I&EC REPORTS & COMMENTS Liquid fuels in solid propellants Measuring mass flow rate directly N e w concept of the old sand bath
MORE POWER FOR SOLID PROPELLANTS
MODIFIED ORIFICE METER GIVES MASS FLOW RATE DIRECTLY
The honeycomb, one of the oldest and most useful of structures, is now shooting for a new use-as a structural framework f o r solid rocket engines. More of today’s large rockets use solid fuel because these fuels are reliable and ready to go instantly. But those in general use today are some 15y0less powerful than very high energy liquid fuel systems. T o increase performance in solid rockets, there are two courses open: cut back weight of inert parts of the rocket or boost the energy of the system. Cutting back weight can pay off, but only to a limited extent. Boosting the energy then is the most likely way to get better performance. Many chemical combinations that might yield very high energy are not compatible. They can’t be intimately mixed or stored with safety. With rocket engines getting larger all the time, physical strength becomes a problem and propellants can crack or creep out of shape. With higher energy fuels, the problem might be more severe. Ways to support solid motors internally and use fuels and oxidizers that are normally incompatible has been the goal. Hexcel Products, Berkeley, Calif., manufacturers of high strength-toweight structures, mostly for aircraft framework, felt that a honeycomb might do the job. It could be made of aluminum or some other reactive material that would burn as the fuel was consumed. The cellular structure would add strength to the solid propellant. Hexcel has supported a Stanford Research Institute project, under contract to the Advanced Research Projects Agency, since 1958. The
With an arrangement that strongly resembles a Wheatstone bridge, the familiar orifice meter can be modified to measure mass flow rate directly. Such a unit gives a pressure drop that is directly proportional to mass flow rate, plus the added advantage of handling low flows without the hindrance of fluctuating orifice coefficients. Further, it has a wide range, only one moving part (sometimes two), and costs less than a turbine or gyro mass flowmeter. The operating principle is simple. Add to the usual orifice in the line another one downstream from it. Then install two side streams, with pumps. One side stream flows from in front of the first orifice to the space between the two; the other from behind the second orifice to the space between the two. The flow from the latter merges with that from the former as they enter the intermediate space. Subtracting the pressure drops across the two orifices-the same as measuring the drop across the whole assembly-gives a result that is proportional to the first power of the mass flow rate. All the squared terms cancel each other. Using four orifices and only one pump leads to the system that looks so much like the Wheatstone bridge. And there are other arrangements too. Choice among them depends on line pressure and flow rates in the system under consideration. The recirculating flow, permitting higher flow rates in the unit, gets around the problem of variable orifice coefficients at low flows. Further, it gets the pressure drop across the assembly into a range
1ncorn;batible fuels and oxidizers in the same rocket engine
can be
used
project has as its aim to check out the use of honeycombs in rocket propulsion. A team from SRI’s Propulsion Sciences Division, headed by Leland Christensen, loaded 2and 5-inch diameter cylindrical motor grains. These burned smoothly and safely even with uncured and unbonded propellants, consuming the honeycomb wall as firing progressed. I n later tests, SRI checked isolation of incompatible ingredients using the honeycomb wall as a barrier. This was also satisfactory. A gelled liquid was found to interact as a solid and burn stably on ignition. Besides cylindrical honeycombs, SRI has checked out other grain configurations. These include tubular grains, where the central core of the cylinder is open, and sandwich grains, where tubular honeycombs filled with fuel are alternated with solid oxidizer that is not supported by honeycomb.
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NO. 1 0 O C T O B E R 1 9 6 2
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I&EC REPORTS
= liquid densit) Q = volumejaw lute
p
where standard differential pressure transducers can handle it. On the other hand, since recirculating flow must be at constant volume, the meter can’t be used for gases. This sort of meter, developed b y Simmonds Precision Products, Tarrytown, N. Y., can handle flows from as low as 0.5 pound per hour up to about 500 pounds at line pressures up to 1000 p.s.i.g. and temperatures up to 350’ F. Accuracy is 0.5% of range, the company says. And pressure drops can be tailored to any convenient range bet\veen 10 and 200 inches of water.
CARTRIDGES NEED LABELS Marking is a manufacturer’s obligalion; recognizing is n user’s necessity The pocket size oxygen dispenser we described in April has led us, through a reader, along an interesting path of investigation to both a reassurance and a warning. The reader asked: “On page 11 12
q = volume j o o w rate of recircu/afingJow
)ou show a picture and include information on an oxygen inhaler. Further in the article you compare the oxygen cartridge to a COz cartridge. Did you ever think what could happen if someone made a mistakr and used the wrong one?” We hadn’t because the original package is clearly marked with proper warning about usage, and the replacement cartridge is bright red with large black letters saying, “Caution. Keep Away from Heat and Oil. U . S . P . Oxygen.” Small high prassure gas cartridges of this type were originally developed for carbon dioxide service. A familiar use for such COz cartridges is to provide an expellant gas in to)s. But in addition to COZ, the Compressed Gas .%sociation tells us, they have been extended not only to oxygen but to butane and nitrous oxide as well. W e have seen recent advertisements in household magazines offering long-burning candles using butane cartridges. IVith the wider application of these
INDUSTRIAL A N D ENGINEERING CHEMISTRY
cartridges, the hazard of misapplication increases ; the need to properly identify the cartridges becomes increasingly important. Two and a half years have passed since the incident where a 14-year old boy blew thrce fingers off his right hand when he put an oxygen cartridge in a BB pellet gun made to operate safely with C O z cartridges. At that time the Ohio State Fire Marshal found on the market both oxygen and C O Z cylinders with the same shape, both painted green. The Compressed Gas Association alerted its members to the need for proper labeling. CGA on one occasion has seen six similar cartridges-three containing COZ, two butane, one oxygen. The three COz cartridges and one of the butane cartridges were not labeled. We hope that the good job of labeling done by the Val-U-Air Products on their oxygen dispenser is more representative of cartridge identification today. We believe the manufacturer has a direct responsibility to both color and mark his cartridge; he who uses, of course, must also read.
LAB-SCALE HEATING BATH A neat arbstt’er to a dzficult laboratory problem Liquid baths are undoubtedly the most convenient method of holding constant temperature. Where real liquids fall short, fluidized beds may do the job. A compact unit, using sand as the medium of transferring heat, is being marketed by Techne (Cambridge) Ltd., of Princeton, N. J. The inner vessel of the unit shown on page 14 contains sand, supported by a porous plate. Electricity for heaters (just above the support plate) and air for fluidizing must be supplied. The vessel or part to be heated is (Continued on page 14) Circle
No. 33 on Readers’ Service C a r d - - - +
GDSOB and GDlOOB Series Regulators offer you 3 methods of control to fit vour requirements
’t’;r”R
GD92B and GD102B REGULATORS controlled by:
n
LV20 LOAD VALVE
LR SERIES LOADER REGULATORS
BV20 BLEED VALVE
Stainless steel or bronze with stainless trim. For panel mounting. Inlet: 10,000 psig. Provides economical, positive, independent valve control.
SPECIFlCAT10NS
-
GD93B and GDlO3B REGULATORS controlled by:
Flow: GD90B Series to 15,000 scfm. GDlOOB Series to 45,000 scfm. Materials: Bronze, stainless steel, or aluminum. Characteristics: Compensated type, constant outlet pressure. Actuation: Dome loaded. inlet pressure: 6,000 psig. Proof pressure: 12,000 psig. Burst pressure: 24,000 psig. Operating temp.: -67” F. to + 1600F. Storage: -800 F. Leakage: Zero. “0”Ring and diaphragm material: Neoprene. Seat material: Nylatron-GS,
Bronze, aluminumInlet: 7,000 psig. Stainless steelInlet: 10,000 psig. Outlet range: From 25-7,000 psig. Outlet range on stainless: 25-10,000 psig. Flows: To 20 scfm. Torque: 40 in. Ibs. at 7,000 psig. 60 in. Ibs. at 10,000 psig. Provides accurate, safe, pilot regulator-type control.
LVlO LOADER VALVE Bronze, stainless steel, aluminum. Inlet and outlet: 7,000 psig. Flow: To 10 scfm. Provides simple, finger-tip valve control. Loads 30” clockwise; bleeds 30” counter-clockwise; returns to neutral automatically.
GD91B and GDlOlB REGULATORS Remotely controlled by any of the control devices shown here.
LOCKUP and FLOW CHARACTERISTICS LOCKUPPRESSURE
0 LOCKUP
50% OPEN VALVE POSITION
100% OPEN
Corn ensated gas-o-dome reguktor operated with load &bleed valves or LVlO loader valve
VICTOR high pressure gas regulators are cleaned, assembled, tested and packaged under carefully controlled conditions to insure maximum product reliability. Cleaning is performed to Victor standards or to customer specifications in a clean room approved by industry and military agencies. Regulators shown here are typical of the available models covering a range of pressures to 10,000 psig. and capacities to 80,000 scfm. at -67” F. to +250” F. Other types, sizes, a n d modifications for special applications, available upon request outlining your requirements. For further information, Bulletins on above models available on request; or write for Regulator Inquiry Form 361-B.
\r’iTi;lTo”R E ~ U ~ P M E’N I rs
GD94B and GD104B REGULATORS controlled by:
844 Folsom Street, San Francisco 7 3821 Santa Fe Ave., Los Angeles 58 1145 E. 76th St., Chicago 19
LOCKUP PRESSURE
0 LOCKUP
50% OPEN VALVE POSITION
100%
OPEN
Corn ensated gas-o-dome regupator operated with loader regulator
88 Manufacturers regulators; welding of highB pressure cutting and equipment; large volume hardfacing gas rods; blasting nozzles; cobalt & tungsten castings; straight-line and shape cutting machines; tractor roller, track, and idler rebuilding machines.
I&EC REPORTS
ROTARY DRYERS, HEATERS AND COOLERS /-
I I
Semi-Direct Heat, Double-Shell Dryer, ideal for coal drying. Cross Section of SemiDirect Heat, DoubleShell Dryer showing lifting flights on inner and outer shells. Indirect-Heat, Double-Shell Dryer for kaolin, chalk, china clay, etc.
,
I
Rotary Steam-tube Dryer designed for raw chemicals.
Single-Shell, Direct-Heat Dryer Parallel or Counter-Flow for sticky organic or inorganic materials.
placed within the sand chamber. A thermostat about mid-height in the sand bed can be set to hold the desired temperature. An insulated jacket keeps the outside cool during. operation. T h e new heating bath can work easily at temperatures over 600” F. For comparison, oil baths arz convenient only to about 300’ F., at which point sludge beqins to form. The fluidized bed retains such characteristics of a liquid bath as accessibility, uniformity of tPmperature, and good heat transfer. Unlike liquid metal baths, the sand does not
Cross section of Indirect Heat Dryer. “A” I S the completely isolated space in which the material is dried. “B” is the inner hot gas passage. “C” represents the V-ducts for the gas return.
_- “.
Cross section view of Steam-Tube Dryer.
Hot-Air Dryer for drying inorganic salts and similar materials.
€a Thr fluidized-bed heating bath operutes eusik\i at temperatures abooe 600‘ F. Rotary Kiln for continuous calcining, roasting or oxidizing.
Cross section of singleShell
I Rotary Cooler for continuous cooling of hot materials after drying or calcining.
I
-
Heat
Ask for our NEW Catalog on Dryers, NO. 16-E-12
Circle No. 16 on Readers’ Service Card
14
Direct Dryer.
INDUSTRIAL A N D ENGINEERING C H E M I S T R Y
conduct electricity, therefore electrical measurements can he made during operation. Unlike molten salt baths, sand is not corrosive. And the fluidized bed can be used for both high and low temperatures. Temperature control cannot be held quite as well as it can in a liquid, because of thz low specific heat of a fluidized solid. But this same factor gives fast heating. To increase acceptance of the new system, the fluidized sand even looks like a hubbling, boiling liquid.
