DD289806A5 - GAS - AIR RATIO CONTROL FOR GAS FIRES - Google Patents

Abstract

Gas-air ratio control for gas firing. The invention is applicable to all gas fires, where gas and air flow must necessarily be controlled by actuators with electric actuator. The problem is that the non-linear characteristic actuators can not be combined into one loop by conventional linear information processing systems. The problem is solved by this invention by the non-linear driving curve of the gas firing in the entire load range at constant gas-air ratio by trial and determined and programmed into the operation unit of the VEB MEW Magdeburg. Input signals of the operation unit are the unit current signals of the position remote displays of the gas and air actuator. The output signal of the operation unit controls the throttle position device via a three-position controller. Leadership is the manual control command for the air actuator. This closes the control loop. In the event of deviations from the permissible gas / air ratio, this is signaled by the operating unit, as a result of which a fault shutdown of the burner takes place. By this invention, the requirements of TGL 30322 "gas firing" point * are met. {Gas-air ratio control; gas furnaces; Gas and air volume flow; Actuators; Actuator; Information processing systems; Control loop; Travel curve; Operation unit; Input signals; Standard current signals; Output signal; Three-point controller}

Description

For this 1 sheet drawing

Field of application of the invention The invention is applicable to all gas firing, where the gas and air flow is controlled separately and there is no

linear relationship between the characteristics of both actuators. In addition, the Siellzeiten are both

Actuators often different. In case of deviation from the specified gas-air ratio, the lockout of the Gas burner. This fulfills the requirements of TGL 30322/01 "Gas firing" where, in point 2.3.1.2., It says: "Combustion air and Fuel gas must have a nominal power> 14OkW in inevitable mutual! Dependence controlled or regulated

become.

In deviations vent permissible fuel gas to air ratio of a gas firing, the gas supply must be interrupted automatically

This requirement is not good for the startup process. Compliance with the fuel gas / air ratio must be monitored. "

The fulfillment of these requirements is kept under control by the State Technical Inspectorate (SATü). Characteristic of the known state of the art The compulsory interdependence of the gas-air ratio obstruction is currently realized as follows: The mechanical control via cam or belt or linkage. This is only possible if the actuators in

Favorable relation to each other and the mechanical position can be detected. This type of control is preferably applied to industrial block burners.

The load control with separate, electrically confirmed actuators in 2 Laststu fen with mutual locking. The load is carried out according to the principle of air before gas and in the discharge gas before air. This driving style in only 2 load levels is not sufficient in many cases. A finer gradation, d. H. a quasistetiger operation, is out

control-technical reasons with reasonable effort not possible.

With the known means is a steady load throughout the load range with separately arranged electrically confirmed Actuators for gas and air not possible. Object of the invention

The aim of the invention is to equip such gas burner systems with a forced gas-air ratio control, in which there were no solutions to date in the current state of the art. In particular, the following advantages result: The operation of gas firing is possible with this solution in the first place. SATü does not approve the operation until the requirements of TGL 30322 have been met. This is especially true for new buildings, reconstructions and Gasartenumstellungen.

Explanation of the essence of the invention

The invention has as its object to regulate the gas and air quantity for a gas burner with separately arranged, electrically driven actuators so that a constant gas-air ratio is maintained throughout the load range. If the permissible gas / air ratio is exceeded or not reached, the burner must be shut down. With linear regulators, this task can not be solved because the characteristic curves of the actuators and other system-specific factors have a non-linear character, and the actuation times of the actuators are different.

According to the invention, the object is achieved by constructing and integrating with a programmable operation unit as the core of a gas-air ratio control.

The ratio must be programmed in the working memory of the operating unit. This non-linear ratio must first be determined experimentally in the entire load range during operation at low operating temperatures and corresponds to the travel curve. In accordance with the programmed values, the operating unit supplies a specific output current which corresponds to the predetermined constant gas-air ratio. Thus, the relationship between the non-linear ratio and its absolute size of the input currents and the associated output current is established via the memory values.

It also belongs to the invention that between the analog output of the operating unit and the servo motor, a three-step controller (16) is interposed, which controls the servo motor (3) of the gas control valve (2), since the analog output of Operatipnseinheit can not be used directly to control the servo motor , This controller determines the system-specific characteristics of the control loop.

As a reference variable in the control loop is the position of the servomotor (5) of the air throttle valve (4), which is selected by means of the manual control (7). By means of the manual-automatic changeover switch (8) and the manual control for the gas control valve (6), the change to manual is possible. At 2 optocoupler outputs of the operating unit (13) relays (14 and 15) are directly connected. These two optocoupler outputs are assigned to the analogue output in such a way that the respective relay is activated by means of parameter setting on the operating unit when the permissible gas / air ratio is exceeded or not reached.

The relay contacts are integrated into the burner control system in such a way that after the start-up process a fault shutdown occurs in the event of a deviation.

embodiment

The drawing shows how the gas burner (1) by means of the equipment used a constant gas-air ratio is supplied. It is a prerequisite that prevail constant pressures before the actuators. For variable temperatures, a pre-pressure correction must be carried out.

The 2 media are determined in their volume flow through the gas control valve (2) and the air throttle valve (4). Both are moved by electric actuators with resistance telemeter (3 and 5). The current positions are converted by means of the transmitters (9 and 11} into unit currents, which are given via the ammeters for the position remote displays (9 and 11) to the two inputs of the operating unit (13).

The mathematical formulation of the gas-air travel curve for various gas-air ratios is programmed in the memories of the operation unit 13. The output current is proportional to the gas-air ratio and represents the input value for the three-position controller 16 In this three-step controller, the control deviation is formed so that in case of deviations from the predetermined gas-air ratio, a control signal to the drive of the gas control valve (3).

A's reference variable in the control loop is the position of the drive of the air throttle valve (5), which is specified by means of the manual control (7).

By means of the manual-automatic-Umschaltors (8), the control circuit can be separated and the drive of the gas control valve (3) with the manual control (6) to be moved. At the operation unit (13), the gas-air ratio is displayed as a lambda value digital. At 2 binary outputs of the operating unit (13) relays (14 and 15) are connected, which switch when exceeding or falling below a specified gas-air ratio and interrupt the gas supply. The switching points are set with the parameter potentiometer assigned to the respective binary output. Thus, this embodiment is described. While maintaining the principle of action, the following modifications can be made:

The provision of the unit current signals is also possible by pressure transmitter for gas and air pressure in front of the gas burner (1).

Reference variable for the control loop can also be the output signal of a temperature or load control of the downstream heat generation system.

According to the manufacturer, in 1990 an operating unit is available as an unsteady controller. Then eliminates the three-point controller (16).

Claims (3)

1. Gas-air ratio control for gas firing, where the gas and air flow is controlled separately and there is no linear relationship between the characteristics of both actuators, characterized in that with a programmable operation unit, connected directly to the relay at two optocoupler outputs are and between the analog output of the operating unit to the servomotor a three-point controller interposed wicd, as the core of a gas-air ratio control is built and integrated. 2. Gas-air ratio control for gas firing according to claim 1, characterized in that these two optocoupler outputs are assigned to the analog output so that by means of parameter setting on the operation unit in case of exceeding or falling below the allowable gas-air ratio, a control of Relay takes place. 3. Gas-air ratio control for gas firing according to claim 1, characterized in that the relay contacts are so integrated into the burner control, that after the supply process, a fault shutdown occurs in case of deviation.