喷气推进/喷气发动机类型
< 喷气推进
冲压发动机使用开放的 布雷顿循环。不使用旋转机械，压缩是由进气道和扩散器实现的。因此，它们需要速度来压缩足够的空气，以便实现良好的效率。冲压发动机在 亚音速 下效率低下，并且它们的效率在超音速下提高。
燃料被注入压缩空气中，并使用火焰稳定器燃烧，以稳定湍流火焰，如加力燃烧室。
在 高超音速 下，压缩和解离过程使完全扩散变得不可取，并且正在研究超燃燃烧。一个 超燃冲压发动机 将空气减速至低超音速，然后燃烧高火焰速度燃料（如氢或甲烷），以尝试获得净推力。
当速度增加时，气流的总温度会升高到超过燃烧产物的解离温度。如果气流被扩散到亚音速，这将阻止有效燃烧。为了解决这个问题，使用高传播速度的燃料（如氢），同时将进气空气扩散到超音速，而不会使气流的温度大幅上升。挑战变成获得稳定的火焰锋面和净推力。
涡喷发动机增加了由涡轮驱动的旋转压缩机。这使得压缩超过进气道的停滞压力，并在较低速度下提高了相对于冲压发动机的效率。热空气离开涡轮后被喷嘴加速并排出。加力燃烧室可用于增加推力。
一个包络的叶扇允许更大的空气质量被一个包络的叶扇移动，该叶扇的流动绕过核心。叶扇相对于核心的相对尺寸由 旁通比 确定。
下图显示了典型的双轴高旁通涡扇发动机的布局。
涡扇发动机中涡扇旁通质量流量与发动机核心质量流量的比率。
顾名思义，这是绕过发动机核心并流过发动机外部并通过喷嘴排出的空气的比率。在现代高旁通比发动机中，旁通比可以高达 85%。增加叶扇的尺寸和旁通比会导致重量增加。无导流风扇或 螺旋桨风扇 的重量增加较小，但噪音在西方一直不可接受。
由于叶扇的直径远大于涡轮，因此它必须以低得多的转速运行。传统上，这是通过多个涡轮级来实现的。然而，这使得涡轮系统不必要地复杂，因此人们试图使用齿轮箱来减少所需的涡轮级数量。到目前为止，功率要求尚未应用于更大的涡扇发动机，但公司仍在尝试。
示例：Honeywell_ALF_502 用于 BAe 146。
带齿轮箱和螺旋桨的涡轴发动机。
进气道、压缩机、燃烧室和驱动轴的涡轮。用于直升机、辅助动力装置，以及地面应用，如坦克、船舶、发电。
使用脉冲爆轰来关闭进气道，而无需初级压缩。进气道关闭可以是动态的，也可以使用机械阀（如 簧片阀）。
TYPES OF PROPULSION SYSTEMS (BASIC EXPLANATION LISTING)
我是一名 FAA 认证的喷气发动机、活塞发动机和机身机械师，并且精通应用物理学和系统设计。以下是我对喷气发动机本身，以及涡轮发动机和所有其他推进动力装置的分类方式
1.) Turbine Propulsion:
A.) Turbojets Engines - No Bypass Cold Airflow Duct and large front Fan, just compressor-turbine spool(s) core.
B.) Turbofan Engines - Large Fan in ahead of compressor-turbine spool(s) core with By-Pass Cold Airflow Duct around
engine body and compressor-turbine spool(s) core.
2.) 涡轮扭矩
A.) Turboshaft Engines - More Turbine Stages w/ Free Turbine to Gear Reduced
Transmission.
B.) Turrboprop Engines - Same as Turboshaft Engine except Fuel Control Unit
is linked to Blade Pitch System to prevent Windmilling of Propeller and
RPM on a Turboprop Engine is controlled by Blade Pitch Control.
3.) Non-Turbine Propulsion Powerplants:
A.) Ramjet - Hollow convergent venturi tube, lit off when enough forward airspeed is
present to provide the compression needed to light it off. Higher in efficiency and
thrust than Propulsion Turbine Powerplants and is dependent on the ability of the
fuel injection system pressure and fuel volume delivery limits. Ramjets are limited
to speeds below where the Nitrogen and Oxygen in the air do not compress to such
enormous pressures as to where the Oxygen and Nitrogen merge as one killing
combustion. (Note: Air is 78% Nitrogen, 21% Oxygen & 1% various Inert
Gases).
B.) Scramjet - Supersonic Scramjet or "scramjet". These propulsion powerplants are
ramjets rated for much higher speeds from supersonic to into hypersonic speeds
(more than 4000 MHP). The only limitation is what any ramjet needs to overcome:
The merger of Oxygen and Nitrogen in the Air under enormous compression,
when not controlled will merge the Oxygen and Nitrogen as one and kill
combustion.
C.) Pulsejet - Hollow convergent venturi tube or any type of differential diameter dual
channel which doesn't need to be routed across in a linear manner, but in the same
way hydraulic and pneumatic systems can route the master and actuator cylinders in
series, any which way in terms of orientation. There are glass jars and dual plumbing
pipes with differential diameters which can be made into pulse jets. The typical
aviation-type Pulse Jet is a convergent venturi channel with spring-loaded shutters on
the intake. During the combustion cycle, a vacuum develops in the aft exhaust
section of the venturi causing the spring-loaded-opened shutters to pass airflow during
combustion, until the vacuum increases more than the spring-loaded-open shutters
can handle causing them to close. This allows a sealing-bias on the intake side as to
maximize thrust in the aft rear section. But only for a limited dwell-time pulse cycle as
to where combustion ceases and allows the shutters to open again to repeat the
process. The aviation-type Pulse Jets run at a frequency around 250 to 600 PPS.
As the frequency increases, the Pulse Jet comes online as running into the full thrust
rating as fuel delivery increases to maximum limits. Aviation-grade Pulse Jets may
utilize Heat-of-Compression on high compression Pulse Jet designs running on
kerosene (same as "jet fuel") which allow the Pulse Jet to stay lit without additional
spark plug or glow plug requirements after being lit off, which time the shutters to the
fuel injection system. Or gasoline-models using shutter position to spark can be used
if the compression is lower than needed for allowing a Heat-of-Compression
combustion cycle to be utilized. Plumbing pipes of different diameters connected 180
degrees to each other on a 180 degree bend and can be turned into Pulse Jets too.
This by using a fuel source in the smaller diameter pipe with spark plug and when it
lights off, spark isn't needed anymore, because the compression rises high enough to
keep the Pulse Jet lit. The 180 degree bend between the two different diameter pipes
allow a high pulse on/off frequency to develop between combustion and fuel flow dwell
when the combustion ceases. Something in the range of 1200 cycles per second.
They're noisy for sure, but keep lit on their own. Also a glass jar with a cover at the
top and small hole at the center with a little bit of gasoline in the bottom, carefully
heated on a stove will light off at the top where the hole is and will light off around
1200 cycles per second as a Pulse Jet. Just be careful on adjusting the heat when
using a glass jar.
D.) Rocket Propulsion - These Propulsion Powerplants utilize a tapering convergent
channel within their airframe fuselage section in which a fuel which carries its own
oxygen along with combustible compounds ignite. Escaping through the tapered
convergent channel into thrust. Typical Rocket Fuels are both liquid and solid Oxy-
Hydro Fuels which are Oxygen and Hydrogen mixed together and ignited. Other
Rocket Fuels include Hydrogen Peroxide mixed with a catalyst in separate reservoirs
injected into the taper convergent thrust channel at the correct ratios to support
combustion. This also goes for the Space Shuttle as well, using liquid Oxygen and
Hydrogen in separate reservoirs mixed with emulsified aluminum as to increase thrust
output. Rocket Propulsion speeds are rated to over 30,000 MHP and are more
practical for defense, high altitude weather/surveillance and space programs than
passenger flight, at least for now this is the case.
E.) Missile Propulsion - Missile Propulsion is similar to Rocket Propulsion, except far
more airframe system guidance is involved in the likes of airplanes flying on GPS or
Radar-Guided systems which control Missile Airframe Flight Control Systems. This for
pin-point guidance, steering and targeting/evasive actions to specific target and
collision/avoidance from specific threats. Many missile designs either incorporate
Rocket Propulsion in the same manner as Rockets or use small turbojet engines
within their fuselage. More advanced missile designs are starting to use Ram Jets
along with an initial Rocket Propulsion light-off to get them up to speed. When they
reach a specific airspeed usually around 500 MHP, the Ram Jet will kick in using Oxy-
Hydro fuel to keep them lit and can increase in speeds to around 2,200 MHP while
also fly at low altitudes. Many of these types of missile designs also incorporate
Microwave & Doppler Radar Tracking & Cancellation Systems. So they can't be
tracked by most any type of Radar, even more advanced Radar Systems which
track flying objects by their airflow pattern converted into a visual profile. Such
missiles have been pioneered by Russia & India, such as the Moskit from Russia
and the Bramos from India.
F.) Air Pressure Propulsion - This is none other than a larger diameter accumulator
shaped like a cylinder with an enormous amount of air pressure pre-charged connected
to a powerful air compression with high volume capacity tank. On the other end of this
cylinder is a small diameter pipe which when opened up passing a high amount of air
velocity, by the air pressure being stepped down at the end before the smaller tail pipe
begins causing the air velocity to rise. These types of Propulsion Systems require a
constant pressure to remain at a certain limit within the accumulator cylinder to be
effective for any practical thrust. Experimental applications using this type of
propulsion would also require a large enough accumulator cylinder to provide for
enough constant pressure to stagnate while the air escapes through the small tail pipe
into thrust. [Pressure = Force / Area; Force = Pressure x Area. This is the basic
principle on how hydraulics, pneumatics, firearms, rockets, jet propulsion, piston
engines and aircraft operate by].