Supercharged internal combustion engines

Claim 1

In an internal combustion engine comprising variable-volume work chambers each provided with at least one air inlet and at least one exhaust gas outlet, a turbocompressor unit for supercharging the engine and comprising at least one compressor having an air inlet and an air outlet and at least one turbine connected to mechanically drive the compressor and having a gas inlet and a gas outlet, each of said air inlets of the work chambers communicating with the air outlet of the compressor, at least one exhaust gas manifold connected to the gas inlet of the turbine, exhaust gas pipes respectively connecting the exhaust gas outlets to the exhaust gas manifold, a junction being provided between each exhaust gas pipe and the exhaust gas manifold, said engine further comprising a bypass pipe which connects the air outlet of the compressor to the gas inlet of the turbine by bypassing the work chambers, throttling means inserted in the bypass pipe and defining a passage of variable section so adapted as to produce such pressure drop that a resulting pressure difference between the air outlet of the compressor and the gas inlet of the turbine substantially only depends on the value of the pressure prevailing in the air outlet of the compressor; the improvements comprising in combination: a. said work chambers, said exhaust gas outlets, said exhaust gas pipes and said exhaust gas manifold being constructed and arranged to cooperate, with respect to exhaust gas flow orientation and velocity in said manifold, with the cross-sectional area of said exhaust gas manifold, which is a substantially constant section and sufficiently small such that, at any rated running speed of and load on the engine, the velocity of the flow of the gases in the manifold, directly downstream of the last junction between the exhaust pipes and the manifold, relative to the direction of flow of the gases in the manifold, is equal to at least the Mach number 0.3; b. the junction between the bypass pipe and the gas inlet of the turbine is located downstream of the throttling means and upstream of the first junction between said manifold with said exhaust pipes, relative to the direction of flow of the gases coming from the work chambers and traveling through the exhaust gas manifold toward the turbine inlet; c. said throttling means are so adapted that the sum of forces due to a pressure drop which they produce and which is applied to said throttling means, is compensated by a balancing force such that the resultant of these forces is substantially nil; and d a control means operably connected to said throttling means and including pressure sensing means operably coupled to said compressor outlet and said turbine inlet for directly sensing the pressure prevailing at said outlet and inlet such that said control means is responsive to a first parameter of operation of the engine related in a bi-univocal manner to the total pressure prevailing directly in the outlet of the compressor and to a second parameter of operation of the engine related in a bi-univocal manner to the total pressure prevailing directly upstream of the turbine, said control means being so adapted that it tends to close said throttling means when said two total pressures tend to approach each other and reciprocally tends to open said throttling means when said total pressures tend to depart from each other and that the difference between said total pressures substantially depends only on the total pressure prevailing in the outlet of the compressor and varies in the same direction as the last-mentioned total pressure.