Actuating Drive for Steam Turbine Control Valve
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Solution Overview
Problem
Existing actuating drives for steam turbine regulation valves suffer from throttling losses in continuously adjustable valves and require expensive servomotors to maintain precise control, leading to thermally unfavorable operating conditions for the working medium pump.
Innovation Solution
An actuating drive with a working cylinder and external working medium circuit, utilizing an electric asynchronous motor-driven pump, a short-circuit line with a short-circuit valve, and unregulated open/closed valves to bypass the working cylinder, allowing for efficient displacement of the piston rod without throttling losses and avoiding thermally unfavorable states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuously adjustable valves are used for precise control of the piston position, then measurement precision is improved, but throttling losses increase and energy consumption rises
Solution Approach 1:
The control process is segmented into two distinct phases: a first phase using a first valve type (e.g., servo valve) for precise positioning, and a second phase using a second valve type (e.g., on/off valve) for maintaining position. This segmentation allows each valve to operate in its optimal mode, reducing overall energy consumption while maintaining precision.
Solution Approach 2:
The control system periodically switches between different valve operating modes. During the positioning phase, the servo valve is activated for precise control; once positioned, the system transitions to using on/off valves for maintenance of position. This periodic switching reduces throttling losses while preserving measurement precision.
2Measurement precision
If servomotors are used to drive the working medium pump for precise control, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The motor operation is segmented into a first operating state for positioning (using full motor power) and a second operating state for maintaining position (using reduced or zero power). This segmentation allows the use of simpler, less expensive motors while achieving the same control precision through intelligent operation phases.
Solution Approach 2:
The motor operates periodically between high-power positioning mode and low-power maintenance mode. During positioning, the motor provides full control authority; once positioned, the system switches to a maintenance state where the motor consumes minimal energy or remains stationary, reducing overall complexity and cost.
3Reliability
If the working medium pump operates continuously to maintain pressure, then reliability is improved, but thermally unfavorable operating states occur and energy consumption increases
Solution Approach 1:
The pump operates periodically between an active pressurizing state and a standby state. During the active state, the pump builds up pressure in the working medium circuit; during the standby state, the pump remains inactive or operates at minimal capacity. This periodic operation reduces thermal loading and energy consumption while maintaining reliable pressure through pressure holding mechanisms.
Solution Approach 2:
The pump performs preliminary pressurizing action before control operations begin, building up sufficient pressure in advance. Once pressurized, the system can maintain pressure without continuous pump operation, using pressure holding valves and the elasticity of the hydraulic system to sustain pressure during standby periods, thereby avoiding thermal overload.
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 reduces production costs and eliminates thermally unfavorable operating states, enabling precise control with digital signals and utilizing the spring force for position adjustment, thus improving the dynamic actuation characteristic and reducing energy consumption.
Implementation Method 1
counter to the force of a spring, in particular compression spring, which is assigned to the working cylinder
Implementation Method 2
the pressure of the working medium is built up by means of a working medium pump in the external working medium circuit
Implementation Method 3
a check valve which opens in the direction of the first pressure port and thus of the first pressure chamber
Implementation Method 4
a short-circuit line, which short-circuit line connects the pressure line to a suction side of the working medium pump while bypassing the working cylinder
Data Source
AI summary
An actuating drive for a regulation valve has a working cylinder with a piston and a piston rod, which piston rod forms an actuator. The piston delimits a first pressure chamber of the working cylinder. The first pressure chamber has a first pressure port for the introduction of a pressurized working medium for displacing the piston, by exertion of pressure, counter to the force of a spring. An external working medium circuit is connected to the working cylinder for introducing the working medium into or discharging the working medium from, the first pressure chamber. The working medium circuit has a working medium pump. The pump is connected to the first pressure port by a pressure line which is connected to a pressure side of the working medium pump. A check valve or shut-off valve which opens in the direction of the first pressure port is provided in the pressure line.