Compression Engines portfolio

P100054: Engine Combustion Control Via Fuel Reactivity Stratification

Overview: Diesel compression ignition engines offer higher efficiency and lower CO2 emissions than their gasoline spark ignition counterparts; however, controlling NOx and soot emissions while achieving high efficiency is a challenge. Conventional diesel engines are prone to high production of nitrogen oxides (NOx), which result in adverse environmental effects such as smog and acid rain and particulates or “soot,” which is visible as the black smoke emitted by some diesel vehicles as they accelerate from a stop. As a result, the United States and many other countries have imposed stringent emission regulations on the use of diesel engines in vehicles.

Numerous technologies have been developed to address the need for diesel engines with reduced emissions. Unfortunately, measures which reduce NOx production in an engine typically increase soot production, and measures that reduce soot production commonly increase NOx production. This conundrum is often termed the “soot-NOx tradeoff.” An alternate approach is to install “after-treatment” systems that address soot and NOx after leaving the engine, but these methods tend to be expensive to install and maintain and can reduce the vehicle’s fuel efficiency. Current technologies developed to reduce both NOx and soot generation are difficult to implement and control and many still require expensive after-treatment measures. As a result, a significant need is felt for engines that provide the efficiency of a diesel engine while meeting or exceeding current emissions standards.

The Invention: UW–Madison researchers have developed a compression engine combustion process using in-cylinder fuel blending. The system utilizes at least two fuels of different reactivity and multiple injections to control in-cylinder fuel reactivity to optimize combustion phasing, duration and magnitude. The process involves introduction of a low reactivity fuel into the cylinder to create a well-mixed charge of low reactivity fuel, air and recirculated exhaust gases. The high reactivity fuel is injected using single or multiple injections directly into the combustion chamber.

In this combustion process, the combusting phasing and duration are controlled by the auto-ignition characteristics, or reactivity of the charge; thus, the combustion mode was named Reactivity Controlled Compression Ignition (RCCI) combustion. Figure 1 shows a typical setup for RCCI combustion using port-fuel-injection of a low reactivity fuel (e.g., gasoline) and direct-injection of a high reactivity fuel (e.g., diesel fuel).

By appropriately choosing the reactivities of the fuel charges, their relative amounts, timing and combustion can be tailored to achieve maximum fuel efficiency. This methodology has resulted in what is believed to be the most fuel-efficient internal combustion engine currently known that is also capable of meeting government soot and NOx emissions limits (see related publication below). Figure 2 shows a summary of results at identical operating conditions for an engine operating in the RCCI combustion mode and state-of-the-art conventional diesel combustion mode. In addition to the improved efficiency, (i.e., reduced greenhouse gas emissions) due to reduced heat transfer losses and improved control over the combustion event, RCCI combustion has demonstrated a factor of 100 reduction in NOx emissions and a factor of 10 reduction in soot emissions.

Applications:

• Reduction of emissions of diesel engines to meet mandated EPA emissions regulations
• Improved fuel efficiency for low emission semi-trucks and off-highway vehicles
• Compatible with Exhaust Gas Recirculation and exhaust after-treatment methods to further reduce emissions

Key Benefits:

• Lowers NOx and soot emissions
• Reduces heat transfer losses
• Increases fuel efficiency
• Eliminates need for costly after-treatment systems
• Reduces fuel system cost
• Complies with EPA 2010 emissions guidelines without exhaust after treatment

P110092: Engine Combustion Control at Low Loads with Reactivity Controlled Compression Ignition Combustion

Overview: Diesel engines, also known as compression ignition engines, are among the most energy-efficient engines available, with high power output per fuel consumption. Unfortunately, they are also among the “dirtiest” engines available with high production of soot and nitrogen oxides, which result in adverse effects such as smog and acid rain. The United States and many other countries have imposed emissions regulations on the use of diesel engines in vehicles, and numerous technologies have been developed to address the issue of high diesel emissions. The difficulties in complying with emissions regulations has resulted in many automotive companies shifting focus away from diesel engines to the use of gasoline engines, which have lower energy efficiency as well as concerning levels of emissions, albeit lower levels than diesel engines.

UW–Madison researchers have previously developed Reactivity-Controlled Compression Ignition (RCCI) methods, which adapt the fuel provided to the engine’s combustion chamber to vary reactivity over the course of the combustion cycle and provide a stratified distribution of fuel reactivity. Fuel reactivity can be tailored by using both diesel fuel (higher reactivity) and gasoline (lower reactivity), timed to be injected at different times during the compression stroke. Appropriate tailoring of fuel reactivity, fuel amounts and proportions and the timing of fuel introduction into the combustion chamber allows combustion to be tailored to produce peak work output at the desired time with low nitrogen oxide and soot production. However, experimentation has revealed that with decreasing engine load and particularly at idle, RCCI methods do not function as well. At low loads, the engine effectively operates as a conventional diesel engine with minimal or no use of gasoline, resulting in conventional diesel performance with lower thermal efficiency and higher emissions. A need exists for adaptations to the RCCI method to allow low-load operations while using the fuel reactivity stratification strategy to achieve low emissions.

The Invention: UW–Madison researchers now have developed a compression combustion method for an internal combustion engine to enable low emissions and high thermal efficiency at low engine loads. The combustion engine has tanks containing fuel materials with differing reactivities. Fuel from the tanks is provided to the combustion chamber during an engine combustion cycle when the engine is running to obtain a stratified distribution of fuel reactivity within the combustion chamber, with regions of high reactivity spaced from regions of low reactivity. The fuels are provided to the combustion chamber at different times during the engine combustion cycle.

The internal combustion engine also has a throttle upstream from its intake port, which allows an open state allowing maximum airflow from the intake manifold to the intake port and a closed state allowing minimum airflow from the intake manifold to the intake port. The throttle is kept out of the open state during the intake stroke of the combustion cycle so that the cylinder air pressure is below ambient pressure at the start of the compression stroke, resulting in controlled temperatures, equivalence ratios, soot and emissions and increased fuel efficiency.

Applications:

• Internal combustion engines utilizing reactivity-controlled compression ignition combustion (RCCI)

Key Benefits:

• Maintains low emissions and low fuel consumption across a range of engine loads, including low loads and idling
• Allows RCCI to be combined with exhaust gas recirculation, exhaust after-treatment strategies and other combustion manipulation techniques to further reduce emissions

P110320: Improved Compression Ignition Combustion in Rotary Engines for Higher Efficiency and Lower Pollutant Emissions

Overview: UW–Madison researchers previously disclosed a Reactivity Controlled Compression Ignition (RCCI) system for improving fuel efficiency and lowering emissions in compression ignition, internal combustion engines. The technology uses a mixture of fuels with different reactivities to control a more efficient combustion process within the engine’s cylinders.

Most automobiles use reciprocating engines (i.e., piston based), however, rotary engines are of interest because they are relatively compact and lightweight compared to reciprocating-piston engines having similar output. A rotary engine is a type of internal combustion engine in which a rotor rotates within a housing and one or more combustion chambers are formed between the rotor and housing. Although rotary engines have many advantages, they also have poor fuel efficiency and high levels of pollutant emissions, which have prevented their widespread adoption. Improving diesel engine efficiency also has been an area of interest because diesel engines tend to be more efficient than gasoline engines and provide higher power output per fuel consumption, but again disadvantages are seen in terms of high pollutant emissions. An improved engine that maximizes efficiency and minimizes pollutant emissions is needed.

The Invention: The UW–Madison researchers now have adapted their previous RCCI method for use in rotary engines. The system comprises a rotor with a circumference having two or more rotor faces where a chamber is defined between each rotor face and the housing. A similar fuel mixture method is used in which a first fuel charge is provided to one of the chambers and then a second fuel charge with different reactivity is provided to a different location in the chamber containing the first fuel charge so as to set up an optimal reactivity stratification. The chamber receiving the first and second fuel charges lacks a spark plug or other spark source; thus, the fuel charge having higher reactivity initiates combustion within the chamber.

Applications:

• Rotary engines for cars, motorcycles, planes, personal watercrafts, power generators and small engines used in products such as lawnmowers and chainsaws
• Hybrid and compact vehicles

Key Benefits:

• Enhanced efficiency
• Reduced emissions
• Can be implemented in a lightweight and compact rotary engine
• Significant reduction in combustion temperatures
• Low unburned fuel
• Low NOx and particulate (soot) emissions

Included IP

• P100054US01 (PAT)
• P100054US02 (CON)
• P100054US03 (CON)
• P110092US01 (PAT)
• P110092US02 (CON)
• P110320US01 (PAT)

*International rights are available. If interested, please contact cschmit@warf.org.