Will Split-Cycle Engine Compete With EV Powertrains?
One cylinder of Scuderi's split-cycle engine performs intake and compression, while the other handles power and exhaust. The engine completes all four strokes in one crankshaft revolution. (Figure courtesy of Scuderi Group.)
OK...I'll concede that of all my criticisms of the split-cycle concept, the temperature comments are the ones I'm least certain about. Although I still contend overheating will be a challenge based on my knowledge - it may indeed be engineerable. For example, the wankel engine has compression / combustion / exhaust always in the same location of the engine (except for the rotor). I know that this was a big development challenge for Mazda (I once owned a racing rotary), but they worked it out with special coatings on the walls, carbon seals, and (check it out) a huge radiator vs. engine size. Efficiency was (and is still) not good, unfortunately.
The main question for the split-cycle concept is "what does it bring to the table that a miller or atkinson cycle engine doesn't?". I contend - almost nothing, and it has some disadvantages to boot.
I really like what Mazda is trying to do with their Activ engines - they are exploring limits of optimization from several angles: gasoline engines with high 14:1 compression ratios, and diesel engines with low 14:1 compression ratios.
Although I have a bias opinion, because of the DRE, I do not believe cooling the power cylinder is going to be a problem.
We build race engines that have no water jackets between each cylinder to allow for very large cylinder bores. These engines are used in sprint cars that run nearly wide open throttle for the entire race and produce more than 700 hp. The average amount of heat that is developed in each cylinder to produce this much HP has to be far higher than that of a power cylinder on a split cycle engine even when you consider the cool intake air bringing the average temperature down. Yet we can do this lap after lap with no cooling issues.
Today’s direct injection engines also introduce oil under the pistons to assist with cooling.
Also if the engine is in fact more efficient it will have less heat to deal with.
When running superchargers the compressor discharge temperature can exceed 200 degrees F. Since this is higher than the normal operating temperature of an engine it has a negative cooling effect. Yet they too can be run for long periods of time without adverse effects.
I agree with most of your comments. However, the "Once the avg. temperature gets too high, lubrication breaks down and engine reliability will suffer" seems a bit unfair. Saab managed to make more than a few 2 cycle engines [similar heat issues] with lifetimes warranties over 40/50 years ago. I would think that the temp problems are about the same and that modern synthetic lubricants could handle the bottom end.
Wow...I think the history of failed Scuderi claims you outline is very telling. Some of the other "breakthrough engines" I've followed over the years (and sometimes debunked) have similar many-year cycles of making bold claims then slipping dates and then coming back with new waves of promises as if the prior claims never happened.
For some reason, people get really hung-up on unique engine mechanisms. Many get obsessed with rotary engines. Rarely does this have any significant bearing on efficiency potential. It is the THERMODYNAMIC GAS PROCESSES that matter, and the engine mechanism is only the means to accomplish that. Even the most successful of the alternative engines, the wankel, actually has no efficiency advantage (in fact, disadvantages) and the only advantage is a little better compactness and fewer moving parts. Sorry Lonny Doyle, but your engine concept also falls into this category - less parts, creative mechanism, but no efficiency or power advantages whatsoever.
The Scuderi engine's gasses cycle through a rather conventional 4-stroke cycle. A big disadvantage is that the power cylinder sees very high avg. temperature: combustion/power-stroke/exhaust, then repeat. A conventional 4-stroke has intake(cool)/ compression(fairly cool)/combustion/power/exhaust all in the same cylinder - hence much lower temperature average. Once the avg. temperature gets too high, lubrication breaks down and engine reliability will suffer. Also, detonation sets in if the combustion chamber walls get too hot. Secondary things like oil "coking" which creates deposits on the cylinder walls also happen.
The only interesting / unique feature of the Scuderi I have seen is the "air hybrid" concept, the core concept which I believe has merit, but appears impractical (or at least undeveloped) in the current state.
My curiosity got the best of me. Before making any wild accusations or sipping any Koolaide, I snipped a few facts. Except for #5, they came from Scuderi web pages.
1. Based in West Springfield, Mass., USA, with offices in Frankfurt, Germany, the Scuderi Group is a research and development company focused on proliferating its technology through R&D and licensing. 2. Oct. 18, 2005 ...the company was recently awarded a $2 million engine development grant by the U.S. House of Representatives. The Scuderi technology is patented worldwide with four patents issued and three pending in the U.S. and three pending in over 45 countries. 3. Posted on 29 March 2006 Fulfilling a family dream and passing another milestone in internal combustion engine efficiency, the Scuderi Group will unveil on April 20 a working model of the first proof-of-concept prototype for its Scuderi Split-Cycle Engine. 4. 3 November 2008 With a proof-of-concept prototype on schedule to be built this year, the Scuderi Engine will undergo rigorous testing before being unveiled to the industry in April 2009 at the SAE World Congress in Detroit. 5. https://www.greentechmedia.com/articles/read/here-comes-the-air-hybrid-engine Michael Kanellos: August 20, 2010 Carmelo Scuderi finalized the Scuderi engine design in 2001. Scuderi completed a four-cylinder prototype last year and in about a month will come out with comprehensive test data on how it performs. A few months after that, the company hopes to show data pertaining to how well the engine did in a retrofitted Chevy Cavalier. 6. Sept. 7, 2011 The company’s global patent portfolio contains more than 476 patent applications filed and 154 issued in 50 countries. 7. Posted on 7 September 2011 Anyone who follows the world of alternative propulsion systems or new engines, can tell you that at the end of the day, many claims are made but very few are backed up by real data. So at Scuderi Group, it's a constant priority to dedicate ourselves to measuring and testing the Scuderi split-cycle technology as accurately and genuinely as possible.
The above items contain adequate information for me to make a personal judgement.
A. Scuderi has invested heavily in Marketing, Legal [patent factory], and Research. There is no clear indication that they have invested in Development [or development has been an unadvertised failure]. On Mar 29, 2006, they were scheduled to unveil a working model on April 20 - meaning that it was already working or ???. Then on Nov 3, 2008, they announce a proof of concept prototype to be complete by year end.
B. Scuderi's statement [#7] wrt 'measuring and testing' is contradictory to their demonstrated actions of 'simulate and advertise'.
All of us who have been involved in new ventures have misstepped and missed dates, but the 'whole history' seems a bit odd to me.
Does it look like a duck?? Walk like a duck?? Is it a duck??
'The text "When tested on several European economy-class vehicles (including an Audi A1 and a Citroen C1), the engine boosted fuel efficiency from an average of 53.5mpg to 65.4mpg, Scuderi said. It also lowered CO2 emissions from 104g/km to 85g/km." leads me to believe that it was tested in an actual vehicle. The fact that it appeared right after SWR simulations makes me wonder.'
Unfortunately, the Scuderi engine was never tested in an actual vehicle. The 'test results' for the European economy-class vehicles were only computer simulations. SWRI has built a 'proof of concept' prototype engine for Scuderi about two years ago, and that prototype has been running. This prototype has never been tested with a turbocharger or with the 'air-storage' tank, however. Scuderi has not built a 'full-size' prototype of their engine for testing in an actual car. The fact that Scuderi has not done this, especially after raising over $85 million, has prevented me from taking them very seriously, despite the fact that the Scuderi engine design may have merit.
I have an offer standing to build a full scale working model for real world testing for the Scuderi Engine. I have all machines and testing equipment necessary for building and testing their engine.
I hope they take me up on my offer.
I too am building a Split cycle engine (Doyle Rotary Engine) although it is not as well funded. It was shown at the SAE World congress last April for the first time. It was very well received. Energy Now flew here to Texas to do a story about it and while we were there a Ford Powertrain engineer had us delay our trip back from Michigan so he could take us to their research facility in Dearborn. They went over the engine design for several hours.
I too fire after TDC. I fire after TDC of the compression stroke but 30 degrees before TDC of the Power Stroke. This gives the engine time for complete combustion before the combustion is introduced to the power cylinder.
The DRE runs un-throttled. The power output is controlled by a direct injected stratified charge in the single combustion chamber.
I have built a simplified working prototype and I am working on a full scale prototype. When it is finished I will post the BSFC numbers on the DRE website. We are hoping to have the numbers before the next SAE World Congress.
I wish the best for the Scuderis, Tour, OPOC and all of the other people trying to build a better engine.
It’s a tough road. If you take a look my engine feel free to give your negative thoughts. If I can't answer them now they will not work in the real world. Physics has very tough rules that have to be followed.
A very good point has been brought up, which is that pesky old reality issue. All computer simulations are based on a model, and deliver performance and behavior based on that model, WHICH MAY HAVE MISSING TERMS! Losses due to the added friction of the second cylinder have not been mentioned, nor have the pressure drop and thermal losses that occur as the charge air passes from one cylinder to another. These losses are not something to be ignored. Next comes the question about timing. The reality is that combustion is not instantly complete, it takes a while for the flame to spread, unless detonation occurs, and this is why almost every engine fires a bit before top center. So it would be very educational for the inventors to explain how they have worked around that part of combustion dynamics. Perhaps, in the model, combustion is "instant" . IT is true that if combustion could be instant, that firing at TDC would be the best option.
So the reality is that there is a lot of highly enthusiastic speech, but no actual physical engine to show that the computer model is valid. Society will best be served if there is a real model to verify that all of the assumptions that went into the computer model actually were correct. There have been a few "next great thing" products introduced before, so investors should be wary.
Would anybody be willing to explain how firing after top center is ever effective? and how it can improve efficiency? I really want to hear that explanation. Really.
1. Forget comparing combustionable pressures to the lower precompression pressures of a supercharger. It is not a two stroke - it is a split cycle four stroke. There are some distinct advantages wrt to cylinder sealing in a noncorrosive, non-explosion, lower temperature environment.
2. I do not see any extra piston friction - it could be lower. Two complete cycles occur in 720 degrees - current engines [to my knowledge cannot do this]. In 'computer talk', I would describe the engine as a four cycle engine with 2 cycles of pipeline.
3. It would appear to me that allowing the cylinder to be designed for a more focused task - power or compression - would eliminate compromises that are required in todays engines.
4. I see advantages to firing the power cylinder just after TDC *IF* the mixture can be ignited quick enough. I noticed 2 spark plugs and no mention of the fuel injection system.
5. Todays engines "are not my father's engines" - they are more complex. It is not clear that significant additional complexity would be required - beyond the 'magic retention tank'. I am a bit skeptical - but I do not have enough info to comment.
6. The text "When tested on several European economy-class vehicles (including an Audi A1 and a Citroen C1), the engine boosted fuel efficiency from an average of 53.5mpg to 65.4mpg, Scuderi said. It also lowered CO2 emissions from 104g/km to 85g/km." leads me to believe that it was tested in an actual vehicle. The fact that it appeared right after SWR simulations makes me wonder.
7. The *idea* of separating the cycles sounds very appealling temperature, different bore/stroke combos BUT the proof is in the pudding.