Fuel Injection on the Lockwood-Hiller?

[Bruno Ogorelec]

Not only is it going to be entrained excessively in the outflow.

Er... Bill, you can't be saying what I think you are saying. What outflow? During the intake phase, there ain't no such thing as outflow. Fluids are traveling from the two ports towards the combustion chamber.

but it will never be able to take advantage of the latent heat farther down, for conversion from atomized liquid to vaporized mixture.

Um... why not? What on Earth can prevent it from doind so? Its travel towards the moment of combustion is going to be increased both in length and distance. If anything, it will pick up more heat and be vaporized more completely.

Also, the joint between the intake(s) and the combustion chamber HAS to be highly turbulent, due to the discontinuous area changes there--and this contributes significantly to the mixing of fuel and air.

But, injecting fuel into the intake stack has nothing to do with this. I did not propose to do away with the sharp transition or turbulence. I proposed to have the fuel injected at a different place.

As even this excellent example of a Locky shows, the primary combustion zone is at least part-way down the chamber, and gives room for good fuel preparation at the head-end.

It need not have much to do with injector location. I can show you pictures of a Thermojet with injection at the intake mouth that has a perfect heat distribution -- the entire chamber is glowing red and so is a part of the exhaust, while the intakes and the rest of the exhaust are cool.

[resosys]

I think it would be an excellent technical effort for somebody to experiment with and record the results of changes in fuel-supply locations--all with the same engine. Lots of work.

I am planning on building a test engine within the next year. The current plan is to install plugs in *many* locations throughout the combustion chamber and intake tube. We're going to strive to keep the internal walls as smooth as possible, even with the plugs, then add or move fuel inlets for the various tests. We're hoping to run both propane and some liquid fuels and try to work out optimum locations for both.

One of our primary concerns is reliability. We use the pulsejets in shows and they need to start every time and run well. Propane works well for this, but we want a lot more pop.

Also, in the works are two very large Lockwood Hiller pulsejets. Fuel injection into the front combustion chamber cone like my image above will probably not be sufficient. Liquid fuel or many more propane injectors, closer to the intake tube will probably be required.

Has anyone done any work with auto fuel injectors? We've started talking about setting up some tests with injectors at the shop.

Also, has anyone experimented with vortex generation or other diverters in any area of a pulsejet engine?

Thanks,

Chris

[hinote]

Er... Bill, you can't be saying what I think you are saying. What outflow? During the intake phase, there ain't no such thing as outflow. Fluids are traveling from the two ports towards the combustion chamber.

But, during the combustion phase, the intakes are converted to thrust-producing exhausts. With the fuel supply further into the engine at least part of the outflow will be re-entrained as it begins to breat in again.

but it will never be able to take advantage of the latent heat farther down, for conversion from atomized liquid to vaporized mixture.

Um... why not? What on Earth can prevent it from doind so? Its travel towards the moment of combustion is going to be increased both in length and distance. If anything, it will pick up more heat and be vaporized more completely.

Remembering that the combustion chamber is only filled to the extent of something like 20%, I don't think it's wise to move the fuel source too far back. You're going to end up with intake tubes filled with fuel/air mixture at the point of combustion---and these are going to go off like separate entities (if they go off at all) and not contribute anything to the needed primary pressure event in the combustion chamber.

As even this excellent example of a Locky shows, the primary combustion zone is at least part-way down the chamber, and gives room for good fuel preparation at the head-end.

It need not have much to do with injector location. I can show you pictures of a Thermojet with injection at the intake mouth that has a perfect heat distribution -- the entire chamber is glowing red and so is a part of the exhaust, while the intakes and the rest of the exhaust are cool.

Based on my (very limited) experience with liquid fuel delivery, all you're going to get with atomizers at the inlet mouths is one or more very wet intake tubes. The point is, the zone where the intake tubes meet the combustion chamber is the perfect location to dump atomized (but still liquid) fuel because it has the 2 things necessary to convert it to vaporized, mixed fuel/air: Heat and turbulence.

Well, it makes for a lively discussion, and various viewpoints...

Bill H.
Acoustic Propulsion Concepts, Inc.

[Viv]

Er... Bill, you can't be saying what I think you are saying. What outflow? During the intake phase, there ain't no such thing as outflow. Fluids are traveling from the two ports towards the combustion chamber.

But, during the combustion phase, the intakes are converted to thrust-producing exhausts. With the fuel supply further into the engine at least part of the outflow will be re-entrained as it begins to breat in again.

but it will never be able to take advantage of the latent heat farther down, for conversion from atomized liquid to vaporized mixture.

Um... why not? What on Earth can prevent it from doind so? Its travel towards the moment of combustion is going to be increased both in length and distance. If anything, it will pick up more heat and be vaporized more completely.

Remembering that the combustion chamber is only filled to the extent of something like 20%, I don't think it's wise to move the fuel source too far back. You're going to end up with intake tubes filled with fuel/air mixture at the point of combustion---and these are going to go off like separate entities (if they go off at all) and not contribute anything to the needed primary pressure event in the combustion chamber.

As even this excellent example of a Locky shows, the primary combustion zone is at least part-way down the chamber, and gives room for good fuel preparation at the head-end.

It need not have much to do with injector location. I can show you pictures of a Thermojet with injection at the intake mouth that has a perfect heat distribution -- the entire chamber is glowing red and so is a part of the exhaust, while the intakes and the rest of the exhaust are cool.

Based on my (very limited) experience with liquid fuel delivery, all you're going to get with atomizers at the inlet mouths is one or more very wet intake tubes. The point is, the zone where the intake tubes meet the combustion chamber is the perfect location to dump atomized (but still liquid) fuel because it has the 2 things necessary to convert it to vaporized, mixed fuel/air: Heat and turbulence.

Well, it makes for a lively discussion, and various viewpoints...

Bill H.
Acoustic Propulsion Concepts, Inc.

I have to go with Bill on the last parragraph, high airspeed heat and turbulance are the main requirments for good atomisatation and the best place to find them is near that transition point from intake to combustion chamber.

Thats not to say you cant find some of those conditions directly behind the intake lip but it lacks the heat input from the engine by conduction and by infrared radiation so we prefure the other end.

Viv

[Bruno Ogorelec]

But, during the combustion phase, the intakes are converted to thrust-producing exhausts. With the fuel supply further into the engine at least part of the outflow will be re-entrained as it begins to beat in again.

Sorry, but I am not sure I understand what you are talking about. Please clarify. What will re-entrain the returning outflow? Where will that flow be entrained towards? What role does the placing of fuel injection play in the process? I have lost you completely.

Remembering that the combustion chamber is only filled to the extent of something like 20%, I don't think it's wise to move the fuel source too far back.

No, it is the entire engine volume that is filled to something like 20 percent. One tries to design the engine so that those 20 percent are within the combustion chamber.

You're going to end up with intake tubes filled with fuel/air mixture at the point of combustion---and these are going to go off like separate entities (if they go off at all) and not contribute anything to the needed primary pressure event in the combustion chamber.

Point taken. This layout will not be high on the fuel efficiency scale. Is this maybe a good case for (Shock! Horror!) timed injection?

Based on my (very limited) experience with liquid fuel delivery, all you're going to get with atomizers at the inlet mouths is one or more very wet intake tubes.

Maybe. You may well be right. On the other hand, there must be injector nozzles that deliver atomized fuel in a narrow cone. But, I take your point at least partly. I am probably influenced in my thinking by my insistence on gaseous fuel.

I have to go with Bill on the last parragraph, high airspeed heat and turbulance are the main requirments for good atomisatation and the best place to find them is near that transition point from intake to combustion chamber. Thats not to say you cant find some of those conditions directly behind the intake lip but it lacks the heat input from the engine by conduction and by infrared radiation so we prefure the other end.

I agree on speed and turbulence and on the fact that they are to be found in the front part of the combustion chamber. But, saying that they are not good in a tubular ejector is like saying that it doesn’t rain in London. What I am saying is, here we have a perfectly good ejector/mixer and we are not using it. If we did, it would do at least a half of the job, with the other half left to be done by the commotion in the combustion chamber. I am not suddenly creating a still and quiet combustion chamber if I inject the fuel into the port, rather than into the chamber. I am just making its job easier. In fact, I wonder if the transition could not be made gentler and the internal drag lessened if half the atomization and mixing were already done by the intake stack. Something to think about.

I admit I was thinking primarily in terms of propane or gasified liquid fuel. Injection of liquid fuel is a bit different. However, look at the history of automotive fuel injection in spark-ignition engines and you will see that injection into ports is the rule. Injection into the chamber is a rare exception.