OT: adding water to fuel

Half-Nutz, I cut and pasted your very words, even including the misspelling. I had no intention of misrepresenting what you said. However, concerning your next line...

...that's just another mistake. In a spark-ignition engine, unlike a diesel, the throttle pedal does not control the flow of fuel. It controls the flow of air, and an air-mass or air-pressure sensor then controls the flow of fuel. (Except for a BMW Valvetronic engine. Unless you're talking about one of those, forget I brought it up. d8-)) In today's engines this happens via the computer (ECU), and a couple of other things are computed to determine the exact amount of fuel to inject, but your statement is just plain wrong. You NEED to control airflow with a throttle, because you don't directly control fuel flow in a SI engine. THAT's why I didn't copy your next line, not because I was misrepresenting what you said.

If you had a spark-ignition engine with no air throttle -- in the carburetor, or in the throttle body in the case of an injected engine -- it would just run away and blow up. That's with or without hydrogen mixture or injection.

So does a diesel. Unless you have a carburetor on the SI engine, with a venturi to restrict air volume and increase velocity, there is no reason for a SI throttle body to be any more restrictive than the air-box or manifold intake on a diesel -- when both are running at full throttle.

HOWEVER...and it's a big "however," you and I are talking about different things, and I realize that the way I've described this is not clear and probably from any angle mistates the issue. (See Note Below if you want to argue this some more.) I'm saying, first, that your hydrogen-enhanced engine needs an air throttle anyway, so there is no gain there. That's why I called your statement a mistake. I'm also saying something else, discussed in Note Below, but I'll ignore that for now. For purposes of this discussion I'll agree that, yes, if you can get rid of the air throttle in a SI engine you can reduce pumping losses to something equivalent to those of a diesel. But you can't get rid of it (with any production engine except BMW's. For the fussbudgets, throttleless, adaptive Atkinson and Miller cycle engines don't exist in production). The hydrogen won't help you get rid of it. And that's because of the way the fuel injection or carburetion system works in a SI engine.

By getting rid of the restriction in a carburetor venturi. At full throttle, a fuel-injected engine has pumping losses on the same order as those of a diesel. At part throttle, your hydrogen-enhanced engine needs a throttle just as much as a regular SI engine, so you're not gaining anything in terms of pumping losses.

It doesn't. What matters is whether there is a venturi.

Right.

But you CAN'T eliminate the throttling of air in a SI engine (previous caveats apply). It will go "boom." Or "death-rattle clank."

-- Ed Huntress

NOTE BELOW: What I said in an earlier message, confusingly, is that pumping losses in a spark-ignition engine are small compared to the losses due to reduced-compression thermal-efficiency losses at part-throttle. I see that SAAB's research indicates a 30% gain in fuel efficiency in normal driving cycles with their variable-compression research engine. That means a regular SI engine has 30% less thermal efficiency in normal driving cycles because of its fixed (nominal) compression ratio. That agrees roughly with what I remember from the MIT engine books, which I am not going to dig out of the attic right now.

If you want to continue arguing this point, find data that shows that

*intake* pumping losses at normal driving cycles produce a 30% loss in fuel efficiency. If you can (because I'm sure it's less than that), I will print these words out in 14-point Times Roman on 22-pound white bond paper and eat them while videotaping the event. Then I will post the video to the dropbox. Promise.

Total pumping losses won't do it: they include compression losses and exhaust-pumping losses, and they're roughly the same for SI and for diesel. And horsepower loss isn't it. That's the result mostly of thermal efficiency losses from part-throttle operation. We're talking intake pumping losses and their energy consumption or, more directly, their effect on fuel efficiency here, in a normal driving cycle -- not coasting downhill with the throttle closed. d8-)

wrote: Something a bit more sophisticated than simple electrolysis would

^^^^^^^^^^^^^^^^^^^^^^ When hydrogen burns, it releases heat, and produces water. Simply from a conservation of energy standpoint, you need to put that energy back into the reaction to separate the water into hydrogen and oxygen. It can come from electric current, or it can come from some yet unknown source at some future date. But the reaction cannot take place without a big supply of energy. Even if you could find some wonderful catalyst to make the reaction take place with 100% efficiency, you have to provide the same amount of energy to break a water molecule as you got by burning a hydrogen molecule. God doesn't let us break the laws of nature.

Once again, you completely ignore what I said, misquote it, and try to evade.

The hydrogen enhanced engine CAN run without a throttle plate in the intake. You control the power via the amount of fuel.

HOW can an engine without fuel, run away, and go Boom? Are you proposing perpetual motion, to wind up the SI engine, without adding fuel to it?

With the Hydrogen addition, the throttling of air is not required, similar to a diesel. The hydrogen allows a very lean burn.

With either Fuel Injection, or a carbuerator, the throttle plates create an air restriction, to control the power level. There is a partial vacuum behind the throttle plate, if it is a carb or a FI motor. The idea of the venturi vacuum being absent on the FI motor is of absolutely no consequence to conveying this concept.

And WHERE did I claim a 30% or any other percentage gain? Where did I even claim that this works?

You are determined to attack an idea but keep getting tangled up with irrelavent factoids.

Your first volley was about the inefficiency of generating Hydrogen, then burning it. Thus concluding it must be scam!

I could take that same exact logic, and apply it to the sparg ignition system, and PROVE by your exact same logic that it must truely be scam of huge proportions. The alternator take power to generate electricity, it is wasted in the coil, and that tiny spark cannot produce enough heat in the cylender to drive the alternator. Therefore, it MUST be a scam.

And yet, we know that a spark is quite useful to light the actual fuel, not drive the motor in a perpetual motion scam.

So too, the hydrogen can be used to burn nearly eny fuel in a SI/ hydrogen cycle, allowing us to think of new ways to operate the motor.

I can't imagine this being a bolt on accesory! It would be an integral and fundamental change to the design of the motor for maximum gain.

Your initial argument about effeciency, although accurate, is ABSOLUTELY IRRELAVENT to the concept of using the hydrogen as a catalyst for ignition, thus allowing a SI engine to operate in a whole new way.

Now, if this is all feasible, and workable, I don't know.

But I think it is best to understand what you are attempting to discredit, and get your facts and understanding of it correct, before trying to attack it.

Does this sound more intersting now?

Water injection systems were old add-ons also. But the hassle of keeping the water tank full put off most folks and they did not sell that well. This was in the sixties and there were indeed some high compression muscle cars out there that benefitted from WI. But again too much hassle for the small gain.

Actually for those of us who were running very high compression, and then couldn't get decent fuel, it was the only game in town. Hard to characterize it as "too much hassle for the small gain" in that without it I couldn't drive the car. Of course we didn't do it for hydrogen benefits, rather it was for knock control.

Adding hydrogen might allow a leaner burn, but it would take a lot of hydrogen to make much difference. With no throttle plate in a spark-ignition engine, the mixtures at low or moderate power settings are going to be really lean and the molecules are just too far apart to sustain any chain reaction. The diesel gets around that by injecting the fuel in when compression is almost complete, so that burn happens instantly as the fuel enters; it didn't have any chance to spread out into the entire air charge as with the carbureted or manifold-injected gasoline engine.

Dan

The catalyst is not availble to the general public.

wws

Not trying to break any laws. Only a small amount of hydrogen would be required to enhance the burn of the fuel mixture, and at close to 100% cracking efficiency it MIGHT become viable. Ena\hancing the burn would mean an improvement in efficiency of the engine, and could POSSIBLY allow the engine to run significantly leaner without the problems normally encountered trying to run lean. Could POSSIBLY allow a throttleless Fuel Injection system with gasoline, similar to CRD.

But the "gain" was in being able to run old high-compression musclecar engines without detonation. I never heard they did anything for fuel economy, except that they'd allow you to advance the spark timing and that would help if you otherwise had to retard it just to run at all.

-- Ed Huntress

wrote: Not trying to break any laws.

^^^^^^^^^^^^^^^^^^^^^^^^ Clare, I feel like I am chasing you around in circles. In my first statement I said, "Let's grant for the sake of argument that adding a little hydrogen to the fuel mix could act as a combustion catalyst or igniter, or whatever." My assertion was that the way to have hydrogen on board would be to have it in a cylinder from another source. You are now arguing in favor of the proposition that I granted in the first place.

But if you insist on arguing about leaning out an engine without a throttle, by controlling the amount of fuel let's look at that. The engine would have to run from idle to full power on the same volume of air. You're asking me to believe that it could be feasible for an engine to idle on a mixture that lean because there's a little hydrogen in the mix. Here's my technical answer: "Fat chance." Flame can propagate in a mixture only if the molecules collide often enough to make the temperature go up. When the fuel is extremely dilute, whether it is gasoline or hydrogen or a mix, that won't happen.

It didn't really give you much increase in H.P. On a P&W 4360 it gave about 7% increase (from 3500 to 3750 H.P.) and for only a limited time.

Bruce-in-Bangkok (correct email address for reply)

Pratt&Whitney said that the water turned to steam, thus cooling the combustion chamber and allowed a leaner, thus better burning, mixture, to be used. Since the carbs were overhauled at Depot I can't give you any specifics but they certainly taught us that when you pushed the throttles "over the huimp" to max power that the mixture was leaned and the water was turned on. Which makes sense as airplanes don't worry much about fuel economy on take off.

Bruce-in-Bangkok (correct email address for reply)

Hey smart=ass. Take a look at what Audi is doing TODAY. see:

injection THROTL-LESS Spark ignition engine WITHOUT Hydrogen augmentation.

Do not say it can not be done. I've been around the block a few times as an automotive technician. There is a lot more "impossible" stuff going to happen in the next 5 years!!

Water injection in airplanes, at least supercharged ones, involves things that usually aren't involved in car engines. First, blown, large-cylinder aircraft engines used "blowdown" to keep them cool. That wastes a lot of fuel. If you can cool the cylinders with water, it's a lot cheaper than cooling them with gasoline.

Second, the large cylinders, supercharged or not (are we talking about a Wasp engine here?), are prone to detonation, so cooling the combustion chamber allows them to run with higher compression and with more spark advance.

Some of the same thing can happen at the margins with big, high-compression car engines, but the ones that were designed when we had higher octane leaded fuel didn't benefit from it -- until high octane fuel became special stuff that was hard to get.

-- Ed Huntress

Wow, that's an impressive piece of engineering. I see that they're claiming a 15% fuel-efficiency increase, between the lean burning and the lack of throttling (pumping) losses. I wonder how much is attributed to pumping, then?

I have some figures I've picked up elsewhere, and I'll have more info on it tomorrow or Sunday.

-- Ed Huntress

Hardly any source I've seen has put a value on it, however, and most of them are disposed to overestimate it because they're selling something, or they're promoting an engine, that reduces it.

The sources I *have* seen indicate, on the average, 9% - 16% horsepower loss in normal cruise. But I dug out my copy of Taylor's _The Internal Combustion Engine in Theory and Practice: vol. 1, Thermodynamics, Fluid Flow, Performance_, found the relevant information, and I'll be running some numbers before the weekend is over. Meantime, I've gotten two figures for the loss of thermal efficiency from lower effective compression ratios at part throttle, and they're heading up around 30%. I'll be able to do some calculations there, too.

I've been driving since 1963 so I'm familiar with it. I'll have some facts to go over regarding it.

-- Ed Huntress

Oh, yeah, if you modify the HECK out of the entire engine, or at least the intake/fuel system, then maybe! Yes, pumping loss is a huge waste of energy, I can't BELIEVE we are still using the damn Otto cycle after stratified charge engines have been around over 40 years! Once you get the engine running without the throttle, and control power output with fuel flow only, you should be seeing a major improvement. The guys flying injected Lycoming engines have come up with a way to balance the fuel flow to the individual cylinders better so they can run on the "lean side" and if it is done right they get remarkable improvement in cruise efficiency and actually reduce engine operating temperatures in that mode. They are not using any additive like Hydrogen, but careful fuel metering balance to all cylinders is the key. They do have a throttle, but usually run it pretty far open at cruise.

I had not heard of this, but it makes some sense.

But, buying something at the local Auto-Zone for $19.95 that has a bottle of water and some electrodes you hook to the battery and put on an otherwise unmodified car is certainly a scam.

Jon

Of COURSE, at WOT, there's no pumping loss. But, when you cruise on the highway, or around town, the throttle is quite closed, you have a pretty low manifold pressure (equals high manifold vacuum) and the pumping loss is significant. You can't do this on modern cars with computerized transmissions, but on the old ones you could floor it, cut off the ignition switch and then after a bit lift your foot off the gas, and feel the pumping loss act as a brake. It was pretty surprising to feel how much braking there was even at partial throttle.

Certainly, the hot gas flowing out the exhaust is the worst energy waste there is, but with IC engines, there is only so much you can do about that. Pumping loss is fairly easy to reduce in a variety of ways (variable displacement schemes, stratified charge injection, the much-coveted HCCI that everybody is tinkering with in their secret labs, or just go Diesel).

Jon

I'm not familiar with the term "blow down" but all gasoline fueled aircraft engines I have been around ran richer then optimum at higher power settings for cooling.

On, at least on the last three or four water injected engines that the Air force used the water cooled the combustion only during maximum power settings. For all power settings below that detonation was controlled by mixture settings. Spark advance and compression was a fixed value on those engines. In fact the only variable ignition timing I ever saw on a military aircraft was only a devise to retard the timing for starting. By the time you hit normal idle speed it was no longer active..

The A.F. never had many problems getting high octane fuel... Bruce-in-Bangkok (correct email address for reply)