Posts

Maintenance Tip of the Week: Air Filters 01/11/2015

Maintenance Tip of the Week – Air Filters 09/28/2015

Air filters are often neglected or forgotten as part of a maintenance plan. Always ensure that air filters are changed as suggested by your manual’s maintenance schedule. As a part of the combustion process, a supply of clean air is always required by the engine.

What happens if you put gasoline into a diesel engine?

 

Don’t do it.

Seriously.

Don’t try it.

At best, you will ruin your engine. Quickly.

At worst, you could start a fire.

Why would someone try this? There is normally no financial incentive, since gasoline, or petrol, is normally more expensive than diesel. When this situation happens, not too commonly with marine engines, in our experience it is a mistake when filling the tank. Somebody grabs the wrong hose.

But, you may ask, if diesel and gasoline both are distilled from petroleum, why is that a problem?

The answer lies in the way ignition of the fuel is made. Gasoline uses a spark ignition system that, when the fuel is mixed with air at the proper moment in time, combustion occurs.

On the other hand, diesel engines are based on the principles of self-ignition (there are no spark plugs). The heat from compression is what causes ignition, rather than a spark. When gasoline is introduced into the engine, it might ignite in the combustion chamber, it may not ignite, or it may ignite at the wrong time, possibly even within the exhaust system. The best case scenario? You have ignition at the wrong time in the cylinder, ruining the cylinder, piston, and cylinder head. Why is this bad? You have just introduced an explosion in a part of the engine that was never intended to contain an explosion.

Unfortunately, when such mistakes occur, there is normally very little recourse other than to drain the fuel system, and repair the engine, with a complete rebuilding usually required. That is, if you have not blown up the boat.

 

The world’s first turbocharger

 

Alfred Büchi is not a name that springs quickly into most people’s minds when thinking about boats or engines (probably not even a question on “Jeopardy). However, aside from Gottlieb Daimler or Rudolf Diesel, he was probably the most significant person involved in the development of the modern diesel engine. Alfred Büchi invented the world’s first turbocharger. This invention directly led to diesel engines becoming lighter, more powerful, and more efficient.

A Swiss engineer employed by Sulzer, Büchi developed the first principles of turbocharging diesel engines, or forcing air under pressure using exhaust gas heat into a combustion chamber. The year was 1905, and the first turbocharged engines were intended for use on early aircraft, since aircraft are subject to lower air pressure at high altitudes, thus suffering poor performance with natural aspiration. Turbocharged marine engines would not be developed until 1923. Automotive use of turbochargers would come much later, beginning with truck engines in the late 1930’s.

The principles developed by Alfred Büchi are still used in engine design in the present day, changing very little. The designs of the turbochargers may have changed (like in the development of VGT), but the physics and idea remain constant. Indeed, the biggest delay in turbocharger development was not the idea, but rather the lack of light, heat resistant materials available in 1905 when Büchi first conceived the idea.

 

 

1,768,000 Kilograms

 

 

1,768,000 Kilograms.

That weight is the equivalent of:

  1. 3 times the weight of Christ the Redeemer, the famous statue in Rio de Janeiro.
  2. 1/5 the weight of the Eiffel Tower.
  3. 11.5 times the weight of the average single family home.
  4. 17 times the weight of an adult blue whale.
  5. The weight of the CO2 produced by a MarineDiesel VGT350 engine over the course of its’ lifespan.

There is a lot of discussion in the media regarding CO2 as a greenhouse gas. CO2 is a product of the combustion process, and as such, is one of the emissions that cause environmental concern. Unfortunately, CO2 is extremely difficult to prevent or eliminate from emissions.

Why?

Diesel fuel is roughly comprised of 82.6% carbon. Since combustion requires air, oxygen is forced into the combustion chamber of the cylinder and it combines with carbon to form CO2.

CO2 is not regulated in the same manner as other emissions. Where required, carbon trading or other taxation schemes are used. However, this does not give engine makers a “free pass” regarding CO2. Efficiencies in turbocharging, electronic engine controls, and fuel efficiency also play a part in reducing carbon emissions. Scrubbing systems are becoming more compact and less expensive, and it will be several more years before the technology is applicable to smaller engines, but change will happen.

Given the fuel economy of Marinediesel’s VGT Series of engines, consumers are making a smaller carbon footprint by choosing the most efficient engine available in its’ class.

 

 

 

Maintenance Tip of the Week – Exhaust Temperatures 11/03/2014

 

Maintenance Tip of the Week

Pay close attention to exhaust temperatures. Never ignore system alarms or faults. Exhaust temperature is a primary indicator of cooling or combustion problems and incorrect temperatures indicate that immediate attention is required.

 

 

Turbo. The most misunderstood word?

 

 

The English language is continually evolving. Words change in meaning all of the time, either through common use, or by analogy. “Turbo” is one such word that has evolved in common use that is often misapplied.

Nowadays, the term Turbo is often used in marketing to denote something powerful, or fast. Any glance at a television or magazine will see things like advertisements or reviews for products like “turbocharged energy bars” or something with “turbocharged power”.

The first turbochargers were developed in the late 19th century as a way to use a turbine compress air into the combustion chamber of early internal combustion engines. Naturally aspirated engines rely on nature to provide enough air into the fuel / air mixture for combustion to occur. A turbocharger simply forces more air into the chamber, increasing the efficiency of combustion. This efficiency may or may not be expressed in terms of raw horsepower.  Efficiency could mean similar power output at a lower weight, or requiring less fuel. Modern turbochargers serve exactly the same function. It is the degree of compression, or the control of that compression, that differentiates between turbocharger brands and types. That is why the term “turbo” is so easily the product of marketing spin: The meaning can be twisted into just about anything that you are trying to sell.

All MarineDiesel engines are turbocharged to one degree or another. Indeed, our VGT Series of engines takes its’ name from the turbochargers with which it is equipped. Variable Geometry Turbocharger.

So, why do we use a VGT instead of a standard turbocharger?

The answer is simple: By controlling the aperture of the air inlet, we can control the degree of compression and the combustion process.

This is what gives our VGT engines a competitive edge over competing products in the market. It is what allows us to easily customize engine performance for our customers.

So, with MarineDiesel engines, we use the word “Turbo” as a descriptive term, rather than marketing spin.

 

 

 

Characteristics of Different Fuels

 

 

Different fuels have inherently different combustion characteristics (They burn in different ways and hold different amounts of energy). When considering alternative fuels, it is important to keep these characteristics in mind, over and above merely considering cost of fuel and cost of operation. The chart below demonstrates different fuels and gives an easy “at a glance” comparison between fuel types:

fuel characteristics

 

Comparison of Auto-Ignition Temperature

The auto-ignition temperature is the temperature at which fuel will ignite without a flame or spark. In respect to the auto-ignition temperatures, LPG, CNG, and LNG are safer than gasoline or diesel.because the auto-ignition temperature is much higher.

Comparison of Peak Flame Temperature

The flammability range is the difference between the leanest (LEL) to the richest (UEL) mixture of fuel and air that will burn. Fuel with narrower ranges are safer to work with, but are less versatile because they offer less choice of air / fuel ratios. CNG has a peak flame temperature of 1,790 deg C / 3,245 deg F, which is 187 deg C / 337 deg F cooler than peak flame temperature of gasoline at 1,977 deg C / 3,591 deg F. The peak flame temperature of LPG at 1,991 deg C / 3,614 deg F is only 13 deg C / 23 deg F (Less than 1%) higher than gasoline.

Comparison of Energy Content

Energy content per unit of fuel (energy density) is an important factor affecting range and power output of internal combustion engines. The higher the energy content of the fuel, the more power the engine will make.

Volumetric Efficiency

The amount of air entering an engine at a particular throttle angle and load is fixed. Any fuel added to the air before it enters the cylinder will displace an equal volume of air and will reduce the volumetric efficiency and power output of the engine. Reductions are as follows:

  • Diesel – Less than 1% (approx.)
  • Gasoline – 1-2% (approx.)
  • LPG – 4% (approx.)
  • CNG – 9% (approx.)

What is LPG?

LPG is “Liquefied Petroleum Gas” Commonly known as propane C3H8, a combustible hydrocarbon based fuel. It comes from the refining of crude oil and natural gas. At normal pressure and temperatures, propane remains in its’ gaseous form. At lower temperatures and / or  higher pressures, propane becomes a liquid.

Propane is odorless and colorless. For safety reasons, propane is required to be odorized. There are currently three grades of propane available: HD5 for internal combustion engines, commercial propane, and propane / butane mixture for other uses. The exact composition of propane varies slightly between different parts of the world and different refineries. Compared to gasoline, the energy content of LPG is 74%.

What is CNG?

CNG is “Compressed Natural Gas”. Natural gas (CH4) is a naturally occurring mixture of combustible hydrocarbon gases found in porous formations beneath the earth’s surface. Natural gas is created by the decomposition of plant and animal remains, under great heat and pressure, over very long periods of time.

Natural gas can be found as:

  • Non-associated gas: Free gas not in contact with significant amounts of crude oil in the reservoir.
  • Associated gas: Free gas in contact with crude oil in the reservoir.
  • Dissolved gas: Gas in solution with crude oil in the reservoir.

For safety reasons, CNG is required to be odorized. Compared to gasoline, the energy content of CNG is 25%.