Method for determining air mass in a crankcase scavenged two-stroke engine
First Claim
1. In a crankcase scavenged two-stroke engine characterized by an operating cycle including portions during which air is inducted into a crankcase chamber, is thereafter trapped and compressed within the shrinking volume of the crankcase chamber, and is then transferred to a combustion chamber;
- a method for determining the mass of air transferred to the combustion chamber during the engine cycle, comprising the steps of;
deriving indications of the pressure P, volume V, and temperature T, of air within the crankcase chamber during the engine operating cycle;
determining the mass of air MT trapped in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle when air is trapped and compressed within the crankcase;
determining the residual mass of air MR remaining in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle after the transfer of air to the combustion chamber is substantially completed; and
estimating the mass of air M transferred to the combustion by chamber as a function of the difference between the mass of air MT trapped within the crankcase chamber and the mass of air MR remaining within the crankcase chamber.
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Accused Products
Abstract
A method is described for determining the cylinder mass of air available for combustion in a crankcase scavenged, two-cycle engine, based upon the Ideal Gas Law relationship and indications of pressure, volume, and temperature of air in the crankcase chamber, at predetermined points in the engine operating cycle. This is achieved by first determining the mass of air trapped and compressed in a crankcase chamber, and thereafter, determining the residual air mass remaining in the crankcase after the transfer of air to the associated combustion chamber. Then, the actual air mass transferred to the combustion chamber is determined as a function of the difference between the trapped and residual air masses. Engine trapping efficiency can be used to correct for air leakage from the combustion chamber prior to cylinder exhaust port closure. The volume of the air within the crankcase chamber is derived as a function of engine cycle position, with crankcase air temperature being derived as a function of intake air temperature. Air pressure in the crankcase is monitored with a pressure transducer.
124 Citations
14 Claims
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1. In a crankcase scavenged two-stroke engine characterized by an operating cycle including portions during which air is inducted into a crankcase chamber, is thereafter trapped and compressed within the shrinking volume of the crankcase chamber, and is then transferred to a combustion chamber;
- a method for determining the mass of air transferred to the combustion chamber during the engine cycle, comprising the steps of;
deriving indications of the pressure P, volume V, and temperature T, of air within the crankcase chamber during the engine operating cycle; determining the mass of air MT trapped in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle when air is trapped and compressed within the crankcase; determining the residual mass of air MR remaining in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle after the transfer of air to the combustion chamber is substantially completed; and estimating the mass of air M transferred to the combustion by chamber as a function of the difference between the mass of air MT trapped within the crankcase chamber and the mass of air MR remaining within the crankcase chamber. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- a method for determining the mass of air transferred to the combustion chamber during the engine cycle, comprising the steps of;
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8. In a crankcase scavenged two-stroke engine characterized by an operating cycle including portions during which air is inducted into a crankcase chamber, is thereafter trapped and compressed within the shrinking volume of the crankcase chamber, and is then transferred to and trapped in a combustion chamber;
- a method for determining the mass of air trapped in the combustion chamber during the engine cycle, comprising the steps of;
deriving indications of the pressure P, volume V, and temperature T, of air within the crankcase chamber during the engine operating cycle; determining the mass of air MT trapped in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle when air is trapped and compressed within the crankcase; determining the residual mass of air MR remaining in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle after the transfer of air to the combustion chamber is substantially completed; estimating the mass of air M transferred to the combustion by chamber as a function of the difference between the mass of air MT trapped within the crankcase chamber and the mass of air MR remaining within the crankcase chamber; determining a trapping efficiency value representing the percentage of the transferred mass of air M, which is trapped in the combustion chamber; and adjusting the transferred mass of air M in accord with the determined trapping efficiency value to provide a measure of the air mass trapped in the combustion chamber. - View Dependent Claims (9, 10, 11, 12, 13, 14)
- a method for determining the mass of air trapped in the combustion chamber during the engine cycle, comprising the steps of;
Specification