Two-Stage Zero-Pressure Control Valve for Combustion Gas Stability
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Solution Overview
Problem
Existing combustion systems with gas burners face instability and sensitivity issues due to the small forces acting on the control membrane of gas valves, leading to restricted flow and sensitivity, especially at larger gas flow rates.
Innovation Solution
A two-stage zero-pressure control valve divides pressure control into two stages, using a servo pressure regulator to adjust inlet pressure and a pressure drop valve to achieve stable outlet pressure, along with two-way valves for safety redundancy, ensuring stability and insensitivity across a broader gas flow range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage pressure control valve is used with similar pressures on both sides of the control diaphragm, then the valve structure is simple, but the valve becomes unstable and sensitive with low flow limit
Solution Approach 1:
The pressure control function is divided into two stages: a first pressure control stage that reduces inlet pressure to an intermediate pressure, and a second pressure control stage that reduces the intermediate pressure to the final outlet pressure. This segmentation allows each stage to operate with appropriate pressure differentials, improving stability while maintaining reasonable structural complexity
Solution Approach 2:
The invention changes the pressure parameters in the control system by introducing an intermediate pressure level. The first control diaphragm operates with inlet pressure versus intermediate pressure, while the second control diaphragm operates with intermediate pressure versus outlet pressure. This parameter transformation enables both diaphragms to function within optimal pressure differential ranges, enhancing overall valve stability
2Ease of operation
If the control diaphragm operates with similar pressures on both sides, then the pressure control is straightforward, but the small forces on the diaphragm cause instability and sensitivity
Solution Approach 1:
The control system is segmented into two independent control loops, each with its own control diaphragm. The first control loop manages the inlet to intermediate pressure transition, while the second control loop manages the intermediate to outlet pressure transition. This segmentation allows each control loop to be optimized for its specific pressure differential, improving stability without compromising ease of operation
Solution Approach 2:
The intermediate pressure serves as an intermediary between the inlet and outlet pressures. By introducing this intermediate pressure level through the first pressure control stage, the system avoids the instability associated with operating a single diaphragm at similar pressures on both sides, while still maintaining straightforward pressure control through the two-stage process
3Device complexity
If a single pressure control stage is used, then the device has fewer components, but it cannot maintain stability across larger gas flow rates
Solution Approach 1:
The pressure control functionality is segmented into two distinct stages, each capable of handling specific pressure differential ranges. This allows the valve system to maintain stability across a broader gas flow rate range, as each stage can be optimized for its operating conditions, justifying the additional components
Solution Approach 2:
The invention adds a dimensional aspect to the pressure control by introducing an intermediate pressure level between inlet and outlet. This creates a two-dimensional pressure control architecture rather than a single-stage approach, enabling the system to handle larger gas flow rates while maintaining stability through distributed pressure management
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a stable and robust valve design suitable for larger flow rates, with enhanced stability and reduced sensitivity, allowing for effective operation with reduced overall effort.
Implementation Method 1
In a first stage, the inlet pressure is changed via a servo pressure regulator from an input pressure to a pressure corresponding to the reference pressure plus a pressure component
Implementation Method 2
In the second stage, a pressure drop valve reduces this pressure by the pressure component, thereby obtaining the reference pressure at the outlet
Implementation Method 3
A reference pressure is applied to one side of the diaphragm, and an outlet pressure is applied to the other. The pressures applied to the sides are similar, so only small forces act on the diaphragm
Data Source
Figure 1~2
AI summary
The method involves premixing air and combustion gas, and adjusting outlet pressure (Pout) of the combustion gas equal to a reference pressure (Pref) before admission into a mixing space of a gas valve in two stages by a zero-pressure control valve (5) that is provided with servo pressure regulator valve unit (5a). Input side pressure (Pi) of combustion gas is reduced in one of the stages to a reference pressure (Pref) and a predetermined pressure portion (Px). The pressure is reduced to reference pressure constantly around the pressure portion in another stage. An independent claim is also included for a combustion system with a combustion gas-air-mixing device.