Technologies

Clean Technology : Transportation

Technologies

Fuel Reactivity Method Cuts Diesel Engine Emissions

UW–Madison researchers have developed a smarter combustion process using in-cylinder fuel blending. The process is called Reactivity Controlled Compression Ignition (RCCI) combustion.

RCCI utilizes at least two fuels of different reactivity and multiple injections to control the timing and duration of combustion. In the process, a low reactivity fuel (e.g., gasoline) is introduced into the cylinder and mixed with air. Then, high reactivity fuel (e.g., diesel) is injected using single or multiple injections. This helps tailor the combustion process for optimal power output at a controlled temperature (to address NOx) and with controlled equivalence ratios (to address soot).
P100054US02

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

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.
P110320US01

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

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.
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RCCI – A Clean Compression Engine Combustion Process for High Fuel Efficiency and Low Emissions

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.
P100054US01

Internal Combustion Engine Exhaust Filtration Analyzer

UW-Madison researchers have developed an improved method and system for analyzing the performance of filtering materials used in DPFs and other exhaust filtration devices.  The new method is able to replicate actual in-use processes that occur during filling and regeneration of filtration devices.  The ability to accurately replicate realistic conditions and manipulate key system parameters sets the new method apart from previous techniques and allows for more accurate and complete analyses of exhaust filtration materials.

Control of the various operational parameters is provided by variable exhaust flow restriction with an actuating valve and orifice in the exhaust system.  In a diesel engine, the exhaust back pressure can be modulated to control the flow characteristics of the exhaust with an actuating value through feedback from a differential pressure sensor placed across the filtering material.  A mass flow controlled orifice may be incorporated downstream of the exhaust analyzer to control the filtration velocity independent of engine operating conditions.  The orifice also allows control of total downstream flow rate while diluting the sampled exhaust with a constant flow of air and provides a constant volume ratio of exhaust and air.  Both improve the evaluation of filter performance by reducing the number of dynamically changing parameters.  The exhaust also may be cooled in stages to control temperature-related characteristics of the exhaust, increasing the accuracy of results.

The implementation of exhaust filtration devices will continue to grow with increasing government regulation of emissions from mobile and stationary internal combustion engines.  As these regulations become more stringent and encompassing, exhaust filtration analysis will be an increasingly important tool in the filtration material development and certification of DPFs and other exhaust filtration devices.
P08173US

Non-Intrusive Monitoring of Combustion Chambers

A UW–Madison researcher has developed an improved monitoring system for engine combustion chambers that is less expensive and requires fewer components than currently available systems. Rather than using sensors located within the combustion chambers, this monitoring system makes use of a valve that allows air and fuel to enter and exit the chamber. When the piston compresses the air/gas mixture, the valve seals the chamber to contain it for the combustion process. The high pressure exerted by the piston compression causes the valve head to bend slightly, displacing the valve stem. Because the stem extends out of the chamber, displacements as small as 1/1000 of an inch can be measured by a sensor located on the outside of the chamber. To calculate pressure, the displacement is compared to a plot of valve movement versus cylinder pressure. Then a control system uses that information to adjust engine operation.
P08225US

Adaptive Fuel Injection Method Cuts Diesel Engine Emissions

UW–Madison researchers have developed a new adaptive injection technique to reduce NOx and soot emissions from diesel engines.

For low engine loads, one or more fuel injections take place between the intake and compression strokes. Each injection has increasing pressure, making the fuel highly premixed with air in the combustion chamber.

For greater engine loads, the process has two steps. First, injections of increasing pressure take place between the intake and compression strokes. Then, subsequent injections occur between the compression and expansion strokes. These subsequent injections have variable pressure. Such variation in injection pressure helps the fuel penetrate within the combustion chamber. At the same time, the pressure is modified so that fuel does not impinge on the walls of the chamber, which would worsen fuel economy and emissions. The technology can readily be implemented using an engine equipped with two fuel injectors per cylinder (each operated with different injection pressures), or with a single injector featuring variable injection pressure, as described in WARF reference number P01108US.
P07342US

Valve Method Cuts Engine Emissions, Boosts Combustion

UW–Madison researchers have developed a way to exploit the flexibility of VVA and reduce pollutant emissions from internal combustion engines.

Their method employs VVA to open valves not only during the intake and exhaust strokes (as in conventional engines), but also at optimal times during the compression and/or power stokes. Briefly opening the valves at these times promotes turbulence and more fuel-air mixing in the combustion chamber, resulting in much greater soot oxidation.

Any unburned fuel or particulates that escape through open valves via the intake manifold will be ingested during the next engine cycle and thus won’t contribute to emissions. Also, to reduce the loss of combustion chamber pressure (and thus engine power) while the valves are open, the length of time they are open can be minimized easily with VVA.
P06042US

Control System for Internal Combustion Engines

UW-Madison researchers have developed an engine control system that models and evaluates engine states in real-time, providing more precise control over performance, especially in engines with variable valve actuation. Key to the technology is a computationally efficient thermodynamic model of a cylinder, or “virtual cylinder,” which is implemented as part of the engine’s computer system. This model estimates the mass air per cylinder (MAC) for each actual cylinder at least a fraction of an engine cycle ahead of real-time operation (generally, 0.1 to 4 cycles ahead). This, in turn, allows real-time adjustments to fuel injection and other parameters, like spark advance, offering more precise engine control. Because the virtual cylinder model estimates MAC at the cylinder itself, these estimates may be more accurate than those achieved with traditional techniques that predict MAC at the throttle. The model also accounts directly for cylinder gas dynamics, rather than indirectly through volumetric efficiency (VE) corrections and other similar techniques. Moreover, because it models cylinders individually, the virtual cylinder approach allows the each cylinder’s fuel injection and spark to be set in accordance with its own MAC estimate, rather than an average MAC value for all cylinders.
P05046US

Plasma Treatment within Dielectric Fluids

UW–Madison researchers have developed a method for producing a plasma discharge in liquids at low temperatures and atmospheric pressure. It shows particular promise for treating gasoline and other liquid fuels to increase combustion efficiency.

In the method, bubbles of gas or vapor are first created within a liquid through mechanical, chemical or other means. Next, the liquid is subjected to an electric field that generates micro-discharges, and thus a plasma state, within the bubbles. Unlike previous techniques aimed at treating liquids by dielectric barrier discharge (DBD) plasma processes, this method produces a very large plasma/liquid interface per unit volume of liquid. This feature is needed to treat the entire liquid volume without causing heating or other unwanted effects.

Using this process, the researchers have shown that octane can be broken down into lower molecular weight compounds of higher burning efficiency. Thus, this technology could potentially be used for in-line treating of gasoline and diesel fuels prior to fuel injection, to increase combustion efficiency and possibly reduce emissions.
P03049US

Variable Valve Actuation Method to Enhance Combustion and Reduce Engine Emissions

UW-Madison researchers have now devised a way to exploit the flexibility of VVA to reduce pollutant emissions from internal combustion engines. Their method employs VVA to open valves not only during the intake and exhaust strokes as in conventional engines, but also at optimal times during the compression and/or power stokes. Opening the valves at these times promotes in-chamber turbulence and mixing during combustion, resulting in much greater soot oxidation. Any unburned fuel or particulates that escape through open valves via the intake manifold will be ingested during the next engine cycle and thus won’t contribute to emissions. Also, to reduce loss of combustion chamber pressure (and thus, engine power) during valve opening, the length of time the valves are open can be minimized easily with VVA.
P03152US

Reducing Emissions and Controlling Combustion Phasing in HCCI Engines

UW-Madison researchers have now developed a method to effectively control combustion phasing in direct-injection, compression-ignition engines by using suitably timed multiple fuel injections. In this technique, an initial fuel pulse is injected during the early phase of the compression stroke. The pulse is timed to mix with cylinder air so that it is too “lean” to produce appreciable soot and nitrogen oxides upon combustion, but not so lean that it creates significant amounts of unburned hydrocarbons and carbon monoxide.

Normally, the pulse is also too lean to auto-ignite, leading to problems with combustion phasing. To solve this, the researchers inject a second fuel pulse that provides a locally rich fuel mixture for effective auto-ignition. They have optimized the second injection’s timing and amount to reduce the soot and nitrogen oxides normally resulting from a single, late fuel injection.
P01320US

Use of Multiple Injections of Increasing Pressure to Reduce Diesel Engine Emissions

UW-Madison researchers have developed a multiple fuel injection scheme that should simultaneously reduce both nitrogen oxide and particulate emissions from diesel engines. Instead of injecting a single fuel charge during a combustion cycle, several charges are injected. Each charge carries an amount of fuel that when added together equals the single charge and is injected at a higher pressure than the last. Spacing fuel injections into several charges of increasing pressure enlarges the surface area of the soot clouds that are exposed to oxidation. It also maintains more uniform combustion temperatures, leading to cooler engine conditions and lower nitrogen oxide emissions. This technique provides higher combustion chamber mixing and greater soot oxidation rates even during the power stroke when mixing rates are reduced due to piston expansion.
P01108US