Internal-combustion engines – Charge forming device – Gaseous fuel and air mixer
Patent
1987-10-27
1989-09-19
Cross, E. Rollins
Internal-combustion engines
Charge forming device
Gaseous fuel and air mixer
123585, 123438, F02B 4300
Patent
active
048671274
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an arrangement for regulating the combustion air proportions also known as air to fuel ratio and designated by the greek letter lambda .lambda., in the case of a gas engine intended for lean mixture operation, in the induction line of which there is an air-gas mixer and possibly a mixture compressor, a lambda controller downstream of which, for varying the combustion air proportions, there is a positioning device for adjusting the air-gas mixer, and also an output measuring device for ascertaining the engine output.
Where gas engines are concerned, it is known to use exhaust gas catalysts in order to reduce the emission of harmful substances, particularly the components NO.sub.x, CO and C.sub.n H.sub.m. When using a three-way catalyst to reduce the aforesaid harmful substance components NO.sub.x, CO and C.sub.n H.sub.m, the gas engine is operated within the range of a combustion air ratio of .lambda.=1, i.e. in the region of the stoichiometric combustion air ratio. In order to achieve a satisfactory conversion rate of the three-way catalyst for all three aforesaid harmful substance components and in order thus to achieve a reduction in the overall emission of pollutants, the combustion air proportion .lambda. must be regulated and maintained within a very narrow range, the so-called lambda window. For example, this lambda window may lie in the range from 0.986 to 0.990. Only when the lambda value is within this narrow range is optimum operation of the three-way catalyst assured.
In the case of a known arrangement, regulation is effected via a zirconium dioxide probe which measures in the waste gas the 0.sub.2 partial pressure in relation to the 0.sub.2 partial pressure of the environmental air. Despite a temperature compensation of the regulator, the narrow prescribed lambda window can scarcely be maintained in practice. Above all in the event of fluctuations in the gas composition such as occur with dump gas, and the fluctuations in heating output which are connected therewith, it is impossible to achieve an optimum efficiency in the known waste gas catalyst which is regulated via a lambda probe.
Further disadvantages of any arrangement working with a threeway catalyst reside in that any pollutants occurring in the gas can rapidly damage the catalyst and the probe and in that the consumption of the gas engines is relatively high. Furthermore, there is a high thermal loading on the engine components.
These last-mentioned disadvantages can be prevented by operating the gas engine on a lean mixture, with which it is possible to avoid the use of a waste gas catalyst. Operating on a lean mixture generally means that the gas engine is operated on a mixture having an increased combustion air ratio (e.g. .lambda.=1.3 to 1.7), in other words in which there is an excess of air over the stoichiometric quantity of air. When operating under such conditions, mainly the NO.sub.x pollutant components in the waste gas decrease rapidly with increasing .lambda.. But also the CO and HC waste gas components are intensely reduced in comparison with .lambda.=1 operation. In order to keep the NO.sub.x pollutant components in the waste gas below a required level (for example 500 mg/Nm.sub.3), therefore, it is necessary to operate with high combustion air ratios (e.g. .lambda.=1.6). If the lambda values are too high (if the mixture is too lean), combustion failures can occur. Therefore, the value of the combustion air proportions must even with lean operation, be kept within a lambda range, the bottom limit of which is determined by the required NO.sub.x pollutant emission and of which the upper limit represents the stalling limit.
The advantage over the narrow lambda window in the case of three-way catalysts, which lies within the region of the stoichiometric lambda value, resides in that the above-defined lambda range is with lean operation substantially wider (by factor of 20 or more) than the required lambda window for a three-way catalyst.
Typical widths of lambda range li
REFERENCES:
patent: 4430978 (1984-02-01), Lewis et al.
patent: 4446940 (1984-05-01), Sakakibara
patent: 4537172 (1985-08-01), Kanehara et al.
patent: 4617904 (1986-10-01), Pagdin
patent: 4635609 (1987-01-01), Seppen et al.
Gruber Friedrich
Knippitsch Stefan
Quirchmayr Gerhard
Cross E. Rollins
Jenbacher Werke Aktiengesellschaft
LandOfFree
Arrangement for regulating the combustion air proportions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Arrangement for regulating the combustion air proportions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Arrangement for regulating the combustion air proportions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-361475