increasing fuel efficiency of engine

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Merlyn
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Re: increasing fuel efficiency of engine

Postby Merlyn » Wed Nov 29, 2017 12:14 pm

We must also not forget to incorporate friction losses into all of the foregoing.
Just a thought.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Merlyn
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Re: increasing fuel efficiency of engine

Postby Merlyn » Fri Dec 01, 2017 1:08 am

Do I understand this to be a twin engine installation?
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Re: increasing fuel efficiency of engine

Postby Serguei » Fri Dec 01, 2017 9:36 am

Sorry Merlyn
make mistake. I will delete one of them.

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Re: increasing fuel efficiency of engine

Postby Serguei » Fri Dec 01, 2017 9:47 am

Merlyn, you right. Friction losses are an important part of both engines. I think that necessary, from my side, to analyze in detail friction losses in the suggested engine. From the first view it seems normal force in the sleeve will be significantly less than in the conventional one.

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Merlyn
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Re: increasing fuel efficiency of engine

Postby Merlyn » Sat Dec 02, 2017 9:45 am

Sleeve?
Sleeve =Liner?
Be interesting working out the coeffiency of friction of a rack v a Liner, less surface area on a two stroke ( ports ) v four stroke.
Plus square engines different from long stroke bonkers for surface area calcs.
No addendum nor dedendum calculations to be taken into consideration here.
Could be less working surface area on your rack idea perhaps?
Plus not all the rack has surface area contact?
Never worked out coefficiency of a rack.
Have to pay more attention to the watertight doors methinks.
Still can't picture a rack thrashing about in a crankcase though.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Big Pete
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Re: increasing fuel efficiency of engine

Postby Big Pete » Mon Dec 04, 2017 12:19 pm

From your first Post: -

[[i]i]"a)The process of the combustion of the mixture begins before the piston arrives at the “top dead point” and it means that the movement of the piston to the ”top dead point” is counteracted by the total pressure: the sum of the degree of the compression, and the increasing pressure of the inflamed mixture, and that results in loss of the power."
[/i][/i]
It is true that combustion starts just before TDC, this is deliberately done for two reasons,
1) There is an ignition delay after fuel is injected before combustion starts, and combustion itself is a "Chain reaction", it starts slowly and grows exponentially, therefore to achieve maximum pressure just after TDC injection has to start well before TDC and combustion will start a little later but still before TDC in order to achieve optimum efficiency. Modern Electronically controlled common Rail fuel injection systems achieve this very well, under all running conditions, while simple mechanical injection systems could only be optimised for one type of fuel, at one speed and load.
2) As the piston is being pushed upwards by the connecting rod on the compression stroke the bearing surfaces of the bottom end and Big end are all under load, at TDC the crank changes direction and if there was not enough pressure on the piston, both the connecting rod and piston would continue upwards under the influence of inertia, until all the clearance in the bearings had been taken up and the BE bearing hammered on the Crankshaft journal and the Top End bearing hammered on the Gudgeon Pin. When the engine fired, and the pressure started to force the piston down to transmit force to the crank, the bearings would be hammered again. This would obviously be very damaging to the engine, and has to be avoided by keeping the load on the bearings in the same direction throughout the cycle rather than having it alternating.

.b) The change of a coefficient of the tangential force to the force working on the piston from the value of 0 up to the value of 1. 2.The engine of the internal combustion uses in the best case scenario only 75 % of the fuel and 25 % goes in the exhaust pipe and the muffler. Namely, this part of the fuel is burning in the catalyst. But catalyst is the very expensive device and it requires the substantial part of the powerful of the engine for pumping the fuel through a dense net of the surfaces of the catalyst. There are several reasons for this phenomenon and one of them is the very short time of the process of the burning. The average time of the burning of the fuel in the cylinder is 0.001sec. In other words the effectivity of the engine depends on the length of the motion of the piston. But the length of the motion of the piston is directly related with the size of the crankshaft and this relationship limits the length of the motion of the piston.

I have never heard of any engine that is 75% efficient. When I started as an Engineer we used to say that, for a large marine engine 1/3 of the Chemical Energy in the fuel is converted into useful Mechanical Power, 1/3 into waste heat in the exhaust gas and 1/3 into waste heat in the cooling water. At that time typical car engines were about 15% efficient, less efficient that a coal fired Scotch Boiler powering a triple expansion steam engine.That is why using this waste heat is so important to Plant Efficiency as opposed to engine efficiency. The improvements over the last 45 years have increased Engine efficiency to about 40%.
If the engine is being operated correctly no fuel should be burnt in the catalyst, and it should not require a great deal of power for the exhaust gas to flow through the catalyst. Obviously the catalyst causes a slight pressure drop in the gas flow and hence a slight increase in the back pressure at the engine, reducing its efficiency slightly and raising the exhaust temperatures slightly. If there is a significant pressure drop the catalyst is dirty and requires cleaning.
As I have said before, the tangential force does not cause a significant loss of power/ energy, because there is no movement in the direction of that force. The friction between the cylinder and piston may be slightly increased by this transverse force, but not sufficiently to reduce the efficiency of the engine.

The catalysts are fitted in the exhaust Gas system, not the fuel system so I am not sure why you are talking about pumping fuel through the catalyst?

The duration of combustion does not greatly effect efficiency, we are not using the force of the explosion to drive the piston, we are releasing energy (through the combustion process) to heat the working fluid (the excess air over the stoichiometric ratio) as the air is heated it tries to expand, generating the pressure that drives the piston. Also, as has been pointed out, modern engines using Electronically controlled Common Rail Fuel Injection, can inject fuel as many times as desired throughout the power stroke, so combustion duration can be maintained over longer periods by making multiple sequential injections of small quantities of fuel, starting before TDC and continuing throughout the power stroke.

I agree that the longer the length of the stroke, the more the Gas is expanded and the less energy is passed into the exhaust pipe, that is why some large 2 stroke engines for big Tankers have a 2 metres long stroke, and they use a conventional crankshaft without any problem, but usually they run at about 60 RPM flat out to optimise the propeller efficiency. However, with a shorter stroke engine that energy can be recovered in an exhaust gas boiler or an exhaust gas power turbine. However, if the expansion stroke were too long there would be insufficient energy in the Gas for it to exhaust properly, there is a limit to how far you can increase efficiency by lengthening the stroke, there comes a point where the pressure is so low that it does not overcome friction in the engine!

"3. The significant influence on the fuel efficiency makes also a short time for the exhaustion of the burned mixture. It means that the new portion of the fresh air-gas mixture is mixed with remains of the burned mixture. These phenomenon decreases the powerful of the engine."

The short time for the exhaust gas to leave the cylinder is common to all 2 stroke engines and one reason why 4 stroke engines tend to be more more efficient, although they tend to have a lower power to weight ratio.
Opposed piston engines have Uniflow scavenging as do the large poppet valve engines like the Sulzer RTA and later engines. Until the demise of Doxford, Sulzer always claimed that there "loop scavenging" design gave superior scavenging to Uniflow, however, it is evident that Uniflow scavenging avoids the problem of the New charge of air mixing with the previous air/ fuel charge.


"4. When the piston is at the “top dead point”, the compressed mixture is ignited. It is known that for the full and complete combustion of the fuel vapor desirable the high temperature and the high pressure. But immediately, when the piston passed the “top dead point”, it starts to move down with the significant increasing of the space above the piston. With the spread of the flame front of the mixture in the combustion chamber the first portions of the mixture will burnt at the high temperature and the high pressure. But the latest portion of the hot mixture burns under the condition of the sharply declining of the pressure and the falling of the temperature. For this reason, the part of the mixture does not have the time to burn or not burn fully."

This is simply not true!! I have never heard of modern engines pumping excess fuel into the exhaust pipes, until the fuel system is set up incorrectly, even high speed engines have plenty of time to burn all the fuel.

I have spent a considerable amount of time searching for a way to make you understand that the angle of the crankshaft does not effect the efficiency of the engine.
The best analogy I have come up with is Electrical. In A.C. circuits driving Electric Induction motors the current flows out of phase with the voltage by an angle known as the phase angle. The product of multiplying the Voltage with current that is in phase with it (Cos. Fi of the total current) is the true power, in kW. The Re active power, the Volts multiplied by the vector of current acting at Right Angles to the Voltage, is known as Wattless power, because it does not have any power, because no Voltage is acting in phase with it.
It is similar with the resolution of forces on the connecting rod, you resolve them into a force acting in line with the movement of the piston, which produces true power, and a force acting against the side of the cylinder, which does not produce any power and could also be described as Wattless".

Merry Xmas.

Big Pete
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Merlyn
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Re: increasing fuel efficiency of engine

Postby Merlyn » Tue Dec 05, 2017 3:38 am

Plenty of workshop manuals being swallowed here it would appear.
I have never encountered a 25 % fuel burning in a Cat. Intentionally happening. Only in the case of faulty injectors/ pintles whereby the nozzle end containing the holes has been damaged and the damaged nozzle ends gone on out the exhaust valves via the uptakes thereby caused by no atomisation to occur, only hosing in that particular cylinder.
Loads and loads of smoke here as the combustion is meant to occur in the cyls. and not in the exhaust system as no effort can be transferred to the crank via the exhaust only excessive smoke to atmosphere.
And a lot of smoke and crap too.
Not good on a passy ship or indeed any other ship.
However I have encountered deliberate fuel injection into a Cat. system.
Particularly on systems fitted with DPF.
Injection is timed via the ECU's brain, not on every stroke but on regular spaced out intervals as the particular ECU 's manufacturer deems fit.
Some systems inject Addblue and the like but some systems inject fueloil.
Just a squirt now and then after TDC to burn off the carbon build up on the CAT face but when you stand alongside the engine when the DPF ing is going on you have to wonder just how efficient the as and when squirt really is.
Probably the scenario, especially at night stood alongside the exhaust discharge to atmosphere is the closest I will get to seeing a live volcano blowing, scary all round.
With no control over it once you commence the process back ( retarded ) goes the injection system electronically , obviously up climb the temps probably over normal running readings and up cranks the rpm.
Not nice to be stood alongside the engine during this process.
Some manufacturers now have this DPF ing system built into its ECU so you don't need your expensive electronic FCR for you to start the process.
MIL light comes on, press a button and it's off on its own.
Red hot carbon discharge here all right, firework display.
You can easily measure the backpressure pressure in a CAT system, we have a kit whereby you drill the outer exhaust casing ( and / or inner one ) and insert a one way valve ( loads of them in the kit ) bit like a large pop Rivet which is left permanately in the system upstream/ downstream of the O2 sensor/s ( if the system has two fitted ) thus on some systems four inserts are fitted to enable four sampling points to be accessed.
A gauge with a gas tight airline/ hydraulic fitting ( collet type jobby ) is clipped onto the bleed nipple type fitting and pressure readings recorded.
So advance warnings of DPF ing can easily be recorded and logged before they actually need doing.
In passing it is interesting to note that as a by product the old Cat systems have superseded the beer money syndrome whereby we don't see much white metal nowadays but the platinum present in the Cat is worth, prorata much more than the dear old white metal ever was for scrap.




,
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Re: increasing fuel efficiency of engine

Postby Serguei » Thu Dec 07, 2017 10:59 am

To Big Pete
I have never heard of any engine that is 75% efficient. Of course you are right. As usual say that the coefficient efficiency of the engine consists from two meanings, namely, a thermodynamic and a mechanical. First meaning show what part of a warm is using for the useful activity and what part goes in the environment. Second meaning, mechanical coefficient; show what part of the activity of the engine uses for overcome the mechanical resistance in the engine. But I think that very important to know what part of the fuel is burning with useful and creating a warm and a volume of the gas and what part of the fuel is not burning fully and goes in the an exhaust pipes like emission.
I don’t share your opinion that “if the engine is being operated correctly no fuel should be burnt in the catalyst, and it should not require a great deal of power for the exhaust gas to flow through the catalyst”. From 1975 in the USA is a mandatory rule that every vehicle must be equipped by the catalyst. It means that the problem of the fully burning of the fuel in the engine is not solved. The incomplete combustion of the petrol gives rise to carbon monoxide and various Volatile Organic Compounds (VOCs). The catalyst has a density net which is resistance for flow of the exhaust gas and therefore there is a loss of the power.
I think that you will agree that the tangential force changes its meaning in accordance with changing of an angle of the crank. Using equation we can define the meaning of the tangential force for any angle.
T = F sin (ɣ+β)/cosβ;
ɣ angle between axis of the crank and axis of the piston;
β –angle between axis of the piston and axis of the connecting rod;
F= S x P;
If F=1, then we can calculate tangential force, T;
ɣ =0 β =0; T =0
ɣ = 15 β =2.97 T =0.3
ɣ = 30 β =5.74 T =0585
ɣ = 45 β =8.13 T =0.8
ɣ = 60 β =9.97 T =0.945
ɣ = 75 β =11.14 T =1.02
ɣ = 90 β =11.54 T =1
ɣ = 105 β =11.14 T =0.91
ɣ = 120 β =9.97 T =0.785
ɣ = 135 β =8.13 T =0.61
ɣ = 150 β =5.74 T =0.41
ɣ = 165 β =2.97 T =0.2
ɣ = 180 β =0 T =0
The average meaning of the tangential force (T τ) for this set of the meaning will be
T τ = Σ T ı /n.
In our case T τ=0.58.The comparison of meanings of tangential forces of the conventional engine and forces in the suggested model shows that in the suggested model the average tangential force is greater in 1.72 times than in the conventional engine.

Best regards
Serguei

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Big Pete
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Re: increasing fuel efficiency of engine

Postby Big Pete » Thu Dec 07, 2017 12:30 pm

Hi Serguei,

This is a Marine Engineering website and I don't claim to know much about Road vehicles, I have only worked on Marine Diesel Engines. Petrol Engines are notoriously inefficient even if run on High Octane petrol to enable higher compression ratios and peak pressures to be used. The Peak Temperature and Pressures will always be lower than that for a Diesel engine and hence the efficiency will be less (Carnot cycle).

With regard to the Tangential force you keep talking about, I still do not believe that that has any effect on the efficiency, because no work is done and no power is lost. The mathematics is very pretty but, I believe it is based on a flawed understanding of how an engine works.

When the piston is near TDC a large linear movement of the piston is required to turn the crank a small angle, as the piston moves down towards Mid stroke the distance becomes less in relation to the crank angle as the Torque increases (the lever arm of the crank throw moves towards the horizontal). The changes in Torque and Linear speed cancel each other out and maintain a more uniform power output than you appear to think.
The pressure inside the cylinder is in part determined by the effort required to move the piston, which in turn is based on the crank angle.
With your novel engine the resistance to movement of the piston and the velocity of the piston would be more uniform than a traditional engine.
With a traditional crankshaft engine effectively the mechanical gearing between the piston and crankshaft varies, this just means that pressure inside the cylinder will vary in a different relationship to the piston position than in "your" engine.

To compare the two engines it would be necessary either to build and run two engines with identical bore and stroke.

Or to make a computer simulation that did the same job.

Keep on reading and thinking Serguei, and all the best for a Merry Xmas.
It is always better to ask a stupid question than to do a stupid thing.

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Re: increasing fuel efficiency of engine

Postby Serguei » Fri Dec 08, 2017 10:43 am

It is known very interesting fact. The newest model of the gas lawn mower throws into an environment in 93 times more emissions than the newest model of the car. It is not surprisingly because is not exist laws which regulate emissions of the lawn movers. As it is known the lawn mower is equipped by 2 stroke engine.

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Merlyn
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Re: increasing fuel efficiency of engine

Postby Merlyn » Sat Dec 09, 2017 7:39 am

Serguei,
No matter how many workshop manuals / formulaes one swallows the irrefutable fact concerning the stated 25% unburnt fuel being deposited into the Cat on both petrol and diesels cannot possibly take place for one very simple reason.
The management system on both types of engines will, to protect the engine cause the MIL light to come on the control panel and will immediately place the engine into the Limp Mode ( Limpo as we all know it by )
Should you attempt to knock the light out with the FCR apon start up you will find it will immediately revert back to Limpo.
Just above tick over rpm and no power, crawl / limp home situation.
The air/ fuel ratio ( the lean burn " Overstoichiometric ratio ) to which the ECU has been programmed to is 14-7 to 1 throught its rev range, load range, temperature range etc and this is primarily sourced from its Lambda sensors, i.e. It's Oxygen sensors ( known in the trade as its "Oxy Sensor " in order to reduce NOx ( Nitrogen Oxides ) discharge to atmosphere.
An overload situation of 25% of unburnt fuel in the Cat is very very high reading indeed, when the Lambda / Oxy sensors tell the ECU of that explosive situation present in a Cat running ideally at 900-00 degrees C plus an immediate shutdown to Limpo would occur to prevent any engine damage.
Normally I have found from personal experience an Oxy failure will not, unlike some other sensors cause a complete shut down resulting in a non start situation although a 25% dumping of unburnt fuel is indeed a dangerous situation indeed.
With newer engines it can be very difficult, even after purging the system to obtain an emissions reading at all and as time goes by we have to update our smoke meter machines hardware to cope with it all, at the present time on nearly new engines sometimes we cannot get a reading at all, even apon a cold start up ( the ideal engine lubeoil temperature being 80 degrees) as laid down by the smoke meter manufactures.
As I have previously stated there is far more emissions measured output from a normal tobacco / cigarette smoker than a lot of new measured Diesel engines.
For authorized smoke emission tests over here using a currently certificated smoke meter an accepted reading on the first test is passable but should the first purged test not be acceptable then the smoke meter will ask/ demand five tests in total before arriving at an average reading devided of course by five.
Even pre CR a 25% load of unburnt fuel in the exhaust system is to invite an explosive situation to be present and splitting the silencer open akin to a bean can exploding.
Sadly these sensors are rather like us, they time expire.
In writing I have fitted much cheaper ones which have caused a lot of problems with premature failures.
Chinese ones.
Repeat jobs are far from ideal in more ways than one.
So Bosch or predominant makes are fitted although it is rumoured that they are also made in China, but to a higher standard. So we are told.
Testing Lambda/Oxy sensors?
Back in the early eighties when they came out over here petrol first then later diesel the common mistake was to FCR the system for an indicated fault of the MIL light on for it to clearly display O2 sensor not working.
But which one?
In the manifold, times two for a V configuration or the ones in the exhaust up both stream and downstream of the Cat
Easy way was to test them by scoping them .
So the faulty one was found by analyzing the scope pattern against the one held in your library, the library in your head or, if not remembered the manufacturers one.
Change the faulty sensor, sometimes seized solid in the manifold and new one fitted using high melting point copper grease.
Restart the engine and up throws the FCR with the exact same code depicting O2 sensor problem.
Scope again all O2 sensors and the new one just fitted comes up as the fault.
Must be a duff new one, had this loads of times over the years with injectors and the like so in with another O2 sensor.
Restart and guess what?
FCR throws up same code.
How can this be?
Took me a lot of hours/days in the early days of the eighties to work out the correct answer.
The early O2 sensors were three wires and the later ones were four wires, the fourth wire being the heater circuit to enable better cold starts and earlier smoother loading to be applied to the engine.
The FCR machine clearly showed the sensor to be faulty and not working correctly and as such not enabling the Cat to be Lit.
The scope readings backed this up.
And yet despite two new O2 sensors the fault remained the same?
Many, many hours later I finally figured it all out.
The very low voltage ( typical values being 0.2 v D.C. I.e. 200mv D.C. Being a rich mixture whilst supplied to the ECU to tell it to " lean me off down here " or "it's cold down here, richen me up please " was not " switching " correctly indicating a loom fault between the O2 sensors and the ECU thus causing the fault.
This was found by a diagnostic procedure which to date has proved again and again to be an excellent diagnostic test.
The " Wiggle Test " .
By wiggling the loom, unclipping it etc the source of the fault was finally revealed exactly.
Yes, the O2 sensor WAS faulty, but only because the below one volt necessary ( the voltage varies when richening'mm' as apposed to leaning off ) was fluctuating owing to the intermittent fault in the loom.
Now repaired, on this particular installation the sensor could actually be heard switching if you put your ear alongside it.
This type of happening was, back in the early eighties to be my introduction to CR and was an early indication for one not to take things for granted and as opposed to the pre CR days still makes for a lot of problems concerning parts replacement Unnecessarily so in many cases and I have found that a lot of highly skilled engineers whom I have worked with for many years actually hate CR problems owing to the FCR telling them a component is at fault when in truth it is not.
So over here the saying the cause not the fault predominates CR diagnostics.
So I do hope that I have not spoilt Seguei's Xmas but don't blame me, I never invented the O2 sensor, Robert did.
Robert Bosch that is.
So in conclusion it is he, not I who will just not permit any CR engine, diesel or petrol to run with a 25% injection of unburnt fuel into a Cat equipped system engine. The Lambda sensor would be on overtime in a futile attempt to desperately lean off the situation but with that high an input into the Cat. a Limpo shut down situation would be inevitable. Typical transmitted values to the ECU would be 0.2v D.C. i.e. 200 mv representing a rich mixture as opposed to 0.8 v D.C. i.e. 800mv D.C. representing a lean mixture.
Both of these being a closed loop type feedback to the ECU to enable the program written in the ECU to control fuel injection and amounts of fuel being injected.
The whole idea is to reduce the NOx ( Nitrogen Oxides ) discharges to atmosphere.
Basically I have encountered two types of Oxy sensors here, the Zirconia Ceramic one, ( thin layer of Platinum ) and the Titania model.
So I guess it's back to the drawing board for Serguei on this one?
So it's maybe time to think about temporarily shelving all those workshop manual / formulae downloads and maybe venture forth with the pinkies into the practicable world of diagnostics engineering and endure the practical/ on site problems /hassles concerning CR and subsequent emissions concerning same?
However my considered opinion of it all is that it's A case of isolating the CAUSE of the problem and not just taking the SYMPTON at face value and after many years of CR and all it's associated problems therein I approach every new job with much caution as it really can be a minefield area to enter.
However Serguei, panic ye not as we say over here, all said and done have a good Xmas, keep your fuel ( ale that is ) / air Overstoichiometric ratio to 14-7 to 1 correct over the festive period and you will be firing on all six, no problem.
PS
My lawn mowers a four stroke, all five
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

Serguei
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Re: increasing fuel efficiency of engine

Postby Serguei » Mon Dec 11, 2017 6:30 pm

Merlyn and Big Pete,
I am so thankful to you. You dedicated your personal time for our discussion . Thank you for questions and critics.
Merry Christmas.


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