Thermoacoustic engine working principle

      

  From the acoustic point of view, it comprised a closed-ended ‘bounce volume’, a hot-end heat exchanger, a thermoacoustic stack, and a cold-end heat exchanger, terminating in a flange onto which the linear alternator would have been bolted, all enclosed in a duct of approximately constant cross-section. The bounce volume was necessary to allow useful magnitudes of acoustic velocity in the stack, but it also provided the radiant surface for transmission to the hot-end heatexchanger. The overall length of the duct was short compared with the acoustic wavelengths to be generated because their frequency was determined by the resonant frequency of the alternator.

Different Types of Metal Fabrication Processes

 

There are numerous types of metal fabrication processes used to transform raw metal materials into useful parts and components by using various metal working tools and fabrication machinery. Some of the more frequently used processes include:

Stamping: The metal is pressed in between a stamp die to create a raised section of the metal.

Punching: A punching tool is used to punch holes in the metal to create the desired part or component.

Cutting: Various cutting methods are used to cut the metal to the right size.

Folding: Sometimes the metal needs to be bent at a specific angle, and folding is used to achieve this result.

Machining: Machining processes carefully remove metal and reshape it into the end product and involve using drills, CNC lathes, and other such machinery.

Welding: This process involves heating two pieces of metal together.

Shearing: Shearing is creating one long single cut on metal sheets to cut it to the correct size.

Computational Fluid Dynamics

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Oil Fired Furnace ?

             Furnace oil is the major fuel used in oil fired furnaces, especially for reheating and heat treatment of materials. LDO is used in furnaces where presence of sulphur is undesirable. The key to efficient furnace operation lies in complete combustion of fuel with minimum excess air. Furnaces operate with efficiencies as low as 7% as against upto 90% achievable in other combustion equipment such as boiler. This is because of the high temperature at which the furnaces have to operate to meet the required demand. For example, a furnace heating the stock to 1200o C will have its exhaust gases leaving atleast at 1200o C resulting in a huge heat loss through the stack. However, improvements in efficiencies have been brought about by methods such as preheating of stock, preheating of combustion air and other waste heat recovery systems. 

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How the Furnace Energy Supply Works?

           

                    Since the products of flue gases directly contact the stock, type of fuel chosen is of importance. For example, some materials will not tolerate sulphur in the fuel. Also use of solid fuels will generate particulate matter, which will interfere the stock place inside the furnace. Hence, vast majority of the furnaces use liquid fuel, gaseous fuel or electricity as energy input. Melting furnaces for steel, cast iron use electricity in induction and arc furnaces. Non-ferrous melting utilizes oil as fuel. 

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Characteristics of an Efficient Furnace ?

              Furnace should be designed so that in a given time, as much of material as possible can be heated to an uniform temperature as possible with the least possible fuel and labour. To achieve this end, the following parameters can be considered.

• Determination of the quantity of heat to be imparted to the material or charge.

• Liberation of sufficient heat within the furnace to heat the stock and overcome all heat losses.

• Transfer of available part of that heat from the furnace gases to the surface of the heating stock. 

• Equalisation of the temperature within the stock.

• Reduction of heat losses from the furnace to the minimum possible extent. 

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Types and Classification of Different Furnaces?

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CHEMICAL PROCESSING FOR FURNACE?

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PHYSICAL PROCESSING FOR FURNACE ?

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What are the components of a furnace?

The principle components are

i. Source of energy
a) Fossil fuel: For fossil fuel one requires burner for efficient mixing of fuel and air. Arrangement of burner is important.
b) Electric energy: Resistance heating, induction heating or arc heating.
c) Chemical energy: Exothermic reactions

ii. Suitable refractory material: Refractory design is important. Thermal enclosure of the furnace is designed and constructed keeping in view the requirements. For example refractory facing the thermal enclosure must have high refractoriness, chemically inert etc. Whereas refractory facing the surrounding must have low thermal conductivity to minimize heat y installing a heat exchanger or internally by recirculation the POC within the ntation and control: Furnaces are equipped with POC analyzer and temperature control. urnaces and their applications in high temperature industries: escription in order to appreciate the requirement of the design of thermal enclosure, i.e. furnace): PHYSICAL PROCESSING losses

iii. Heat exchanger:

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What is a furnace?

              A furnace is essentially a thermal enclosure and is employed to process raw materials at high temperatures both in solid state and liquid state. Several industries like iron and steel making, non ferrous metals production, glass making, manufacturing, ceramic processing, calcination in cement production etc. employ furnace. The principle objectives are a) To utilize heat efficiently so that losses are minimum, and b) To handle the different phases (solid, liquid or gaseous) moving at different velocities for different times and temperatures such that erosion and corrosion of the refractory are minimum. 

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Countermeasure against molding defect ?

Defect
Warpage

Cause
1. Inappropriate gate location
2. Un even molded product thickness
3. Design of undercut, rib, and boss is inappropriate
4. Lack of cooling
5. Large anisotropic of shrinkage ratio

Countermeasure
1a. Change the gate location.
1b. Add the gates.
2. Try to make the molded product thickness even.
3. Change the design, thinking about warpage.
4. Drop the mold temperature, and make the cooling time longer.
5. Use the low warpage grade.

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Countermeasure against molding defects?

Defect
Strength poverty 

Cause
1. Lack of drying
2. High resin temperature
3. Too much cushion volume
4. Shear heat generation at the runner and the gate
5. Residence time too long

Countermeasure
1. Preliminary dry the pellet well enough
2. Drop the cylinder temperature
3. Reduce the cushion volume
4. Make the runner and the gate bigger, and shorten the gate land.
5a. Use the molding machine with appropriate injection volume(about 1.5 to 3 times more than the cavity volume)
5b. If resin remains inside the cylinder by some kind of trouble, resume molding after purging it.  

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Selection of injection machine?

* Select by injection volume

* Select by mold clamping pressure

* Nozzle structure

* Injection mechanism

* Backflow prevention ring

* Drying machine

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Selection of injection machine Nozzle structure ?

                Open nozzle is common when molding NOVADURAN. The nozzle of commercially-supplied injection machine can be open nozzle or shut-off nozzle (Figure 1-1) but in any type, it is necessary to have a temperature control. If drooling from the nozzle is concerned, use the shut-off nozzle. However, it might cause burn and sunspot object by resin retention at the slide part, so be careful.  

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Selection of injection machine by mold clamping pressure ?

               Both toggle type and direct pressure type is suitable when molding NOVADURAN. The relation of molded product projected area A(cm2 ) and required mold clamping pressure P(ton) should be in the range indicated below.

 P ＝ （0.5～0.7）×A  

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Selection of injection machine by injection volume?

               As a guide, generally the injection machine should be selected so that molded product volume will become 30% to 80% of the machine's injection volume. When molding, the relation of the machine's injection volume Q(g) and one shot weight (sprue and runner weight included) W(g) should be in the range indicated below. 

 Q ＝ （1.3～1.5）×W

                       If the injection volume is too small, plasticization will not make it, and might lose its original physicality as a molded product because the resin will be sent without enough plasticization. On the other hand, if the injection volume is too big, residence time inside the cylinder will be longer and cause degradation by more chance. 

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Types of Injection machine ?

（1） Horizontal injection machine ：
                      Both mold clamping device and injection device compounded horizontally

（2） Vertical injection machine ：
                      Both mold clamping device and injection device compounded vertically

（3） Two-color injection machine

（4） Rotary injection machine

（5） Low foam injection machine

（6） Multi material injection machine

（7） Sandwich injection machine

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Injection Molding

               The injection machine is a machine that melt plasticize the molding material inside the heating cylinder and inject this into the mold tool to create the molded product by solidifying inside it. The injection machine is constructed of a mold clamping device that opens and closes the mold tool, and device that plasticize and inject the molding material.

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Types of patterns used in sand casting?

(a) solid pattern

(b) split pattern

(c) match-plate pattern

(d) cope and drag pattern

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Sand Casting?

               Sand Casting is simply melting the metal and pouring it into a preformed cavity, called mold, allowing (the metal to solidify and then breaking up the mold to remove casting. In sand casting expandable molds are used. So for each casting operation you have to form a new mold. 

• Most widely used casting process

. 

• Parts ranging in size from small to very large 

• Production quantities from one to millions

• Sand mold is used.

• Patterns and Cores – Solid, Split, Match-plate and Cope-and-drag Patterns – Cores – achieve the internal surface of the part 

Advantages of casting?

Advantages

• Design flexibility

• Reduced costs

• Dimensional accuracy

• Versatility in production

Disadvantages

• Lot of molten metal is wasted in riser & gating

• Casting may require machining to remove rough surfaces

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Casting and types of Casting?

Casting Casting is the process of producing metal parts by pouring molten metal into the mould cavity of the required shape and allowing the metal to solidify. The solidified metal piece is called as “casting”.

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