Determining the Dimensions of a Pulse Jet Engine: A Scientific Approach

Click For Summary

Discussion Overview

The discussion revolves around the design and dimensions of a pulse jet engine, including the determination of various components such as the tailpipe, combustion chamber, air intake valve system, and fuel burn rates. Participants explore theoretical and practical aspects of pulse jet engine design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant suggests starting with fuel burn rates to determine the air intake area and subsequent dimensions of the engine.
  • Another participant requests a detailed example of calculations for a specific 35 lb thrust pulse jet engine using gasoline and alcohol as fuels.
  • Some participants express frustration with existing resources, claiming they do not provide sufficient scientific information for designing a pulse jet engine.
  • A participant mentions having developed personal formulas for pulse jet engines but emphasizes the need for physics-based data on fuel burn rates in air.
  • Concerns are raised about the lack of clarity in existing plans, particularly regarding unspecified dimensions.
  • One participant reflects on their long experience with pulse jet engines and the importance of understanding the underlying physics for optimal design.
  • Another participant encourages engagement with the community and suggests that learning from experienced members could be beneficial.

Areas of Agreement / Disagreement

Participants express differing views on the adequacy of available resources for pulse jet engine design, with some finding them lacking in scientific rigor while others believe they are sufficient for learning. There is no consensus on the best approach to design or the importance of specific data.

Contextual Notes

Participants note limitations in existing plans, particularly regarding the lack of clear dimensions and scientific data related to fuel burn rates in air. There is also mention of personal experiences and the need for a deeper understanding of fluid mechanics.

Who May Find This Useful

Individuals interested in pulse jet engine design, engineering students, hobbyists, and those seeking to understand the principles of combustion and fluid dynamics in practical applications.

gary350
Messages
292
Reaction score
83
If you were to design a pulse jet engine where would you start?

How do you determine the diameter and length of the tail pipe?

How do you determine the diameter and length of the combustion chamber?

How do you determine the area of the air intake valve system?

How do you determine the burn rate of the fuel?

How do you determine the over all length and design of the engine?
 
Physics news on Phys.org
I suppose I would start with fuel burn rates. That's because, as a private citizen, I have access to a very limted number of fuels, and can easily look up their burn rates at different mixtures. From there I could determine the area of the air intake, which would tell me how large thje valve assembly needs to be, and keep going from there.
 
Where do I look up the burn rate of fuel air mixtures?

How about a 35 lb thrust pulse jet engine with gasoline as the fuel.

Give me an example for calculating, doing all the math for this engine. If I can see an example and know where to find all the information then I can take it from there and do the math for other size engines. I would also like to use Alcohol as a fuel too. Methal or Ethyl.
 
If you Google pulse jets, you will find a wealth of information. They are not difficult to design. However, having someone tell you how to do something doesn't teach you anything about it. You need to do the research and the digging.

How about starting here:
http://www.pulse-jets.com/
 
FredGarvin said:
If you Google pulse jets, you will find a wealth of information. They are not difficult to design. However, having someone tell you how to do something doesn't teach you anything about it. You need to do the research and the digging.

How about starting here:
http://www.pulse-jets.com/

This information is worthless. I found this years ago. It is a bunch of plans other people have built. There is nothing her that teaches a person how to design their own. Anyone can copy other peoples plans. What I need is some scientific informations based on the laws of physics and formulas.
 
Last edited:
gary350 said:
This information is worthless. I found this years ago. It is a bunch of plans other people have built. There is nothing her that teaches a person how to design their own. Anyone can copy other peoples plans.

If you found this site years ago and still do not know anything about pluse jets, I have to draw the conclusion your a bit lazy.:rolleyes:
 
RonL said:
If you found this site years ago and still do not know anything about pluse jets, I have to draw the conclusion your a bit lazy.:rolleyes:

There are lots of plans there that is all I have found. Most of those plans are not good. They don't have all the dimensions and some dimensions are just numbers like 75, 40, 30, 25. So what is that, 75 what? 75 meters, 75 feet, 75 inches, 75 milimeters?

I have built a lot of pulse jet engines over the past 31 years. I have come up with my own formulas that work very well but I thing there has to be some physics involved here that can be used to design these engines and fine tune them to run at maximum efficiency.

I have book on Liquid fuel rocket engines they are all designed around the burn rate of the fuel. I think a pulse jet engine should be designed around the burn rate of the fuel but there is no data for burn rate in air.

I have been out of college 40 years, if you don't use it you loose it, I have forgotten more than I every knew. I wish I still have my old college fluid mechanics book seems to be there is some good information in there that I need.
 
gary350 said:
There are lots of plans there that is all I have found. Most of those plans are not good. They don't have all the dimensions and some dimensions are just numbers like 75, 40, 30, 25. So what is that, 75 what? 75 meters, 75 feet, 75 inches, 75 milimeters?

I have built a lot of pulse jet engines over the past 31 years. I have come up with my own formulas that work very well but I thing there has to be some physics involved here that can be used to design these engines and fine tune them to run at maximum efficiency.

I have book on Liquid fuel rocket engines they are all designed around the burn rate of the fuel. I think a pulse jet engine should be designed around the burn rate of the fuel but there is no data for burn rate in air.

I have been out of college 40 years, if you don't use it you loose it, I have forgotten more than I every knew. I wish I still have my old college fluid mechanics book seems to be there is some good information in there that I need.

I only meant to be a little offensive in my comment, as Fred is a much respected member of this forum, you'll learn more about him and others that can help you, if you stay around awhile.
Please do, it sounds as if you have some info that can be of help to others.

I have to go for now but will be back later.

Check out the rules and forum guidelines, and stick around long enough to get to know a few of the people here.

RonL
 

Similar threads

Can a Railgun-Powered Ramjet Solve the Challenges of High-Speed Travel?
  • · Replies 4 ·
Replies
4
Views
3K
How Can I Calculate Pulse Jet Engine Dimensions Using Air as Oxidizer?
  • · Replies 4 ·
Replies
4
Views
14K
How Does Fuel Expansion and Contraction Work in Pulse Jet Engines?
  • · Replies 4 ·
Replies
4
Views
22K
Calculating suction area around the intake of a jet engine
  • · Replies 3 ·
Replies
3
Views
6K
Pulse Jet engine - A new design concept
  • · Replies 43 ·
2
Replies
43
Views
27K
Undergrad Understanding the thrust generated by a typical jet engine
  • · Replies 2 ·
Replies
2
Views
3K
Graduate Calculate Frequency of Flat Spring Steel for Reed Valves in a Pulse Jet Engine
  • · Replies 26 ·
Replies
26
Views
5K
Understanding Airflow and Pressure Changes in Jet Engine Design
  • · Replies 24 ·
Replies
24
Views
5K
A practical way to vaporize fuel for high MPG?
  • · Replies 39 ·
2
Replies
39
Views
4K
Is there a limit on rocket engine exhaust velocity?
  • · Replies 16 ·
Replies
16
Views
8K