What is injector: Definition and 20 Discussions

An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic pump with no moving parts except a valve to control inlet flow.
A steam injector is a typical application of the principle used to deliver cold water to a boiler against its own pressure, using its own live or exhaust steam, replacing any mechanical pump. When first developed, its operation was intriguing because it seemed paradoxical, almost like perpetual motion, but it was later explained using thermodynamics. Other types of injector may use other pressurised motive fluids such as air.
Depending on the application, an injector can also take the form of an eductor-jet pump, a water eductor or an aspirator. An ejector operates on similar principles to create a vacuum feed connection for braking systems etc.

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  1. S

    How to select a pump for a venturi injector?

    I'm building a fertigation system using 1 inch venturi injector with ball valve at the end to simulate drip irrigation system pressure requirement. i have read to start an injection you need 30% pressure difference between injector inlet and outlet. the pressure I'm simulating is around 10 meter...
  2. A

    B Pinched plasma inside a neutral beam injector

    Let me start this off with saying I am just a uneducated idiot, But after reading about Zap Energies sheared flow pinch reactor I was wondering if you could use a similar concept in a neutral beam injector? Like could you first compress and heat the plasma inside of a NBI using a pinch, then...
  3. Austin_Tx_Rockets

    Does the discharge coefficient of an injector depend on the fluid?

    The discharge coefficient is the ratio of the actual discharge to the ideal discharge and can be measured experimentally. If one were to experimentally measure the discharge coefficient using water, would this value be constant for all incompressible fluids? What does the discharge coefficient...
  4. S

    Diesel Injector and Water Tube Boiler Back-Pressure

    Diesel injector: How much pressure relative to the maximum combustion chamber pressure during the sharpest phase of detonation does an injector need to be able to overcome to inject its full charge? How much overlap is typical between injection and detonation? Water-tube boiler: Are the water...
  5. W

    Measuring Parameters for a Hybrid Rocket Injector Assembly

    I am interested in research on hybrid rocket technology and I would like to know if anyone has a known ideal way to measure the required parameters to find the below items. I am particularly interested in a cold flow test involving: Characteristics of the Oxidizer Flow Turbulent Intensity...
  6. kunalvanjare

    Venturi injector suction not adequate

    Hey guys, we've been tasked with providing solutions for reducing coolant consumption by our client using automation. One of those is a system to reclaim the coolant dripped off of the chips from a Chip Trolley in a CNC Machine. Around 15-20 Litres of coolant+water emulsion is wasted everyday...
  7. W

    Hybrid Rocket Injector Plate Design Research

    Hello, First of all, I hope this post is in the right section (aerospace engineering). I am doing research on the injector plate design for a hybrid rocket and I'm no where at the moment. I was thinking that I could improve the geometry of the injector plate in order to help improve some...
  8. Roy S Ramirez

    Measuring the Discharge Coefficients of a Rocket Injector

    Hello everybody! I hope you are all doing well. I built a liquid rocket injector and the following feed system: I started to do hydro-static tests (cold flows) and a program I wrote records all the data for me (except for the flow rates which I measured experimentally by collecting the water...
  9. Roy S Ramirez

    Injector pressure drop in a liquid rocket engine

    Hello everybody, I hope you are doing fine. I'm currently designing an injector for a hydrogen peroxide - ethanol engine, and the following formula is confusing me: Q = Cd * A * sqrt( 2 * dP / rho); where Cd is the discharge coefficient, A the total area, dP the pressure drop, and rho the...
  10. eigenmax

    Need a small valve for gas injection? Any ideas?

    Hello everyone, For injecting gas into a little setup I've got, I have the following mechanism set out. The gas comes from a chemical reaction, goes through a copper capillary, then to a glass tube which was melted in the centre and pulled at both ends to create a thin passage. Then from that to...
  11. P

    Some questions about Steam Injector principle

    http://www.mekanizmalar.com/how-steam-injectors-work.html In the link above, the basics of steam injector is given. Steam Injector's don't have any moving parts and doesn't consume any energy by themselves. Still, it can be able to pressurise water and inject that to a high pressure Boiler by...
  12. H

    Calculating Entrained Flow in Injector Design: Challenges and Considerations

    Hello, I am trying to analyze an injector and having trouble coming up with the final equation for the calculation. The apparatus can be seen below. Assuming we know the inlet flow rate and pressure (A) from the pump/fan and the pipe geometry. The pressure out of the outlet of the nozzle is...
  13. M

    Diesel injector sac pressure calculation

    I am trying to calculate the nozzle sac pressure required to deliver 60mm3/ms of diesel fuel into a pressurised cylinder (19MPa). The nozzle has 5 delivery holes of diameter 0.157mm and the discharge co-efficient is 0.87. The sac diameter= 0.7 mm and the sac volume= 0.12mm3. I have tried to use...
  14. P

    Non-steady suction induced by Venturi Injector

    This is not really homework but an engineering problem nonetheless. 1. I have a venturi injector sucking in liquid (by all means and purposes identical to water) and injecting into a pressurized water line. A straight tube is inserted into the container of liquid (below the liquid surface) and...
  15. crador

    Fluid Dynamics pipeline with a venturi injector

    Hey guys, I've been wracking my brain for a while, and thus I have landed here yet again. My problem is the following: Say you have a pipeline with a venturi injector, and intermittently a large tank of water with a portion of air on top -- I.e. a closed circuit communicating between the...
  16. M

    How to Measure Volume/Injection in a CRI Engine Injector Tester?

    Hello all. I have a project to make the injector tester for CRI engine. Any ideas how to measure volume / injection ? Hery
  17. P

    Automotive Fuel Injector Angle Within Fuel Injector Port

    I'm trying to find information regarding the angle of the fuel injector with respect to the air intake. Basically, I want to know how important it is, and how changing that angle would affect the performance of a vehicle. I'm working on a Formula SAE race car, and my team and I are looking to...
  18. G

    How to select the Injector for CNG application

    Help me Guys How to select the Injector for CNG application
  19. M

    The Mystery of Electronic Fuel Injectors - How Do They Work?

    hello everybody my ques about the fuel injector,which is working electronically-- i saw it for real in a car was fixing by a mechanic,and i looked at the electronic fuel injectors mounted on the fuel rail----and while the engine was running,the injector as u know-is supplied by the pressurized...
  20. Clausius2

    Fuel injector surrounded by a coaxial air stream

    Maybe you, chemical people could answer my question. Imagine a fuel injector surrounded by a coaxial air stream. The fuel and air flow are parallel, coaxial and axisymmetric. Both fluids obey ideal gas equation. Let's consider steady and compressible flow, i.e, variations of \rho are...