VENTURI INDUCTION FOR HEAT RECOVERY AND LOW NOX INTERNAL COMBUSTION ENGINES
Internal combustion engine heat is recovered by charge air for useful work and to increase engine thermal efficiency. A dual liquid/air cooling system is presented to facilitate heat recovery. Water is injected into a pintle-regulated Venturi to mitigate the engine charge temperature, control the combustion temperature and reduce NOx emissions.
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This invention improves the thermodynamic efficiency while reducing NOx emission of internal combustion engines. A simplistic approach is to homogeneously mix water with fuel and air in a pintle-regulated Venturi to reduce the combustion temperature. A second approach is described to increase engine efficiency, whereby exhaust heat is recovered by incoming air and subsequently cooled by water injection in a Venturi. A third approach recovers heat from the combustion chamber and exhaust, increasing the heat recovery potential. Fuel could be gasoline but could also be natural gas, other hydrocarbons, alcohols, or diesel.
BACKGROUND OF THE INVENTIONIn a conventional internal combustion engine, coolant heat rejection ranges from 10-35% of the combustion energy. Exhaust heat loss is usually 20-45% of the combustion energy. Consequently, there is substantial room for improving the thermodynamic efficiency of the internal combustion engine.
Air is composed of 78 volume percent nitrogen. Nitrogen oxidizes when fuel is burned at high temperatures, as in a combustion process to form nitrogen oxides. Nitrogen oxides consist of a group of oxidized nitrogen compounds collectively known as NOx. Many of the nitrogen oxides are colorless and odorless. However, one common pollutant, nitrogen dioxide (NO2) along with particles in the air can often be seen as a reddish-brown layer over many urban areas. The primary source of NOx is motor vehicles. Production of NOx increases with the time and temperature of combustion.
NOx is generated exponentially with increasing flame temperature and decreases exponentially with water injection in the flame zone. NOx emissions can therefore be reduced by eliminating nitrogen from the intake vapor mixture and/or reducing the combustion temperature by saturating the intake vapor mixture with water.
Of the six pollutants (carbon monoxide, lead, nitrogen oxides, particulate matter, sulfur dioxide, and volatile organic compounds) tracked by the Environmental Protection Agency, all have decreased significantly since passage of the Clean Air Act in 1970—except for nitrogen oxides
The differential producing Venturi has a long history of uses in many applications. With no abrupt flow restrictions, the Venturi can mix gases and liquids with a minimal total pressure loss. Recently, the Venturi has been used in carbureted engines. The suction from the throat of the Venturi provided the motive force for bringing the fuel in contact with the air. The improved application of the Venturi with the proposed invention is: the metering of the fuel is controlled by the fuel injector instead of the suction of the venturi; the fuel vaporization is facilitated by the reduced pressure in the throat of the Venturi; and mixing of the fuel/vapor mixture is enhanced by the turbulent action in the outlet of the Venturi.
The principle behind the operation of the Venturi is the Bernoulli effect. The Venturi mixes vapors and liquids by reducing the cross sectional flow area in the vapor flow path, resulting in a pressure reduction in the throat of the Venturi. After the pressure reduction, the mixture is passed through a pressure recovery exit section where most of the pressure reduction is recovered. The pressure differential follows Bernoulli's Equation, simplified for a negligible change in elevation:
P1+½d1v12=P2+½d2v22
where,
P1=Pressure at the inlet of Venturi (
P2=Pressure at the throat of the Venturi (
d1=vapor density at the inlet of the Venturi (
d2=vapor density at the throat of the Venturi (
v1=vapor velocity at the inlet of the Venturi (
v2=vapor velocity at the throat of the Venturi (
In
Three methods are presented for reducing NOx in an internal combustion engine. Air is defined for the purposes of this disclosure as a vapor containing oxygen. Water is defined as liquid containing water, recognizing that anti-freeze components may be required for cold weather operation.
In the first method, water is injected into the throat of the Venturi where homogeneous mixing is accomplished with fuel and air. NOx emission is reduced because of the resulting lower combustion temperature due to water injection.
The second method utilizes engine exhaust to heat charge air. The heated air is cooled by water injected into a Venturi passing the heated air charge. The thermal efficiency of the engine is improved without overheating the engine because heat is absorbed by the injected water. Specifically, engine overheating is prevented by 1) the low water temperature relative to the air charge and 2) the latent heat of evaporation of the water in the Venturi. Exhaust heat is therefore recovered by the water liquid-to-vapor phase change between the point of injection and combustion outlet valve.
The third method recovers heat from the engine exhaust and the combustion chamber. Charge air, compressed by a supercharger or turbocharger is heated by the exhaust and the combustion chamber. Recognizing that the combustion chamber temperature must be regulated, a dual chamber is depicted whereby the inner liquid coolant is temperature controlled as in a conventional engine. However, heat is also conveyed to the outer chamber where combustion heat is transferred to charge air. Heat transfer to the outer air chamber can be facilitated by fins projecting through the inner and outer chamber partition.
The heated charge air is controlled by an ambient air-cooled inter-cooler to ensure the charge air never becomes overheated beyond the capability of the water injection to control the combustion temperature. Otherwise, the combustion temperature inside the cylinder could potentially become too hot for conventional engine materials. The control strategy will maximize heat recovery by water injection to optimize engine efficiency.
With the pintle-regulated Venturi design, the fuel becomes well mixed with the vapor because: 1) the pressure reduction at the Venturi throat increases the partial pressure of the fuel, promoting fuel vaporization and; 2) turbulence through the Venturi facilitates fuel/vapor mixing before the combustion chamber. The pintle-regulated Venturi design enhances fuel/vapor mixing at all throttle vapor rates by combining vapor flow control with the Venturi design. The resulting flow area reduction provides a higher velocity at low throttle than an unregulated Venturi design. For example, when a car is cruising down the highway at low throttle, the pintle is relatively closed into the throat of the Venturi. Consequently, mixing velocity is much higher and mixing is more complete across the entire throttle range relative to an unregulated Venturi or a common butterfly valve intake system.
The water injection rate for all three methods is controlled by the exhaust temperature sensor.
The thermal efficiency of the engine is improved by heat recovery from the combustion products to the charge air. NOx emissions are controlled and reduced by regulating the combustion temperature with water injection.
Claims
1. A double-wall exhaust pipe carrying exhaust inside a center pipe heats charge air flowing through an annulus, whereby heated charge air as stated in claim 5 is provided to a spark-ignition or compression ignition engine.
2. A double-wall pipe conveys heated charge air in the center channel and an evacuated annulus minimizes heat loss, whereby heated charge air as stated in claim 5 is provided to a spark ignition or compression ignition engine.
3. A dual medium coolant system comprised of an inner chamber for liquid cooling and an outer chamber for air cooling; the liquid-cooled chamber controls the engine temperature with a flow control thermostat; charge air is conveyed through the outer chamber to the engine for combustion; whereby heated charge air as stated in claim 5 is provided to a spark ignition or compression ignition engine.
4. A dual coolant chamber comprised of an inner chamber for liquid cooling and an outer chamber for air cooling, with fins spanning from the inner liquid-cooled chamber to the outer vapor-cooled chamber to increase heat transfer to the outer air-cooled heat transfer chamber; the liquid-cooled chamber controls the engine temperature with a flow control thermostat; charge air is conveyed through the outer chamber to the engine for combustion: whereby heated charge air as stated in claim 5 is provided to a spark ignition or compression ignition engine.
5. Heated charge air and water is injected into a pintle-regulated Venturi; whereby the engine combustion temperature is controlled by the water injection rate in a spark ignition or compression ignition engine.
Type: Application
Filed: Feb 28, 2005
Publication Date: Aug 31, 2006
Applicant: ASPEN ENGINEERING SERVICES, LLC (Morrison, CO)
Inventor: James Meyer (Morrison, CO)
Application Number: 10/906,624
International Classification: F01N 3/02 (20060101); F01N 5/02 (20060101);