Methanol fueled turbocharged diesel cycle internal combustion engine

The combination of an intake air supply system with an internal combustion engine having a charge air cooler, a cylinder charging air intake and an exhaust discharge, the intake air supply system including:

• an engine driven positive displacement blower having inlet and outlet means and an exhaust gas driven turbo-compressor connected in series whereby the compressor discharges to the blower inlet and the blower outlet discharges to the charge air cooler and to the engine air intake;
• a bypass passage connecting the blower inlet and outlet;
• control means including an electronic control module for calculating a required flow area of said bypass passage in response to continually sensed engine operating parameters including engine speed, boost air pressure at the turbo-compressor outlet and operator demand;
• valve means in the bypass passage to control the flow of fluid through the bypass;
• said valve means being operative to modulate said flow area as calculated from a fully open position to a fully closed position of said bypass passage thereby infinitely varying the flow area between the fully open and fully closed positions of said valve means;
• and
• said valve means being modulated to operatively maintain said bypass passage at least partially open at engine idle, whereby said valve means permits bypass flow, either (a) to recirculate air flow from the blower outlet to the inlet to reduce or limit the engine power absorbed by the blower or (b) to conduct additional air flow around the blower directly from the turbo-compressor to the engine intake to avoid the restriction of the blower to increased charging air flow, thereby providing a dual function capability in a single valve means.