The efficiency of internal combustion engines depends on several factors, the most important of which is
the expansion ratio
. For any heat engine the work which can be extracted from it is proportional to the difference between the starting pressure and the ending pressure during the expansion phase.
What causes an engine to be less efficient?
Abstract: The conversion of fuel energy into useful work in an internal combustion engine involves a number of loses. These include the
chemical energy loss in emissions
, heat losses from the engine and through the exhaust gas, and gas pumping and friction losses in the engine.
How is engine efficiency calculated?
An Example
If 200 joules of thermal energy as heat is input (), and the engine does 80 J of work (), then the efficiency is 80J/200J, which is 40% efficient. This same result can be gained by measuring the waste heat of the engine.
Why does engine efficiency increase with load?
engine efficiency
increases as load increases
, however, air drag losses increase as the square of the speed. There are two major reasons for the poor efficiently at low load: At low load, a significant percentage of the work done is used to overcome engine friction.
How can we increase the efficiency of an engine?
- Run the engine fuel-lean, that is, use excess air. It is well known that fuel-lean running improves the efficiency. …
- Higher compression ratio. …
- We need new cycles put into practical use. …
- Run the engine at optimum conditions, meaning low friction (modest engine speed) and low pumping work (air throttle more open).
Which engine has highest efficiency?
The Stirling cycle engine
has the highest theoretical efficiency of any thermal engine but it has a low output power to weight ratio, therefore Stirling engines of practical size tend to be large.
What is the most efficient engine ever?
The Wärtsilä 31
is quite simply the most fuel efficient, user friendly, versatile engine ever developed. The Wärtsilä 31 is not one single engine, but rather a platform consisting of three different products – a diesel engine, a gas engine and a dual-fuel engine.
What are the signs of a bad fuel injector?
- The Engine Misfires. Dirty fuel injectors may cause your vehicle’s engine to misfire. …
- Idling Gets Rough. …
- Your Gas Mileage Tanks. …
- The RPM Needle Starts to Dance. …
- Your Car Won’t Start.
How often should spark plugs be changed?
And as a general rule, we recommend replacing spark plugs
every 30,000 miles
, which falls in line with most manufacturers’ recommendations. You can check your owner’s manual or the manufacturer’s website for information specific to your make and model vehicle.
How can you tell when a spark plug is bad?
- Your car is a rough starter. …
- Your car is a rough idler. …
- Your engine will sometimes misfire. …
- Your engine surges. …
- Your fuel consumption is higher than usual. …
- Your car isn’t accelerating as it should.
How do you find efficiency?
The work efficiency formula is
efficiency = output / input
, and you can multiply the result by 100 to get work efficiency as a percentage. This is used across different methods of measuring energy and work, whether it’s energy production or machine efficiency.
What is a good volumetric efficiency?
Volumetric efficiencies
above 100%
can be reached by using forced induction such as supercharging or turbocharging. With proper tuning, volumetric efficiencies above 100% can also be reached by naturally aspirated engines.
What is the efficiency of an engine?
According to MDPI, gasoline engines have a thermal efficiency of
between 30% and 36%
while diesel engines can reach a thermal efficiency of almost 50%.
What feature of an engine has the greatest effect on volumetric efficiency?
13.4.
Re-expansion
has by far the greatest effect on volumetric efficiency.
Which engine is more efficiency 2 stroke or 4 stroke?
But there is a loss of fuel in 2 stroke engines during scavenging which affects their efficiency. Power density would be greater in 2 stroke.
2 stroke engine
is more efficient than four stroke.
How can we increase the efficiency of Otto cycle?
1. an ideal thermodynamic combustion cycle, as follows: a compression at constant entropy; a constant-volume heat transfer to the system; an expansion at constant entropy; and a constant-volume heat transfer from the system. The thermal efficiency of the ideal Otto cycle increases
with an increasing compression ratio
.
