While you may be aware of diesel engines, and diesel powered welders, many people have little hands-on experience with them.
Diesel engines have traditionally been much less popular than gasoline powered engines. A diesel fueled engine has many advantages over its gasoline powered relatives, not to mention typically higher fuel efficiencies than are possible with gasoline engines.
A diesel engine is an internal combustion engine that uses diesel as a fuel. Even though they’re also an internal combustion engine, they differ from gasoline engines in some very different ways. The first of these is that a diesel engine doesn’t have spark plugs, or combust fuel with the aid of a spark producing device. Diesel engines use pressurized fuel pumps to inject diesel fuel into the cylinders, and then compress the resulting air-fuel mixture to a very high pressure where it combusts due to the heat of compression.
To put a diesel engines operating pressure into perspective, typical gasoline powered internal combustion engine utilizes a compression ratio of roughly 8:1 to 12:1. Whereas a diesel engine has a compression ratio of anywhere from 14:1 to up to 25:1. As an example, let’s consider atmospheric pressure to be 14 psi and use compression ratios of 10:1 for a gasoline engine and 20:1 for a diesel engine. the gasoline engine will compress the mixture to 140 psi and the diesel engine will compress it to 280 psi — twice that of the gasoline engine. It’s because of the diesel engine’s higher compression/expansion ratio that more power is produced with less fuel. This reason alone is why diesel engines are more efficient than their gasoline powered counterparts.
With roughly twice the compression ratio, the difference in operating pressures within the engine cylinder is rather large. And because of this, diesel engines need to be built much stronger than gasoline engines. The upside to this is that the reliability of a heavier duty engine increases. Diesel engines require less maintenance and often will operate much longer before maintenance is needed. Add to that the fact that there are fewer moving parts, and it’s easy to see why they seem to run forever. The downside though is that a heavier duty engine is much more expensive to manufacture and in turn will cost you more to purchase.
Another byproduct of the increased operating pressure of the diesel engine is an increased torque output. Diesel engines produce a large amount of torque at a lower rpm level, and lend themselves well to industrial and construction duties where high torque is needed. This lends itself well to welders, especially when using higher amperage ranges for long periods of time such as when pipeline welding, or arc gouging.
While diesel engines are capable of utilizing kerosene as a fuel, due to kerosene’s higher cost, it’s not often used. Instead, kerosene is usually blended with diesel fuel in colder climates in order to keep the diesel fuel from “gelling” up. Colder temperatures cause waxy like solids to precipitate in pure diesel fuel. This is known as the cloud point, and if it gets too cloudy, the diesel fuel “gels” and causes fuel filters to plug up which in turn keeps the engine from operating. Normally this isn’t a problem in most colder areas because the fuel companies supply a winter diesel blend that’s been mixed with kerosene to eliminate this.
So as you can see, diesel engines can be a great way to power welders, especially if your requirements demand long hours of continuous use. For most hobby and light duty requirements, a gasoline powered welder is still the most economically prudent choice. But when your amperage output or operating hours increase, you may be better off with a diesel powered welder even though the initial costs are usually much larger.
There is much more that could be said about diesel engines, but it’s well beyond the scope of this blog post. If you’d like to learn more, this wiki page on diesel engines is a great place to start.
For a simple example of how a diesel engine works, watch the video below.