Sunday, June 17, 2012

Types of internal combustion engines


Types of internal combustion engines



1.  Types of internal combustion engines:


1.1. According to configuration

§  Reciprocating

§  Rotary

§  Continuous combustion


1.2. According to engine cooling method

§  Air cooled

§  Water cooled


1.3. According to fuel used

§  Gasoline engine

§  Diesel engine

§  Natural gas engine


2.  Types of reciprocating engines


2.1. According to number of strokes

§  Two stroke

§  Four stroke

§  Five stroke

§  Six stroke


2.2. According to cylinder arrangement

§  Inline engine

§  Radial V engine

§  W engine


2.3. According to number of valves per cylinder

§  Two valves per cylinder

§  Four valves per cylinder


2.4. According to swept volume

§  Fixed displacement engines

§  Variable displacement engines


3.  Types of rotary engines

§  Wankel engine

Saturday, June 16, 2012

Comparison between natural gas, electric, and induction cooktops


This comparison is just qualitative and not quantitative with no numerical facts or typical values. This comparison is inspired by some videos on YouTube and some data in ElectroLuxAplliances.com.




Natural gas cooktop
Electric cooktop
Induction cooktop
Electric supply
Optional for spark
Essential
Essential
Heating power
Small
High
Very high
Boiling time
Large
Small
Very small
Pan material
Any heat conductive material
Any heat conductive material
Heat conductive material which attracts to magnets
Cooktop components heating
Heated
Heated
Only pan is heated
Heating area
Constant. Different heating areas are provided by using different eyes.
Constant
Dependent on pan base area
Putting hand on cooktop’s surface
Burning hazard
Burning hazard
No burning
Heating power control
Control gas flow rate
Control electric current
Control electric current

If flame is fade out, an external source is required to ignite the gas to continue heating
If electricity is out for certain time, the heater will continue heating when electricity is back
If electricity is out for certain time, the heater will continue heating when electricity is back
Mechanical maintenance
Difficult and required after small operating periods due to blocking of gas paths and galleries
Not required
Not required
Plug and play
Requires some setup. Difficult
Easy
Easy
Outdoor operation in strong winds, sandy environments, very cold places
No
Yes
Yes
Boil over effect
§  Kills flame
§  Requires cleaning after boil over
§  Requires re-ignition
§  Hazardous
Continues heating when boil over takes place
Continues heating when boil over takes place
Cleaning and washing
Difficult
Easy
Easier
Flexibility to move cooktop to another place
Difficult
Easy
Easy
Effect on inhaling in closed rooms (places)
Dangerous due to emission of carbon dioxide and monoxide
No effect
No effect
Hazard propagation
Wide (global) due to propagation of natural gas when flame is killed and natural gas is fed to the cooktop
Local
Local
Operating cost (in Egypt)
Low
High
High
Maximum temperature
Low
High
Very high
Pan blackening
Yes, because of carbon content of exhaust gases
No
No
Burning of plastic handles
May be burnt due to direct flame
No
No
Direct visual inspection of heat power
Easy
Hard
Very hard


Wednesday, June 13, 2012

Electric water heater dimensions

Electric heater dimensions constraints for a given storage volume

Almost all electric water heaters used nowadays in our houses are of cylinderical shape.
May be this cylinderical shape has little artworks on it or some extra features on its surface, but it is still a cylinder. So how to estimate the dimensions of an electric water heater in a new design. The dimensions are simply radius and height of the cylinder. The following constraints may affect the dimensions of an electric heater with a given storage volume:


1. Minimal sheet metal surface area for a given sheet metal thickness... Cost criteria

2. Accessibility criteria.

3. Minimal insulation material criteria...cost criteria

4. Water head required criteria to provide satisfactory flow rate for washing or showering.

5. complete water consumption criteria. The heater tank should be placed in a position that when a faucet is opened the whole water inside the tank may be used, knowing that the height of a typical floor 2.9 meters.

6. Minimum area of the place where the heater will be placed

Tuesday, June 12, 2012

Linear guidance systems


v Shaft guidance system:

§  Shaft (solid or hollow)

§  Linear bearings (closed or open)

§  Shaft support blocks

v Monorail guidance system:

§  Guide rail

§  Monorail bearing

v Track roller guidance system (not used in CNC routers):

§  Track

§  Carriage with track roller

v Deep groove ball bearing in right angle configuration

Linear motion drives for CNC router


v Ball screw (problems: backlash, not self –locking, expensive)

v Lead screws/power screws/translations screws: (efficiency 25%-70% , higher pitches result in higher efficiencies)

§  Acme screw (cheap, small/no backlash. Small pitch and slow speeds)

§  Square screw (most efficient, least friction, most difficult to machine, and most expensive)

§  Metric V thread (lowest efficiency)

v Rack and pinion
The following table shows a quick comparison between lead screw and ball screw as they are almost used in hobby CNC routers


Point of view
Lead screw
Ball screw
Efficiency
Linear speed
Slow
High
Self-locking
In most
No
Cost
Relatively cheap
Expensive
Manufacturing
Easier
Difficult
Backlash
Small
Large
Backlash compensation
Using Anti-backlash nut
Using software
Pitch
Small
Large