Showing papers on "Lean burn published in 1987"

Air/fuel ratio controller for engine

Abstract: Disclosed herein is an air/fuel ratio controller for an engine, which is equipped with a function to make the air/fuel ratio leaner in a light-load operation zone or the like of a lean burn engine. The controller is intended to improve the starting performance and acceleration feeling of the engine significantly. Upon generation of an acceleration command by a driver during lean burn of the engine at a lean air/fuel ratio, an air/fuel ratio enriching device is operated to set the air/fuel ratio of an air-fuel mixture, which is to be fed to the engine, at a level richer than the lean air/fuel ratio while an actually accelerated state continues in the engine from the time point of generation of the acceleration command.

Operational Characteristics of a Lean Burn Sl-Engine: Comparison Between Plasma-Jet and Conventional Ignition System

Abstract: Besides the specific demands on mixture formation the main problem of lean-mixture SI engines is to assure the ignition of the air-fuel mixture even if very lean and at all operational conditions. In the scope of extensive research work an analysis was made of the operational behavior of a 4-stroke SI-engine with a newly developed plasma-jet ignition and a conventional transistorized ignition system, respectively. The investigations on the engine were completed by tests in a combustion chamber with methane-air mixture. With plasma-jet ignition the combustion delay and the combustion duration are clearly shorter. The engine tests also revealed a clearly extended lean misfire limit and a reduction of cyclic variations. The NO/sub x/-emissions are only slightly higher than with the transistorized ignition system although a considerable improvement of the brake efficiency can be obtained.

Feasibility evaluation of reformed methanol usage to spark ignition engine

Abstract: To improve the cold starting and low load driveability problem in a methanol fueled car, a reformed methanol fueled si engine with a small methanol reformer using exhaust thermal energy as a heat source was developed and tested. Half of the methanol supplied to the engine was reformed to hydrogen and carbon monoxide, and the rest was supplied in a liquid state. As a result, this engine produces less power than the neat methanol fueled engine. But brake specific fuel consumption of this engine is lower based on the calorific value than that of the neat methanol fueled engine in the wide range of excess air ratio. The co emission levels are not significantly different, whereas the hc emission levels are lower than those from the neat methanol fueled engine. The nox emission levels are higher than those from the neat methanol fueled engine but this problem can be solved by lean burn (a).

Air-fuel ratio controller for engine

Abstract: PURPOSE:To make a stabilized combustion state maintainable, by controlling the combustion state with a richer air-fuel ratio then an intrinsic desired lean air-fuel ratio in a transient manner, within the specified period when a water temperature variation is predicted even if an engine driving state shifts to hotness CONSTITUTION:After engine starting, the cooling water temperature detected by a thermistor 11 is more than the setting value, that is, whether warm-up is all over or not is judged at a central processing unit 19, and when NO is the case, rich driving takes place, and at that point that it comes to YES, lean burn (lean air-fuel ratio) driving takes place At the time of transition of this lean burn driving, first a water temperature variation per unit time is calculated, and when the value is smaller than 0 and larger than the specified value approximate to the zero, a fuel injection quantity commensurate to cooling water temperature at that time is calculated And, fuel in a quantity setting an intermediate air-fuel ratio being richer in the specified quantity than an intrinsic desired lean air-fuel ratio is made so as to be sprayed out of an injector 10

Engine Control System for Lean Combustion

Abstract: In order to achieve a lean burn engine control system, it is necessary to develop high accuracy air fuel ratio control technology including transient driving conditions and lean burn limit expansion technology. This paper describes the following: (1) the characteristics of the transient response of the fuel supply are clarified when various kinds of air flow measuring methods and fuel injection methods are used. (2) To achieve stable combustion in a lean mixture, a fine fuel droplet mixture, whose diameter is less than 40 micron, needs to be supplied (a).

Fuel Economy and Emissions of a Toyota T-LCS-M Methanol Prototype Vehicle

Abstract: The Toyota lean combustion system-methanol (T-LCS-M) is a lean burn methanol combustion system designed to maximize fuel economy and driving performance while minimizing pollutant emissions. Testing at the EPA Motor Vehicle Emissions Laboratory (MVEL) indicates that this system allows relatively low emissions of regulated pollutants and aldehydes when operated on either M100 or M85 methanol fuels under transient driving and evaporative emissions test conditions. Total vehicle hydrocarbon emissions appear lower when the vehicle is operated on M100 rather than M85 fuel. Fuel economy is slightly improved when the system is operated on M85 rather than M100 fuel.

Air fuel ratio controller of lean burn engine

Abstract: PURPOSE:To prevent hunting by calculating the primary lag in an air fuel ratio feedback control system provided with a lean sensor according to the operating state and processing primary lag characteristic to an air fuel ratio set value in order to be made to be the aimed value. CONSTITUTION:An air fuel ratio set value calculating means 11 reads out set values of air fuel ratio corresponding to respective operating states on the basis of intake air flow (a) and of engine speed N, and a factor calculating means 12 calculates a fuel amount conversion factor KAF for correction is order to obtain set air fuel ratio, and correction factors COEF for warming increase, intake temperature correction and the like. A feedback control correction factor KFB is calculated from a KFB calculating means 16 according to deviation between the aimed value of air fuel ratio calculated from an arithmometor 15 and an air fuel ratio signal from a lean sensor 5. A response lag time constant calculating means 17 makes response time lag of a feedback control system according to the operating state to approximate as the primary lag, and a primary lag processing means 18 weighs and averages the set value from the air fuel ratio set value calculating means 11 according to the response lag time constant, so that the aimed value is to be output.

Air-fuel ratio control device for lean burn engine

Abstract: PURPOSE:To prevent the generation of hunting by temporarily stopping feedback when the set value of air-fuel ratio has changed in accordance with an operating condition and making this stopping time the response delay time of a feedback system including a lean sensor. CONSTITUTION:An air-fuel ratio set value calculating means 11 receives the signals of the engine speed N of an engine 1, air quantity Q, etc. and outputs the set value of air-fuel ratio. A coefficient calculating means 12 calculates a coefficient for converting to a desired fuel injection quantity and correction coefficients for correcting warming-up increasing quantity, intake air, etc. On the other hand, the thickness of exhaust gas from the engine 1 is detected by a lean sensor 5, and its air-fuel ratio signal is compared with a target value by an adding operator and, based on the deviation, a means 16 calculates a feedback correction coefficient KFB. In this case, when the set value of this air-fuel ratio has suddenly changed, this is detected by a feedback stopping timer 17, the coefficient KFB is clamped to the value before it is changed, and the feedback control is stopped for a certain period of time.