Calibrated Non-Thermal Plasma Systems for Control of Engine Emissions

Abstract

The instant invention is based on techniques for using non-thermal plasma reactors in both the main exhaust pipe and in the exhaust gas recirculation feed pipe to reduce particulate matter sufficiently to meet EPA limits for PM and enhanced exhaust gas recirculation to meet NOx limits. More specifically, it is based upon the use of a non-thermal plasma device in which a high voltage charge in the plasma reactor causes extremely rapid oxidation of soot particles in the exhaust stream of an engine and further chemical reactions that aid in the reduction of NOx. The primary benefit of this technology is that it can be calibrated to optimize both soot and NOx reduction.

Claims

1. A calibrated non-thermal plasma system for control of internal combustion engine emissions, comprising: an internal combustion engine including an exhaust gas recirculation system receiving exhaust gas from an outlet for said engine and recirculating a portion of said exhaust gas to an engine intake for said engine while a remaining portion of said exhaust gas exits said recirculation system via a recirculation system outlet for processing in aftertreatment systems before exiting to the atmosphere; at least one non-thermal plasma reactor receiving and processing exhaust gas from said recirculation system intermediate said engine outlet and said recirculation system outlet; an air source providing air for injection into said exhaust stream intermediate said engine and said non-thermal plasma reactor via a control valve; and a control system to maximize removal of particulate matter from said exhaust gas stream comprising an electronic control module controlling at least one of power provided to said non-thermal plasma reactor, and said control valve providing air for injection into said exhaust stream.

2. The system of claim 1, wherein said aftertreatment systems include at least one of: a diesel oxidation catalyst, a diesel particulate filter, and a selective catalytic reduction system.

3. The system of claim 1, wherein said control system monitors oxygen levels intermediate said engine outlet and said at least one non-thermal plasma reactor, and actuates said control valve to maintain oxygen levels in said non-thermal plasma reactor at an optimum level to maximize elimination of particulate matter from said exhaust gas stream.

4. The system of claim 2, wherein said control system monitors oxygen levels intermediate said engine outlet and said at least one non-thermal plasma reactor, and actuates said control valve to maintain oxygen levels in said non-thermal plasma reactor at an optimum level to maximize elimination of particulate matter from said exhaust gas stream.

5. The system of claim 1, wherein said control system monitors oxygen levels intermediate said engine outlet and said at least one non-thermal plasma reactor, and actuates a power supply for said at least one non-thermal plasma reactor to maintain power levels in said at least one non-thermal plasma reactor at an optimum level to maximize elimination of particulate matter from said exhaust gas stream.

6. The system of claim 2, wherein said control system monitors oxygen levels intermediate said engine outlet and said at least one non-thermal plasma reactor, and actuates a power supply for said at least one non-thermal plasma reactor to maintain power levels in said at least one non-thermal plasma reactor at an optimum level to maximize elimination of particulate matter from said exhaust gas stream.

7. The system of claim 3, wherein said control system monitors oxygen levels intermediate said engine outlet and said at least one non-thermal plasma reactor, and actuates a power supply for said at least one non-thermal plasma reactor to maintain power levels in said at least one non-thermal plasma reactor at an optimum level to maximize elimination of particulate matter from said exhaust gas stream.

8. The system of claim 4, wherein said control system monitors oxygen levels intermediate said engine outlet and said at least one non-thermal plasma reactor, and actuates a power supply for said at least one non-thermal plasma reactor to maintain power levels in said at least one non-thermal plasma reactor at an optimum level to maximize elimination of particulate matter from said exhaust gas stream.

9. The system of claim 1, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

10. The system of claim 2, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

11. The system of claim 3, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

12. The system of claim 4, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

13. The system of claim 5, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

14. The system of claim 6, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

15. The system of claim 7, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

16. The system of claim 8, wherein at least one of: said at least one non-thermal reactor comprises at least one of: a plurality of non-thermal reactors arranged in parallel, and a plurality of non-thermal reactors arranged in series, and a multiplex voltage controller provides power to said at least one non-thermal reactor.

17. The system of claim 1, wherein at least one of: said at least one non-thermal reactor voltage is maintained at approximately 25,000 Volts, and Oxygen maintained at approximately 18-25% of the exhaust gas stream entering said at least one non-thermal reactor.

18. The system of claim 2, wherein at least one of said at least one non-thermal reactor voltage is maintained at approximately 25,000 Volts, and Oxygen maintained at approximately 18-25% of the exhaust gas stream entering said at least one non-thermal reactor.

19. The system of claim 3, wherein at least one of: said at least one non-thermal reactor voltage is maintained at approximately 25,000 Volts, and Oxygen maintained at approximately 18-25% of the exhaust gas stream entering said at least one non-thermal reactor.

20. The system of claim 4, wherein at least one of: said at least one non-thermal reactor voltage is maintained at approximately 25,000 Volts, and Oxygen maintained at approximately 18-25% of the exhaust gas stream entering said at least one non-thermal reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further object and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

[0022] FIG. 1 provides a schematic diagram of a prior art system of emission treatment in association with a diesel engine.

[0023] FIG. 2A provides a first schematic diagram of an emission treatment system in accordance with the teachings of the invention in association with a diesel engine, illustrating a single reactor NTP system inserted into the exhaust stream prior to the Exhaust Gas Recirculation tap and other features.

[0024] FIG. 2B provides a second schematic diagram of an emission treatment system in accordance with the teachings of the invention in association with a diesel engine, illustrating the same concepts as FIG. 2A with the addition of a temperature sensor in the exhaust stream and other features.

[0025] FIG. 2C provides a third schematic diagram of an emission treatment system in accordance with the teachings of the invention in association with a diesel engine, illustrating the same concept as FIG. 2B with the addition of a multiplexer connected to the NTP system power supply and other features.

[0026] FIG. 2D provides a fourth schematic diagram of an emission treatment system in accordance with the teachings of the invention in association with a diesel engine, illustrating the same concepts as FIG. 2C with the application to a multiple reactor NTP system and other features.

[0027] FIG. 3A provides experimental data showing the impact of a fixed voltage at two vehicle speeds, 40 and 50 mph, with the highest PM reduction achieved at 94.1%.

[0028] FIG. 3B provides experimental data showing the impact of varying voltage and rpm and sampling exhaust at three separate sites in the exhaust system, with highest PM reduction achieved at 86.9%.

[0029] FIG. 3C provides experimental data showing the impact of varying voltage and rpm and sampling exhaust at two separate sites in the exhaust system, with highest PM reduction achieved at 100%.

DESCRIPTION

[0030] As previously noted, the inventors have determined that the overall efficiency of the NTP 5 reactor can be enhanced by assuring an abundance of oxygen. The following two examples of experimental results achieved further confirm these findings.

Example 1: Dynamometer Tests of a 2010 Freightliner M2 Tractor Equipped with a Cummins 8.3 Liter Diesel with Exhaust Gas Recirculation (EGR) 2 and DPF 1 Aftertreatment—Engine Out Overall Emissions

[0031]

TABLE-US-00001 PEMS Emission Analyzer Aggregate Summary - Average Values O2[%] NOx[ppm] FC[g/s] PM10[mg/s] 50 MPH 12.16 142 5.32 0.449 30 MPH 15.82 132 3.38 0.298

Example 2: Dynamometer Tests of a 2010 Freightliner M2 Tractor Equipped with a Cummins 8.3 Liter Diesel with Exhaust Gas Recirculation 2 and DPF 1 after Treatment—Engine Out and Tailpipe Particulate Matter (PM) at Various Engine Operating Modes

[0032]

TABLE-US-00002 Gas Analyzer PM Level Correlation (10 mg/sec) NTP System with Gravimetric Filter Engine Tailpipe TP % Residual Samples Out (TP) Steady Capac.* PM Level 30 MPH Steady Throttle 0.2724 0.0378 30 MPH Fan Clutch Activated 0.5876 0.0421 10.2% 30 MPH Acceleration, Idle to 0.7867 0.0422 1.11% 30 MPH 30 MPH Aggregate 0.294 0.0392  3.7% .sup. +30% 50 MPH Steady Throttle 0.3277 0.0362 50 MPH Fan Clutch Activated 0.559 0.0417 15.2% 50 MPH Acceleration Idle to 1.750 0.1283  254% 50 MPH 50 MPH Aggregate: 0.450 0.045 .sup. 24% +24.5% *Residual Capac. = NTP % PM Reduction per Gravimetric Analysis minus Tailpipe PM % Steady without NTP.

[0033] The above research clearly indicates that the usage of NTP 5 as a means of reducing PM and NOx in diesel exhaust gases is a process that depends upon oxygen availability in the exhaust stream and that the efficiency of the process is dependent upon both the power available in the NTP 5 as well as upon the operating mode of the engine. Therefore, application of NTP 5 requires a calibration of power availability at each NTP 5 reactor in the exhaust stream as well as insurance of sufficient oxygen availability to maximize PM reduction at various driving modes of the vehicle. The following embodiments achieve those requirements by integrating insertion of NTP 5 enhancements to existing aftertreatment systems, with the additional potential that some portions of the existing aftertreatment systems may be eliminated or down-sized. (See, also, FIGS. 3A-3C, which serve to reinforce the concepts already presented that the efficiency of PM reduction is the result of calibrated factors that comprehend engine load and RPM).

[0034] As noted, FIGS. 2A through 2D illustrate various system arrangements in keeping with the teachings of the invention. FIG. 2A illustrates a single NTP 5 reactor insertion into the exhaust stream prior to the Exhaust Gas Recirculation 2 tap, with the additional provision of air (or oxygen) injection at the NTP 5 reactor controlled by a valve between the air source 7 and the NTP 5. Any number of discs within the NTP 5 reactor are included and air injection rate is controlled to maximize efficiency (sufficient residual capacity) of PM removal for various engine operating modes. FIG. 2B illustrates the same concepts as FIG. 2A with the addition of a temperature sensor 8 in the exhaust stream connected to a thermostatically controlled valve for calibration of the air (or oxygen) injection rate. FIG. 2C illustrates the same concept as FIG. 2B with the addition of a multiplexer 9 connected to the NTP 5 system power supply in preparation for power sharing to multiple NTP 5 reactors. FIG. 2D illustrates the same concepts as FIG. 2C with the application to multiple NTP 5 reactors for maximum efficiency in PM removal and NOx reduction through pretreatment of the gases entering either the Exhaust Gas Recirculation 2 loop or the main aftertreatment system or both. As will be noted, the multiple NTP 5 reactors are (and can) be arranged in both series and parallel arrangements.

[0035] While the embodiments are illustrated as capable of operation as independent systems, they are also capable of being separately controlled by linkage with the main control system of the engine. It is of primary importance, and is indeed the essence of the claims, that the NTP 5 system be calibrated to work in concert with the other control systems of the engine and be both sized and calibrated in such a manner as to achieve optimum reactivity and capacity for both PM and undesirable exhaust gas reductions. The sizing and calibrations of the NTP 5 system is achieved through the application of a mathematical model already existing in current electronic control modules 6 which comprehends the premeasured loading of the engine, its operating modes and the resultant exhaust stream variables, including oxygen levels. Radial clearance flow, flow rate of the exhaust, and the electrical potential across the radial clearance are examples of key parameters included in the model. That modeling is assumed in the claims.

[0036] Essential to the success of NTP 5 as a means of controlling PM and exhaust gases in a diesel engine is the provision of power sharing for maximum efficiency at each NTP 5 reactor. Therefore, the mathematical model used by the ECM 6 predetermines the necessary power at each reactor for various engine modes and allows calculation of how much power must be available to assure sufficient residual capacity at each reactor. Likewise, the model allows prediction of the necessary oxygen availability at each reactor so that the residual capacity is optimized by the availability of sufficient oxygen. In practice, the inventors have found that NTP 5 voltage should be maintained at approximately 25,000 Volts, while Oxygen levels should comprise approximately 18-25% of that gas stream by volume. (Cf., FIGS. 3A through 3C). Hence, these will generally be considered optimum levels to be maintained by the system of the invention.

PARTS LIST

[0037] 1 diesel particulate filters (“DPFs”) [0038] 1A diesel oxidation catalyst (“DOC”) [0039] 2 exhaust gas recirculation (“EGR”) [0040] 3 selective catalytic reduction (“SCR”) [0041] 3A ammonia oxidation catalyst (“AOC”) [0042] 4 diesel exhaust fluid (“DEF”) [0043] 5 nonthermal plasma generator or reactor (“NTP”) [0044] 6 electronic control module (“ECM”) [0045] 7 air source or air compressor [0046] 8 temperature sensor [0047] 9 multiplexer [0048] 10 variable geometry turbocharger (“VGT”)

[0049] In view of the foregoing, it should be clear that numerous changes and variations can be made without exceeding the scope of the inventive concept outlined. Accordingly, it is to be understood that the embodiment(s) of the invention herein described is/are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiment(s) is not intended to limit the scope of the claims, which recite those features regarded as essential to the invention.