MICRO-PILOT INJECTION IGNITION TYPE GAS ENGINE

• US 20100043744A1
• Filed: 11/20/2008
• Published: 02/25/2010
• Est. Priority Date: 12/14/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Heavy Industries Engine & Turbocharger, Ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Mitsubishi Heavy Industries, Ltd.
• Inventors: Nishio, Hideki, Shimizu, Yuuichi, Suzuki, Hajime
• Granted Patent: US 8,215,284 B2
• Time in Patent Office: Days
• US Class Current: 123/260
• CPC Class Codes: F02B 77/08 Safety, indicating or supervising devices thermal insulation F02B77/11; rendering engines inoperative or idling F02D17/04; dependent on lubricating conditions F01M1/22; dependent on cooling F01P11/14
• CPC Class Codes: F02B 77/085 with sensors measuring combustion processes, e.g. knocking, pressure, ionization, combustion flame
• CPC Class Codes: F02D 19/061 by controlling fuel injectors
• CPC Class Codes: F02D 19/0623 Failure diagnosis or prevention; Safety measures; Testing
• CPC Class Codes: F02D 19/0631 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 19/10 peculiar to compression-ignition engines in which the main fuel is gaseous
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: F02D 41/0025 Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
• CPC Class Codes: F02D 41/0027 the fuel being gaseous non-electrical control F02D19/02
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/06 for engine starting or warming up F02D41/0255 takes precedence
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/1475 Regulating the air fuel ratio at a value other than stoichiometry
• CPC Class Codes: F02D 41/3047 said means being a secondary injection of fuel
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

What is disclosed is a micro-pilot injection ignition type gas engine, whereby an air fuel ratio control in starting the engine is executed with enhanced precision, by means of introducing skip-firing intermittent operations which reflect the engine operation conditions, while an idling time span can be shortened or omitted.

The engine includes: a gas valve that opens and closes a fuel-gas passage in front of each cylinder, so as to arbitrarily control the throat area as well as the opening-closing time span of the gas valve; an engine speed detecting unit to detect the engine speed; a combustion diagnosis unit to detect an engine combustion state through a cylinder pressure distribution along elapsed time, as to each cylinder; an opening-closing control unit as to the gas valve, so as to control the intermittent opening-closing of the gas valve according to the levels of the detected engine speed as well as the cylinder pressure distribution; whereby, in starting the engine, the intermittent opening-closing of the gas-valve enables at least one skip-firing mode that brings an enhanced fuel-supply pressure-pulsation with which a relatively large amount of fuel-gas is supplied per engine cycle with firing so that the air fuel-gas ratio of each cylinder reaches a prescribed target value.

Claims

1. A micro-pilot injection ignition type gas engine that ignites and burns premixed air fuel-gas mixture inducted into each main combustion chamber,

by means of at least one pilot flame that jets out from a pre-chamber to the main chamber through at least one pre-chamber nozzle hole communicating the main chamber to the pre-chamber in which a fuel-oil injector injects micro-pilot fuel oil to produce a pre-chamber combustion gas as a source of the flame jet,

the gas engine comprising:

a gas valve that delivers and cuts a fuel-gas at a position in front of each cylinder, so as to arbitrarily control the throat area as well as an opening-or-closing time span of the gas valve;

an engine speed detecting unit to detect the engine speed;

a cylinder pressure sensor provided at each cylinder so as to continually measure pressure levels as to each cylinder;

a combustion diagnosis unit to monitor the pressure levels so that the diagnosis unit analyzes an engine combustion state through a cylinder pressure distribution along elapsed time, the distribution as to each cylinder being formed in the diagnosis unit;

an opening-closing control unit as to the gas valve, so as to control an intermittent opening-or-closing of the gas valve in response to the engine speed and the pressure distribution;

whereby, in starting the engine, the intermittent opening-or-closing of the gas-valve enables at least one skip-firing mode that brings an enhanced fuel-supply pressure-pulsation with which an increased amount of fuel-gas is supplied per one engine-cycle with firing so that the air fuel-gas ratio of each cylinder reaches a prescribed target value.

2. The micro-pilot injection ignition type gas engine according to the claim 1, whereby the opening-closing control unit as to the gas valve makes the gas valve for each cylinder open and close, intermittently per each cylinder in turn according to a firing sequence of the engine, so that the air fuel-gas ratio reaches the prescribed target value,

with the at-least-one skip-firing mode, and

with a series of time spans as to the variable valve-opening-time span of the gas valve, the time spans being changed step by step.

3. The micro-pilot injection ignition type gas engine according to the claim 1, whereby the opening-closing control unit makes the gas valve for each cylinder open and close with a first skip-firing mode of a lower valve-opening-ratio in the case when the cylinder pressure distribution along elapsed time the distribution which is analyzed by the combustion diagnosis unit corresponds to a prescribed target distribution, whereas the opening-closing control unit makes the gas valve open and close with a second skip-firing mode of a higher valve-opening-ratio in the case when the cylinder pressure distribution along elapsed time does not reach the prescribed target distribution.