On the other hand, for much more complex engines – internal combustion and turbojet, what models have not been invented? There is a choice for every taste and wallet. And even without a wallet. Do you want to model your own turbojet engine? No questions at all, please! Special programs will not only draw it, but also show how its parameters will change with any changes in the initial data, including speed and flight altitude. But maybe you want to go back to the roots and make your own piston engine? No problem, you can also easily find a program for modeling ICE and watch practically “live” how the length of the exhaust pipe affects the power. But for some reason, everything is different with a pulsejet engine – scientists will not let you lie, they will confirm, that there is not possible to do so easy.

So what do we have as a result? Only some empirical formulas that came from nowhere for some vague calculation of the general dimensions and ratios, probably obtained from practical experience of cutting and welding a large number of steel pipes. And that’s it? It turned out that this is exactly so – indeed, there is nothing else. Well, OK, if you can calculate something and even get some pipe dimensions for welding, why not calculate them? But as soon as you calculate something, even more questions arise. For example, if the pipe is made a little longer, is it good or bad? And if it is shorter, how will it work? And if the pipe is made conical, is it better or worse? And if we put our pipe on an aircraft and launch it at a speed of about 500-600 kilometers per hour, will it give more or less thrust? Or, as some of the most advanced scientists say, will the oncoming air push through the valves and everything “degenerate”? But at what speed will this “degeneration” occur?

There are still no clear answers to these questions. But it is already clear that without modeling, nothing works. That is, no – it works, but it takes too much stainless steel, time, grinding wheels for cutting and welding electrodes for welding. But is a simple pipe worth such serious investments? Nevertheless, up until now this path has been the most common, mainly among welding enthusiasts. Cut, weld, cut again and weld again – is it really this path that will continue to be the only possible and correct one for designing pulsejets?

We – have not believed it. And generally speaking, it is very hard to believe that in the 21st century there is some mysterious pipe for which there is no ready-made calculation model and not a single ready-made program has been written. Why it is not written – someone was not given the money he wanted, someone could not or did not want to strain himself, because he was sure that it was impossible, and someone decided that it is easier to cut and weld than to think and calculate – it is not even interesting to understand it anymore. We just sat down and in a couple of weeks wrote a model and program for simulating the working cycle of a pulsejet engine. Which we then took and posted here on a website specially created for this. And now anyone can run this program. And not just run it, but even check whether his engine works with the specified parameters, and if it works, then how – well or not very well.

We certainly understand that creating a model and a program that would be pleasing to everyone in all respects for simulating a really complex work cycle is a very difficult and perhaps even almost impossible task. Therefore, we would like to immediately warn skeptics that the work cycle model we currently offer, as well as the program itself, is just the beginning. Immediately after the launch of the project, both the model and the program are already in a continuous process of fine-tuning and improvement. Therefore, we will be glad if users send us information about any problems when working with the program - we will always accept any comments with gratitude, check and correct all detected errors.

In order to create a working model of a pulse jet engine for a wide range of users, we developed the Pulsejet-Sim program – an online service for calculating and optimizing the pulsejet parameters.

Pulsejet-Sim is a so-called web-oriented SaaS service (Software as a Service) for engineering calculations of pulse jet engines. Initially, our idea was to divide the program into 2 parts: the user sees only his user part, where he sets the initial data, and then this data is transferred to the server part, where the calculations themselves take place, from where the calculation results are then sent to the user part.

As a result, the service was built on the Python 3/Django 4.2 LTS + PostgreSQL + Celery/Redis stack on the server side and jQuery 3.7 + Bootstrap 5.3 on the client side, and the architecture received three logical modules:

1) the Data-Entry & Metadata Service module performs step-by-step parameter input, immediately generating intermediate metadata and dynamically suggesting acceptable ranges;

2) the Preset Manager module saves factory configurations and any user sets, allowing their export and exchange;

3) the Compute Engine module asynchronously launches numerical calculations on cloud nodes (up to 192 virtual processors), caches thermodynamic tables and returns results in less than 2 seconds.

The calculation process is accompanied by graphical construction of diagrams of the calculated parameters. After completion, the results are stored in the results table and in special cloud storage, from where the user can download them. The user can also view and then save the calculation data, including the main engine parameters in the last calculated cycle, as well as conduct parametric studies for some parameters. In addition, the processing of the results includes the construction of diagrams, where the least squares method is used with the function of eliminating random errors that exceed the maximum permissible deviation.

The principle of constructing our Pulsejet-Sim program is fundamentally different from classic research programs, which are built in the form of desktop engineering software simulation packages and require local computing resources of increased performance, long installation and expensive licenses. On the contrary, compared to well-known desktop packages (ANSYS and similar), the online Pulsejet-Sim program provides work directly in the browser, instant scaling and secure storage of data in the repository without the need to own the hardware.

As a result, the measured average duration of the Pulsejet-Sim thermogasdynamic run is only 1.8 s. In practice, this means that the program allows you to conduct research even on your own phone and obtain parametric dependencies, characteristics and diagrams of the parameters of a pulse jet engine, which is over 300-500 calculation cycles of 2000 points each, within a few seconds.

For research groups, such performance means a significant increase in the number of iterations with the same budget ceiling, and for startups - the ability to run engineering simulations without capital investments in their own hardware. Such features and advantages make our Pulsejet-Sim program an extremely effective tool for engineers and scientists, employees of scientific laboratories and design bureaus, as well as for students of educational courses.

1. Just go to the program and select your engine type – valve or valveless.

2. Then go to the general data entry page. You can easily test the program if you click the 'Last saved data' button here – the program will start working with the default data, skipping all other pages of inputting the initial data.

If you click the 'Custom Initial Data' button, you can enter your own dimensions. When entering, the program indicates the most typical values of the input parameters known to date. For advanced users, you can also set parametric calculations with a change in the selected parameter within the specified limits (such parameters are marked in color) – as a result, you can get graphs of the dependence of the main engine parameters on the selected parameter. However, please note that we provide access to such calculations only after registration and payment for a subscription. Some parameters can also be changed only with a subscription, about which the program will issue a corresponding warning. After entering your data, you need to click the 'Continue' button to go to the next page.

3. The following input pages work in exactly the same way – either the input of the initial data is replaced by previously saved data (default data), or you need to enter your own data.

4. The program works with all known types of valves and valve systems, so you can select the type of valves, and then you will be asked to enter their dimensions. After entering the type of valves, you will no longer be able to switch to the default dimensions, it will be mandatory to set your own dimensions. However, the program will help and indicate the known limits of change for each dimension.

For a valveless engine, the dimensions of the intake pipe are specified instead of valves. This pipe is turned back parallel to the exhaust pipe by default – this is important, since in a valveless engine both pipes, the intake and exhaust, create jet thrust.

5. The program uses a simplified model of combustion and gas flow, it requires some adjustment. The used correction factors are listed on the corresponding page. What they affect is clear from their name. By default, their value is set to 1.0, but if necessary, you can enter a correction in certain processes (a function for professionals, provided by subscription).

6. At the end of the input, you will be prompted to enter the calculation parameters. We recommend assigning at least 5 calculation cycles to obtain a stabilized pulsating cycle, with a minimum influence of the initial conditions (the least influence is observed at 7-10 cycles, but this takes time). It is advisable to select the time step from the recommended range, since with a larger step, the stability of the solution may suffer, and with a smaller one, the calculation time increases.

7. After entering all the initial data, they will be displayed on the final input page. You can approve them and start the calculation or go back to the beginning of the input.

8. During the calculation, the program shows the change in the calculated parameters in real-time calculation mode – you can watch the entire process from the moment of starting air supply and ignition of the fuel-air mixture until the end of the selected cycle number!

If the correct engine operating parameters were set, the program will definitely give similar cycles. However, if you enter any erroneous or unrealistic parameter value, the cycle can easily become damped, and by the 5-7th cycle, the parameter changes will turn into slightly oscillating lines. If the parameters differ significantly from the normal one, the program has the right to refuse to consider such an engine, stop the calculation and issue a corresponding warning with the ability to return to entering the initial data.

9. The first result obtained, as soon as the program calculates everything, is the main engine parameters. After them, you can get graphs of parameter changes in the cycle.

10. It is possible to simultaneously display 4 cycle parameters on graphs - pressure and temperature in the combustion chamber, as well as the speed in the exhaust resonance pipe and at the inlet (in the intake pipe for a valveless engine). Additionally, you can display the position of the gas-air boundary in the pipes – a very important parameter for a valveless engine, since it determines the beginning of air intake into the chamber through the intake pipe, taken as the beginning of a new cycle. In addition, the position of the gas-air boundary in the exhaust pipe shows how much air has entered the pipe and will be pushed out – this affects the engine thrust. You can also display the instantaneous value of the valve petal lift, air flow, heat release rate during combustion and other parameters. The default selection of output parameters can be changed with a subscription.

11. The final calculation page shows the results of the specified parametric study, that is, a graphical dependence of the influence of the selected parameter in its selected limits on the main engine parameters (provided by subscription). After that, you can save the file with the calculation data in your account (also a subscription function) and proceed to a new calculation.