Pressure boosted IC engine with exhaust gas recirculation

1. A method of operating an internal combustion engine, said engine comprising a turbocharger having a linked turbine impeller/compressor and an exhaust gas turbine impeller bypass, an exhaust gas recirculation (EGR) system, and a combined turbine impeller and EGR control valve, said method comprising the steps of:

i) providing via the control valve exhaust gas from the engine in order to drive the turbine impeller and power the compressor;

ii) using the compressor to compress inlet air supplied to the engine;

iii) using the control valve to divert exhaust gas from reaching the turbine impeller;

iv) using the control valve to recirculate a portion of exhaust gas produced by the engine via the EGR system; and

v) using the control valve to control the amount of the exhaust gas diverted and recirculated by the EGR system, and hence the amount of exhaust gas reaching the turbine impeller.

2. The method of claim 1 wherein the diverted exhaust gas is diverted to the bypass.

3. A compressor and exhaust gas recirculation (EGR) apparatus for an internal combustion engine (ICE) having one or more combustion chambers, said apparatus comprising a turbine impeller, an exhaust gas inlet leading to the turbine impeller for providing exhaust gas from the one or more combustion chambers of the ICE to drive the turbine impeller, an exhaust gas outlet for venting exhaust gas from the turbine impeller, a compressor arranged to be driven by the turbine impeller, and air inlet for supplying inlet air to the compressor, a compressed air outlet leading from the compressor for providing compressed air to the one or more combustion chambers of the ICE, an exhaust gas bypass passage for controlling the amount of exhaust gas used to drive the turbine impeller, an EGR passage for recirculating exhaust gas from the exhaust gas inlet to the compressed air outlet, and a combined turbine impeller and EGR control valve arranged to receive exhaust gas from the exhaust gas inlet and to control the relative proportions of the exhaust gas flowing to the compressed air outlet via the EGR passage, to the exhaust gas outlet via the exhaust gas bypass passage and through the turbine impeller.

4. The compressor and EGR apparatus as claimed in claim 1 , further comprising a common housing surrounding the turbine impeller, compressor and control valve.

5. The compressor and EGR apparatus as claimed in claim 1 , in which the control valve, exhaust gas bypass passage and EGR passage are integrated within a unitary apparatus.

6. The compressor and EGR apparatus as claimed in claim 1 , in which the EGR passage is arranged to recirculate un-cooled exhaust gas from the exhaust gas inlet to the compressed air outlet and the compressor is arranged to provide un-cooled compressed air to the compressed air outlet.

7. The compressor and EGR apparatus as claimed in claim 1 in which the control valve is configured to prevent exhaust gas from being recirculated whenever exhaust gas is allowed to bypass the turbine impeller.

8. The compressor and EGR apparatus as claimed in claim 1 , in which the control valve is configured to prevent exhaust gas from bypassing the turbine impeller whenever exhaust gas is being recirculated.

9. The compressor and EGR apparatus as claim in claim 1 , in which the control valve is configured to control the proportion of exhaust gas being recirculated when exhaust gas bypasses the turbine impeller.

10. The compressor and EGR apparatus as claimed in claim 1 , in which the control valve is a rotary valve.

11. The internal combustion engine as claimed in claim 10 , further comprising a combined intercooler for cooling a mixture of compressed air and recirculated exhaust gas.

12. An internal combustion engine, comprising one or more combustion chambers, an engine air inlet passage leading to the one or more combustion chambers, an engine exhaust outlet passage leading from the one or more combustion chambers, a turbocharger with a turbine impeller arranged to be driven by exhaust gas from the engine exhaust outlet passage and a compressor driven by the turbine impeller for compressing air admitted to the engine air inlet passage, an exhaust gas recirculation (EGR) system arranged to recirculate exhaust gas from the engine exhaust outlet passage to the engine air Inlet passage, and an exhaust gas bypass passage arranged to divert exhaust gas that would otherwise reach the turbine impeller, wherein the engine further comprises a control valve with a valve inlet and three valve outlets, the valve inlet arranged to receive exhaust gas from the engine exhaust outlet passage, a first one of the three valve outlets providing exhaust gas to the EGR system for recirculation to the engine air inlet passage, a second one of the three valve outlets providing exhaust gas to the exhaust gas bypass passage and a third one of the three valve outlets providing exhaust gas to the turbine impeller.

13. The internal combustion engine as claimed in claim 12 , in which the control valve is configured to control the relative proportions of exhaust gas supplied to the EGR system, the exhaust gas bypass passage and the turbine impeller.

14. The internal combustion engine as claimed in claim 12 , further comprising an intercooler for cooling compressed air and an EGR cooler for cooling recirculated exhaust gas.