Method and device for controlling natural gas electrospray of high-power diesel engine

Abstract

The invention relates to a device for controlling natural gas fuel electrospray of the high-power diesel engine. The device comprises a single-chip microcomputer, a digital quantity command input circuit, a general analog quantity input circuit, a fuel supplying rack position detecting analog quantity input circuit, a rotation speed and phase detecting circuit and an electromagnetic valve driving circuit. A method for controlling natural gas fuel electrospray of the high-power diesel engine includes setting relevant MAPMAP digit groups reflecting various corresponding relations, detecting target and practical parameter values in real time, inquiring the relevant MAPMAP digit groups, obtaining starting time point of real-time gas supply time windows and length, and sequentially controlling on and off of a gas supply electromagnetic valve. Variations of gas inflow requirements caused by variations of fuel gas properties as well as gas inflow requirements caused by fluctuation of rotation speed and load variations of the diesel engine can be responded in real time. An electrospray control system can accurately detect and determine phase angle information of the diesel engine and can accurately determine gas inlet time and window period of each cylinder.

Description

technical field [0001] The invention belongs to the technical field of diesel engines, and in particular relates to a method and device for controlling natural gas electric injection of high-power diesel engines. Background technique [0002] High-power diesel engines (single engine power above 1MW) generally use liquid fuels with high calorific value such as light diesel and heavy diesel. The use of cleaner and more environmentally friendly natural gas as the main fuel for megawatt-class high-power diesel engines is currently in the experimental stage. Such diesel engines generally require two sets of fuel supply systems: diesel fuel system and natural gas fuel system. Because the calorific value of natural gas is low, low speed or cold machine is difficult to effectively compress and ignite to do work, so diesel is generally used to start. After reaching the rated or higher speed and the machine is relatively hot, start to gradually inject natural gas and reduce diesel sup...

AI Technical Summary

Problems solved by technology

[0004] The high-power diesel engine is upgraded to use natural gas as the main fuel. Its control and detection are quite different from those of diesel engines that only use diesel as fuel. Because the calorific value of natural gas fuel is much lower than that of diesel, so the gas pressure and shut-off flow will do work on the gas combustion. The impact is very direct and obvious, and very small changes in pressure and cut-off flow will be reflected in work; what's more, the pressure and cut-off flow fluctuations of the gas itself are very random and unstable, so it is very difficult to control the intake air to stabilize the operation of the diesel engine.

When the load of the diesel engine changes, it is very tricky and complicated to control the diesel engine by increasing or decreasing the gas intake in time according to the instantaneous fluctuation of the diesel engine speed.

[0005] The biggest disadvantage of the existing schemes that use manual or semi-automatic control of the natural gas intake valve to control the natural gas intake volume is that the response is relatively slow, and it is difficult to adjust the intake air in real time according to the real-time fluctuations of diesel engine speed fluctuations, natural gas pressure, and shut-off flow. Therefore, even under the condition of constant load, due to the turbulence of the gas flow itself, the diesel engine with this scheme to control the intake of natural gas often has a large power output fluctuation, and there will be a large power fluctuation amplitude

In the case of load alternation, it is almost impossible to effectively control and restore stable diesel engine operation with this method

Moreover, the number of solenoid valves that can be controlled by the manual or semi-automatic natural gas intake scheme cannot be very large, so the intake point can only be selected at the intake manifold of the diesel engine, and the gas entering the intake manifold of the diesel engine can be controlled by controlling the opening or number of the intake valves. The amount of intake air enters each cylinder for combustion one by one through the diesel engine's own mechanical intake program.

However, the disadvantage of this solution is that due to the low gas density, the pressure near the inlet end where the gas enters the intake manifold is relatively high, and the gas density is relatively high. relatively low density

This results in uneven distribution of gas density and pressure at various points in the intake manifold of the diesel engine, so that the combustion of the gas entering each cylinder is inconsistent and uneven. The reflected phenomenon is that the combustion of each cylinder is inconsistent and the exhaust temperature varies greatly.

In addition, manual or semi-automatic control schemes are extremely intensive for on-site operators. Operators must maintain a high degree of concentration at all times, comprehensively observe diesel engine parameters and gas-related parameters, and fine-tune gas intake at any time to ensure the normal operation of the diesel engine.

If dozens or even hundreds of hours of continuous unit performance tests are performed, multiple operators must take turns to work, and the error rate will greatly increase

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