, permitting greater expansion and thus greater energy recovery.  Cooling after compression doesn't do this; it does not reduce compression work AND requires additional heat just to get to the same pre-expansion pressure, which can only cut efficiency.

The BSFC curve for the intercooled engine is irrelevant to the April 22 claim.  That engine is intercooled before final compression (approximating the isothermal compression step of the Carnot cycle), not after compression as in the 4/22 proposal for a split-cycle engine.

Engineer-Poet

SimonDM:  I'm glad you can see through the bluster.  The guy with the PhD has been caught with his pants down, and he hates it (being caught, that is) with a passion.  This may be where being American confers an advantage on me; with no hereditary nobility, there's less social pressure to defer to people with titles or honors when they've made a gaffe.  I refuse to defer to Peter's social standing because he's wrong, and it drives him absolutely crazy.

Here's an example of the crazy:

One fact you seem to have so difficult to understand is that compression work decreases when intercooling is used.
Contradicted by the record:  "While I'd be the last to argue that an intercooled engine cannot be more efficient than one without intercooling (just the downsized mechanical section and reduced compression back-work are solid advantages..."

What do you call it when someone keeps contradicting the truth that's plainly in front of them?

His example of the two engines above ignores the real advantage of a turbocharged split-cycle engine, which is the ability to use asymmetric compression and expansion ratios without sacrificing volumetric efficiency... but that's sort of beside the point, as that's not under dispute.

And now to watch the next episode of The Meltdown of Peter XX, PhD.

Peter_XX

@Engineer-Poet
I cannot see any rational thinking behind your thoughts and I do not bother to comment on your insults. Please come back with your calculations so that I can examine them! If we skip the discussion about theory for later, hard experimental data is more relevant and here I sit on a mountain of data.

You dismissed my previous data on Scania engines as “irrelevant” (although I would not think operators of heavy-duty vehicles would agree), so I wonder where I could find any example that meet your standards for relevance. What should I do next? Maybe more examples from car or heavy-duty engines… No, I will show some evidence from a large 4-stroke marine diesel engine this time.

An article in the German MTZ journal in March describes the application of two-stage turbocharging on a large marine diesel engine (MAN 18V48/60TS, with cylinder diameter=480 mm). The engine has both an intercooler between the stages and an aftercooler after the second stage. The authors refer to these as CAC (charge air cooling). The authors state the following about CAC: “Charge air cooling is an effective method of reducing both NOx emissions and SFOC.” SFOC stands for specific fuel oil consumption. The authors continue: “MAN employs two-stage charge air cooling to achieve the lowest charge air temperatures between the two compressor stages and in the intake manifold.” If you are still skeptical, you can have a look on the diagram via the link below. If the air temperature increases from the low level of ~40 deg. C in either the low-pressure (LP) CAC or the high-pressure (HP) CAC, SFOC increase significantly. If the MAN engineers would listen to the thermodynamic theories of a Poet, they would remove the charge air coolers. I do not think they are that stupid.

MTZ industrial, Special Edition MTZ, March 2002.

http://www.picvalley.net/v.php?p=u/2444/85297616016519605361335888169t5DhoY7fHlO5JfCLv2we.JPG

Peter_XX

@Engineer-Poet
I have now provided two cases with experimental data showing that you are wrong. You have provided noting to support your “home-cooked” theories on thermodynamics. The score is now 2:0 but I will prepare and post more experimental data, so I will further improve the score!

It is fun to see that you try to compensate your lack of knowledge by stupid ideas. A Carnot engine would most likely be a “closed” engine, such as a Stirling engine. One could perhaps try to envision a Carnot engine with gas exchange. Rudolf Diesel did make an effort to do so before he invented the diesel cycle. Anyway, it is impossible to envision that you could have gas exchange during adiabatic compression or expansion, so the gas exchange would have to be done during another phase. Thus, we end up with only two temperatures for efficiency calculation, just as in the diagram on the Internet you referred to and in my calculation. The lower temperature corresponds to the engine inlet temperature and in the Carnot engine inlet and exhaust temperatures would be the same. Conclusion: my calculation is correct. As with experimental data, you have not provided any calculations to back your theories. My calculation can be validated by using any text book in this field. Perhaps you should buy such a book and read some fundamentals about the topics under discussion.

Peter_XX

For those of you who are interested, the link below is to an engine that use external compression in several stages with intercooling/aftercooling between and after the compression stages. This is still more or less a concept engine but theoretical calculations show the potential for very high efficiency. This engine has internal combustion. My original comments refer to that a split-cycle engine might use the same type of compression and gas exchange. Those of you who did not understand my original comments can have a look at the site below and gain some knowledge in the process.

http://www.aumet.fi/

SimonDM

http://www.aumet.fi/html/faq.htm

Q: Doesn’t the intercooling after the piston compressor decrease the overall efficiency, when heat is removed from the process?
A: Yes it does.

SimonDM

Peter XX on record: "If the air temperature increases from the low level of ~40 deg. C in either the low-pressure (LP) CAC or the high-pressure (HP) CAC, SFOC increase significantly. If the MAN engineers would listen to the thermodynamic theories of a Poet, they would remove the charge air coolers. I do not think they are that stupid."

What I see: intercooling can make an engine more efficient.

Engineer-Poet on the record: "While I'd be the last to argue that an intercooled engine cannot be more efficient than one without intercooling (just the downsized mechanical section and reduced compression back-work are solid advantages..."

What I see: intercooling can make an engine more efficient.

I do however also see that as far as the theoretical aspects of thermodynamics are concerned, E-P is the one that has it right. I do not doubt Peter XX on the technical aspects of engines in what he posts.

Peter_XX

@SimonDM
Well, E-P has not provided any results from calculations. Since he has provided nothing in this field, what is your basis for the basis that E-Ps theoretical aspects would be correct? I already pointed you a monumental error in his theory about how the Carnot cycle works.

You should also note that my theoretical explanations go hand in hand with experimental data. Both theory and experiments agree. If E-Ps theories would be correct, he would have to find experimental data to back up his theories. No way! He has already lost this discussion. I hope this will be a lesson for life in his case.

I will provide more experimental data later.

Peter_XX

@SimonDM
You had a question about the Aumet engine and boldly you also provided an answer. It is wrong! You should read my comments more carefully. I already explained that isothermal compression require less work than adiabatic compression. This work has to be taken from the engine crankshaft. With cooling, we can also increase the compression/expansion ratio in the engine, since the pressure and temperature at top dead center is lower. You should also note that if we look at the theoretical efficiency of the otto cycle, ambient temperature as no impact at all on efficiency. If we reduce the temperature, as intercooling does, we do not lose efficiency as you and E-P seem to think. You cannot find temperature anywhere in the equation (please have a look). However, this is an idealized equation. In reality the thermodynamic properties of the gases change with temperature (and composition due to combustion). Air has a value of cp/cv (this is the ideal value for “p” in the exponent in the equation) at 1.4 at ambient temperature. At 1000 deg. C, the cp/cv is reduced to 1.321. The idealized efficiency of an otto engine with 10:1 in compression ratio is 60.2% with cp/cv of 1.4 and 52.2% with 1.321 respectively. Note that this is at the same compression ratio in both cases (we have not taken advantage of that compression ratio can be increased with intercooling). The difference in practice will be lower, but I will leave this explanation for later. However, this is still an explanation as to why you should always cool the air as much as possible before the engine.

If you do not believe my explanation above, you should have a look again at the results on the MAN engine. It is obvious that cooling after both compression stages have a positive effect on fuel oil consumption. This is hard experimental data. Why should the same principles not work on any other engine (Aumet, split cycle,…)?

If you have theories about thermodynamics, why don’t you post your calculations to prove your point?

Peter_XX

@Engineer-Poet & SimonDM
Since two examples of experimental data obviously were not enough for you, I am posting yet another comparison that shows the impact of an intercooler on efficiency. As I previously noted, Scania produced non-intercooled and intercooled engines in parallel for a relatively long period of time. This comparison is from the late 1980’s, while the first one was from the early 1980’s.

Again, we see a substantial advantage for the intercooled engine. The difference is on average somewhat greater than in the first example and shifted towards lower rpm this time.

The score on experimental data is now 3:0.
The score on calculations is now 2:0.

Neither one of you have provided any experimental data nor any calculations to prove your point.

http://www.picvalley.net/v.php?p=u/2148/63142416411822294911336028287kd1OxIRu4JdFPB2bJC6s.JPG

SimonDM

"You had a question about the Aumet engine and boldly you also provided an answer."

No, I copied and pasted an excerpt from the faq of the site you posted. I did not answer anything.

SimonDM

"If you have theories about thermodynamics, why don’t you post your calculations to prove your point?"

Intercooling and reheating will always decrease the thermal efficiency unless they are accompanied by regeneration. This is because intercooling decreases the average temperature at which heat is added, and reheating increases the average temperature at which heat is rejected.

http://web.me.unr.edu/me372/Spring2001/The%20Brayton%20Cycle%20with%20Regeneration.pdf>The Brayton Cycle With Regeneration

This is a general statement about the thermodynamic aspect. It doesn't mean that by modifying other cycle parameters, such as compression ratio for example as allowed by intercooling, that thermodynamic cycle efficiency can't be increased again. Generally however, keeping the other parameters of the cycle the same, thermodynamic cycle efficiency does decrease by intercooling. This is generally accepted knowledge in thermodynamics.

I'm too lazy to do the calculations myself so I refer you to example 2 on page 12 for actual calculations for a very simplified cycle analysis that intercooling and reheating without regeneration decrease efficiency.

There is however for example also a paper called: "Raising cycle efficiency by intercooling in air-cooled gas turbines":

http://www.mendeley.com/research/raising-cycle-efficiency-intercooling-aircooled-gas-turbines-5/#

Which shows thermodynamic cycle efficiency of a brayton cycle gas turbine CAN be increased by intercooling. This is however when taking cooling air requirements into account in the thermodynamic cycle analysis. So it depends on what you take into account in your thermodynamic cycle analysis. If in your case, you modify the cycle by changing compression ratio from 8:1 to 10:1 and take cylinder wall heat losses into account in a more detailed thermodynamic cycle analysis, sure, intercooling can increase cycle efficiency of this modified cycle. However, in the most simplistic case and analysis, the general statement that intercooling and reheating without regeneration decrease efficiency is true. So I don't see what the bickering is so much about.

Peter_XX

@SimonDM
Well, you have to refer to where you get the information. I anticipated that it was your own words.

It seems as you deliberately left out information from the answer and you also fail to include other questions and answers relevant to this topic. All effects must also be taken into account, e.g. the impact on compression work, which decreases when intercooling is used. All in all, the Aumet engine has a potential for higher overall efficiency than a conventional engine, and this is one of the objectives for the inventor. Obviously, you have failed to note that, you only read what you want.

Peter_XX

@SimonDM
If you want more in-depth information about thermodynamics of the Aumet engine, you should look at the theoretical calculations in the document provided by Aumet. This document should answer your questions and convince you that the engine, taking its small size into consideration in the calculations, has a potential for very high efficiency (45% is cited), although the assumptions made by the author are very conservative. BTW, do you really think that the inventor would propose an engine that would be less efficient than a conventional engine? Such an invention would have a bleak future. In contrast, Aumet state (e.g. INSA paper, 2010) the following as the first point of the advantages of the engine:
- high efficiency, especially at part loads

So, what about the last experimental data I posted on the two Scania engines? Could I prove to you this time that intercooling is efficient, or do you need more evidence?

SimonDM

"Well, you have to refer to where you get the information. I anticipated that it was your own words."

I posted the reference right at the very top of the post, impossible to miss it.

"It seems as you deliberately left out information from the answer"

I posted the relevant part. I did put in a later post that it was an EXCERPT.

Obviously, you have failed to note that, you only read what you want.

And you don't read what you don't want. That's why I posted that excerpt in the first place. I know very well at Aumet they want to make an efficient engine otherwise there would be no point of switching from a conventional Otto or Diesel engine to anything else and they wouldn't get investment. Yet there has to be a reason why they answered "Yes it does." to a decrease in efficiency, isn't it? Or are they idiots too?

SimonDM

"So, what about the last experimental data I posted on the two Scania engines? Could I prove to you this time that intercooling is efficient, or do you need more evidence?"

As previously mentioned, I don't doubt you on the technical or experimental aspects of engines you post and even E-P acknowledged that an intercooled engine CAN be more efficient.

Peter_XX

@ SimonDM
Earlier in life, I have had, on occasions, the privilege to educate young students (i.e. students with at least M.Sc. degrees). However, I have never ever had to encounter any persons such stubborn and with such apparent lack of basic knowledge before as you and Engineer-Poet. Therefore, I must be much more systematic in future “lectures”. It is definitely not the best idea to start with the most complicated example, i.e. split-cycle engines, or the Aumet engine, as a special case. I suggest the following order:

1. Impact on intercooling on diesel engines
2. Impact on intercooling on otto engines
3. Implications for split-cycle engines

Would this order be O.K. for you? For each topic, I plan to provide both calculations and experimental data to back-up theoretical explanations.

I also have one question: Are you just a pseudonym for the Engineer-Poet or are you two different persons? Please also back up your answer with some evidence.

Engineer-Poet

<munches popcorn>

SimonDM

I am sorry, but no one at this point is really disputing that intercooling can make an engine more efficient so your lectures would be pointless. I still don't see what your main issue with E-P is about. The biggest issue that I have with any of your claims is as E-P that cooling between compression and combustion could improve thermal efficiency.

There seems some misunderstandings on all parties though as to the exact impact of intercooling on thermal efficiency. I was wrong previously in using a way too generalized statement on the effect of intercooling on thermodynamic efficiency. Since intercooling in practice is ALWAYS used with super/turbocharging in a reciprocating internal combustion engine, it can make an engine more efficient even in simple thermodynamic cycle analysis. If however no or too little super/turbocharging were to be used and compression ratio were to remain the same, then I do maintain intercooling would be detrimental to thermal efficiency in simple cycle analysis. Such a thing is however not realistic as you cannot stop compression mid cylinder stroke to cool the charge and then compress it further. In a Brayton cycle turbine it is generally accepted in simple thermodynamic cycle analysis that keeping other cycle parameters the same, intercooling alone is detrimental to thermal efficiency. E-P gave a link to this which I didn't bother reading and ended up linking to again myself.

FYI, I am Belgian (are you Dutch or German?) while as Engineer-Poet is American. I'm a civil engineer, specialty in textiles. I graduated in 2001. I had thermodynamics in my second year only (1998) so my skills are a bit rusty.

Peter_XX

@ SimonDM
O.K. Good! Then I know a little more about who you are.

Now, you have to understand that I simply have to start explaining the easiest things first and then go on with more complex issues. I acknowledge that you have accepted that intercooling works on a normal engine. The Engineer-Poet does not, so I simply have to go through that first before going on with more complicated issues. Maybe I can just jump over the otto engine, we will see...

I will not comment on your statements this time. I will only ask you to consider one issue with conventional engines that also apply to split-cycle or the Aumet type of engines. We must minimize the total losses from an engine to increase efficiency. There is a loss in an intercooler but this is not the biggest loss from an engine. You cannot stare at the intercooler loss alone; you have to look at all the losses. The exhaust loss is much bigger than the intercooler loss and there is much more to be gained by minimizing the bigger losses. Intercooling decreases the exhaust loss. This does also the Atkinson cycle, the Aumet engine (which use a modified Atkinson cycle) and split-cycle engines (at least in some cases). The whole point is that you can gain more by reducing the exhaust losses than the loss in the intercooler. I tried to explain this before, but I would have to elaborate it in much more detail for you to fully understand it. For the time being, consider what I just hinted about the total losses. you will get the complete picture later.

For the moment, I have other things to do; I have a job as well, so I will not be active on GCC until late this weekend.

Engineer-Poet

It's well past the weekend, and nothing yet.

Apparently it's very hard to back up your claims.

Engineer-Poet

Here we are at another weekend. Got anything?

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