DE697505C - Process for the operation of mixture-compressing four-stroke internal combustion engines for gaseous fuels - Google Patents

Description

Method for operating mixture-compressing four-stroke internal combustion engines for gas-fired fuels With the previously known methods for increasing performance gas-compressing internal combustion engines, especially gas engines, generally only the air is compressed. Part of the compressed air serves to flush the hot residual gases out of the compression chamber, the remaining part as load # air.

Because after rinsing already a large Lu # tmenge in the compression chamber of the cyl - inders located and because the gas is almost always not under such high pressure as the air, the air must be heavily throttled during Ansaugehubes to provide the required amount of gas in to get the cylinder; In such machines, the intake line is almost along its entire length below the atmospheric line; the work involved in the pre-compression of the air is therefore destroyed by the throttling.

Methods are also known to increase the performance of such machines in which air and gas are separated under positive pressure to the working cylinder of the machine be guided. You can then build the inlet increase so that initially only air enters the cylinder and flushes out the residual gases, then a gas-air mixture occurs expediently with excess gas during the suction stroke in the machine and finally again air. In such machines, the suction line does not need less at full load to lie on the atmospheric line, but it lies at lower loads including, because at lower loads, the gas-air mixture volume is reduced by throttling is reduced during the suction stroke.

Also here, except at full load, the workload for the Compression_ of. Air and gas not or only partially recovered; the loading work such machines is so big.

In the case of the two working methods mentioned, the end of the Eles intake stroke with the help of the overpressure under which the air or the air and the gas are, the cylinder charged to get a larger cargo weight that charging is due to the associated compression of the already existing in the cylinder Mixture associated with an increase in temperature; the temperature deg Mixture is increased unpleasant in this way.

It is known that you can increase the performance of gas engines by 20 to 30% with such work processes, without increasing the thermal stresses on the cylinders, pistons, etc. The reason is that as a result of rinsing the hot residual gases, the temperature of the intake mixture is much lower than in unwashed machines and that the hot cylinder parts are cooled by means of the cold purge air.

It goes without saying that in such working processes there is air or air and gas cooled after compression.

Compared to these methods, which aim to increase the performance of the machines, an older method is previously known, which aims not to increase performance, but to reduce heat consumption, which is associated with a reduction in performance. In this process, the residual gases are also flushed out with pressurized air; During the intake stroke, gas and air are compressed in a common centrifugal fan and, without being cooled, are fed to the cylinder at such a low pressure that no overpressure occurs in the cylinder. After two thirds of the intake stroke, the inlet valve closes and the gas-air mixture expands to the end of the intake housing, up to such a negative pressure that the end point of the extension line of the working stroke is on the atmospheric line. Such a machine works with favorable heat consumption, but so little power that the machine does not work economically.

This is how this machine works at full load; like they do with small loads works is not specified.

A well-known drawback with all mixture-compressing machines is the strong increase in fuel consumption with decreasing load.

The purpose of the present invention is to increase in such machines the performance without increasing the thermal stresses considerably higher than the previously known levels to reduce the loading work strong and the fuel needed - to design effective at decreasing load In order to achieve these goals is proposed according to the invention to supply the inlet of the machine with gas and air, separated and cooled in the usual way, under excess pressure and to close off their inlet cross-sections even at full load of the machine before the end of the filling stroke, approximately after 3/4 of its way, and then in the cylinder the mixture that is under excess pressure can be expanded adiabatically to the end of the stroke.

The overpressure under which the charge components are fed to the inlet should be sG high above in order to achieve the desired increase in performance the atmosphere lie that with full load of the machine the pressure in the cylinder at the end the adiabatic expansion following the filling by a maximum of one low level below atmospheric pressure and thus the pressure at the end of the working stroke is pleasantly above atmospheric pressure.

Before the start of the filling stroke, of course, the person under excess pressure occurs Air alone in the cylinder, expediently during most of the exhaust stroke, to flush out the hot residual gases.

The filling level of the machine at full load depends on the overpressure under which the load components are; the greater the overpressure, the smaller the degree of filling.

The adiabatic expansion of the mixture in the cylinder is associated with a corresponding cooling. In this way, the temperature of the gas-air mixture at the end of the loading stroke is considerably lower - than with the previously known machines; and this lower starting temperature of the compression allows the machine with larger increases in performance than with the - to operate previously known power increase method, without the thermal stresses of the machine are greater than previously. Of course, if the machine is overloaded, the filling can be increased accordingly.

In order to achieve the desired lower fuel consumption with decreasing stress wild supplied mixture quantity not 'reduced by throttling but durchVerkleinern the filling. If this happens, the adiabatic expansion is lengthened and the final temperature and pressure drop further. As a result, slide rams are driven with less stress at greatly reduced temperatures and pressures.

The operation of a machine that operated with the new process is based on the attached diagram, which shows the loading stroke of the machine, explained.

We assume, for example, that air and gas are fed separately to the machine with 0.3 at overpressure. Let the compression ratio of the machine be = 5. During the extension stroke or the last part of the same, only air enters the cylinder to flush out the hot residual gases. From the beginning of the loading stroke, even earlier if desired, gas and air enter the cylinder, line, together under their overpressure. In b #, the control closes the mixture admission at full load, and the mixture expands adiabatically to the end of the stroke according to the line bc. If the temperature of the gas-air mixture in the cylinder of the scavenged machine before the adiabatic expansion is 2o 'and the filling is 75 "/", the temperature at point c is the pressure is 0.95 ata ..

In order to reduce the machine output, the filling is reduced, for example to 50% up to point d; at the end point e of the adiabatic expansion the temperature is then = -36 ', the pressure = 0.63 ata.

With a filling of 25 '/ "point f, the adiabatic expansion« runs along the line fg; the temperature at point g is 721, the pressure - 0.36 ata.

The method has the following advantages: The loading work of the machine becomes low, because all losses caused by the usual throttle control are eliminated.

When the machine is at full load, the same thermal loads of the cylinder and the other components that come into contact with the hot fire gases achieve a greater increase in performance because the temperature at the beginning of compaction is less than with the previously known machines.

With decreasing machine performance, compared to the previously known Machines that work with throttle control, the specific heat consumption is significant cheaper because as a result of the lower temperatures and pressures, the cooling water and Exhaust losses become smaller.

The proposed regulation of the filling can be achieved with controls, as they are common today with valve steam machines.

The new method appears to be particularly valuable for gas engines that are connected to gas lines with a corresponding excess pressure, for example to long-distance gas lines, because in this case only the air, for example by a fan driven by an exhaust gas turbine, has to be pressurized. e

Claims (2)

PATENT CLAIMS: i. A method of operations of mixture - four-stroke internal combustion engine for gaseous örmige fuel e, in which the exhaust gases are purged by air, and the charge under pressure, but is introduced only during part of the stroke, into the working cylinder after the flushing and remaining during the Part of the stroke is cooled by adiabatic expansion, characterized in that when the two charging components, gas and air, are fed separately to the inlet of the filling pressure. held high above the atmospheric line and the filling distance at \ #ollast extended so far that the pressure in the cylinder at the end of the adiabatic expansion following the filling is at most a little below atmospheric pressure and thus the pressure at the end of the working cap is still considerably above the atmospheric pressure: lies. 2. Procedure for power control of a machine working in the factory, as a result characterized in that with decreasing load the filling line in the same Height maintained as in full load operation, but the filling distance is shortened.