Presentation script for The RICT a new sort of engine

Slide No.

1. Introduction. Explain how the engine came to be designed and built with the aid of a SMART award. Explain how Numerics Technology Ltd was set up. Further detail information to the background can be obtained on the numerics web site.

2. I will now introduce the constant volume turbine as compared to normal constant pressure turbines. Earliest turbine developments were c-v types, which were unsuccessful in comparison to c-p turbines due to high losses and low efficiencies. A modern example follows. This has been chosen as it has been the subject of an in depth analysis. More of this later…

3. This is a design by the Australian Defence Scientific Services Aeronautical Laboratory. It has 4 principle components: a single impeller compressor, a c-v combustor assembly, a high-pressure turbine unit and a reduction gearbox.

4. This slide shows the combustor assembly in more detail. It has three compartments and rotates such that each compartment receives a charge of fuel in turn. This is then burnt under constant volume conditions and the exhaust is passed to the HP turbine. Whilst there is effectively an inlet valve system there is no outlet valve as such. A diagram of this system is shown here below and it can be seen that the c-v conditions result from nozzle throttling of the hot exhaust gases causing sufficient backpressure conditions in the combustor.

5. This slide shows the RICT arrangement, which is basically the same, but importantly it has both inlet and outlet rotary valves as part of the design. The inlet valves are on the sides of the rotor assembly. The outlet valves exist as a function of the stator combustion chambers' nozzle outlet and the rotor periphery.

6. The technical conclusions of the analysis paper of this c-v turbine design by Mr Whurr whilst at Cranfield University are given here, together with the corresponding comparison to the RICT engine. The combustor losses refer to heat loss in the Australian design resulting from a very large surface area. This will reduce the pressure level achieved in the combustor. In comparison the RICT combustion chamber is optimised to reduce heat loss. The equivalence conclusion due to HP film cooling does not apply to the RICT, as the turbine design is totally different. The RICT's core cooling is external and not part of the HP gas flows.

7. The scavenging comment does not apply to the RICT design, as there is an output valve present, so a large percentage of the fuel air charge does not pass straight through the combustion chamber. The RICT design is based around and takes advantage of a pulsed flow, rather than taking a normal c-p HP turbine, which is designed for continuous gas flow operation and then subjecting it to a pulsating flow regime.

8. This slide shows the theoretical efficiency differences between c-p and c-v turbines at various operating temperature. This is from a 3rd party report. The assumptions are 85% turbine energy conversion efficiency, 5% combustor losses and no other primary losses for both types of turbine. It can be seen that at a pressure ratio of 16 the c-v turbine is about 16% more efficient. At higher-pressure ratios this efficiency advantage decreases, as can be seen from the trends of the curves.

9. Why build a RICT c-v turbine engine? The power density of a c-v device can be up to 10 times that of conventional c-p turbine. The pressures and more importantly the pressure differentials are up to an order of magnitude higher and the mean operating temperatures are also higher, or can be. This means that an efficient and practical c-v turbine (the RICT) theoretically should be able to provide power levels that approach that of pure rockets. As we have seen earlier the c-v cycle is potentially up to 16% or so more efficient than the equivalent c-p cycle in the mid pressure ratio band. This advantage reduces with higher-pressure ratios as we saw earlier, but both types are in the 40% to 50% practical efficiency band by this point. The small size of a c-v turbine follows from the power density aspect of the engine. The size of a fully developed RICT would be smaller than the figure given here.

10. The pure rotary nature of turbines produces longevity of life and long inter-service periods, other factors remaining equal. By using a two-rotor design, a small faster unit to drive the compressor and a larger slower unit to provide the power output, it is possible to construct an engine with low output speed, which is important for some applications. These include heavy transport and haulage, electricity generation and CHP. This technique is not new and was pioneered in the Rover JET 1 car of the 1950's. The RICT has only a small number of moving parts. The prototype has one common mandrel with five components mounted on it. The manufacturing techniques are standard, normal casting and investment-casting methods are employed and the alloys are not particularly special or expensive. Hence the starting manufacturing costs are that much lower and the production costs decreases substantially with mass production. As the engine design employs higher pressure and to a degree higher temperatures, the mass flow for a given power output is less than a c-p turbine. This means the localised environmental heating effects are reduced. Also the RICT can turn over at lower r.p.m.'s. That is a RICT powered vehicle in a traffic jam would not heat up its surroundings. Also with the two-rotor design this benefit is enhanced.

11. The consequence of having a practical c-v type of engine (the RICT) is that true compression ignition becomes possible. This means that a larger range of fuels and fuel oils may be burnt. As the energy and power density of the RICT can be high, an ecological hydrogen burning engine will still produce a reasonable amount of power in a given engine size. Hydrogen has a lower calorific value than carbon base fuels, as there is no carbon to CO2 conversion in the combustion process, which carries a higher thermal energy value. It does not take much imagination to project that the combination of all these factors, could cause dramatic changes in a variety of areas. Probably transport is one of the most obvious. Electricity generation and CHP are also important areas.

12. This slide shows a longitudinal cross section of the 'as originally built' prototype engine…..Explain……The engine weighs around 180 kgs 'all up'. It is currently being modified as a result of the last series of tests.

13. This slide shows a cross section through the engine core, the rotor stator assembly. The core configuration is horizontally opposed.……Explain…..a fair number of the current modifications are to do with the core.

14. This slide shows a cross section of the combustion chamber in one of the stator units……Explain.

15. I have talked about the RICT c-v turbine being different to a c-p turbine. This slide relates specifically to the expansion process and the detail differences between how the c-p turbine handles expansion of the gas and how the RICT does the job. If a chamber with a rectangular shape has gas expanding in it, theoretically at the first level of analysis the gas will do work. However, the amount of work done in practice is reduced due to effect of turbulence as shown in the diagram on the right. A conventional c-p turbine avoids this problem by using aerodynamically shaped blades in the rotor and stator assemblies. In the RICT core the wall shapes are not aerodynamic shaped in the same way as conventional turbines, but are designed to extract energy from gas vectoring.

16. If we look at the next slide we can see the effect of a high-pressure gas discharging through a slot annulus. The theory for this is covered in several standard works on the topic. At high-pressure differentials there is no turbulence, there may be constrained shock waves when the gas velocity exceeds its own speed of sound, but energy is constrained in the egressing plume. The obvious example of this is a rocket exhaust. These are the conditions that apply to the internal operation of the RICT core. Let me explain further……

17. This slide shows a table of step differential pressures within the rotor stator core of the RICT. There are also corollary tables for pressure and temperature and the work done. This is a typical set of conditions of a RICT under full load operation. The columns of the table are the various stator chambers and are referenced on the top row of the table. The first column is the rotor chamber. The rotor chambers describe diagonals on the table due to rotor rotation. This table shows thirteen stator chambers including the exhaust, and fourteen rotor chambers including the exhaust. The pressure differentials are coloured: red for pressure delta p's greater than 10 bar, yellow for delta p's between 5 to 10 bar, pink for delta p's between 2 to 5 bar and light blue for delta p's below 2 bar.

18. What are the consequences of this table's results? Taking a typical c-p turbine with eight stages of HP turbine expansion at sea level, the differential pressures are nominally 2 bar per stage. In the RICT core there are 195 step expansions. Of these 36% are 2 bar or less. 21% are from 2 to 5 bar. 28% are from 5 to 10 bar and 15% are greater than 10 bar. That is 39% are greater than 5 bar and 62% are greater than 2 bar. The RICT core thus has lower propensity to be affected by turbulence losses than a normal c-p HP turbine.

19. This slide shows the table just described in graphical form. Here though the absolute pressures are plotted, not the differential pressures. There are two plots one for the stator and one for the rotor. The stator has the initial peak of the spark ignition. There are similar tables for compression ignition. The table's x-axis is a step one as using direct volumes, as in a conventional P-V diagram, results in cramping on the left hand side, due to the first small volume chambers. The area under the PV diagram is equated to the output power level of the engine as normal.

20. The RICT prototype is represented in diagrammatic form on this slide together with a form of descriptive nomenclature. This nomenclature was developed as there are numerous configurations that the RICT can take and a short form of description was felt to be useful. There are grammatical rules for this nomenclature. The nomenclature also has a mathematical relationship to the engine profile e.g. dot products for compressor output pressures. The syntax on the left hand side describes the standard layout of the RICT prototype. That on the right hand side describes a RICT with water injection and a form of after burning. The RICT can take large percentage levels of water injection in to the core as the combustion process is separated from the water injection. This can increase power levels and extend the torque curve down to lower revolutions If down stream burners are added in to the oxygen rich cooling air flow so that the turbine assistance unit picks up the additional energy, the power output of the RICT will be increased. The usage of these techniques could more than double the output power of a given sized engine. This has applications in any peak loading application including electricity generation, CHP, aero and VTOL as well as some transport areas.

21. Previously I have made reference to a two-rotor, or two-core format of the RICT. This slide shows such an engine diagrammatically and syntactically. The high-speed compressor set is shown in light blue. The power output unit is shown in yellow. It has no compressor attached.

22. This next slide takes this arrangement a step further. Here an additional exhaust driven turbo-charger has been added to the set up. The problem with impeller-based compressors, which are based on a single shaft, is that later stages need to have higher speeds of rotation to match the flow rates from the earlier stages. This has a corollary to impedance matching in electrical engineering. The problem does not arise in the same form in a standard axial flow bladed compressor. Hence the usage of high-speed turbo chargers, which may be pre or post the shaft compressor stage, or both, can dramatically improve compressor performance. The prototype RICT will include such modifications in the next test series.

23. The core format in the current prototype is that of radial chambers and a radial oscillating gas flow between these chambers occurs. This is illustrated on the left hand side of the slide. On the right hand side an axial format for the core is shown. The axial format has a constant gap, has no centripetally derived back pressure, but in a single stator arrangement requires thrust bearings and the couple is radially dependant. It is much more difficult to manufacture than the radial format requiring a form of laminated construction. This is why, despite drawbacks the radial core format was built.

24. The prototype was built with the concept of dynamic gap control and no sealing between the rotor and stator(s). The theory behind this is shown in this graph which shows leakage for the combustion chamber, a mid sequence chamber and the exhaust chamber. In practice it has not proven to realise these curves due to the gap size at low start speeds. The stator diameter is made marginally larger than the rotor diameter so that although there is minimum clearance at the combustion chamber, the gap increases around the rotor perimeter. The reason for this arrangement is so that centripetal expansion of the rotor and differential expansion between the rotor and stator(s), due to temperature differences, may be taken up.

25. This slide shows the projected power output of the RICT in relation to radial or diametric size. This is a 3.5 power curve. As against a normal square law based curve of a normal area based relationship. If we talk in terms of increasing the axial length of the engine in the same proportion, the respective curves are 4.5 power and cubic respectively. At large engine sizes the engine is unlikely to follow the full power curve due to gas speeds and time needed to fill the larger chambers. Similarly the efficiency is likely to drop off………………Intro slide next.

26. This is a picture of the central part of the rotor. It is made from a high tensile SO2 resistant stainless steel with good creep properties and was cast using investment-casting techniques. The rotor is faced off with two rotor end plates of the same material, which also contain the inlet transfer valve system. The expansion chambers, which connect to the rotor periphery and the cooling 'ventricles', which run axially, can be clearly seen.

27. This slide shows a side view of the engine with the primary parts offered up. Going from right to left we have the two-stage compressor. Next is the toroidal intercooler. Then there is the cooling fan assembly. The rotor can be seen in the middle of the picture. The rotor end plates can be seen on either side of the rotor. The induction transfer ports can be seen in each of the two end plates and are facing us. After the rotor there is the air ducting, which feeds the assistance turbine. The cowling for this is the next component.

28. This slide shows a close up of the engine core. The stator surrounding the rotor can be clearly seen. Its position is ignition and the area exposed through the exhaust port is advance before top dead centre equivalent. The rotor perimeter can also be seen. The hole is the spark plug hole. One of the sensor leads can be shown, which is a high temperature resistance wire. This attaches to the sensor, which is the white area.

29. The engine assembly can be seen here with the various covers in place. Induction air enters on the right hand side and the exhaust is on the left hand side. Various valve assemblies between the compressor output and the intercooler can also be seen in the picture. The four threaded studding rods, which serve as the engine component positioning and mounting system can also be seen.

30. This is a rear view of the engine giving a better view of one of the exhaust outlet. This arrangement is being changed in the prototype re-working currently being undertaken. The back engine frame and bearings can be seen in this view.

31. The model (my daughter) in this slide is touching the engine and is slightly in front and to one side of it, so its size can be fully appreciated.

32. The engine is shown in its mounting frame together with the 3 horsepower soft start motor system. Other points of interest are the engine protection unit or EPU at the top right. The racing standard engine control unit at the bottom right which is the gold coloured unit. This is proven to operate at least to 18,000 rpm on two stroke units. It is fully configurable for two, four stroke cycles and rotary units. It can support one to four plugs and ignition coils and up to eight injectors. The frame and motor at the top left is the servo control system for the stator positioning and uses bang-bang control. In the middle left is one of the two injector plenum boxes. One of the two spark coils can be seen in front of this.

33. This photograph shows the engine during tests conducted up to the end of August this year. A protective sarcophagus surrounds the engine. This unit is made from heavy mahogany roof timbers with thick chip boarding on the inside and outside faces. The void in between is filled with removable sand bags. The whole unit is mounted on heavy castors so that it can be wheeled back from the engine. The sarcophagus weighs around 350 kgs. As a result of the testing we found that various engine modifications were needed. These are currently under way………………………..Intro slide next.

34. In this slide a domestic CHP application is analysed for engines of twenty and forty percent efficiency. Many domestic CHP units currently being developed use Stirling engines, which have low efficiencies even with recuperation. The top table is for forty percent engine efficiency, the bottom twenty. Both tables assume 90% alternator efficiency. The horizontal x-axis of the table is the heating demand in kilowatts. The vertical y-axis is the electrical demand also in kilowatts. The figures in each cell of the table are the balance of heating demand needed. At no electrical power demand as the heating demand increase the balance demand increases by the same amount and the figures are negative indicating that another source i.e. an external burner would have to meet the demand. As boilers, particularly condensing types, may be made very efficient this is not an issue hence the light green blue colour for the background. As electrical demand is increased the prime mover produces heat, which is used for realising the heating demand. As the heat is produced according to the engine efficiency a balance will be struck between the heat demand and that produced by the engine. It can be seen that at 2 KW electrical demand on the 20% table and 5 KW heating demand the engine produces 6.1 KW of excess heat that would be dumped up the flue. This is why the cell is coloured light pink i.e. bad. The only way round this is to import the electrical energy from the mains. The same balance logic is applied to the full matrix of cells and the proportion of light green blue (good) to light pink (bad) can be seen by inspection for the twenty 0ercent engine. If we look at the top table which is a forty percent engine, one can see that the proportion of green is noticeably more not unsurprisingly. The 'good' as it were to bad is about 50 50, whilst in the lower table it is about 25 to 75. Thus we have a simple figure of measure of the effect of engine performance in a domestic CHP environment. The boxes on both tables represent the typical boundaries of electrical and heating demand in small, medium and large domestic properties.

35. The next slide shows the same information as the table in graphical format. The balance energy demand (the cell contents) is plotted on the vertical y-axis. The x-axis is the heat demand. The electrical demand is the third variable. The plot is for the 40% engine example. We have in effect a plot of iso-electrical demand lines. Above the x-axis or excess energy balance is 'bad' as the engine is producing too much heat to that needed, or energy has to be imported. Below the x-axis is 'good' as the engine produces too little heat which can be met by the efficient burner / boiler system.

36. Here we have a comparison between a car and a VTOL vehicle for a journey over 200 miles or 320 kilometres. The y-axis is in units of one hundred horsepower minutes. That is a power output of a hundred horsepower over one minute. The x-axis is in kilometres per hour. The car's curve starts at the origin. The VTOL curve starts at an intercept point. This intercept is the energy required to take off and land vertically at each end of the journey. So if a moderately sized VTOL craft has a power output of 1,000 BHP or 750 KW and takes 30 seconds each time to take of and land, which is quite possible, it will consume ten HHPM's, I.e. the intercept. For a car travelling at one hundred miles per hour or 160 KPH, the VTOL craft can travel at 300 KPH or 190 MPH for the same energy consumption even allowing for take off and landing. The same energy points are also 250 KPH for a car and nearly 500 KPH for a VTOL craft.

37. This graph shows the amount of energy consumed over a 200 mile journey as a function of speed. From an energy standpoint the longest journey time is the best not surprisingly as the rate of energy expenditure is dependant on the speed of travel. If time were the overriding factor we would travel as fast as we could and damn the energy used. It is fairly obvious that the correct trade off is somewhere near the knee of the curve. I.e. around fifty minutes journey time and about 350 KPH or around 220 MPH. That is we would travel at 3.5 times the average long distance motorway speed of 60 MPH or 100 KPH and nearly quarter our journey times.

38. What are the consequences of this? It means that the average commuter on a clear motorway run now doing a 30 minute journey of 30 miles could travel 110 miles. A long distance commuter now travelling 60 miles would be able to travel 220 miles. London urban commuting by VTOL could extend from beyond Plymouth in the west to Leeds/ Harrogate in the North, or from Amsterdam or Paris on the continent, all at the same fuel cost. The eco-sociological consequences, or military possibilities of this design do not require elaborating. The visualisation of this can be seen on the slide, which is a map of the UK. Centred on London are the two 'commuting circles'. Also, the energy consumed by the VTOL craft, even allowing for extended take-off and landing energy, is about the same as that consumed by the car traveller. This is the consequence of and in light of the very latest developments beyond the scope of this presentation, but which will become much clearer to all in the future.

39. The next graph just makes this point in a different way. The red line is the car's energy cost, the mauve line the VTOL energy cost at different speeds.

40. For those who wish to see the photographs again you may see them on the Numerics web site. You may also sign up for e-mail updating on the site. I have provided some castings of the core for perusal at the front here. There are also some more detail photographs of the engine. I hope this presentation has been enlightening for you if a little mind stretching at times.