Fuel deposit testing using burner-based exhaust flow simulation system

A method of using an exhaust flow simulation system to test the effects of exhaust system conditions on various materials. A typical exhaust flow simulator is a burner-based system, in which exhaust from burner combustion is exhausted through an exhaust line. A “test coupon” of the material may be placed at an appropriate location in the flow line, and tested to determine how it is affected by the exhaust resulting from various fuels and additives.

TECHNICAL FIELD OF THE INVENTION

The present application relates in general to systems for simulating the exhaust flow of an engine over extended driving conditions and high temperatures.

BACKGROUND OF THE INVENTION

As a result of stricter regulations for automotive emissions, it was desired to design a testing apparatus and procedure for testing emissions control devices. Historically, an actual internal combustion engine was used for such evaluations. However, the use of a real engine for long term testing can be inconsistent, maintenance intensive, and expensive to operate. In addition, a real engine does not conveniently permit the separate evaluation of individual variables, such as the effects of various constituents of fuel and oil.

U.S. Patent Pub. No. 2003/0079520, entitled “Method and Apparatus for Testing Catalytic Converter Durability” and U.S. Patent Pub. No 2004/0007056 A1, entitled Method for “Testing Catalytic Converter Durability”, both describe an exhaust flow simulation system. The system comprises a fuel-combustive burner with an integrated, computerized control system. The system realistically simulates the flow of exhaust gas from an engine under a variety of load conditions.

DETAILED DESCRIPTION OF THE INVENTION

The following description is directed to a burner-based exhaust flow simulation system, which produces a flow of exhaust gas with a composition and temperature corresponding to those produced by the internal combustion engine of a motor vehicle. The system can be used with or without introducing oil to simulate engine oil consumption.

As an example of one application of an exhaust flow simulation system, an emissions control device can be installed on the exhaust line of the system. The effect of extended driving conditions and elevated temperatures on the emissions control device can be simulated. The system can also produce the effects of additives and contaminants from the engine fuel and lubricant oil on the durability of the emissions control device. The system is capable of “aging” the device, which can then be evaluated, and if desired, performance-tested on an actual vehicle.

Other applications of the exhaust flow simulation system are possible. Various sensors, such as those used for emissions monitoring and control, can be tested. Materials used to fabricate any component affected by exhaust gas can be tested. The subject of the testing may be a fuel, an additive, or an oil. Or, various environmental factors may be introduced and their effect evaluated.

The present invention is directed to the testing of the effects of the exhaust flow on a test material. The results of the testing can be evaluated to determine the suitability of the material for use in components that will be exposed to the exhaust gas of a production automobile or other engine-driven equipment. For example, after having been exposed to the simulated exhaust, the material can be examined for deposits, coking, corrosion, heat effects, and other symptoms of exposure to the exhaust flow.

U.S. Patent Pub. No. 2003/0079520 and U.S. Patent Pub. No 2004/0007056, referenced in the Background and incorporated by reference herein, each describes an exhaust flow simulation system with which the invention described herein may be used. However, the invention is not limited to those systems, and in general, can be applied to any burner-based exhaust flow simulation system.

FIG. 1illustrates a burner-based exhaust flow simulation system100having a chamber175for materials testing in accordance with the invention. As explained below, system100is capable of separating the effects of fuel and oil, allowing precise control of each variable. It provides exhaust from combustion of gasoline or various other fuels, liquid or gaseous. The exhaust is generating under conditions of precise air to fuel ratio (AFR) control. The system has an oil atomization and injection subsystem provides definitive isolation of the effects of fuel and of lubricant at various consumption rates and states of oxidation. System100is capable of operating over a variety of conditions, allowing various modes of engine operation to be simulated, for example cold start, steady state stoichiometric, lean, rich, or cyclic perturbation.

System100has eight subsystems: (1) an air supply system to provide air for combustion to the burner, (2) a fuel system to provide fuel to the burner, (3) a burner system to combust the air-fuel mixture and provide the proper exhaust gas constituents, (4) a heat exchanger to control the exhaust gas temperature, (5) an oil injection system, (6) a secondary air injection system, (7) a materials testing chamber, and (8) a computerized control system.

Primary Air Supply System

An air blower30draws ambient air through an inlet air filter20and exhausts a pressurized stream of air. A mass air flow sensor50monitors air flow. The volume of air supplied is set by adjusting a bypass valve40to produce a desired flow rate of air.

The air blower30, filter20, and the mass air flow sensor50may be of any conventional design. An example of a suitable air blower30is an electric centrifugal blower.

Blower30may also be used for cooling system100. For example, if the burner is off, system100may be rapidly cooled by using blower30to blow forced air on any part of system100.

Fuel Supply System

A fuel pump10pumps engine fuel through a fuel line12to a fuel control valve14. As used herein, the term “engine fuel” means any substance which may be used as a fuel for an internal combustion engine, including, but not necessarily limited to, synthetic gasoline, diesel, carbon-based liquefied fuel, methanol, or compressed natural gas.

An example of a suitable fuel control valve14is a solenoid valve that receives a pulse-width modulated signal from the control unit180, and regulates the flow of fuel to the burner60in proportion to the pulse width. From the fuel control valve14, the fuel is delivered to the fuel injector16associated with burner60.

Burner

Burner60produces a desired combustion of the fuel and air. In the example of this description, burner60is a swirl-stabilized burner capable of producing continuous combustion at rich, lean, or stoichiometric air-fuel ratios.

FIG. 2illustrates burner60in further detail. Burner60comprises a plenum chamber200and a combustion tube210separated by a swirl plate18. The combustion tube210is constructed of material capable of withstanding extremely high temperatures. Preferred materials include, but are not necessarily limited to INCONEL or stainless steel, and optionally can have a window, made from a material such as quartz or other material that transmits IR, visible, or UV energy.

Air and fuel are separately introduced into the burner60. Air from mass flow sensor50is ducted to the plenum chamber200, then through the swirl plate18into the burner tube.

The swirl plate18is equipped with a fuel injector16, implemented as an air-assisted fuel spray nozzle16at the center of the swirl plate18. The swirl plate18has a central bore255, and spray nozzle16is fitted to the swirl plate18at this central bore255using suitable means. Fuel from fuel supply line14is delivered to the spray nozzle16, where it is mixed with compressed air from air line15and sprayed into the combustion tube210. The compressed air line15provides high pressure air to assist in fuel atomization.

Swirl plate18is capable of producing highly turbulent swirling combustion, so as to provide a complex pattern of collapsed conical and swirl flow in the combustion area. The flow pattern created by the swirl plate18involves the interaction of a number of jets through swirl plate18. The arrangement and angling of these jets dictate how they direct air. For example, “turbulent jets” may be used to direct the air toward the central bore. Other jets may be used to direct air from the outer circumference of the swirl plate18. The precise dimensions and angular orientation of the jets may vary. The jets may further be used to prevent the flame from contacting the air assisted spray nozzle16.

The swirling flow within tube210collapses and expands, preferably at intervals that are substantially equivalent in length to the inner diameter of combustion tube210. In the example of this description, the inner diameter of the combustion tube210is 4 inches, and the intervals at which the swirling flow collapses and expands is every 4 inches.

Combustion tube210is equipped with several spark igniters220. In a preferred embodiment, three substantially equally spaced igniters220are located around the circumference of the combustion tube in the gas “swirl path” created by the swirl plate18. In a preferred embodiment these igniters220are marine spark plugs.

The swirl pattern within combustion tube210may be used to define the location of igniters220along the combustion tube210. In the embodiment described herein, the igniters are located at first and second full expansions along the path of inner swirl jets.

Swirl plate18may be implemented as a substantially circular disc having a thickness sufficient to fix the air flow pattern and to create an “air shroud” that is effective to protect the fuel injector. In the example of this description, this thickness generally is about ½ inch or more. The swirl plate18is made of substantially any material capable of withstanding high temperature, a preferred material being stainless steel.

In some embodiments, suitable for combustion of low volatility fuels, the combustion tube210is further equipped with ceramic foam located downstream from the spray nozzle16. Various materials may be used, preferably SiC ceramic foam.

Heat Exchanger

Referring again toFIG. 1, the exhaust from the burner60is routed to a heat exchanger70. The heat exchanger70may be of any conventional design known to a person of ordinary skill in the art. In the example of this description, the heat exchanger70consists of two sections. An upstream section consists of a water jacketed tube. A downstream section is a vertical cross flow shell and tube heat exchanger. The vertical cross flow design minimizes steam formation and steam trapping within the cooling tubes. The heat exchanger70is provided with an inlet water line80and an outlet water line90which supply and drain cooling water. The heat exchanger70cools the exhaust gas to a temperature simulating that which is present at the inlet to an emissions control device170.

Oil Injection System

Downstream from the burner60, the exhaust gas is routed past an oil injection section110, which may be used to introduce a precisely controlled amount of lubricating oil into the exhaust stream. In the example of this description, the oil injection section110is installed in a four inch diameter pipe.

The oil injection section110provides an atomized oil spray comprising oil droplets with a sufficiently small diameter to vaporize and oxidize the oil before it reaches the emissions control device170. The oil injection system110may include means for metering the consumption rate and oxidation state (unburned, partially burned, or fully burned) of the oil delivered downstream the oil injection.

In operation, a sample of lubricant oil is withdrawn from an oil reservoir150by means of an oil pump160. Substantially any type of pump may be used, preferably a peristaltic pump which feeds the oil from the reservoir through an oil injection line140and into a water cooled probe120from which the oil is injected into the exhaust gas.

Secondary Air Injection

Secondary air injector195is placed upstream of the emissions control device170, and supplies air into the exhaust flow line193. Although, this description is in terms of supplying air, injector195may be equivalently used to supply any other type of gas into the exhaust flow. One application of the secondary air injector195is to help control the composition or heat of the exhaust gas. For example, an injection of oxygen may be used to provide thermal excursions.

FIG. 3is a perspective view, to illustrate secondary air injector195in further detail. A secondary air inlet311receives the secondary air, which is typically from a pressurized source. A hollow ring310has a solid outer wall313and a perforated inner wall312, through which the air enters the exhaust line193.

In the example ofFIG. 3, air injector195is designed as an add-on part that can be installed into a gap in the exhaust line193. Accordingly, it has bell-type sleeves301and302for snugly accepting ends of the exhaust pipe. Other means of attachment may be used. It possible to modify air injector195so that it is an integral part of exhaust line193, such as by perforating a portion of exhaust line193with holes to form the inner wall312of secondary air injector195.

In the example of this description, inner wall312has eight air injection ports315. These air injection ports315are placed22degrees off center from the main air inlet311to help provide a even pressure distribution and to permit even air injection into the exhaust flow tube. The use of inner wall312with its multiple injection ports permits the pressured air to create a jet into the exhaust flow resulting in deeper penetration into the exhaust flow stream for better mixing.

If desired, the ports of inner wall312may be threaded to accept through-drilled set screws (not shown) at all eight injection locations. The set screws are the appropriate diameter to create deep penetration of the air jet perpendicular to the exhaust stream flowing up to 80 scfm or higher. The penetration depth may be changed by varying the diameter of the set screws.

In the example of this description, the air injection ports315are bored perpendicular to the surface of inner wall312. Hence, the air enters perpendicularly to the exhaust flow. However, in other embodiments, they may be angled to provide higher turbulence resulting in better air distribution in the exhaust stream.

Downstream of secondary air injector195, the exhaust gas, now mixed with the injected oil and secondary air, passes through an emissions control device170, following which the exhaust gas is vented to the atmosphere.

Materials Testing Chamber

As stated above, in addition to testing actual emissions control devices installed on the exhaust flow line, system100can be used to test all sorts of materials and devices that may be exposed to the exhaust gas and/or its elevated temperatures. For example, a common problem in engines of all types is the buildup of deposits on valves. These deposits vary as a function of temperature, pressure, fuel type, and additives.

FIG. 4illustrates the interior of test chamber175, and how a sample of material401may be placed in test chamber175and exposed to the exhaust flow. Test chamber175permits fuels and fuel additives to be evaluated by examining deposits on test samples of materials placed in the exhaust flow stream.

The test material401, also referred to herein as a “test coupon”, may be placed at any appropriate location along the flow tube of system100to achieve the desired exhaust gas exposure and thermal experience. InFIG. 1, the location of test chamber175downstream of secondary air injector195is arbitrary—it may be placed anywhere in the exhaust stream downstream burner60.

By placing a sample of material in the exhaust flow, different materials and coatings may be tested for various applications, such as intake and exhaust valve materials, valve seat materials, cylinder wall materials, and piston materials. The test coupon may be installed throughout a complete “aging” cycle, to determine long terms effects of the material. Various materials can be tested with various fuels, oils, and additives.

For example, thermal excursions may be achieved by controlling the stoichiometry of the exhaust gas and by injection of oxygen or other gases into the exhaust stream. The effect of high temperature and rapid temperature increases on the material may be evaluated. Blower30(or other cooling equipment) may be used to rapidly cool the system100or the exhaust itself, thereby permitting the effect of rapid temperature drops to be evaluated.

Test chamber may also be designed so that the sample is exposed to the spectral (UV, visible, or IR) energy of the burner flame. This spectral emission exposure may be controlled, such that testing involves multi-parameter control, with the parameters including spectral exposure as well as exposure to exhaust components and thermal conditions. If there are spectral effects on the material itself, the exhaust components, or thermal conditions, then the spectrally excited states and the effects on deposit formation can be tested at various areas within the flow line of system100. Control of spectral effects can be accomplished by providing a controllable shield of the sample from the burner flame.

In other embodiments, the test sample need not be in direct contact with the exhaust gas flow. For example, a test for the effects of combustion could call for placing a test sample of material in burner60or upstream of burner60. In the latter case, the exposure environment is that which a material would undergo in the intake portion of an engine. System100could also be equipped with an exhaust gas recirculation (EGR) path and a test sample placed in the flow line or the EGR path, such that the effects of recirculated exhaust on the sample may be tested.

Control Unit

Referring again toFIG. 1, control unit180receives input from various sensors associated with system100and delivers control signals to its various actuators. Control unit180may be implemented with conventional computing equipment, including processors and memory. It is equipped with suitable input devices, a monitor, and a multi-function data acquisition card, connected to an digital relay module to monitor and record system information, and to control system electronics. Control unit180is programmed to run various simulation programs.

The sensors include sensor50and may further include sensors for measuring various gas contents and flows. Various measured parameters collected by control unit180may include: the mass air flow in the system, the air/fuel ratio (linear and EGO), the exhaust gas temperature at the outlet from the heat exchanger, the exhaust gas temperature at the inlet to the emissions control device, and the exhaust gas temperature at the outlet from the emissions control device, and various chemical constituents of the exhaust. The information measured by the sensors is transmitted by electronic signals to control unit180, which measures all of the monitored parameters on a periodic basis and stores the measurement data in memory.

The actuators controlled by control unit180include the various injectors, pumps, valves, and blowers described above. More specifically, control unit180controls the air-to-fuel ratio by modulating the fuel delivered to the fuel injector16under either an open loop or closed loop control configuration. Control unit180further provides a means to control ignition, air assist to the fuel injector, auxiliary air, fuel feed, blower air feed, and oil injection. An example of a suitable control system would be a proportional integral derivative (PID) control loop.

Control unit180monitors system100for safety. For example, it may be used to verify that the burner is lighted and that the exhaust is within specified limits for both temperature and air to fuel ratio. The control unit180is programmed to identify and address failure modes, and to monitor and control system100to a safe shutdown if a failure mode is detected.

Interactive interface programming of control unit180permits an operator to develop and run various aging cycles. The operator can use control unit180to investigate the effects of exposure to various oils and other fuel contaminants or additives. The inlet temperature to the emissions control device170can be adjusted over a wide range of temperatures.

Control unit180may be used to switch power to the blowers and fuel pump, as well as control the air assisted fuel injectors, burner spark, oil injection, and auxiliary air. System temperatures, mass air flow for the burner air, and the burner air to fuel ratio are measured and converted to engineering units. The software program uses measured data to calculate total exhaust flow and burner air to fuel ratio, and to check conditions indicative of a system malfunction. The burner air to fuel ratio may be controlled as either open or closed loop, maintaining either specified fuel flow or specified air to fuel ratio. Air to fuel ratio control is achieved by varying the rate of fuel delivered to the burner. Whenever necessary, open loop control can be activated allowing the operator to enter a fixed fuel injector pulse duty cycle. Closed loop control can be activated in which the actual burner air to fuel ratio is measured and compared to the measured value of the air to fuel setpoint and then adjusting the fuel injector duty cycle to correct for the measured error.