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# <a name="Hybrid Plumbing"></a> Hybrid Plumbing

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<div>
  <center>[[!img HybridPlumbing/plumbinglarge.jpg size="581x385"]]</center>
</div>

**Overview**

The plumbing for our hybrid motor will provide the necessary gaseous oxygen mass flux for the paraffin fuel grain as well as a nitrogen purge system to extinguish and cool the motor upon burn termination.

The system design is similar in nature to those built by other universities. [1]\[2]\[3]\[4]

The theory of operation is fairly simple. The control of the static firing sequence will be done with a laptop computer running a small script that will communicate out a serial port to a ‘Flextek’ I/O board. This board is capable of data collection through several 10-bit A/D channels and the board is also capable of triggering single events through several output channels.

At T-2 seconds the control board will signal the igniter to start. This signal will trip a small igniter relay, which will dump a larger voltage and current to the igniter from a 12v battery.

Immediately after igniter start the control board will signal the actuator solenoid relay. The relay will channel power from the 12v battery to the actuator solenoid, the actuator solenoid will in turn switch on the 80psi gaseous nitrogen source to the pneumatic actuator. The pneumatic actuator turns a stainless steel ball valve, which will turn on the gaseous oxygen source to the motor.

The gaseous oxygen flow, once started, will travel from the ball valve through a check valve that will protect the oxygen plumbing system in the event of an over-pressurization situation in the combustion chamber. Once the oxygen flows through the oxygen check valve it will go through the metering orifice. This is a small flat plate style orifice that will regulate the flow through it to the exact volume needed to react with the paraffin for optimal combustion.

The gaseous oxygen will then be injected into the combustion chamber through a brass injector/diffuser that insures the oxygen will be turbulent and not have a large velocity down the central port of the paraffin fuel grain.

The motor should burn for approximately 10 seconds at 50 lbf of thrust.

The controller will handle burn termination by de-energizing the actuator solenoid. This will cause the pneumatic actuator to lose pressure and therefore close the ball valve.

Once oxygen flow has been halted the controller will signal the purge solenoid relay. The purge solenoid relay will provide power from the 12v battery to the nitrogen purge solenoid, which will open the flow of nitrogen from the source. The nitrogen will then flow through the check valve and then into the combustion chamber.

The nitrogen will serve two functions. The first is to extinguish the motor from any residual burning from oxygen still in the system or air coming back into the combustion chamber through the nozzle. Second is to cool the graphite nozzle after firing to hopefully reduce the possible effects of stored heat in the graphite further melting the remaining paraffin in the combustion chamber. We would like to keep the paraffin undamaged after firing so we can do a post-mortem analysis to look at the regression. Once the system has finished firing and purging and is deemed safe the excess pressurized oxygen and nitrogen stored in the 12’ and 25’ feed lines can be discharged thorough the manual purge valves.

Once the system has cooled. We can remove the forward nozzle-retaining flange and remove the spent fuel and nozzle and replace it with a new nozzle and fuel grain and refire.

<div>
  <center>[[!img HybridPlumbing/plumbingv30.jpg size="640x467"]]</center>
</div>

**Additional Information:**

- [[HybridSolenoids]]
- [[Valves and Regulators|ValvesRegulators]]
- [[Metering orifice|MeteringOrifice]]
- [[Hoses and connectors|HosesConnectors]]

**References:**

**[1]** AIAA-93-2610 "The Rapid and Low Cost Development of a Hybrid Rocket Motor" K.W. Schulze, S.A. Meyer June 1993 (Gencorp-Aerojet Inc.)

**[2]** "A Labscale Hybrid Rocket Motor for Instrumentation Studies" Robert Shanks, M. Keith Hudson Summer 2000 (University of Arkansas)

**[3]** AIAA-2001-3535 "Combustion of HTPB-Based Solid Fuels Containing Nano-sized Energetic Powder in a Hybrid Rocket Motor" Grant A. Risha, Abdullah Ulas July 2001 (Pennsylvania State University)

**[4]** AIAA 2003-1162 "Scale-up Tests of High Regression Rate Liquefying Hybrid Rocket Fuels" M. Arif Karabeyoglu, Greg Zilliac Jan 2003 (Stanford University)

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Attachments:

- [[plumbingv1b.vsd]]
- [[plumbingv1c.vsd]]
- [[plumbingv21.vsd]]
- [[plumbingv22.vsd]]
- [[plumbingv30.vsd]]