METHOD FOR ACCELERATING FOULING OF INJECTORS IN GASOLINE DIRECT INJECTION ENGINES AND FOR EVALUATING PERFORMANCE OF DEPOSIT CONTROL ADDITIVES

Abstract

A method for fouling an injector of a gasoline direct injection engine, includes the steps of operating the direct injection engine on at least a first stationary engine mode which is defined by a pre-established engine load and a pre-established engine speed. Both the pre-established engine load and the speed are within 35% and 65% of their maximum values, this at least first stationary engine mode being characterized by high particulate matter generation. The direct injection engine is operated on the at least first engine mode for less than ten hours.

A method for evaluating the fouling effect of a gasoline formulation in a gasoline direct injection engine uses the above-described fouling method.

Claims

1. A Method for fouling an injector of a gasoline direct injection engine, which comprises: operating the direct injection engine on at least a first stationary engine mode which is defined by a pre-established engine load and a pre-established engine speed, both the pre-established engine load and speed being comprised within 35% and 65% of their maximum values, this at least first stationary engine mode being characterized by high particulate matter generation with a concentration of particulate matter in exhaust gases which is above 30% of the maximum concentration of particulate matter of the engine in the exhaust gases; wherein the direct injection engine is operated on the at least first engine mode for less than ten hours.

2. The method according to claim 1, wherein operating the direct injection engine comprises alternating operation of the direct injection engine between a first stationary engine mode and a second stationary engine mode, each engine mode being defined by a pre-established engine load and a pre-established engine speed, both the pre-established engine load and speed being comprised within 35% and 65% of their maximum values and being characterized by high particulate matter generation.

3. The method according to claim 2, wherein the GDI engine starts operating at the engine mode having the highest engine load.

4. The method according to claim 2, which further comprises continuously monitoring the particulate matter emission.

5. The method according to claim 1, which further comprises continuously monitoring the injection duration of the injector using external current or voltage measuring means.

6. The method according to claim 1, wherein the direct injection engine is operated for less than eight hours, preferably during six hours.

7. The method according to claim 2, wherein the direct injection engine is operated in the first stationary engine mode and in the second stationary engine mode during time intervals of the same duration.

8. The method according to claim 2, wherein the first stationary engine mode and in the stationary second engine mode are operated during time intervals, each time interval having a duration of at least 1 minute, preferably of 15 minutes.

9. The method according to claim 1, which further comprises continuously monitoring temperature and pressure at pre-established points of the engine.

10. The method according to claim 1, which further comprises: a) determining a maximum concentration of particulate matter of the gasoline direct injection engine in exhaust gases; and b) establishing high particulate matter generation as a concentration of particulate matter in the exhaust gases that is above a 30% of the maximum concentration of particulate matter determined in step a).

11. The method for evaluating the fouling effect of a gasoline formulation in a gasoline direct injection engine, which comprises using the method for fouling an injector of any of the previous claim 1 and operating the gasoline direct injection engine with such gasoline formulation.

12. The method according to claim 11, wherein the gasoline formulation includes a deposit control additive, and the performance of the deposit control additive is evaluated.

13. The method for evaluating an effect of an engine parameter of a gasoline direct injection engine, which comprises using the method for fouling an injector of claim 1 and operating the gasoline direct injection engine with different values of that engine parameter.

14. The method for evaluating an effect of an engine component of a gasoline direct injection engine, which comprises using the method for fouling an injector of claim 1 and operating the gasoline direct injection engine with different designs of the engine component.

15. The method according to claim 14, wherein the engine component is an injector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To complete the description and in order to provide for a better understanding of the disclosure, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the disclosure, which should not be interpreted as restricting the scope of the disclosure, but just as an example of how the disclosure can be carried out. The drawings comprise the following figures:

[0027] FIG. 1 schematically shows a preferred embodiment of test bench prepared for evaluating fouling of injectors.

[0028] FIGS. 2 and 3 schematically show an example of a test cycle followed by the GDI engine, in terms of the engine speed and load, respectively.

[0029] FIG. 4 schematically shows the difference in the injection duration as an example of fouling during a test cycle of a clean injector.

[0030] FIG. 5 schematically shows the evolution of the injection duration using four different formulations in the test cycle.

[0031] FIG. 6 schematically shows the evolution of particulate matter emissions using four different formulations in the test cycle.

[0032] FIG. 7 shows a graphic comparison of the 6-hour fouling test according to the disclosure and a non-accelerated 29-hour test in terms of particulate emission.

[0033] FIG. 8 schematically shows an analysis of the repeatability of the method of the disclosure (seven repetitions performed with the same commercial fuel and under the same conditions).

DETAILED DESCRIPTION OF THE DRAWINGS

[0034] The following description is not to be taken in a limiting sense but is given solely for the purpose of describing the broad principles of the disclosure. Embodiments of the disclosure will be now described by way of example, with reference to the above-mentioned drawings showing elements and results according to the disclosure.

[0035] The method for fouling injectors of the present disclosure is performed using a gasoline direct injection (GDI) engine 10 in a test bed 100, as schematically shown in FIG. 1. In this specific example, the engine installed on the test bed is a 1197 cm3 GDI engine coded EA111 by the Volkswagen Group. The engine has a power of 77 kW, maximum torque of 175 Nm, maximum speed of 5700 rpm and has two valves per cylinder.

[0036] The test bed installation 100 shown in FIG. 1 is formed by: [0037] an electric dynamometer 80 to brake the engine 10, controlled by an automatic system to ensure better engine control and reproducibility; [0038] a lubricating oil recirculating system with temperature (T) control 11; [0039] a refrigeration liquid recirculating system with temperature (T) control 12; [0040] different pressure and temperature sensors to measure and control the engine performance during the test: [0041] ambient conditions (pressure and temperature); [0042] pressure and temperature at intake manifold; [0043] pressure and temperature at exhaust manifold; [0044] pressure and temperature after Three-Way Catalyst (TWC); [0045] lubricating oil temperature; [0046] refrigeration liquid temperature; [0047] injection pressure; [0048] a fuel balance module 20; [0049] a lambda measurement module 30 (to check that the test is carried out with lambda substantially equal to 1); and [0050] particulate matter emission analysing equipment 40.

[0051] The test bed installation 100 further comprises two clamp meters and an angle encoder with resolution of 0.1 CA (crank angle degrees) (block 50 in FIG. 1), so as to measure the activation signal of the injectors of cylinders one and three. The output of this block is introduced in an application 60 which measures with high precision the injection pulse duration (pulse width) in each cylinder. The deviation of the original injector pulse width is used for measuring and quantifying the amount of deposits on the injector holes.

[0052] As also shown in FIG. 1, the engine 10 is connected to the corresponding intake and exhaust manifolds 70 and 75 in order to provide fresh air and dispose exhaust gases respectively. The remaining elements in this FIG. 1 are an air-water intercooler 85 to control the intake air temperature, an air filter 90 to eliminate any particle from the intake air and a three-way catalyst 95 to control pollutant emissions from the engine.

[0053] The method of the present disclosure can be carried out in this test bed, controlled by the electric dynamometer and controlling the fluid temperatures during the test cycle (lubricating oil and refrigerant). The main parameters considered are: [0054] Engine speed (rpm) [0055] Engine load (Nm) [0056] Particulate matter emissions (mg/m3) [0057] Injection duration ( CA)

[0058] In order to define the operation modes of the engine for the method, an initial screening of the engine map is carried out. In these screening, operation modes with a high emission of particles are identified. Typically, these engine conditions are defined in terms of engine speed (measured in rpm) and engine torque (measured in Nm). In this method, two stationary modes at which the particulate matter generation is high (particulate matter concentration in the exhaust gases above 30% of the maximum concentration condition of the engine, with an injector used above 60 h) and at the same time the engine is thermally stable and moderately loaded (below 65% of the maximum load) are chosen. These conditions decrease the time necessary to achieve a high mass of deposits on the injectors. To reinforce the necessity of specific developments around the problem of injector fouling in GDI engines, this methodology has achieved a selection of stationary point/s (when the thermal conditions of the engine are stable) which create high injector fouling positioned very close to normal driving conditions in highways. Thus, injector fouling takes place in usual conditions and points out the relevance of this methodology allowing development processes being evaluated in a working day.

[0059] Due to the influence of the particulate matter concentration inside the cylinder chamber in the injector fouling process, the particulate emission analysing equipment 40 is necessary to select the critical point or points (of high particulate matter concentration and moderate thermal load) to achieve enough mass of deposits in the injector holes along the test which disturb the injector optimal performance. Then the duration of the test can be optimized.

[0060] Once these two engine conditions at which injector fouling takes place rapidly have been determined, an engine cycle is defined by concatenating phases of these modes with duration of more than 1 minute, preferably 15 minutes, as shown in FIGS. 2 and 3, creating a succession of stationary points.

[0061] As it can be seen in FIGS. 2 and 3, in the preferred embodiment the engine cycle is formed by two engine modes, each mode setting the engine to operate at an engine speed and an engine load which are between 35% and 65% of their range. The cycle starts with the engine mode having the higher load during 15 minutes, and then the engine mode is changed to the engine mode having the lower load during another 15 minutes. This process is repeated twelve times to a total of 6 hours.

[0062] In the particular case of the EA111 engine, the worst engine modes chosen are 3300 rpm and 90 Nm, and 3000 rpm and 80 Nm (see FIGS. 2 and 3).

[0063] The test bed also includes temperature and pressure sensors at different points of the engine so as to monitor and register throughout each engine cycle the main engine parameterspressures and temperaturesto ensure that the engine has been operating correctly during the engine cycle. This fact has special relevance to ensure the repeatability and reproducibility of the methodology developed. These parameters provide information about the thermal stabilization of the engine to start the fouling cycle, and also provide information about abnormal measured points; this allows for discarding erratic fluctuation of the engine if the ECU is applying corrections, thereby increasing the precision of the measurements.

[0064] Additionally, particulate matter emissions and injection duration are continuously registered to evaluate the evolution of injector fouling. This evolution can be seen in FIG. 4, which shows the difference in the injection pulse duration during a test cycle of a clean injector (represented by the black solid line) and the increase in the duration of the injection pulse when the injector is fouled (represented by the dotted line): an increase of around 10 CA can be seen.

[0065] This methodology enables the comparison of the effect of fuel formulation and the effectiveness of DCA on injector fouling in a relatively short period of time of just 6 hours, while other methods for evaluating injector fouling require a minimum time around 30 hours.

[0066] The procedure of injector fouling described above can also be used to evaluate the effect of additives both on the keep-clean and clean-up processes. It may also be used to evaluate the deposition of the unburned combustion products on the injector.

[0067] As an example the evolution of the injection duration using four different fuel formulations A, B, C and D in the test cycle is shown in FIG. 5. Formulation A contains no additives; formulation B contains a certain amount of additives; formulation C contains a higher amount of additives than formulation B; and finally, formulation D contains a higher amount of the same additive than formulations B and C. FIG. 6 schematically shows the evolution of particulate matter emissions also using the same four different formulations A, B, C and D in the test cycle. It is apparent that, with the method disclosed in the present disclosure, the effect of the different additives and their concentration in the total formulation of the gasoline can be evaluated in just 6 hours.

[0068] FIG. 7 shows a graphical comparison of the 6-hour fouling test according to the disclosure and a non-accelerated 29-hour test in terms of particulate emission.

[0069] The non-accelerated 29-hour test is based on the methodology used to study the effect of fuel on fouling processes over intake valves in port fuel injector engines. This methodology is based on alternating the engine operation very rapidly (in terms of seconds) between low, medium and high engine regimes and loads. This test repeats the cycle shown in the following Table 1 until the end of the test. It is apparent that the 6-hour test, whose engine conditions have been defined on the basis of their particulate matter emissions, is more severe than the 29-hour test based on another methodology.

TABLE-US-00001 TABLE 1 Description of 29 hours test of GDI injector fouling based on another methodology. Engine speed (rpm) Torque (Nm) Time (s) Mode 1 1000 30 25 Mode 2 1300 30 15 Mode 3 3000 92 10 Mode 4 5000 130 10

[0070] To evaluate the repeatability of the method for accelerated fouling of the present disclosure, the test was repeated seven times using the same fuel. A commercial fuel without any additive was selected, since it provides the worst conditions to accelerate injector fouling, and also the worst statistical condition, because of its higher deposit concentration and the higher dispersion deposition. FIG. 8 shows the results thereof: the standard deviation of the injector duration increases as the injector duration increases. The standard deviation in this test varied between 0.15 and 0.59 crank angle degrees as injection duration increased during the test.

[0071] The precision of the method of the present disclosure enables the evaluation of different fuel formulations, or the use of fuel additives, or other engine modifications (for example, different injector designs) as shown in FIGS. 5, 6 and 8.

[0072] On the other hand, the disclosure is obviously not limited to the specific embodiments described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the disclosure as defined in the claims.