According to the National Research Council, diesel engines are only 42% efficient in converting the fuel’s chemical energy to mechanical work energy. For over a century, this loss of potential work has been explained as the result of inherent barriers in the transition from the heat of combustion to pressure on the piston.

The fundamental discovery made by developers of HMWPIB technology is that the physical properties of diesel fuel restrict how much of the fuel’s chemical energy that can be extracted during combustion. A large part of the 58% loss of potential energy is due to poor combustion efficiency. Incomplete combustion not only wastes fuel (increasing greenhouse gasses) it also produces the PM, ground level ozone, and NOx emissions responsible for death and disability across the globe.

The Role of Oxygen in Combustion Efficiency

Combustion requires three things: air, heat, and fuel. 100% combustion produces only heat, carbon dioxide, and water (CO₂ and H₂O). Anything less than 100% combustion produces heat, CO₂ and H₂O plus carbon monoxide (CO) unburned hydrocarbons (UHC), and particulate matter (PM). (NOx is also produced indirectly, as a result of rapid heat release.) Complete combustion, 100% efficiency, of a liquid hydrocarbon fuel occurs when all of the fuel's carbon is converted to CO₂ and all of its hydrogen is converted to H₂O. For complete combustion to occur, oxygen must be available at every potential site of combustion.

Effects of HMWPIB on Oxygen During Combustion

Diesel is a complex fuel comprised of many compounds, each with its own requirement for oxygen to support complete combustion. The combustion efficiency of a diesel engine is dependent on the degree of homogeneity both of the compounds in the fuel vapor and of the mixture of this vapor with air. Viscoelasticity increases uniformity of droplet size and vapor content in the air-fuel mixture. As a result, it makes more oxygen available at combustion sites throughout the air-fuel mixture. More air at combustion sites produces more complete combustion and, therefore, produces less toxic emissions.

Untreated fuel spray. Wide range of droplet size and distribution, aggregating towards the center of the spray cone with superfine droplets at perimeter.

HMWPIB-treated fuel spray. More uniform droplet formation and distribution, eliminating ultra-fast-burning superfine droplets. Results in a steadier, more complete burn with no NOx-creating rapid heat-release profile.

Untreated fuel vaporization. Light-end, fast-burning components (pink) vaporize first, concentrating the heavier, slower-burning components (blue). The result is products of incomplete combustion, primarily PM.

HMWPIB: Effect on Droplet Size and Distribution

In a diesel engine, fuel is sprayed from an injector, blended with air, and vaporized in the heat of the cylinder before it is burned. This is a physical process. How the fuel performs physically in each step during this transition determines how much of its energy is extracted in combustion.

In untreated liquid hydrocarbon fuel, uncontrolled droplet formation produces a hetergeneous mix ranging from superfine ultra-fast-burning to aggregated slower-burning. The superfines burn in a flash, leaving unburned hydrocarbons, particulate matter, and NOx (from rapid heat release early in cycle).

When subjected to shear, as in a diesel injector, a viscoelastic liquid experiences an instantaneous increase in viscosity to the point that it approaches the behavior of a solid. The effect on diesel fuel spray is to reduce average droplet size and distribute fuel more evenly across the spray cone. The fuel spray entrains more air. Droplets have better penetration of the high-pressure gas in the cylinder where they resist splatter and coating when they contact a surface. Superfine droplets that burn explosively like a vapor are eliminated.

HMWPIB: Effect on Vaporization and Vapor Composition

Viscoelasticity also modifies the process of liquid hydrocarbon fuel vaporization. Increased viscosity inhibits fractional distillation, allowing all of a fuel’s various compounds to vaporize simultaneously from the surface of the liquid.

The vapor formed is a more homogeneous blend of the fuel's different compounds. In a series of tests to measure the calorific value of gasoline, adding a few ppm of a HMWPIB increased calorific value by 7.9%. In this test protocol, liquid fuel is vaporized under ideal conditions to release the fuels energy.

HMWPIB increases the homogeneity of the air-fuel mixture at the molecular level. Diesel fuel’s different compounds are more evenly distributed in the fuel vapor and sufficient oxygen is made available at more combustion sites for conversion of the carbon and hydrogen to CO₂ and H₂O. Combustion efficiency and fuel economy are increased.