Patent Application
20200200105
The present invention relates to internal combustion engines and, more specifically, to systems and methods which reduce exhaust emissions without degrading other engine performance parameters such as fuel efficiency.
Environmental compliance in the transportation industry continues to be problematic for society. Control of emissions levels is particularly costly for the commercial ground transportation industry because Compression Ignition (CI) engines have a set of technical challenges different from Spark Ignition (SI) engines. Present and future emissions compliance demand systems advancements in diesel engine technology. Solutions increase vehicle costs and elevate maintenance costs. Another undesirable outcome which stems from compliance with NOx emissions standards relates to the further generation of greenhouse gases, as reductions in fuel efficiency have been accepted as a necessary cost of compliance with NOx emissions standards.
Ideally, optimum fuel efficiency in a diesel or gasoline powered internal combustion engine requires adjustment to a relatively high air-to-fuel ratio such that the ratio is positioned away from a relatively rich fuel content to a slightly fuel rich ratio that is relatively close to the stoichiometric ratio.
Despite this drawback, it is widely accepted that control of NOx emissions in diesel engines must be addressed with some form of an Exhaust Gas Recirculation (EGR) system which re-uses spent combustion gases. Typically, EGR systems recirculate gases from the exhaust manifold through the intake manifold. The extent of recirculation may range from 10 percent to over 50 percent. This affects reduction in the oxygen content at the intake manifold, effectively depressing the air-to-fuel ratio. With relatively rich fuel content in the combustion chamber, the reaction is shifted further away from the stoichiometric ratio. This, in turn, reduces the combustion temperature to a level which reduces NOx generation to a more acceptable level, perhaps up to about a fifty percent reduction. However, as the level of exhaust recirculation increases, there is increased heat rejection which requires a larger cooling system. Another drawback is that with exhaust gas recirculation diluting the volume percent of oxygen entering the engine from the intake manifold, the engine power density decreases. This gives rise to a need for a larger displacement engine to achieve the same power output. Also, when the volume percent of oxygen decreases, more soot is generated and more unburned hydrocarbons are also carried out the exhaust. With regulatory limits on both particulate matter and unburned hydrocarbons it has become necessary to incorporate additional equipment in the engine exhaust system, e.g., diesel particulate filters which may remove only about eighty five percent of the particulate matter. Generally, EGR systems require additional components to overcome or offset the aforementioned drawbacks. They result in excessive engine wear and higher maintenance requirements due, for example, to entry of carbon into the motor oil.
It is also recognized that an EGR system cannot, alone, provide sufficient NOx emission reductions to comply with many current and future emissions requirements. Due to the aforementioned drawbacks of EGR systems in diesel engines, original equipment manufacturers have incorporated systems with other means to reduce NOx emissions and to even reduce the percentage of exhaust gas recirculation. Selective Catalytic Reduction (SCR) systems are exemplary. Such systems inject an aqueous solution of urea into the exhaust flow in the presence of a catalyst to convert the NOx into molecular nitrogen and water. Treatment of exhaust gases by catalytic reduction after initial NOx removal with an EGR system enables engine operations to meet current regulatory requirements; and while it is essential to incorporate exhaust gas recirculation in diesel engines to meet emission level standards, the necessary level of recirculation can be reduced with an SCR system. Ideally, alternate means for reducing the NOx emissions should completely supplant the need for EGR systems.
The simplified schematic diagram of
The secondary exhaust emissions control system includes electronic controller 51, a Diesel Particulate Filter 53 and a Selective Catalytic Reducer 55, each in line with the exhaust pipe 43. Upstream of the Filter 53 there are positioned in the exhaust pipe 43 an exhaust temperature sensor 57 and a NOx sensor 59 which each provide a signal 57s or 59s only to the controller 51. An intermediate temperature sensor 61 is positioned in the exhaust pipe between the filter 53 and the Selective Catalytic Reducer 55. An output NOx sensor 63 positioned in the exhaust pipe 5 measures the NOx level in exhaust leaving the pipe 43. The intermediate temperature sensor 61 and the NOx sensor 63 each provide a signal 61s or 63s only to the controller 51.
The engine control system comprises an Electronic Control Unit (ECU) 71 which is connected to receive signals from each of an intake manifold pressure sensor 75, an exhaust pressure sensor 77, a fuel rail pressure sensor 79, a barometric pressure sensor 81 and a crank shaft position sensor 83. The ECU also sends a control signal 87 to the EGR valve 49 to regulate the amount of exhaust flow recirculated into the manifold 19 and a control signal 89 to regulate the timing and duration of the opening of the fuel injector 35.
The following drawings are provided to facilitate understanding of the inventive concepts described in the written description which follows, where:
Like reference numbers are used throughout the figures to denote like components. Numerous components are illustrated schematically, it being understood that various details, connections and components of an apparent nature are not shown in order to emphasize features of the invention. Various features shown in the figures are not shown to scale in order to emphasize features of the invention.
Before describing in detail the particular methods and systems and components relating to embodiments of the invention, it is noted that the present invention resides primarily in a novel and non-obvious combination of components and process steps. So as not to obscure the disclosure with details that will be readily apparent to those skilled in the art, certain conventional components and steps have been omitted or presented with lesser detail, while the drawings and the specification describe in greater detail other elements and steps pertinent to understanding the invention. Further, the following embodiments do not define limits as to structure or method according to the invention, but provide examples which include features that are permissive rather than mandatory and illustrative rather than exhaustive.
With reference to
Hydrogen generation systems suitable for practicing the invention are designed to produce hydrogen-containing gaseous products suitable for injection into an engine combustion chamber because they contain reactive hydrogen. The term hydrogen containing gaseous products as used herein and in the claims means products which contain reactive hydrogen, i.e., containing atomic hydrogen (H) or molecular hydrogen (H2) or hydrogen in the form H+, OH−, O−H+ or H2O2 suitable for use in an internal combustion engine to facilitate enhanced performance when also burning another fuel. The hydrogen containing gaseous products may contain other components such as H2O. When the gaseous product is generated by electrolysis the product includes oxygen where the ratio of hydrogen to oxygen is 2:1 and the material is referred to as oxyhydrogen, HHO or Brown's gas. Although disclosed embodiments of the invention include hydrogen generation systems which produce a reactive hydrogen species, the hydrogen-containing gaseous products include pre-prepared secondary fuel containing reactive hydrogen. Also, a hydrogen generation system may produce reactive hydrogen in situ in the presence of heat and a catalytic material such as copper. For example, a light hydrocarbon such as methane may be passed through a variable number of heated copper tubes to provide a supply of reactive hydrogen. The process may involve generation of a plasma or thermal cracking or a uv photoelectric process.
A function of the control module 104 is to modify the behavior of one or more original equipment control circuits of a vehicle by adjusting the signals normally sent directly from sensors into the ECU 71. By way of example, in the embodiment of
Embodiments of the invention are in recognition that, because an ECU modifies certain engine variables in response to changes in sensor data (e.g., pulse widths of fuel injection timing signals), the same input terminals of an ECU utilizing this sensor data can be used to further change engine parameters, e.g., in a cumulative manner, based on information provided to the terminal in addition to or in place of the data received directly from the sensor. Thus received sensor signal data can be modified based on additional information in order to further alter those engine variables of interest in response to changing conditions such as a change in the air-to-fuel ratio resulting from a change in the rate of flow of a secondary fuel into the intake manifold of the engine.
With reference to
To effect this modification of any sensor signal input to the ECU 71, the control module 104 may be microprocessor based and programmed in accord with an algorithm or may access values from a look-up table. More simply, the control module may apply one or more predefined offset values to adjust the sensor magnitude as a digital signal or as an analog signal. In the illustrated embodiments this control module functionality is implemented with a microprocessor. It is to be understood that in embodiments which integrate functions of the control module 104 with the OEM ECU, separate analog-to-digital and digital-to-analog conversions may not be necessary.
In embodiments of the invention, the control module may include an algorithm, a look-up table or, more simply, one or more predefined offset values, which are applied to adjust the volumetric flow of the primary fuel to improve engine performance while a secondary fuel is sent into the combustion chamber regions. The magnitude of voltage adjustment made by the control module 104 may simply be a fixed value based on analysis of engine performance under differing rates of primary fuel delivery (e.g., diesel fuel delivery) and manifold pressure while both the primary and the secondary fuel are applied. Other embodiments include variable voltage shifts for the sensor value to more optimally adjust the rate of fuel delivery, e.g., based on varying engine dynamics or changes in ambient conditions. The secondary fuel may be held at a fixed flow rate while the analysis is performed by varying primary fuel input rates or an algorithm may provide adjustment based in part on varied flow rate of the secondary fuel.
Before describing specific features of the CI engine system 100 shown in
The control circuitry of
As illustrated in
Referring again to
Digitized sensor signals output from the thermocouple circuitry 126 and the analog-to-digital converter circuitry 128 are transmitted on the serial bus 124 to the microprocessor 132 which determines changes in HHO production levels (e.g., based on weighted sensor data). The microprocessor 132 also modifies the magnitudes of several sensor signals: the pressure signal 75s from the intake manifold pressure sensor 75, the pressure signal 77s from the exhaust pressure sensor 77, the fuel rail pressure signal 79s from the sensor 79, and the barometric pressure signal 81s from the sensor 81. The revised signal magnitudes are sent to the digital-to-analog circuitry 130 over the bus 124 and are then output to the ECU 71 to perform functions, including modification of the air-to-primary (diesel) fuel ratio and control of dependent variables such as NOx emissions.
In one embodiment the control of variables is had through the process of continually monitoring data acquired with sensors while adjusting independent variables. In one application the rate of primary fuel delivery, an independent variable, is adjusted while comparing values of a dependent variable to effectively modify the rate of primary fuel delivery until the difference between the predetermined value and the measured value of the dependent variable approaches zero or a minimum. Similarly, the rate of delivery of secondary fuel, also an independent variable, is adjusted while comparing values of a dependent variable (e.g., the level of NOx emissions) to effectively adjust the magnitude of the dependent variable. To this end, the sensor output may be routed through the control module 104, digitized and compared to a predetermined value. Based on the difference between the sensor voltage output and the predetermined value, an algorithm or a matrix of values is used to determine an adjustment to the independent variable. Thus under conditions where the engine power is increased increasing the flow rate of a primary fuel into the engine, control circuitry may adjust the rate of delivery of the secondary fuel as the rate of primary fuel delivery changes.
The hydrogen generation system includes a hydrogen generator 114 and hydrogen control electronics 118 shown in
The hydrogen control electronics 118 includes a CPU 142 which controls HHO production and safety control, and MOSFETs 144 that regulate the rate of hydrogen production, including regulation of electrolytic cells that produce the HHO, and regulation of the electrolyte pump, electrolyte heaters and cooling fans. The electronics monitors temperature to provide data for cooling and to assure safe limits of operation. The CPU also controls circuitry 148 which includes safety interlock switches and electrolyte level monitors. Signals 112s from the NOx sensor 112 are received via a CAN BUS into the CPU 142 and transferred to the microprocessor 132 in the NOx control module 104 via the RS232 serial link 140. The microprocessor 132 monitors the NOx signal as part of the control function which minimizes emissions as a function of shifts in magnitudes of the independent variable signals to 75s′, 77s′, 79s′ and 81s′ which are sent to the ECU 71 in lieu of signals 75s, 77s, 79s and 81s.
With further reference to
While it has been a desire in the art to deploy systems which utilize secondary fuels, there has been no recognition that secondary fuels can be applied to CI and SI engines to reduce NOx emissions. The present invention provides system configurations incorporating secondary fuels and associated methods which can result in high fuel efficiency and NOx pollution reduction, each accompanied by high reliability under engine loading, whereas prior system designs which use secondary fuels for fuel efficiency have not shown consistent performance under the typical ranges of engine operating conditions. With the afore described methods, the benefits of premixing a gaseous second fuel source with air for injection into cylinders of an internal combustion engine can provide NOx reduction with the addition of control systems that are designed to continually monitor and adjust the engine parameters. A feature of illustrated embodiments is adjustment of parameters during or after changes in engine operating conditions. With respect to vehicles operating with a secondary fuel source, it is possible to both optimize fuel efficiency and reduce NOx emissions under both dynamic and steady state modes, e.g., for vehicle operation under acceleration or under constant speed conditions.
Field data can be used to identify key variables and develop input adjustment signals, e.g., based on measured concentration levels, to control NOx concentrations. The control may be effected with an algorithm that generates control signals used to modify engine parameters including parameters conventionally used to adjust engine performance or emission levels.
It is well known that engines operate at an air-to-fuel ratio that is typically lower than the ideal or stoichiometric ratio. A feature of the invention is adjustment of the air-to-fuel ratio for a primary fuel (e.g., gasoline or diesel fuel) in a dual fuel combustion process. The terms “dual fuel process” and “secondary fuel” as used herein refer to supplying an engine with a first, main fuel, e.g., a liquid fuel such as diesel fuel or gasoline, and a second fuel, typically in a lesser quantity, such as a gaseous mixture having a substantial content by volume of reactive hydrogen or another reactive species. With other relevant parameters remaining unchanged, a reduced fuel volume results in an increased air-to-fuel ratio. With a gaseous secondary fuel present in the cylinders adverse effects of reducing the fuel-to-air ratio are less severe than when running the engine without the secondary fuel. Consequently there is an expanded range of acceptable air-to-fuel ratio from which an optimum ratio can be selected to improve fuel economy and or lower NOx emissions. A feedback control loop may be provided to use a parameter in an algorithm which generates an adjustment value to mitigate NOx emissions. The control loop may also be used to adjust the measured parameter by modifying an input variable, e.g., the air-to-fuel ratio. Weighting functions may be assigned to determine relative influence of multiple control loops. The weighting functions may vary temporally or based on engine operating conditions, including ambient states.
During extensive over-the-road testing optimum points at which to shift the magnitudes of the sensor output signals were identified to take full advantage of the addition of the HHO over the full range of operating conditions. To that end the present invention applies a control that continuously reads multiple engine sensors (e.g., fuel manifold pressure, intake manifold pressure, exhaust manifold pressure, exhaust gas temperature, ambient barometric pressure, etc.) and dynamically adjusts those sensor readings to achieve optimum levels of emissions reduction and enhanced fuel economy. The modified levels may then be further adjusted in response to two additional sensors signal outputs: a NOx sensor and an Exhaust Gas Temperature sensor, before the sensor signals are passed on to the ECU. This results in the decreased output of NOx, HC and PE thus reducing the load on EGR systems and exhaust after-treatment systems.
Features of the invention have been illustrated for engines having OEM electronic control systems, but the disclosed concepts may be extended to engines not having such systems. In one series of embodiments, such engines may be equipped with custom versions of an electronic control module to provide one or more of the functionalities which have been disclosed. As another example, for an engine having a mechanical fuel injection system, an analog or digital control may be incorporated to adjust the amount of primary fuel delivered to the engine by electrically or mechanically adjusting the fuel manifold pressure. The pressure adjustment may be had by providing an adjustable relief valve or a selectable secondary relief valve with a lower set pressure than that of the primary relief valve.
While the invention has been described with reference to particular embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. Accordingly, the scope of the invention is only limited by the claims which follow.
This national stage application claims priority to PCT Application PCT/US2014/10936 filed Jan. 9, 2014 which claims the benefit of provisional patent application U.S. 61/750,650 filed 9 Jan. 2013.
| Number | Date | Country | |
|---|---|---|---|
| 61750650 | Jan 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14436986 | Apr 2015 | US |
| Child | 16805813 | US |
