Ae4506162164

Sharadkumar K. Chhantbar Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 5( Version 6), May 2014, pp.162-164
www.ijera.com 162 | P a g e
Screw Extruder for Pellet Injection System
Sharadkumar K. Chhantbar
PG student, A. D. Patel Institute of Technology, New V. V. nagar, Anand, Gujarat, India
Abstract— Solid hydrogenic pellets are used as fuel for fusion energy reactor. A technique for continuous
production of solid hydrogen and its isotopes by a screw extruder is suggested for the production of an unlimited
number of pellets. The idea was developed and patented by PELIN laboratories, Inc. (Canada). A Gifford
McMahon cryocooler is used for the generation of solid hydrogenic fluid pellets. Requirements of the pellets is
depends upon the energy to be produced by tokamak. This review paper focuses on the model for the screw
extruder for solidification of hydrogen ice having high injection reliability.
Keywords: screw extruder, cryocooler
I. INTRODUCTION
Future fusion reactors should be equipped
with a fuelling system operating in a steady state
mode. There are three techniques for plasma fuelling:
by gas puffing, by compact toroids and by injection
of pellets produced from solidified hydrogen
isotopes. A key task of the injection is to develop a
reliable pellet injector capable of injecting, in the
steady state mode, an unlimited number of pellets
into the plasma core. Several techniques for
continuous pellet production have been proposed.
One is a screw extruder type pellet injection system.
Another technique is to produce pellets by a porous
pellet generator. Recently the screw extruder type
pellet injection system has been designed and tested.
II. DEVELOPMENT OF EXTRUDER
TYPE PELLET INJECTOR
R. Viniar et. al., Developed a screw
extruder to produce a deuterium ice in 2000. A
cylindrical rod of 2 mm in diameter and 100 m in
length was extruded over 3000s. The deuterium
solidifies by a liquid helium heat exchanger. A
schematic diagram of the pellet injector is shown in
Figure1. It consists of vacuum chamber (1) with an
extruder (2), which equipped with helium heat
exchanger (3) and screw (4), A rotating driver (5)
connected to screw, A propellant gas valve (6),
chopper (7), a gun barrel (8), and diagnostic chamber
(9). A transparent chamber (10) is attached to the
extruder exit and equipped with pumping system
(11).
Figure 1 Schematic Diagram of the Pneumatic
pellet injector with a screw extruder. [I. Viniar et.
al, 2000]
R. Sakamoto et. al., in his paper
“Development of advance pellet injector systems for
plasma fueling” in 2008, the cooling is done by cryo-
cooler instead of liquid helium. Its key design futures
are as follows,
 Cooling by compact cryo-coolers: the pellet
injector is operated using electrical input only,
which is the most fundamental facility in a
laboratory, instead of a complicated liquid
RESEARCH ARTICLE OPEN ACCESS

helium supply system. This design enables
flexible and reliable operation.
 Screw extruder for solid hydrogen production:
The screw extruder can produce solid hydrogen
rod via simultaneous replenishment, liquefaction,
and solidification of hydrogen gas. This design
steady state operation in principle.
 Pneumatic pipe-gun acceleration: the design
enables reliable and reproducible pellet injection
with easy injection-timing control.
The screw extrusion concept, which was
proposed by Mitsubishi Heavy industry and
developed by PELIN L laboratory, can produce a
solid hydrogen rod continuously. A conceptual
drawing of the screw extruder is shown in Fig.1.
There are two Gifford-McMahon cycle 4 K cryo-
coolers to cool the cryo-cylinder, the total cooling
capacity of the cryo-coolers is 20 W at 8 K. The
lower part of a copper cryo-cylinder is cooled to
below 6 K in the standby phase.
Figure 2 Conceptual drawing of screw extruder
[R. Sakamoto et. al, 2008]
Hydrogen gas is pre cooled in a heat
exchanger at the same temperature with the thermal
shield, and then flows onto the cooper cryo-cylinder
to be liquefied and solidified, while the solid
hydrogen rod is extruded by the rotating screw from a
nozzle (Fig.2).
Figure 3 Solid hydrogen Road [R. Sakamoto et. al,
2008]
J.W. Leachman et. al., in his paper “Model
of a Twin-Screw Extruder operating with a
Cryocooler for the Solidification of Deuterium” in
2009, Analysis carried out using the numerical
model. Nine parameters are considered in his
sensitivity analysis.
Figure 4 Sensitivity of extruder performance
[J.W. Leachman et. al, 2009]
Figure 4 indicates that the extruder
performance is most sensitive to two-phase
convection coefficient, Followed in order by latent
heat of fusion, Liquid convection coefficient, and
liquid heat capacity.
III. CONCLUSION
The sensitivity of extruder
performance is complex to control due to two phase
flow. Among two methods of producing solid
hydrogen and its isotopes, the GM cryocooler based
cooling system is preferable to control load capacity
over liquid helium heat exchanger system.

REFERENCES
[1] R. Viniar et al., “10 Hz Deuterium Pellet
Injector for 1000 s Continuous Fuelling”,
2000
[2] R. Sakamoto et al., “Development of
Advanced Pellet Injector Systems for
Plasma Fuelling”, Journal of Fusion
Engineering and Design, 2008
[3] J.W. Leachman, “Model of a Twin-Screw
Extruder Operating with a Cryocooler for
the Solidification of Deuterium”, 2009

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