Method and device for controlling starting of gas engine

• US 20090071438A1
• Filed: 08/28/2008
• Published: 03/19/2009
• Est. Priority Date: 08/30/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Heavy Industries Engine & Turbocharger, Ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Mitsubishi Heavy Industries, Ltd.
• Inventors: Sakai, Kei, Shiraishi, Masataka, Kakuhama, Yoshitaka, Kitamura, Yosuke
• Granted Patent: US 7,654,247 B2
• Time in Patent Office: Days
• US Class Current: 123/403
• CPC Class Codes: F02B 2275/14 Direct injection into combustion chamber
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02D 19/022 to adjust the fuel pressure, temperature or composition
• CPC Class Codes: F02D 19/024 by controlling fuel injectors
• CPC Class Codes: F02D 19/027 Determining the fuel pressure, temperature or volume flow, the fuel tank fill level or a valve position
• CPC Class Codes: F02D 31/002 controlling air supply
• CPC Class Codes: F02D 41/0007 for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• CPC Class Codes: F02D 41/0027 the fuel being gaseous non-electrical control F02D19/02
• CPC Class Codes: F02D 41/06 for engine starting or warming up F02D41/0255 takes precedence
• CPC Class Codes: F02M 21/0236 Multi-way valves; Multiple valves forming a multi-way valve system
• CPC Class Codes: F02M 21/0275 for in-cylinder direct injection, e.g. injector combined with spark plug
• CPC Class Codes: F02M 21/0284 Arrangement of multiple injectors or fuel-air mixers per combustion chamber
• CPC Class Codes: F02M 21/047 Venturi mixer
• CPC Class Codes: F02N 2300/102 Control of the starter motor speed; Control of the engine speed during cranking
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A method and device for controlling starting of a gas engine is proposed which is superior in starting performance and improved in load responsivity while maintaining air fuel ratio control.

There are provided a starting operation mode in which fuel gas flow is controlled by the fuel gas flow control valve based on actual mixture flow rate and adequate excess air ratio prescribed for each of detected values of operating conditions of the engine and then mixture flow is controlled by the throttle valve so that engine rotation speed approaches a target rotation speed, and a normal operation mode in which fuel gas flow is controlled by the fuel gas flow control valve so that engine rotation speed approaches the target rotation speed and then mixture flow rate is controlled by the throttle valve so that air fuel ratio of the mixture coincides with an adequate value prescribed for each of detected values of operating conditions of the gas engine with the fuel gas flow flowing at the commanded fuel gas flow rate, and a switchover rotation speed is predetermined so that operation mode is switched from starting mode to normal mode when engine speed reaches the switchover rotation speed.

Claims

1. A method of controlling starting of a gas engine in which

fuel gas is introduced via a fuel gas flow control valve to a charging air supply pipe to be mixed with the air and the mixture is controlled in its flow rate by a throttle valve and supplied to combustion chambers of the engine, wherein are provided

a starting operation mode in which fuel gas flow is controlled by the fuel gas flow control valve based on actual mixture flow rate and adequate excess air ratio prescribed for each of detected values of operating conditions of the engine and then mixture flow is controlled by the throttle valve so that engine rotation speed approaches a target rotation speed, and

a normal operation mode in which fuel gas flow is controlled by the fuel gas flow control valve so that engine rotation speed approaches the target rotation speed and then mixture flow rate is controlled by the throttle valve so that air fuel ratio of the mixture coincides with an adequate value prescribed for each of detected values of operating conditions of the gas engine with the fuel gas flow flowing at a commanded fuel gas flow rate,

wherein a switchover rotation speed is predetermined which is a threshold value of engine rotation speed for the engine to be able to run self-reliably, and

wherein the engine is controlled in the starting operation mode during engine rotation speed of from a prescribed initial rotation speed to a prescribed switchover rotation speed, and when the rotation speed rises to equal to or exceeds the prescribed switchover rotation speed, the control is switched to the normal operation mode.

2. A method of controlling starting of a gas engine according to claim 1, wherein the normal operation mode comprises

a speed control process for controlling engine rotation speed by calculating a command value of fuel gas flow rate based on deviation of a detected engine rotation speed from a target command value of engine rotation speed and controlling fuel gas flow rate flowing through the fuel gas flow control valve to coincide with the calculated command value of fuel gas flow rate, and

an air fuel ratio control process for controlling air fuel ratio of fuel-air mixture supplied to the combustion chamber of the engine through performing feedback control in which such a command value of fuel-air mixture flow rate is calculated that air fuel ratio of the mixture coincides with an adequate value prescribed for each of detected values of operating conditions of the gas engine with the fuel gas flow flowing at the commanded fuel gas flow rate and a target opening of the throttle valve is determined based on deviation of the actual mixture flow rate calculated based on detected values of operating conditions of the gas engine from the calculated command value of fuel-air mixture flow rate.

3. A method of controlling starting of a gas engine according to claim 1, wherein capacity correction is performed when calculating mixture flow rate as actual mixture flow rate at the initial stage of starting operation, the capacity correction being such that content volume of an intake manifold of the engine is added to the total piston swept volume of the engine.

4. A method of controlling starting of a gas engine according to claim 3, wherein the capacity correction processing is finished when a prescribed time period of correction continuation has elapsed or engine rotation speed has reached a prescribed rotation speed.

8. A method of controlling starting of a gas engine according to claim 2, wherein capacity correction is performed when calculating mixture flow rate as actual mixture flow rate at the initial stage of starting operation, the capacity correction being such that content volume of an intake manifold of the engine is added to the total piston swept volume of the engine.

5. A starting control device for controlling starting of a gas engine in which fuel gas is introduced via a fuel gas flow control valve to a charging air supply pipe to be mixed with the air and the mixture is controlled in its flow rate by a throttle valve and supplied to combustion chambers of the engine, the engine being equipped with a rotation speed sensor for detecting engine rotation speed, an inlet pressure sensor for detecting mixture inlet pressure, an inlet temperature sensor for detecting mixture inlet temperature, and an engine control device for controlling engine operation in accordance with detected values of operating conditions of the engine, wherein the engine control device has a means to allow the fuel gas flow control valve to control fuel gas flow rate based on actual mixture flow rate detected engine rotation speed, inlet manifold pressure, and inlet manifold temperature and based on an adequate value of excess air ratio prescribed for each of detected values of operating conditions of the gas engine and a means to allow the throttle valve to control mixture flow rate so that engine rotation speed approaches a prescribed target rotation speed, thereby enabling the control device to perform engine operation in a starting operation mode, and

a means to allow the fuel gas flow control valve to control fuel gas flow rate so that engine rotation speed approaches a prescribed target rotation speed and a means to allow the throttle valve to control mixture flow rate so that excess air ratio of the mixture coincides with an adequate value prescribed for each of detected values of operating conditions of the gas engine with the fuel gas flow flowing at the controlled fuel gas flow rate, thereby enabling the control device to perform engine operation in a normal operation mode,

wherein a switching means for switching over operation mode from one mode to the other mode is provided, and

wherein a switchover rotation speed is predetermined which is a threshold value of engine rotation speed at which the engine can run self-reliantly,

whereby the engine is controlled in the starting operation mode during engine rotation speed of from a prescribed initial rotation speed to a prescribed switchover rotation speed, and when the rotation speed rises to equal to or exceeds the prescribed switchover rotation speed, the control is switched to the normal operation mode.

6. A starting control device for controlling starting of a gas engine according to claim 5, wherein the engine control device comprises

a speed control section for controlling engine rotation speed by calculating a command value of fuel gas flow rate based on deviation of a detected engine rotation speed from a target command value of engine rotation speed and controlling fuel gas flow rate flowing through the fuel gas flow control valve to coincide with the calculated command value of fuel gas flow rate, and

an air fuel ratio control section for controlling air fuel ratio of fuel-air mixture supplied to the combustion chamber of the engine through performing feedback control in which such a command value of fuel-air mixture flow rate is calculated that air fuel ratio of the mixture coincides with an adequate value prescribed for each of detected values of operating conditions of the gas engine with the fuel gas flow flowing at a commanded fuel gas flow rate and a target opening of the throttle valve is determined based on deviation of the actual mixture flow rate calculated based on detected values of operating conditions of the gas engine from the calculated command value of fuel-air mixture flow rate.

7. A starting control device for controlling starting of a gas engine according to claim 5, wherein a capacity correction means is provided which performs such a capacity correction that content volume of an intake manifold of the engine is added to the total piston swept volume of the engine when calculating mixture flow rate as actual mixture flow rate at the initial stage of starting operation, whereby the capacity correction processing is finished when a prescribed time period of correction continuation has elapsed or engine rotation speed has reached a prescribed rotation speed.

9. A starting control device for controlling starting of a gas engine according to claim 6, wherein a capacity correction means is provided which performs such a capacity correction that content volume of an intake manifold of the engine is added to the total piston swept volume of the engine when calculating mixture flow rate as actual mixture flow rate at the initial stage of starting operation, whereby the capacity correction processing is finished when a prescribed time period of correction continuation has elapsed or engine rotation speed has reached a prescribed rotation speed.