Split cycle engine control

1. A split cycle internal combustion engine comprising:

a compression cylinder accommodating a compression piston;

a combustion cylinder accommodating a combustion piston;

a recuperator arranged to exchange heat between exhaust fluid from the combustion cylinder and working fluid being supplied from the compression cylinder to the combustion cylinder via a crossover passage; and

a controller configured to control operation of the engine based on an indication of a temperature of at least one of (i) a material of the recuperator and (ii) the working fluid in the crossover passage;

wherein controlling operation of the engine based on the indication of the temperature comprises: in the event that the indicated temperature exceeds an upper threshold value, controlling operation of the engine to reduce a temperature of the recuperator to reduce an amount of heat-induced damage inflicted on the recuperator.

2. The engine of claim 1 , wherein controlling operation of the engine based on the indication of the temperature of the material of the recuperator comprises: in the event that the indicated temperature exceeds an upper threshold value, controlling operation of the engine to reduce the temperature of the material of the recuperator.

3. The engine of claim 2 , wherein the upper threshold value is selected based on a temperature associated with material damage to the material of the recuperator.

4. The engine of claim 1 , wherein controlling operation of the engine based on the indication of the temperature of the material in the recuperator comprises: in the event that the indicated temperature is below a lower threshold value, controlling operation of the engine to increase the temperature of the material of the recuperator.

5. The engine of claim 1 , wherein the recuperator comprises: (i) a first passage for fluid travelling from the compression cylinder to the combustion cylinder, and (ii) a second passage for exhaust fluid travelling from an exhaust of the combustion cylinder.

6. The engine of claim 1 , wherein the engine comprises a turbine arranged to be driven by exhaust fluid flowing from the combustion cylinder to the recuperator; and

wherein the controller is configured to control operation of the engine based on the indicated temperature by controlling operation of the turbine to regulate a temperature of the exhaust fluid from the combustion cylinder.

7. The engine of claim 6 , wherein the engine comprises a turbine bypass passage arranged to enable at least some of the exhaust fluid from the combustion cylinder to flow to the recuperator without driving the turbine.

8. The engine of claim 7 , wherein the controller is configured to control operation of the engine based on the indicated temperature by controlling use of the turbine bypass passage.

9. The engine of claim 1 , wherein the turbine is coupled to a compressor arranged for compressing inlet fluid to be supplied to the compression cylinder.

10. The engine of claim 1 , wherein the engine comprises a recuperator bypass passage arranged to enable at least some fluid to avoid flowing through the recuperator.

11. The engine of claim 10 , wherein the controller is configured to control operation of the engine based on the indicated temperature by controlling use of the recuperator bypass passage.

12. The engine of claim 1 , wherein the controller is configured to control operation of the engine based on the indicated temperature by controlling at least one of: (i) opening and closing times for an inlet and/or exhaust valve of the combustion cylinder, and (ii) a timing of supplying of fuel into the combustion cylinder.

13. The engine of claim 1 , wherein the engine comprises an intercooler for cooling and/or compressing inlet fluid to be supplied to the compression cylinder.

14. The engine of claim 13 , wherein the engine comprises a fluid passageway configured to enable liquid obtained from the intercooler to be supplied to the compression cylinder as a coolant.

15. The engine of claim 1 , wherein the controller is configured to control operation of the engine based on the indicated temperature by controlling operation of at least one of:

(i) a compressor for compressing inlet fluid to be supplied to the compression cylinder;

(ii) an intercooler for cooling inlet fluid to be supplied to the compression cylinder;

(iii) a coolant system arranged to regulate a temperature of the working fluid supplied to the combustion cylinder;

(iv) an inlet valve for the combustion cylinder;

(v) an exhaust valve for the combustion cylinder;

(vi) fuel injection timing for the combustion cylinder;

(vii) a turbine arranged to be driven by exhaust fluid flowing from the combustion cylinder to the recuperator;

(viii) a turbine bypass passage;

(ix) a recuperator bypass passage; and

(x) an inlet port and/or an outlet port of the compression cylinder.

16. A method of controlling a split cycle internal combustion engine comprising: (i) a compression cylinder accommodating a compression piston, (ii) a combustion cylinder accommodating a combustion piston, and (iii) a recuperator arranged to exchange heat between exhaust fluid from the combustion cylinder and working fluid being supplied from the compression cylinder to the combustion cylinder, the method comprising:

obtaining an indication of a temperature of a material of the recuperator; and

controlling operation of the engine to reduce a temperature of the recuperator to reduce an amount of heat-induced damage inflicted on the recuperator in the event that the indicated temperature exceeds an upper threshold value.

17. A non-transitory computer program product stored in at least one memory and executable by at least one processor to perform the method of claim 16 .

18. A split cycle internal combustion engine comprising:

a compression cylinder accommodating a compression piston;

a combustion cylinder accommodating a combustion piston and having an exhaust valve for exhausting exhaust fluid from the combustion cylinder;

a recuperator arranged to exchange heat between the exhaust fluid from the combustion cylinder and working fluid being supplied from the compression cylinder to the combustion cylinder; and

a controller configured to control operation of the exhaust valve based on an indication of at least one of: (i) a temperature associated with the recuperator, and (ii) a temperature associated with the combustion cylinder,

wherein controlling operation of the exhaust based on the indication of the temperature comprises: in the event that the indicated temperature exceeds an upper threshold value, controlling operation of the exhaust valve to reduce a temperature of the recuperator to reduce an amount of heat-induced damage inflicted on the recuperator.

19. The engine of claim 18 , wherein controlling operation of the exhaust valve based on the indicated temperature comprises: in the event that the indicated temperature is below a minimum threshold value, controlling operation of the exhaust valve to open at a time in the cycle which is earlier than an opening time of the exhaust valve in the event that the indicated temperature is above the minimum threshold value.

20. The engine of claim 19 , wherein the combustion cylinder has an inlet valve for controlling flow of working fluid into the combustion cylinder; and

wherein, in the event that the controller controls the exhaust valve to open at an earlier time, the controller is configured to also control operation of the inlet valve to open at a time in the cycle which is earlier than an opening time of the inlet valve in the event that the indicated temperature is below the minimum threshold value.