Bypass Fan Module for Engine Nacelles - Adds Bypass Thrust, allows Stock Turbofan Engines

[Goddess Bhavani]

The Idea:

Currently for VTOL operations we have a choice of the quite weak basic jets and the fuel guzzling Whiplash engines, which allows for 2 turboramjet engines to power a 25 ton "Firefly class" VTOL on tilt nacelles but guzzle gas so fast you'd be lucky to get a 50 mile mission radius for a simple air ambulance mission!

A simple solution to this issue would be to upgrade stock (turbo)jets into modern turbofan engines. Instead of creating new engines, an enterprising modder could instead construct bypass fan modules to stick to the front of stock engine nacelles, giving them the appearance of modern jetliner powerplants.

As we all know, a turbojet engine is simply the core of a turbofan; a fanjet has an additional low pressure turbine at the back which drives a fan which produces bypass thrust; air which flows around the engine core. Therefore it should be quite straightforward to create a 1.875m low bypass fan module to convert a J-33 basic jet nacelle into a low bypass turbofan engine, and a 2.5m bypass fan to convert it into a powerful present day airliner engine.

Balancing:

The turbofan module should provide augmentation for engine thrust at low altitudes; it can simply generate thrust pointed backwards without need to check for occlusion of other parts (if possible) or output the thrust around the outside edge of the part where the outlet of a conventional jetliner engine's bypass is.

The cost for the turbofan conversion should be increased drag area of the engine nacelle (we don't want this to be a free upgrade) as well as added mass. So you could opt for a fast jet that sucks gas or an efficient cruiser with low TWR but good cruise economy around Mach 0.8.

It would also make jetliner replicas have more realistic engine performance and reduce part count (No need to make engine cores and bypass out of many, many basic jet engines). The idea, once again, to create a bypass fan module, is to allow craft builders to customize their engine nacelles and provide various bypass options for existing engine types in order to modify or enhance their performance in specific areas.

Thoughts?

Edited October 2, 2015 by pandoras kitten

[cobbman11]

I don't know much about creating this kind of stuff, but I can say that it would be a welcomed addition. My recent 737 replica suffered from poor engine performance.

[Razordraac]

For this I would suggest having two thrust exhausts at the rear of the engine - with one acting as the core in the middle and one acting as the bypass around the outside. Change the efficiency and power of both, and how they relate to each other, and walla, simple turbofan engine

[Nazari1382]

I have some unfinished models for a concept very similar to this, and they could potentially be used with AJE, which I had mentioned to Blowfish when I started them. Its just a matter of finding the time to work on mods...

[Alshain]

These are coming in 1.1. Wheesley is getting redesigned as a turbofan (it's performance is already like a turbofan, now the model will match). Plus a new Goliath High Bypass turbofan, the Panther I *think* is supposed to be a low bypass turbofan and a small 0.625m "Juno" jet engine, I'm guessing it is a turbojet it kinda looks like the Junkers Jumo 004 (worlds first turbojet) and that name sounds a lot like it. That little Juno engine might prove useful for VTOL, depending on the craft size.

http://imgur.com/a/NkzMp

Edited October 3, 2015 by Alshain

[AdmiralTigerclaw]

I think the problem with this is that right now engine modules work on a 'get resources, produce thrust' formula that treats the engine as one big chunk.

AJE from what I've seen, forcibly pulls the work of the code out and does the math, and then reinjects the modified thrust values back into the game, but it's still a mechanic of 'get resources, produce thrust', just that the math for how the thrust is produced is done 'off site' from the original engines.

Really, what would make something like this workable would be separating the turbine's behavior into multiple code modules and part modules.

Essentially, break the turbine into its composite parts. Inlet > Intake Fan > Compressor Stage > Burner > Power Turbine Stage > Exhaust stage and then determine what gets to be its own part.

Inlet, obviously stays as an inlet.

Intake fan, is essentially what you're suggesting to be the new bypass fan part. It would definitely make for a useful part. I would make this one part of thrust production.

Compressor Stage, I would pair with the burner stage and the power turbine. The output of the C/B-Stage would be 'power' or 'Torque'.

And then a nozzle type, be it a 'turboshaft' type nozzle, or a jet exhaust.

So the mechanic I would do here is 'put the turbine in a box'. That is to say, alone, the turbine produces no thrust. It produces POWER, but no thrust without the proper pairing.

Displayed next is a picture I whipped up to show the model I'm thinking of.

I would think this breaks a turbine engine into the key components one really needs for making them more customizable, while allowing the 'modular' simplicity to remain. Performance can be spiced up by having a few types of each modular part, and the behavior of the engines as a whole now depends on how the player builds their turbine set. Keeping the Compressor, Burner, and Power Turbine segments all as one part is going to be key in keeping this simplicity. That's the part that is all one running machine all on its own, everything else are 'mods' to said machine that are strapped on each end.

As an example, A turbofan would be an inlet, a bypass of their choice depending on the job, a turbine core, and the fitting exhaust nozzle.

A helicopter would be an inlet, a turbine core, a turboshaft module instead of a nozzle, and a rotor blade that's not considered here.

A generator is an inlet and a turbine.

A J-57 engine is a shock cone inlet, a special bypass tube component that has the additional product [uSED AIR] resource, a turbine core, and a WHOLE lotta afterburning doom.

And just to double-clarify from the image. [uSED AIR] is simply to differentiate the intake air from the various inlets from the air supply the engines feed to the nozzle. Otherwise, the nozzle gets air directly from any inlet on the vehicle no matter what the engine conditions might be.

Thrust behavior in accordance with player throttle would not control the turbine core. Instead, code from Kerbal Foundries' Auxilliary Power Unit, which throttles the APU based on demand, can be linked to the [POWER] resource draw of the parts around it, allowing the core to behave as needed be it used as a jet, or as a helicopter engine.

Code to look into to make performance work out nicely would be AJE, Firespitter, and Kerbal Foundries. AJE would be to make the turbomachinery work, while KF is for the throttle control. Firespitter for props, bypass fans, and rotors.

[Sampa]

given the fact that I am learning about this, once I finish learning blender, I might want to give this a try!

[Azimech]

Very interesting!

[SuicidalInsanity]

Heh. I actually rigged up something similar with MM back in 0.90 - The numbers could use some tweaking for better balance, but perhaps it could serve as a base or starting example. It was actually sorta fun to play around with, since suddenly aircraft had to have actual volume dedicated for their engines. Quick port to 1.04:

RESOURCE_DEFINITION
{
name = CompressedAir
density = 0.005
unitcost = 0
flowMode = STACK_PRIORITY_SEARCH
transfer = NONE
isTweakable = false
}

@PART[JetEngine]
{
@MODULE[ModuleEngines*] {
@PROPELLANT[IntakeAir]
{
@name = CompressedAir
}
}
}

@PART[turboFanEngine]
{
@MODULE[ModuleEngines*] {
@PROPELLANT[IntakeAir]
{
@name = CompressedAir
}
}
}

@PART[RAPIER]
{
@MODULE[ModuleEngines*] {
@PROPELLANT[IntakeAir]
{
@name = CompressedAir
}
}
}

@PART[radialEngineBody]
{
stagingIcon = COMMAND_POD
@mass = 0.85
@description = The newest iteration of the classic C7 radial Engine Body keeps the radial airscoops and lightweight fueltank, and goes the extra mile with the addition of a robust, if less than cutting edge, compressor turbine. Compressors turn intake air into compressed air needed for a jet to function.
RESOURCE
{
name = CompressedAir
amount = 0.1
maxAmount = 1.0
}
MODULE
{
name = ModuleResourceConverter
ConverterName = Compresor
StartActionName = Start Compressor
StopActionName = Shutdown Compressor
FillAmount = 0.95
AutoShutdown = false
GeneratesHeat = false
UseSpecialistBonus = false


INPUT_RESOURCE
{
ResourceName = IntakeAir
Ratio = 0.85
FlowMode = STAGE_PRIORITY_FLOW
}
OUTPUT_RESOURCE
{
ResourceName = CompressedAir
Ratio = 0.85
DumpExcess = false
}
}
}
@PART[nacelleBody]
{
@mass = 1.2
stagingIcon = COMMAND_POD
@description = The Engine Nacelle is a self-contained solution for powering air-breathing engines. It holds some fuel, as well as combining air intake and top-of-the-line compressor into a single unit, making it a very practical option. Compressors turn intake air into compressed air needed for a jet to function.
RESOURCE
{
name = CompressedAir
amount = 0.1
maxAmount = 1.0
}
MODULE
{
name = ModuleResourceConverter
ConverterName = Compresor
StartActionName = Start Compressor
StopActionName = Shutdown Compressor
FillAmount = 0.95
AutoShutdown = false
GeneratesHeat = false
UseSpecialistBonus = false


INPUT_RESOURCE
{
ResourceName = IntakeAir
Ratio = 1.5
FlowMode = STAGE_PRIORITY_FLOW
}
OUTPUT_RESOURCE
{
ResourceName = CompressedAir
Ratio = 1.5
DumpExcess = false
}
}
}

@PART[MK1IntakeFuselage]
{
@mass = 1.6
stagingIcon = COMMAND_POD
@title = Advanced Engine Body
@description = This advanced unit sacrifices fuel capacity for a heavy duty and incredibly efficient compressor turbine for all your high performance jet engine needs. Compressors turn intake air into compressed air needed for a jet to function.
RESOURCE
{
name = CompressedAir
amount = 0.1
maxAmount = 1.0
}
MODULE
{
name = ModuleResourceConverter
ConverterName = Compresor
StartActionName = Start Compressor
StopActionName = Shutdown Compressor
FillAmount = 0.95
AutoShutdown = false
GeneratesHeat = false
UseSpecialistBonus = false


INPUT_RESOURCE
{
ResourceName = IntakeAir
Ratio = 3.0
FlowMode = STAGE_PRIORITY_FLOW
}
OUTPUT_RESOURCE
{
ResourceName = CompressedAir
Ratio = 3.0
DumpExcess = false
}
}
}

// MM Configs for changing jet engines to use compressed air, and modding the radial and nacelle engine body to be compressors

Edited October 5, 2015 by SuicidalInsanity

[Goddess Bhavani]

Heh. I actually rigged up something similar with MM back in 0.90 - The numbers could use some tweaking for better balance, but perhaps it could serve as a base or starting example. It was actually sorta fun to play around with, since suddenly aircraft had to have actual volume dedicated for their engines. Quick port to 1.04:

I would VERY much like to try this soon! This seems like exactly what I'm hoping for in turbine simulation, and the need to provide space for compressors and intakes would add an interesting layer of detail to aircraft design.

I also communicated with AdmiralTigerClaw above to illustrate that if these turbine simulation addons ever take off, then it would be plausible to try and simulate other types of engines as well - internal combustion engines, for one, could work by using intakeair to feed through a carburetor, and the resultant FuelAirMix being combusted in the cylinder head for torque. Torque is output from the engine out of the Crankshaft, and drivetrain is responsible for converting Torque into Horsepower which drives accessories and turns wheels.

The fun thing about ICE modelling is that one can use the stock thermal model to simulate horsepower and engine reliability being limited by engine temperature; if the cylinder heads blow the engine ceases to work, necessitating design of a working air or liquid cooling system using stock parts.

Different intake and carburetion options could increase power at the cost of heat, so hot rod builders could use this as technical challenge - extreme cylinder heat would flow to other parts, possibly causing them to fail as well.

For turbines, the same kind of treatment can be added to the Combustor part of the engine to realistically simulate limited endurance with continuous max thrust settings; this could be countered by providing WaterInjection modules that add thrust and cool down the engine core until the water runs out; useful for large cargo aircraft and early generation heavy jet bombers.

These are coming in 1.1. Wheesley is getting redesigned as a turbofan (it's performance is already like a turbofan, now the model will match). Plus a new Goliath High Bypass turbofan, the Panther I *think* is supposed to be a low bypass turbofan and a small 0.625m "Juno" jet engine, I'm guessing it is a turbojet it kinda looks like the Junkers Jumo 004 (worlds first turbojet) and that name sounds a lot like it. That little Juno engine might prove useful for VTOL, depending on the craft size.

http://imgur.com/a/NkzMp

Those new parts look great! The Panther would be most welcome for mid-range performance and I think would produce enough thrust to act as a useful compact VTOL powerplant; albeit a deck-melting one!

Edited October 4, 2015 by pandoras kitten

[AdmiralTigerclaw]

One of the points I want to emphasize with mine however, is customizing with intuitive simplicity kept in-tact. The performance of a turbomachine alone varies wildly with the number of compression stages and their ratios, and the recovery of power can likewise be varied. However, the math gets nasty and my thought is simply to keep that all one core component with a few variations on type.

Like I mentioned before, my main thing is that turbine engines change in function and purpose massively by the big parts you strap to each end. IE, the fans and nozzle types. I'm not as familiar with piston engines as I am with turbines, so I don't know how much you're breaking things down. Perhaps you should post a diagram of your engine model as well.